# 4th axis servo controlled rotary table build



## brino (Jan 10, 2018)

Great project, I'm watching!


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## Jake2465 (Jan 10, 2018)

brino said:


> Great project, I'm watching!
> View attachment 254064



Thanks!


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## Jake2465 (Jan 11, 2018)

I should be getting the rotary table in this coming week. I don't have a chuck for it yet, but I plan to get one for it some time soon.


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## Karl_T (Jan 12, 2018)

I did this exact job a few years ago. You will love this added capability.


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## Jake2465 (Jan 12, 2018)

Karl_T said:


> I did this exact job a few years ago. You will love this added capability.



I can't wait! One of the things I have been wanting to make is gears and having a servo controlled rotary table will get rid of the need for dividing heads.

What software did you decide on for your 4th axis work? Fusion 360 has been very slow in coming up with a good 4th axis solution. Their CAM software can really only do indexed 4th axis and not live 4th axis(it can do live, but only in a couple special cases for finishing work). I found posts on their forums from early 2016 where they said they would have a solution soon...

I saw this software called "DeskProto". I don't know anything about it, but it looks like it can do live 4th axis, and the price is much better as compared to the big players out there.


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## Jake2465 (Jan 12, 2018)

I am watching some of their videos. It looks like their software is better suited for soft material work because the tools don't appear to be able to do any helical ramps into the work, but rather plunge moves. BUT, the software is live 4th axis capable.


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## Karl_T (Jan 12, 2018)

I have a shelf full of gear hobs...
I use electronic gearing with my control, Camsoft, to quickly knock out any gear. 

Yep, CAM software for 4rth axis is hard to come by. Got a fairly easy work around. its a piece of cake to change the encoder counts per unit length in the control. So, lay out your project with X being the X axis and Y being the circumference of your part. Then take the resulting Gcode and change Y to A. Of course, this does not work for code sections that do have a Y move. You got to run that separate.


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## Jake2465 (Jan 12, 2018)

It just came in this morning !!

Ugh! This thing is a boat anchor ! Time to tear the box apart and get it out !


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## Jake2465 (Jan 12, 2018)

It seems to be nicely built and I can't hardly tell if there is backlash present. I would have to put an indicator on it to see how much there is.


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## Karl_T (Jan 12, 2018)

Suggestion. Make the three jaw chuck "adjust true" type. Being able to dial your part to have zero run out is critical on many parts.  This is not a real difficult task to add to any chuck.


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## Jake2465 (Jan 12, 2018)

Made it to the Hangar. Time to pop off the hand wheel.


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## Jake2465 (Jan 12, 2018)

Hmm the hand wheel has a keyway and the dial is a slip fit ring with graduations on it.


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## Jake2465 (Jan 12, 2018)

Another ring came off.


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## Jake2465 (Jan 12, 2018)

It appears I wont have room to just mount the servo inline with the worm screw. I will make a bracket and hang tge servo behid the rotary table.


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## Jake2465 (Jan 12, 2018)

Something like this should do the trick.


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## Jake2465 (Jan 12, 2018)

Now, where to find some cog pulleys and a belt .


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## Jake2465 (Jan 12, 2018)

The two pulleys and the belt have been ordered and should come some time this week. Looks like All I will need to do is fab up a bracket. Jim Dawson suggested that I could cut two linear slots for the four screws that the servo would use for mounting. That way I can easily adjust belt tension. Sounded like a great idea to me .


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## Karl_T (Jan 12, 2018)

Jake2465 said:


> The two pulleys and the belt have been ordered and should come some time this week. Looks like All I will need to do is fab up a bracket. Jim Dawson suggested that I could cut two linear slots for the four screws that the servo would use for mounting. That way I can easily adjust belt tension. Sounded like a great idea to me .



That's what i did. i also put a large pulley on the RT to mathc the size of the handwheel. A small one on the servo gave a 5:1 gearing gave a real torque advantage


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## chips&more (Jan 12, 2018)

Did you plan out your ratio? I would do that first. You want a ratio that gives you more whole numbers than not. Whole numbers will increase your division accuracy.


