Extruder Stepper Too Hot

I wanted to know if anyone else is having this problem.

After many problems with cheap cloned extruders, and endless jams I went with a E3D 1.75 hotend using bowden air tripper and MK8 gear. Seems this configuration works for me. However, I do use PLA which gives me a problem jamming at the cold end. After an hour of printing the stepper gets so hot that the heat transfers to the pulley and then deforms the filament and stops feeding. I am using a NEMA 17 stepper 33 oz-in with Ramps 1.4 & A4988.

The obvious answer is add a fan but where? point at the stepper body or right at the drive gear?

Thanks/

Actually, the obvious answer is turn down the current to that motor. You have a geared extruder- you should not need to run a lot of current in the motor. Even direct drive extruders only get warm when running. My geared extruder uses 600mA and barely rises above ambient temperature after multiple hours of printing.

The problem with A4988 modules is the tiny pot that adjusts current- it's easily broken- so be careful. The other problem is you never know what the current is actually set to. You're going to have to just try turning it down (counterclockwise) and see how it goes. If it starts skipping steps you'll have to bump the current back up again.

Yeah, and while you're at it, try not to short out the stepper drivers. Use a ceramic screwdriver by preference

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http://www.marinusdebeer.nl/

...Maybe I should do the same. Im running a direct extruder (gregs) with 3mm ABS and my extruder gets so hot you cannot touch it!

Quote

The other problem is you never know what the current is actually set to

Well, unless you actually measure it (which is easy enough to do)

The Pololu website gives you the procedure, you measure vRef from the metal dial of the pot, and any ground on the stepper or RAMPS, using the formulae:

I (current limit) = Vref x 2.5

So for example, a measured Vref of 0.52 volts = 1.3 A

The A4988's can provide up to 2A (more than many of the motors we use can take), so the aim is to keep current high enough to stop the motors binding (more current equals more torque), but not so high that overheating becomes an issue.

Just be aware though, too much current, and not enough current, can both have the same symptom in your print (missed steps). Too little current can produce too little torque, so the motor skips steps, too much current for the A4988 will cause it to overheat (unless you have effective active cooling on the steppers) so its thermal cut-out kicks in (producing missed steps). 

Edited 1 time(s). Last edit at 02/10/2015 03:47AM by plankton.

Thanks so much to everyone that responded. I had turned the current in the past but thought that I was as low as I could go. You guys are awesome, turned down the current even more and now the motor is barely warm after an hour of printing. Saved me so much frustration and now I'm ready to enjoy printing.

Thanks again.

Also: I'm on the same setup (Airtripper Mk8 Bowden, , E3D 1.75) and I have a huge CPU heatsink/fan glued to the motor. If you have a computer thrift shop near you, go pick up a cheap used heatsink. If not, even a small active heatsink, like the $5 ones on eBay, helps a ton.

I was at about 80-85c on my extruder after a 30 minute print.
WAY too hot to touch.
My X and Y also get so hot you cannot touch them.

my exstruder stepper is from a scanner, and the gear drive is too. Such a tiny motor does need fan forced cooling and it stays at 30 degrees celcius.. It runs a bowden exruder so there is extra friction. Other than that, the rest of my printer steppers usually measure about 5-10 degrees celcius.

Another update. I ended up getting more jamming and the plastic would shred. I went from a 33 oz-in to a 78 oz-in stepper. Supposedly the airtripper requires more torque from its motor than the 33 oz-in. The bonus of this is the bigger motor is it stays cool, have yet to feel any heat on it and so far no jamming or missing steps.

The 78 oz-in NEMA 17 stepper was only $16 with no shipping on ebay. It's worth trying for the extruder.

Hope this helps.

I dialed mine back a little and its a bit cooler. Only a little above room temp after a big print. No missed steps or anything.

i dont get it.
I replaced the mainboard from a makerbot replicator 1. I keep using the 24V with new DRV8825 driver . The vref for the extruder is set at 0.3V so its below the accaptable 0.4V (0.8A per coil are allowed for the stepper... ). However the motor gets really hot!
I am useing Marlin 1.1.4 any suggestions ? i really hope i dont need to add an extra fan... .

Edited 1 time(s). Last edit at 08/07/2017 11:25AM by kakawuwu.

The motor torque and temperature are proportional to current. Turning the current down will reduce the torque and the temperature rise. As long as you have enough torque to extrude reliably, it's OK to turn the current down.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Thanks that is a good advise. The torque is dependent von the chipwheel /cog size. thus a smaler wheel could increase the torque while having a redurced current?!

Yes, a smaller diameter drive gear would effectively increase torque, or allow equal torque at lower motor current.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]