Determining max velocity, max acceleration?

Going by the Getting Started Manual V 2.5. If I'm reading it correctly, I should set the acceleration at 2 "/sec, and the velocity near what I hop to attain.

I set the velocity at 100 "/min, and tested. No problems, so I increased the velocity. I kept increasing at 10-20% until I reached 3000 "/min. Still no missed steps while I was pushing back against the table. I decided to stop there, as it seemed an insane number. I then started working on the acceleration value, and increased it to 500 IIRC, before encountering missing steps. Decreased to 350, and still missing steps. Decreased to 200 and still missing steps.

Finally decided to start over, I put in 250"/min as the max velocity, and 15"/sec as the acceleration. It was missing steps, so I backed down to 10"/sec on the acceleration and everything seems fine.

Does this sound reasonable???

thanks,
Ken

Hi

Most people seem to set their velocity and acceleration far too high for what are comparatively low power motors.

Two factors to consider are that acceleration is not nn"/sec it is nn"/sec/sec;
also the figures in the .ini file are in units per second. That works fine for acceleration but when looking at velocity you need to multiply the figure by 60.

My Nema34 12Nm geared stepper powered turret mill, has axis MAX_VELOCITY of 25mm/sec (1500mm/min) and MAX_ACCELERATION of 12mm/sec/sec
It never misses a beat and can be left unattended for hours

Compare your figures by multiplying them by 25.4!

Another consideration is that you should set the MAX_LINEAR_VELOCITY under the [TRAJ] section to approx 20% higher than the individual axes to ensure co-ordinated moves can be brought off.

I don't know what machine you have, the time when steps are lost in real world machining are normally at high speed when the torque is lowest. A quick G00 retraction on a lathe at the end of a heavy cut is a favourite.

regards

John:

Just typing in shorthand, I guess. I thought everyone would understand. It is 2"/sec(squared), or 2"/sec/sec.

I guess on a "technical" forum, I should try to be more technical.

Ken