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Extruder advance

Posted by nebbian 
Extruder advance
April 23, 2017 09:51AM
Here's where I'm up to with extruder advance in Smoothie:

I've gotten a proof of concept setup working, just using a simple algorithm that just modifies the number of steps on acceleration and deceleration of the extruder.

Here I've changed the advance value on the fly a couple of times, to show the effect that advance has. These cubes were printed at 100 mm/s, with an acceleration value of around 300mm/s/s, which shows the problems with the current version of smoothie (ie, no advance possible). You can see the blobbing on the corners as the head slows down, as well as the filament starvation as the head accelerates away from a corner. Changing the advance value to about 1.2 or so on my machine seems to really clean up the print.

The algorithm doesn't handle different acceleration values all that well, so next up is to try the 'proper' algorithm as shown here:

My algorithm also only works when segments are used, so is better suited to deltas than other machines at the moment.

If anyone is interested in testing these changes, the github repo is here:

I can post some test binaries if anyone wants to try them.

Edited 1 time(s). Last edit at 04/23/2017 09:52AM by nebbian.
Re: Extruder advance
April 26, 2017 04:41AM
I was having some issues with retraction, so did a hack to disable this when retracting/unretracting. It seems to be working well now, but I'm keen to do a better fix for retraction.

I'm keen to see if anyone else wants to try it out. To enable, send:

M572 S0.1

Values from 0.05 to 0.15 seem to be in the right zone for my delta with a short bowden using PLA.
open | download - firmware.bin (366 KB)
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