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4th Axis Build

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JimDawson

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#1
A few months ago I picked up an unused 6 inch Vertex Super Spacer almost free. Cost me about $80 in materials and a couple hours labor. :)

IMG_0658.jpg

But this is about powering it up.

The job that I got it for finally is ready to go so now I need the 4th axis on my machine. The goal here is to install the stepper drive without modifying the original hardware. What I came up with is clamping the assembly onto the cam support shaft. That way I can just remove it and am back to normal operation.

IMG_0660.jpg

The concept drawing

RT Power.jpg


So first operation is to square up the 1x4 aluminum. Then drill the cap screw holes in the housing. This is so can bolt the cap in place later without disturbing the setup when ready for that operation. These are just drilled for tap size, but will be tapped later.

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Then drill the cap and counter bore to depth for the cap screws. The depth of the counter bores are set so that in subsequent operations, the end mill will not hit the cap screws.

IMG_0632.jpg

The first operation was to cut the pocket for the cap, once that was done, then the holes were tapped and the cap bolted into place. Then the various pocketing operation were done on the entire motor side.

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And the completed motor side operations

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And the pocketing is complete on the belt side.

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The pocketing is complete on the belt cover. Tapping the 1 inch -32 hole for the shaft cover. Why did I use a 1-32? Because I had a tap for that, it’s a standard C-mount lens size. Here I’m using a 3/8 tap as the center point to keep the tap on center. Keep down pressure on the quill while turning the tap. (the quill is vertical, I was just holding the camera at an angle)

IMG_0644.jpg

And the almost completed pieces. Now the outside profile needs to be done.

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Setting the zero to the center of the T-slot, I just use a ½ inch cap screw in the chuck to get pretty close. Does not need to be dead on.

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First anchor one side of the motor mount down to the table with a chunk of MDF board under.

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Now indicate the side to align it to the table. I used the Blake because it will be used in the next operation.

IMG_0649.jpg

Next is locate the clamp hole. All of the features are relative to this location. This is located at -6.115,-2.000

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Now bolt down the belt cover. I am using a feeler gauge under the bolt to make sure it does not bottom in the T-slot.

IMG_0651.jpg

I had to change to washers under the bolt rather than the clamp. The collet nose would have hit the clamp. There is a thread on H-M about using a mill as a band saw, well that’s kinda what I am doing here. I could have trimmed these on the band saw, but I got lazy, just press go and come back when it’s done.

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Getting close

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Corner rounding the edge with a Harbor Freight carbide router bit.

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The motor mount ready to ready to install

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And the motor is mounted

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The trained monkeys pulled the wrong pulley for the 3/8 wide belt order, so I just pulled the front flange off. :mad: The belt won’t come off, the bottom flange will hold it.

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And the belt and pulleys installed.

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Has a bit of a snout sticking out, need to cover that. A handle can be installed for hand operation with the motor installed.

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I made the shaft cover from 1.125 aluminum bar stock. Since the thread length is only 3/8 inch and it’s to a shoulder, I turned the tool up side down and ran the lathe backwards. I did the threading at 460 RPM. Made nice threads.

IMG_0668.jpg

Fits nice but maybe it’s a bit long. We can call it Pinocchio:adore:

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Corner rounding on the lathe, another HF carbide router bit. Work back & forth between the edges, don’t try to take a full width cut, it’s not stable enough.

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The face wasn’t planned, but its kind of cute.:grin:

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The assembly can be used both horizontally as well as vertical just by loosening the cap screws and rotating around.

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Next is to install the drive and then write the software. That may get done tomorrow. I'll post pictures of it actually being used pretty quick.
.
.
 
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JimDawson

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#6
Just an update, I now have it running under computer control. G-code control to follow soon. 3,600,000 steps per 360 degrees of rotation or 10000 steps per degree. Way too fine resolution to be really useful, but it's kinda cool. At max speed, the table rotates at 80 degrees per second.
 
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JimDawson

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#7
Thank you all for the kind words.:) I hope you all enjoy these projects, and more importantly are able to take away something useful to you.

Other than the obvious bragging about my creations :rolleyes:, I post these threads showing not only the what but also the why I did something the way I did. I also try to show work holding, tool use, order of operation and overall process. Where appropriate, I will also post the stuff that didn't work so others don't make the same mistakes.

If a project has more than a couple of operations, I will ''machine'' the entire project in my head prior to ever making a chip. Sometimes It's back to the drawing board because something is too difficult to machine, or will have conflicting operations. This is especially important when doing CNC work.

Hopefully I can also pass on some of how to think through a problem and find a solution that both works and won't break the bank in execution. Problem solving is a learned skill IMHO, and I hope some can gain some insight into my approach. This is not to say that the way I do things is the best or ''correct'' way, but rather just to illustrate how I did it with what I have to work with.
 

