Struggle with PLA

I'm using a ressurected Thing-O-Matic Mk7. I've modded it so much it is rediculous. It prints ABS GREAT! No problems there.

I've recently been wanting to print in PLA, but have only been able to print 1 thing...a vase...barely. I keep getting jams no matter what temps I'm running, and no matter what amount of airflow I force across the 'heat gap' in the Mk7 hotend. At first I tried the popular 40mm fan. That didn't help any, so I went way overboard and printed out a setup that uses an 80mm fan. Still no change. That tells me it can't be heat creep. I'm using MakerGeeks PLA. I don't have any other PLA to try.

Is it just impossible to print PLA with the ToM?

Oh, and it isn't just an extruder issue. I get jams even when I am manually pushing filament through. At first, I am easily able to push filament through, then it just gets hard and harder to push filament through until it completely jams. Then I have to play a game of tug-of-war to get the filament out.

Edited 2 time(s). Last edit at 06/21/2014 10:05PM by MrBaz.

Do you mean the Stepstruder MK7 hot end?
[www.makerbot.com]

You might get more help on Google Groups, seems to be a lot of others are having issues with hot ends from Makerbot not working: [groups.google.com]

I'm curious, after you clear the PLA jam, have you switched back to ABS, and did it print without jamming?

THING-O-MATIC MK7 PLA SET-UP AND TROUBLESHOOTING (LIKELY MK8)
[www.protoparadigm.com]

Yes, Mk7 hotend.

I can switch back to ABS and print flawlessly.

Black PLA?

Measure the diameter of the ABS and compare it to the PLA, should be the same, or nearly so.

Natural PLA. I've input the correct measurements into my slicer, and my extruder is a spring-pressure ball bearing type. I'm using 1.75mm filament.

Edited 1 time(s). Last edit at 06/22/2014 07:30PM by MrBaz.

Quote
MrBaz
I get jams even when I am manually pushing filament through. At first, I am easily able to push filament through, then it just gets hard and harder to push filament through until it completely jams.

I find this quote perplexing. Because you can push the filament through at a high rate, enough so that heat doesn't migrate up the filament to cause a "plug" jam.

I think you should go on the Google forum, and pick their brains.

Possibly your thermistor is not potted or wiggling in the well, making intermittent contact, and temps are higher than you think. ABS can take a higher temp, temps that will cause PLA to collapse. Try potting the end of the thermistor with high temp silicone in the well.

You should take some pictures of your rig too.


Review the following parameters against your settings:

RepRap: Printing Parameters Database
[reprap.org]


PLA, (Polylactic acid, or polylactide, Type: extruded):

Drying Temperature:
Range: 45°C to 100°C, (113ºF to 212ºF)

Dry time:
Range: 4 hours.

Glass-transition temp:
Range: 45°C to 120°C, (113ºF to 248ºF).
Average: 59.6°C, (139ºF).
Wikipedia: 60°C to 65°C, (140ºF to 149ºF).

Begin testing around this temp:
Substrate/bed temperature: 60°C, (140ºF).
Enclosure temperature: 60°C, (140ºF).

Machine parameters:
Extrude temp (RepRap): 165°C ~ 200°C.
Wikipedia: melting temperature between 173-178 °C

Quote
A2

Quote
MrBaz
I get jams even when I am manually pushing filament through. At first, I am easily able to push filament through, then it just gets hard and harder to push filament through until it completely jams.

I find this quote perplexing. Because you can push the filament through at a high rate, enough so that heat doesn't migrate up the filament to cause a "plug" jam.

I think you should go on the Google forum, and pick their brains.

Possibly your thermistor is not potted or wiggling in the well, making intermittent contact, and temps are higher than you think. ABS can take a higher temp, temps that will cause PLA to collapse. Try potting the end of the thermistor with high temp silicone in the well.

You should take some pictures of your rig too.


Review the following parameters against your settings:

RepRap: Printing Parameters Database
[reprap.org]


PLA, (Polylactic acid, or polylactide, Type: extruded):

Drying Temperature:
Range: 45°C to 100°C, (113ºF to 212ºF)

Dry time:
Range: 4 hours.

Glass-transition temp:
Range: 45°C to 120°C, (113ºF to 248ºF).
Average: 59.6°C, (139ºF).
Wikipedia: 60°C to 65°C, (140ºF to 149ºF).

Begin testing around this temp:
Substrate/bed temperature: 60°C, (140ºF).
Enclosure temperature: 60°C, (140ºF).

