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Jon Jantz Wed 02 February 2011 13:25

Need Motor Sizing Help Please
2 Attachment(s)
Howdy, Mechmate guys...

I have a question that I am seeking help with.

I have built a CNC plasma built loosely on the Mechmate plans. My brother in law Blake built a Mechmate router a while back and I consulted him quite a bit while building this...

Anyway, I bought OM PK299-03AA motors for it and have been using the plasma. I recently decided to build some belt drives for it to get a little more accuracy and have gotten my X belt drives made. However, I do not have room on my gantry for the Y motor to have a belt drive, so was wanting to replace that motor with a 3.6:1 geared motor from Oriental Motors.

My problem is figuring out which one I can get that will work with the power setup that I have... where can I get the info to figure this out or can someone point me in the right direction?

I have the PK299 motors wired Unipolar and my power supply is supplying them with around 50V DC. (If I remember correctly....)

The PK299-03AA motors specs are as follows...

Current per Phase (A/phase) 3.18 [Bipolar (Series)]
4.5 [Unipolar]

Lead Wires 6

Voltage (VDC) 3.9 [Bipolar (Series)]
2.8 [Unipolar]

Resistance (Ω/phase) 1.32 [Bipolar (Series)]
0.66 [Unipolar]

Inductance (mH/phase) 10 [Bipolar (Series)]
2.5 [Unipolar]

I was looking at the PK296 geared motors but can't seem to figure out which one I could use that would work with my setup....

Sorry for being so dense, any help is greatly appreciated.

I'm attaching a couple of pics of my belt drives and gantry area.... no LOL's please.... :)

Khanid Wed 02 February 2011 13:47

If this can help you?! Description on how we plan to build our plasma, good deal about motors there.

Richards Wed 02 February 2011 15:41

The PK299-03 with inductance of 2.5mH is close enough to the PK296A2A-SG3.6 motor's half-coil inductance of 1.5mH that you can run both motors from the same power supply.

The A2A motor is rated at 3A. If the motor runs too hot at 50V, then limit the current to 2A or 2.5A. I've just finished some testing with a 47VDC power supply and my PK296B2A-SG3.6 motors rated at 3A and had absolutely no heat problems.

If you're really worried about heat, you could also run both motors from a 35VDC power supply instead of using the 50VDC supply that you have. You would sacrifice a little of the top speed with the PK299-03 motor, but that top speed is not usable on most CNC machines. (I ran a PK299-F4.5 motor at 2,000 RPM with a 47VDC power supply. It sounded great and it made a great impression on the observers, but anything over about 750 RPM is for show only - wasted RPM that only produce excessive heat.)

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