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e calibration

Posted by waitaki 
e calibration
December 03, 2012 02:50AM

Who calibrates their extruder with the..
1) "mark the filament with a pen and see how far it travels" method?
2) And who uses the mathematical formula?
Re: e calibration
December 03, 2012 03:13AM
I just re calibrated my extruder using the marking method, and used the figures from that to calculate for the new step settings . . . .
Re: e calibration
December 03, 2012 06:40AM
There isn't an exact formula as it depends how far the plastic is pressed into the teeth of the hobbed bolt / pulley. For a given spring pressure soft plastic will feed slower than hard plastic because it sees a smaller effective diameter.

Edit: wrong way round!

Edited 1 time(s). Last edit at 12/03/2012 10:34AM by nophead.

Re: e calibration
December 03, 2012 07:40PM
Yeah, that makes sense Nophead. The reason I touched on this, is, using a V shaped hobbed groove, the filament cannot sit on the bottom - it's not meant to, (unless its a half round groove of course.) Therefore, in this case the bolt diameter is not measured at the root of the groove but at the inside edge of the filament that sits in the groove - this is the effective diameter of the bolt in the formula.

Re: e calibration
December 03, 2012 08:06PM
With normal hobbing the uncertainty is how far the teeth penetrate the plastic, which is bounded by the thread depth. With a V it could be more variable, a bit like a Variomatic gearbox. It will also depend on filament diameter, If it smaller it will feed more slowly, which is definitely a bad thing.

Re: e calibration
December 04, 2012 02:52AM
I use the mark with a pen then do the maths to calculate the setting

Experimenting in 3D in New Zealand
Re: e calibration
December 04, 2012 06:08AM
Also get sure to measure by actually extruding filament (heated hotend etc) at an usual extrusion speed.

I've seen variations between length extruded while disconnected from the hotend and when actually extruding (resistance is futile, but can be measured).

This should normally not happen if your extruder is perfect, but perfection is only a goal.

Most of my technical comments should be correct, but is THIS one ?
Anyway, as a rule of thumb, always double check what people write.
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