Direct Drive 1.75 mm -- Not Enough Torque?

I've been having issues recently with my extruder. I use a direct drive extruder, with an mk 8 drive gear and 1.75 mm filament. Recently, the extruder has been having trouble extruding, even at modest speed settings and correctly-tuned stepper drivers. When extruding, the stepper constantly clicks, unless the heat is set high (around 215 for PLA). Is this due to a faulty stepper? What could I do to resolve this issue? Thanks!

I had the same issue when I updated my firmware to marlin 1.1.RC1.
I allowed the extruder stepper to be turned off when not used, but in the new FW this seems to be done immediately. The pressure in my Bowden tube pushed back the filament at any bend in the print.

#define DISABLE_E false // For all extruders

-Olaf

Clicking meeans it looses steps. This is either because the driver does not deliver sufficient current (which can be adjusted), or the motor/stepper combination is simply overloaded (the motor should be pretty hot in this case).
215°C is not realy high for PLA, depending on the exact material it might make sense to go up to 220°C, or even more.
You could have some issue with the hotend that increases the pressure needed for extrusion. Check that you don't have any heat creep (molten filament in or close to the heat barrier), make the retract as short as possible (you only seldomly need more than 1mm), check that no dust or dirt block the nozzle (use a sponge or similar to wipe dust of the filament while printing).
Maybe you are just trying to print to fast, try lowering the speed.
If you use a small nozzle (0.2 - 0.3) but set the software to 0.5 it is very likely that the extruder will not be able to deliver the force needed for extrusion at normal 0.5 speed. Keep in mind that changes in diameter change the actual extruded volume squared.

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I had this problem, and came to the same conclusion. I replaced my Mk8 with a Greg wades geared extruder. The mechanical advantage the gears gave me was enough for it to extrude.

I did some research on this and I came to the conclusion that in order to get a 1.75mm direct drive extruder to work well, you need to get several things right:

1. A long (48mm or longer) stepper motor, assuming it is a Nema 17. Shorter motors have insufficient torque.

2. Run the stepper motor close to its rated current, e.g. at 85 or 90%. This requires the stepper motor to be carefully chosen so that standard stepper drivers can handle that current.

3. A hobbed pulley in good condition with lots of grip.

I find it easier to use 3:1 geared extruders and smaller motors.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
I did some research on this and I came to the conclusion that in order to get a 1.75mm direct drive extruder to work well, you need to get several things right:

1. A long (48mm or longer) stepper motor, assuming it is a Nema 17. Shorter motors have insufficient torque.

2. Run the stepper motor close to its rated current, e.g. at 85 or 90%. This requires the stepper motor to be carefully chosen so that standard stepper drivers can handle that current.

3. A hobbed pulley in good condition with lots of grip.

I find it easier to use 3:1 geared extruders and smaller motors.

Seriously. Way overkill.
I have run using a 40mm Nema 17 with 3.9kg/cm torq at 0.8vref - bowden 1.75 with E3Dv6. Usually print PLA at 220c. MK7 bit.

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I think it's important to recognize that the temperature readout may not be accurate. If it says it's 220C but it's actually 180C, you will run into problems extruding. If you have a thermocouple and a DMM you can check to see if the temperature is close to what the printer controller reports. If you don't have a thermocouple, try turning up the temperature before deciding that the extruder is the problem.

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Quote
the_digital_dentist
I think it's important to recognize that the temperature readout may not be accurate. If it says it's 220C but it's actually 180C, you will run into problems extruding. If you have a thermocouple and a DMM you can check to see if the temperature is close to what the printer controller reports. If you don't have a thermocouple, try turning up the temperature before deciding that the extruder is the problem.

I believe it's important to note how temperatures in consumer 3D printers are inaccurate in general. Or at least should be considered inaccurate untill proven otherwise.
I do not see the temperatures themselves as particular important though : meaning it really doesn't matter wheter it shows 200 or 220 as long as it is consistent.

I have printed PLA at 240 on my E3Dv6. Mostly at 210-220 though, so do not see 215 as high.

I have not tried using thermocouplers to check temperature, but I've read a good deal about it, and considering the need to position them rather accurate... preferebly inside the molten filament ( ! ), I do not see it as a viable method really.
Considering the Price of £5-10 for the thermocoupler and another £6-10 for an amplifier board and the complexity of hooking it up, both in electrically, firmware wise and mechanically to the hotend.... I just don't see it as a good way of doing it.

I'm using original E3D thermistor on my E3Dv6 and PT100 sensors on my UM2 clone. On E3D I print PLA at 210-220 while I print at 200-205 on the UM2. Granted, I havn't printed THAT much on UM2 clone yet, but there are many other aspects to take into consideration other than plain temperature readings: like the type of hotend.

My 24v UM2 hotend simply just cannot print over 96mm/sec (larger surfaces without any letup). It simply can't melt the plastic fast enough. I have tried cranking the temperature way up, and it doesn't help a bit. On the E3Dv6 I can print fine at 120mm/sec (have had no need to print faster).
I put it down to the smaller meltchamber and/or the way the heater cartridge is placed in the UM2... but everything Counts.

I even changed it to a way more powerfull Nema but without any change.

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My Instructables - both total newbie instructables and some for intermediate users.
My Designs on Thingiverse
YouTube channel containing a few 3D printing videos - they are videos for my Instructables, and mostly not standalone.
Ultius / Tantillus Thingiverse Group