[shreifali]

Dear all,
I have built my cnc wood router machine using rack and pinion mechanism for X and Y axis and ballscrew mechanism for z axis.
The machine is working perfect but i am looking for enhancing the z axis speed to diminish the working time.
In other words:
The X and Y axis can reach a speed of 5000mm/min while the maximum Z axis speed which can be reached is 700mm/min. for example when 3D fininshing a relief, the X and Y axis seem they are waiting the z axis while if it were able to move the same speed of X and Y , the working time will be reduced 10 times approximately.
Therefore I plan to use the rack pinion mechanism for the Z axis and I bought a heavy duty stepper (holding torque 4.5N/m) and a driver board (200 steps per revolution TO 12800 steps per revolution) . The Z gantry weighs 10 kgs so the stepper can move it easily and 12800 steps/revolution gives me an acceptable high resolution.

This is my plan but I prefer asking the experts before proceeding , there may be an alternative using multithreaded ballscrews giving the same speed??
Thx in advance for your advice.
Best regards,
Baligh

[DukerX]

Are you sure increasing the Z speed would increase your overall performance that much?
If you look at the programmed feed rate vs the actual feed rate when Z is moving, is it really close to 1/10 of programmed?
Depending on your current hardware, you could alter the gearing ratio on the Z axis pulley (unless it's direct drive), or get a stepper that can handle higher RPM, or replace the stepper with a servo motor.
Going from screw to rack & pinion seem like a significant rebuild of the machine...

[shreifali]

Thx dukerX for your reply,
When 3d roughing with no change in Z , the machine is fast enough and at the same determined feed rate, but when there is a change in Z it slows . it becomes clear that there no consistency between x and y , and z.
The z axis is driect driven, no pulleys installed , and may using gears heats the plastic nut (5000 rpm needed).
I am now looking for a mutistart ballscrew for not rebuilding the z gantry in case of rack and pinion solution which will be my last choice .

[RICHARD ZASTROW]

Possibly a linear motor? No ball screw or nut is required. Draw back is either a power-off brake or counter balance is need for safety.

Dick Z