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Neil Jones
01-16-2009, 12:35 AM
Are there any books or videos that teach you how to use a rotary table for advanced contouring?

Circlip
01-16-2009, 09:24 AM
If you're reffering to using it to blend radii on different centres you need an X-Y table mounted on top of the rotary table. Otherwise it means re-centreing for each arc centre (Substitue centER if in the US of)

Regards Ian.

PS Just remembered, easy way is CNC.

Neil Jones
01-16-2009, 02:54 PM
I'm reffering to mounting a rotary table on a knee mill. I need to be able to cut complex profiles without using a CNC. Before CNC I'm sure this was done with a rotary table mounted on a knee mill.

BadDog
01-16-2009, 03:16 PM
Some can be done with a top slide rotary table, but generally not with a standard rotary table, at least not without some painful setup efforts. Other options include accessories like my my Volstro rotary head attachment. I've managed to do some rather interesting stuff with it that I don't think could have been done (easily) otherwise, though it's still fiddly and requires a fairly light touch. There is also the REAL rotary heads like the K&T, and the "Cherying Heads", universal tables, coupled drives, and other various accessories. The rotary table can do a lot of useful work, but in typical/basic form does not lend itself to "advanced contouring".

For most HSMs with only "aesthetic" requirements in this area, I think the main course is to do the layout and then cut to the line (perhaps using a rotary table to align with a convenient axis), and then file for final contour. In fact, file work was an important part of die and mold making "back in the day" (at least when I worked as a draftsman on extrusion die tooling), probably still is...

Circlip
01-16-2009, 03:45 PM
Sorry Neil, I assumed you'd already mounted the rotary table on the B/P first. OK, from there you THEN mount a co-ordinate (X-Y) table centrally ON TOP of the rotary table.

Clamp the rotary table centrally L to R and F to B on the topslide, and move the slides so that the R/T is centred under the spindle.

Clamp the X-Y table centrally on the rotary table.

By clamping anything to the top of the X-Y table and centreing any hole position under the spindle using the X-Y slides, you can machine blend arcs by rotating the R/T handle.

If you only want to drill holes at pitch centres, you move the topslide and crossslide.

Regards Ian.

Neil Jones
01-16-2009, 04:27 PM
Some can be done with a top slide rotary table, but generally not with a standard rotary table, at least not without some painful setup efforts. Other options include accessories like my my Volstro rotary head attachment. I've managed to do some rather interesting stuff with it that I don't think could have been done (easily) otherwise, though it's still fiddly and requires a fairly light touch. There is also the REAL rotary heads like the K&T, and the "Cherying Heads", universal tables, coupled drives, and other various accessories. The rotary table can do a lot of useful work, but in typical/basic form does not lend itself to "advanced contouring".


Is there a book or video that shows how to mill complex profiles with a top slide rotary table or even with a Volstro rotary head? I imagine that one would draw a picture of the contour with numbers to position to written in ahead of time to mill to?

Neil Jones
01-16-2009, 04:50 PM
Ian, are you aware of any book or video that teaches how to mill profile/contours with the type of set up you described?

BadDog
01-16-2009, 06:01 PM
I know of no book or video, but would love to see one. I've generally sussed it out on my own for the most part. I've got a Volstro manual with what amounts to a "teaser" in a handful of very basic suggestions. The sales brochure is actually more enlightening in that it shows some interesting things that can theoretically be made with it, and then I kinda reverse engineered/figured from that.

I've also got a "light" milling table that I can theoretically mount on my 12" Troyke V/H, but that beast is so heavy that I'm reluctant to fool with it for what is often a few simple cuts. So if it's small enough, I just mount the Volstro (usually sufficient). If not, I make do with multiple setups and cuts, perhaps followed by a file and such...

NickH
01-16-2009, 06:50 PM
How about defining what you are trying to do rather than asking if an undefined action can be achieved with an undefined setup.
Better chance of tapping other's experience and ideas if you give a description of what you are trying to achieve,
Regards,
Nick

Neil Jones
01-16-2009, 07:25 PM
NickH, I wish to mill complex contours that have angles and radii without having to resort to using a file and without using a cam program and a cnc machine. I'm looking for a book, video or online help guide that shows the best way to do this using examples. If you have anything specific to add on where I can find this information I'd appreciate it.

rbregn
01-16-2009, 09:12 PM
If you have a rotary table with a x-y table on top of it, it is relatively easy. With out an x-y table on top, it can be done, but I would take the time to do it. To much work to be worth it, unless someone was willing to pay me shop rate and not complaining about it!:D

oldtiffie
01-16-2009, 09:29 PM
Any chance of a pic or two to show just what this "contour" application is - or just enough to let me see it at least - as I am not at all sure what it is.

Perhaps I know it by another name - or perhaps not.

LES A W HARRIS
01-17-2009, 12:38 AM
NickH, I wish to mill complex contours that have angles and radii without having to resort to using a file and without using a cam program and a cnc machine. I'm looking for a book, video or online help guide that shows the best way to do this using examples. If you have anything specific to add on where I can find this information I'd appreciate it.

This kind of stuff?

Yuasa xy Rotary Table setups.
http://i37.photobucket.com/albums/e97/CURVIC9/NILLWORK/LAWH0205.jpg

http://i37.photobucket.com/albums/e97/CURVIC9/NILLWORK/PANA0435.jpg


http://i37.photobucket.com/albums/e97/CURVIC9/NILLWORK/LAWH0209.jpg

Here's the prints, this is the material, have at it!

Never saw a book on it, you have the machine X-Y, the rotary's x-y, and the rotary's graduated rotation. Center up the rotary, it's slides, cutter diameter, external, internal radii, angular cuts, if all centers can be set within range of slides, how are you going to hold the part?

As posted above the Volstro head can do some wonderful work also.

Cheers,

Neil Jones
01-17-2009, 12:54 AM
Yup. That kind of stuff.

I found this but it's too basic.

http://rick.sparber.org/rtcs.pdf

What I'd like to see are some hands on projects that make use of a rotary table and cross slide done by someone very experienced with using a rotary table and cross slide who likes to teach. I remember a long time ago in trade school that those hands on projects really taught us machining skills. I don't think many machinists have great rotary table and cross slide skills because of CNC and CAM. Based on this .pdf (itís very recent) I think there are quite a few of us who have an interest in building skills in this area.

BadDog
01-17-2009, 01:50 AM
If I could find one the size of that Yuasa for decent money I would own it. I found a 15" Troyke with top slide, and it was pretty cheap compared to what they bring, but just too forking big. About 300+ lbs...

John Stevenson
01-17-2009, 06:07 AM
Draw your profile out on graph paper.
Mark in all the way points [ where the profile changes ] at X and Y co-ordinates and you will see a pattern on how this is laid out.

Basically it's writing G Code line by line but without the CNC.

When we run training classes they have to be able to do simple parts before they even get to see a machine.

The hard part is to be able to transfer the rotab zero to the next arc centre point then update you co-ordinates from this point but you need the original co-ordinates to either add or subtract to.

.

oldtiffie
01-17-2009, 06:58 AM
I can see what John Stevenson is getting at as its not that much different from drawing it at different "flat" "X"-"Y" planes with each at a different elevation "Z" - all using relative and absolute co-ordinates and calculating/allowing for tool off-sets.

It should be easy in CAD.

OK - so much for the theory and the computer.

If the set-up is anything like Les Harris', the set-up will required a very large 3-dimensional envelope to get under the spindle and not foul/impact the mill column or vertical dove-tail (knee mill).

