Geneva Drive Extruder Visualizer

Introduction:

This is a bit of a work in progress and is the first version of my Geneva Drive Extruder Visualizer. I will be using this on my printer and monitoring it to see how it performs over time. If there are any changes to be made, I will update this page and parts as I go so keep an eye out.

If you have any trouble with the parts or have any suggestions for changed, please leave a comment and I will do my best to accommodate.

Update 01-04-23

I have been running this for a few hours now and the issue with the geneva drive stopping and starting seems to have gone away completely. I have used a very small amount of grease on the pin of the drive wheel where it interacts with the driven wheel. No oil or grease was used on the washers on my version but I think a tiny (pin head tiny) drop of medium viscosity oil on the washers might even make things smoother. I found the key was to make sure there is a tiny space between the washers and the drive / driven wheel. As long as they run freely, it should be good.

Bill of Materials:

* 3D printed version included and in use on my own prototype

3D Printed Parts:

Main Frame
Driven Wheel Frame
Intermediate Gear
Drive Wheel
Main Drive Gear
Driven Wheel
Pointer (Optional)
Connector (Optional)

Printing:

All of the parts are designed to print without supports. Use common sense to orient the parts on the build plate so that there are no overhanging parts. I printed everything with a .2mm layer height on a .4mm nozzle. The parts should be printed slowly to ensure a good finish. Colours and materials are up to you but I am jusing PLA. The black and copper colours I used are by Giantarm and the dark green parts are Prusament Gentlemens Grey.

Construction:

Step 1:

Using superglue, attach the driven wheel frame to the main frame.

Step 2:

Align the drive wheel with the intermediate gear and glue them together using superglue. Take care to make sure the gear is glued centrally to the drive wheel. The central holes are a little undersized so that they can be drilled out to 3mm exactly. This will ensure a good slip fit for the m3 bolt. Once glued, then drill the holes out to make sure they are concentric.

Adding a washer either side will allow free movement of the wheel which needs to spin freely. You can use real washers, or the 3D printed ones included. If you are using the 3D printed washers, you may want to rub them on some sandpaper to ensure a smooth top and bottom surface. A very small amount of grease can also be used but use as little as possible.

Step 3:

This is similar to step 2 as the central hole of the driven wheel needs to be drilled out to 3mm to allow a slip fit on the M3 bolt holding it in place. Again either real washers or 3D printed washers can be used, follow the same procedure as step 2 for the washers. The optional pointer can also be glued in place to add a different colour accent to the driven wheel.

Step 4:

This can be tricky, and it may be easier to start with one wheel assembly at a time loosely bolted in to start with, so you can align the second wheel assembly. The main frame and the driven wheel frame have undersized holes in them that will allow the M3 bolts to cut a thread. These bolts need to be snug but ensure that both wheels can move very freely without too much play.

The connector is optional but will cover the washers and can be used to add an accent colour to the build.

The parts have been designed with .4mm of tolerance so if the wheels are binding up, you will need to check your printer settings and make sure you are not over extruding. Also check for elephants’ foot as this can cause binding.

Step 5:

Using super glue, add the magnet to the bottom of the main drive gear. There is a small recess in the bottom of the gear to help with alignment. You will want to make sure this is as perfectly central as you can get it. Once glued in place, allow it to dry before placing it on the bottom of your extruder. The main assembly can then be push-fit into place over the extruder. It may be necessary to rotate the drive wheel as you push the assembly into place so that it meshes with the main drive gear. Once in place, check that there are no wires catching in the gears and give it a test.

Final Note:

I did find that on occasion, the mechanism would stop, in particular with slow moves where the drive wheel meshes with the driven wheel. This seems to go away after a retraction most of the time, I expect it will become better with use but keep an eye out for an updated version in the future in case I find a solution to this. Again if you have any issues or suggestions, leave a comment and I will do my best to help.