Talk about all things CNC
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chamnit wrote:Probably the best solution for this size table would be welding or building a metal (steel or aluminum) 5'x5' frame like @veng1 suggested. But, not everyone has the $$$ or the equipment to weld it together.
http://www.lkgoodwin.com/more_info/galv ... ngle.shtml
My Dad built a workbench out of the stuff once --- still bummed it stayed behind after a move.
Shapeoko 3XL #0006 w/ Carbide Compact Router w/0.125″ and ¼″ Carbide 3D precision collets
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One of the things I've found in trying to use the structural elements that are "L" shaped is that they don't, at least by themselves, resist twisting. Extrusions may cost more but also may end up worth the extra cost. A box section just works better for me. What little I know about structures was mostly from "Racing and Sports Car Chassis Design", by Costin and Phipps. If you can find a copy, get it. It's quite dated but illustrates the thinking that was used in a lot of winning race cars.
I also like the heavy Mitsumi corner brackets that fit aluminum extrusions because the higher priced ones are actually 90 degrees. I've measured stamped corners that weren't even close.
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You could use uni-strut for a low cost structural element and place a torsion box on top of that. Some suppliers carry up to 5'x12' sheets of MDF.
I would likely make a frame out of 8020 extrusion with a torsion box and sacrificial top, placing the seams in the T-slot recess in the X direction.
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For reference, open cross-section beams, like an L-beam, I-beam, or C-beam, are all horrible in torsion. Meaning that they twist easily. But that doesn't mean they can't be used.
They are great cheap options as long as these types of beam are put into positions where they will not be loaded to twist, in something like a truss. A truss is one of the most efficient structures, in terms of low mass (minimum material) and high stiffness. They are used everywhere in space, stage lighting, and construction (cranes). To create a truss-like base frame, you basically just need to add diagonal members to a frame and try to keep all of the members intersect close to each other (not midspan). You'll be amazed how incredibly strong and rigid of a frame you can make this way.
Wood 2x4 truss-like frames are just as good, since the wood expands mostly in the width of the 2x4s not the length. The first workbench I made had a truss design. It was so rigid that it would always sit on three of the four legs no matter how much weight I put on top of it. Anytime I moved it, I had to shim the fourth leg so that it'd sit level on my uneven garage floor.
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Anyone else anxiously awaiting the availability of the expansion kits? I have a few projects that I am working on and feel somewhat limited by size - so I am using the first run as practice - then I'll remake them once I get the kit.
Mainly want to keep this thread near the top so Carbide knows we are ready to send them payment!!
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I haven't purchased it yet, as my primary projects require certain lengths which disqualify a machine which isn't suitable to those requirements.
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I've been looking for an update regarding expansion packs. Has anyone heard anything?
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At least do you know if, in the end :
Will you offer the extensions as an upgrade only? Or will you sell "extended shapeoko 3 kits" with the long extrusions already in the box?
Last edited by grep
on Tue Sep 29, 2015 10:56 pm, edited 1 time in total.
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- Location: Dixon, IL
Hey all - sorry for the spotty feedback on this thread.
The expansion packs are important to us too. We've been working hard on fulfilling the backorder, and getting the supply chain stuff in line so we can get in stock and stay there. Once that happens, everything gets a little easier here.
I've been constantly starting and stopping on the larger machine build for quite a while. Like a lot of things, the 3D model was a good starting point, but as the build progresses, designs change and things need to be modified. Getting the prototype parts isn't a big deal but they take time. I'm having a few pieces laser cut now, but it's going to be 2 weeks before they're completed and shipped to me for fit-up. Long story short - it's slow going, but we're moving along.
Stick with us, we're not going to let this go to the back burner. It's something that we're excited about and want to get done as soon as we can without being neglectful of the other project's we've been working on.
Shapeoko 1 #0 - a couple of upgrades.
Shapeoko 2 #0 - a couple of upgrades.
Shapeoko 3 #2 - Stock