Is there any reason why the job can't be fabricated and/or built up from pre-cut (laser? plasma?) material and welded so as to minimise the cutting time and loads?

Why not have it built using Rapid Prototype?

It really does seem to shout (for?) "CNC!!!!!"

John Stevenson
01-17-2009, 07:21 AM
I can see what John Stevenson is getting at as its not that much different from drawing it at different "flat" "X"-"Y" planes with each at a different elevation "Z" - all using relative and absolute co-ordinates and calculating/allowing for tool off-sets.

Ignore the Z you don't draw in 3D when using a normal engineering print.




Is there any reason why the job can't be fabricated and/or built up from pre-cut (laser? plasma?) material and welded so as to minimise the cutting time and loads?

Probably because the OP never asked for that, more an understanding on how to do this at home.


Why not have it built using Rapid Prototype?

Good question, other than You tube has anyone here in a home shop or small shop environment got access to rapid prototyping easily sourced at at hobby shop pricing ?
Rapid prototyping is also usually done in wax, anything more comes very expensive and probably still wont accept normal useage but be more suitable as a pattern or master.



It really does seem to shout (for?) "CNC!!!!!"

Yes but like many on this board who don't have CNC the OP did say without CAM or CNC.

Neil Jones
01-17-2009, 07:55 AM
"The hard part is to be able to transfer the rotab zero to the next arc centre point then update you co-ordinates from this point but you need the original co-ordinates to either add or subtract to."

What is a "rotab zero"? Can you post an example part contour showing how this method you describe works. That might be enough to get me going in the right direction. I don't see myself being able to mill part contours without doing all the math and making a map/print ahead of time.

Circlip
01-17-2009, 08:07 AM
Full marks for wanting to learn the "old way" Neil. Sorry I can't point you in the direction of any books or vids to guide you. Les Harris's piccys show and explain exactly what I was trying to describe and certainly were a blast from the past. My own experience in using the setups were over forty years ago machining punches for press tools to manufacture my post name and sadly the only instructions for setting up how to do it was at the elbows of two mentors as I was the Kid in the middle of row of three Bridgeports all permanantly fitted with rotary tables and co-ordinate tables. Just to point out to the old stagers that they can ALLWAYS learn from youf, I won a fiver (£5 in old money when my weakly [NOT a spelling error] wage was £3-7s-3d) from one of them on a positioning error on the setup.

The longest part of the task, as has been intimated, was zeroing and recording all the dial settings, setting and clamping the punch blank on the co-ordinate table true with the spindle and THEN sitting with the component drawing and plotting ALL the machining centres, offsets and arc end points and recording them in a book before even switching the machine on. It was then a case of going through the settings and cutting or drilling dependant on which slide you were bringing into use, and we did make the punches in batches of four.

If yer budget don't go to a reasonable co-ord table, another way would be to mark all the centres on the workpiece with a centre punch and centralise and clamp each one in turn on the rotary table and do all the machining pertinent to that centre, then pickup and re-centralise and clamp the next one. Again, the most important tools are going to be a notepad, pencil and Zeus or calculator and set out the WHOLE of the sequence before hacking any metal.

Hope the ramblings help,

Regards Ian.

( I make no excuse for writing Rotary table in full as the American bastardisation really gets up me nose )

oldtiffie
01-17-2009, 08:08 AM
Originally Posted by oldtiffie
I can see what John Stevenson is getting at as its not that much different from drawing it at different "flat" "X"-"Y" planes with each at a different elevation "Z" - all using relative and absolute co-ordinates and calculating/allowing for tool off-sets.


Ignore the Z you don't draw in 3D when using a normal engineering print.

I could have put that better I suppose. I rather meant a "flat" (2-D) drawing for each change in profile/s with a change in "Z". Different drawings/jobs at each level of "Z".

If it were a set-up like Les Harriss', then "interference" or "fouling" of or by the tool, job or set-up may make it very difficult.

I actually had in mind that each of the seperate 2-D "drawings" could be on sepate layers (in CAD) or sheets of transparent/translucent "graph" paper that are all registered to a common "X-Y" point/s and each can be "switched on or off" (or in the case of paper, inserted or withdrawn - as on a "light table").

My guess is that a physical "model" for "proof of concept" might be a good idea before going too much further.



Is there any reason why the job can't be fabricated and/or built up from pre-cut (laser? plasma?) material and welded so as to minimise the cutting time and loads?


Probably because the OP never asked for that, more an understanding on how to do this at home.

I was meaning to ask/suggest about an option to carving out from a billet.



Why not have it built using Rapid Prototype?


Good question, other than You tube has anyone here in a home shop or small shop environment got access to rapid prototyping easily sourced at at hobby shop pricing ?
Rapid prototyping is also usually done in wax, anything more comes very expensive and probably still wont accept normal useage but be more suitable as a pattern or master.

Too true. I was "just thinking aloud" I guess. But I have seen RPT done pretty quickly - and allegedly not all that expensively - from supplied 3-d models - but 3-D is out too. But I did have casting in mind. I think I recall seeing somewhere that RPT has advanced to using sintering materials and processes as well such that all that needed is minimal if any machining.



It really does seem to shout (for?) "CNC!!!!!"


Yes but like many on this board who don't have CNC the OP did say without CAM or CNC.

Again - true. But perhaps someone may be able to assist or else CNC may well end up being the most viable and/or only option. If that is the case, then ruling out CNC may well bring the whole job to a dead stop.

John Stevenson
01-17-2009, 08:23 AM
Tiffie me old mate, not having a pop at you just trying to get this back on track.

It's getting more obvious than Neil is a complete beginner, no problems with that we all were a 157 years ago, but it also opens up how many are also watching this and don't have a clue.

Ian, has shed a bit of light on it as he's also used a Volstro head.
I have only used one once and that was at college but I can remember how it worked.

At work we didn't have one and had to do it the hard way.

Rotab zero is the centre of the rotary table and for any arc moves you have to know where it's at accurately for any arc moves, not as critical for linear moves.

If no one steps up to the block I'll do a simple two line and two arc demo later tonight as I have other things on at the moment.

Sorry Ian if ROTAB gets up your nose but anything that saves time but gets it across works for me.
When you are born with a long surname you soon find ways to cut things down :D

Circlip
01-17-2009, 08:30 AM
Damn turncoat JoStEoSuPuWa. and whats a Volstro Head ??

Ci

Neil Jones
01-17-2009, 08:40 AM
Ian,

"The longest part of the task, as has been intimated, was zeroing and recording all the dial settings, setting and clamping the punch blank on the co-ordinate table true with the spindle and THEN sitting with the component drawing and plotting ALL the machining centres, offsets and arc end points and recording them in a book before even switching the machine on."

At this point what you wrote above is how I envision myself doing part contours with manual equipment. I know seeing a tutorial on what you wrote above would really, really help me!

"If yer budget don't go to a reasonable co-ord table, another way would be to mark all the centres on the workpiece with a centre punch and centralise and clamp each one in turn on the rotary table and do all the machining pertinent to that centre, then pickup and re-centralise and clamp the next one. Again, the most important tools are going to be a notepad, pencil and Zeus or calculator and set out the WHOLE of the sequence before hacking any metal."

I’d like to try doing it this way a few times. I do have access to both a Volstro head and a rotary table. Not sure if I can get my hands on a rotary table with a built in coordinate table.

