Heating zone too small with makergear heatercore?

[minutilabs]

Hi there,
I've been in the long process of getting #1095 up and running. I
initially got it all set up, printed two completely uncalibrated
objects, and then oozed my PTFE barrel and broke my insulator
retainer. I'm using ABS, btw.
As per the suggestions seen here (and everywhere else), I ordered a
PEEK barrel and spare retainer from makergear, as well as a
heatercore
and a few miscellaneous odds and ends. I think it was the "enhanced
pack" or something like it. The PEEK barrel and retainer are
beautiful
and strong, the modular thermistor and heatercore are a must
(seriously, why isn't a modular design the standard?), and everything
looks much nicer and is easier to work on.
However, it seems like my heating zone is too small. When I back the
filament out after failed extrusion, I have something between 5-10mm
of melting area. I'm aware that the PEEK barrels aren't as insulative
as PTFE, so I have the metallic insulation wrapped around the PEEK,
and the ceramic cloth stuff wrapped around the nozzle and heatercore.
Is this correct, or am I missing something here?
Any tips on how to fix this? I'm dying to get my 'bot printing stuff
and to get my hands dirty helping on reprap development.

[Rick Pollack]

Hey Matt -

Let's work through this...there is no issue with the size of the heat zone...so let's see what's going on...

Is your HeatCore twisted tight against your nozzle and getting good thermal contact? Is the thermistor taped to the nozzle? A photo with the insulation off would help.

What temp are you using for ABS and describe how it fails...does it run for a few minutes...does it fail immediately...etc. Can you extrude from control panel? What is the diameter of the filament you are using? And the diameter of the filament coming out of the pinch wheel? If the filament is getting really squished by the pinch wheel, it can get stuck in the PEEK. The internal diameter of the PEEK opening (after the bevel) should be 3.35mm. Can you easily slide a piece of squished filament into the insulator?

If you can, please post a photo of your hot-end (insulation off) and some backed out filament. Also, you may want to take a look at the SuperPack instructions to see how I assemble a Plastruder.

Rick

[Rick Pollack]

Also,  you probably received a larger thermistor ("3mm")...you should be using a beta of 4066.

[Matt Minuti]

I just verified, the HeatCore is tight against the nozzle, and as far as I can tell gets good thermal contact. Everything looks pretty much just like in the SuperPack link.

The thermistor is taped to the nozzle, halfway down the nut for a good measurement balance. A photo is attached.

ABS extrusion fails immediately. I started at 230C, let it reach the temp, waited 10 minutes to be certain, and fed filament forward from the control panel. No plastic came out, and the idler wheel stopped spinning, indicating stripping or jamming. Reversed for a second or so. Set to 240C, repeat, same results. I tried it at 245C briefly, but I didn't want to break anything so I didn't let it wait long.

My caliper isn't the greatest, but it's looking like it says the filament is 3.05mm. After going through the pinch wheel, I'm not seeing a difference. I'm using the MK5 pulley, so that might account for less squish.

The PEEK opening is 3.35mm, as far as I can tell. A squished (or post-pinchwheel) piece of filament easily fits inside.

A picture of some backed-out filament is also attached.

And yes, I have a 3mm thermistor, and I'm using a beta of 4066.

[minutilabs]

Almost forgot, I have a multimeter with a thermocouple I can use to
verify temperatures, provided I know where to be sampling!

>  2010-06-05 11.55.21.jpg
> 407KViewDownload
>
>  2010-06-05 12.10.11.jpg
> 478KViewDownload

[Rick Pollack]

This is odd. Couple of things to try/check.

1) Loosen the pinch wheel so that you can push the filament through by hand.  Set the temp at 220C and after it gets to temp give it one more minute and then start pushing the filament through. What happens?

2) What is the resistance of the HeatCore and the thermistor at room temp?

3) Is it possible your pinch wheel and idler are not aligned? When the ilder stops turning is the motor stopped or did it strip the filament?

Rick

[Rick Pollack]

Also, which firmware are you using?

