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JeffKranz
09-23-2006, 07:10 PM
Here is my latest project. I wanted to be able to use a wood router on my CNC machine to do some high-speed work. I have a Dewalt vari-speed DW625 router that has a 3 HP motor. Since the quill has the servomotor, I couldn’t just mount it to the side of the head. First thought was to clamp it on the quill but that would cause problems with homing the machine.

Since I made a bracket to mount to a 40 Taper shell mill holder I needed a way to stop rotation of the plate. I used a linear bearing and needed to machine a holder for the bearing to mount to the head. I just finished it today so I didn’t have a chance to use it but I’m sure it will work just fine. I just need to make sure that I don't try to start the spindle.

I have added some pictures in case you wanted to see it.

Jeff

http://members.accesstoledo.com/beagly/keep/cncrouter1.jpg

http://members.accesstoledo.com/beagly/keep/cncrouter2.jpg

http://members.accesstoledo.com/beagly/keep/cncrouter4.jpg

http://members.accesstoledo.com/beagly/keep/cncrouter6.jpg

b2u44
09-23-2006, 07:35 PM
Jeff--

Nice looking work. Perhaps you should install some sort of switch in the power wire that goes to the spindle motor... that way you have no chance of accidentally turning on the motor.

Very nice job though. I might try to rig something like that up for my mill. Let us know how it works in terms of accuracy and surface finish.

--Ben

Evan
09-23-2006, 08:08 PM
That looks cool, should make a nice mess. I would go a step further than Ben suggests and figure out some sort of positive lockout for the spindle power when the adapter is in place.

John Stevenson
09-23-2006, 08:39 PM
Why not clamp around the quill ?
No need for interlocks or stop bars.

.

b2u44
09-23-2006, 09:22 PM
John--

Some of those open CNC mills 'home' by fully retracting the quill. If something is clamped to it, it won't be able to retract and you'll end up with busted gears or feed-screws.

--Ben

JeffKranz
09-23-2006, 10:18 PM
On this machine when the machine is homed, the quill must reach a limit switch. My first thought was to re-adjust the limit switch but then again the controller know how much range of travel it has and when it would go the other direction it would hit the hard stop which causes the servo motors to disconnect. The only solution I had was to mount it to the tool holder and add the rod to stop rotation.

Evan - I'm thinking of adding a limit switch that will trigger when the rod is installed and disconnect the power to the motor. I will need to look at it since it is a three phase two speed motor. Not sure how many wires I need to disconnect due to the two speed motor.

jdunmyer
09-24-2006, 02:17 PM
Jeff,
Your limit switch should be connected to the motor starter that operates the spindle motor, not to the motor wires themselves. The starter/contactor probably has 2 coils and a mechanical interlock for the 2 speeds, so the easiest way to prevent operation would be to break the common wire on the 2 coils.

Maybe I need to stop over and look at it. :-)

Dawai
09-25-2006, 07:46 PM
http://img.photobucket.com/albums/v85/ibewgypsie/cnctooling_001.jpg

I made a spyder of a mount, put a bar on top to slide into a collet..

Worked once for a wooden carved sign.. not used it since.

JeffKranz
09-30-2006, 03:37 PM
Well, taking the advice of Evan and really didn't need the help of Jim :-) (even though he has help me many times in the past) I added a limit switch today and tested it all out. There was four contactors that controlled Forward/reverse/high/low. I just found which wire went to each of them and hooked that to the limit switch before the first contactor.

Here are some picture on of the final project and the first 3-D cut using a 1/8 carbide ball cutter and some G-Codes I found on the internet.

Jeff

http://members.accesstoledo.com/beagly/keep/cncswitch1.jpg

http://members.accesstoledo.com/beagly/keep/cncswitch2.jpg

http://members.accesstoledo.com/beagly/keep/cncrouterball.jpg

http://members.accesstoledo.com/beagly/keep/cncrouter1st.jpg

Evan
09-30-2006, 05:10 PM
That is extremely cool. Now I really must get my CNC going. Would you mind telling what that material is?

I've been messing with software and have been generating G-codes for milling gears, in particular change gears for my SB9. I have already cranked out the code for a 37/47 tooth metric transposing gear. It will need a 1/16" end mill to cut it in aluminum or brass and a high speed spindle will be nice so it doesn't take a week.

