Stiffening The Long Horizontal Gantry

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EricPeterson
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Stiffening The Long Horizontal Gantry

Post by EricPeterson » Thu Jul 28, 2016 8:48 pm

I had problems with the long gantry deforming due to high belt tensions. I ran higher than standard belt tensions to handle large pieces without dropping accelerations too far.

I was advised to shim the linear way's rail. That's not the right way to go. The right way to go is to stiffen the beam bending section of the gantry assembly. I did that by adding a miniature steel structural beam, drilled and tapped with the 13 M3 holes to replace the 13 lock nuts.

Image

Works beautifully. The length of shallow channel -- installed on its side -- was only twenty or thirty bucks through McMaster-Carr. Of course I absolutely had to buy a nifty little German metric small tap and tap drill set... but the cost of tools never counts towards a repair....

jsc
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Re: Stiffening The Long Horizontal Gantry

Post by jsc » Fri Jul 29, 2016 3:46 am

but the cost of tools never counts towards a repair....
I like that. I've repaired a thing or two with 3D printed replacement parts. That means the cost of the M2 totally doesn't "count".

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jimc
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Re: Stiffening The Long Horizontal Gantry

Post by jimc » Sat Jul 30, 2016 2:41 am

thats great but that is the y gantry and not what ed and i were talking about in the other thread. x gantry is the one that is prone to flexing or bowing down in the center from belt tension. never seen anyone have that problem with the y. generally you just need to slightly shim that top rail to true it to the build plate.

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Matt_Sharkey
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Re: Stiffening The Long Horizontal Gantry

Post by Matt_Sharkey » Sat Jul 30, 2016 3:47 pm

Hey jimc, Would you mind throwing together a small guide on how to properly shim the x rail? I could guess at how to do it, but would likely mess it up, having supporting resources would be great. some info that would be helpful could be:

Links to any purchases necessary (tools and consumables)
Steps to take first like measurements.
how to actually shim the rail.
any troubleshooting and maintenance.

Yeah I know that what I'm asking for comes off as hand-holding but, well, I think I need my hand held on this one.

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jimc
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Re: Stiffening The Long Horizontal Gantry

Post by jimc » Sun Jul 31, 2016 12:25 am

well, if your bed is say .01mm too tight in the middle which would make you think that the bed is bowed up in the center..... which is usually the case. loosen the rail and add .01mm worth of shim stock under the rail in the center and tighten it back down. get some you can buy brass shim stock in all thicknesses at mcmaster for a few bucks.

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Matt_Sharkey
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Re: Stiffening The Long Horizontal Gantry

Post by Matt_Sharkey » Sun Jul 31, 2016 6:13 pm

well that seems pretty easy...

EricPeterson
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Re: Stiffening The Long Horizontal Gantry

Post by EricPeterson » Tue Aug 16, 2016 7:41 pm

jimc wrote:thats great but that is the y gantry and not what ed and i were talking about in the other thread. x gantry is the one that is prone to flexing or bowing down in the center from belt tension. never seen anyone have that problem with the y. generally you just need to slightly shim that top rail to true it to the build plate.
Nevertheless jimc, you were correct and it was a deformation under belt tensioning issue and not a deformation in the heated plate, which I had suspected. I do not have an issue with the crossfeed -- no deformation that way and a nice, constant gap adjustment.

This fixed the uneven gap in the long travel direction, which was much tighter at the ends than in the center.

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jimc
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Re: Stiffening The Long Horizontal Gantry

Post by jimc » Wed Aug 17, 2016 4:30 am

glad you got her all straightened out

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