Newbie CNC Build

[C.AlveSilva]

Hello,

My name is Carlos and i'm form Portugal.

I want to built a CNC router to make 3D wooden molds.

I was thinking in the xx axis use racks instead of ball screws, (the racks in the place of the ball screws, put the xx motor in the middle of the yy axis and using a shaft with a pulley at each end).

In terms of accuracy, racks is worse than a ball screw??

I want the router to make molds, for it I need a lot of precision. (For this kind of work an error of 0.1 mm (0.0039 inches) is an huge error.)

Would you, please, give me your opinion about the racks?

Thanks.

P.S.: Sorry for my English...

[JAZZCNC]

Hello,

My name is Carlos and i'm form Portugal.

Would you, please, give me your opinion about the racks?

Sorry Carlos didn't see your post.

If you want to do mainly 3D work and fine tolorences then I suggest you use ballscrews on all Axis.

Rack is ok for general profiling and machining etc but to do really accurate work with lots of repeatabilty then requires Hi quality Rack & pinions and because often with R&P you have to gear then you'll also need Hi quality gearing units or Pulleys and belts.! . . . All these will cost more than cheap chinese ballscrews and possibly perform no better if not worse.!

So IMO ballscrews every time. Thou this does depend on length of machine and even then I'd still consider using them just with a rotating ballnut.!!