I'm so screwed :)

[freak_brain]

First post for me so I must tell all of you, I am new to building CNC machines. However, I have been machining parts for about 20 years so I do understand the concepts.

Presently I am building a CNC plasma/router gantry type machine. I'm at the point of thinking about ball screws, lead screws, acme thread type screws etc.. Lead, ball dia, and the different brands seem to come up also. Here is what I am trying to accomplish. I want a machine that is reliable and accurate. Does this mean I should use a ball screw for each axis? Is that over kill for this type of machine?

Also, how does one figure out how much torque he needs out of his servo motors?

<---put this in because it looks funny. Dances like I do. Maybe that's why I'm single, lol

Any suggestions would be greatly appreciated.

Thanks
Allen James

[Ken_Shea]

Allen -
If you can afford the ball screws most definitely use them, however there are a lot of very successful machines using simple acme thread. It all depends on your budget and what you require of your finished equipment.

[freak_brain]

Your right Ken. I have spent a lot of money on good slides, servos and other stuff. Wouldn't make much sense to cut corners now. What lead would you recommend? .200-.250?? I figure with a 1000 ppr endcoder and a .250 lead I would have a minimum movement of .00025, is that correct? If so, that's plenty close enough for what I plan on doing. Thanks Allen

[Ken_Shea]

Allen, I cannot offer you any help with the lead information at all, I have never done a single calculation in regards to this.

Sorry
Ken

[HuFlungDung]

Allen,

Since you're going with servos, there is something to be said for high resolution encoders. Even your 1000 line encoder may give you a resolution of 4000 encoder pulses (via quadrature output). More lines of resolution helps your motion controller keep better tabs on the motor position. This can help get better motor performance when tuning your servos. But for actual positioning accuracy, the 1000 line is likely fine.

[freak_brain]

thanks guys, I appreciate the input!!


Allen