Plastic chips accumulating in a mini hyena

[Guillaume Seguin]

Hi group,

I've been having issues with mini hyenas (tried with 3 of them, so
it's not a specific bolt problem but more likely to be a problem with
my setup) where plastic chips start accumulating after a few minutes
of print, soon leading to gripping issues.

I checked manual extrusion hardness, and it's quite easy to push
filament by hand through the hotend. It also seems I can manually
extrude fine for a while, though I haven't tried for more than a few
minutes.

As the mini hyena is not perfectly aligned with the filament path (the
filament is too far from the hyena, it is correctly aligned with the
hyena's hole (the misaligment is radial, not axial I think)), I'm
wondering if that could be the problem, or if I'm tightening the
filament too much (or not enough). Another guess might be that my
extruder motors (the 1:50 geared steppers from 2engineers.com) are
running too hot, thus making the hyena hot as well, that might have
side effects on the grip (not sure about that at all, just a wild
guess).

Has anyone experienced such issues in the past ? I'm using 3mm ABS
filament with a J-Head hotend that worked wonderfully with a PG-35L
and a drive gear from trinitylabs from last year.

Laszlo suggested the following steps:
1) extrude by hand and check if it's not too hard (done, it's not hard)
2) trying to print way above the bed (so that the pushing pressure is
not changed by the material below)

I'm going to attempt 2) soonish, and I'm going to try to print a new
extruder body with the hyena more aligned with the filament path and
will report soon, but I'd be happy to hear from others who had
accumulating plastic chips or who are using the 1:50 steppers from
2engineers !

Thanks for the help !

Best,
Guillaume

[Guillaume Seguin]

Oh and also, is it a good idea to use an acetone bath to clean a hyena ?

2013/8/13 Guillaume Seguin <guil...@segu.in>:

[Laszlo KREKACS]

Hi,

One remark:
I tried PG-35L motor in the past, and I could never get reliable
printing with it.
It is just too weak.

As a bandaid you could try to cool the motor itself with a fan.

and one (wild) guess:
Maybe the motor gets too hot, conducting the heat to the mini hyena,
making the filament
soft, and that cause the bite.

Would be interesting to see with active cooling outside the machine
(ie. airflow, and no heated bed).

But the general advise is get a better motor.
I used successfully planetary gearhead stepper motors in the past
(and still in operation on a machine, just crazy expensive).

Cleaning with acetone is fine. But I dont think its quicker.

Oh, and another idea. Mark with a marker/pen where it starts on the
hyena biting into the filament.
Maybe it starts always at the same spot, and it has a damaged tooth there?


Best,
Laszlo

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[Guillaume Seguin]

2013/8/13 Laszlo KREKACS <li...@arcol.hu>:

> Hi,
>
> One remark:
> I tried PG-35L motor in the past, and I could never get reliable
> printing with it.
> It is just too weak.
>

Well it was working fine before (printed with 6 months with it a ton
of things) but anyway it's not the motor I'm using now (42BYG48HJ50,
http://www.2engineers.com/shop/geared150/) which should work much
better and not melt over time as the PG-35L. The PG-35L was actively
cooled though, not the new one.

> As a bandaid you could try to cool the motor itself with a fan.
>
> and one (wild) guess:
> Maybe the motor gets too hot, conducting the heat to the mini hyena,
> making the filament
> soft, and that cause the bite.
>
> Would be interesting to see with active cooling outside the machine
> (ie. airflow, and no heated bed).

I'll try cooling the motor and printing without heatbed asap.

>
> But the general advise is get a better motor.
> I used successfully planetary gearhead stepper motors in the past
> (and still in operation on a machine, just crazy expensive).
>
> Cleaning with acetone is fine. But I dont think its quicker.

Well my hands are a little shaky so it's not super trivial to clean
it with a needle, acetone is a more passive way that would get it done
for me :) I'll try it.

>
> Oh, and another idea. Mark with a marker/pen where it starts on the
> hyena biting into the filament.
> Maybe it starts always at the same spot, and it has a damaged tooth there?

Well I tried with 3 different mini hyenas, they can't all have a
damaged teeth can they ? But I'll try that !

