A possible improvement for bowden extrusion?

I have noticed in using my RRP Huxley that one of the biggest issued with bowden extrudes seems to be the delay in getting the filament moving in the hotend after you start the extruder. Would it be possible to set up a control system that used a sensor located immediately above the hot end (an optical mouse sensor perhaps?) to sense filament feed rate into the nozzle itself and use this to control the XY motor speeds (making sure the expected amount of filament is deposited in a given location)? It might also be used for automatic esteps calibration, out-of filament detection, and maximum printspeed detection! I doubt I will have time to try this idea, so if anyone does, please share the results! Maybe this could be the secret to perfect-looking top infill at high speeds!

No Idea if this would work at all, but I figured it was worth suggestig.

I had the same idea. I was going to use a lego tire on a 200CPS (counts/revolution) encoder but the current arduinos do not have the ability to handle that high of a encoder reliably while printing.

I was thinking of of using the STM32F4 Discovery board as my new controller but I am to busy to test anything out. The Davinci printer uses an encoder and saves the revolutions on the eeprom on the cartridge which is a great idea, I wish they took it further and had it store the ideal temperature and cooling fan settings as well.

It is called backlash. You need a stiffer filament guide. I have had good luck using motorcycle brake cables. Only thing is they have a bit of oil in them so you should run a 2-3 hour print to work the oil out of it. The print will look terrible at first with lots of bubbles.

I am looking at modifying the firmware for the Duet controller board to add a configurable delay to the movements of the XYZ stepper motors, so that the extruder can be given a head start. Other techniques may also help, such as computing the extruder motor stepping rate not only from the desired extrusion rate, but also adding a term proportional to the rate of change of desired extrusion rate.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].