Clicking Extruder Noise
The extruder periodically makes a loud "clicking" or "knocking" sound. This is caused by the stepper motor missing steps or slipping on the filament. The usual cause is too much back pressure in the melt chamber. If you are using the original Rigidbot hot end with the Teflon Feeder Tube then temperature limitations of Teflon (>240°C) is the predominant cause of this restriction.
Back-pressure occurs when the amount of filament getting extruded is less than the amount of filament that the printer expects to be extruded. There are a variety of reasons this can happen:
- Partially blocked nozzle. Do a "cold pull" (see wiki) to clean out the nozzle. Use a piece of foam or sponge around the filament to wipe off any dust as the filament goes into the extruder (dust will build up in nozzle).
- Restricted PTFE tube due to over heating. Disassemble the extruder and verify that filament can slide through the tube. If this is not the case, the tube needs to be replaced. A temporary solution is to bore out some of the tube, but the issue will likely return in this case.
- Uncalibrated extruder. All steppers are slightly different. You need to very accurately measure that your extruder pushes 50mm of filament (through heated hot end, into free air) when you tell it to. If not, adjust your extruder steps/mm.
- It is possible the heater is unable to keep up with flow demand. Increase heater temperature, retune the heater gains, or reduce print speed.
- (Least likely) You may need to up the current to up the current to the extruder stepper slightly.
- Filament pressure between hobbed gear and plastic arm too high
- Alignment of the hobbed cresent in the extruder drive gear to the filament opening in the heater block. I had to machine material off the back of the gear for a proper alignment.
- Extruder drive gear teeth not sharp enough to grip the filament. Buy new ones from another vendor that are machined from a quality material.
- Extruder drive gear spring loaded filament presser, could have multiple issues. 1) The little bearing does not line up with the hobbed cresent of the drive gear. 2) Low spring tension 3) Excessive friction at the pivot, check that the pivot shoulder screw is not too tight.
- The set screw on the extruder drive gear is not holding it in place. If you notice scratches on the drive shaft of the stepper motor this is a likely one of the causes of your problem. Recommend blue lock tight in the threads of the lock screw while securing it down. Also run a black sharpie between the drive shaft and the extruder drive gear and see they remain aligned after some print jobs.
- Low quality Filament. Diameter of the filament too large or diameter not consistent causing fluctuations in extrusion speed.
It's also possible that one coil of the stepper is not getting power causing the motor to not turn. This can cause the motor to bang more than click.
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