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View Full Version : I finished a little project I started a few years ago



Evan
03-13-2010, 12:22 AM
I started building this CNC rotary table before I built my mill. When I had finished making nearly all the parts I decided I didn't need it and proceeded on building the mill. That was several years ago and I put what amounted to a cnc rotary table kit in a box under the bench. I decided yesterday to finish it and it didn't take very long.

Except for the stepper motor and the shaft bearings the rest is made from stock. It uses a full diameter teflon sheet as the bearing for the worm wheel which is the base of the rotating unit. The wheel is cut from 7075-T6 aluminum which is harder and stronger than mild steel. The worm is cut from stainless steel and is supported by ball bearings.

There are no formal adjustments for lash or play. It was designed and made with a slight preload of the worm to the wheel and with zero end play of the worm. If necessary adjusters can be fitted to slightly move the bearing blocks closer to the worm wheel. The adjusters if required are very simple, one set screw each in the end cover of the bearing blocks

http://ixian.ca/pics7/rt1.jpg


The unit has a generous supply of grease and is sealed against swarf or coolant intrusion. On the bottom right image you can see the gasket that seals the opening for the table mechanism.

http://ixian.ca/pics7/rt2.jpg

The left image shows the hob I made to cut the worm wheel. It is made of 1040 steel and hardened.

http://ixian.ca/pics7/rt3.jpg

dp
03-13-2010, 12:28 AM
What are the plans for the threaded center hole?

And nice work!

Evan
03-13-2010, 12:38 AM
A dead centre can be fitted there.

8ntsane
03-13-2010, 12:46 AM
Evan
Every time you post your work, it just makes me drool. You do such incredible work. That Milling machine you built, is a master piece of your work as well. I allways look forward to seeing things you have built, in part,or whole. Even when you take somthing and mod it, One example comes to mind, the drill press, that you void the warrenty, and mounted it up on your lathe,,that was priceless,;)

Paul

MTNGUN
03-13-2010, 12:51 AM
Impressive.

gary hart
03-13-2010, 12:55 AM
Like the low profile, very nice cnc rotary table.
Is there teflon sheet on each side of the top cover plate?

Evan
03-13-2010, 01:07 AM
The teflon sheet is under the entire rotating mechanism. It is only .002" thick and the assembly is preloaded against the base and the teflon with a fine thread bolt that runs through a ball bearing on the base which locates the table against side loads. The entire unit is zero lash in all directions so I didn't bother fitting a table clamp although I have provided a mechanism to do that. The actual table clears the top cover plate by .010" inch and lightly touches the top surface of the gasket. The top cover plate is just a cover and doesn't provide support for the table.

Black_Moons
03-13-2010, 01:23 AM
Very nice project, the belt guard gives me ideas for my sheet..
Why did you put the motor on the opposite side of the table of the hand wheel? no real comment on it just wondering, I sometimes have serious problems making irrelivant design decisions.

Evan
03-13-2010, 01:42 AM
It was the only length of belt I had that would fit the pulleys.

knudsen
03-13-2010, 01:53 AM
Very nice, Evan!

darryl
03-13-2010, 03:07 AM
Keep it up, Evan. Your decision to complete an old project is helping to push me towards doing the same- I really need to finish the folding guitar project I started.

Kibby
03-13-2010, 06:09 AM
Nice work, Evan. I bow to your superior kung fu. Posts like this are one of the reasons I love this site!

jackary
03-13-2010, 06:22 AM
Superb work Evan and nicely finished
Alan

Your Old Dog
03-13-2010, 07:41 AM
Really nice project Evan. If I had the skill to do it, I'd pray for the patience. You are an inspiration to the board and I'm grateful that you hang with us here on this forum. It's a great board but we have several here who turn out superior work and it's fun for some of us rookie machinist to view.

Could you hazard a guess as to how many hours you might have into this project? I'm asking because I feel that all my projects seem to take 10 times longer to accomplish then they should. It would be useful to know if this was just whipped up or if you have many hours in to it.

Evan
03-13-2010, 09:01 AM
Everything I build takes ten times longer than it seems like it should. I don't keep track of hours at all but it was more than a few days, probably a few weeks. This was made before my mill so all the parts were either turned, fly cut or milled on my SB9. That was a very slow process.

These days I usually finish my projects. This one was abandoned only because I judged it unnecessary at the time. I have now found that I have a use for it so I completed it.

I am also curious to see if I can do anything useful with it by sticking it between centres on the 4th axis on my mill which would make it a five axis machine.

DFMiller
03-13-2010, 10:09 AM
Evan,
Very nice work.

