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December 09, 2018, 20:35:31 pm


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Author Topic: Motor Mount  (Read 638 times)
Bob La Londe
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« on: March 22, 2018, 00:14:25 am »

This could go either way.  Member Projects or Member Machines

This is a bi-directionally adjustable Nema34 motor mount.  I used a fixed sleeve to position it to line up the lead screw and the shaft then tightened all the bolts In the adjustment slots.  Then take the motor off, swap to the flexible motor coupler, and slap the motor back on. 

I've done fixed bearings on the outboard end of lead screws the same way. 

On the KMB1 I found two things when I tore into the Y axis.  The end of the lead screw shaft was bent.  The Y-Axis servo motor was offset belt drive so the bent shaft really reeked havoc with tuning and adjusting the servo drive on that motor.  On top of that the brush holders in the motor were falling out.  I would guess that made the motor fairly weak.  Not seeing an easy fix and knowing its hard to find that exact motor at a reasonable price I decided to give direct drive with a closed loop (encoder to drive) stepper a try.  I already had the stepper and stepper controller. 

I did two things to improve the end of the lead screw.  I bent it back to the best of my ability.  Mounted it in soft jaws in my four jaw chuck, cut off the end since it no longer needed the extra length, and turned the area behind that down to the right size for the coupler.  Even if its still not perfect, being direct drive with a helical coupler will be a lot less strain on the motor than having a timing pulley either going over tight or sloppy loose for part of every rotation. 

The motor mount is three pieces, but if I had a piece 1.5x4 inch bar I could have made it as just two pieces.  It was designed and cut using CamBam. 



* Soft Jaws.jpg (257.09 KB, 1008x756 - viewed 77 times.)

* Adjustable Motor Mounts.jpg (199.63 KB, 864x864 - viewed 96 times.)
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If I have the time I'll be glad to show you a little in my shop. 

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lloydsp
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« Reply #1 on: March 22, 2018, 01:32:36 am »

ICK!  I can't even begin to fully-appreciate the impact of a bent leadscrew!  I'm having 'rate' issues on the Y-axis of  my router right now, and the X and Y axes were un-touched during my whole B-axis adventure.

I'm still trouble-shooting.  The machine would once do 300 ipm without trouble, now, over a 3000-inch-travel job, I'm losing about 0.010" in Y!

Lloy
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Bob La Londe
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« Reply #2 on: March 22, 2018, 02:35:31 am »

ICK!  I can't even begin to fully-appreciate the impact of a bent leadscrew!  I'm having 'rate' issues on the Y-axis of  my router right now, and the X and Y axes were un-touched during my whole B-axis adventure.

I'm still trouble-shooting.  The machine would once do 300 ipm without trouble, now, over a 3000-inch-travel job, I'm losing about 0.010" in Y!

Lloyd

You know that commercial, industrial, and high end semi DIY routers that size typically rapid at twice that and often 4 times that.  Ahren Johnson from CNC Router parts claims his Nema34 build kit will easily rapid at 1200IPM.  Of course it doesn't have that awesome rigid and perfectly flat vacuum table you have on that Shop Sabre. 

I tested my little Chinese noodle (rigid as a noodle) router at 600IPM and backed it off to 300 for stability since its a blatantly crappy misaligned build.  Some day I will basically replace it with all new parts as a build project, and I'll crank the speed back up.  I've got a NEMA23 closed loop stepper package set aside for that future project. 

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Getting started on CNC?  In or passing through my area?
If I have the time I'll be glad to show you a little in my shop. 

Some Stuff I Make with CamBam
http://www.CNCMOLDS.com
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