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adamp2006

Constant Plugging all of a sudden

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So after getting used to a new supply of PLA and gettting the best out of it i thought all my teething problems were behind me , but it seems not , over the last couple of weeks i've struggled to get a print to finish successfully , it seems that after the first few layers (or sometimes after a 5-8cms which is way more annoying) a plug forms and its print over

I've loosened off the hot end and reseated everything , made sure there is a nice straight / level end to the bowden tube, cleared the print head

i'm at my wits end , was hoping to provide a paying friend with his prototypes for his custom PC tomorrow but it looks like he'll have to wait as i can't leave the print over night with such unreliability

Any suggestions , new things that i've not already tried , permanent solutions ? greatfully received

Running Ulitmaker 1 with V2 hotend

 

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1) Could be dust. Are you in a dusty environment? Some people use some tissue and tape to make a loop around the filament as it is about to feed through the feeder.

2) Are you sure it's a clog? Measure the new PLA with calipers. If it is > 2.99mm then it probably occasionally hits 3.05 or 3.1mm which is enough to get stuck in the bowden tube. You could verify this on the next "clog" by trying to pull the pla out and it should be difficult.

3) Could it be wood splinters from the feeder? Open up the feeder and look in there carefully with a flashlight at the hobbed bolt. Maybe even remove the black delrin clip and slide the big gear out and look at the area carefully.

4) Could it be your filament is tangling? This often causes problems after a while.

5) Could you be printing too slowly? If you are printing .2mm layers I doubt it but if .1mm you should be printing at least 50mm/sec if not 100. And if .05mm layers than at least 100mm/sec. I mean many people can print slower but if you do heat can drift up the hot end. Especially if there is lots of retraction (which slides the heat up due to sliding warmer filament). Then what happens is the filament gets too soft high up in the hot end assembly. Actually this probably isn't the problem as you would have noticed clogs high up (as opposed to at the nozzle).

What do you mean exactly a "plug"? Is it the kind in #5 or is it down in the nozzle?

If #5 then print cooler/faster and with less retraction (4.5mm is plenty).

 

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Ok lets see what i can answer :

Print speed : 149mm/s

Temp 205 :

Filament is free flowing and not tangled (as much as it tries to be lol)

I have noticed alot of heat transfer to the metal plate that the hot end passes through , when i was clearing the head at 250 it was enough to soften the PLA fan shroud

Having just turned the printer on to remove the PLA all i got was puffs of smoke out of the hot end , which is what happened last time (i posted about it and was told it was most likely a plug) , have to push the filament through by hand till i feel it give , and then it flows again , not sure if the nozzle is blocked again and that causing the PLA to back up and plug ?

 

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What layer height are you printing at? 150mm/s is pretty fast, especially at that low of a temperature. The maximum throughput for a standard nozzle is probably a little less than 10mm³/s. So you need to keep (speed x bead width x layer height) < 10. I wrote about this http://www.extrudable.me/2013/04/18/exploring-extrusion-variability-and-limits/.

If you don't, you're going to get grinding of your filament at the extruder motor end, plus very high pressures at the hot end which could cause molten filament to squirt back up into colder parts of the extruder and solidify.

So I'd be inclined to start by raising your temperature to more like 220 or 230º, and slow down and/or thin your layers if needed to keep your extrusion rate in more of a 5-8mm³/s range.

 

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Next time you take the hot end apart, take a close look at the V2 Teflon tube (between the Bowden tube and the brass tube). My Teflon tube developed a small chip right next to the brass tube on the inside wall. This was causing jams. I removed the Teflon tube entirely.

Also, the Teflon tube ID is supposed to be slightly smaller than the ID of the brass tube, so any melted or soft plastic that re-hardens in the Teflon tube is more likely to be able to pass into the brass tube. With my V2 brass tube and Teflon tube, this is not the case! The Teflon tube ID is larger than the brass tube. In fact, my Bowden tube ID is smaller than the Teflon tube ID and my hotend is running fine without the Teflon tube, but then again, the V1 never had a Teflon tube either. I also mostly print ABS and nylon (618 and 3ntr PA-6) and haven't run much PLA since removing the Teflon tube.

 

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So I'm confused. You clearly describe underextrusion but what made you think it was a plug? Can you explain this better?

Are the models with issues - do they have much more retraction than the earlier models that printed fine?

150mm/sec should be fine at .04 layer height. This is only 2.4 mm^3 per second. This is equivalent flow of 30mm/sec travel at .2 layer height which is definitely not pushing the limits.

 

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So when a print fails if i stop it and unhook the part of the extruder that puts pressure on and push the filament up it feels like something is stopping it , and if a apply more pressure it will push through the blockage and flow again , thats what leads me to think its a plug

Its all types of prints, it pretty much prints the first few layers (very well with no problems) nice and smoothly as i have the first and last layer thickness high to get a good smooth outside to my finished prints

If it is indeed underextrusion and not plugging what are my options ?

 

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Plugging causes underextrusion. So it can be both of course.

This description is strange. The feeder should be able to push/pull 22 pounds of force. That's harder than I can actually push on the filament. So either you are using pliers or you are much stronger than I am or something doesn't make sense.

