Extruder Stepper skipping steps

Greetings all,

So my reprap with gen3 electronics is finally all assembled and running [almost] well. I'm using the repsnapper software and all the axis move well.

However, there seems to be a problem with the extruder, it always skips ( tries to rotate one step but fails). So in my mind this means that something is pushing back on the motor two hard or the motor isn't getting enough voltage.

I've tried adjusting the trimpot on the extruder controller board, which reduced the skipping but did not eliminate it.

also I've aligned the teeth of the gears and ground down any imperfections on the teeth to remove any resistance from them. No improvement.

Finaly, I had originally set the hot tip temperature to 190 degrees C and notice that the PLA seemed to be flowing with difficulty. So i upped the temp gradually until it flowed well, which was at 220 ish degrees C. (I'm assuming that my thermocouple is just reading the temperature incorrectly. ) This helped allot. But the stepper still skips.

also I've noticed that the hot tip-wood block assembly (as shipped by Techzone) seems to be taking allot of pressure. It was originally fixed to the carriage by a screw but the it was starting to rip the layers apart. so i reinforced it with some insulated copper wire raped around the wood block and then around the extruder body. But the force was so large that the wires stretched and the hot tip moved down about a centimeter.

So that's it. I'm not quite sure what to do next. Any suggestions are greatly appreciated.

Cheers,

J.A.

Some PLA do require high temperature. If it's 4043D which seems to be sold by Ultimaker and Makerbot, you do need 220C or higher. I calibrated my thermistor to a thermicouple as Nophead suggested and I found that it extrudes best with the least ooze at 230-240C.

What kind of extruder are you using? I put some silicone grease on the gears mine (Adrian's geared extruder). I also had to slide the motor as far away as possible to keep the gears from crashing to each other.

Well that's good to know about the PLA temperature. I did buy it from Ultimaker.

As for the the extruder I am using Wade's exturder. Like a said before the i checke the gears to run smoothely. but a though just occured to me. as the motor spins the suppor warps quite a bit. maybe that is causing the gears to colide. I will check that and post back.

But is it normal for the back pressures to get so high in an extruder tip. With a mixture of the heat conducted up the wires i used as reinforcement and the pressure the extruder support was starting to warp around the wires.

I use a 40 mm PC fan to cool the thermal insulator and keep heat from getting to the filament feed. You should be able to turn the big gear by hand and extrude with no trouble with your extruder motor turned off.

Do you have springs on the 4 screws to apply pressure on the filament drive? Wade's has probably enough force to break a wood or plastic thermal break unless you use springs and adjust the tension.