Guillaume

[nop head]

I clean hobbed bolts with a steel wire brush. Much quicker and easier than with a pin (which I used to use).

[Ante Vukorepa]

I use both. The wire brush helps, but often leaves plastic stuck in the corners of the teeth, which i then dislodge with a needle.

Not sure if the new geometry of the teeth makes plastic get caught in the corners less often, though, this is on an old Hyena. If so, brush should suffice, like nophead says.

[nop head]

That's a point, there aren't really any corners with the conventional hobbed bolt I use.

[Guillaume Seguin]

One more bit of information: here's a picture of my setup:
https://lh6.googleusercontent.com/mS5hjq4PmJgvkH5pZYj4C0C5jjOSzEDWIZ7w592m5A0y03LLEfcShxKzMJlmxFZX7Q=w1600
I'm wondering if the filament is not itching on the extruder filament
path due to the misalignment.

2013/8/13 Guillaume Seguin <guil...@segu.in>:

[Michiel Haisma]

My suggestion:

Decouple your extruder motor.
Heat up your hotend.
Now turn the hyena by hand. This should be possible! I suspect you wont be able to do this because the hyena is has a too small diameter for this setup. This causes the idler bearing to -bend- the filament towards the hyena. That bending causes immense friction. Also this explains why you are fine pushing it in by hand (with loosend idler).
To fix this, the holes for the filament need to be aligned better in respect to the place the hyena will grab it.
Hope this helps.

Regards

Michiel

Guillaume Seguin <guil...@segu.in>schreef:

[Guillaume Seguin]

I'll try your suggestion (though I'm not super sure on how to decouple
the motor, it seems to have a ton of torque even when unpowered).
Thanks !
I've already updated the extruder design to correct the bending
problem, I just need to succeed at printing it now ^^

Thanks for the helpful feedback :)

Guillaume

2013/8/13 Michiel Haisma <michie...@gmail.com>:

[Ronald Aldrich]

Guillaume,

When I designed http://www.thingiverse.com/thing:24219 , I found that the filament path needed to be changed a bit in order to fit the mini hyena, or the friction in the extruder would be too high for it to work properly.

That design includes a semi-conical filament path, which allows it to be used with either the mini hyena, or other drive gears.

- Ron

[Laszlo KREKACS]

Guillaume,

Any news to share?

Best,
Laszlo

[Guillaume Seguin]

Hi,

I just fixed my extruder design issues this morning and was able to lower motor current since friction was greatly reduced, reducing the temperature of the bolt. I still had a few chips accumulating on my test prints, but that could be due to extra idler tightening. I'll retry with a clean hyena asap.

Guillaume

[Laszlo KREKACS]

Hi,

Was the hyena basically hot, because of the overheated motor?
Do you know, that when the motor is overheated it skips steps more
easily? (ie. loose its torque).

Also the new hyena has more torque, then the old one, but it also
means, once it starts accumulating chips,
then it loose the torque greately. That is why it is vital to keep the
hyena clean for problem-free printing.

I'm happy about your progress.

Best,
Laszlo

[nop head]

Motors shouldn't loose much torque when they get hot when driven with a constant current. The resistance increases but that should only affect the high speed torque and extruders run pretty slowly.

[László KREKÁCS]

On Sat, Aug 24, 2013 at 6:31 PM, nop head <nop....@gmail.com> wrote:
> Motors shouldn't loose much torque when they get hot when driven with a
> constant current. The resistance increases but that should only affect the
> high speed torque and extruders run pretty slowly.

Maybe it was a placebo on my side. But my experience was like this:
Motor started to heating up, and loosing steps. But maybe it was just
above the torque, and the heat just affected something (filament?).

Anyway it is always a good thing to avoid overheating.

Laszlo

[nico...@gmail.com]

Thermal protection maybe?

[Ronald Aldrich]

On Aug 24, 2013, at 1:13 PM, nico...@gmail.com wrote:

> Thermal protection maybe?

If you're using 4pi or smoothieboard to run the printer (both of which have programmable motor current, rather than trim pots), you could attach a thermistor to the motor, and use it to auto-adjust the motor current.

Of course, that would be pretty extreme overkill, since once motor current is set correctly, it should never need to change.

- Ron