extruders

Topics Related to the ORD Bot Printer

extruders

Postby keos » Wed Oct 31, 2012 6:23 am

if i decide to just use one extruder do i need to remove one of A4988 stepper driver (pololu compatible) from the ramps board or i can just leave it in place..
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Re: extruders

Postby fma » Wed Oct 31, 2012 7:29 am

Some people reported that it can be dangerous for the driver to be powered up without motor connected... I don't understand why (in my job, we use dozens of big steppers, using much higher voltages and currents, and never had such problem), but as these Allegro devices are not really the state of the heart...
Frédéric
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Re: extruders

Postby bdring » Wed Oct 31, 2012 12:23 pm

Starting a driver without wires connected is not a problem. Some drivers can be damaged if the motors are disconnected when the drivers are on. I have not seen that happen, but I follow that advice.
Bart
"If you didn't build it, you will never own it."
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Re: extruders

Postby fma » Wed Oct 31, 2012 12:35 pm

True, interrupting current in an inductive load leads to high voltage (L.di/dt), and this can easily dammage the driver.
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Re: extruders

Postby royco » Wed Oct 31, 2012 3:48 pm

I've managed to fry a few drivers with no motors connected @24v(nothing happened @12V) during testing and Im not sure why/how(if I have at least 1 motor connected and nothing for the rest its fine). It also only happens with allegro chips, the ones from Ti wont mind at all. Im suspecting its the power supply spike that kills it. Reversing the orientation is the surest way to kill it, unplugging wires while powered/running have damaged a few but not all the time.

My suggestion, remove it.
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Re: extruders

Postby mikegrundvig » Wed Oct 31, 2012 6:31 pm

Some drivers can be damaged if the motors are disconnected when the drivers are on. I have not seen that happen, but I follow that advice.
I've seen this happen when a wire pulled loose while the motor was running. Allegro chips are REALLY fragile.
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Re: extruders

Postby orcinus » Wed Oct 31, 2012 7:12 pm

royco wrote:My suggestion, remove it.


That's what i'm gonna be doing from now on (or, actually, since my SureStepr incident).
Live and learn...
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Re: extruders

Postby keos » Wed Oct 31, 2012 9:42 pm

Thank you guys for the input
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Re: extruders

Postby Locus » Sat Nov 03, 2012 9:05 pm

mikegrundvig wrote:
Some drivers can be damaged if the motors are disconnected when the drivers are on. I have not seen that happen, but I follow that advice.
I've seen this happen when a wire pulled loose while the motor was running. Allegro chips are REALLY fragile.

This happened to me on the day you posted this, funny enough. A motor connector worked loose, I fixed it, then a little later the stepper driver started acting weird. It would randomly stop, reverse directions, etc. while driving something.

Luckily I had a spare from my RAMPS kit, so I just swapped it in and booted things back up. It fried that one because I wasn't paying attention and somehow put it in backwards despite knowing better. :roll: Two lessons learned! And I got to practice more soldering when my eBay replacement arrived today.
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