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kinginnovator

I can extrude PLA but can't extrude ABS at all????

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Trying to extrude virgin ABS for the first time through a .4mm nozel at 260-265C. It is backing up into the bowden tube and running amuck.. I've even tried manually extruding it, but it takes a lot and I mean a lot of force to do so.. What is causng the build up in the Bowden beside's pressure?? Do you have to run the extruder and the machine incredibly slow to extrude ABS? Why can't my UM extrude ABS? Any tips?? PLA no problem obviously but as soon as I switch them out and increase the temp bam, a jam... What steps am I missing??? :ugeek:

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What could I be missing here??? I tried the following:

The PLA and ABS both have the same diameter.

1. Lower temp and higher temp.

2. Slower feed from extruder.

Is there any difference between extruding the two? Any tricks that I'm missing?

The result is the same every time, the plastic is backing up into the bowden tube do to pressure.

Is there a successful setting our there for ABS? (extruder steps in EE, temperature, packing density, etc)????

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Sorry I haven't tried printing it, only extruded it into the air for a little bit to plug up gaps in my nozzle.

Wait what do you mean it's backing up in the bowden tube, is it doing that during a print as a result of retraction? Does it work without retraction? Does it extrude fine into free air? Can you extrude it by hand? What layer height are you trying for? I heard ABS doesn't like to be stretched thin as much as PLA.

Are you using a fan? Try without cooling, maybe that will make the ABS a bit more liquidy. I have heard that other people print ABS without cooling. I have never experienced my "filament backing up into the bowden tube" so I have no idea what that looks like or why it might be caused. Maybe you could take some pictures?

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What could I be missing here??? I tried the following:

The PLA and ABS both have the same diameter.

1. Lower temp and higher temp.

2. Slower feed from extruder.

Is there any difference between extruding the two? Any tricks that I'm missing?

The result is the same every time, the plastic is backing up into the bowden tube do to pressure.

Is there a successful setting our there for ABS? (extruder steps in EE, temperature, packing density, etc)????

a couple of basic questions:

 

  • [*:z8zyb2oh]your filament path is clean&easy? (meaning that there is no bump going from the bowden tube into the brass, when you push the filament through while the printer cold&clean?)

    [*:z8zyb2oh]is your thumb screw for the filament tension set to high/low? (it needs to be "just enough")

    [*:z8zyb2oh]you have measured&set the new E-steps/mm by decoupling the bowden from the cold end, and moving 100mm through? (what value did you get?)

    [*:z8zyb2oh]you have set the packing density in your slicer to 0.85 for ABS (PLA need 1.00)?

    [*:z8zyb2oh]is your thumb screw for the filament tension set to high/low? (it needs to be "just enough")

    [*:z8zyb2oh]ABS prints about 30C warmer than PLA. (at what temp did you successfully print your PLA?)

    [*:z8zyb2oh]when you heat up your UM to 230C, how does it feel when you turn the large extruder wheel by hand? (it should feel springy and difficult after a couple of mm of filament, because the ABS is soft, but not soft enough for printing)

    [*:z8zyb2oh]did you increase the temp by 5C, and repeat the previous step, until you get a constant extrusion that has no more springiness? (you should use that temperature as your initial printing temp)

 

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you have measured&set the new E-steps/mm by decoupling the bowden from the cold end, and moving 100mm through? (what value did you get?)

I recommend doing this hot, while extruding the filament. Just to make sure you are measuring the right thing

hot isn't really necessary as long as you enable "cold extrusion" via the proper g-code, since the bowden is de-coupled, and the filament isn't actually going into the hot end for this test.

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What could I be missing here??? I tried the following:

The PLA and ABS both have the same diameter.

1. Lower temp and higher temp.

2. Slower feed from extruder.

Is there any difference between extruding the two? Any tricks that I'm missing?

The result is the same every time, the plastic is backing up into the bowden tube do to pressure.

Is there a successful setting our there for ABS? (extruder steps in EE, temperature, packing density, etc)????

a couple of basic questions:

 

  • [*:2trfv3tg]your filament path is clean&easy? (meaning that there is no bump going from the bowden tube into the brass, when you push the filament through while the printer cold&clean?) Yes, path is perfect because PLA runs great.

    [*:2trfv3tg]is your thumb screw for the filament tension set to high/low? (it needs to be "just enough")Tried everything, high , low, too high, too low etc. Just even manually letting it sit with no extrusion it starts to kreep up intot the bowden!

    [*:2trfv3tg]you have measured&set the new E-steps/mm by decoupling the bowden from the cold end, and moving 100mm through? (what value did you get?)I will try this out, not sure if it will help at all but at this point I'm just trying to get it to extrude for a good minute while I manually jog it from the mouse clicks. It will start to backup no matter what I'm doing.

    [*:2trfv3tg]you have set the packing density in your slicer to 0.85 for ABS (PLA need 1.00)?Yes

    [*:2trfv3tg]is your thumb screw for the filament tension set to high/low? (it needs to be "just enough")Tried it all.

