timing belt instead of screw

[Ed Williams]

I wanted to use the attached design with 25mm belts on a 4x4 table. I was going to gear it 3 to 1. Could I get some pro and con on this.
Thanks Ed

[Al_The_Man]

I have used this principle, Breco Belts sell the belting and hardware for this method.
Al.

[LazyMan]

I wanted to use belts and eventually decided to just go with rack and pinion because it was more cost effective in the end.

If you do go with belts take a look at http://www.cnczone.com/forums/showthread.php?t=59570

[johnmac]

If I build another table, I will use belts for the X and Y, and a screw for the Z. 3 full turns of the stepper for 1 inch of travel is just about right.

John

[ger21]

Originally Posted by johnmac 3 full turns of the stepper for 1 inch of travel is just about right. John

A 1" pulley will give you 3.14" of travel, so I think you'd need 9:1 gearing to get 1" of travel for 3 stepper rev's. And with larger belts, you may need larger than 1" pulleys.

[Ed Williams]

Gerry
I have a couple of problems in this design. Here I go. I'm using a 20mm jack shaft on x to drive pulleys on each side. So the 20mm limits me on the size of pulley I can use. I'm using at5 25mm belts. I have on the servo 14t and jack shaft 42t. This is 3 to 1. Now the smallest pulley I can go is 28t because of 20mm jack shaft. This puts me at 46.6666666mm per motor rev. That is putting me around 1.8372 inches per rev. I know on my other machine my servos at 1 inch per rev will snap a bit like it was even there on a screw up. So I'm hoping that I will still have enough torque on this new setup. I using a 150w YAG laser so no drag. But I want to add a spindle for pockets. What do you think?
Ed

[johnmac]

My suggestion on the 3:1 is based on resolution vs speed for a stepper driven table.

John