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## Jake2465 (Jan 13, 2018)

chips&more said:


> Did you plan out your ratio? I would do that first. You want a ratio that gives you more whole numbers than not. Whole numbers will increase your division accuracy.



I did .  The servo encoder gives 10000 pulses per rev and the ratio on the rotary table is 90:1. So, 10,000(90)/360 = 2500 pulses/deg.


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## Jake2465 (Jan 13, 2018)

Karl_T said:


> Suggestion. Make the three jaw chuck "adjust true" type. Being able to dial your part to have zero run out is critical on many parts.  This is not a real difficult task to add to any chuck.



That sounds like a good idea. I was thinking about how I am going to get a 6" chuck bolted to this thing and I realized that just making an adapter will not give me any adjustability. It will get me close, but the arrangement of the T-slots will not really work for trueing up the chuck. Being able to match centerlines between the chuck and the rotary table would be very convenient. If it was a case of only being a few thousanths off, then I would probably not sweat it, but I feel that I could be .010-.030 off, and that would be too much. Also, having a chuck that runs on a lathe that is not dead true is not that big of a deal if the bar can be turned first and left in the chuck for all the work. I won't have that option on the mill. The chuck will have to be accurate enough to get me there on it's own.


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## JimDawson (Jan 13, 2018)

Jake2465 said:


> I did .  The servo encoder gives 10000 pulses per rev and the ratio on the rotary table is 90:1. So, 10,000(90)/360 = 2500 pulses/deg.



What pulley ratio did you order?


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## Jake2465 (Jan 13, 2018)

JimDawson said:


> What pulley ratio did you order?


1:1


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## Jake2465 (Jan 13, 2018)

JimDawson said:


> What pulley ratio did you order?



Looks like this rotary table has around 5 to 7 minutes of backlash depending on where it's at in the rotation.


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## JimDawson (Jan 13, 2018)

You might be able to ''wear'' it in after you get the motor hung on it.  That's what I did with mine.  Just ran it as I over tightened the worm until I was able to get zero backlash.

Have you pulled the worm cam assembley out yet and looked at the thrust bearings?


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## Jake2465 (Jan 13, 2018)

JimDawson said:


> You might be able to ''wear'' it in after you get the motor hung on it.  That's what I did with mine.  Just ran it as I over tightened the worm until I was able to get zero backlash.
> 
> Have you pulled the worm cam assembley out yet and looked at the thrust bearings?



I have not pulled the assembly out yet. Is it as simple as just rotating the cam down and getting my rubber mallet and giving it a couple good bops to knock the assembly out of there?


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## JimDawson (Jan 13, 2018)

There should be a set screw that runs in a slot in the cam ''can''.  Remove that screw, disengage the worm the the gear, and pull the assembly out from the handle end.  There may also be an end plate or something that prevents axial movement.  That will have to be removed if it exists.


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## Jake2465 (Jan 13, 2018)

JimDawson said:


> There should be a set screw that runs in a slot in the cam ''can''.  Remove that screw, disengage the worm the the gear, and pull the assembly out from the handle end.  There may also be an end plate or something that prevents axial movement.  That will have to be removed if it exists.



I may be going back over there today. If I do, I will try to get the worm assembly out and post some pictures.


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## Jake2465 (Jan 16, 2018)

The two pulleys and the belt are supposed to come in the mail tomorrow.


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## Jake2465 (Jan 19, 2018)

The belt and the pulleys finally came in. Here is the design for the bracket. Pretty straight forward.


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## Jake2465 (Jan 22, 2018)

Started making chips!


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## Jake2465 (Jan 22, 2018)

Some more chips!


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## Jake2465 (Jan 22, 2018)

Jake2465 said:


> Some more chips!



My machine is running a software controller provided by Jim Dawson. His software is also 4th axis capable, so I intend to try that capability out with this build.


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## Jake2465 (Jan 23, 2018)

Working the backside.


