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Prusa i3 clone keeps having jams

Posted by thastealth 
Prusa i3 clone keeps having jams
August 27, 2018 07:25AM
I'm posting this because I don't have any clues how to solve my problem anymore,
The problem which I keep running into is that the hotend keeps on jamming mid print in a lot of prints.
I have found that it hapens everytime when I try to print this: [www.thingiverse.com] so I am using it as a benchmark to test if the printer is functioning.
It occurs sometimes in the 2nd layer, somethings in the 30+th layer, but it never has finished a print.
I'm printing on PLA using a Prusa i3 (self build) clone (AM8). The hotend is a E3D V6 clone and a bowden extruder running Marlin 1.1.8 on a RAMPS 1.4 board. For some reason I have to print at 225 degrees celcius, if I print at <215 it almost immediately clogs
What I already tried:
- Changing the PLA roll (black to red)
- Increased and decreased printing temperature (210-235)
- Replaced the entire hotend/coldend (heater cartridge, thermistor, nozzle, throat, PTFE tube,etc)
- Changed the retraction from 2mm to 6mm (and in between)
- Recalibrated the hotbed distance
- Dailed down maximum speed to 30 mm/s
- Checked extruder wheel (has a little wear, but is not slipping)

When the jam occurs the filament is completely stuck, if I remove the extruder<>coldend PTFE tube I can jank the PLA out, cut the top 3-4 cm from the PLA and reinsert it. then the jam is solved again (for the time being)...
Some strange issues I also noticed (but don't seem to have any impact as far I can tell):
- Temperature of the PLA should be 200 degrees, but if I set mine to that temp it just jams. I have an Anet A8, which prints fine with this PLA at 200 degrees, so I can rule out a problem with the PLA (crap quality or something). I tried various thermistor settings in the FW, but none seems to solve the problem.
- At some moments in the print (corners I guess) the printer slows down a lot, it doesn't do corners smooth, it sortoff starts and stops, it seems like it is having somekind of trouble to do a corner. But the corner seems printed just fine
does anyone have an idea what the problem could be? If additional information is required just let me know....
I use Cura (3.3/3.4 for slicing)

Thanks!
Re: Prusa i3 clone keeps having jams
September 05, 2018 08:26PM
I've been having some similar problems. The immediate suspect is the E3D hotend has a heat break tube with major grooves in it from lousy milling.
They grab onto the filament somehow and cause friction. I was skeptical of this at first, as there are several videos on polishing the inside of the tubes, but its more like "re-milling" as the grooves in my hotend were bad. Like the drill used was completely worn and trashed, but hey, I bought the part.....
So the first thing is to try disassembling the heat break and looking at it with a flash light. Sand any grooves out, and polish per videos out there.
I tried that and it helped some, but have a feeling I need to do a better job. Stainless is hard material so takes some doing.

I use 3mm PLA, and am starting to wonder if that does not work great with the e3d heads. You don't have PTFE all the way down near hot area, just at the top.
The 1.75 mm version has rtoom for PTFE all the way to bottom of cooled area.

So my question is: "is 3mm PLA a bad idea for e3d hotends?" I know there are model numbers and so on, but the principal of less PTFE for 3mm happens on all I believe.
thanks
Re: Prusa i3 clone keeps having jams
September 05, 2018 09:21PM
A genuine e3dv5 3mm has no PTFE. I have a 3mm and a couple of 1.75mm, PLA works fine in them.
Re: Prusa i3 clone keeps having jams
September 06, 2018 07:20PM
Well, that is the question - why do they sometimes not behave?
I got a genuine E3D for my dad and it had issues also. His and my extruder are geared, not direct drive, so have lots of pushing power.
I need to play with things more, but it seems like some people have great luck, and some none.
Its really tricky to know what proper behavior is.

Has anyone measured the force you should need to push 3mm or 1.75 mm PLA through an E3D with .4mm nozzle at whatever temp they like?
I heard you keep raising temp until pushing is not easier, then use that temp.
My experience is its not too hard at first, say for 10 seconds, then the jam happens. I have the fan clipped to the fins and running.

