Extruder not extruding consistent lengths of filament

[GITRDUN]

I went to recalibrate my extruder and discovered that it is extruding
at different lengths every time i hit the extrude button on
pronterface. Extruding at 400mm/minute, 1.75mm PLA with the geared
motor direct drive unit. No slipping or binding going on with the
motor and filament, it just stops short or long every time. Varying by
up to +/- 5mm from one extrude to the next over a distance of 90mm.

[jay.c...@gmail.com]

Sounds like filament is slipping.
Increase the idler spring tension and retest. Otherwise, suggest you recalibrate without the hotend. Try to add some resistance to the filament to create missed steps. Increase the motor current until there is no missed steps.
Sent on the Sprint® Now Network from my BlackBerry®

[Rick Pollack]

try 220mm/min

[GITRDUN]

I was getting bad slipping and filament stripping above 500mm/minute.
At 400mm it doesnt slip or strip at all. Allready checked that. Also
upped the pot on the pololu driver until the motor started growling
and ocsilating then reduced it until it settled down and wasnt running
too hot. I will try again at a much lower speed but at this point im
90% sure the filament is not slipping.

[Rick Pollack]

make sure he drive pulley is not loose

[GITRDUN]

Rechecked a few times at 200mm/m , same results. I cant figure it out.
I pulled everything apart earlier to check for mechanical problems but
didnt find anything loose or looking amiss. I can still print with it
but no way to get it to print perfect prints anymore. The solid layers
really show the problem, it prints like a dream then all of a sudden
it either leaves cavities from not enough filament or it lays down to
much and mushes it around.

[Rick Pollack]

what temp? and are you using the default firmware?

[ddurant]

Did the filament come from a reliable source? Maybe take a bunch of measurements across a meter or so of it and look for variations in the diameter..

[sto...@gmail.com]

Along with Dave D,

I've used a fare variety of colors/plastic this last year. But, I have one black plastic coil that will not print more then a few inches at a time. I do have another coil of black that prints beautifully.

Suggestion: Switch up your plastic and know that, at this time in development, a reliable source may occasionally send you a poor batch. FWIW

[sto...@gmail.com]

If it prints at 400mm per ? and not at 500mm per ? Then, maybe you are exceeding the melting capability of your hotend. Within our 3D printer realm there may now be a need/want for a faster responding heat source? I am seeing - as the extruder pushes plastic into the extruder the temp. fluctuates. Higher temps. work for a short range on some plastics and faster print speeds but, then begin to cause their own problems.

As the filament extruder delivers plastic to the hotend the hotend's temperature drops and can drop below the melting temperature of the plastic. When, this happens the filament begins to strip and the plastic no longer extrudes. Our temperature indicators have a sample rate. I would guess the sample rate may not be fast or often enough to show the dip below optimum melting temp.?

Question: Is hotend PID still being used to adjust extruder temps.? Now, may be a time to revisit settings? Also, switch to a finer filament to print with at faster speeds?

The plastic filament does have cross sectional area which needs to be melted. If you exceed the hot ends capability to melt to the core then you will not be able to extrude.

Rick (and/or others) could design/build a longer heated hotend melt zone to accomodate the higher volumes of melted plastic needed at higher print speeds. Note: I've seen the design of an industrial extruder and they have a long pre-heat and melt zone. Our little hot glue guns (printers) can't just melt instantly at any speed. (Hmmm, maybe the cause of some faulty filaments? Maybe faulty plastics are denser? Denser filament can't presently be melted fast enough to print with? Yes? Then, we need evolved hotends.) I learned from my real hot glue gun that I sometimes can not squeeze it out as fast as I'd like to use the glue. It just will not melt fast enough. :-)

Disclaimer: If I am wrong I did not read the entire string. If I'm onto something then, "Whew!", that was lucky. ;-)

----- Reply message -----
From: "GITRDUN" <cray...@gmail.com>
Date: Fri, Jun 1, 2012 8:12 pm
Subject: [MakerGear] Re: Extruder not extruding consistent lengths of filament

[GITRDUN]

I am extruding at 175~185C. Ive went up to 205 and down to 160. I am
using Sprinter firmware. Same firmware ive had since day one.

I checked the filament dia over a dstance of 3' and its .168"
consistently.

To reiterate , the FILAMENT IS NOT SLIPPING OR STRIPPING in the
extruder and the motor isnt stuttering or being oveloaded, thats why
im having trouble figuring out whats up.

With that said it almost has to be related to the electronics side of
things but it just makes no sense.

[Rick Pollack]

if you watch the extruder motor, can you see anything obvious like it is stuttering? Have you tried swapping stepper drivers?

Are you using the firmware that shipped with the printer?