Could you test your feeder? Make sure it can pull at least 10 pounds of force? Put the filament only a few inches into the bowden tube so there is no forces required to get it into the print head (bowden should be mostly empty). Have 2 one gallons jugs of water (or milk) nearby. They weigh 8.3 pounds each. Feel the force it takes to lift one. Now try to fight the filament and have it feed filament. For example you can just turn the feeder gear with your left hand while gripping two water jugs to the filament with the right hand in such a way that you are neither lifting nor pushing down with the right hand - just gripping the filament locked to the 2 gallons of water. Can you lift this by turning the big feeder gear? If not something is wrong with your feeder and we can talk about that (start with photos of it open and closed).

If this test passes then something must be hapening at the print head. Maybe a "soft" clog. Maybe something else. The next time it clogs you could just pull the bowden tube out. While the print head is still hot, remove the blue clip that holds the ring up. Then with one hand push down on the ring and with the other hand pull out the bowden tube firmly. Look inside the tube and use a flashlight to look down into the print head. Is there a clog?

These clogs in the upper part of the print head are usually caused by lots of retraction. Retraction pulls the hot filament up which touches the sides which heats the upper part of the print head chamber. Then the next retraction moves the heat further and further up until it gets hot enough to soften the PLA and cause a jam.

Or maybe there is a clog in the nozzle itself and you are just amazingly strong (compared to me).

I feel like we still haven't ruled out 3 completely different possibilities and you need to start eliminating them to narrow it down to the actual problem. And there are more than just these 3.

 

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The most force you can apply to the filament is by combining the force of the feeder with manual assist (using pliers, if desired, but I usually just wear a nitrile glove to increase my grip on the filament). You can use the feeder motor to push the filament, but I just use one hand to turn the big gear while pushing down with my wrist on the UM chassis, and my other hand to push upward on the filament--always gripping the filament very close to the entrance to the feeder while keeping the filament direction square to the feeder. I installed one of these add-ons to keep the feeder in place:

http://www.thingiverse.com/thing:25436

I have often cleared partial and complete jams this way but, more importantly, I "prime" the hot end fully using this technique before every print to make sure the hot end is free-flowing plastic through the nozzle. I've found that partial jams are common when starting a new print (perhaps due to the state of the once molten and partially molten plastic inside the head) and this precaution will nearly always get the print off to a good start much better than any "priming" performed in the gcode.

 

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Also, if you're suddenly getting problems where you didn't before, check your fan. It may have shifted, and now be blowing on the nozzle tip, reducing the temperature sufficiently that it can't extrude properly. With this, prints normally start of, because the fan is off, and then after a few layers, the fan comes on, and the temperature of the nozzle tip gradually drops until you get past a tipping point at which extrusion fails.

 

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Ok did a force test , didn't have any gallon water jugs around so used plastic dumbbells pulls easily with a single 5kgs (11lb) weight and also with 2 so almost 22lbs , i'm setting up to run the last print it failed on and see if it happens again , if it does then i will examine the print head for clogs , am also checking the position of the fan as suggested by illuminarti

EDIT :

 

I think illuminarti may be on to something , preheated as usual , and measured the temp with my thermocouple probe , nozzle read about 203 ish , measured on the far side of the nozzle furthest from the fan , switched fan speed to 100 and the temp droppped to 160 -180 range , so seems the PLA fan shroud could well have warped and moved after several months of use and now be cooling the nozzle and not the print, going to switch back to the origarmi version from the kit (hope i still have it) and retry the test see if it eliminates the head cooling , if it does i will do a test print

 

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It seems that although the nozzle was being cooled by the other fan that was not the only issue, it still seems to block up , took the bowden off when i notice it wasn't extruding and it seems to be something down in the nozzle, once its cooled i'll take it apart and have a look

 

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If you disassemble while it is below 180C you may break it. Especially the brass nozzle - do not attempt to unscrew it without it being at least at 180C. It is very delicate. Well -- delicate if you are using a wrench. Very strong if using your fingers.

 

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looks like theres a blockage where the brass tube meets the nozzle,

 

That's just filament from the most recent print don't you think? Or is the blockage a different material/color? Are you sure there is no blockage higher up in the cooler parts of the hot end? Like in the part made out of PEEK? Or maybe down in the tip of the nozzle.

 

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The blockage was a different colour , more of a gray and i'm using clear / natural pla currently

Swapped everything back to the original parts that came with the kit , so fan shroud and extruder (as i was using a Berthos version) i managed to get one ok print (all be it with lots of stringing and now got my leak back in the print head (sortable though i'm just always weary of snapping the brass tube) yeat today we are back to a couple layers and then no filament being extruded , slightly fed up now .

 

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Ahhh! sucks! :???:

Are you sure it isn't dust on the filament? Or wood chip dust coming from the extruder? How many mm of filament do you think you used before it stopped working?

 

blockage was a different colour , more of a gray

 

What the hell? Were you using gray in the past? Does the clear PLA turn gray if you overheat it?

 

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Yeah--I always prefer to risk finger burns than risk my hotend brass parts and it comes apart so easily when it's hot! :)

 

If you disassemble while it is below 180C you may break it. Especially the brass nozzle - do not attempt to unscrew it without it being at least at 180C. It is very delicate. Well -- delicate if you are using a wrench. Very strong if using your fingers.

 

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