Here is the setup to calibrate the Y axis "steps per". I clamp down a 1-2-3 block, jog up to zero the indicator, move 3" to the back of the block and see if I hit zero again on the dial. The theoretical number for the Y with its 1.8 degree stepper and 4mm screw pitch is:
360 / 1.8deg = 200 x 10 (for the micro-stepping Gecko drive) = 2000 steps per revolution.
Steps per unit (1") is 2000 x 25.4mm/4mm pitch = 12700
After a few trials I settled on 12710 microsteps per inch.
On the X, with its 5mm pitch screw, I ended up with 10159 steps - just one fewer than the calculated 10160.
Some possible candidates for the motor:
360 / 1.8deg = 200 x 10 (for the micro-stepping Gecko drive) = 2000 steps per revolution.
Steps per unit (1") is 2000 x 25.4mm/4mm pitch = 12700
After a few trials I settled on 12710 microsteps per inch.
On the X, with its 5mm pitch screw, I ended up with 10159 steps - just one fewer than the calculated 10160.
As far as velocity and acceleration goes, with the admittedly under-powered steppers currently installed, I can't get anything more out of the X- axis than 23 IPM at 100 in /s/s, pretty slow. Why?
The screw is 5mm pitch, so 25.4mm/inch / 5mm = 5.08 rev/inch.
Multiplying the rev/inch by the inch per minute gives us RPM: 5.08 x 23 = 116.84 rpm - also pretty slow.
Multiplying the rev/inch by the inch per minute gives us RPM: 5.08 x 23 = 116.84 rpm - also pretty slow.
Update 2013/9/24 - I significantly lowered the acceleration curves to around 5 in/s/s and got better, but still not great, rapids of 50ipm. However, while cutting out the perimeter of one of the Z mounting plates with a relatively conservative cut of .25" depth x 0.5" wide @ 17.4 ipm I lost a bunch of steps in both axes. In managed to salvage the part, but it is further evidence that more torque is required...
If we look at the performance chart for this motor (with a 24v power supply) we can see the torque available is around 330 ozin at 100 rpm, about as much as you can get from this motor.
The supplier for these motors has a fairly good tool for sizing. Having followed that guide, the minimum torque recommendation was 310 ozin - but while we don't need all that torque for the rapids, the motor obviously needs more than the torque than this one has at the target speed (which if we want rapids of 100 IPM is 100 rpm x 5.08 rev/inch = 508 RPM). From the torque/speed curve we can see that less than half of the recommended torque is available at that speed. So some stronger medicine is required here.
Some possible candidates for the motor:
No comments:
Post a Comment