A challenge to all you smart people.

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jeeplvr
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A challenge to all you smart people.

Post by jeeplvr » Thu Dec 19, 2013 9:18 am

If someone will come up with a good idea for a jam proof extruder for the mini I will build it and share the drawings, technology etc.

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wilsonj
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Re: A challenge to all you smart people.

Post by wilsonj » Fri Dec 20, 2013 7:47 am

I'd suggest not printing in the kitchen to start with. :shock:
Regards
Jamie
3DPrinterGear.com.au

roller
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Re: A challenge to all you smart people.

Post by roller » Fri Dec 20, 2013 12:59 pm

Thermally decouple the extruder gear from the stepper motor - not more PLA jams.... and that's it. Oh yeah, and don't buy junk filament. Done, no more jams.

jeeplvr
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Re: A challenge to all you smart people.

Post by jeeplvr » Tue Jan 14, 2014 2:28 am

roller wrote:Thermally decouple the extruder gear from the stepper motor - not more PLA jams.... and that's it. Oh yeah, and don't buy junk filament. Done, no more jams.
Explain the extruder gear mod please. Are you saying the motor heats the gear which melts the ABS?
I bought some Afinia premium filament and I am having much better luck but still getting the occasional jams.

roller
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Re: A challenge to all you smart people.

Post by roller » Wed Jan 15, 2014 3:08 am

That's exactly what I am saying (albeit with terrible grammar - gotta not write replies late at night!).

The problem printing PLA is the is gets soft and deforms at a very low temp. The biggest PLA issue (the primary issue beyond needing temp mods) on the Up is the filament getting jammed for exactly this reason and the heat hitting the filament seems to come primarily through the drive gear. I see this with all repraps that use direct drive as well. On a reprap we dial down the current to the stepper motor to keep it cool. The Up motor gets quite warm - too warm - and I can predict a jam within a few minutes by monitoring extruder motor temp.

The heat is being generated in the stepper motor and conducted through to the stepper gear and straight to the filament. Cooling the stepper motor is an alternative approach OR as we has seen with mods by Drew et al you can focus on cooling the filament gear and filament with injected air. But simply (more simply said than done of course) thermally decoupling the extrusion gear would permanently eliminated the issue.

jeeplvr
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Re: A challenge to all you smart people.

Post by jeeplvr » Wed Jan 15, 2014 3:43 am

roller wrote:That's exactly what I am saying (albeit with terrible grammar - gotta not write replies late at night!).

The problem printing PLA is the is gets soft and deforms at a very low temp. The biggest PLA issue (the primary issue beyond needing temp mods) on the Up is the filament getting jammed for exactly this reason and the heat hitting the filament seems to come primarily through the drive gear. I see this with all repraps that use direct drive as well. On a reprap we dial down the current to the stepper motor to keep it cool. The Up motor gets quite warm - too warm - and I can predict a jam within a few minutes by monitoring extruder motor temp.

The heat is being generated in the stepper motor and conducted through to the stepper gear and straight to the filament. Cooling the stepper motor is an alternative approach OR as we has seen with mods by Drew et al you can focus on cooling the filament gear and filament with injected air. But simply (more simply said than done of course) thermally decoupling the extrusion gear would permanently eliminated the issue.
I see. That might explain the divits in the fillament after a jam. Most times I can simply push the filament a little and the extruder starts extruding again. Rarely do I have to pull the extruder apart and clear a real jam.
So I redesigned the stepper platform and the wind barrier to better cool the stepper motor. So far I have dropped the temperature of the stepper 6 degrees c by just perforating the motor mount.
I wil post some pictures of the new parts and test results as soon as I am through with testing. Basically I perforated the stepper platform to allow better heat convection, especially above the motor. The wind barrier that came with the Mini now directs the hot air away from the cooling fan intake and upward. This should make everything more efficient. I also sealed up the open areas of the wind barrier and removed the silly little wind rudder. I will post the files on Thingiverse tomorrow and post some pictures here as well.

ahntlia
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Re: A challenge to all you smart people.

Post by ahntlia » Fri Feb 07, 2014 4:20 am

Very interested on this, I also have some ocassional jams with ABS and if I can catch her up doing it yes Push a little on the filament will extrude again.
But I will really like to know how to Step-by-step thermally decouple the extrusion gear...

roller
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Re: A challenge to all you smart people.

Post by roller » Sat Feb 08, 2014 2:26 am

So I redesigned the stepper platform and the wind barrier to better cool the stepper motor. So far I have dropped the temperature of the stepper 6 degrees c by just perforating the motor mount.
Unfortunately it's not enough. My stepper motor gets well over 60C ... (some) PLA softens at 40C. 6C isnt enough. If we could just find a long shaft NEMA14 motor to swap in for the stepper then the length of the stainless shaft would be sufficient decoupling to keep the extruder pinion cool enough.

Also, once you get a jam with PLA it will fill up your extruder gear with PLA debris and make future jams/slipping more prevalent. Often after a bad jam I need to clean out the teeth in the gear. If you teeth were a little bigger this wouldnt be such an issue.

brad72
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Re: A challenge to all you smart people.

Post by brad72 » Sat Feb 08, 2014 11:32 pm

You could always mount a "Peltier" cooler to the side of the stepper. Should work pretty well to keep it cool and you could also mount a small heatsink to the hot side of the cooler to improve the efficiency, although not needed.

I don't think that there is much that can be done to the stepper since it is operating continuously so the heat is going to build up.

roller
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Re: A challenge to all you smart people.

