HI guys, im having terrible extrusion problems with a j-head.

HI guys, im having terrible extrusion problems with a j-head. I had a few (and managed to burn the peek barrel) and i always had the same problem, sooner or later the extruder got blocked and stopped working. The only solution whas to disassemble, do a deep clean and assemble again.

j-heads are great, i know, but im failing to use it. Any hint on what i might be doing wrong?

Im printing ABS, tried from 215 to 240, got always the same results.

Sounds like your printing too hot! You say you’ve tried 215-240, what is the minimum temp you can push the filament through by hand (lot of force)? Temps may not be accurate so you have to just gauge what the filament softens at.

Is this a legitimate J-head, or a chinese knock-off?

Legitimate. Simon, will try that again. Im using a marlin table 5 thermistor now.

Filament quality can have a huge effect. Where did you get the filament ?

tried with http://czechreprap.eu/ and national (argentinean) filament. With an Arcol hotend i dont have this kind of issues.

Dude. If the Arcol works, ebay your jhead and buy another Arcol. Sometimes technical people get religious. They decide something is the best and all tell each other and then wont believe anything else no matter what actually happens. Maybe jheads are really shit. Dont listen to others when your eyes are telling you the opposite. That is religion. Science is accepting reality even when it doesnt match what everyone else says. If Arcol works, use it.

@James_Newton and also, some people are just terrible at troubleshooting. J-heads work constantly, and amazingly for a plethora of people. I, personally, have access to MG hot ends, J-heads (IV and V), Budaschnozzles (1.2, 1.3), and an Arcol.

Budaschnozzles perform by-far the best, but are very expensive. The Arcol I’ve had no complaints about, the makergear nozzles are terribad and the J-head is 1/2 of the Budaschnozzle, and easily 90% of its performance and reliability. This isn’t religion, this is kilograms upon kilograms of filament put through these hot ends.

Now, I’m not trying to put Nicolas down, but more than likely he’s either overlooking something, or he happened to get a faulty J-head.

I have a J-Head mk V and haven’t had any blockage problems to-date.

Perhaps you are driving the filament too fast. If you are using Marlin firmware then there is a very good calibration procedure at http://reprap.org/wiki/Triffid_Hunter's_Calibration_Guide.

The key is to get the extruder steps-per-unit set up in your firmware correctly before you attach the hot-end. The Configuration.h file in Marlin contains the setting you need to change but you can adjust things ‘in-flight’ by sending an M92 Exxx to change the extruder setting to xxx.

Another thought if you are overheating - is the thermistor properly seated in the hot-end block and do yoiu have a fan cooling the peek block?

@James_Newton @ThantiK , this isnt about religion. Tons of people use j-heads with success. I never managed to make it work reliably, so i know that im doing something wrong. Im not technically savvy (yet) to troubleshoot all the possible 3d printing problems, so im asking and investing money to learn. Im going to buy another arcol, and since im building another printer, one will be for “production” and the other one for “development”. One will have an arcol and the other a jhead or any other hotend or part that i want to learn to use or is giving me trouble.

Thanks for all the suggestions.

Just for info, my temp is dead on, so, im going to recalibrate my esteps and slow down to 30mm/min extruding speed. Once i get it working reliably there, i will start accelerating it.

@David_Price looks like my esteps are not spot on.

The thermistor fit loosely (not very). Should i try to make it snug wrapping it with tin foil?

Part of religion is assuming that what is good for you is good for others. The tragedy of that is people assuming that what is good for others is good for them. If someone doesnt troubleshoot well, they can choose to try to improve that skill (nothing wrong with that) or they can just use what doesnt need troubleshooting and get the job done. If you want to take the time to learn how to heard a jhead, good on you. I was just pointing out that you have other options, and that it might not be you at all. Friday afternoon happens at the jhead factory, just like everywhere else.

My thermistor was not a tight fit, the main thing is to ensure it stays in the hole in contact with the metal surface for which I used Kapton tape wrapped around the heat block. I’ll post a picture showing what I mean…

@David_Price i get it, that is how i mount it.