Tag Archives: nozzle

Adventures with PLA temperatures

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Kinda rhymes, no?

Given Rick Pollack’s PLA printing success and temperatures at barrel entry rather than nozzle, I should probably start delineating between temperatures at the barrel and nozzle.  If barrel entry temperature is truly a critical factor, then he’s totally right about how going by nozzle temperature is like driving a bus with just the rear view mirrors.

However, this gives me pause.  Everything I’ve read about ABS suggests it may be best to melt it right at the nozzle as quickly as possible.  I’ve found that ABS cools very rapidly too.  PLA on the other hand takes a while to cool (but, then again, I was running my extruder too hot) – with the parts being quite flexible for some time after printing.  If barrel entry temperature is that important, then it seems that PLA must need a longer time to melt.  If this is the case, should the nichrome be wrapped higher on the barrel?  If so, then Rick’s heater cores (which already seem very convenient) are downright brilliant – since you can probably easily adjust where the heat is being applied.

From Nophead’s comment I gather that I was, indeed, running my extruder too hot.  I found that at my ABS temperatures (220+) made the PLA just drip right out of the heater – and once that had basically stop it would then intermittently release little amber droplets of plastic.  I must have been really cooking it.

With the limited printing I managed with PLA I found that it printed well with my non-temperature ABS Skeinforge settings.  So, before I go back to PLA I think I’ll finish tuning my ‘bot using Nick Ames’ Skeinforge tutorial.

How are you printing with PLA?

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I’d like to print in PLA, I really would.  No warping?  No rafts?  Smells like syrup?  Makes kittens and rainbows?  Sign me up!

Rick from MakerGear has the following suggestions for printing in PLA:

  • Have a 150-160 C degree temperature for the entry of the barrel
  • He notes that the nozzle temperature is roughly 190 C degrees
  • However, later he suggests printing at 220-235 was possible
  • He suggests not to worry overmuch about PLA in the threads – its just one of those things

Nick McCoy offered several pieces of wisdom:

  • He found that 10W-30 oil added lightly to the PLA as it entered the extruder, by adding oil to a piece of cotton wrapped around the filament, helped it print without jamming
  • He noticed that pausing the extruder for more than a few seconds would jam the barrel
  • He found he could print at 180-210 degrees (I assume he’s measuring the nozzle temperature as you would with an ABS setup)

Nick’s results suggesting a nozzle temperature of 180-210 seem to match up with Rick’s findings of 190 or so.  I think I’ll give Polly another shot and see if I can extrude at those temperatures.

How to unclog your extruder barrel and nozzle

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Nozzle and barrel apart

Nozzle and barrel apart

Here’s the process I used to unclog my extruder barrel and nozzle without a lot of extra equipment.  Obviously you should take all reasonable safety precautions with goggles, gloves, tongs, with a fire extinguisher, etc.  Plan ahead and be safe.

1. Materials:

  • Clogged extruder
  • Yarn
  • Q-tips
  • Heavy iron hook
  • Wrench
  • A big rock
  • Ethernet cable
  • Wire strippers
  • Blow torch
  • Safety equipment
  • Drill bits
  • Thick rubber band
Cleaning the inside of the nozzle - kinda gross

Cleaning the inside of the nozzle - kinda gross

2. Process:

  1. Disassemble the extruder
    1. Since PLA had gotten into the threads I had to leave the extruder warm as I unscrewed the PTFE insulating barrier.
    2. Unwrap the heater – taking off the ceramic tape, thermistor, nichrome, and Kapton tape.
  2. Remove plastic from the extruder
    1. I wrapped the unsharp end of my smallest drill bit in a thick rubber band to give it a grip.
    2. I then rotated the drill bit into the barrel by hand.
      3. Extruder barrel and thick yarn

      Extruder barrel and thick yarn

    3. When I had gotten as much out as I could, I switched to a slightly larger drill bit (again wrapped in a rubber band for grip) and drilled out as much as I could.  I repeated this until I had gotten to my largest drill bit that would fit in the barrel.
    4. I used a precision flathead screwdriver to follow along the threads of the extruder barrel and chip out plastic.
    5. I used the same precision flathead screwdriver to follow the threads inside the PTFE and chip out plastic.
  3. Heat the barrel
    1. This prior post has pictures for the entire setup.
    2. I was unable to remove the nozzle from the barrel.  Don’t worry if you can’t either.
    3. Put the extruder nozzle and barrel inside the large washer so the barrel is hanging down through the washer with the nozzle keeping it in place.
    4. Place the washer on a big iron hook or some similar piece of large thick heavy metal.
    5. Weigh down one end of the hook with the rock.
    6. With all reasonable proper safety measures in place and with adult supervision, heat the barrel and nozzle with the blow torch until it emits black smoke (which you should NOT breathe) and then keep it hot until it stops emitting smoke.
      7. Flossing the nozzle with copper wire

