Extruder missing steeps mid-printing

I'm having a trouble that I'm not sure if it could be a electronic problem.

After have printed some really good quality pieces with ABS, the thing is starting a new piece normally, after 8/10 layers, the extruder miss steps. The pulleys try to turn but it's like something doesn't leave do freely. This cause that the filament isn't extruded properly and missing milimeters of filament, also the filament that it's extruded is much more thin.

Checking the temperature with the thermistor is correct and measures the same than the temperature that the printing started, around 253/255ºC, I mean I have the same temperature at the begining than the problem starts. I have tried with different .stl pieces and always same problem, after 8/10 layers.

I'm using Pronterface, Sprinter, and slicing with Slic3r.

Does anyone know about this issue?

Thanks to everyone!

Edited 2 time(s). Last edit at 12/23/2011 04:02PM by pikelo.

More info:

Extruding speeds: first layer 12mm/s rest of layers 24 mm/s.

Here some of the .gcode file generated with Slic3r from the "half" of the file:

"...
G1 X137.549 Y93.442 E3.27694
G1 X139.558 Y95.451 E3.35817
G1 X139.558 Y93.874 E3.40324
G1 X139.126 Y93.442 E3.42072
G1 F720.000 E2.42072
G92 E0
G1 X122.994 Y83.907 F7800.000
G1 F720.000 E1.65000
G1 X122.741 Y83.654 F1320.000 E1.66101
G1 X122.471 Y84.227 F7800.000
G1 X122.014 Y83.769 F1320.000 E1.68095
G1 X121.843 Y84.441 F7800.000
G1 X121.306 Y83.904 F1320.000 E1.70437
G1 X120.748 Y84.188 F7800.000
G1 X121.225 Y84.665 F1320.000 E1.72520
G1 X120.608 Y84.890 F7800.000
G1 X120.190 Y84.472 F1320.000 E1.74343
G1 X119.632 Y84.756 F7800.000
G1 X120.122 Y85.246 F1320.000 E1.76477
G1 X119.664 Y85.630 F7800.000
G1 X119.201 Y85.167 F1320.000 E1.78497
G1 X118.779 Y85.588 F7800.000
G1 X119.206 Y86.015 F1320.000 E1.80355
G1 X118.805 Y86.456 F7800.000
G1 X118.358 Y86.009 F1320.000 E1.82302
G1 X118.015 Y86.509 F7800.000
G1 X118.496 Y86.990 F1320.000 E1.84400
G1 X118.188 Y87.524 F7800.000
G1 X117.731 Y87.067 F1320.000 E1.86393
G1 X117.447 Y87.625 F7800.000
G1 X117.730 Y87.908 F1320.000 E1.87628
G1 F720.000 E0.87628
G92 E0
G1 X123.160 Y84.227 F7800.000
..."

What I have tried is, send to print a .stl file with 253ºC at nozzle and 110ºC on heated bed. Once the first layer is done with that temperature and sticked well on heated bed, I changed the heatedbed temperature to 60ºC and see if the problem go on. The extrussion was done fine and no problem!! the only thing is that after a few layers and a "bulk" piece half-done, it un-sticked from the heated bed because not enough temperature to keep it sticked. The problem I guess there is not power enough to keep such a high temperature both in nozzle and bed at the same time.

But the weird thing was with the same configuration I printed really well a couple of days ago some pieces really good.

I could also be the cold end of the extruder getting too hot over time. Reducing the bed temperature would keep the extruder cooler.

---

[www.hydraraptor.blogspot.com]

So how do you advice I do usually the printings? Now it appears a new problem, taking place at the last 3 printings pieces, It was printings greatly, and suddently printing stops but no the extruder for a while (just a few seconds) and the it also stops, like no connection between machine and computer.

What could it be? Any advice or checking to do?

Thanks!

For the first problem, try reducing the speed of your prints to 15mm/s and under. Your hotend may say it's at 255º but depending on where the thermistor is mounted, it may be alot less. Also when you extrude large areas of infill, the hotend heating element may not be able to keep up. Print slower and if it helps, think about getting a more powerful hotend. If it makes it worse, it may be an extruder jam that can be solved with a fan or a new design.

As for the heated bed, keep the higher temperature to ensure the parts stay stuck and insulate the underside of the HBP with fibrous glass insulation. You can insulate the hot end while you're at it. This will reduce the duty cycle of the heating elements and facilitate faster printing.