ABS stripping problem

everything was great with my mendelmax until about a week ago. i had to replace the filament as it had ran out. i had done this many times before with no issues. ever since that time, the extruder simply will not extrude abs. it always strips the filament. on my wade's extruder, i've tried to tighten the springs all the way down, loosen them up, higher temperature (250ish) lower temperature (220ish), cleaned the hobbed bolt a dozen times, adjusted the current on the driver, everything i could possibly think of. still, it gets about half way through the first layer of a calibration block and the strips.

PLA prints just fine. only the ABS is stripping. any ideas? i'm at my wits' end.

If you're using Skeinforge to generate your gcode, is it reducing the temperature for the first layer?

i'm using slic3r. the temperature seems to be consistent. it doesn't seem to affect anything. it's only ABS that gives me stripping problems. PLA only does it when i set the z-home too low

It sounds as if you might have clogged nozzle.

Can you extrude pushing filament by hand?

I think I can help. I need a bit of info from you.

1. Which brand of ABS (Makerbot, Ultimachine, 3DPrinterStuff, Other(s)) and which color.
2. Which hot end design?

For now, I can lend the following advice:

1. Set the temperature to 230, and don't fiddle with it. When troubleshooting, you should change only a single parameter at a time, returning frequently to the original settings, until you isolate the cause.

2. For now, take the springs off. If you (or the supplier) selected these at random, there is no way to know if the tension they provide is adequate. Tighten the nuts on the extruder idler until the hobbing on the bolt makes full contact with the filament. If you were extruding filament with the hot end removed, it should be tight enough so that you cannot prevent the filament from feeding without stalling the stepper motor. If the roller bearing is leaving a wide flat in the filament, it's too tight.

3. With the hot end COLD (yes, I mean turned off), turn your E0 motor current all the way down. If this is a Pololu-based driver, you should turn the POT counter-clock-wise so that the flat is in the 7 O'clock potition.

4. Send a series of fairly long extrude commands, and begin turning up the current slowly. Be sure to have a fan blowing on the driver heat sink during this, or you will likely trigger the thermal protection on the driver, which will screw with you. At the lower current settings, the tension on the filament cannot be overcome by the torque of the stepper motor. This will produce rattling in the large gear of your Wade's extruder. As you increase the current, the stepper will begin to overcome the tension, and begin to compress the filament. Periodically, it will release tension in the filament with quick reversals.

5. Continue turning up the current until the extruder begins stripping the filament. You will know this is the case because the quick tension releases will become less frequent, or more likely stop altogether. This is your current limit position. It should not go beyond the 12 O'clock position on the POT, unless you have a particularly strong motor.

6. Back off the current slightly, and reverse the filament out of the extruder (this assuming the filament is not melted into the heater block). You don't want a piece of chewed up filament going down there, right? At this slightly reduced current setting, the extruder will release excess tension in the filament, rather than strip it.

7. Once you have reached this point, it's time to start trouble shooting the nozzle. Try extruding slowly at first. Fast extrusion looks great on youtube, but in reality, faster speed does not translate into improved print quality.

Also keep in mind that not all ABS is exactly the same. Different colors, and different vendor's formulations can wreak havoc.

Good luck,

-Wildseyed-

thanks for the advice! i'll give it a shot. i'm using a j-head mkiv-b and ultimachine pla/abs. it's started giving me problems with pla as well now.

sounds like a blocked nozzle or your ptfe insert has overheated and contracted.

Your problem is most likely mechanical, try disassembling the hotend and soaking the metal bits in acetone. (not the PTFE or PEEK)

Make sure that they are squeaky clean before reassembling it.

PS: If you are able to take it apart cold, you will be able to see what the blockage is.