Gauge that gives a visual indication of tension on the E3D Hemera extruder. The needle moves up the gauge when the knurled screw is adjusted.

As with all 3D printed things that are designed to fit other things, dimensions may vary between printers, this is designed to be a tight fit, have your files at the ready.

The fall back of the needle is entirely gravity driven so might not be appropriate for bowden setups where the extruder isn't mounted upright. (I am in the process of working out how to include a small return spring)

STEP file included for your tweaking pleasure.

If you make one, please share.

Print

It's a tricky little print, I used a 0.4mm nozzle but a smaller nozzle might be beneficial particularly for the needle. Bed adhesion needs to be good with bed supports enabled for the body.

The pictures show the body printed with a 0.1mm layer height with PETG. It made little difference to printing in 0.2 layers so that will be fine. Also shouldn't be a problem with PLA, I just happened to have PETG on the printer. 4 outer layers.

The underside of the gauge face didn't come out particularly well but as a functional print it's of no consequence. Probably better with PLA.

The designs can be mirrored if your extruder is facing the other way.

Assembly

Required:
M2 x 10 Socket cap screw

The fit of the needle on the screw should be checked first. It should be loose and free to turn. If not, running through the hole in the needle with a 2mm drill bit should do the job. Do not drill through the body.

Check the fit of the body in the back of the extrusion arm, the lugs should be a tight push fit. It's deliberately designed to be tight and may need filing in places. if it's loose a small dab of glue might be in order. Don't want it falling off mid print.

For the gauge face add a sticky back postage label or piece of paper stuck with glue stick and trim to fit.

The machine screw is screwed directly into the body with the 'tail' of the needle nearest the extruder.

Holding the assembly with the needle in its lowest position (as in the pics) the assembly can be pushed into the back of the tension arm. the tail of the needle should just about touch or be very close to the white sliding block in the tension arm.

The paper gauge face can be marked up with min/max and however many divisions you like.

Some notes on the design

The needle is delicate, that can't be avoided.

The gauge is at a weird angle and doesn't lend itself well to a clean print. This is a compromise between leaving thumb space for the adjustment screw and space on the outside of the body so that the arm can be retracted without crashing into parts that might be mounted on the side.

The gauge doesn't have printed increments because they would be too fine to be useful and a piece of paper allows for some deviation and personal preference.