Once I get things up and running and have a chance to test the codes I will make them available.

JeffKranz
10-01-2006, 08:17 AM
Evan,

I'm 95% sure it is delrin. I was at an auction and some guy purchased a wall full of aluminum, brass & plastic. He was just going to scrap the metal and approached him and asked him if he wanted to sell the plastic. He told me to make him a offer so I said $50.00. He said "sold". What is not pictured was a full sheet of 1/4 lexan still with the protective paper, a large round piece of nylon 18" in diameter and 24" long and a bunch of lenghts of round and angle stock in plastic. I used some of it on projects and sold one piece of brown delrin 6" diameter 12" long on ebay for $48.00.

What is one the shelves below in order

Rubber
Delrin
UHMW
UHMW/PVC
Acrylics/Peek/odd stuff
Nylons
Some Black stuff is something for the food business that machines like a charm I use that stuff to check out cutter paths.

Jeff


http://members.accesstoledo.com/beagly/keep/plastic.jpg[/IMG]

Evan
10-01-2006, 09:34 AM
Holy cow! That's a small fortune in plastics. Are you sure the bottom shelf isn't Delrin or some type of acetal? There aren't that many plastics that come in true black and machine as nice as acetal. That stuff is expensive to be using as "machinable wax".

Mortimerex
10-01-2006, 03:31 PM
Holy cow! That's a small fortune in plastics. Are you sure the bottom shelf isn't Delrin or some type of acetal? There aren't that many plastics that come in true black and machine as nice as acetal. That stuff is expensive to be using as "machinable wax".


I'm no expert but I thought Delrin was just a trade name for acetal? Anyway it looks and sounds like black acetal. The black doesn't have as high as lubricity as the white acetal but still machines very nicely, the white is almost waxy. By the way, is the reason for mounting the router that the router has a much higher rpm than the mill? I was thinking with acetal you could just get 1/8" inch (and/or 1/4" i forget which is most standard for routers) r8 collet and use the router bits in the mill with about the same results and alot less bother? I could see if you want to make a whole seperate cnc router that could emboss designs on an entire 4'x8' sheet of wood or plastic but if your gonna use the mill why not use the mill? Forgive my ignorants :o

Evan
10-01-2006, 03:41 PM
Delrin is acetal homopolymer. Generic acetal is normally acetal copolymer. They have slightly different properties. Both are available in natural (white) and true black and have similar machining properties.

Mortimerex
10-01-2006, 04:29 PM
Delrin is acetal homopolymer. Generic acetal is normally acetal copolymer. They have slightly different properties. Both are available in natural (white) and true black and have similar machining properties.

I majored in chemical engineering for a year and took some classes in organic and polymer chemistry even after that but I don't recall much about homopolymers. But thats probably just my faulty memory and lack of actually using the knowledge, I will have to do some internet searching to brush up I guess. The actual difference seems pretty negligable for practical use. The enco catalog on page 643 does say, " ACETAL, also known as Delrin..." but then again salesmen often are fast and loose with product specifications...

Evan
10-01-2006, 04:43 PM
The homopolymers (Delrin) have slightly higher strength, about 10 to 15% but tend to have lower density and some porosity in the center of extrusions. The copolymers have lower strength but even density.

Mortimerex
10-01-2006, 04:55 PM
Still, Delrin sounds like a trade name. And its got a big fat (R) after it. Basically, its a slightly different blend of acetal with a fancy new trade name. Pardon my sarcasm but it seems every 10 years (or even less) the same old things are given fancy new names along with a higher price.

Actually my old "Industrial Plastics" book lists acetal (homopolymer) but says nothing about copolymer. POM Du Pont 1960 (polyoxymethylene is the correct chemical term for this polymer, acetal is the generic term.) Sorry no mention of Delrin.

Evan
10-01-2006, 06:52 PM
Sure, Delrin is a trade name, trademark of Dupont. The differences are significant enough that they warrant consideration in some applications.

Homoplymer:

http://www.matweb.com/search/SpecificMaterial.asp?bassnum=O1280

Copolymer:

http://www.matweb.com/search/SpecificMaterial.asp?bassnum=O1250

JeffKranz
10-01-2006, 07:43 PM
Maybe it is Actel. That is the problem with mystery plastics / metal. I work for an injection molding firm that molds stuff in Actel at one of our plants. Seems to me that you can burn it and it does something unique so you can tell if it is Actel. It seem to cut a little better than the Delrin and does have that waxy look.

