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Sunday, April 05, 2009

A gripping read

I have done some work comparing the amount of grip that different extruder drive methods achieve. I measured the amount of force the following devices gave before the filament slipped: -





A 4mm splined shaft.
A 13mm timing pulley
The original M5 thread drive
A 13mm knurled wheel
A 13mm threaded "worm" pulley


The results where as follows: -

 PCL HDPE ABS PLA
4mm splined shaft 2.5 Kg 3.0 Kg 5.0 Kg 7.5 Kg
13mm timing pulley 4.0 Kg 10.0 Kg 8.5 Kg >8 Kg
13mm knurled wheel 5.0 Kg 10.0 Kg 12.0 Kg >12.5 Kg
13mm M4 worm pulley 6.0 Kg >12.5 Kg >12.5 Kg >12.5 Kg
13mm M3 worm pulley 8.0 Kg >12.5 Kg >12.5 Kg >12.5 Kg
M5 thread 9.0 Kg >12.5 Kg >12.5 Kg >12.5 Kg

The red figures are lower or marginal compared to the force required to extrude 0.5mm filament at 16mm/s.

More details in my blog hydraraptor.blogspot.com/2009/03/pulling-power and hydraraptor.blogspot.com/2009/04/all-torque-and-no-traction.
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4 comments:

  1. Jay SwiftApril 05, 2009 10:04 PM

    The worm pulley design is what is in the stratasys machines

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  2. Adrian BowyerApril 08, 2009 11:07 PM

    This is really useful stuff. Zach started all this with a range of experiments. The most useful thing about his and Nop's (and my) results is that it gives us a range of working solutions that we can use in different designs. For example, I want to do two things in the near future: one - to make a really small extruder, and two - to make one that works with drink bottles cut into strips. These may well need different solutions.

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  3. nopheadApril 08, 2009 11:41 PM

    If you want to make really small extruder you might consider feeding it with 0.5-1.0mm filament from a static version of the current extruder. That way the forces get much less, although you do put the plastic through an extra heat cycle.

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  4. Adrian BowyerApril 09, 2009 1:17 PM

    I have a NEMA 14 that will do about 10 N-cm (http://uk.farnell.com/8425884/industrial-controls-automation/product.us0?sku=ASTROSYN-MY4001), which should give me 4 kgf at 2.5mm radius (which is the stepper's shaft). From your numbers here:

    http://hydraraptor.blogspot.com/2009/03/rheology.html

    that should just about be enough to work ABS and PCL with a 3mm filament. I'll try it and see.

    If it works it should give a very light and compact extruder design indeed - about a credit card in plan view.

    ReplyDelete