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Hey everyone
Its been a long time since but i want to finish my CNC Table and it just pooed in my head to go with a timing belt system
If i remember right my gantry is around 6 feet long and about 500 pounds.
Would it work if i use a timing belt on both sides ???
What size of motor would be recommended ???
I would imagine i would need a gear reduction ???
Thanks a lot everyone.
Yes, and no.
Timing belts stretch a little, and more under increasing load.
They are not very rigid - under increasing load.
The wider the belt, and the bigger the profile, the stronger and more rigid it is.
IF You used a HTD-8 mm profile belt, 30 mm wide, on both sides, it would give reasonable positioning rigidity ..
and be easy to do.
The accuracy would be good enough.
But it is quite expensive.
HTD-8-30 pulleys are expensive, and the belts are relatively expensive.
The system, 6 feet, might cost 400-600$.
2 fixed belts 6 feet long, 2 pulleys, 2 idlers per side with bearings, total 4 idlers.
The smaller HTD-5 mm profile, say 15 mm wide, is much cheaper.
It is pretty accurate, but not rigid enough.
Rack and pinion will be much cheaper, more rigid, and easy to do.
All opinions based on using HTD5-15 with steppers, servos, about 20 times+,
and HTD-8-30 with a 2.5 kW AC brushless servo, for both power and positioning,
and HTD-8-30 with AC brushless servos for x and z axes at 1:2 for a high end lathe motion control system.
The pulley system and belts cost about 450 € with taperlock pulleys, wholesale cost to me.
Recommend rack and pinion.
Thanks for your help :)
I started building this table with a Thomson ball screw, witch is very accurate but slow and hard to setup,
I had the idea of a belt drive setup, in my mind it would be quick and easy to setup, i am not to worried about the cost, and wear i am i can get pretty much anything i want.
I just want to get the right things, i was looking at going with about a 3" inch wide belt, I know rack and pinion is the way to go but i think it would be a bit more difficult to setup, with what i have already made.
In my head i was thinking of getting a couple belts a few pulleys slap that on and yay! done :) hehehe The machine is been 10 years in the making :( i would like to finish it before i die hehe
I may have a other look at it and maybe i can go with a rack and pinion setup,
Do you think i can still have the accuracy and the power of the ball screw ???
I have decided i am going to go with a rack and pinion system,
Looks like the Nexen system is the best zero back lash and super fast, that is what i am getting :)
What you think ???
I use 25mm timing belts for my cnc table and don't have any problems with my setup but it depends what you want to do. I just plasma and torch out weldments so +-.010 really doesn't matter to me when welding them up. For a router belts would probably be bad with the spindle forces resisting movement. My table is 6' by 18' so a rack would be very expensive compared to a few belts. I also use a driveshaft with belts on both sides for squaring so essentially it could be looked at as a 2"wide drive belt. The carriage I would estimate around 500 lbs also driven by a 5000oz nema 42. Z axis is ballscrew. It will do 450 ipm but acceleration can sometimes be a problem. What do you plan on doing with your table? That can be a determining factor.
Don't have any answers, but was curious. Has anyone ever used a roller chain drive?
I thought about chains too but ruled it out cause my table is 18' long. That much unsupported length of chain would be problematic I think. Chains are not generally thought of as a anti backlash type of driving mechanism. I would think that with a chain stretched out and only one, maybe two sprocket teeth engaged into the chain there would be too much slop to make acceptable parts. You could run two idlers and the sprocket to get more wrap like a pyramid setup and that might work but I still have not seen a chain drive gantry on a industrial machine.