Sherline 2000 CNC - Part 4

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6-25-2002

Fun with Power supplies.

 

Decided to upgrade my power source somewhat, so I started using this supply.
It came out of a DECPrinter, of 1980s vintage. It gives me 2 24V outputs at plenty 'o amps.

I was having a problem where the driver ICs were overheating when doing slow moves. Solution? Cooling fans liberated from Pentium heatsinks and a little G02 action on the top of the stepper driver box.

The airflow has eliminated my driver chip overheating problems.

They look 'cool' as well.

12-10-2002

 

To recap the setup so far, there are 55 oz-in motors on all axii. I run X and Y with a rapid of 15 ipm, Z set slightly slower. When the mill is adjusted and lubricated properly, it will reliably travel faster. However, 15 ipm is a conservative setting to allow for a 'safety margin'.

X and Y share a 24V power supply, Z has two supplies for a total of 41 volts (the maximum for the Allegro SLA7042 driver IC is 46V).

Driver for all three axii is a microstepping, chopping unipolar-style (not to be confused with those cheap 4-transistor unipolar drivers).

For some Z-axis experimentation, I got a Gecko G201 bipolar driver, a 48V switching supply, and a low-inductance 3A Vexta motor.

The motor is small, about the same size as the 55 oz-in motor, but square instead of round.

After removing the handleweel (it was making the whole mill shake), I was able to achive 60 ipm rapid on Z! Yes, 1200 rpm. Very fast!

And there was still some torque at that speed. I couldn't stall the motor by pressing down on the headstock as it was rising.

If I keep this on Z, I will probably limit it to 28-30 ipm, both to have a safety margin, and also so the mill doesn't shake itself apart.

 

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