4th Axis Conversion

[Jim Dawson]

I did some horse trading for this 6 inch Vertex super spacer, about $80 in materials, and a couple hours labor But it was missing something....I still had to turn the handle and I couldn't hook it to the computer. But.....I can fix that.



With the handle removed, it looks like that is a perfect place to put a pulley.



So, make a little box to house the belt and mount the NEMA 23 Stepper.


Finishing the cover



The finished housing, motor side. It just clamps onto the Vertex housing.



And in position




The belt installed, 2:1 reduction



With the cover installed. I did not want to modify the Vertex at all so I left the shaft intact. The original handle will still fit with the motor on.



So I made a cover that just screws into the housing.



It still allows vertical or horizontal operation by rotating the motor housing around the mount.



It worked perfectly....well almost

The thrust ''bearing'' on the outboard end of the worm shaft was a wave washer rubbing on cast iron. Not the best system, and it started seizing on me. It needs a real thrust bearing but a 15 x 21 x 4 mm thrust bearing proved to be nonexistent. No problem.....Just because ‘’they’’ don’t make a 15 x 21 x 4 mm thrust bearing, doesn’t mean that one can’t be made. All it takes is two grade 8 washers, a bronze washer, and some 2mm bearing balls. Ok the grade 8 washers ain’t bearing steel, but close enough for this application. A little operation under load will work harden the surface and they’ll last quite a while.



A little surgery on the parts and instant (almost) thrust bearings.



Loading the bearings



The cam housing with the the thrust bearing in the new pocket.



The worm shaft and cam housing with the new thrust bearings.



Running in the new thrust bearings. Over tighten a bit, run for awhile, rinse repeat until I'm happy with the way it feels. Then adjust to the proper preload.



And the finished product



3.6 million steps per revolution or 10,000 steps per degree. Adjustable to zero backlash. A little more time to install the new stepper driver in the cabinet, then a few program modifications and the new 4th axis is alive.

After a few mods to a Grizzly tailstock it's set up.



The first test cut !



This is what the screen looks like. The Z and R(otary) axis are turned off on this pic.



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[asuratman]

Very good job... nice 4th axis rotary
How do you program mach3 to put K and R on the screen?

[Jim Dawson]

Very good job... nice 4th axis rotary
How do you program mach3 to put K and R on the screen?

Thank you for the kind words.

That is not Mach3. That is my own software, I wrote it. Dawson Controls CNC (DC_CNC) http://www.cnczone.com/forums/knee-v...ml#post1977928

I think there is some kind of screen builder app for Mach3 that allows you to add to the DRO

[asuratman]

So, you are software developer. Do you have website about this software? Do you also develop any hardware such as motion controller for ethernet, BOB, etc.?

[Jim Dawson]

So, you are software developer. Do you have website about this software? Do you also develop any hardware such as motion controller for ethernet, BOB, etc.?

Yes, I've been writing industrial software for about 25 years. My website is Dawson Controls

I have done some hardware interfaces for special applications, but normally I use Galil Motion Control products. Their controllers work with Ethernet, USB, or Serial. They also have PCI bus products.

[Scot808]

I know this is an old thread but wondering how you were able to adjust out all the backlash? And, the method you used, is it applicable to all/most rotary tables?

[Jim Dawson]

Great question! I started out with a good quality (Vertex) super spacer. Then I just cranked down the worm engagement adjustment until there was no measurable backlash in the worm gear/worm wheel system, the preload on the thrust bearings that I installed helped also, took all of the possible end play out of the worm gear shaft. I do have to say that forcing the worm engagement is not the best for long worm life, but I keep it well lubricated with a good hypoid gear lube, and in my case the 4th axis does not see a lot of use.

As far as I know, all rotary tables have a method to adjust the worm engagement. I would say that this is possible to do with most rotary tables and spacers as long as the worm & worm wheel are reasonably concentric.

[bryanbdp]

.

[Jim Dawson]

Thank you.

I just zero manually by indicating the part in if needed, then zero the DRO. If starting with raw stock, then just put the stock in the chuck and zero the DRO, that becomes zero for the duration of the job.

It would be possible to use a homing switch, but not sure how well that would work, nor can I really see a need for it.