Extruder missing steps - Tmc2130 tuning?

I've got a pretty much new Prusa I3 that just can't lay down a consistent extrusion line. I've tried a different stepper motor, different cable, different Einsy board, different drive gears, different filament, bed heater off, etc , to no avail.

Typically this shows as consistent angled banding on all sides of a test cube. Yesterday a ran a cube that had z offset too high, and it really depicts the issue.



I looked at the gcode to determine the travel distance versus extruded filament distance, and was able to get a good estimate of the interval between each artifact from a picture of the cube bottom. The extruder uses 32 microsteps and 280 steps/mm. The artifact spacing is about 3.6-3.8 mm, and that works out to just about 32 steps between artifacts if I did the math right.

So it's missing steps right at every full step. I assume it's missing steps, though I don't know how to identify that. It certainly stops extruding for a short bit.

Could anyone help advise what tuning parameters I might try to help correct this problem?

I think you're talking about the gaps in the extruded diagonal lines. This appears to be under extrusion. This could be because the extruder isn't hot enough or because the extruder isn't calibrated properly or because the filament is slipping in the feeder gear.

There are settings in Marlin and your slicer that'll increase the amount extruded by a fixed percentage.

There are calibration web sites that will step you through the cal process.

Unfortunately we're past the easy fixes. I've tried every reasonable temp on the hot end, there's no change. Altering the flow rate won't really do the trick, as that's going to impact the entire extruded line, and not fix the missed steps at the full step point.
The extruder gears have been checked, rechecked, replaced, new stepper applied, different tensions tried, all with no effect.

Typical reasons for lost steps:

• microstep setting too high
• acceleration too high
• top speed too high (rarely the case for an extruder)

Have you done the "remove the nozzle and do a 100mm cold extrude" to make sure the steps/mm setting is correct?