JimDawson

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#9
IT'S ALIVE!!! Not too bad, I designed the drive last Sunday, ordered the parts on Monday, and am making chips with it on Saturday.

I made the first test cut tonight. It came out OK, but I need to work on the feed speeds a bit and smooth out the programming. I'm still learning how to use it

Sorry for the crappy video quality. I see now that I should have moved the camera closer in, not used so much zoom, and used better lighting..

I ordered a Grizzly tailstock and a carbide tipped center for it. I knew the tailstock was going to be a bit tall, but I wanted the heaver unit. I also found out that the keyslot in the bottom is not square to the face, about 0.040 off over the length. :burned up: No problem, I figured out a quick work around.!

This is the lowest position of the tailstock with out modification. About 1/4 inch too high.

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The slide slot needed to be a bit longer, so I went another 0.375 more. Mounted to the angle plate. This may be the first picture you have ever seen of my mill when it wasn't buried in aluminum chips.:grin:

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Here is how I supported the other end
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And the setup.

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Oh, almost forgot, here is a screen shot of the new screen with the rotary axis installed.
ScreenShop.jpg
 
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wrmiller

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#10
Very nice. I have no idea what I'd do with that screen...where's the GO button? :)
 

JimDawson

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#12
All is not well with the 4th axis. :( It turns out that this Vertex RT was designed for hand operation, surprise:eek: The hand wheel on it may have been a clue:rolleyes: The worm shaft/housing doesn't like operating at high speeds, maybe up to 1200 RPM. The radial bearing is fine, but the axial thrust setup is not up to the task. It started seizing on me. Normally I would just buy some thrust bearings, but in this case it requires a 15mm ID and max OD of 21mm. These bearings don't exist as a stock item in any configuration that I can find.......yet ......I would even side load a standard ball bearing if I could find one that size.

So....I get to design a thrust setup that will work. Not exactly sure how I'm going to do it just yet, but I'll come up with an idea. :eagerness: Back to the drawing board :faint:

EDIT: a 6702 ball bearing is 15x21x4 mm, that size is usable, but no thrust bearing in that size.
 
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countryguy

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#13
Thanks for all those great tips and tricks Jim! HF carbie corner rounding bit. I'm chucking the ball mil I was trying to play w. :) and the stud post stand you made... Way easy to remember that one! Love the great pics and teaching you do Jim! Thanks as always.
JJ
 

JimDawson

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#14
OK, Inbound a package of 2mm bearing balls, and a pack of 0.599 ID hardened washers to make the bearing plates out of. I'll make my own thrust bearings. I'll post that build when I get the parts.
 

JimDawson

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#15
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.

upload_2015-12-8_22-42-43.png

It turns out that a 9/16 SAE washer is exactly the correct ID to fit a15mm shaft, but the OD is more like 28mm, no problem, that’s what lathes are for. First I turned a stub arbor the size of the washer ID, and threaded the end for a bolt.

I made the stub just long enough to be just a little shorter than a stack of 4 washers so the bolt would clamp them to the arbor. Then turn the OD concentric to the ID. Once that was completed the bronze washers’ also needed to be turned. This meant turning the stub arbor to match the ID of the bronze washers, and also shortening the stub to match the stack length of the 2 bronze washers. I make stub arbors for a lot of work that needs to be concentric, simple and cheap.

upload_2015-12-8_22-43-1.png

OD’s turned to size, 21mm. The ID of the bronze washers is still original. That will be fixed in the next operation on the mill.

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First operation is to machine a 21mm pocket in a 5C emergency collet. I could have done this on the lathe, but it is just as easy on the mill. For those of you who have not heard of an emergency collet, these are made to be machined as needed, and are available in soft steel, brass, and nylon that I know of. I normally keep a couple around for projects. You pull the collet into the chuck and do your machining, then remove the 3 dowel pins to use.

upload_2015-12-8_22-43-42.png

Once the collet was pocketed, then I machined the four grade 8 washers to 0.049 thick with the same setup I used for pocketing the collet, just changed the height..

Then it is time to put the bearing track in the washers. For this I used a 0.078 ball end mill, and went 0.010 deep in 2 passes.
upload_2015-12-8_22-44-2.png

Next was to make the bearing cages out of the bronze washers. First they had to be machined to 0.039 thick using the same setup as above, and the ID also needed to be pocketed to 15.1 mm.

Then machine the 16 bearing pockets, 0.079 dia, using a 0.077 end mill and running a pocket routine.
upload_2015-12-8_22-45-55.png

And the finished races and cages.

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Hopefully I will get the ball bearings tomorrow.
.
.
 
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ch2co

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#16
Jim
I sure hope that you are enjoying doing this project a I am watching it.

CHuck the grumpy old guy
 

RJSakowski

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#19
Jim, you are a machinist's machinist. If you can't buy something, you make it. If it doesn't exist you design it. A great job. I am looking forward to seeing the completed project.

