Please Help me diagnose my Filament jamming issues

I've attached an image of the filament after the jam. Im using a cheap Chinese e3d knock off with a mk8 drive gear. Ive tried a range of temperatures from 185 to 210 still the same jam. Ive reduced the filament retraction to 0.5. When the printer isn't jamming i can hold the filament and it pulls through with good force. Ive measured and calibrated the feed rate. The body of the heatsink is cool to the touch. Ive used option 11 in the marlin software for the thermistor settings. It controls fine but can take time to settle. Ive also used the thermistor table shown below. I have no way of checking the real temperature of the the hot end. From the picture i can see a bulb at the end of the filament and im thinking this is what is jamming. The bulb isnt big and should be small enough to be in the hotend. Im running out of ideas. Any other things you can think of would be appreciated.





E3D Knock off
[www.ebay.co.uk]

Mk8 Drive Gear
[www.ebay.co.uk]

Extruder
[www.thingiverse.com]

Thermistor table
[nutz95.wordpress.com]

Edited 1 time(s). Last edit at 11/02/2015 04:15PM by i3ond.

I have read that the PTFE tubing in some knock-offs can be the wrong size making for a tight fit. Someone else posted in another thread that the clones don't use the same finishing process on the internal borings and you should use some sand paper on piano wire (?) to smooth the barrel.

In the short term, you might try oiling the filament before inserting it into the hotend. I have an official E3Dv6 which benefits from that. Might also bump up your PLA temp to 220ish.

Im using it direct drive so the ptfe tubing has been removed aswell at the fitting. I dont see any signs of kinking in the filament caused by the void where the push fitting has been removed. If its PTFE lining your on about the hotend and heatsink are not lined. I think i may try bumping the temperature up more. Ty

Another thing is when the jam happens I remove my drive gear and try to push the filament manually. Its really stiff and doesn't move at all. As soon at I remove the filament and cut the bulged end if it feed fine.

Pretty sure you still need the PTFE inside the extruder, the cool area where the fins are. It stops at the stainless steel heat break. Not an expert at this though, definitely could be wrong.

Do you have the hotend fan on all the time, blowing air over the fins?
+ do you have a "space" between the heatblock and the fins?

To me it seems the filament has melted to high.

Edited 1 time(s). Last edit at 11/02/2015 05:09PM by Koenig.

I dont think its melting on the heatsink. Fans on all the time and i can touch the heatsink its no where near even warm. Theres a stem separating the cooling block from the hotend.

The nozzle I.D. is larger than the connector tube I.D. is this correct. Im starting to think when print goes to retract the bulb is stopping it and then the drive gear is tearing into the filament and when it extrudes afterwards it can get the grip due to the tear. Has anyone came across this before is that possible.

Might be a stupid question but why a PTFE tube in a full metal hotend?
I only use teflon in the top part of the hotend - from inside a bowden connector to the actual hole in the hotend, but not all the way down.
E3D clones can be bad and I wrote a few things on how to fix them, you might want to check for this.

Most clones use the teflon as the hotend is universal.
So 3mm will go in without teflon, 1.75mm get's the tube stuffed in.
Sadly some chinese sellers use very thin walled tube that on top of that is also quite tight.
The tube that came with my hotend had 4mm outer diameter and 3mm inner diameter, leaving no room at all for filament damage caused by the extuder or expanded filament during retractions.
Due to being too fragile those tubes also love to shrink in diameter at the hot end from the constant pushing.

FWIW, when I switched from an all-metal hotend to a PTFE-lined one, I suddenly began printing again. The PTFE in mine goes down inside the heat break.

It's important to tighten the heat break against the nozzle inside the heater block, and to do that while everything is *hot*. Search here for my posts to find the correct procedure.

Google for "PID tuning" to improve temperature control.

fyi, Id recommend actually testing the tempatures you expect with a meter...


they could have told you the wrong thermistor, for instance...