"I make no excuse for writing Rotary table in full as the American bastardisation really gets up me nose"

Does “Rotary table in full” mean a rotary table with a built in coordinate table? Also, to make sure I'm not missing anything, is a "Zeus" the same thing as a calculator?

oldtiffie
01-17-2009, 08:45 AM
You are right John.

I could see this leaving its orbit.

I can see another "tiffie apology" is in order here - done!! Jeez - there's a lot of 'em.

Perhaps if a simple/realistic model were made - modeling clay might do - and plonked on a rotab (yeah - me too!!) the problem with making it should soon become obvious. Putting an "X"-"Y" slide on the rotab while seeming to solve a few more problems (which it may) will soon show or create a few more.

The trick here is not to just see it on paper or a computer but to see it on the machine in animated 3-D ("walk-through"?) in your "mind's eye".

This could either be an excellent project or the Machinist's version of the Stations of the Cross - and where that ended up!!!

John Stevenson
01-17-2009, 08:52 AM
Ian,
This is a Volstro head.
http://www.stevenson-engineers.co.uk/files/volstro1.JPG

http://www.stevenson-engineers.co.uk/files/volstro2.JPG

Pictures courtesy of Ebay before they disappear.

The bottom slide is the linear slide and the handwheel above is the rotary movement.
they are power driven from the head of the mill and are similar to a rotary table with X Y table but inverted.

Neil.
"Rotary table in full " is Ian's way for meaning "Rotary table" but longhand not shorthand as in "Rotab"

Zues describes the pocket book of tables much loved by engineers this side of the pond

Here's a link to the pdf of the book, grab it quick before it disapears.

http://forums.lr4x4.com/index.php?showtopic=4463&mode=threaded&pid=46760

.

oldtiffie
01-17-2009, 08:55 AM
..........................................
..........................................

Also, to make sure I'm not missing anything, is a "Zeus" the same thing as a calculator?

Neil,

(the) "Zeus" is a small pocket-sized booklet of Engineering Tables that has been around for-ever. It is readily available pretty well everywhere. It was referred to in a recent "Black Book" thread.

It is similar to - but in my opinion not as good as - the "Black Book" which I posted in the same thread.

Here is the "Black Book" - as said, "Zeus" is similar.
http://i200.photobucket.com/albums/aa294/oldtiffie/EngineersBlackBook1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/EngineersBlackBook2.jpg

Circlip
01-17-2009, 09:00 AM
Sorry Neil, it's just the shortening of the correct term "Rotary Table" to Rotab, (Lazy Yanks)

No, I've never seen a combined/one piece unit, that why I mentioned clamping the co-ordinate table on top of the Rotab ( Oh sh4t)

"Zeus" is an engineers bible, a book of formulae, in TLOTF "The Engineers Black Book" ?

Can't comment on on Volstro head,never seen one.

Can you give a sketch of what you're thinking of machining? with a few dimensions, a lot easier than trying to hypothesize.

Regards Ian.

Circlip
01-17-2009, 09:12 AM
Hades Dentures even the Aussies are shafting us, can't afford a few bob for a Zeus (Probably costs more to download) (Bob,- Shillings-obsolete British coinage)

Ok, back to the plot, I can see how you can offset in one axis on the Volstro, but not the other? It only seems to have one axis offset and the rotary function.

Regards Ian.

abn
01-17-2009, 09:14 AM
Rotary tables also have a precise center hole or taper...you can use this to mount a pin to speed rotary table center location with a matching hole on the part. Works great for radii around bolt holes and such where you have to drill a hole anyway. I'm at work right now and can't access pics or movies so I'm sort of flying blind.

Just as an aside, a lot of past work was also done with radii or forms ground into the tooling. There were/are also various tracer and pantograph attachments. Sort of a weird reference, but still in my head; There's a kid's show called Reading Rainbow, in an episode called Hotel Animal they tour the Matchbox car factory, very short segment but you get to see a manual machinist doing complex contours on a vertical mill. There's a snippet here (which I can't see from work).

http://link17.streamhoster.com/?u=educate&p=%2Fgpn%2F126_123.rm

I just mention it because it may be at your local library, wouldn't go out of my way to get it, but if you are there anyway. Main point of the post was the locating pin tip...as you can see from the article you posted Rotab (Rotory Table abbreviation) work depends on being able to reliably and repeatably locate the rotab center of rotation in relation to the machine spindle. It all just adds up, if you can visualize the article you posted, now visualize it say using a corner rounding end mill, or in aluminum, even a wood router bit to add additional contour. Once you visualize that now put a block under one end of the rotab to tilt it, now you can see contours getting pretty complex. Wish I could help more.

John Stevenson
01-17-2009, 09:15 AM
That PDF of the Zeus book is the older version that has the full BA specs in and not the bastardised later version with only tapping sizes for BA to make room for fine metric.

Been looking for a decent copy of that for ages as mine, you don't read it, you shuffle it.

It's not the full book as it's missing the log trig tables at the back but still handy to have.

.

Neil Jones
01-17-2009, 01:38 PM
One thing that I can't get my head around is how to you figure out how to machine a non-standard radius where the radius is not the size of the end mill?

John Stevenson
01-17-2009, 01:53 PM
The radius of the end mill should never come into it. You choose a size that is less than the minimum radius you have.
If it's equal or larger then this will determines the radius it cuts.

Yes I know equal should read equal but in real world with clearances etc it will cut bigger.

Can you do a sketch of what you want to achieve?

.

Circlip
01-17-2009, 02:05 PM
If you turn the job through 90deg vertically, ie. a plate on a lathe and treppan a hole in the plate, you have moved the cutting tool off centre to the plate, then rotated the plate and cut into it with a fixed cutter and you have cut a disc out and left whatever size bore you need ? OK. replace the lathe tool with a rotating cutter and do the same operation and you still get a bore in the plate at whatever radius you set the cutter.

Consider the rotary table as the chuck that YOU are rotating and if you had a single point cutter in the spindle and fed it down onto the plate, if you've offset the Table you scribe a bigger circle on the plate.

Is this bit clear? NO SARCHASM INTENDED,just trying to get first principles.

Regards Ian.

Neil Jones
01-17-2009, 02:08 PM
I need to find a way to scan in a print. Nothing unique or special about the part. A typical two and one half axis milled part that can be done easily and quickly on any CNC.

Neil Jones
01-17-2009, 02:18 PM
What is not clear is how I would figure out the X,Y positions to cut a non-standard radius with a cad system. Perhaps by drawing the radius (circle) and making it tangent to say two lines and then finding it's center point where I would start milling. I guess I would also have to know the degrees of where the radius stops in order to know when to stop turning the rotary table?

Smokedaddy
01-17-2009, 08:03 PM
Neil,

I screwed my back up this morning so sitting is impossible and typing isn't to much fun. I have the same desire that you do (in this thread). I know the conture below is simple ...

http://www.pbase.com/smokedaddy/image/92948425

... but I too would like to be able to do complex curves like you mentioned. In any case, I wrote a LISP routine in AutoCAD a few years ago that extracts the X and Y coordinates of all intersections then places those coordinates next to the intersections, based on a selected 0,0. I wonder how this would work with a DRO (even though I don't have one, nor know how one operates).

-SD:

NickH
01-17-2009, 08:33 PM
Use a coordinate table large enough to move the center point of each radius on your part on center of the rotary table you've bolted the coordinate table to the top of.

To do the job without the small coordinate table on top you re-center the work on the rotary table for each radius.

