This is a version of the ReprapMJ (3990953) two hardware extruder with the addition of 4 screw holes so it can be fitted to most standard brackets and nema17 motors.

It is very minimalist and very easy to print and assemble. It is even easier to use and work with.

It works on the basis that there is no tension when not in use (if you remember to turn the lever off). Filament can be fed or unfed without fiddling around with springs etc etc.
It can be left “on” but if made with PLA it will gradually loose tension. I have left mine under tension many times (I am getting old!!) and I still have enough adjustment on the cam to apply more tension.

And yes, I have forgotten to apply tension when trying to start a print (quite a lot if I am honest). I always catch it in time because I routinely use three loops of skirt to check the nozzle is clean and I watch the layer thickness to make sure the Z is correct all around my object.

There are a couple of short clips below of a ReprapMJ using the screwless version while making this new 4 screw type and also being used with nylon.

If you check out the full ReprapMJ you will see there is a fully printed version which I may also add as a screw on type if there is a demand (let me know in comments). The fully printed version works with PLA only and I would not recommend it for long and costly prints but it is great fun and very satisfying to watch it working (I spend waaay to much time watching 3D printers!!). It was made as a design exercise and for the principle of being fully printed but it works surprisingly well.

Advisory Note – The down side to this extruder is that you need a working printer to print one. I suggest do not wait until your old one breaks before you decide that you need to make one!!!

Personal Note – If you like this thing please may I ask you to kindly take the time to click the like button. I have uploaded a small collection of things which in my opinion range from useful to frankly stunning (OK I admit I am biased) but I have a very sad and minimalistic collection of likes so far. You folks are VERY hard to impress and I am feeling very unloved right now!!!