Duffy
03-13-2010, 10:12 AM
Evan:- HELP me with this axis-counting process! Left-right is one, forward and back is two, (never mind x-y-z nonsense,) up and down is three, round and round is four. That leaves round and round the left-right axis for five? Would you then be able to mill spiral tap bodies and odd diameter milling cutters with stange numbers of flutes? As has been said-VERY impressive work. Duffy

Bill in Ky
03-13-2010, 10:46 AM
Very nice work. Thanks for sharing it.

lazlo
03-13-2010, 01:26 PM
Very nice Evan!

You say the worm is supported by ball bearings, but the bottom right picture looks like a bronze bearing? Or is that a flash artifact?

Paul Alciatore
03-13-2010, 04:37 PM
Evan,

As always, very nice work. I don't know if I could stand putting all those parts in a box for for several years to await assembly. I would have lost sleep or something to get it together.

If I counted correctly, it looks like the worm wheel has 120 teeth. So that's 3 degrees per revolution. You probably have a 1.8 degree stepper so that is 200 steps per revolution there. That gives 200/3 = 66.666... steps per degree. Not what I would choose. But there is a step down by the drive belt. Is it a 3X or what? I am curious about the actual numbers that you choose here.

Evan
03-13-2010, 05:27 PM
You say the worm is supported by ball bearings, but the bottom right picture looks like a bronze bearing? Or is that a flash artifact?


You observe correctly. I changed the design at that time so that it is all ball bearing.

Paul, I will have to go count it myself. Since it is CNC and that is the intended mode of operarion it really doesn't matter what the step per degree work out to. Not only is there a gear down on the pulley but it will by running in 1/4 step mode.

Sorry for not being very responsive to questions today but I am in the middle of a kidney stone attack. I am guessing that being slow roasted over an open fire might be more comfortable.

aostling
03-13-2010, 07:00 PM
Sorry for not being very responsive to questions today but I am in the middle of a kidney stone attack. I am guessing that being slow roasted over an open fire might be more comfortable.

Having had two of those myself, I know the nausea and pain of this. Finally had a lithotripsy (ultrasound bombardment), not equipment I'd expect to be in Williams Lake. You have my sympathy, and I hope you get into the hospital ASAP.

lazlo
03-13-2010, 07:39 PM
Sorry for not being very responsive to questions today but I am in the middle of a kidney stone attack. I am guessing that being slow roasted over an open fire might be more comfortable.

Ack! Sorry to hear that Evan :( Hope you get it squared away...

Ken_Shea
03-13-2010, 08:03 PM
Super Evan,
Also always enjoy seeing your building of items, you've come to the point of not only being able to make pretty much what you want but also under standing it as well, both remarkable in their own way.

Very sorry to hear of the Kidney stone attack, never experienced it but heard it can be excruciating, which the slow roasted over an open fire would surley qualify.

Evan
03-17-2010, 11:21 PM
I hooked up the table tonight and it works without a hitch. It will run 24 degrees per second with a theoretical resolution of 6.75 arc seconds.

The reason for completing this build is because I need to make some high resolution encoders. Rather than deal with even minute amounts backlash the best way to accomplish this is to rotate the work under the laser always in the same direction with the laser moving in only a single axis to scribe it's lines. The encoder will be a 1000 line encoder for use with the servo controller I bought for the Z axis of the mill.

airsmith282
03-17-2010, 11:37 PM
cool rig evan, you gota do a video of it in action

Evan
03-17-2010, 11:56 PM
OK, will do.

Evan
03-18-2010, 01:14 AM
OK, here is a short video of the table in action. It's the best I could arrange (cough ) on short notice. :D

http://ixian.ca/video/4inchtable.wmv

darryl
03-18-2010, 02:55 AM
:)--------:)

John Stevenson
03-18-2010, 04:47 AM
Is that table for Stevie Wonder ?

Evan
03-18-2010, 06:03 AM
It's a conductor's baton John. Personally I think that this little table is one of the cutest items I have made.

John Stevenson
03-18-2010, 08:40 AM
No Evan, just a black screen here , no video.

Evan
03-18-2010, 09:04 AM
Seems fine at this end when I download it. It is the same codec I normally use for Window Media Video.

Weston Bye
03-18-2010, 10:41 AM
Played fine for me.

Evan
03-18-2010, 11:45 AM
Plug a couple more schillings in the meter John. :D

John Stevenson
03-18-2010, 06:25 PM
I'll try my laptop later, still nothing here but I can get all sorts of other video with no problem.

Paid the 'lecky bill yesterday so that can't be the problem, unless I upset the lady in accounts.

I rang her up to say they had made a mistake on the bill, she asked what the problem was.

I replied you have sent me British Steel's by mistake.

Her rely - How droll...............

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