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  #1  
Old Thu 20 October 2011, 03:15
Tonys
Just call me: Tony
 
Suffolk
United Kingdom
Backlash

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.
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  #2  
Old Thu 20 October 2011, 04:43
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
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 ?
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  #3  
Old Thu 20 October 2011, 10:54
Tonys
Just call me: Tony
 
Suffolk
United Kingdom
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.
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  #4  
Old Thu 20 October 2011, 10:56
Tonys
Just call me: Tony
 
Suffolk
United Kingdom
Sorry fogot the pics
Attached Images
File Type: jpg IMG-20111020-00047.jpg (61.7 KB, 303 views)
File Type: jpg IMG-20111020-00048.jpg (59.5 KB, 303 views)
File Type: jpg IMG-20111020-00049.jpg (58.8 KB, 302 views)
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  #5  
Old Thu 20 October 2011, 11:04
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
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?
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  #6  
Old Thu 20 October 2011, 11:07
danilom
Just call me: Danilo #64
 
Novi Sad
Serbia
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.
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  #7  
Old Thu 20 October 2011, 12:21
Tonys
Just call me: Tony
 
Suffolk
United Kingdom
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.
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  #8  
Old Thu 20 October 2011, 13:46
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Tony, I have been there.....more than once.
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