MechMate CNC Router Forum

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-   -   Backlash (

Tonys Thu 20 October 2011 02:15

I have the PK296AE SG7.2 on my machine with mod1 rack and 30tooth pinion. I broached the pinions to take a key way and used two set screws at 90 deg to fix to the shaft. With everything switched on i.e. motors under holding torque I can get ,measured with a dial indicator, up to 1.1 mm movement on the Y car by physically rocking back and forth-about (.5 mm in both directions.)
I wondered if any one has done tests on backlash, and if this is an acceptable level?
I am just starting with the Mechmate so learning curve very steep.

Gerald D Thu 20 October 2011 03:43

1.1mm is way too much! Can you show a pic of where the dial gauge is located and where you apply the 0.5mm rocking ?

Tonys Thu 20 October 2011 09:54

Sorry about quality but here are pictures of the set up I used. The DI shows 0.5mm movement each way with a single handed push and shove! If you think this is an appropriate way to test I will test the other axis. I am not engineer so any guidance or advice would be appreciated.

Tonys Thu 20 October 2011 09:56

3 Attachment(s)
Sorry fogot the pics

Gerald D Thu 20 October 2011 10:04

Tony, 1.1 or 0.5mm for that setup is something very big and you should see the cause of it easily with the naked eye (without a dial gauge). Are you sure that you are not measuring 0.11 and 0.05mm) a factor 10 less?

danilom Thu 20 October 2011 10:07

I dont see spring on the Z motor, do you have it on other motors? if you just pushed the motors to the rack and bolted then you could experience some backlash.

Tonys Thu 20 October 2011 11:21

Gerald, you are absolutely right. I could say age and poor eye sight are to blame but more likely a non engineer trying to use proper engineering tools! Thanks

Danilon, yes springs on all motors Gerald got it in one.

Gerald D Thu 20 October 2011 12:46

Tony, I have been there.....more than once. ;)

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