MFI (Melt Flow Index) and Filament  

MFI (Melt Flow Index) and Filament

Would an MFI test that is tailored to filament give relevant information about printability and settings?

The MFI test takes a heated vertical barrel, filled with plastic, with a plunger with a fixed weight to push the molten plastic out of the bottom through an orifice.  So like an extruder.   How many grams of plastic that are fed out over a period of time is the Melt FLow Index.  The higher the number the more plastic expelled.  When you start adding pigments to plastic, the melt flow index goes up (less viscosity) and is taken as an indicator of a change in the polymer- often seen in lower resistance properties.

My thought is instead of the cylinder filled with molten plastic, to take something  like an standard hot end (E3D V6) with out the gears and extruder and  you have a column slightly larger than the filament and then stopper than pushes down on the filament.  The amount of time it takes to feed a representative sample of filament (100-150mm) at a temperature with a given weight would indicate how the filament would process.  

I've done this by hand with an old printrbot with the gears disengaged, and with a Prusa Mini, by taking off the Bowden tube and feeding filament straight in.  By pushing the filament, I could feel how the filament fed at a temp.

My thought is that you could show how the amount of time it takes to feed a unit of filament, varied by temp, would show what processing temps would be best for filament flow.  Also, looking at the weight (force) effect on flow.

Using the actual hot end would show how the heat transfer and melt zone are working to affect the pigment melting and flowing.

My thought is that with a table of weight (feed rate proxy) versus temperature would yield as response 'surface' that would show how consistent a filament might print.  If temp affects the feeding quickly, or the amount of force varies the feed rate, you'd know that the printing would be very sensitive to printing parameters.

I know that when I first start printing a new filament, that I'd like to have that kind of data rather than "Print at 235-260C".

Is anyone doing testing like this?

Any thoughts on how much 'pressure' extruders exert on filament?