Compass now has 3 axes <3and it’s pretty sweet |
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I’m really excited to finally share what I’ve been working on for the past couple weeks: I’ve given the Compass handheld CNC router another axis! Let’s jump into what has changed and why this is so cool… |
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The main advantage of adding another axis is that it dramatically improves the device’s path tracking abilities. It can now correct forwards and backwards as well as just left to right, making more complex designs a lottt easier for the user. Because the last version was only 2 axes, the user was solely responsible for the 3rd axis of motion. Rotating or repositioning the device was necessary, and frankly unintuitive as many beta testers pointed out. This is now solved. The operation is now an enjoyable dance where Compass leads, and you follow. |
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All you gotta do is keep the little circle inside the box |
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I’ve been thinking about implementing a 3 axis motion system for quite some time now, but have only just recently settled on a satisfying way to do it effectively. I wanted it to be as simple as possible, rigid, and compact. Simply shrinking down a standard CNC gantry would be unnecessarily clunky. Our little handheld CNC router doesn’t need nearly as big a range as a standard CNC machine, so we are able to get away with some sneaky redesigns. |
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What I ended up going with for the XY motion assembly was a coreXY system built upon stacked plates and linear rails. These stacked plates are meant to keep everything as low down to the work surface as possible to minimize torques on the tool and keep the system rigid. This approach also allows us to bring the plates extremely close together in order to keep the dust collection channel as airtight as possible. The efficacy of the dust collection is pretty important for Compass’ operation so we gotta be locked in with this. |
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Once I had the design settled, I went to work on the proof of concept. The mechanism was pretty easy to whip up once I had an idea of how I wanted it to work. It was a bit of a learning curve designing around belts and pulleys, but not too bad. The software was a quite a bit more difficult. I started out with a little “chicken head” mode, just keeping the tool at (0,0) while I moved it around. |
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I racked my brain for a solid week or two on how to extend this to any arbitrary path. With the 2 axis router, the user would lead the motion, and the device would respond to move the tool to the correct position. This was pretty straightforward because there was only ever one solution for the “correct position”. With 3 axes, though, there are effectively infinite solutions. That makes it a bit harder to choose just one. I thought about this for a while, thinking through complex control schemes that would bias towards keeping the tool in the center of the working range. Then I realized I could simplify things quite a bit by just flipping the approach - the robot leads the motion while the user responds. This makes everything a lottt easier. Once you hit “go”, Compass is pretty much acting like a standard CNC machine - until you move it. The user’s only job is to make sure the design stays within the router’s working range. |
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One of my favorite parts of this design is actually the belt tensioning mechanism. Because the motion assembly is so compact, it is pretty tricky to get the belts where they need to be. I went down a fun little rabbit hole to fix this and make belt routing a straightforward process. |
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There are two M5 bolts on the top plate that are connected to drive pulleys which grab onto the belt when inserted from the side. This allows you to easily feed the belts through and tighten them with an allen wrench. Once the desired tension is reached, just insert the 3D printed plugs to keep the belts locked in. |
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As far as the new prototype goes, that’s pretty much the gist. Hop into the forums and let me know what you think. What should I add? What am I doing wrong? Always love to hear the feedback! |
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I only had time for one cut test before leaving to CO for RMRRF and tldr it wasn’t amazing. After further investigation, I found that my new router’s fancy ER11 collet was seating terribly, causing for a bunch of run out. The collet nut is totally warped. Hopefully that’s the main culprit. Only more tests will tell! Will hop in the shop asap and post updates on the socials, so stay tuned… |
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Rocky Mountain RepRap Festival |
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Speaking of RMRRF, this past weekend was awesome. The amount of smart, passionate people at events like these is really just so intoxicating to be around. I’ve come away with a solid list of things I want to explore and quite a bit of excitement to do so. It was also such a great time sharing tables with the V1 Engineering crew and seeing all the cool stuff that they brought! Excellent vibe the entire event. |
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My goal was to have this 3 axis prototype ready to show off at RMRRF, and low and behold I was able to squeak everything together just in time. I had little drawing demos going for people to come and try out the new device. It was awesome to see the process of young kids coming up to the table super confused, attempting to figure out the controls (some getting it quicker than others…), and then teaching other interested kids how to use it. Some just liked to whip it it around like a racecar or fighter jet. This subset of users are always the best torture testers. |
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After a handful of people mentioned how much the demo felt like a video game, I decided to throw together a little “speed run” mode for people to see how fast they could draw the RMRRF logo. It was such a blast seeing people come up and try to beat new the new records. |
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Other than just Compass stuff, there were countless cool projects around the venue. The Ston printer was a mind blowing standout, shining of thick polished aluminum and printing at 750mm/s with pristine quality. It’s a pretty crazy feat of design and engineering, made even more compelling after chatting with its creator, Nathan (who definitely gives subtle mad genius vibes - of the 3D printing variety). Another favorite was a custom iPhone-based camera rig featuring a retro-reflective green screen and real-time tracking. It looked like glowing sci-fi tech from across the room and delivered some pretty impressive effects. |
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Stay tuned for more! Really excited to start pushing Compass’ new 3 axes to the limit. |
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Remember to keep it fun :P |
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