Help with Servo Power Supply for Bridgeport conversion

[glockabilly]

I have three servo motors I picked up awhile back that I would like to eventually use for a conversion of a Bridgeport mill. Right now, I want to see if I can get one motor and driver and software communicating but would like to get the power supply that will be enough for the overall conversion so I don't have to buy another one when I'm done testing/learning. So far, I've been looking at the PS at AnTek Inc. on e-Bay...


Here's what I'm using or planning to use:

Driver: I just bought one Gecko 320X.
Software: Mach 3
Motors: Three MAE M644 (M644 1340 127 635 13TSZ)

They are old and the only specs I could find online are:
Continuous Stall Torque 1.4 Nm
Peak Stall Torque 6.36 Nm
Continuous Stall Current 10.7 A
Maximum Pulse Current 48.9 A
Maximum Terminal Voltage 60V
Maximum Speed 4000 RPM

Torque Constant Kt 0.130 Nm/A
Voltage Constant 13.4 V/kRPM

I measure the x and y axis and it takes about 1 ft-lb to turn the screws. The knee takes about 6 ft-lbs to raise.

I'm not sure how you figure out max speed I need. The current screws turn .200/rev for x and y and .100/rev for the knee. Do you run the motor to be at peak torque? This would be about 0-500 rpm where peak torque is 6.36 Nm which would be 100 IPM for 1:1 ratio which would be plenty. I think the knee would need some gearing to get the required 6ft-lbs (8.13 Nm).


Any help on how to size the power supply would be appreciated!

[Al_The_Man]

The should not be run at more than the continuous stall torque value.
Are you thinking of CNC'ing the knee as Z axis?, this is not considered a good idea due to the inertia of combined knee table and any work piece.
For operations such as peck drilling etc, the inertia is extremely large usually requiring a high gearing ratio.
The torque required to turn the axis is the break-away torque, the torque required is calculated on the desired accel/decel rate.
Which has to be within acceptable motor to load inertia ratio.
There is free sizing software on the Kollmorgen site.
Al.

[glockabilly]

Al,
Thanks for the clarification on torque.

Ok, I'm learning...albeit slowly so please bear with me :-). So what you are saying is I should reduce my load inertia so the system is more responsive and doesn't oscillate which means I have to gear the motors to be within the acceptable motor to load ratio.

Are there any guidelines for determining the desired accel/decel rate? I have no idea what a functional value should be. This is a machine for my own personal use so I don't have any requirement to accel/decel a load at certain rate. If it takes longer to accel/decel, is the only implication that the whole machining process would be slower or are there other implications?

-Satch

[Al_The_Man]

Pluging in numbers into the software gives you an idea.
In reduction terms, torque is increase at the rate of reduction and inertia ratio is decreased by the Square of the reduction, 5:1 reduces inertia ratio by 25.
Usually the accepted level is 10:1 max. motor-load inertia ratio.
Al.