EZstruder snapping filament halfway through long prints

[shentheory]

So this post may be a little premature, as I didn't get a chance to really diagnose the issue before i had to leave for work this morning or look at any settings, but I'd just like to get some tips on what I should look into specifically when I get home.


I walked in this morning to a 6 hour print I had left over night, only to see it was about 30% complete. I take a look up at the extruder and see this:

[img]http://i.imgur.com/GHapp8N.jpg[/img]

This is the second time this happened in the past few days. I'm printing ABS 1.75 from Microcenter. I inspected the filiment and didnt see any existing cuts or deformation. There was no pulling or twisting in the spool, it feeds down to the extruder pretty well. And again, this seems to only happen with longer prints. Anything under 4 hours typically comes out great. What could be causing this??

I will update with my current Slic3r settings when I get home, im just anxious here at work

Much appreciated!!

[Nylocke]

Filament grinding comes from excessive back pressure from the hot end, generally from too low of extrusion temps, or in some cases problems with something blocking the nozzle. I don't think you're having the later, so what temps are you printing at? I say 230 is bare minimum for ABS, 235-240 offers much better layer bonding.

[shentheory]

Filament grinding comes from excessive back pressure from the hot end, generally from too low of extrusion temps, or in some cases problems with something blocking the nozzle. I don't think you're having the later, so what temps are you printing at? I say 230 is bare minimum for ABS, 235-240 offers much better layer bonding.

Thanks! Could you explain why that is a little more? I'm printing at 230 and the bed is 100. I'll try around 240. Would retraction possibly be a factor? I'm completely new to 3d printing, but it seems like when the extruder retracts, it's so much faster that it could possibly grind the filament.

[Nylocke]

It can possibly, but that generally only happens when the spring is over tense. I run 4mm retraction at the least at 60mm/sec and it works fine without much grinding. Maybe if there are a ton of small features spaced far apart so the same 4mm of plastic is retraced over repeatedly you might have some problems, but retracting once shouldnt be a problem.

The issue is if you try to extrude faster than your temp will allow it will resist, since you can't force a solid object (or super vicious thermoplastic) through a hole .5mm when it starts out as 1.75mm. The filament will try to buckle in the teflon tube, which it can't actually do since the ID is 2mm. After it buckles as much as it can it will start to stop moving, or move less, through the extruder, but the extruder is still going at the same speed. Because of friction between the filament and the hobbed gear on the motor shaft (increase by the teeth) it starts to wear on the softest material, AKA the filament, and so it starts to eat away at the diameter of the filament, eventually getting to the point where its cut all the way through it, like you have experienced.

Another factor that doesn't help is that the steppers get a little warm during operation, which brings the filament a smidgen closer to its glass phase. ABS thats probably not too much of an issue, but with PLA people have reported the filament being flattened because of the stepper heat. This isn't that common of a problem though, I don't suffer from it, and I don't know of many others who do on a regular basis.

[shentheory]

It can possibly, but that generally only happens when the spring is over tense. I run 4mm retraction at the least at 60mm/sec and it works fine without much grinding. Maybe if there are a ton of small features spaced far apart so the same 4mm of plastic is retraced over repeatedly you might have some problems, but retracting once shouldnt be a problem.

The issue is if you try to extrude faster than your temp will allow it will resist, since you can't force a solid object (or super vicious thermoplastic) through a hole .5mm when it starts out as 1.75mm. The filament will try to buckle in the teflon tube, which it can't actually do since the ID is 2mm. After it buckles as much as it can it will start to stop moving, or move less, through the extruder, but the extruder is still going at the same speed. Because of friction between the filament and the hobbed gear on the motor shaft (increase by the teeth) it starts to wear on the softest material, AKA the filament, and so it starts to eat away at the diameter of the filament, eventually getting to the point where its cut all the way through it, like you have experienced.

Another factor that doesn't help is that the steppers get a little warm during operation, which brings the filament a smidgen closer to its glass phase. ABS thats probably not too much of an issue, but with PLA people have reported the filament being flattened because of the stepper heat. This isn't that common of a problem though, I don't suffer from it, and I don't know of many others who do on a regular basis.

This. I didnt take a picture of the remaining filament that I pulled out the hotend, but the end of it was like a fat mold of the inside tip of the hot end. So i will definitely try upping the temperature. Hopefully I can stick around this weekend so I can monitor a long print. This is where octoprint would come in handy!!

[jdurand]

I hadn't thought about the heat up at the gear. My old Afinia printer jams with normal PLA but works fine with their high-temp stuff. Hmmm, wonder if that's the problem.

Also had a problem with t-glase but that might be too viscus for the 0.4mm nozzle on the Afinia. Sure didn't print pretty.

[Nylocke]

Yeah, PET is sorta hard to print, even if its T-glase, which I believe Taulman formulated to be easier to print. Unfortunately I don't have any real solutions to printing T-glase other than trying a larger nozzle, large layer heights (.3-.4 or so until you got it down) and maybe slow speeds. Someone was recommending 20mm/sec or slower. I don't know the reliability on that info though.

