4th Axis & LinuxCNC 2.7.15 RTAI i386

Hi All,

recently I made the 4th axis my home made CNC machine. To run it I use arch i386 RTAI kernel and Wheezy platform.

The machine has two step motors on X axis (gentry), and single motors for Y and Z axis respectively. The BoB used to operate machine is 5axis LinuxCNC/Mach3 (see enclosed link LinuxCNC Mach3 Breakout Board ) and in XYZ setup everything works like a charm. In configuration file P2 & P3 is used for X master motor and P8 & P9 is used for X follower motor. P4 & P5 for Y motor, P6 & P7 for Y motor.

Now with rotary axis I use P16 & P17 for A motor and set Axis performance later in config file as following: Steps 200, micro-stepping 64, gear ration 1:3, pitch 120 degree/rev, velocity 100 deg/s and acc 500 deg/s2. Home at 0, table travel -99999 to 99999.

When machine is fired-on, all motors are activated ready to go. All axis, double X, Y and Z works as before, however very slow move of A axis. Checking wiring, connections, cables nothing was found wrong. When I change connection and settings (swap) Z and A axis, A motor speeds up, Z is rarely rotating.

Is there anyone who could help me, give some advise, what I did wrong, what to do to get A axis running as good as other three?

Thank you!

Thank you Tommy for support. The microstepping was changed to 5 (all other axis set to 5 -- metric ball screws in all three linear axis), and max speed set to 1500 deg/s. Worked well. However, during the time it happened motor was speeding in one direction and in opposite started to jerk. Driver was checked - CW5054, wiring, connections, par port cable, everything was OK. The only thing not checked is BoB. Tomorrow I'll get new one and check if that is issue for my joy.

Though I would have fine tuning and accuracy setting of the rotary axis, for pulley - gear reduction 3:1, should I set 120 or to leave 360 deg/rev as pitch, what is your proposal?

Once again, Tommy thanks a lot. I set step time to 5000, step space 8000, machine started. Today I rounded the first piece of wood. Max speed revolution I could get is 90'000 which is not as fast as I thought.

In 4axis, I kept X, Y and Z axis alive. Present post-processor X values wraps around Y, outputs as A, ,which is Ok in my setup.

Cheers!

Hvala