Bob
 

JimDawson

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#20
Jim, you are a machinist's machinist. If you can't buy something, you make it. If it doesn't exist you design it. A great job. I am looking forward to seeing the completed project.

Bob
You're making me blush, Bob. Thank you!
 

RJSakowski

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#21
I took a look at my Tormach 6" RT. It is a motorized Phase II as near as I can tell. I see no evidence of a thrust bearing in the parts diagram.

I have never put it through its paces and now you have me wondering if there may be a problem there as well.
 

JimDawson

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#22
Bob, yours may be designed as a motorized table from the get go. My Vertex has an odd arrangement, one end of the shaft is a hardened steel boss contacting on end of the cast iron sleeve. Actually that is a pretty good bearing. The other end consists of a threaded collar and a wave washer to set the end preload. The wave washer is captured between the collar and the cast iron sleeve and acts as the bearing. In this case a wave washer does not make a good bearing, it was starting to gall a bit. It could have been a lack of lubrication, but it's not a good system for high rotational speeds.

EDIT: I looked at the Tormach documents, their super spacer is a Vertex or a clone. It is built identical to mine. The exploded view is incorrect, it shows the sleeve (item 29) in the wrong assembly order, but item 27 is the wave washer in mine, what they are calling a spacer in the parts list. I don't know about your RT, but I could see a problem with their super spacer.
 
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JimDawson

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#23
The final step in the process is to pocket the cast iron sleeve for the thrust bearings. The worm shaft must be maintained in the same position as original so the sleeve needs to be pocketed to the thickness of the thrust bearing.

This is the original assembly. The boss just to the right of the worm gear contacted the end of the sleeve as the bearing, and on the other end the ‘’bearing’’ surface is the wave washer that was in contact with the other end of the sleeve. Probably OK for hand operation, but not adequate for powered operation.

upload_2015-12-10_16-46-0.png

Here is the assembly with the new thrust bearings, less the balls. Where is UPS?????:cautious:

upload_2015-12-10_16-46-19.png

The sleeve setup and ready for pocketing on the worm gear end. The sleeve is held in a round pocket I already had machined into the vice soft jaws for another project. Soft jaws are really handy to have around and easy to make. They allow all kinds of quick fixturing for lots of projects. I normally just leave them in place and use them just like hard jaws until I need to change them because I have modified them to the point they are no longer useful for anything. Just waiting on the bearings to arrive, where’s UPS????????:confused:

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UPS finally got here!!!!:)
One bearing with the balls loaded and greased up.

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After assembling the bearings, I measured the thickness and found that rather than 4mm they were 4.35 mm, so the pocket needs to be 0.171 deep.

Pocketing the worm gear end of the sleeve

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And the bearing in place.

upload_2015-12-10_16-48-39.png

And pocketing the other end

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Running in the assembly. This consisted of over tightening the nut and running until the bearings got warm, rest a while, tighten a bit more, run again, rinse repeat until I’m happy with the way it feels. Then back off the nut and bring it back up to what I felt was a proper torque on a 6 inch crescent wrench. With the balls at about a RC62 and the races at about a RC35 hardness this exercise conformed the ball tracks to the balls for a nice fitup. The thickness of the thrust bearing probably changed a bit during the run in operation, but it will be close enough.

upload_2015-12-10_16-49-12.png


And reassembled. I ran it for about a half hour and it’s nice and smooth, with none of the problems that I experienced before the thrust bearing mod. Before I could easily stop the chuck with my hand and stall the motor. Now I am not able to stall it at all.:) I’m going to call this a success.:grin: :encourage: Now I can get on with my other projects!

upload_2015-12-10_16-49-44.png
 

ch2co

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#24
Jim
Beautiful and well executed again. You da man. I've made nylon thrust washers before, but thrust ball bearings? WOW!

CHuck the grumpy old guy.
 

JimDawson

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#27
Matt, I would say it might be possible to make a helical gear on this setup. Trivial is not the word I would use:) Just thinking about the g-code makes my head hurt. However I did cut a helix as a test when setting up.
 

mattthemuppet2

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#28
yeah, perhaps I bandied the word trivial around a bit too much there :D CNC can appear simple to those who know nothing about it, like magic!
 

middle.road

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#29
Matt, I would say it might be possible to make a helical gear on this setup. Trivial is not the word I would use:) Just thinking about the g-code makes my head hurt. However I did cut a helix as a test when setting up.
All you have to do is hold the drawing up in front of the monitor on said machine and it'll program itself - won't it? :grin:
I have actually 'endured' people who believed that with all their hearts and minds.
Computers are a great tool, but some still require programming time...
 

FOMOGO

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#30
Just read your post. You do amazing work. Thanks so much for posting and passing on all the great info there in. Mike
 
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