Tramming issues

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aarvidsson
Posts: 150
Joined: Sat Aug 03, 2013 4:46 pm
Location: Frosty Sweden

Tramming issues

Post by aarvidsson » Sun May 22, 2016 4:17 pm

I've got a 750mm (X) and 1000mm (Y) ShapeOko 2 that's bolted directly to a table. In between I've got a 750x550mm MDF spoil board with a gazillion T-nuts in for workholding. I've squared the machine and tightened everything down, and I've trammed the spoilboard so everything is exactly flat and relative to everything else. For the first few days I am only about a tenth of a millimeter off Z anywhere on the spoilboard, but then it starts to become funky. Over time (and sometimes as little as two weeks), I get rather big variations in Z (0,5-1 mm). As far as I can see nothing has shifted in the machine which makes me think that the MDF and/or table in itself shifts with humidity or from having things placed on the spoilboard. Does this sound plausible, or am I looking at something else?

I am contemplating going for an all aluminium bed (and maybe bolting the machine to the bed, haven't decided on the relative merits just yet), something that would cure the abovementionend issues. Anyone gone that route and care to share some advice?
ShapeOko 2 #4143

WillAdams
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Location: Pennsylvania --- south of the Turnpike, East of US-15
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Re: Tramming issues

Post by WillAdams » Sun May 22, 2016 11:16 pm

I put an HDPE spoil board on top of my MDF Wasteboard — seemed a reasonable option.
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets

DRobs86
Posts: 148
Joined: Fri Jun 05, 2015 4:19 am

Re: Tramming issues

Post by DRobs86 » Mon May 23, 2016 11:42 am

What kind of temp and humidity swings might you experience in that two seek period? Are you sure the mdf hasnt just permanently warped?

aarvidsson
Posts: 150
Joined: Sat Aug 03, 2013 4:46 pm
Location: Frosty Sweden

Re: Tramming issues

Post by aarvidsson » Tue May 24, 2016 7:47 pm

No, I'm not sure at all, I'm afraid. I had the great idea that by bolting the MDF to the table the warping issues would lessen or go away, but maybe that's it. The surface is not uniformly bent but varies both up and down all over, so warping might be the issue. The humidity has been between 10% and 50%, give or take. Maybe I should go for a dead material instead...
ShapeOko 2 #4143

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