Weekly summary ending 2018-02-01

Hey, friends! Here is what we worked on in the last week, where we are heading next, and how you can join us.

Last week I mentioned that I’m trying to sell a vending machine to make room for a CNC metal cutting machine. The CNC quote came back at >$40k CAD.

As you probably know by now, we’ve been working on a robot arm. Last week we ended off with a new cycloidal gearbox. Well this week we printed two more and installed them.

We’ve had many challenges dealing with friction in our power transmission. Bevel gears have been a real problem – There’s no perfect solution to make bevel gears and some of the tutorials we found online were flat out wrong… which we figured out only after following the tutorials.

There are, in fact, three popular ways to make bevel gears.

Once we had a better understanding of how to make bevel gears correctly, it only took three tries to get the gears perfectly tuned on our printers. With that out of the way we can finally show our three motors working together to move the first three joints of the robot arm.

Fun fact! The joints and motors work as a differential: one motor is needed to move the hand, but it takes two working together to turn the wrist, and three working together to turn the ulna.


I am currently deep into the Makelangelo firmware, trying to solve a mystery that should improve speed across all our robots.

Jin is working on the math for our motors. There is an ideal speed (in RPM) to get best torque, and from that ideal we can calculate what Sixi’s actual speed will be. We didn’t know earlier because the priority was strength and accuracy. Fast, Strong, Precise: pick two!

How you can join us

Get the latest Sixi Master Assembly for Fusion360 on Patreon
Buy anything in our store and mention ‘The Fusion link’ in the notes field to get a link by email.

You can use this file to build your own copy of the robot arm.  Put that 3D printer you bought to use – Make it your own! Share your creation with others!  That’s what open source is about.  If you build one we would love to share it with others.  I am actively seeking talent… show me what you got.

As always, follow our daily progress on our Instagram or see our older stuff on Youtube.

Lastly, thank you for your likes, subscribes, comments, and purchases. You keep the lights on and the mood high so we can keep working on awesome things for you.