    [*:2trfv3tg]ABS prints about 30C warmer than PLA. (at what temp did you successfully print your PLA?)230 have tried it at 240,250,260,270,280,285

    [*:2trfv3tg]when you heat up your UM to 230C, how does it feel when you turn the large extruder wheel by hand? (it should feel springy and difficult after a couple of mm of filament, because the ABS is soft, but not soft enough for printing)

    [*:2trfv3tg]did you increase the temp by 5C, and repeat the previous step, until you get a constant extrusion that has no more springiness? (you should use that temperature as your initial printing temp)

 

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Listen let me best explain it this way. I have forgot to even try and print with it because at this point I've tried in manual jog mode to just extrude it consecutively for say 1-2 minutes to see if it can even do that. What I'm doing is pressing the extrude button in PrintRun which pulses the extruder stepper for a brief halh second and then some material comes out, then I repeat the step once that amount that was extruded slows down, it still backs up.

Someone in a scientific way explain to me why I'm able to extrude PLA and not ABS when there are people out there extruding both around the same temp like 240c?? I will even try to do it so slowly by hand and even still it does it. Some comes out the nozel and some goes up and around the incomming filament (sneaks past) and up into the bowden tube... This makes sense because it takes some amount of pressure to push it out the nozel but that pressure is equal everywhere and I know for a fact that the filament diameter is slightly smaller than the hot end hollow brass tube so material sneaks past that small gap too then travels upward and into the larger bowden tube where is solidifies and causes a jam..

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Listen let me best explain it this way. I have forgot to even try and print with it because at this point I've tried in manual jog mode to just extrude it consecutively for say 1-2 minutes to see if it can even do that. What I'm doing is pressing the extrude button in PrintRun which pulses the extruder stepper for a brief halh second and then some material comes out, then I repeat the step once that amount that was extruded slows down, it still backs up.

When I suggested you turn the big extruder wheel by hand, I quite literally mean that you use your hand and turn the wheel, and not press some button in print run. the reason for this is to "feel" the filament going through the nozzle, and getting a feeling for how the extrusion feels when it fails (reasons see below). (And please don't imply that I am not listening to what you are asking...)

 

Someone in a scientific way explain to me why I'm able to extrude PLA and not ABS when there are people out there extruding both around the same temp like 240c?? I will even try to do it so slowly by hand and even still it does it. Some comes out the nozel and some goes up and around the incomming filament (sneaks past) and up into the bowden tube... This makes sense because it takes some amount of pressure to push it out the nozel but that pressure is equal everywhere and I know for a fact that the filament diameter is slightly smaller than the hot end hollow brass tube so material sneaks past that small gap too then travels upward and into the larger bowden tube where is solidifies and causes a jam..

well, if you are extruding PLA and ABS at the same temp, you are over-cooking the PLA (meaning you have a liquid/runny mess), and using a lot of force to squeeze the barely soft ABS through a tiny hole.

that why I was asking you: what is the lowest temp you can extrude and successfully print PLA? if it is 230 for your PLA, and at 225C you can't get PLA through the nozzle at all, that means your TC is about 30C off, since you should be able to extrude PLA at 200C nominally, and print quite well at +10-+15C based on that base temp (temp0). ABS should be extrudable at Temp0 plus 30C, assuming your nozzle and tube are clean from any baked in/cooked up/dried up filament left overs (which is quite likely if you heat up your printer to 270C and more). again, testing the extrudability at a certain temperature requires some "feeling" when you turn the big wooden extruder gear by hand.

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ABS is difficult than PLA for printing because:

ABS is more slippery than PLA, so need more force(more friction) at the hobbed bolt to get the same pressure at the extruder.

ABS is more flexible than PLA, so can deform easily and be smashed than PLA at the hobbed bolt. If the filament is smashed at the hobbed bolt, then it can clog in the PTFE when colling(after some layers).

ABS doesn't have a temperature of transition from solid to liquid like the PLA, is always viscous and gradually become less viscous with high temperature. So it need more pressure to get the same output rate.

If the ABS is printed at low speed and with low extruder diameter(<0.5mm), then it need a little more temperature to stick at the lower printed layers. PLA doesn't have this problem, because PLA need to change from liquid to solid, and this change need a lot cold.

you may need to change some parts of your extruder to be printing with ABS.

See the extruder diameter, if is too small, you may consider feeding with 1.75mm filament(expensive) or change to 0.5mm or get a good hobbed bold(cheaper).

See if your hobbed bold works good, home made hobbed bold have less quality than some available at stores.

See if the ABS gets a lot of pressure and is smashed at the hobbed bolt. if so, it can be clog at the PTFE part.

I don't know what pressure does Erik's Bowden Extruder need to extrude ABS, but i know is less than normal the common version extruder(Wade's Geared Extruder). Erik's Bowden Extruder can work for you.

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