Extruder Choking... (PIC Inside) Need Your Thoughts

Hi All,

I am perplexed by the behavior of one of my extruders. Here is the culprit:



It is a NEMA 17 (Wantai 42BYGHW609) driven "Eckstuder," being driven by a RepRapDiscount Ramps 1.4 board and RepRapDiscount Clone Polu Driver.

It extruded fairly well for about a week, but I noticed it skipping every once and a while. But now it does not seem to have the strength to properly push the filament. The extruder spins and stops, shudders and skips. Sometimes it will not turn at all.

Disassembling it, cleaning it, adjusting the closeness of the gears, adjusting the tension on the idler does little to help.

The hot-end does not seem to be clogged, I can manually extrude filament by hand turning the gears. (it does take a lot of force though)

I even tried switching to a different stepper driver and the problem persisted.

What is causing this?

1. Does my particular NEMA17 not have enough torque for this job?
2. Are my cheap-O chinese stepper drivers to blame?
3 Is my hot-end clogged up a bit and I am just not perceiving it?

My only thoughts right now are to get a motor with more torque and if that does not work, try a stonger set of electronics.

I appreciate your thoughts.

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FabberForge - Printing Happiness

[www.fabberforge.com]

Check your voltage to the motor. Either it has burnt your stepper out or your drivers are not giving enough juice. Also check the leads. A dry solder joint or fracture will sap power as it will act as a resister.

the RepRap discount drivers I am using have some strange properties. When bench testing them, they had to be set to .1 volts to gain any control of the motors. Got a recommended voltage reference to try? Anything too low and the motor will click back and forth. Anything to high and the motor will run then stop, run then stop. I am guessing in the latter case that the stepper driver runs, gets hot and stops.

My guess it has nothing to do with any of the components you specified and the problem lies in the hotend. If you can not push the filament in by hand then it is not working correctly.

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What hot end is it, and are you sure that the small gear on that stepper motor isn't spinning on. The shaft, what can happen is that as it heats up the pla in contact with the shaft will soften enough to allow it to slip, I would put a small mark on the stepper shaft as and verify that it isn't slipping

likely overpowering the stepper driver causes a coil inside nema 17 to short or open. replace the motor.

jamesdanielv Wrote:
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> likely overpowering the stepper driver causes a
> coil inside nema 17 to short or open. replace the
> motor.

The stepper would have gotten hot enough to soften the drive gear and bracket before that would happen.

You want those Chinese drivers set at about 200 mV reference, as opposed to the real Pololus being set at around 400 mV.

You should be able to extrude easily turning the main gear by hand, assuming the extruder motor is disabled. Otherwise it is a problem with the hotend. Are you printing with PLA or ABS? With PLA you need a fan blowing over the thermal break in the hotend, with ABS you don't.

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I am printing in PLA. There is a fan attached in the back. It has a scoop that blows on the thermal break

I will try 200 mV (I have been in that ball park)

I will also triple check if the extruder is clogged.

I don't think the small gear is spinning, but at this point I will check everything

You might want to check the diameter of the fillament feeding your extruder.

If your hotend intake is drilled to exactly 1.75mm or 3mm, the plastic fillament your using might be over that diameter.

You may be printing at too low a temperature, or too high a feedrate. The hotend may not be melting the plastic fast enough, causing it to stop and stalling out the motor.

You are print PLA, at what temperature / feedrate / layer height? Is it always jamed or does it work for a little while then jam?

CdnReprap Wrote:
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> You might want to check the diameter of the
> fillament feeding your extruder.
>
> If your hotend intake is drilled to exactly 1.75mm
> or 3mm, the plastic fillament your using might be
> over that diameter.


Filament that is under 3mm and filament that is over 3mm are both having the same problem

pfinucan Wrote:
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> You may be printing at too low a temperature, or
> too high a feedrate. The hotend may not be melting
> the plastic fast enough, causing it to stop and
> stalling out the motor.
>
> You are print PLA, at what temperature / feedrate
> / layer height? Is it always jamed or does it
> work for a little while then jam?

right now I am simply slowly extruding filament (not during an actual print) until I figure out why she is choking.

I am using PLA and trying temperatures between 200 and 220. For a moment, I thought that 220 was making the extruder more easily, but the choking persisted.

What hot-end is it and where did you get it from - it's not a J-head clone is it?

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[richrap.blogspot.com]

I FIGURED IT OUT!!!!

It was the perfect storm of multi-variable problems lol

*My EkerTech Hot-End was partially clogged
(I was able to unclog it with the cleaning kit that came with it. It is a nice Hot End BTW!)

*My Chinese Stepper drivers did not have the "juice" to power through this, so I would turn up the stepper driver current slightly

*After turning up the current on the stepper driver, the stepper motor would become powerful enough that the small printed gear would start to slip on the motor shaft.

Results of the situation were:
Regular Current To Extruder: Not strong enough to turn
High Current To Extruder: Small Gear slipping on motor shaft

I have cleaned out the extruder and am printing a new small gear on another machine now. God willing this problem will be resolved

richrap Wrote:
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> What hot-end is it and where did you get it from -
> it's not a J-head clone is it?

It is an eckertech all-metal hot-end. It seems really nice actually.