[Rick Pollack]

what is that diameter measurement again? (.168" can't be right)

[GITRDUN]

Sorry, youre right. Its not .168" its .068" which is roughly 1.75mm .
I hadnt thought of swapping stepper drivers but i will try that. The
motor runs smooth as silk when extruding, no cogging no stuttering no
strange noises or anything. The firmware shipped with the printer? I
bought the Makergear prusa kit, there was no firmware or software
shipped with it. Instructions werent exactly much help either, its
difficult for a beginner to understand how it all goes together when
everything is explained in expert terms and vague explanations if its
explained at all. I was in the middle of making a wades extruder when
the problems arose. If i could at least get a good enough print to
finish it i could set it up and start the process of elimination.

On Jun 2, 10:27 am, Rick Pollack <r...@makergear.com> wrote:
> what is that diameter measurement again? (.168" can't be right)
>
>
>
>
>
>
>
> On Sat, Jun 2, 2012 at 11:25 AM, Rick Pollack <r...@makergear.com> wrote:
> > if you watch the extruder motor, can you see anything obvious like it is
> > stuttering? Have you tried swapping stepper drivers?
>
> > Are you using the firmware that shipped with the printer?
>

[Rick Pollack]

it shipped with firmware for the electronics. what firmware did you put on?

[GITRDUN]

I am running sprinter. I have no idea what firmware youre talking
about that shipped with the printer. Are you saying that the mega 2560
was preloaded with firmware? What firmware do you reccomend and what
is supplied with the printer?

[Rick Pollack]

Yes, there was firmware on the mega. The firmware for the prusa is pinned to the top of the google group. There is a 14:1 and 5:1 version. It is sprinter.

[GITRDUN]

I think i may have the problem resolved. I got to thinking about when
the printing trouble popped up and it was about the time i connected
the printer to a mini laptop i had purchased to use for the printer
alone. So i connected my old laptop to it which is what i had used
origionaly and ran a print at 80mm/sec feeds and so far the first 10
layers look as amazing as ever. I have tried and tried to run the same
print with the mini laptop to no avail for a week now. The best
results i could get were with feeds at 30mm/sec and even then i kept
getting blobs of filament, horrible strings and cavitys from not
enough filament. The mini laptop has an old 700mhz processor and i
have a feeling the communication just wasnt able to flow fast enough
or correctly. I did have the port settings set to match the printer so
it wasnt faulty setup as far as i can tell.

Anyways, if the print turns into muck before its done ill post it but
if not then all is back to normal and lesson learned. Thanks for the
support assistance.

[Rick Pollack]

you can get an sd-card add-on for ramps then you should be able to use the mini laptop

[Triffid Hunter]

On Sun, Jun 3, 2012 at 1:42 PM, GITRDUN <cray...@gmail.com> wrote:

The best
results i could get were with feeds at 30mm/sec and even then i kept
getting blobs of filament, horrible strings and cavitys from not
enough filament. The mini laptop has an old 700mhz processor and i
have a feeling the communication just wasnt able to flow fast enough
or correctly.

this sounds to me like pronterface spending too much time doing graphics and not enough time sending the file. there should be a way to turn off the gcode display and I suspect that'll help massively.

Think about it, why would a 700MHz 32-bit processor have trouble sending a file down a serial port fast enough to keep up with a 16MHz 8-bit processor?

may also be worth your while looking up some of the really simple terminal-mode senders like send.py or the bash scripts in teacup's func.sh

[GITRDUN]

I contemplated the SD card add on before but i like being able to see
whats going on while printing with pronterfaces features. I went ahead
and ordered a much newer mini laptop with a 1.6G processor, its just
so handy to have a stand alone computer for it. I would like to know
what exactly is causing the slow down with the 700mhz laptop, when i
first hooked it up i ran task manager and watched the performance of
the processor and page file usage while printing and it was barely
getting used so i assumed everything was good to go. It does have the
old USB port which is not the high speed 2.0 port, that could be the
bottle neck i dont know.

The print i ran last night looked excellent so it is deffinatly a
problem with the mini laptop.

[Triffid Hunter]

On Sun, Jun 3, 2012 at 11:36 PM, GITRDUN <cray...@gmail.com> wrote: 

It does have the
old USB port which is not the high speed 2.0 port, that could be the
bottle neck i dont know.

nope, the usb<->serial chip on the mega only runs at full speed, not high speed.

[Jay Couture]

Since you are on the subject, what baud rate are you running GITRDUN?

[Charles Warner]

I had a similar problem, and, somewhere here on the forum I cam across
the idea that the drive gear was getting too hot. This apparently
causes a softening of the material before it gets shoved down into the
hot end. Solved by adding a small fan blowing on the extruder head to
keep the drive gear cooled down a bit...

Charlie

[GITRDUN]

I had the baud rate set to 115200 on the com port and in Pronterface.

I put a fan on the X carriage to blow on the extruder long ago as i
was getting jam after jam from the filament swelling in the nozzle
while sitting in between prints. I havent had a single jam since.