      Flossing the nozzle with copper wire

    7. Use the wrench to pick up the assembly and check if you can see through the nozzle.
    8. If you can’t see through the nozzle, keep heating it.
    9. Once you can see through the nozzle, it’s time to clean the extruder again
  4. Clean the extruder
    1. Once the barrel and nozzle had been heated, I found the nozzle came off very easily.
    2. Clean out the large cavity of the nozzle with the Q tip.
    3. Clean out the barrel with the yarn by inserting the yarn and “flossing” it.
    4. I happened to have pieces of an ethernet cable lying around.  I cut open one of the wires inside and pulled out the thin copper strands.  I took two of them and fed them through the 0.5mm nozzle.  I “flossed” the nozzle until it felt reasonably clean.
  5. Reassemble!

Cracking a tough nut

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Dave M. posted his process for removing a threaded barrel from his PTFE insulator, and it’s brilliant.  I was wondering how to do this since I may want to get my heater barrel out of the nozzle.  But, how to do it without having to some plyers, vice, or some other crushing instrument on the threads?!

  • Screw on one nut, a washer, and another nut.
  • Put the PTFE in a vice
  • Put a wrench on the nut below the washer
  • Muscles!

An idea for checking the temperature of an extruder at the barrel entry

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Several people have suggested that the temperature at the entry of the barrel is very important to printing with PLA.  This makes sense.  If the temperature at the barrel entry is above the melting point for PLA, it can melt right there and ooze down around the threads.

Maybe I should assembly my extruder with just the thermistor on the barrel entry, and heat it until it is just below the melting point of PLA – then check the temperature at the nozzle.

Or, I could get a second thermistor and use it at the top of the barrel while keeping the original thermistor at the nozzle.  I could only use one set at a time (since I don’t know how to hack the electronics/extruder board), but that shouldn’t be an issue.

MakerBot extruder clog experiment

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DO NOT USE THIS extruder unclogger setup

DO NOT USE THIS extruder unclogger setup

UPDATE: DO NOT USE TILES!!!  THEY WILL SHATTER!  READ LATEST POST!

The bad news is this is my first clogged extruder.  The good news is I have all the spare parts to whip up a new extruder, no problem.  That means I can experiment with wild abandon!  My backup plan is to slice and dice the PTFE insulator into washers.

Having drilled out most of the plastic clog from the barrel, it’s mostly empty.  The PTFE is in pretty good shape with the threads intact, if a little worse for wear.  My plan to get the remaining plastic out of the nozzle is to put the nozzle/barrel assembly into the large washer upside down and prop it up on some ceramic tiles.

My hope is that by applying a heat source to the nozzle the plastic will just drip/fall out.  The suggestion for using a blow torch to clear out the barrel and nozzle comes from Rick Pollack / MakerGear.  Thanks again Rick!

By the way, wicked Google Sketchup skillz, no?

New print: MakerBot Insulator Retainer Ring

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Insulator Retainer Ring

Insulator Retainer Ring

Lots of non-robot stuff keeping me busy…  but not too busy to print a replacement insulator retainer ring!  I should really start a list of the first things you should print once you get a MakerBot.  This should be way at the top, even above the Z-axis crank.

From what I gather from the MakerBot operators group, the 5mm acrylic insulator retainer ring that comes with the MakerBot kit will eventually fail.  If this happens, the heater will basically pop off and melt into whatever you were building at the time.

Really, it’s all about choices, right? The extruder motor is super slow but super strong.  Chances are it will eventually deform some part of your assembly.  With this in mind, you can build your heater assembly with and without the nut.  Depending upon which you do, different parts will be bearing the brunt of the force exerted by the extruder motor.

If you assemble the heater without the nut below the washer, the majority of the force will be applied by the motor to the filament and into the barrel and nozzle, eventually forcing the nozzle downwards, ruining the PTFE insulator barrier, stripping the PTFE barrier threads, pushing out the nozzle, and making a molten oozing mess of everything.

If instead you assemble the heater with the nut below the washer, the nut will hold the washer in place and the majority of the downwards force applied by the extruder motor will be placed on the insulator retainer ring.  If the insulator barrier ring fails, it will crack or shatter dropping the heater into whatever you were building.

The good news about the second method is that its pretty easy to print up a replacement insulator retainer ring to keep handy!