Use the mill's main X - Y to position your cutter, you'll want it (about ;-) )the radius of cut minus the radius of the cutter from the center point of the radius you're cutting.
Turn the rotary table for the required radius cut.

John's idea of drawing this on graph paper is ideal, if you draw your part you can calculate or measure with a protracor the number of degrees for each cut.

I think you should have a fiddle just blending one inside radius into an outside radius, it really is easier than it sounds once you do it,
Regards,
Nick

oldtiffie
01-17-2009, 09:16 PM
Neil,

I think I can see the problem.

The radius you draw or require on the job is the path the cutting edges/s of the tool will take to cut it. The centre of the tool is the path the centre of the tool and the milling head spindle axis will take. The path of the centre of the cutter is generally known as the "tool (centre) path" and the cutting face/edge of the tool/cutter is the cutting path. The off-set between these two paths is the "off-set" - ie the radius (half the diameter) of the cutter.

It is really no different to using guides or templates on a wood-working router.

These are a brake drum that I machined on my rotary table:
http://i200.photobucket.com/albums/aa294/oldtiffie/Brake-disc1-1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Brake-disc2-1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Brake-disc3-1.jpg

With this milling cutter "off-set" to suit:
http://i200.photobucket.com/albums/aa294/oldtiffie/TC_end-cutter1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/TC_End-cutter2.jpg

If you are going to fit a rotary table big enough to clamp stuff - "X"-"Y" table etc. and fit in your cutters as well you are going to need a pretty big good mill and a pretty big rotary table.

Here is my common garden-variety HF-45 vertical mill with both a 6" and an 8" rotary table on it.
http://i200.photobucket.com/albums/aa294/oldtiffie/HF45-5.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/HF45-1.jpg

And here is a pretty small and cheap but surprisingly accurate "X-Y" table on my lathe that I put up just for the pic. for a post some time ago. I have a larger better one too but all this adds up and crams the over-head space.
http://i200.photobucket.com/albums/aa294/oldtiffie/AirSmith06.jpg

The question about cutting a 1" hole or 1/2" radius with a 1" cutter might seem simple enough - but it isn't.

If "drilling/boring" the cutter tends to "wander off". Cutting a 1/2" radius in conjunction with cutting one or more tangential faces by just cutting one face and until the cutter is tangent to the other or another face and then just starting the new face from the tangent point is another thing that seems as it wil work - but most time it doesn't as the large cutting arc on the cutter will cause it to "rub" and perhaps "burn"as well and probably to "chatter" as well. All of these can work-harden the job and not do the cutter any good at all. What is often done is to drill/bore the 1" hole and cut the tangential faces with a smaller (say 7/8" or 1/2") cutter and all will be well. CNC will cut both tangential, faces and the (1/2" radius) arc all at once with a say 1/2" cutter with its tool-path off-set by half the cutter diameter from the required faces. Just as you would on a router.

A rotary table - with the job clamped to it - stood vertically on a flat surface as well as a digital height guage - or a surface guage or scribing block and a good ruler depending upon your circumstances - is an excellent way of marking angles out on a job if you don't have a good protractor. I use either method often. If high accuracy is not needed, I just mark it out and centre-punch it and set the job up on the mill table or the rotary table (scribed lines can be set up to within a couple of thou very quickly and accurately). I would drill/bore all holes with the job on the mill or rotary table and do all of the straight and/or tangential lines as well. I would do the "external" curves/arcs/radii on the rotary table as it is easier to get the radius/curve to "blend" smoothly with the lines than it is to get the lines to blend with the curve/s.

I would just about bet that there will be some "hand-finishing" even if only a small amount.

I'd like to see a pic or a scan of something similar to what you intend to do.

My approach is always to use the simplest or easiest methods and tools etc. first and work my way "up" only until I have reached the required level. Too many are inclined to (do??) use the "top down" approach" and tend toward the most difficult or most "high tech" with the most expensive tooling first. I have most or much of the expensive "hi-tech" stuff and most of it is rarely used - until or unless it really needs to be - and that suits me.

Most big jobs - any job - is only a series of smaller and/or easier jobs. It just takes a bit of planning and fore-thought.

Its just like eating an elephant - a big job that takes time, patience and planning - as well as lots of small(er) bites - and of course, an appetite for the job!!!.

Hasten slowly.

dp
01-17-2009, 09:35 PM
Sorry Neil, it's just the shortening of the correct term "Rotary Table" to Rotab, (Lazy Yanks)

The correct term would be "lazy Yankees". (Sodding Brits!) :)

D&R

oldtiffie
01-17-2009, 09:53 PM
Yep they are sodding buggers. And not just the Brits!!

http://en.wikipedia.org/wiki/Sod_(Vulgarity)

I am old (by any measure) and am of Irish extraction - both sides - Mum from "Prod", dad from "Mick" from "the old Sod" (as it is sometimes referred to).

Hmmmm

oldtiffie
01-17-2009, 11:02 PM
I suggest that this current thread is highly relevant here and well worth a good read:
http://bbs.homeshopmachinist.net/showthread.php?t=32718

dp
01-17-2009, 11:48 PM
I spent some time between thread hijackings to browse the internet to find any literature on using rotabs for carving complex shapes but found nothing. I did come up with a method to try some experiments without much investment.

Put a print of your object on a properly sized flat plate. Affix that plate to the rotab in some fashion, perhaps using double backed tape, and get the drawing aligned as you would the work. Put a sharpie in a collet or drill chuck in the mill, and start drawing the cutter path on the paper using the rotab controls. The mill remains turned off, of course.

I've used this method to do step cuts in a complex shape as a practice step and it works pretty well. Cheap, too.

oldtiffie
01-18-2009, 12:19 AM
Good start and good thinking Dennis.

Rich Carlstedt used a similar principle in his manufacture of his engine - brilliant work.

What he did - as I recall - was to have a drawing separate to the mill and had a pointer/stylus attached to the mill quill. He just "traced" the drawing by using his mill "X" - "Y' slides and the mill "followed" the stylus. I can't remember if he use a rotary table. Brilliant hand co-ordination work. He was "flying blind" a lot of the time as the cutter was hidden in the job!!

Perhaps someone can post the link to that marvelous thread!!!

If your drawing had the cutter "off-sets" as off-set lines from the required finished face/s you could trace that with it set up for the cutter centre to follow the off-set line/s. You can use your mill as a router would and use progressively larger cutters to control depth of cut while alway following the same off-set lines/s.

"Holes" (arcs and drilled or bored etc.) would need "zero off-set" but can be done relatively easily. I would do all I could initially in "X" and "Y" with the job packed up from and bolted to the mill table.

Any lines other than "X"-Y" can be done by setting up the drawing on one rotary table and the job on another. Align "X" or "Y" lines to zero on both the both rotary tables. Rotate the "drawing" to align with the mill "X" and/or "Y". Rotate the "work" rotab the same amount, pick up the "off-set" line/s and away you go.

External tangential arcs can be done without "tracing" if needs be as the cutter can be centred over the rotab centre and off-set to suit the tool path off-set. Getting the "blended" arc tangential to the lines is pretty accurate and easy if done by "feel" and "eye".

The limiting factors here may well be (not necessarily limited to): machine/job/cutter "fouling" or "crashing"; rigidity of the set-up; limit of over-head ("Z").

Cutting from a bare "billet" can be a PITA. Some pre-forming/cutting/separate (to be assembled later) parts and perhaps some welding may be needed.

