Oiling GM3s?

I have been playing with a GM3 (the extruder motor) with no load on it. After a few minutes running at 5V it started making an irritating screeching noise. I could stop the noise by touching the motor axle, but it soon came back again, so I put a little light oil on the exposed motor bearing. That had a dramatic effect. Not only is it much quieter now, but it runs a lot faster for the same voltage. One downside is that when I remove the power it runs on a lot longer. I can stop that with electronic breaking if it becomes a problem.

I expect the effect would be less dramatic under load but probably still significant.

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[www.hydraraptor.blogspot.com]

nophead Wrote:
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> I expect the effect would be less dramatic under
> load but probably still significant.

I doubt it will make much difference for your extruder. For positioning, however, it is a significant technical challenge. I'm working on just that issue this morning, in fact.

Do you let your motor freewheel when you switch it off or do you use the bridge to short it to get braking?

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[www.hydraraptor.blogspot.com]

Sadly, the 754410 doesn't brake worth a damn. Mind, the L298N brakes beautifully, but not the 754410.

What I'm doing right now is throwing the damned thing into reverse. That works pretty good.

Edited 1 time(s). Last edit at 08/25/2007 04:18PM by Forrest Higgs.

hehe... i can imagine that is a pretty effective brake =)

Yes reverse thrust should stop you even quicker than regen braking but you risk going back the other way.

I just had a quick look at the 754410 data sheet but I can't see why it would be worse at braking than the L298. If you enable it with both inputs high or low it should short the motor. Because it uses Darlington pairs it will not do much once the motor generating voltage drops below 2V but the L298 should suffer from that as well.

A DMOS device like the ST L6201 / L6202 / L6203 should be a lot better in this respect. It would get you more torque as well because it will drop a lot less voltage. With a Darlington H bridge you must lose at least 2V out of your 12.

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[www.hydraraptor.blogspot.com]