Another off idea...

[mbele]

I've checked preloaded brand name ballscrews on ebay, and found few solutions for Y and Z. I have to select ballscrew for the min possible diameter (inertia) and required stiffness.
Considering 180N load and 0.05mm allowed error, can I assume that total stiffness of the machine at the tool tip should be no less than: 180N/0.05mm=3.6N/um? Would then a 12mm dia ballscew with rigidity(K)=120N/um be enough?

I've sketched a solution for X axis base. Tubular structure would be made from a 50mm thick granite slabs, glued and fastened together with screws. Steel rail supports would be fastened on top with screws and epoxy, and then shaped and ground to create plane for mounting rails. Would a rail span of ~200mm be enough (I see that span used on gantry machines)?

[driftspin]

I've checked preloaded brand name ballscrews on ebay, and found few solutions for Y and Z. I have to select ballscrew for the min possible diameter (inertia) and required stiffness.
Considering 180N load and 0.05mm allowed error, can I assume that total stiffness of the machine at the tool tip should be no less than: 180N/0.05mm=3.6N/um? Would then a 12mm dia ballscew with rigidity(K)=120N/um be enough?

I've sketched a solution for X axis base. Tubular structure would be made from a 50mm thick granite slabs, glued and fastened together with screws. Steel rail supports would be fastened on top with screws and epoxy, and then shaped and ground to create plane for mounting rails. Would a rail span of ~200mm be enough (I see that span used on gantry machines)?

Hi mbele,

This is gonna be an intresting build if your total allowed error is <0.05mm @ 180N

What servos can run at 180n at operating speed. Did you check the stepper calculator on this site?

Also please check what happens with 180n force in all directions at the tool tip on all (moving) parts combined.

One does realise quite quickly that everything looks like made of rubber.


Grtz Bert.

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