New Motion Control

More Laser 11 Aug 2018

The Smoothie is dead, long live the… whatever comes next. Some crappy wire fried my control board so now I’ve got to get a new solution.

I went over the primary disadvantage of the Smoothie in the last post, which is that it can’t support two motors driving the same axis. This isn’t generally a problem for most people, but it is for the design that I came up with. I searched around a lot to try and find a better solution. Some of the things I looked at were:

• Klipper is what I use on my 3d printer but no laser support currently
• TinyG seems really nice but no support for double motor gantry
• GRBL looks more complicated to setup (looking to flash to Smoothie) and no double motor support
• LinuxCNC looks difficult to set up, but supports dual motor gantry. Requires an old PC with parallel port theoretically
• MachineKit is a branch of LinuxCNC, seems to be mostly run on BeagleBone Blacks with a “cape” that adds supporting circuitry for interfacing with the machine. Similar configuration to LinuxCNC

I ended up selecting MachineKit on a BBB with a Xylotex 6 Pack as the supporting cape. I chose this as its the only option that supports dual motors on a gantry, and it also doesn’t require an old parallel port PC or expensive hardware like LinuxCNC seems to require. I chose the Xylotex out of several options. Most of the other capes seem to be aimed at a more powerful system where you’d have stand alone stepper drivers and just need to wire them to the control board. They mostly just provide isolated/protected outputs from the BBB. The Xylotex board is similar to RAMPS, in that it provides up to 6 stepper drivers using the ubiquitous RepRap style stepper driver pinout, in addition to a handful of isolated inputs and outputs, and some extra connectors for an E-Stop and power switch. I’ve still got to figure out how to wire this all up to the relays and stuff I have, but it seems like it should be able to do everything I want. So far MachineKit seems complex to setup, but I think this is mostly due to lackluster documentation. There seems to be a good amount of documentation, but it isn’t set up in a way that’s intuitive to follow. Luckily, I think this has much more configuration options when compared to most 3D printer controllers as far as input and output control, and user configurable logic. It will just take a while to get there. I’ll try my best to write up a little how to when I’m done to try and make it easier for others in the future.

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