[lerman]

Originally Posted by kanankeban Hi Chris, Thanks for so helpfull information...regarding your comments, 1. I'm thinking on using either camfollowers over a machined flat or v bearings over either regular steel angle or v railings(expensive! for a 6'x12'or20' table). I don't have a remotless idea on the friction on this kind of linear axis. 2. Im planning to use rack and pinion in x,y,z axis, don't know which one is better 14.5 degree angle or 20 degree, and I don't know either what kind of friction they impose on the system. 3. The weigh of the gantry, well, Im planning to do it from steel so it will be pretty heavy. the maximum speed for cutting is 240ipm, I'm building this table for a Hypertherm HT2000 High Speed Plasma. I'm planning to use servos with drive belt reduction...on x and y axis. for the z just a small dc motor, I'll be using the rutex 510 board. What kind of calculations will be involved in this type of design...in conclusion ---big table ---heavy gantry ---fast speeds ---rack and pinion ---v bearings or cam followers Regards, Hector

In addition to the forces associated with friction, don't forget to add in the force associated with acceleration. Most of the forces associated with friction are independent of the speed (I assume that you are not going so fast that air resistance is a consideration).

Ken