Leadscrew?

[Madclicker]

Originally Posted by bearwen Ger 21, I thought about welding 2 pieces of angle iron together and then set the pipe on top and tack weld the pipe to the angle iron for support the problem I have is bearings how do I build the bearing races to ride on the pipe I need to have support of the bearings in the x,y,and z directions correct they cant just ride on top and both sides cause then the gantry could lift as you lower the z axis correct I thought about the jgro type bearings but with the supported tube as I mentioned but is the jgro bearing any good or is there a better DIY way?

I would just use steel channel if you are going to weld it. I used AL channel bolted to the torsion box bed for my pipe supports and there is absolutely no flex in the pipes.

See Here

[Oldmanandhistoy]

This is an example of a thread that ends up being my opinion against your opinion.

None of which helps the thread starter and would only cause confusion and what could be an enjoyable experience ends up being a stressful task.

I know we all give our opinions with best intentions meant and we are all entitled to our own opinions.
There are certain people here who have a lot of experience and knowledge where cnc machine construction is concerned, me not being one of them.

All I would say to bearwen is this, first good luck with your build and second do not take any information as fact, and this is the only way to do it, use the information as a starting point. Take a good look around this excellent forum and see how others have done it and how well their method worked. There is no substitute for experience.

No insult intended or implied.

Best regards, John

[bearwen]

Oldmanandhistoy
Thank you yes sometimes people get side tracked and what not such as I asked peoples opinion of building out of steel and got only one reply but others about wood warp etc... well thank you all for the input I am studying other peoples designs and reading the threads to find what worked and what did not like you stated oldmanandhistory there is no substitute for experience since I have none I figure better to learn from others prototypes (mistakes).


Thanks again

[Firebird0095]

Mine is all 4 inch square steel tubing welded together with lots of gussets and I am using star linear rails, kerk screws, cmc 4445 servos, and api servo drives. The gantry is 8 inch square structural. Use one screw on each side of the gantry - good screws. There is no flex. Will cut aluminum just like a "real" cnc.

As for all of the engineering talk and people pulling out the modulus of elasticity. Flex in a machine is really a combination of different modes of bending that rely a lot more on shear and normal stresses and area moments of inertia. I think that these are good things to talk about but not in this thread. Plain and simple steel is better than wood of any kind, assuming correct design. For steel E = 30e6psi for the engineering types. The real issue here is money. If you have it - use steel and get what you want. If you don't then use wood and get some experience and then build another one later and make improvements. For me this hobby is for fun, so try to keep it fun and learn.

If you want engineering data for wood go to http://www.woodweb.com/knowledge_bas..._Handbook.html

If you want engineering data for metals or plastics go to www.matweb.com

Have fun!

[ger21]

The original question was what leadscrews to use. 1/2-8 2 start acme seems to be becoming the most popular after 1/2-10. You have to be careful when going to larger diameters, because they have much more inertia to overcome and may require more powerful motors.