Sunday night I performed the E step calibration on my month old Mini (I’m slow about it). The factory setting was 833 and the value I came up with is 813. The nice prints I have been enjoying have improved. Dimensions of holes are only too small by 0.1mm instead of 0.5mm. This and measuring the filament diameter seem to be step one for new users after the first print.
The question I have is why does this need to be calibrated? There is a stepper motor driving the gear that drives a shaft with teeth in it to push the filament through the nozzle. It seems like it should be constant math for the number of steps to the distance the outside diameter of the shaft moves. That is in a perfect world.
Could these items be causing the need for E step calibration:
- Is it that the diameter of the shaft varies from printer to printer?
- Is it the distance that the teeth dig into the filament based on the tension spring and filament density which effectively change the diameter of the shaft?
- Is it that the filament does not advance due to slipping every now and then?
If it is the 2nd one, then the calibration will need to be done each time the filament is changed. Also, I assume the heat from the nozzle flows up into the filament to the teeth pinch point such that it also depends on the history of the filament travel. For example if it is just feeding slowly, the filament will be hotter than if it was feeding quickly. Also, it seems that it would be hotter if it was just reversed.