[beak90]

The barrel might be clogged from something. If you made the
temperature too high on accident, it could have burned the ABS and
caused a jam. Try cleaning the barrel and nozzle really well. Check
out this link for more info on cleaning: http://wiki.makerbot.com/burning-plastic

On Jun 5, 9:45 am, Rick Pollack <r...@makergear.com> wrote:
> Also, which firmware are you using?
>

> On Sat, Jun 5, 2010 at 12:43 PM, Rick Pollack <r...@makergear.com> wrote:
> > This is odd. Couple of things to try/check.
>
> > 1) Loosen the pinch wheel so that you can push the filament through by
> > hand.  Set the temp at 220C and after it gets to temp give it one more
> > minute and then start pushing the filament through. What happens?
>
> > 2) What is the resistance of the HeatCore and the thermistor at room temp?
>
> > 3) Is it possible your pinch wheel and idler are not aligned? When the
> > ilder stops turning is the motor stopped or did it strip the filament?
>
> > Rick
>

[Matt Minuti]

Cleaned out the barrel, there was a bit of discolored plastic. I was able to manually feed filament through at 220C, it was tougher than expected, but ended up flowing smoothly. I also double-checked the idler wheel and it looked slightly misaligned. Once I staighten that out, I'll post back with my updated progress. Thanks so far, everybody!

On Jun 5, 2010 5:46 PM, "beak90" <bea...@gmail.com> wrote:

The barrel might be clogged from something. If you made the
temperature too high on accident, it could have burned the ABS and
caused a jam. Try cleaning the barrel and nozzle really well. Check
out this link for more info on cleaning: http://wiki.makerbot.com/burning-plastic

On Jun 5, 9:45 am, Rick Pollack <r...@makergear.com> wrote:
> Also, which firmware are you using?

>...

> On Sat, Jun 5, 2010 at 12:43 PM, Rick Pollack <r...@makergear.com> wrote:

> > This is odd. Couple ...

> > On Sat, Jun 5, 2010 at 12:16 PM, minutilabs <matt.min...@gmail.com> wrote:
>

> >> Almost forgot,...

[Matt Minuti]

It extrudes! Probably was a combination of gunked-up barrel and misaligned idler. To make sure, I had the bot make delicious ABS spaghetti for about 5 minutes straight, it kept up without a hitch, and held right on temperature!

On to skeinforge calibration!

Thank you so much!

[Matt Minuti]

1) It won't go through. It seems to be hot enough, because I can stick the .4mm brass wire into the nozzle tip and the plastic inside is molten. I left the filament there for a minute or so, pulled it out, and it was beautifully melted at the end and pulled a long string. 

2) Current room temp here as measured by my meter is 31C. Heatcore resistance is about 6.3Ohms. Thermistor resistance is 82.0KOhms. Reading the temperature from the control panel gives me 34C. Maybe a sign of something amiss?

3) The pinch wheel and idler appear to be aligned. It seems like the motor stops turning, since there's some chewing on the filament but not enough to be completely stripped.

4) Plastruder 2.3r1, Reprap motherboard 2.1r1

[Rick Pollack]

It can be hot enough to melt but not extrude. Have you tried mb firmware v1.4 or v1.6 and controller v1.8?

Rick

[Andrew Plumb]

Since you have the thermocouple, take some measurements at your target melt temperature as well. All the room-temperature reading tells you is that your thermistor is in right ball-park (compared to an accidental 10K thermistor).

Try the two-pass calibration method I captured to the MakerBot wiki (scroll to the bottom):

http://wiki.makerbot.com/adjusting-the-thermistor-settings

Aside: setting the PID settings properly is critical with the v2.x firmware.

Andrew.

--

"The future is already here. It's just not very evenly distributed" -- William Gibson

Me: http://clothbot.com/wiki/

[Rick]

Matt - any status on this?