BillH
10-01-2006, 08:00 PM
Interesting, Little Machine Shop sells a nearly identical part for the mini mill for mounting a Praxxon die grinder off to the side as a high speed spindle for the smaller cutters. Apparently the Proxxon is rated for continous work and doesnt wear out fast.

Mortimerex
10-01-2006, 08:28 PM
Sorry but acetal can be a homopolymer or copolymer. Probably the same for Delrin(R). Note also that all sources claiming that Delrin(R) is superior to acetal are (that I have seen so far) all from Du Pont which of course gets more money selling Delrin(R) than acetal even though they can be made from the same ingredients. There is greater difference in the composition of todays gasoline vs 1980s gasoline than there is between Delrin(R) and acetal I would wager.

Maybe you should read up on the difference between chemical formula, trade name, and generic name for chemicals mostly polymers and drugs that have the plethora of names for the same thing. I swear Evan, refuting your BS almost justifies not selling all my college texts.

Evan
10-01-2006, 08:36 PM
Both types of acetal polymer are food rated so I strongly suspect it is acetal. Here is a good example why it can matter which type it is.

http://www.immnet.com/articles?article=523

[added]
I didn't see your last post when I put this up. I didn't realize you are also on a campaign to discredit me. Now, what was that about BS?

[added later]

You may as well sell the books. They aren't doing you any good.

Mortimerex
10-02-2006, 06:52 AM
The food grade is likely due to varying methods of actually manufacturing the SAME CHEMICALLY IDENTICAL substance. But to be food or medical grade you can not re melt "scrap" back (not necessarily junkyard scrap just the dregs from the last medically pure batch is no longer considered pure but being a thermoplastic they can toss it into the next batch of non medical grade and has identical physical properties)in even if the scrap is chemically identical due to possible microbial/ virus contamination. Now I'm a mechanical engineer not a chemical engineer or chemist so one of those can read this and probably get teed off at my superficial explanation and slap me around.

I may be incorrect but seem to recall several medical associations and possibly engineering associations trying to ban the use of trade names since they are basically a big fat scam perpetrated on the ignorant. Trade name and generic name have the same chemical formula and properties aside from some possibly minor additives.

Maybe I should sell you my books since they aren't doing me any good maybe they will help you not be so full it.

JeffKranz
10-02-2006, 08:59 AM
Man, all I wanted was to show how someone could hook a high speed router to a CNC machine and this thread turned to a fight fest. You both need to cool your jets.

Evan you should just stop replying to this subject since we all know you have great knowledge and feel honored when you reply with answers. Maybe they aren’t perfect but most of the time they get people pointed in the right direction. If we wanted details down to the atom, we probably should take that up with application engineers at the specific company. Also, I won’t bring up gas springs ;-)

Mortimerex – Don’t sell your books – they are a great value for debate but maybe you don’t need to go for the jugular vein.

Chill out guys!

Evan
10-02-2006, 10:03 AM
I had no idea there was any "fight" going on until Mort's BS comment. I just thought he didn't know there was a difference and wanted to know more. I was right about him not knowing there was a difference. I mistook his other motives. I'm sorry he started this.

Evan
10-02-2006, 10:08 AM
The food grade is likely due to varying methods of actually manufacturing the SAME CHEMICALLY IDENTICAL substance.
O2 and O3 are made from the exact same chemically identical substance. Which would you rather breath?

Diamond and graphite are chemically identical too.

DR
10-02-2006, 11:36 AM
Delrin is acetal homopolymer. Generic acetal is normally acetal copolymer. They have slightly different properties. Both are available in natural (white) and true black and have similar machining properties.

Dont know about the homopolymer versus copolymer business.

I do know from years of machining thousands of pounds of customer supplied acetal (probably the cheapest version they could find) it doesn't all have similar machining characteristics. Some will be significantly better to machine, cuts cleaner, threads better, etc. Some's brittle (untempered?).

Delrin has very consistent machining characteristics from batch to batch and is worth the premium price if the parts are marginally difficult to machine. Problem is, not all plastics dealers can sell Delrin, only Dupont authorized stores.

