Mig 4-roller extruder?

eBay page for 4roller extruder

I saw this while searching for MIG drive rollers for my custom extruder. What do you think of this design? 4-roller (opposing) with a brass guide shaft for the filament between the two sets of opposing drive wheels. I would get all wheels to be driven with a gear off a single NEMA23 geared stepper (50 or 60:1).

Any thoughts/comments? I am especially interested in any thoughts on making the entire assembly adjustable in tension (which this one in the ebay link is) but with all rollers being "driven". Or do you think I could leave the bottom two rollers free wheeling?

thanks
Jon

I think at 50 or 60:1 it's going to have a very low maximum printing speed, especially if you're using 1.75mm filament.

Edited 1 time(s). Last edit at 03/04/2015 04:48PM by the_digital_dentist.

I'm not too worried about the gear ratio. I know others are using geared steppers with similar ratios to drive the extruders.

Quote
jonnycowboy
I'm not too worried about the gear ratio. I know others are using geared steppers with similar ratios to drive the extruders.

Because they are doing it does not mean it works well.... Ideal ratios should be calculated properly with retraction speed being a priority. My 2:1 extruder can drive my printer at over 150mm/s with .5mm nozzle and .3mm layers.

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