shapeoko losing calibration ?

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cmdrrimmer
Posts: 12
Joined: Wed Aug 08, 2012 7:31 pm

shapeoko losing calibration ?

Post by cmdrrimmer » Sat Jul 26, 2014 1:15 pm

Hi all.

I recently started cutting pieces where precision mattered and discovered I had to adjust the steps per mm for x and y axis.

I cut a 50mm square and it came out 53mm....ok no problem adjusted the steps per mm.....recut it came out 50mm.

My issue is a few days later I ran a job and its cutting too big again.

I couldn't remember what I changed the steps per mm to so I'm not positive the grblshield lost the settings but I've read it should maintain them.

Could it be as simple as temperature and humidity being dfferent ?

Belts keep stretching inelastically ?

Thanks

Andy

Camel
Posts: 15
Joined: Tue Mar 04, 2014 11:07 pm

Re: shapeoko losing calibration ?

Post by Camel » Sat Jul 26, 2014 2:26 pm

Something similar happened to me. In my case it turned out that the steppers were missing steps. It wasn't obvious until I started really tuning my machine down to the fraction of a fraction of an inch.

WillAdams
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Joined: Mon Apr 09, 2012 6:11 pm
Location: Pennsylvania --- south of the Turnpike, East of US-15
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Re: shapeoko losing calibration ?

Post by WillAdams » Sun Jul 27, 2014 12:59 am

The belts stretch too, but missing steps is the biggest threat to accuracy/precision.

Temperature may slightly affect the belts --- once direct sunlight warming up the zip ties I was using for belt anchors caused them to come lose one after another. It will also cause a very slight expansion in size of the machine, which may come into play on long operations.
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets
Nomad 883 Pro #596 (bamboo)

cmdrrimmer
Posts: 12
Joined: Wed Aug 08, 2012 7:31 pm

Re: shapeoko losing calibration ?

Post by cmdrrimmer » Sun Jul 27, 2014 4:12 am

I think i've sorted this out. I believe I've been adjusting the steps/mm the wrong way....I was increasing the steps/mm when it was moving too far.....I think I had a bad set of grblcode from inkscape/makercam that made me think increaseing the steps/mm made it move less....when it seems clear the opposite is true.

I went to basics...reset the steps/mm to 40.20 , ordered a few x/y moves of 3 inches using a 1-2-3 block to judge what actually happened...but this time i increased the steps/mm only because it was moving too little. I seem to have it dialed in pretty close now by eye with a steel ruler......once i get my dial gauge in the mail i'll fine tune it more.

Thx for the replies.

Andy

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