Originally Posted by
joeavaerage
Hi,
That voltage drop is inconsequential. By all means hook up the X axis and compare.
A 50V power supply surprises me, its lower, quite a bit lower than I would have expected. With the '1500rpm' on the label I would have expected the voltage to be north of 100VDC.
Good low inductance steppers (less than 1.5mH) could be expected to retain 35% of the holding torque at 1000rpm with a 60-80VDC driver. A lesser motor, say 4mH inductance,
would be lucky to have 25% of its holding torque at 500 rpm, let alone 1000 rpm, and at 1000rpm I would expect less than 10%.
Taking the two considerations in mind, ie high voltage equates to high speed and low inductance equates to highspeed leaves a bit confused about what steppers you have,
are they some 'super low inductance whizz bangs that defy physics' or what?????
I suspect you are right, this machine was equipped with servos and clearly steppers are never going to match them no matter how hard you try.
What I would recommend is calculate the gear reduction ans set the max velocity such that the stepper is doing 500rpm at max velocity. Set the acceleration to 10% of that.
Then, leaving acceleration alone, increase the max velocity until it stalls or starts missing steps. That is a better and more practical measure of what your steppers can achieve in your machine.
Once you have established that limit, reduce the max velocity to 75% of what you have found and start increasing the acceleration, until it too starts missing/stalling.
The aim is to have as high acceleration as possible, it promotes the best and fastest toolpath following, and is usually more important to cycle time than max velocity, strange as it
may sound. Most toolpaths spend more time accelerating than at max velocity, so acceleration is favoured over max velocity.
Craig