Wade's geared extruder keeps jamming

Hi everybody! I'm having some troubles with my geared extruder for my Prusa i3 Rework. I've now had it jam a whole bunch of times on me and I'm having trouble figuring out what the problem might be. I'm using the Wade's geared extruder with the gears perpendicular to the X axis, that comes with the i3 Rework.

Couple questions:

1) How important is the fan that's mounted on the extruder, and what function does it serve? I have been having trouble keeping the extruder hot enough with that fan running, but I have a feeling that I need to have that fan on the J-head's cooling fins to keep the filament solid until it reaches the heater block. Am I right in assuming that's what it's for? Is there a way to connect it to the RAMPS board so that I can control its speed?
2) Is there a way I can get a little more warning that the extruder isn't extruding? By the time I catch it there's a few centimeters of filament backed up inside the extruder, just past the hobbed bolt, and it's a lot of effort to clean all that out.
3) If I experience another jam, what is the most efficient way to clean out the extruder body and J-head so I can reset and try printing again?
4) What is another extruder that may be less prone to jamming up like this?

Thanks very much in advance for any help y'all can offer.

1) If you are running with only a single extruder you can connect the fan to your D9 output if you are using a ramps board. You can then control fan speed in your printer host.
2) Have you tuned your stepper drivers according to the calibration guide? Is the motor not turning like it should, or is the hobbed bolt digging holes in the plastic and not forcing it into the extruder? What Temp are you running plastic, also ABS or PLA? As of right now there is no motor feedback supplied to the rest of the system to let it know if things are not operating as they should.
3) You can get picks off of amazon that fit in the nozzle to clean out jams that fit up through the nozzles hole. Otherwise taking it apart may be your next option.
4)I have been running the same extruder for months with only one jam. Most jams are created not through hardware but low quality filament. Cheap filament often has imperfections in it such as particles too large to be pushed through a .4mm or so nozzle or excess moisture is causing issues. Your best bet may be to get some better filament. I have been using 1.75mm Hatchbox Pla with no issues, even though it is cheap.

Edited 1 time(s). Last edit at 07/30/2015 12:09AM by gmckee.

I've been having troubles with this on and off but have been fixing other things about my printer.

1) As per my other postings in this forum, that ended up being a heater cartridge problem that's now been solved. After installing the correct heater resistor and re-doing my PID settings in the firmware the hotend is heating up beautifully.
2) I adjust my steppers when they skip or make noise, but beyond that I'm not really super sure how to adjust them perfectly. In particular since the extruder motor isn't on all the time, how do you tune it? If it doesn't heat up too much, is it okay to err on the side of caution by turning the current up a little more? What exact symptoms would I be seeing if the extruder motor were underdriven?
3) The geared extruder is thankfully pretty easy to take apart and I've been able to get all the little PLA bits out of there using compressed air and a wire brush. Nothing ever seems to completely clog the nozzle, as in when I get one of these jams I can clear it pretty easily by reducing the hotend temperature to ~100-120°C and gently pulling the filament out. The filament is sticky enough that usually all of it comes out with one pull.
4) I, too, use Hatchbox PLA for the same reason. My RepRap Huxley used to jam constantly with cheap filament and I had to switch to the good stuff. My experience with the Hatchbox 1.75mm PLA has been great overall.

I'm tempted to just re-do the extruder with a bowden type cold end and a tube, because I'm also annoyed at how much the machine vibrates with x-axis movements. I've got the hardware to make [www.thingiverse.com], but I haven't found a suitable bowden mount for the hot end (mine is a pretty standard J-head hotend). If this problem is caused by the extruder stepper driver, then it would probably persist with the bowden setup anyway.

Could it be that my hobbed bolt is out of alignment? I notice every time this happens, the filament bunches up under the idler just outside the hole going down into the J-head, then the hobbed bolt cuts into the filament and it stops moving....

Probably is just a clogged nozzle. Time to print out several 20 cm cubes.

Hi,

I guess it's all about 20mm calibration cubes ?

Villainous, you don't want to add problems while trying to cure others.
D9 is for parts cooling only.
The hotend fan must be always 100% on.
The proper wiring is directly on your 12V PSU. Stick to that.
Clogged hotend mostly comes from insufficient cooling.

If the hotend fan cools the heatblock too,
insulate the heatblock and/or use a fan duct
to concentrate the airflow to the coldend.

Check the hobbed bolt is properly alligned with the filament's path.

To tune the stepper drivers, you need few things :
1/ a multimeter.
2/ the reference amperage rating of your motor
3/ some calculation
4/ a ceramic screw driver (to avoid shorts)

The formulas is : (reference amperage rating) * 8 * Rs = Voltage output.
for A4988 drivers : Rs = 0.05 Ω
for RV8825 drivers : Rs = 0.1 Ω

Now you set your multimeter to voltage measurement,
and adjust the variable resistor to the required voltage,
by turning gently the screw clockwise+ ccw-.
Check by measuring the voltage from the resistance centre to the ground pin :
(A4988)
(DRV8825)

++JM

Just attached a pic of the problem when it happened last. The filament bunches up *then* the hobbed bolt gouges into the filament and stops moving it. After getting the hotend PID autotuned and everything, the hotend heated up pretty fast and I watched it stay hot for a whole print—printed myself a new herringbone wade gear that ended up not fitting my hobbed bolt anyway. I'm not sure if I'll be able to find the reference voltage for the stepper motors, as I bought them as part of a kit, but I'll look later this evening.

I started taking apart the extruder, removing it from the printer entirely, and noted that the j-head is a little loose in the groove mount. Not sure why. I shimmed it into place better. Now the filament moves smoothly through the head, but not 100% frictionless. I'm gonna use the next few moments my printer is actually working to print a new wade body.

Does the photo I posted fit with the hypothesis of the extruder stepper motor being tuned wrong?

Maybe. If the stepper is trying to push much too much through the nozzle, it will clog like this.

Do a 100 mm extrude command and measure if 100 mm filament goes through.

I found that 100mm extrude extruded 100.5mm of filament so I adjusted a little and now it's spot on. Made a few more adjustments including loosening the idler screws juust a bit since I heard that too-tight idler can cause extrusion troubles. Gonna try a test print in a minute here.

Those adjustments seem to have worked. I've now printed three fairly large things without trouble, so hopefully it'll continue to work now.

Thanks everybody for your help!

Yea at first my wades idler was too tight and it squashed the filament which caused it to get stuck in the tube. I took off one spring on the idler, and now it's great.