Extruder motor overheat

[Grambo]

Hello!

I just received and assembled my rostock max v2 a week ago and I am having troubles with longer prints!
The stepper motor that controls my feed rate has a nasty habit of heating up (over time, thus the problems with longer prints). What happens is the heat eventually transfers through the friction feed wheel and melts the plastic in the feed! It then continues to wrap the plastic into a massive mess, and the printer continues none the wiser to whats going on.
I've done some poking around online and have discovered that the motors usually heat up, but I don't think it's supposed to get as hot as it does. After comparing by touching the bed at 60 DG to the motor it feels at least 90+ degrees.
I figure it cant be an electrical short, as that problem would show itself within minutes not an hour- two hours.

So what is all of your expert opinions!?

Thanks in advance,
Graeme

[Polygonhell]

You probably just need to reduce the motor current in the firmware, if you purchased it assembled, support should be able to walk you through it.

[TMIB]

This is the exact problem I had with mine. Turns out I had missed a step in the configuration manual.

Bottom of page 12, top of page 13:

If your kit was shipped with the Kysan or Automation Technology stepper motors (we covered
that earlier, remember?), you're going to need to make a small tweak to the firmware in order to adjust
the current drive that they need.

Click on the tab in the Arduino IDE marked “Configuration.h”. Around line #701, you should
see this text: #define MOTOR_CURRENT {175,175,175,200,0}. (or similar)
Change that line to this:
#define MOTOR_CURRENT {150,150,150,130,0}
Save your changes and upload the updated firmware to the RAMBo, just like you did in the
prior step

I did that to mine, and the motor runs nice and cool now. (Changed from 65C to 35C on the outer case)

[thedoble]

I found that my stepper runs hot regardless of the firmware change.

As such I printed this little fan shroud for the extruder. My stepper runs nice and cool now.

http://www.thingiverse.com/thing:244292

[Grambo]

I double checked my firmware and it is set properly for my motors. I would throw a heat sink and fan on it, but if it's heating up so hot brand new I can't imagine it will last all that long. I'll send them an email, maybe this is something that they will cover.
None the less, thanks everyone!

[thedoble]

Steppers do run very hot - however over 90 degrees is probably too hot.
Check your extruder assembly. Make sure that the filament path is straight and it's not rubbing against something. Check that the cog is lined up with the filament path.

A useful test would be to remove the bowden tube and just extrude and retract some filament repeatedly for a few minutes. If the stepper gets hot then you know it's something in the assembly. If not, it could be further down the line.

After I put the fan on my extruder, it went from being over 60 degrees to room temperature. I've got 22 days of print time so far without issue.

[Polygonhell]

Steppers are constant current devices, they don't get hotter because they are pushing against resistance, they run their hottest when the motor is enabled and they are just holding position. Which is largely why there is a timeout that disables the motors if they aren't moved for 5 minutes or so.
Most steppers are rated for operating temperatures in the 80C range, some for substantially more than that, but those temps will cause the filament to soften and bind in the extruder, especially if the drive gear in the easystruder isn'y perfectly aligned with the exit path.
If it's running at 90C I'd still drop the drive current in the firmware, if it doesn't lead to skipping, there is no real loss. But given you bough the assembled one, I'd talk to support and get there suggestion.