Post by roller » Sun Feb 09, 2014 8:02 am

brad72 wrote:You could always mount a "Peltier" cooler to the side of the stepper. Should work pretty well to keep it cool and you could also mount a small heatsink to the hot side of the cooler to improve the efficiency, although not needed.
You mean like I said on the 3 other recent threads on that subject? :)

It works but overall Drew's air injection/pump idea worked just as well, was cheaper, just as reliable and actually less noisy than experiments with using a Peltier. If I were to use a Peltier design again I would actually use it with the air pump to push in chilled air.

brad72
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Re: A challenge to all you smart people.

Post by brad72 » Mon Feb 10, 2014 4:23 am

roller wrote:
brad72 wrote:You could always mount a "Peltier" cooler to the side of the stepper. Should work pretty well to keep it cool and you could also mount a small heatsink to the hot side of the cooler to improve the efficiency, although not needed.
You mean like I said on the 3 other recent threads on that subject? :)
Missed the other threads where you had trailed a peltier but at least I know it is not as successful as I would of thought.

roller
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Re: A challenge to all you smart people.

Post by roller » Wed Feb 12, 2014 6:18 am

It's successful - just inelegant in that it requires more wires, power, some sort of switching to stop it overheating/cooling, another heatsink, generally a cooling fan and then a mount or bracket with good thermal contact for the peltier.

swort
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Re: A challenge to all you smart people.

Post by swort » Wed Mar 19, 2014 4:32 pm

Disclamer:
- I'm not responsible for your actions, all handlings and damages are on your own risk.


Here is what you need:
- Theremal paste (the white stuff for use on computer cpu's)
- A brain, and probably 2 right hands (if your right handed)
- A phillips (+) screw thing
- Some tiny fingers to unplug the power connectors
- A piece of fillament of about 1 meter in length.
- Permanent marker (BLACK)

Here is what i did:
- Unplug the nozzle assembly from the power
- Remove the nozzle assembly from the magnetic holders
(make some pictures on how it is assembled to easy fix it back together for the next steps)
- Unplug and remove the fan
- Unscrew the fan speed printed thing (probably white)
- Unscrew the top fan speed thing holder

Note: for this step it would be easy to make a marking with a permanent marker before you unscrew the nozzle heater.
- Unscrew the nozzle head from the tube (where the fillament comes trough)

Note before this step: make sure you don't use too much it will become hard before you know it.
-Add some theremal paste between the fillament tube and the nozzle heater part (where the 2 meet)
- Clean the filament tube to remove excess thermal paste, that's inside the tube.
-Fix the nozzle head back to the filament tube, remember to align with your line made in a previous step with the permanent marker.
- Fix it all back together according to the images. Remember to plug it all back together as it should have been.

Now make sure the platform is leveled.
And pre-heat the bed before each print (about 15-30 minutes). I recommend to select "pre-heat 1 hour" instead of "pre-heat 15 minutes".
Keep the lid closed.
Now open the FAN thing completely so it blows to the nozzle and not to the heating element.
Use the perfboard, there is no need to clean all holes each time if you print a raft. Just use the flat knife thing you got shipped with your mini to remove
the printed object from your perf board. When you pre-heat your new objects will stick to the old ABS in the perfboard holes and will help avoiding warp.

Have fun printing. This works best for ABS, less warp, less work to remove object, higher print quality, faster prints.

roller
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Location: Brisbane, Australia

Re: A challenge to all you smart people.

Post by roller » Thu Mar 20, 2014 3:49 am

Ah, no I think you are not misinterpreting the issues at play.

You are increasing the conduction of heat up into the body of the extruder by adding thermal paste ... you are going to increase your rate of jams. The issue is to keep heat out of the extruder body and filament feed tube not conduct more up to it. This is why many repraps use high temp plastics in their filament tubes rather than using metal parts. You want the filament as cool as possible until it arrives in the heat chamber. Otherwise, is softens and spreads or bends on itself in the filament tube and jams (assuming it makes it that far).

swort
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Re: A challenge to all you smart people.

Post by swort » Mon Mar 24, 2014 5:48 pm

roller wrote:Ah, no I think you are not misinterpreting the issues at play.

You are increasing the conduction of heat up into the body of the extruder by adding thermal paste ... you are going to increase your rate of jams. The issue is to keep heat out of the extruder body and filament feed tube not conduct more up to it. This is why many repraps use high temp plastics in their filament tubes rather than using metal parts. You want the filament as cool as possible until it arrives in the heat chamber. Otherwise, is softens and spreads or bends on itself in the filament tube and jams (assuming it makes it that far).
you mean DECREASE.
More heat spread over mor surface, with the fan on full open. makes you up! mini JAM-FREE.
As mentioned your not required to do it and it's on your own risk. But it works PERFECTLY for me, so it should work the same for you.
:D

roller
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Re: A challenge to all you smart people.

Post by roller » Wed Mar 26, 2014 6:33 am

No I mean increase because cooling a round shaft with air passing over it is generally less efficient at displacing heat than the rate of conduction. With fins it's possible but just the barrel doesn't work much. You can improve it with a longer stainless barrel as conduction is poor and heat levels fall off more readily.

A heated barrel also presents a longer period you are preheating the filament which will give PLA a greater chance to soften, buckle and jam. My experience comes from 3 years of making hotends, printing with PLA and lots of discussion with the experts of the reprap community over that time.

The purpose of the heater block at the bottom is to provide thermal mass (stored heat) so that when you have a fast continuous feed of filament suck heat out of the chamber there is plenty of stored heat to rush in and keep the chamber up to temp. By allowing more heat to wick away into the barrel and more surface area to chill you are just making your heater module work harder to keep the whole lot up to temp and robbing the thermal battery of some of its heat so you can give it away to the air.

Sometimes the results you observe are not the outcome of the change you intended to make and your mod is actually fighting against the intended design of the hotend to make it's overall characteristics worse. If anything you are just lowering the net temp in the whole hotend which you could have done more successfully with a temp mod.

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