First Frame(r). Thoughts on materials

Frame material:
I’ve read several articles here in the forum and I’m leaning towards a complete metal frame using either Uni-Strut or T-Slotted extruded aluminum. I’ve seen several articles on the former but next to nothing on the latter. Anyone try experimenting with this? I’ve built several industrial machine frames using nothing but this material. Nice part about it is all connectors and accessories including monitor mounts and castors. A bit more expensive but very modular.

Drive Train:
I’ve read about some of the issues how chain sag affects accuracy. Would a timing belt help? They make cut-to-length for used for motion applications.

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Could you explain a bit more?

The main reason for not using aluminum extrusions is cost… my homedepot procured unistrut (12’ beam) frame easily approached $350… if you can build a similarly sized t-slot extrusion frame for less than 2x that, please let us know!

a timing belt replacement for the chains isn’t a bad idea but would require some inventive design to keep the belts on the sprockets, go for it!

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the belt will still sag (not as much because it’s lighter, but it will sag) We
are implementing code to account for this, so eliminating the sag is eliminating
something we are able to account for.

the belt will also stretch. We are not working to account for the chains
stretching depending on how much force is on them.

it will also wear faster than the chain.

I doubt it will be a win, you are replacing one error that we are working to
account for with a different error that we are not working to account for.

David Lang

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here is an aluminum frame ( no legs) 3 long pieces in blue are 1.5" channel, everything else is 1.25" square tube. tube simply fits into the channel and a drilled hole with bolt holds it together. for the shorter vertical tubes use tube nuts pounded into the ends of the tube from McMaster. I think the weight was 60 lbs With the current price of aluminum about $2.50 a lb should cost about $150 to make.
You would think steel would be cheaper, but it winds up costing about the same since steel is about 3x denser than aluminum and costs about 1/3rd as much $1 a pound typically. then you have to factor in paint costs which is no fun IMHO.

you need to move the top beam forward of the rest of the frame about 6"

you don’t need nearly as much framework in the center area, you could loose the to middle horizontals without any significant difference.

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