Sizing Your Extruder Motor

Hi all!

I’m currently working on improving a set of machines in Boise, Idaho. One of the limitations we’ve been hitting is that our extruder motor isn’t strong enough, so I did some digging to figure out how to calculate the power required in a motor to extrude plastic.

Trying to find a way to calculate this wasn’t the easiest thing. None of my professors could tell me how to size a motor properly either through a rule of thumb or a calculation, so I did some Google searching. Finally, I came up with a few publications and a powerpoint on rheology in plastic processing, specifically for extrusion, from the University of Thessaly. Reading through the powerpoint gave me a lot of useful information about how to calculate the size of the extruder motor, shapes of extruder screws, how to design extruder screws, and a lot more. From this, I did some calculations by hand, and after taking up a few pages in my notebook to define variables, write equations, take notes, and make sense of what was happening, I decided to make a spreadsheet what I could quickly reference to size motors based off my desired throughput of any given plastic.

Here are the links to the spreadsheet I created, and the powerpoint it was based on:


What size motor and reducer have you been using?

@chrisdagher, that’s extreme helpful information and exactly what I needed for extending my skills in this field. thank you very much for the work you’ve put in there.

@fullcirclesupply : depends on your screw but I assume it’s an industrial ‘universal’ screw from the bazar or alibaba with no specials like mixing addons or secondary flights… in the 500 Euro range. If so, a 25mm screw diameter with 60 cm usable length is around 800-1200 Watt|1500RPM|3phase via inverter and a reducer at 1:40. Also depends a little on the quality you want. More throughout needs more power but from what I saw you might be fine with 1.4 – 2.0 KW as well.