Not all faces may need to be machined or machined to high levels of accuracy. Some may just aesthetic and some may just for "clearance" etc.

These are interesting jobs.

may you live in interesting (good) times!!

dp
01-18-2009, 12:33 AM
There are interesting differences when the rotating face is on the x-y table vs having the x-y table on the rotating face. There were pictures posted of both configurations.

Circlip
01-18-2009, 05:14 AM
Seems like all of us that have used the set up are all singing from the same song sheet Neil. A couple of points to add on NickH's post, subtract cutter rad for INTERNAL arcs, but ADD cutter rad for EXTERNAL arcs. Other point is that you can calculate precise blend points between merging arcs with tables and calc. sin. cos and tan. Looking back at Les Harris's post,the Yuasa unit he shows is a dedicated unit, yer can't separate the rotary fromthe co-ord.

Sorry dp, the sodin bugg*rin lazy Brit has had the AUDACITY to shorten a term :p


Regards Ian.

Neil Jones
01-18-2009, 01:18 PM
Got some help on the phone yesterday from a retired manual machinist/moldmaker who still uses his Yuasa rotary table with built-in cross slide on his knee mill at his home. I hope I have most of what he said correct:

You do your milling with the knee mills X,Y table.

You do your positioning for the center point of each inside or outside radius with the rotary tables built-in cross slide.

Arcs are obviously milled using the rotary tables crank

A riser block on the knee mill is necessary for a good deal of work.

Leave extra material on the piece and mill a profile to a very shallow depth to see where you will have blending problems and if you have made any mistakes in calculations.

All of this can be done without a cross slide if you reposition your work but this is something I'd rather not do.

He's never used a Volstro head so we did not discuss its use. Apparently the Volstro head works quite differently because as has been mentioned it's only got one slide. The only advantage to using a Volstro head that I can envision is a quicker setup. I could be wrong on this.

Neil Jones
01-18-2009, 01:23 PM
Nick,

"Use a coordinate table large enough to move the center point of each radius on your part on center of the rotary table you've bolted the coordinate table to the top of."

I believe this is the main issue I didn't understand.

I still don't understand how a Volstro head works.

John Stevenson
01-18-2009, 01:31 PM
Simple mis understanding.

YOU are talking about using a rotary table on the bed of a knee mill.

OTHERS are talking about using a rotary table that has it's own X and Y slide built in.

In your case you machine using the XY table of the knee mill and then the first arc using the rotary table.
THEN you have to move your work so the centre of the second arc is over the centre of the rotary table [ hence rotab zero ] and carry on.

In the other cases you machine using the XY table of the knee mill and then the first arc using the rotary table.
Then you use the rotabs own x y slides to position the second arc under the rotab zero and carry on.

In short if you have what is known as a co-ordinate rotary table [ one with it's own slides ] you can do work with multiple arc centres.

If you only have a rotary table you have to position your arc centre after ever arc cut.

Clear ?

Forget the Volstro head it's confusing you, sort this problem out first.


.

Circlip
01-18-2009, 01:44 PM
The explanations are in all the posts John, it's just that we haven't got a big enough memory stick. Yuasa were busy trying to rebuild their irradiated factory units over forty years ago, so had the advantage that they could "Design" what had been a two part tooling system and invent (Copy) a better mousetrap.

Regards Ian

John Stevenson
01-18-2009, 01:52 PM
The explanations are in all the posts John, it's just that we haven't got a big enough memory stick.

Regards Ian

I know that and you do, but Neil is struggling to see the light.

Not knocking him it sometimes happens, I have problems understanding women, quantum physics ? no problem, women ? a problem

and no Tiffie we don't want 175386539975 [ approx ] tiffipedia links .

Circlip
01-18-2009, 01:55 PM
Spoilsport

BadDog
01-18-2009, 02:13 PM
If I'm not mistaken, Troyke built coord rotabs before Yuasa, not sure who made the first.

And yes, the only benefit of a coord rotab is the ability to use the top slide (coord element) to move the parts center of rotation by moving the part over the rotary element. Then the machines table is used to do transitions as usual (linear cuts or set radius). Simple as that, there is nothing else to think about. The only thing of any difficulty at all is figuring the actual numeric values of the movements on all 5 axis to yield the desired results. So, the limitation here is that the max aggregate distance across center points is constrained by the work envelope of the rotabs coord table. But, the work piece itself, including cut radius and linear traversals is constrained only by setup and the mill's table work envelope.

This is also why a cross slide on the bottom of the rotary element will not work for this purpose (see Palmgren thread). Again, the key is the ability to move the rotation center on the part.

And yes, the Volstro (or more generally, a rotary head) is completely different in operation, so don't try to mix them in, or it will just confuse things. However, while the mechanism is very different (actually flipped on it's head), the end result is the same. With a rotary head, you use the main table to move the rotational center on the part. You then change radius or make linear transitions using the single cross slide of the head. The limitation here is that you can only handle parts where the radius and linear transitions are within the rotary head cross slide range. BUT, you can handle parts (for which that is true) with much larger max aggregate distance between centers based on the mill's table envelope. It also tends to eat a lot less of your work z-space.

So, same basic results, just different implementations and effect on your work envelope. If you're making case latches, ratchet pawls, gun triggers, and all such typical HSM uses, then either of these will do. I've got the Volstro, but no coord rotab. I would like to have both "just in case", but really, it would be largely redundant. The coord rotab would allow me that change in envelope (might make a difference some day), but more importantly, it is more rigid and would allow slightly more aggressive cuts. But then, I'm not in that big a hurry...

derekm
01-18-2009, 02:46 PM
Yep they are sodding buggers. And not just the Brits!!

http://en.wikipedia.org/wiki/Sod_(Vulgarity)

I am old (by any measure) and am of Irish extraction - both sides - Mum from "Prod", dad from "Mick" from "the old Sod" (as it is sometimes referred to).

Hmmmm

Its not BRIT - its "Citizen of the United Kingdom" especially to Transportees and the Revolting People who cant spell catalogue and centre and colour... :D

Way ot so far as to be a Thread Pirate AARRRRH

Why is JAP racist but BRIT isnt?


I remember causing furor in a U.S. forum long long ago when I mentioned how good I thought a JAPanese bike was ... and when the moderators stepped in and asked I remove it , I decided in the usual BRITish perverse wind up way , to claim that the term BRIT was a racist slur... They took me seriously :D :D That reaction to the wind up made me laugh for ages...

NickH
01-18-2009, 03:08 PM
Does this help?

http://i135.photobucket.com/albums/q158/magicniner/X-Y-OnRtOnMill.jpg

As you can see, a substantial part of the top X-X table can be brought on RT centre.
Use the mill X-Y to position the RT centre for the correct raduis & wind the RT & cut.
Move your next radius centre to the middle of the RT & so on,
Regards,
Nick

I was impressed that this lot would fit under my little benchtop without removing the collet chuck ;-)

dp
01-18-2009, 03:12 PM
In the other cases you machine using the XY table of the knee mill and then the first arc using the rotary table.
Then you use the rotabs own x y slides to position the second arc under the rotab zero and carry on.

To complete my understanding of the geometry - in this last case is the x-y table above or below the rotary table? If above then it will allow you to relocate relative to the rotab center without reclamping the work.

NickH
01-18-2009, 03:16 PM
Once more with feeling?

