Replacement Z-Axis Servo Motor, IH CNC Mill

Unfortunately, during gib adjustment on the Z-Axis of my IH CNC Conversion Mill I locked up the Z-Axis and burned out the servo motor. I contacted Charter Oak Automation and Paul was very helpful in trying to find a "stock" replacement servo motor, which are no longer in production and none could be located. Paul suggested I replace my IH CNC Z-Axis servo motor setup with the new Charter Oak Z-Axis installation. The new Charter Oak Z-Axis setup has the servo motor mounted upward (the opposite of the old IH CNC setup) and unfortunately the ceiling in my workshop is too low to accommodate the new Charter Oak Z-Axis setup.

After searching the Internet, I found the HomeShopCNC website where they sell a Nema-34 Servo Motor (850 oz-in peak torque, 72v DC brushed motor, without encoder) for $159. I bought one and when it arrived, I discovered it was approximately 0.3 inches larger in diameter than the original IH CNC servo motor. I enlarged the Z-Axis IH CNC Nema-34 stock spacer along with the stock motor bracket using my Taig CNC Mill. Additionally, I had to make an additional 3/16 inch thick spacer to correct for a slightly shorter servo motor shaft. https://grabcad.com/library/nema-34-motor-spacer-1

The new servo motor has been installed and operates flawlessly so far.

Attachment 247190

Thanks for heads up. After reading your post I purchased similar motor from Automation Technologies (KL34-180-72 @ 1125 oz/in). I did not like original IH mounting method (load from top but mounted on bottom), so I relocated motor to top by cutting a rectangular hole in top plate of mill to allow motor through to mount on 3/16" plate attached to bottom of that plate via slotted screw holes in the plate. I can adjust belt tension via sliding plate. Motor is fully exposed for heat radiation (an ongoing concern of mine). I am happy with outcome, and I am eager to finish up and get back to milling!

Good solution . . . I really like the 850 oz-in motor as it powers the mill head up/down smoothly. Can you post a picture of your installation so others can copy your solution?

The power of my new motor provides a night and day difference compared to the original motor. The original motor struggled but worked, the new motor works without any audible signs of struggle. I have amp gauges coming, and I will install them on all the drives to monitor future issues before they burn up motors. I think that the original motors were marginally qualified: I burned up the x-axis motor when the mill was new (replaced immediately without cost by Gino) and I noticed the original servo was rated at 60v (Pittman/Ametek 14000 series), but the dc power to the drives is 76v. However, I recently lucked upon two, what appear to be new (untested sold as parts but still with original tinned wired connections), gear-motor drives on ebay with 76.4v rated motors that look identical to the servos on my x-y, so I bought those and I hopefully now have properly rated spares for my x and y on the way. I will purchase another KL34 for the z-axis now that I know it performs well for that axis.

I struggled yesterday to attach photos directly via my smartphone, but I gave up surfing the posting dialog that is not very smartphone friendly regarding attachments. This should work better now that I am on my desktop PC...
Attachment 249762Attachment 249764Attachment 249766

Oh, and please forgive the long screws, I will shorten them eventually. All of the work was done with drill press, hacksaw, file, and elbow grease (although I did enlarge the large hole in the steel plate in the four jaw on my lathe after poking most of it out with a 2-3/4" hole saw on the drill press).

The best solutions are the ones that are simple and clean . . . you have both . . . great installation.

Hi guys,

We have plenty of the KL34-170-72's in stock and currently on sale for $129. If anyone else is looking to make this swap, we also have Z axis top plates machined and ready to ship.

Quote:

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Originally Posted by gtiworks

The best solutions are the ones that are simple and clean . . . you have both . . . great installation.

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Thanks for the kind words: I think you characterized my intent precisely. I have many hours scuba diving: KISS is a critical part of my overall philosophy to life. I am a little unhappy with the belt alignment, but that is because I obsess; the original belt alignments are no better. However, measurements I originally took show my solution to be off by 1/16" although that vertical misalignment is easily tolerated by the existing pulley and belt choices. After originally noticing the problem during layout, I decided to build it anyhow, and it turned out entirely acceptable given the belt is not on the edge of either pulley.

I'm a grumpy old codger, and I have always hated what I consider a ridiculous servo cover solution on the IH mill (bent acrylic with hose clamps???). I am currently in the process of milling end caps to replace the round spacers separating the inner and outer plates (my end caps will span the short end of each pair of plates and replace the two round spacers on those ends): my end caps will fill out the ends so that only a flat piece of lexan will be required to span the long side to cover the pulley and belt, and I'll probably just glue that window in with silicone. I'll probably make some sort of solvent welded window to avoid the larger z-axis pulley, but it will be based on a flat window for a proper perimeter seal, like the future x and y windows, but with a cutout for the pulley and a cap covering the pulley cutout solvent welded in place. My current covers are in sad shape and I am eager to repair them...

When I mill those end caps, I hope to adjust the z-axis plate spacing to adjust my existing z-axis solution so that the pulleys are precisely aligned. I will be limited by the z-axis design, so I may not get the 1/16" there, but I am comfortable with the existing solution so that shouldn't be much of an issue for me to ignore, if need be, when the time comes. I'm in the middle of real projects, so the mill cover upgrade is still on the back burner.