BTW, natural is not white. Natural is a light tan, white is very white.

Also, from my experience I'd say black is the best machining of all colors. My private theory is maybe they use graphite to make it black which might add lubricity.

Evan
10-02-2006, 11:59 AM
It almost certainly is colored black with carbon black. It's not the same as graphite which is structurally a hexagonal crystal form whereas carbon black is amorphous. Carbon black doesn't make much difference in terms of lubricity. Graphite is used in some plastics such as graphite loaded ballistic nylon which has a dark silvery gray swirled appearance. Easier machining is more likely due to the difference between the homopolymer and the copolymer.

Graphite won't produce a true black because the atoms are arranged in sheets that can reflect light from the planes.

The business of identifying plastics by color can be very misleading sometimes. In the following pic on the left is "black" nylon also known as Nylatron which is really grey because it is loaded with Molybdenum disulfide. It isn't black but everyone in the plastic business calls it black nylon anyway.

The middle piece is ballistic nylon with graphite loading and the right piece is "natural" nylon. Depending on the plastic natural can range from tan to very white. For a really white plastic titanium or magnesium oxides are used as a colorant.

http://vts.bc.ca/pics/plastics2.jpg

These parts are made from acetal copolymer. It's a little easier to knurl than the homopolymer because it is a bit softer. The two types of polymers are not only structurally different they are chemically different too. The copolymer has ethylene oxide added to the homopolymer chains. That's why it is called a copolymer.

http://vts.bc.ca/pics/acetal1.jpg

JeffKranz
10-02-2006, 12:20 PM
I guess I will answer a question from a few days ago, The idea of mounting the router to the CNC mill was to do high speed spindle work in soft material. I also have a full wood shop and would like to do some woodworking using toolpaths and a router. The current mill only has about 5000 rpm and most router bits like to run in the 20,000 range.

Plus - I needed a reason to machine up a few brackets.

Jeff

Peter N
10-02-2006, 03:53 PM
I’m impressed. Evan has actually done a remarkably accurate job on the subject of Acetal for somebody who has not been primarily involved in the industry. Mortimer is right on a couple of points too, if a little more forthright in putting them across.

Now the boring bits…I’ll apologise in advance for the long post but this stuff is pretty much my specialist subject and I couldn’t resist.

Acetal (Polyacetal, Polyoxymethlylene) is a generic name for this material and covers both homopolymers and copolymers. Dupont invented the first Acetal resin, a homopolymer, took out a patent on it, and market it under the trade name Delrin.
Rival companies such as Hoechst, BASF, and Celanese developed copolymer acetals shortly after to get around the Dupont patents and marketed these under trade names such as Hostaform, Ultraform and Celcon. There are now many other equally good Acetal resins on the market from asian producers that can happily be substituted for any of the above.

There are mechanical, thermal, and chemical property differences between the homopolymer and copolymer bases, but in 95% of applications either will do the job of producing springs, bearings, gears, carburettor parts, kettles, ski-bindings and so on.

It can’t be argued that one has superior properties to the other as you will find far greater differences in these across the grades within a single brand name than between a mid-range grade from either. Dupont has something like 70 different grades of Delrin, and Ticona (Hoechst/Celanese merger company) has well over 100 grades in the Hostaform/Celcon range.

The grades have difference viscosity indexes and melt flows due to plasticising and lubricating agents and additives to suit different processes. An extrusion grade will generally have few plasticisers and a low melt-flow index (say around 2-6) to give a high viscosity material with a higher yield strain.
An injection moulding grade will have an MFI of around 12-20 and a lower yield strain. There you have an immediate difference in mechanical properties in a single brand.

A major factor that will affect the mechanical properties of Acetals, including how they machine, is processing parameters. Acetals of either type are highly crystalline polymers. During the melt phase a crystalline polymer reverts to an amorphous structure which allows it to flow, and will re-crystallise during cooling. However the rate of cooling significantly affects the structure, and if allowed to cool at between 110°C - 140°C it will pretty much re-crystallise in its original proportions. However, as the melting point of some Acetals is only around 150°C this is not a viable production proposition as commercial process times become too long, and this is generally compromised to around 80° - 90°C. However, if cooled down at around 50-60C a significant proportion of the structure becomes locked in its amorphous phase.