Does this help?

http://i135.photobucket.com/albums/q158/magicniner/X-Y-OnRtOnMill.jpg

As you can see, a substantial part of the top X-X table can be brought on RT centre.
Use the mill X-Y to position the RT centre for the correct raduis & wind the RT & cut.
Move your next radius centre to the middle of the RT & so on,
Regards,
Nick

I was impressed that this lot would fit under my little benchtop without removing the collet chuck ;-)

dp
01-18-2009, 03:59 PM
Once more with feeling?

We were posting at the same time :) Thanks, Nick. That config looks to be the most versatile. Compare http://bbs.homeshopmachinist.net/showthread.php?t=32718 which is also a nice tool but requires repositioning the work.

Neil Jones
01-18-2009, 05:38 PM
"Simple mis understanding.

YOU are talking about using a rotary table on the bed of a knee mill.

OTHERS are talking about using a rotary table that has it's own X and Y slide built in."

Right, YOU and OTHERS are. MY bad. I now know the difference and how valuable having a built in X and Y slide in a rotary table is!

"In your case you machine using the XY table of the knee mill and then the first arc using the rotary table. THEN you have to move your work so the centre of the second arc is over the centre of the rotary table [ hence rotab zero ] and carry on."

I would think having a built in X and Y slide would save a lot of time and prevent a possible/likely tolerance stack up.

"In the other cases you machine using the XY table of the knee mill and then the first arc using the rotary table. Then you use the rotabs own x y slides to position the second arc under the rotab zero and carry on." In short if you have what is known as a co-ordinate rotary table [ one with it's own slides ] you can do work with multiple arc centres."

Right.

"If you only have a rotary table you have to position your arc centre after ever arc cut.

Clear ?"

If "ever" = every than I AM crystal clear. :)

"Forget the Volstro head it's confusing you, sort this problem out first."

I think this problem is finally sorted out in my mind. My next step might be to buy or borrow a rotary table with a built in X and Y slides. I also might accept the fellow who spent at least an hour on the phone with me yesterday offer to show me how he does it at his house. Regardless of what I do next, I'm pretty confident that I can now sort out the rest.

Ready to try and explain how you use a Volstro head to cut a profile/contour? The reason I ask is it with be very easy to borrow a Volstro head from a local shop who no longer uses it and see if I can mill a profile/contour with it.

John Stevenson
01-18-2009, 05:53 PM
Ready to try and explain how you use a Volstro head to cut a profile/contour? The reason I ask is it with be very easy to borrow a Volstro head from a local shop who no longer uses it and see if I can mill a profile/contour with it.

No I'll leave that to someone who may have used one later than I did and that was for one afternoon 43 years ago.............

.

Neil Jones
01-18-2009, 05:57 PM
"With a rotary head, you use the main table to move the rotational center on the part."

Okay.

"You then change radius or make linear transitions using the single cross slide of the head."

So just one slide can mill linear transitions (lines, angled lines) for both X and Y coordinates?

"The limitation here is that you can only handle parts where the radius and linear transitions are within the rotary head cross slide range."

So it's only for small parts less than the distance of travel of the single slide unless you create multiple part zeros?

oldtiffie
01-18-2009, 06:55 PM
While wanting not (not wanting?) to be the "wet blanket" here, and not-with-standing the requirement of the OP for contouring on a rotary table, it has got a bit further than that (and almost out of hand).

I rather thought or understood that it was required to be done on a vertical of knee mill and a rotary table - without CNC/NC - in a HSM shop. I can stretch that to include an "X"-"Y" table probably on the rotary table and even under it - but not necessarily as an integrated unit.

There is nothing in the OP that I can see that says that the entire job has to be done on a rotary table either. That being the case, there are or may be elements of the job that can be done with the job clamped to the angle plate or the mill table or a fixed or tilting angle plate or in a simple or compound vise.

If that is so, then providing that at least part of the "profiling" is done on a rotary table then the question implicit in the thread title - the original OP - which was and still is:
"How TO Use a Rotary Table For Advanced Contouring?"
is answered and can be in many HSM shops with a vertical mill and a rotary table.

There was nothing to say - in the OP - that the end-result could not be comprised of several separate elements or parts that when assembled (ie "built-up") met - or might meet - the OP criteria.

John Stevenson made some very telling points ("reality checks"?) along the way - the main one, implied if not said - was that providing that if it was dealt with as separate 2-D jobs in succession - that if it could be drawn (CAD or paper), then it could be drawn on the job (aka "marked out"). All that was needed was a reasonably good flat surface, a rotary table (vertical mode), a hammer and centre/prick punch, a digital/vernier height guage (or a scribing block, a surface guage - or a scriber and a good rule(r), and you are pretty well set to go.

If references were needed for accuracy, I'd use edges and/or pre-bored holes or inserted dowels and otherwise just aim to "split" the marking-out lines and centre-punched marks. I can reliably pick and work to a scribed line with in a thou or so - if needed.

My preferred milling/machining is always with the job bolted or clamped to the mill table. Next is a rotary table (if for no reason other than to comply with the OP) followed by a vice (with or without a rotating base - as required).

So far the discussion had been limited to just the X-Y plane. Why is that? Who is to say - or said - that oblique planes are not involved and that the ordinates are orthogonal/normal within that/those plane/s?

It is far too easy to forget - or disregard - the objective of the OP and to presumably (have to?) to stay within the parameters set by machines, tools and accessories in an average HSM shop.

Theorising and discussion about a job is one thing - but applying it in the practical limits of a (HSM) shop may be quite another.

Not being able to see the wood trees is one thing - but being too busy to sharpen the axe is another, and far from "fruitful" either.

John Stevenson
01-18-2009, 07:19 PM
John Stevenson made some very telling points ("reality checks"?) along the way - the main one, implied if not said - was that providing that if it was dealt with as separate 2-D jobs in succession - that if it could be drawn (CAD or paper), then it could be drawn on the job (aka "marked out"). All that was needed was a reasonably good flat surface, a rotary table (vertical mode), a hammer and centre/prick punch, a digital/vernier height guage (or a scribing block, a surface guage - or a scriber and a good rule(r), and you are pretty well set to go.



Where was rotary table in vertical mode mentioned ?

.

dockrat
01-18-2009, 07:45 PM
John Stevenson made some very telling points ... All that was needed was a reasonably good flat surface, a rotary table (vertical mode), a hammer and centre/prick punch, a digital/vernier height guage (or a scribing block, a surface guage - or a scriber and a good rule(r), and you are pretty well set to go.

Am I missing something here??? Why would the table have to be vertical???

Edit....oooops...I think John beat me to it ( BTW John...did you run out of virgins while I was away??? :D )

John Stevenson
01-18-2009, 07:51 PM
Am I missing something here??? Why would the table have to be vertical???

Edit....oooops...I think John beat me to it ( BTW John...did you run out of virgins while I was away??? :D )

No I had problems, did a web search and the last know sighting of one in the UK was on a bus trip to Blackpool by the Cadbury Chocolate factory Social Club in 1924,

However the 1925 census failed to find any.

.

oldtiffie
01-18-2009, 08:17 PM
Oops, sorry John and dockrat.

My error there - sorry - my apologies - again!!.

I was referring- or meant to refer - to marking angles out on the job on a flat surface. But the OP didn't specify that the rotary table had to be used in all parts of phases or in the horizontal plane either - or restricted to the horizontal or any plane/s between the horizontal and vertical either.

Its too easy to read an inference into a requirement and accept it as "gospel" providing that enough others "climb on-board" and/or it is neither questioned nor refuted. This is the "it must be right because no-one - or not enough - either challenged it or said it was or might be wrong" approach.

