Persistent extruder jamming

Hey everyone

I am about to throw this think out the window. I have been building a replica of the prusia air that has been going fairly well with the exception of getting consistent nozzle jamming. I can get to about 2 minutes into the print before the Extruder quits laying plastic and the filament bunches at the top of the cold end. I have read many answers to this problem and have since bought new ptfe, installed a fan pulling airflow over the thermal barrier and set temp to 235. I am thinking the is an easy fix to this issue and if someone could share some helpful advise to resolve I would be eternally grateful.. I have been on this issue for 3 month s now and anxious to at least get passed layer 1

Specs:
Marlin firmware
Extruder: what looks like a budaschnozzle replica [www.ebay.com]
Extuder Driver: Wades Geared 48:11
Filament:1.75mm ABS black from radio shack (recommended for afina 3d printer)
Bed temp: 115
Nozzle diameter: .35mm

If pictures are requires I will be happy yo upload on request

Thank you

Edited 2 time(s). Last edit at 03/11/2014 04:42PM by equinox86.

It's entirely possible that the hot end is the culprit, especially since the quality of Chinese-made hot ends is often quite poor. Can you feed plastic through the heated hot end by hand at a reasonable rate? If not, the hot end is the problem.

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Cameron

Firstly Thank you for your reply.

What is a reasonable rate? I notice that there is resistance but I figured that the nozzle itself what causing that. Filament continues to flow but it does take a bit of force. Sometimes I hear pops and see bubbles in the filament. Could this be caused by the hotend as well?

Quote
equinox86
What is a reasonable rate? I notice that there is resistance but I figured that the nozzle itself what causing that. Filament continues to flow but it does take a bit of force.

You should be able to get a consistent stream of plastic coming out of the nozzle.

Quote
equinox86
Sometimes I hear pops and see bubbles in the filament. Could this be caused by the hotend as well?

This is probably caused by moisture in the filament.

The way I see it there are two possible issues causing your problem:
1. The hot end is getting jammed up, possibly due to bad manufacturing or contaminants in the filament.
2. The filament has too much room to buckle underneath the hobbed bolt. Either the gap from the hobbed bolt to the guide hole is too long, or the guide hole is too large of diameter.

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I definitely notice the buckling above the hotend. there is about 12 mm of gap from the wades extruder to the hotend. Is there less gap between on something like a jhead?

I cant really say anything about the quality this is my first by. There may be alot of humidity- I will get a dehum.

I am under the belief it is the hotend.
First they ship me the wrong teflon tube, then the first one they sent snapped when Un tightening, I wouldn't be surprised if this thing is crap.

Edited 1 time(s). Last edit at 03/11/2014 11:42PM by equinox86.

A gap between the extruder and the hotend? The extruder should slip into the hole on the bottom of the extruder and bottom out against the extruder. Then either clamp into place (using the flat clmap that slips into the grooves on the hotend) or use 2 screws from the front to hold it into place.

Thanks for the feedback

I was able to take some leftover ptfe and glued it to the bottom of the Extruder to connect to the hotend. It now creates self clearing jams while printing without the filament bunching up at the top

The odd thing is when I extrude from pronterface I can do 200+mm about 10 mm off of the hotplate @100mm/min without a single jam. When printing it seems that the gears move at a more brisk pace. I checked slic3r setting and it shows 60mm/sec which I thought was weird. Any suggestions on an appropriate starting speed for Extruder mm/min in slic3r?



Edit: AT LAST!!!. The issue was a few things. Here was the fix in order of importance for those who bought this hotend.

Cause: Ptfe thermal barrier is shipped with 3mm.
Fix: order budaschnozzle thermal barrier from lulzbot.
This may need to have the exterior diameter shaved down. You can use a drill to hold the barrier and roll it around a piece of sandpaper to trim the exterior to fit the mounting plate and ceramic like connector.

Cause: thermal barrier aluminum heatsink does not remove the heat from the ptfe thermal barrier. This causes the Melt zone to creep up the ptfe tube.
Fix: mounted (superglued) a 40 mm fan to the xcarriage. You may need to attach a duct to force the airflow. I made a makeshift one out of a cardboard FedEx envelope and taped it onto the fan (since it needed to be remove able and I didn't want to dislodge the fan) setting is M 106 S160

Cause: Too much gap between wades extruder and hotend mounting plate. This causes the filament to coil and snap during prints. The gap is built for mkv and the cheap China one is flush
Fix: used one of the spare 3mm ptfe barriers I had. Trimmed it and glued to the exit hole of the wades extruder. This flushed the wades extruder to the hole in the hotplate.

Cause: Z axis was calibrated incorrectly. This caused extreme back flow and causing jams.
Fix: used reprap calculator to resolve.

Whether or not the speed in slic3r was right or wrong I don't really know. I took the speed down to 25mm/s. Prints are long but after some fine tuning I think it will be worth it.

I am about an hour in and printing strong... thanks again to everyone and I hope my comments help.

Edited 3 time(s). Last edit at 03/12/2014 08:08PM by equinox86.