Machine parameters:
Extrude temp (RepRap): 165°C ~ 200°C.
Wikipedia: melting temperature between 173-178 °C

I thought I had already done a temp plot test, and the results gave me the starting temp before anything would extrude was around 195*C. I'll try it again.

OK. Weird and very interesting development. In an effort to simply 'tint' my natural/clear PLA plastic during a print, I realized I could print just fine. I tried oiling the filament with canola oil, no dice. I tried wiping the filament with pledge dust wipes, still no dice. Yet, when I take a permanent marker to the filament in order to tint the clear plastic, I can print flawlessly -- even with retraction turned on!

I'm chalking this up to a poor hotend design from MakerBot as far as PLA is concerned.


My question is, what is in a permanent marker that would lubricate the filament better than me directly wiping oil onto the filament?

A very interesting development. Possibly you have coated the PLA with a resin that performs as a lubricant. What color, mfg, and amount of surface area did you coat the natural PLA?

Quote

Dear Natalie,

Permanent inks, like the classic Sharpie, contain three main ingredients: colorant, carrier (solvent) and resin (polymer). For permanence, the colorant of choice is pigments (as opposed to dyes). Pigments do not fade like dyes and do not bleed through paper. Solvents for the old markers (up until the 1990's) were nasty-smelling organic chemicals such as xylene. Nowadays, the solvent of choice is an alcohol (ethanol or isopropanol), which is more enviromentally friendly and better smelling, while still evaporating quickly to prevent messy smearing, etc. Finally, there is a resin or polymer that is added as a "binder" that promotes adhesion... A permanent resin is not permanent unless it sticks like glue to most of the surfaces it is written on. The resin forms a film (once the alcohol evaporates) that allows the ink to write smoothly and uniformly on any surface (smooth or rough) while acting like glue for the pigment. Resins come in all shapes and sizes, typically, urethane acrylic resins are used (like those used in house paints).

I Hope this is helpful.

Sincerely,

Keith Allison ("Dr. Crayola")
Senior Chemist
Binney & Smith, Inc.
[www.madsci.org]

TLDR, and don't even know what the MB hotend looks like. Just throwing out a thought while I have it- could it be that it is bad at spreading heat, and as you push through filament it is cooling it too fast for the heat to catch up and keep melting filament?
When you push it through by hand until it stops, can you wait and then resume [without pulling it back up]?

Before posting I decided to read a bit more. ABS would give the same problem if that were the case, but I'll leave that there for thought anyways.

Oil can bake, and in my personal experience it can actually increase contact [that's why I just used it to cook up my quesadilla] and as far as I know, increasing contact increases PLA's friction. A solid resin wouldn't pull the surfaces together, but simply lubricate. Oils are used for lubricating things that need to make contact, like engines and drill bits. The more solid, dry wax is used for things that shouldn't have increased contact, like the sides of saw mills and chains.

---

Realizer- One who realizes dreams by making them a reality either by possibility or by completion. Also creating or renewing hopes of dreams.
"keep in mind, even the best printer can not print with the best filament if the user is the problem." -Ohmarinus

Quote
A2
A very interesting development. Possibly you have coated the PLA with a resin that performs as a lubricant. What color, mfg, and amount of surface area did you coat the natural PLA?

Quote

Dear Natalie,

Permanent inks, like the classic Sharpie, contain three main ingredients: colorant, carrier (solvent) and resin (polymer). For permanence, the colorant of choice is pigments (as opposed to dyes). Pigments do not fade like dyes and do not bleed through paper. Solvents for the old markers (up until the 1990's) were nasty-smelling organic chemicals such as xylene. Nowadays, the solvent of choice is an alcohol (ethanol or isopropanol), which is more enviromentally friendly and better smelling, while still evaporating quickly to prevent messy smearing, etc. Finally, there is a resin or polymer that is added as a "binder" that promotes adhesion... A permanent resin is not permanent unless it sticks like glue to most of the surfaces it is written on. The resin forms a film (once the alcohol evaporates) that allows the ink to write smoothly and uniformly on any surface (smooth or rough) while acting like glue for the pigment. Resins come in all shapes and sizes, typically, urethane acrylic resins are used (like those used in house paints).

I Hope this is helpful.

Sincerely,

Keith Allison ("Dr. Crayola")
Senior Chemist
Binney & Smith, Inc.
[www.madsci.org]

That is crazy weird. I never thought about a resin as a working lube for PLA. I'm using Sharpie brand 'brush' tip markers. All of the colors work the same. If you split the filament into four sides, as little as two sides provide good enough lubrication for it to work.