Dockrat: the reason I referred to the vertical with the rotary table was that in the "mark-out" phase it is easier to clamp the job to the vertical rotary table as it becomes relatively easy to mark both "X" and "Y" as well as any angles - with the "marking out" tools (mentioned previously) as they too work in the vertical plane on a flat surface/surface plate. Those items marked out in the vertical can then relate to or be related to in the horizontal when mounted on the mill/machine table or the rotary table, vise etc. that in turn are mounted/clamped to the table. It is quite possible that the job can be at least partially if not entirely marked out on the job on the vertical rotary table, left fixed to the rotary table and then the job and rotary table moved and clamped to the mill table as a combined unit for milling/machining.

Also, if I may, in regard to this/your question to John S,


.............................................
............................................
Edit....oooops...I think John beat me to it ( BTW John...did you run out of virgins while I was away??? )
Perhaps Richard Branson either spirited them away or stole 'em etc. as they might have been his anyway!!!

http://i200.photobucket.com/albums/aa294/oldtiffie/Funnies/Virgin1.jpg

BadDog
01-18-2009, 10:12 PM
"With a rotary head, you use the main table to move the rotational center on the part."

Okay.

"You then change radius or make linear transitions using the single cross slide of the head."

So just one slide can mill linear transitions (lines, angled lines) for both X and Y coordinates?

Yes, you just swing the head till the cross is in the orientation (angle) you desire to travel. It's almost completely opposite the way you think of a rotab with top slide...


"The limitation here is that you can only handle parts where the radius and linear transitions are within the rotary head cross slide range."

So it's only for small parts less than the distance of travel of the single slide unless you create multiple part zeros?
Not necessarily. The part could be enormous and limited only by the size of the main table. But EACH individual angled transition OR radius would have to be within the rotary heads cross limits. Any transition along the main table axis is limited only by that table. And that's just the "stay in the cut mode". Even if you run out of cross for the transition, you could always pick up, move over, reset, and continue along an angle that is longer than a single rotary head translation would allow. The only thing that is hard limited with no effective work around is radius limits.

Or imagine a sort of serpentine part, perhaps over 2' long. At each zig-zag vertex is a radius arc of 1" radius, and center to center distance is maybe 4". This could easily be done by a rotary head with only ~6" travel (like the Volstro), even though it's over 2' long...

Neil Jones
01-18-2009, 10:21 PM
"Yes, you just swing the head till the cross is in the orientation (angle) you desire to travel. It's almost completely opposite the way you think of a rotab with top slide..."

Got it. Thanks!

"Not necessarily. The part could be enormous and limited only by the size of the main table. But EACH individual angled transition OR radius would have to be within the rotary heads cross limits. Any transition along the main table axis is limited only by that table. And that's just the "stay in the cut mode". Even if you run out of cross for the transition, you could always pick up, move over, reset, and continue along an angle that is longer than a single rotary head translation would allow. The only thing that is hard limited with no effective work around is radius limits."

"Or imagine a sort of serpentine part, perhaps over 2' long. At each zig-zag vertex is a radius arc of 1" radius, and center to center distance is maybe 4". This could easily be done by a rotary head with only ~6" travel (like the Volstro), even though it's over 2' long...""

Thanks very much for the detailed explanation. I'm ready to borrow one of these Volstro heads and try it out. What do good ones sell for used on e-Bay?

dp
01-18-2009, 10:48 PM
Thanks very much for the detailed explanation. I'm ready to borrow one of these Volstro heads and try it out. What do good ones sell for used on e-Bay?

Between $500 and $1200 last I looked a few days ago, depending on how complete the kit is.

LES A W HARRIS
01-20-2009, 06:01 AM
Neil, Looks like you are on your way. Looked up my notes, here are some views of the layouts for setups, as has been noted just figure cutter positions for start & stop like CNC. The sample parts were two off, inner & outer, upper & lower, (17) CNC shops no bid back in 2002.

http://i37.photobucket.com/albums/e97/CURVIC9/NILLWORK/Fullscreencapture120200920939AM.jpg







http://i37.photobucket.com/albums/e97/CURVIC9/NILLWORK/Fullscreencapture120200915908AM.jpg


http://i37.photobucket.com/albums/e97/CURVIC9/NILLWORK/Fullscreencapture120200914435AM.jpg

http://i37.photobucket.com/albums/e97/CURVIC9/NILLWORK/Fullscreencapture120200914822AM.jpg

http://i37.photobucket.com/albums/e97/CURVIC9/NILLWORK/Fullscreencapture120200920305AM.jpg


Cheers,

bobw53
01-20-2009, 12:15 PM
Les, you forgot the finished product

http://www.kitpack.com/images/L3010260.jpg
Radome Hinge Assembly

Neil Jones
01-20-2009, 06:16 PM
Les,

What you posted is exactly what I intend to do/have when I attempt to mill a complex profile/contour with either a Volstro head or a rotary table with built in X,Y slides.

Circlip
01-21-2009, 07:27 AM
Both components shown would be difficult to make using the Volstro head if I understand the workings of it. POP using Rt/co-ord.

Regards Ian.

(Bablefish translation POP - Item of urine) Brit term.

Norman Atkinson
01-21-2009, 07:50 AM
And if we rotated it 90 degrees-and why not-

Could we call it 'Ornamental Turning'

If so, it is back to Holzapffel.


Norman

BadDog
01-21-2009, 01:20 PM
Both components shown would be difficult to make using the Volstro head if I understand the workings of it. POP using Rt/co-ord.
A Volstro rotary head would have no problem with the shape, but that large EM and the standard mill for the undercut would never work. The Volstro head is just too small. However, remember that the Volstro is just the most common Bridgeport sized accessory of that function. A larger rotary head (general term for that function) such as the K&T would have NO problem making that part in double or even triple (more?) scale. Both the rotary head and the coordinate rotary table have almost exactly the same function and capability relative to envelope(s), one just turns part of the function inside out with regard to the operators perspective. Basically, the operations change but the result stays the same...

LES A W HARRIS
01-21-2009, 02:05 PM
Robert, nice pic of the finished assy, did not get one of them. Happy "New Mexico" by the way, was at the Oncologist yesterday one year of remission, (Yeah)! Have started exercise therapy to get my strength built back up.



Neil, the Volstro Head only takes up to 3/8" dia collets, as I recall, so even a 1/2" dia end mill with 3/8" dia shank, does not allow for much hogging; but even so one can do some outlandish parts with one.

Cheers,

Circlip
01-21-2009, 02:54 PM
A combined R/T,co-ord with the co-ord on top is OK, cos that's the function you need to do both inside and outside arcs, moving the centre of rotation of each arc to that of the table. Once the job is clamped, you dont unclamp it untill the whole profile has been machined, and yes BD it's just clicking how you can achieve the internal and external arcing functions with the Volstro with a single slide, and as you quite rightly state each has its own ENVELOPE. It then comes down to preferance and what you're "Brought up on" and I'm not even going to think about deciding that one.

Surfice to say however, a rotary table with an X-Y table underneath it is surely called "a milling machine with a rotary table on it"??

Regards Ian.

John Stevenson
01-21-2009, 07:53 PM
OK I'm going to have a punt at this.

First things first this is for an X Y table mounted on top of a R/T.

You will also either need a detailed drawing, CAD or a scaled up drawing on graph paper and some decent Tech Drawing measuring instruments or be decent at trig.

For ease of use I have used CAD, remember this is just a simple tutorial.

