Looking at Dave’s extruder, I noticed that the motor, belt & wheel setup he has are very similar to a set that I have here, salvaged from an old washing machine, except that what I have been wanting to do with this motor was to build a lathe, like this one.
So it just occurred to me, that with making this machine modular as one of the aims, we could possibly design one to be mounted in a lathe, so that when not extruding plastic, that bench and motor can have other uses (killing two birds with one stone, while saving workshop space and materials 🙂

This may mean that the machine requires a stand to be clamped to the table, rather than bolted down, possibly with adjustable legs, unless the barrel can be positioned in a lathe tool-holder.