1 Topic by satman49

  • satman49
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Topic: filament input and output

I have calibrated the extruder to extrude 100mm when called for.I always wondered what the output in mm was.I ran 100mm in and measured the length of filament output.In my case it was 1130mm with a .4mm nozzle. I really don't know what difference this makes,just an observation.

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2 Reply by jagowilson

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Re: filament input and output

I really need to find a good book on polymer extrusion because I would like to understand this relationship more. Anyone have suggestions?

3 Reply by Fredjikrang

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Re: filament input and output

It is just a volumetric relationship. If you measure the diameter of the filament that goes in, find the cross section and multiply by the length, and then compare that to the measured diameter of the out coming filament, and find the volume in the same way. They should be equal.

4 Reply by mwille (edited by mwille 2015-01-29 02:48:13)

  • mwille
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Re: filament input and output

Isn't it just a matter of volume in = volume out? 

I'm going to guess at the average diameter of filament used was 1.7mm.  Then radius = .85, so volume in = .85^2*pi*100 = 226.98 mm^3.

Now a guess for the average diameter after extruding was .48mm.  That would be .24^2*pi*1130 = 204.48 mm^3 volume out.

So, it's reasonable to assume that if the actual diameters were used, they should be even closer in total volume than that.

Edit: beat to it by Fredjikrang

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5 Reply by jagowilson (edited by jagowilson 2015-01-29 05:51:01)

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Re: filament input and output

mwille wrote:

Isn't it just a matter of volume in = volume out? 

I'm going to guess at the average diameter of filament used was 1.7mm.  Then radius = .85, so volume in = .85^2*pi*100 = 226.98 mm^3.

Now a guess for the average diameter after extruding was .48mm.  That would be .24^2*pi*1130 = 204.48 mm^3 volume out.

So, it's reasonable to assume that if the actual diameters were used, they should be even closer in total volume than that.

Edit: beat to it by Fredjikrang

Thanks for the explanation. I think i communicated poorly. What I'm interested in is the extruded diameter and how this is theoretically approximated based on, I can only assume, the internal geometry and diameter of the nozzle. I'm aware to some extent of how slicers approximate this using geometric models of extrusion, but I'm more curious about the real world factors.

6 Reply by elmoret

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Re: filament input and output

That's called die swell, and it is roughly 20% though it depends on nozzle geometry, polymer, and nozzle temperature.

It also doesn't matter much in our case since we don't extrude to free air in 3D printing (though you do in filament production).

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