Build #2: Going bigger - How does this torsion box look so far?

Mostly Printed CNC - MPCNC Troubleshooting
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I’ll be using the 525-23.5 build, everything printed in PETG this time instead of PLA, with a working area of 2’ by 6’ for sign making. On a 4’x8’ sheet, this gives me about 13 inches in both dimensions for power supply, RAMPS, laptop, tool cases… I finally got real RS bearings instead of those heavy-grease 608-ZZ’s, so I should be able to print in colder weather. I’ll probably support the long spans at three positions, about every 20 inches.

So, to the table: The option of hoisting it to the ceiling to free up space is appealing, so I need a torsion box to keep the surface rigid. Although unfinished, is there enough cross-support here, or should I add another set in the short (4’) direction?

The material is 1/4" OSB, because it’s cheap and so am I, but I will be topping it with a good MDF spoil board.

More questions to come, I bet…

Thanks Ryan and all!

–Matt

Torsion-box.jpg
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The major problem will be rigidity in the long access. To have a 6’ working area your axis will be close to 7’ long… I am sure the weight of the router will bow the conduit.

I have a large build as well 60" square with a working area of 1200mm the conduit doesnt seem visually to deflect with a dw600 on it at that length. I have perimeter supports at the mid point of each axis to keep the outer rails straight.

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I am interested to see how it performs at that length. I want to rebuild mine and make one small like 12x12x3 for most of the stuff I do but then I would like something like your plan for some bigger projects.

I did a rigidity test on some stainless steel at different wall thicknesses, It can handle that length for sure I did the tests at 6’ lengths or 8 can’t remember and hung a 10lb weight. Have a look if you run into issues with conduit SS is the fix. https://www.v1engineering.com/forum/topic/stainless-steel-quick-and-dirty-flex-test/

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Thanks Jason! So, at 60" you don’t see much sag in the gantry? That’s good news - I’m hoping having the area narrow and long will allow the Y gantry tube to support the super-long X as it travels. If it sags, I might reduce it to a 18"x72" area. I’m not too worried about the side spans, the supports should do it.

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Thanks Ryan, I’ll be reporting back! Good to know about the SS, one piece for the gantry wouldn’t be too much of an investment…

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Okay, box is complete, with extra lumber for the feet to screw into. Now to cut pipe…

Edit: Whoops, looks like the forum doesn’t like my pic. Rest assured the earth is in the right spot.

Torsion-box2.jpg
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Torsion-box3.jpg
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Box looks nice and sturdy!

I am starting to think about replacing my X and Y with stainless… I can leave the perimeter rails as conduit as I have added support mid way on the axis and they are very strong…

Question is… Is there a stainless pipe that will fit the 23.5 Center I just printed. HMMM

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That crossed my mind - if you find it, let me know! This, from the Stainless test link above, looks close-ish…

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So is this type of torsion box flat enough? Wouldn’t any twist in the 2x4s mess it up? Or does it just end up flat enough, after the ply and MPD toppers?

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Lots of people are starting to use cheap doors from the hardware store. Pretty cheap option for a ready made surface. I think it is a slick idea.

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A door sounds interesting. Plus it can fit in my car. Might even have one in the garage. Currently building a nice table for my small configuration.

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we have a “habitat for humanity re-store” here that sells used building materials. I got a $1 door to use for mine.

I had nice crayon marks all over the door. A little kid must have had a lot of fun and apparently likes orange a lot…