I found my readings were off by 30c

Well i was able to get hold of a k type TC for my meter and have a look at the temperatures. Reading from where the thermistor is located im getting a 10c drop which i thought wasnt to bad considering i was printing pla up to 210 so real term 200 but then i decided to measure at the actual nozzle yea. Im getting a 40c drop there. Ive ramped up the temperature to 225 and im gonna test it. Hopefully this will do the job. Looks like ill be making a custom lookup table.

I'd like to repeat what others have said. I was also using a clone E3d and had converted it to be "all metal" by switching out the ptfe lined heat break. I had a great deal of trouble printing (PLA). It would jam every time despite my trying quite a few different cooling options and the heat sink always felt very cool. In the end, I put the ptfe lined heat break back in and it has worked perfectly since. Many people have had trouble printing with PLA in an all metal hot end. The heat traveling up the heat break is enough to melt the PLA filament in the heat break.

Edited to add: I went through the same process with my thermistor tables. I thought for certain that was the issue. Made no difference but I did learn quite a bit about that side of the process. I actually think that raising the temperature will likely just make things worse as heat will travel further up the heat break. I can guarantee that your current temperatures are more than sufficient to melt the PLA well enough that the clog is not happening in the heater block.

Edited 1 time(s). Last edit at 11/03/2015 08:57PM by MichaelBrock.

The heat break didn't come lined I'd have to bore it out to add one.

Don't get me wrong, but the whole purpose of an "All metal" hotened is that there is no telflon in the hot parts.
The only teflon in mine was to bridge the top part of the cold end as it was designed for bowden but I use a direct system.
And that bit of teflon is now gone in favour for a custon PEEK adapter.
Before I add a telfon liner I would simply polish the metal...

Quote
Downunder35m
Before I add a telfon liner I would simply polish the metal...

This could actually worsen the problems all metal hotends have with PLA. For anything else it should help.

As for the purpose of all metal hotends. Apart from PC, which is seldomely used by anone, i have yet to see a reason why all metal would be preferable.
If you install a usefull cooling solution a hotend with PTFE can achieve 260°C or similar. People usually overestimate how hot the upper part of the hot part of the hotend becomes.
Teflons melting point is above 300°C and as long as there is no strong mechanical force acting on it during print there is no reason why it shouldn't work for even more than 260°C.
I think the bad press teflon got is mostly due to the very first few hotends where teflon was used for structural components. It will fail in those situatiuons because it becomes soft at rather low temperatures.
With my Merlin hotend i print at 255°C regularily.

---

[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Well, all I can say is that I tried both, the all metal ones with teflon liner and those without.
Only if the liner has walls of more than 1.5mm they survive, otherwise they are a consumable.
I print PLA, ABS, Nylon and rarely PC with my hotend and there is no jamming (unless for the usual causes like contamination or not enough cleaning when coming from a high temp plastic) and no other problems.
But might be a quality thing too as I use 15$ E3D knock offs from china....
And you might check the properties of teflon as it is useless above 260° Celsius and I doubt get special PTFE tubes
Melting might be happing at much higher temps but the material softens and that is what causes the problems together with retractions.

If you need a teflon liner for your all metal hotend that it either has cooling problems or is of really shitty quality.

I've been fighting with PLA in my week-old Prusa i3, and was having similar problems where it would print for awhile but then jam. I couldn't print more than a dozen layers or so before the problem would come in. Looking far and wide, the solution I found (that seems to be working for the last three prints, knock on wood) was to put Canola oil on the filament before putting it through into the extruder. Clean out the hotend as good you can, do a cool pull if possible, then rub the canola oil over a 6-12 inches of the filament. I've been doing this type of "hot end seasoning" for another 6" or so before every new print, and it's now able to complete prints without jamming.

I saw it recommended specifically to use canola oil, not vegetable or olive oil, as canola oil has a higher smoke temperature and won't burn at the temps of PLA extrusion.

I hope it helps! Good luck!

Edited 1 time(s). Last edit at 11/07/2015 03:18PM by ellie_l.