Filament Monitors - Closed Loop Extruder?

DocTrucker

I've seen little bits of the recent laser filament sensor and hear murmurs about the impending beta testing of the magnetic filament monitor. How close are we to being able to have a closed loop extruder - or at least an extruder that can self tune? Capacity wise is this something that has to wait for Duet 3?

I've put a fair effort into tuning my extruder with linear/non linear correction for the equivalent of 10 through 90mm/sec head speeds but feel I'm fighting a war of attrition against a printer that can easily win by any number of factors shifting a little - including coming to the end of a spool of filament. My Most recent struggle has been over extrusion on short vectors but not longer ones that appear to be unrelated to temperature or pressure advance.

A simple (from the user perspective) e-steps like calibration for the sensor (accept material differences are hard to accommodate for) followed by an heater auto tune like process for the feedrate linked extrusion distance correction would be great. Better still would be live, but think that is asking something very difficult down long wires and also quick enough to cope with microstepping.

If this is something the magnetic sensor that is due for beta test is likely to be able support this and this will be acjhievable with a Duet Ethernet I will be very happy buy an ethernet and join the trial - if you'll let me!

dc42

This is something that we plan to try with the magnetic sensor when we have a stable mechanical design. In principle, with a filament monitor between the Bowden tube and the hot end, we could calibrate pressure advance automatically, and if necessary implement more advanced algorithms such as non-linear pressure advance.

DocTrucker

That sounds great. I think that will make a huge difference to the amount of time spent tuning. Much of this is likely to be possible on the current generation of Duets and in what sort of time scale are you likely to require willing (paying) volunteers?

Alexander Mundy

@dc42 said in Filament Monitors - Closed Loop Extruder?:

This is something that we plan to try with the magnetic sensor when we have a stable mechanical design. In principle, with a filament monitor between the Bowden tube and the hot end, we could calibrate pressure advance automatically, and if necessary implement more advanced algorithms such as non-linear pressure advance.

I have started working on these same 2 calibrations as a personal project with a sensor and independent processor / display platform in what little spare time I have. That is how much I think it will save calibration time, so if you implement them directly in Duet and with a commercially available sensor I think that would be a major attraction.

genghisnico13

I would like this feature too, measuring extrusion at different speeds for non-linear extrusion takes most of my tuning time.