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Looking for Advice on Mounting Acrylic to Extrusions

Discussion in 'Other Builds' started by Ian Lee, Dec 28, 2016.

  1. Ian Lee

    Ian Lee New
    Builder

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    I cut some acrylic panels for this bot made of V-slot and mounted it them using M5 low profile screws with drop-in T-nuts. The one in the front was mounted last night and looked great before I went to bed. Today I went back out and mounted the panel on top before I noticed the panel from last night had cracks at every screw. I didn't think I over tightened them and certainly didn't tighten them to the point where they left an indent. They looked just like the screws on top. Any advice on how to properly mount acrylic to V-slot? Perhaps I should use a different plastic or just a thicker acrylic? I believe the problem is the gap between the T-nuts and the acrylic but I'm not sure what to do about it short of making (3D printing) some spacers to fill the gap.

    [​IMG]

    Thanks!
    Ian
     
  2. Jonathon Duerig

    Builder

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    The two basic paths ahead of you are either: (1) use a stronger material or (2) distribute the load more

    (1) You might want to try thicker acrylic. The thicker the acrylic is, the stronger it will be. I've had a piece of 2.5mm acrylic break off in my hand just from the weight of it and shatter on the ground. On the other hand, 6mm or thicker acrylic is pretty strong and I've used that for (light) structural applications. Or you might want to try ABS or PVC. Both of those are great to machine if you have a little CNC. Or if you have a laser cutter, you could try acetal/delrin.

    (2) Add more mounting points. Instead of mounting with single T-nuts, mount with double T-nuts and a pair of holes. Or just add more single T-nut mounting points distributed around the panel. Or use fender washers to distribute the load of each mounting point. I've also read that acrylic doesn't like to have the constant compression stress of being screwed in, especially over long periods of time. So you might be a lot more gentle. Only tighten with the short lever arm and not with the long.

    On my current build, I'm using acrylic windows while the main panel is mostly ABS. Since the acrylic spans are smaller with less weight (just a window), I can use cheap 3.2mm stuff rather than use anything thicker. But depending on your span, you may end up using some stuff that is quite thick.

    -Jonathon Duerig
     

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