Take this part as given as a job.

http://www.stevenson-engineers.co.uk/files/arcs1.jpg

First off we have to redraw it or re orientate it in CAD so were are working on an XX plane or a YY plane, straight up and down or straight across to the geometrically impared.

So we now finish up with this.

http://www.stevenson-engineers.co.uk/files/arcs.jpg

Note the original drawing in black and the tool outline in red. The tool outline in this case is 5mm off the work to allow use of a 10mm cutter.
Sorry for the metric it's just more convenient to me, if it upsets you just work in units.

So the first thing to do it t make sure you have adequate travels on the XY table before setting a R/T centre.

[1] Set the work so the 0,0 point, top left hole is on the R/T zero. How you do that is up to you, many ways and I'm not getting side tracked.
[2] Starting with to top left arc we need to go to the start of it, the arc is 110.22 degrees long so we need to back off 110.22 - 90 = 20.22 degrees. Point A
[3] Wind the mill table X in so the centre of the cutter is 15 mm or units away from the centre of the arc, that will put the edge 10mm away as per the drawing.
[4] Rotate the R/T thru 110.22 degrees and that will do the first arc and the 50mm long straight will be pointing vertical or in the YY plane. Point B
[5] Then move the mill table 50mm in the Y to finish up at the start of the next arc. Point C
[6] First tricky bit, raise the cutter clear of the work and move the XY table on top of the R/T towards you by 50mm and 10mm to the left. This will put the second arc on the R/T zero point.
[7] Move the cutter over 10mm to the left using the mill table and lower the cutter back into the work and turn the R/T thru 149.49 degrees. You finish up at point D
[8] The straight D E is now level and you can move the mill table in the X 40mm to finish up at point E.
[9] Raise the cutter and move the X Y table 40mm to the left and 5mm towards you to get arc 3 over the R/T zero.
[10] Also move the cutter 5mm towards you using the mills Y axis and lower back into the cut.
[11] Rotate the R/T 110.29 degrees to finish up at point F.
[12] It's now a straight run of 38.83mm to finish up at the start point.

I think this is OK as it's late here and I'd appreciate someone checking my figures.

As you can appreciate it's a long job and we must give true appreciation to the tool makers of yesterday.
remember I haven't covered taking backlash into account here and getting a true blemish free contour is hard.

Now you see why I like CNC :D

.

lane
01-21-2009, 09:26 PM
I have been reading all of this for the past few days trying to make heads are tails of it . After seeing the drawing John s. made and the other one . I used to do that day in and out machining Dies years ago. Easy enough All that is needed is a X-Y rotary table .like a big Yausa are Toyke. A X-Y rotary table is easer to use than a Volstro head. I have and use both. So I know.

oldtiffie
01-21-2009, 11:09 PM
Well,

I went right back to basics: shop math and tool-making.

The "trick" (if there is one) is to not just look at the job, but to look through and past it and to find at least two - possibly more - optional ways of doing the job and then evaluate the best in terms of reduction of complexity and keeping within the capacity of the machines, tools and accessories in the shop. I always start from basics and work up until I hit the level I need in terms of practicality. So I go for the simple "low tech" stuff and methods.

I did the following "as a concept" and "on paper". In short, I "drew" it without a CAD system. Everything can be done on a mill table (clamped on spacers/parallel strips), other than the radii. There are several set-ups but they are quick and easy to do. A good dial indicator was needed for the set-ups.

I prefer to mark a job out as it really assists to see if the set-up is right instead of just relying on calculations. A good setting-up/out will be well within 0.005".

I will jot it all down and post it in the next day or so.

I used the Law of Cosines in the first instance to solve it as a proff of concept but there is a huge amount of calculations. One I slip (I made a couple but recovered) and yiu are "toast". After I wwas satisfied that it worked, I gave it away and went even further back to basic shop geometry and trigonometry and shop fundamentals and it worked like a dream.

I just wanted to prove that it was quite feasible to get a good result without CAD - which we sure did not have when I was in shops -but we had everything else that was needed as I hope to show.

All I simulated (at my desk) was the use of a marking out table, a (then vernier, now digital) height guage, scribing-block or surface guage, 3 x "Tool-makers buttons", a good set of (then vernier, now digital) calipers or micrometers, slip guages or spacers to suit, and a couple of parallel strips (no specific sizes), hammer, centre-punch, dividers, and a rotary table that will stand vertically.

The only "X"-"Y" I needed was the mill slides.

I will post the solutions in the next few days.

lane
01-21-2009, 11:31 PM
We used to draw it out 10 times scale and measure with a rule .you could get so close it was scary.

LES A W HARRIS
01-22-2009, 01:40 AM
OK I'm going to have a punt at this.

First things first this is for an X Y table mounted on top of a R/T.

You will also either need a detailed drawing, CAD or a scaled up drawing on graph paper and some decent Tech Drawing measuring instruments or be decent at trig.

For ease of use I have used CAD, remember this is just a simple tutorial...

First off we have to redraw it or re orientate it in CAD so were are working on an XX plane or a YY plane, straight up and down or straight across to the geometrically impared...

So the first thing to do it t make sure you have adequate travels on the XY table before setting a R/T centre.

[1] Set the work so the 0,0 point, top left hole is on the R/T zero. How you do that is up to you, many ways and I'm not getting side tracked.
[2] Starting with to top left arc we need to go to the start of it, the arc is 110.22 degrees long so we need to back off 110.22 - 90 = 20.22 degrees. Point A
[3] Wind the mill table X in so the centre of the cutter is 15 mm or units away from the centre of the arc, that will put the edge 10mm away as per the drawing.
[4] Rotate the R/T thru 110.22 degrees and that will do the first arc and the 50mm long straight will be pointing vertical or in the YY plane. Point B
[5] Then move the mill table 50mm in the Y to finish up at the start of the next arc. Point C
[6] First tricky bit, raise the cutter clear of the work and move the XY table on top of the R/T towards you by 50mm and 10mm to the left. This will put the second arc on the R/T zero point.
[7] Move the cutter over 10mm to the left using the mill table and lower the cutter back into the work and turn the R/T thru 149.49 degrees. You finish up at point D
[8] The straight D E is now level and you can move the mill table in the X 40mm to finish up at point E.
[9] Raise the cutter and move the X Y table 40mm to the left and 5mm towards you to get arc 3 over the R/T zero.
[10] Also move the cutter 5mm towards you using the mills Y axis and lower back into the cut.
[11] Rotate the R/T 110.29 degrees to finish up at point F.
[12] It's now a straight run of 38.83mm to finish up at the start point.

I think this is OK as it's late here and I'd appreciate someone checking my figures.

Now you see why I like CNC :D

.
Mill, BIG X-Y, Rotary rig small x-y.

Yuasa had 6.00" x-y, so 50mm is ok.
Geometry check;

http://i37.photobucket.com/albums/e97/CURVIC9/2009%20MILLWORK/Fullscreencapture121200992407PM.jpg

Added 3rd radius & co-ordinates.

Toolpath, would depend, conventional or climb cut! conventional rotary setting if set to "0" at start, would be increasing throughout, climbing would require subtracting the angles as you progress.


http://i37.photobucket.com/albums/e97/CURVIC9/2009%20MILLWORK/Fullscreencapture1212009101348PM.jpg

Yes, except [12]. you were tired, that's 38.73mm not 38.83mm. (Picky Basket).


10:39PM here now i'm tired, Night all!

Cheers,