[ger21]

I'd put a lot more ribs in that gantry beam. Here's a pic of mine. 12"x40", 3/4" Baltic Birch.
http://www.cnczone.com/forums/attach...0&d=1109818854

[louieatienza]

I'd put a lot more ribs in that gantry beam. Here's a pic of mine. 12"x40", 3/4" Baltic Birch.
http://www.cnczone.com/forums/attach...0&d=1109818854

ger21 that looks solid! You have a build link?

[ivojnob]

That's looking great! The 5x 12 sheets must've weighed a ton!

Yeah, they were a little heavy. I cut off a 3' end to use for the short ribs and a 2' strip off the remaining 9' length for the long ribs. Pushing those pieces through the table saw was much easier than a 5x12 sheet. The problem is that the completed box is going to be 300 lbs!!!

BTW I take you're a bon jovi fan? (I'm a big Jumble player...)

I used to be long ago. Back then I had a hard time finding a userID that wasn't already taken (I'm not very creative), so this is what I used. I never bothered changing it.

I'd put a lot more ribs in that gantry beam. Here's a pic of mine. 12"x40", 3/4" Baltic Birch.
http://www.cnczone.com/forums/attach...0&d=1109818854

That does look good. I'm going to focus on the main frame for now, but I'll definitely look closer at your gantry when I finalize the design of mine.

[brtech]

Are there some torsion box experts out there? I'm trying to understand what is important and what is not about torsion box design.

For example, do the joints in the ribs matter? I've seen lot of the 1/2 "U" joint (as in this design) where the horizontal and vertical ribs are continuous pieces with joint cuts 1/2 way through. I've also seen designs where one axis is continuous with no holes, and the other is small pieces with no holes, with the joints just glued and brad nailed to form the honeycomb. Does it matter?

Most designs have the ribs in square or rectangular boxes. Does that matter? Could one axis be staggered?

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How do you calculate the thickness of the rib material, or for that matter, the skin material to get flat surfaces? Clearly there is a relationship between how many ribs and the strength of each rib.

Most designs have the outer edges thicker than the internal ribs. Is that actually part of the design, or just done for other reasons?

Most designs I've seen use either ply or MDF for the ribs. Is ply better or worse in compression on edge than MDF for a given thickness?

When you support a torsion box, does it matter where the supports are? Is edge support better than, say, a platform that covers 1/2 the area in the center? I'm guessing it behaves like any other slab, and it's the longest unsupported span that counts, but is that really true for a torsion box?

[DHSYCNC]

matter you choose ball screw and rack and pinion, both stone and hardwood can be engraved and get good result. But if compare with ball screw and rack structure, result engraved by ball screw is far better than rack one. From photo, gantry is weak.