MK5 Drive Gear – Now with Science!
The design is pretty simple: there is a chunk of Stainless Steel 304 with a knurled groove that has the same diameter as the old drive pulley. Therefore, this part is a drop-in replacement for the old pulley. Since it is stainless steel it is very difficult to damage the pulley, even if you tighten it down too far. Furthermore, since the knurling on the pulley is so fine, it has a limited ability to self-clean as any stripped filament will typically fall out of it. If you’re feeling hardcore, you can download it from Thingiverse and make it yourself.
As sexy as this new pulley is, we wanted to be able to prove that it was indeed better than the old system. So, we turned to our trusty friend, Science! We formed a hypothesis (that the MK5 drive gear is better than the MK3 Drive Pulley). We created a test rig and we ran a bunch of tests. We tested the MK4 with both the new and old drive pulleys at a variety of spacings. As we had hoped, the new MK5 drive pulley came out on top.

For the force measurements, we used a very nice yet affordable Dillon GL-500 Force Gauge . This gauge has a few really nice features: a 500N capacity (~50kg) with an accuracy of 0.2N (~20g). Besides being nice and accurate, it can also measure both pull and push forces. It can record peak force, and even has RS-232 output which we could use to record measurements digitally. It is also a really solid, well built device.
The test rig was lasercut from some plywood and bolted to a chunky 2×6. If you want to replicate our results at home, you can download our template and lasercut it. The test process was pretty straightforward. We typically repeat this process 10x per setup to get a decent sample size. The design is pretty simple: there is a chunk of Stainless Steel 304 with a knurled groove that has the same diameter as the old drive pulley. Therefore, this part is a drop-in replacement for the old pulley. Since it is stainless steel it is very difficult to damage the pulley, even if you tighten it down too far. Furthermore, since the knurling on the pulley is so fine, it has a limited ability to self-clean as any stripped filament will typically fall out of it.
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