Brief observations on calibration, skeinforge

[Andrew Plumb]

Hey Everyone,

If you're currently engaged in mortal combat with your v2.1/2.3 firmware MakerBot, here are some quick notes from my own battle yesterday evening with the Ottawa ModLab's batch 13 cupcake:

- If you have calibrated your thermistor, chances are high that 220C will work great and 240C (the Skeinfox default) may cause you all manner of grief. If manual control-panel extrusion works but you're having problems getting your gcode builds to even start printing, try rolling down the temperatures to 220C.

Best I can figure, the ambient environment (room temperature, slight breezes, etc) was cooling the nozzle too quickly for it to maintain a 240C steady state temperature. Touching the nozzle with metal pliers or tweezers while cleaning away ooze, even for a barely a moment, dipped the temperature significantly.

- Turn off oozebane in skeinforge. The new firmware-controlled equivalent does the same thing, and trying to build with oozebane'd gcode made the finer details look like crap. Also, not having all the extra short, software-based reversal commands in the gcode might help reduce some of the communications-related issues others have seen when building directly over slow-serial instead of via SD card buffer.

Andrew.

--

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

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

[peterr]

my 2Cents:

240° is always to hot... i dunno why it's suggested on various
resources, but i never been able to print anything smooth with 240°.
When i print i heat up to 225° , and 220° during the build.

I just attached a huge pair of metal pliers to my nozzle, and didn't
see a decrease in temp...
just for the fun of it, i put them in the freezer for a few minutes
and again attached it to the nozzle - no temp flux again...
i have put a fan on my head before (big 9x9cm pc fan), and noticed 3°
temp decrease during the build... around 4-5° when not printing.
Had a room temp of 20° at that time...

[Tox]

Sounds like you've insulated the heck out of your head - mine would
freeze up whenever the air currents changed direction in my garage (no
insulation, was having a hard time keeping it in place).

Congratulations on the stability!

Tox

[MakerBot Space2]

Who is using the heated build platform in this discussion? Please
raise your hand. When printing without the heated build platform in
a cold room the ends of my raft curled up for reference say 65 degrees
Fahrenheit - I raised the room temp to 98 degrees and had nice flat
ends. At the MakerFaire this year, in a cold drafty hanger, I watched
as Bre cranked out bottle opener after bottle opener with a cold
draft. Both machines had heated build platforms - if you want to
eliminate cold air issues get the HBP.

BTW - I agree 240 is too hot - I got a ptfe bulge @ 240 - however I
suspect people running 240 successfully are out of calibration.

Thanks

Brandon

[ddurant]

> BTW - I agree 240 is too hot - I got a ptfe bulge @ 240 - however I
> suspect people running 240 successfully are out of calibration.

I agree.. I think a new & improved extruder firmware, a repg with some
bug fixes and getting everybody up to the latest versions with the
correct PID versions and such would make much of the temperature talk
go away.

> > > Me:http://clothbot.com/wiki/- Hide quoted text -
>
> - Show quoted text -

[Andrew Plumb]

Just to clarify, the extreme temperature sensitivity was at 240C; 220C was fine/normal. At 220C there's probably enough headroom for the heater to overshoot and compensate for instantaneous variations.

Andrew.

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[peterr]

i do use a heated build platform, but that's to battle warping... not
to stabilize temp flux on the nozzle end...
i'm not sure why my heads are so 'stable', because all i really ever
did was follow the wiki to the letter...
it even states how many layers of kapton to use...
as a test, i just experimented with my nichrome wire, and the
makergear heatercore - both give me identical results...
from what i can gather ALLOT of people are having problems with
placing the nichrome wire on... i'm guessing about 50% of the people
are wiring it too high up the barrel hence loosing temperature
consistency...
next time i rebuild a head i'll take foto's of each step...

240° nozzle end, would heat up the nichrome to around 270°... PTFE
gets messed up at around 250°... simple math...
240 HAS to be miss calibration :-)

discussion and opinions solve problems, so let's keep at it! :-)

Peter

[Rick Pollack]

240C resulted from using the big beaded thermistor beta (4066) for a small beaded thermistor. It is discussed in detail here.

[Len Trigg]

At one point skeinfox configurations were using 240 for ABS (I'm not
sure if they still do, but it's the first thing I changed when I
pulled out it's embedded version of skeinforge for use on my linux
box).

Cheers,
Len.

[Jordan Miller]

agreed. picking a default in general is tricky when the desirable
temps vary so much from machine to machine.

for those wondering: we picked a default that is "safe" for non-
calibrated machines fresh out-the-box for the machine and operator
sanity. the dearth of reports of shattered insulator retainers due to
skeinfox defaults, I think, says it is better that we picked it too
hot rather than too cold =]

240 on an uncalibrated machine has never given me fatal problems, on
either abs or pla 4042D. but now I'm back down to 220 for abs and 210
for pla to minimize chance of stalling while also minimizing
tremendous oozing (and because we've rebuilt the extruder several
times, with all manner of different sized thermistor heads).

jordan