The result of the above is that highly crystalline structures exhibit markedly greater surface hardness and far less ductility than those cooled at a lower temperature and this will manifest itself in the more amorphous material as greater toughness and flexibility or tearing when machining the material.

As far as colour is concerned, natural Acetal is an opaque white. The picture below shows an ‘as moulded’ sample of Delrin 500P. The part is actually a pickup slider we moulded for a linear potentiometer used in electronic throttle control by Ford America.

http://www.btinternet.com/~p.neill/GHSP_Slider2.jpeg

If the Acetal you have is a light tan colour then one of two characteristics will apply to it. The first is that it may have been subject to time/temperature degradation during processing which will ‘caramelise’ the material and very severely restrict its integrity in any application. Acetal is very easily degraded by incorrect process parameters. The other possibility is that is a grade reinforced with short glass fibres (ca. 100 micron length)that tend to impart a buff/cream colour to it. The third possibility is of course an added pigment, but I have seen very little of this except in finished external appearance moulded forms, certainly not in bar stock.

Black pigmented polymers will use either Carbon Black or Nigrosine (don’t laugh) to achieve the hue, but there are for and against criteria here as well. Carbon Black gives the best UV protection but can’t be used in electronically sensitive applications because of micro conductive issues. Carbon black produces a slight flatter black, and Nigrosine produces a slightly sharper black, with sometimes a very slight bluey-black finish. However, Nigrosine is a liquid pigment and often needs to be incorporated into an inert carrier (like LDPE) when it is compounded. Some post-process customer applications don’t like the (tiny) amount of LDPE carrier, so to confuse things further many black hues carry a mix of both pigments.

With regards to food safety or medical safety or other safety critical items it’s generally not good manufacturing practice to use regrind in these instances. Not so much for the reasons previously stated, but more for the potential change in properties. Dupont & others now quite happily recommend that up to 20% ‘fresh’ regrind may be added to virgin material with no significant loss of properties. The problem arises when you start regrinding the regrind, and then the proportions change to an unknown factor, and you can then experience a significant property change.
If you think about it the microbial/virus issue is fairly irrelevant as the material will reach a melt temperature of between 170° - 210°C in the extruder -injection barrel that will pretty much kill off most things to worry about.

And finally, Jeff commented that you could burn Acetal to identify it. This is very true, but definitely not recommended. Acetal is very flammable and they haven’t yet found a (safe) way to prevent it burning freely. As it burns (and also when it is overheated) it will decompose and give off formaldehyde gas and smoke. This smoke is extremely acrid and sniffing it will have your eyes and nose running, stinging like hell, and you gasping for fresh air. Think ‘Tear Gas’ and you have exactly the same effect. Dumping the burning Acetal in a bucket of water immediately is the best remedy.

Sorry for the diatribe.

Peter

BobWarfield
10-02-2006, 03:58 PM
Mounting a high speed spindle is a great idea for machining softer materials with small end mills. Small end mills are almost essential for CNC profiling if there is much detail involved. The rpms needed are actually surprisingly high to put cutters in their sweet spot, even sometimes for mild steel.

My mill only runs up to 1600 rpm, and will go to 3200 with a different motor. Most folks don't own a mill that does 10K rpm or even 8K, so this is a cheap way to still get the job done. There are also spindle speeders (increasers or multipliers are other names) that are little gearboxes that go in the spindle to increase the speed. Sir John has talked about them from time to time. Very costly new, and even on eBay usually not too cheap.

Best,

BW

PS Nice description of homopolymer vs copolymer types of acetal here for those who care:

http://www.machinedesign.com/BDE/materials/bdemat2/bdemat2_3.html

As usual, Evan had it right. I can only assume there is little else to do so far North but read voluminously and hang out in the workshop! LOL

Evan
10-02-2006, 04:21 PM
I can only assume there is little else to do so far North but read voluminously and hang out in the workshop! LOL
That is the one redeeming thing about winter. It will be snowing here soon. The usual marker date is halloween. We nearly always have the first snowfall by then.

BTW Peter, I have had a lot of experience with certain thermoplastics over the years. The toners used in B/W and color copiers are all thermoplastics and many different formulations have been used including ones based on acetal resins. We had extensive training in all aspects of thermo plastics and the specific applications we dealt with including the care and feeding of the various types of materials used for structural and moving parts in machines.