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## Jake2465 (Jan 23, 2018)

Jake2465 said:


> Working the backside.


Cleaned up.


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## Jake2465 (Jan 25, 2018)

4th axis pretty much finished up. I still have to run it in and put it under some machining stress to see if the setup will actually hold. The next project will be making a mounting plate for the 4th axis so I can actually mount it at mid-point on the Y-axis travel.

Here are some things I learned doing this project:

1) It's probably best to use a 4 jaw chuck when boring holes in things that require a set amount of tension or backlash like pulleys and gears. when I rotate the shaft of the 4th axis, I can push down on the belt and notice that a few spots have more tension. Fortunately it is not enough to cause extra drag in those spots, but If I was off anymore, I probably would have been taking a one way trip to destination screwed.

2) incorporating some kind of tightening mechanism would have been a big help. Pulling on the servo to get the belt tight while trying to hold an Allen wrench in the hex socket hole and drive my electric impact gun from the other side is not fun.

Overall, I am happy with the results.


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## JimDawson (Jan 25, 2018)

Looking good !


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## Jake2465 (Jan 27, 2018)

A short video:


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## Jake2465 (Jan 27, 2018)

I need to bump up the acceleration a little bit. It uses about 90deg of rotation to get up to speed.


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## JimDawson (Jan 28, 2018)

Jake2465 said:


> I need to bump up the acceleration a little bit. It uses about 90deg of rotation to get up to speed.


 
Parameters 4.3 and 4.4


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## Firestopper (Jan 28, 2018)

What a cool project, nice work!. I can see a 3-D printed belt cover in your future or perhaps a Kydex formed that could screw onto the edge of your base plate.
Very cool indeed, thank for sharing.
Paco


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## Jake2465 (Jan 28, 2018)

firestopper said:


> What a cool project, nice work!. I can see a 3-D printed belt cover in your future or perhaps a Kydex formed that could screw onto the edge of your base plate.
> Very cool indeed, thank for sharing.
> Paco



You know, I always keep forgetting that 3D printers are another option . I was looking at that belt yesterday and thinking "Ya know, I should really put some kind of guard on that thing so oil and chips don't get lodged in the cogs". I was thinking about machining some kind of aluminum guard or something like that, but It would be a pretty good waste of a bar of aluminum just to cover up the works. On the other hand, possibly 3D printing a plastic guard or even just making a sheet aluminum guard that is held together with rivets may be another option. Also, I could make a foam core molded fiberglass guard as well...Hmmm, perhaps that would be the ticket since I don't have a 3D printer. I can just hack and sand a piece of Styrofoam with the came shape of the aluminum bracket and just do a layup on the foam directly. After it dries, I can remove the foam.


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## Jake2465 (Jan 28, 2018)

Here is a part I will likely test with the 4th axis once I get a chuck mounted on it. It's 2" OD and 3" length.


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## Jake2465 (Feb 9, 2018)

Here is a video of the mill working with the 4th axis to produce what would be a face op on an eight sided part.


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## Jake2465 (Feb 9, 2018)

The 6" chuck came in. Tomorrow I plan to machine out the adapter base for the 4th axis so it can be bolted down to the center T-slot on the mill table. Also, I need to machine out four special T-slots for the 4th axis face so the chuck can be adjusted to be as concentric as possible.


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## Jake2465 (Feb 10, 2018)

Here is what I managed to accomplish today.


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## Jake2465 (Feb 10, 2018)

Making the special t slot nuts.


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## Jake2465 (Feb 10, 2018)

Milling the other side.


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## Jake2465 (Feb 10, 2018)

One piece down.


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## Jake2465 (Feb 12, 2018)

I finally finished up all of the T-nuts. The last part will be the back plate. It is partially machined out. Once it is mounted up to the face of the 4th axis, I should have up to .075" adjustability.


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## Jake2465 (Feb 14, 2018)

And here is the finished 4th axis .


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## Jake2465 (Feb 14, 2018)

A test part. It works great!


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## JimDawson (Feb 15, 2018)

I love it when something actually works.


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