I'm thinking I need to find a source of heatbreaks that are machined decently. That will eliminate that aspect.
I can't buy E3D made hotends, nor should anyone need to as the "clones" are generally made to spec.
This is all open source stuff, so the parts made by the designer are nothing special necessarily.
Obviously E3D cares a billion times more than China about quality, but the bad heatbreak machining should be something we can overcome.
I'm still struggling with it though but have hope.
Re: Prusa i3 clone keeps having jams
September 07, 2018 03:37PM
I agree with the general consensus about E3Dv6 quality (it is spotty). I have had this kind of clogging issue and every time it seems to be something different. I have three genuine E3Dv6 1.75mm hotends and one genuine E3Dv6 3mm. Both have had this issue. There are two things I have done that have corrected this "blockage" problem:
Replace the nozzle. Twice I exchanged the $12 E3D nozzle with a cheap $3 nozzle and problem solved.
Replace the fan. I have had spotty luck with the snap-n E3D 30mm fan. In one case I replaced it with a 40mm fan that was mounted about 10mm away from the heat sink, in another I mounted the 30mm fan that distance away.
I have an E3D Chimera clone that had this problem, I solved it by moving the 30mm fan to one side and mounting a second one on the heat sink.

In short, I think that the problem is a rough and clogging nozzle or heat-creep caused by poor airflow across the heat sink.

I have built several printers, and have seen just about every kind of printer problem imaginable. Here are my solutions, in order of frequency:
Replace nozzle
Change the heat sink cooling
Replace the heat break
Reduce the retract distance

The above list has fixed every hotend problem that I have had. (I won't go into the bed leveling, bed zeroing on asymmetry issues and solutions...)

DLC


Kits: Folgertech Kossel 2020 upgraded E3Dv6, Anet A8 upgraded E3Dv6, Tevo Tarantula enhanced parts and dual-head, TronXY X5SA Pro(E3Dv6).
Scratch: Large bed Cartesian, exchangeable heads, Linear slide Delta, Maker-Beam XL Micro Delta, 220x220CoreXY.
Re: Prusa i3 clone keeps having jams
September 10, 2018 01:19PM
@DLC,
Thanks for the advice. It is good to hear there can be a happy (hot)ending to all this.
Now that would be a good blog title "Happy Hotends"...
This weekend I took apart my three hotends, and compared dimensions to the E3D V6 drawings.
On the main one I have had trouble with, it had several odd things going on.
The heatsink had m7 threads, which is for 1.75 mm filament, but the depth for heatbreak was 18mm.
The E3D drawings call for 15mm on a 1.75mm model. They mixed dimensions on that, as the filament bore is for 3mm.
The heatbreak I have has m7 threaded portion was 15mm, so went in 3mm too far, making the heated end brick too close.
I assume this caused issues with the molten plastic area inside, but I actually thought it would have helped, not hurt.
I had two incrorrectly dimensioned parts. In addition, my heatbreak had a spot for 4.1mm teflon tube to insert.
Its like they mixed a 1.75mm design with 3mm in all the wrong ways.

Having looked at the E3D drawings, it seems the non-E3D manufacturers have gotten "creative".
You can get heatbreaks in m7x6 and M6x6 in many variations.
Some have 4.1mm bore which totally confuses me.
The E3D v6 design for 1.75mm has the teflon bowden tube stopping about 4mm from the top.
The 3 mm heatbreak has no spot for the tube at all.

Why did I end up with a heatbreak with spot at top for 4.1mm teflon tube, but then a 3.2mm bore?
Well, I know how I got it - paid practically nothing and waited 30 days, but....
If I am doing 3mm bowden, my teflon tube is 6mm OD, so cannot slip into the top of the heatbreak.
Am I supposed to have a short piece of 4.1 mm tube in there?
I get that the heatbreak is too small for 6mm tube, but whose idea was it to add in the 4.1mm tubes on hotends for 3mm filament.
I think part of my problem is the friction from the small tube. I think the tube is getting dragged into the hotend a bit, and buckling where it bottoms out.
That would then pinch the filament. The 4.1mm ID should be ok for 3 mm, but after being run through the hobbed gear at extruder, you get a pattern of indentations that have to be the worst for friction.

In the end, I ordered new heatbreaks and heatsinks. I did not order complete hotends as the makers do these funny combinations.
My 3mm heatbreaks will have no 4.1mm teflon in them at all.
I actually don't do 1.75mm filament, so that means all my hotends will be teflon free.

The next thing will be to play with other hotends out there. It seems like the design are stabilizing a bit and I want to try direct drive for my non-bowden extruders.
Fun stuff.

Edited 1 time(s). Last edit at 09/10/2018 01:25PM by jmaeding.
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