Rick

On Jun 5, 1:43 pm, Matt Minuti <matt.min...@gmail.com> wrote:
> 1) It won't go through. It seems to be hot enough, because I can stick the
> .4mm brass wire into the nozzle tip and the plastic inside is molten. I left
> the filament there for a minute or so, pulled it out, and it was beautifully
> melted at the end and pulled a long string.
>
> 2) Current room temp here as measured by my meter is 31C. Heatcore
> resistance is about 6.3Ohms. Thermistor resistance is 82.0KOhms. Reading the
> temperature from the control panel gives me 34C. Maybe a sign of something
> amiss?
>
> 3) The pinch wheel and idler appear to be aligned. It seems like the motor
> stops turning, since there's some chewing on the filament but not enough to
> be completely stripped.
>
> 4) Plastruder 2.3r1, Reprap motherboard 2.1r1
>

> On Sat, Jun 5, 2010 at 12:45 PM, Rick Pollack <r...@makergear.com> wrote:
> > Also, which firmware are you using?
>

> > On Sat, Jun 5, 2010 at 12:43 PM, Rick Pollack <r...@makergear.com> wrote:
>
> >> This is odd. Couple of things to try/check.
>
> >> 1) Loosen the pinch wheel so that you can push the filament through by
> >> hand.  Set the temp at 220C and after it gets to temp give it one more
> >> minute and then start pushing the filament through. What happens?
>
> >> 2) What is the resistance of the HeatCore and the thermistor at room temp?
>
> >> 3) Is it possible your pinch wheel and idler are not aligned? When the
> >> ilder stops turning is the motor stopped or did it strip the filament?
>
> >> Rick
>

[minutilabs]

I'm sorry, I thought I had replied with my findings earlier, maybe it
didn't go through!

The idler wasn't quite aligned right. I added a washer to enforce good
alignment, and it worked wonders. All my temperatures have been right
on, and I was able to produce about 6 or 7 decent prints while I
figured out some skeinforge settings.

I installed my HBP and that's been great, but I must've knocked
something because I'm having stripping issues again. Definitely wasn't
the heater at all though.

Thanks for all the help!

[Rick Pollack]

Can you use your thermocouple to to read the temp just inside the heater barrel where it meets the insulator? There is usually some plastic at the junction and you can push the end of the thermocouple into it.

[Matt Minuti]

What do you mean "just inside?" Do you mean dismount the extruder so that I can stick the thermocouple down the barrel, as if it were filament? And what do you mean by insulator?

[Rick Pollack]

I just mean run your thermocouple down through the filament movement mechanism and into the PEEK insulator (you are using PEEK, right?) and then get a temperature reading just where the brass and PEEK meet. The washer is a big heat sink and if the temp there is too low then filament will get stuck. That's the reason we eliminated the washer...

You don't need to take anything apart.

Also, your temp settings in skeinforge are correct? what temp are you using again?

[Matt Minuti]

After warming to 220C and holding it there for about 5 minutes, I can feed the thermocouple down into the PEEK almost exactly halfway before I hit plastic. squishing it into the plastic a little bit and waiting another 5 minutes gives me a pretty stable reading of 164C. Seems like I should put some extra insulation back around the PEEK?

Temp settings in skeinforge are correct. 220C, no raft, build platform at 125C on lightly sanded kapton. About an hour ago I stripped the filament just extruding in the control panel, so I know it's not skeinforge this time.

[Rick Pollack]

Is the tip of your thermocouple just inside the brass or still in the PEEK? The PEEK is threaded for 15mm. The temp at that junction, iirc, should be at least 180C. What happens if you try to extrude at 230C?

I've never needed to put insulation around the insulator :) Do you have insulation around the heatcore and nozzle?

[Matt Minuti]

Seems like it's in the brass. The thermocouple goes in past the top of the PEEK approx 2.25cm. I'll try extruding at 230C after lunch.

Yes, I have insulation around the heatcore and nozzle. The white ceramic fabric stuff included with the enhanced pack.

[Andrew Plumb]

What PID settings are you using for the heater?

--

[Matt Minuti]

P: 7.0

I: 0.34765625 (floating point weirdness, I think it was supposed to be .35)

D: 36.0

[Matt Minuti]

Thermocouple says that the same spot in the PEEK is 176C when I have the temperature set to 230C, allowed to stabilize for 5 minutes. Extrusion works well, I extruded for 3 minutes or so without any signs of irregularity or stripping.

Should I just be running at 230C instead of 220C?

[Rick Pollack]

You might want to try taping your thermocouple next to your thermistor on the nozzle and get that temp. Figure out what temp gets the top of you barrel to 180C and then try use that to print an object...

Also, you may want to try and insulate your washer or where your washer meets your heater barrel and see of that helps.