[BenTheRighteous]

I'm not sure the extruder gear could possibly get that hot.

I don't have any evidence other than my own anecdote, but the other day I was trying to melt some loctite out from between a shaft and a pulley. I had a windproof lighter (a mini butane torch) focused on the thing for a good 20 - 30 seconds, and all it accomplished was making hot for a few seconds. After just a moment, it was practically cool to the touch again. (Needless to say my efforts were fruitless.)

I would imagine that regular duty is a lot less extreme and those things apparently shed heat like crazy. I personally have 0 concern that my extruder gear would be hot enough to impact the filament even the slightest.

[Nylocke]

I did say its normally negligible, but it can happen, depending on stepper loads and the current you're putting through it.

[nitewatchman]

I didnt take a picture of the remaining filament that I pulled out the hotend, but the end of it was like a fat mold of the inside tip of the hot end.

The end of the filament will usually always have the bulb or knot on the end to some extent. This is normal no matter how hot you run the filament. It is caused by pulling the hot blob of material back through the tube.

When the material is hot in the tip, there is a nugget or reservoir of material after the end of the PETN Tube in the heat break and the reduced part of the nozzle (.5mm tip). It is can be relatively big. When you pull the hot plastic back the knot is drawn through the PETN Tube and takes the exact size of the ID of the tube and elongates. If you look closely there will be a small reduced area between the knot and the filament that was stretched during the drawing out operation. This to me is very normal and unavoidable.

[Nylocke]

PETN is a high explosive, I think you mean PTFE?

[nitewatchman]

Slip of the fingers, in my day job I deal with large quantities of PETN and RDX. When I reread the post it looked normal to me.

Use PETN coated tubes also.

[bot]

I want a PETN coated tube in my filament path, riiiight up to the melt zone.

[nitewatchman]

Careful what you wish for!

The material is a little odd in that respect. The sheet scrap is routinely burned. You treat it like cardboard and burn it in a barrel. The material we use has a velocity of about 29,500 ft/sec and it takes a significant shock to go high order. At the melt zone it would either melt and run out or burn. The sheet is produced by extruding through a nozzle that forms a 3-1/8" cylinder with a specific wall thickness, the tube is then split and rolled into a 10" wide sheet.

[shentheory]

It can possibly, but that generally only happens when the spring is over tense. I run 4mm retraction at the least at 60mm/sec and it works fine without much grinding. Maybe if there are a ton of small features spaced far apart so the same 4mm of plastic is retraced over repeatedly you might have some problems, but retracting once shouldnt be a problem.

The issue is if you try to extrude faster than your temp will allow it will resist, since you can't force a solid object (or super vicious thermoplastic) through a hole .5mm when it starts out as 1.75mm. The filament will try to buckle in the teflon tube, which it can't actually do since the ID is 2mm. After it buckles as much as it can it will start to stop moving, or move less, through the extruder, but the extruder is still going at the same speed. Because of friction between the filament and the hobbed gear on the motor shaft (increase by the teeth) it starts to wear on the softest material, AKA the filament, and so it starts to eat away at the diameter of the filament, eventually getting to the point where its cut all the way through it, like you have experienced.

Another factor that doesn't help is that the steppers get a little warm during operation, which brings the filament a smidgen closer to its glass phase. ABS thats probably not too much of an issue, but with PLA people have reported the filament being flattened because of the stepper heat. This isn't that common of a problem though, I don't suffer from it, and I don't know of many others who do on a regular basis.

I wanted to give you an update, It worked!! thanks so much. I had my hotend temp at 235, I bumped it to 245, and I bumped the heated bed from 100 to 110. It went through a 10 hour print last night with out a hitch and the print looks perfect!! It's weird that the manual says to go to 225 for ABS!!! It's possible too that since it's winter the colder room temperture required you go a little higher than normal. Anyways thanks again! I'm back to printing like a champ!!!

[Mac The Knife]

ABS from different manufacturers will have different characteristics. Different colors from the same manufacturers may need minor tweaking.

[Nylocke]

General rule of thumb is the darker the coloring the higher temperature you'll have to use. Of course YMMV, you should tune it to get the best results. Clear versions of filaments generally need lower temps (Eg, Opaque PLA normally goes around 200-210 while clear stuff goes 190-200, or sometimes in the 180 range). Use whatever works.

245 is getting up to critical temp for the PEEK, be careful that you don't go any higher than that, unless of course you're running an all metal setup. Make sure your fan is always on and running properly, and that your thermistor is secure.

[shentheory]

General rule of thumb is the darker the coloring the higher temperature you'll have to use. Of course YMMV, you should tune it to get the best results. Clear versions of filaments generally need lower temps (Eg, Opaque PLA normally goes around 200-210 while clear stuff goes 190-200, or sometimes in the 180 range). Use whatever works.

245 is getting up to critical temp for the PEEK, be careful that you don't go any higher than that, unless of course you're running an all metal setup. Make sure your fan is always on and running properly, and that your thermistor is secure.

Thanks! yes I'm running an e3d V6 all metal hotend.