LESSON 2.1 · 2:29 · CHAPTER 2 · THE EXTRUDER
A pump that leaks backwards
A single screw's output is drag flow minus pressure back-flow: rpm sets only the drag, and the nozzle decides how much actually leaves.
Predict · at 0:50 in the video
A 40 millimetre screw with a 3 millimetre metering channel, turning at 100 rpm. Roughly what does it put out, with nothing pushing back?
About 45 kilograms an hour. The drag flow works out to 11.4 cubic centimetres a second. At 1.1 grams per cubic centimetre, that's 45 kilograms every hour.
Further reading
This course is our own. These books go deeper.
- The economics of Big Area Additive Manufacturing, Post et al., Solid Freeform Fabrication Symposium, 2016
- Additively manufactured carbon fibre-reinforced composites: state of the art and perspective, van de Werken et al., Composites Part A, 2020
About the numbers
Simulations in this lesson are our own. Where a number rests on an assumption or a single source, the video marks it with an asterisk and says where it comes from.
Up next · 2.2 · 2:25Why big nozzles work