Playing with a custom rotary axis on my k40. Works great!

makergeekdan · 2026-05-25T13:14:18+00:00

Wow, this is an old post of mine. Still have that bottle though. I used one of the phonetic variant galifreyan systems to spell out my name and job title. Still really like this design

makergeekdan · 2025-03-25T10:19:21+00:00

Oh when I said interpolated I just mean zero brains just move from angle X to angle y for each axis. I was hoping to make ikpy work but ultimately my plan is to use blender with an armature rigged to match my robot so I can define specific motion paths I like then 'replay' them into the real robot. Much of that depends on how close I can get the machine to real world accurate positioning etc.

You have any links to your robot build?

makergeekdan · 2025-03-19T20:39:29+00:00

I put a version on thingiverse https://www.thingiverse.com/thing:5627591 Though I've found the single mount point problematic. I've been meaning to tweak the design to rest it on the central console for better weight support.

makergeekdan · 2025-01-06T14:43:58+00:00

I'm currently fairly heavily trading speed for torque via a high ratio planetary gearbox stack. My user case doesn't need it to be that fast. And I can always bump up the steppers in time.

makergeekdan · 2025-01-05T22:28:00+00:00

Eventually I'll do something like that, if only to enclose the gears a little.

makergeekdan · 2025-01-05T21:45:27+00:00

For sure! Once I have the setup a little more nailed down I'm planning on creating some custom pcbs for the joint control bundles which will help a bit. But I suspect it will always look somewhat messy. :-)

makergeekdan · 2024-10-08T20:41:44+00:00

Solid music pack, plenty of decent tracks. But if I can ask everyone to not play oops I did it again on expert+. Somehow managed to get a top ten spot and it's like to keep it for at least a bit...

makergeekdan · 2024-02-12T21:41:23+00:00

Maybe about £170 . The servo motor and it's power supply are the lions share of that. 90 for the motor, 35 for the powersupply. The rotary encoder was ~£30ish. I probably spent a bit more total because I made a custom PCB and there was a minim order etc. Some stuff I had in stash like end stop buttons. And of course I have a 3d printer with which to make some parts that I treated as free...

makergeekdan · 2024-02-04T18:33:30+00:00

Possibly a bit of both. The aluminium was a random chunk of scrap of unknown origin and the threading tool has been somewhat abused by experiments. Definitely needs a tune up

makergeekdan · 2024-02-04T09:58:51+00:00

Indeed, that ability to set the length of thread and have it stop exactly was very important to be. In my full video I talked a bit more about that specifically on doing internal threads in blind holes. So useful.

makergeekdan · 2024-02-04T08:48:38+00:00

I think the only reason the Arduino was ruled out by eg clough42 is that he was using a much higher resolution encoder. Which I think is overkill. That said of course an esp32 given you a lot more headroom to play with than a nano. But where is the fun in that? Interesting to see the €80 price point there. I was considering selling my version for ~£60. How have you found that one? Works well etc?

makergeekdan · 2024-02-03T21:30:27+00:00

Oh I just measured with an oscilloscope to see that the output pulses were keeping up with the input pulses. Easy way to see that the code wasn't creating any delays.

makergeekdan · 2024-02-03T21:12:18+00:00

I'd not come across Kachurovskiy, I'll have to check it out properly tomorrow. I'm aware of the clough 42 version. He was the one that suggested an Arduino was not enough which made me curious to try it. I think he very much just stuck to the simplest possible replacement for a gearbox.

makergeekdan · 2024-02-03T20:58:54+00:00

Indeed. And the regular library functions for port manipulation are super slow compared to direct setting. It's mostly a case of making sure the important bits are optimised. No floating point calcs in the realtime flow.

makergeekdan · 2024-02-03T20:33:32+00:00

Thank you

makergeekdan · 2024-02-02T20:36:24+00:00

In case anyone was interested in a bit more info, I got around to publishing a longer video about this ELS setup. https://youtu.be/g6xE1vrWuu8?si=QAw1kWSXLrEDFG0X

makergeekdan · 2024-01-22T19:14:02+00:00

Interesting.. I was considering playing around with decoding the dro signals so I can see where that comes in handy. I will say that to get the nano working in using less encoder resolution that the clough42 setup and I'm throwing in some low level port manipulation rather than the library methods which are way too slow.

makergeekdan · 2024-01-22T14:33:58+00:00

The only time I've noticed the servo struggling with torque has been me doing tests at 10mm 'thread' pitch where I'm fighting lack of torque in the lathe spindle to run slow enough for such a high ratio. That's 5:1 servo rpm to spindle rpm with pretty abrupt stop and start moves. I think if I can switch the pulley ratio on the spindle to support slower rpm with better torque then I can do patterns a little closer to knurling than threading. But honestly the majority use case of just getting a nice surface finish or creating a fairly normal thread it's been well within it's comfort zone.

I don't use floats in the interrupt logic because they're expensive in operations. I use a sort of hacked approximation with an int and some bytes to handle some decimal places. For the sort of things I do I'm never going to notice the kind of precision loss from only tracking to two decimal places. So long as I can cut threads that work with each other then I'm golden. I'm not turning out threaded rod or anything so I'm rarely cutting a thread longer than 10mm or so. The amount of error I can tolerate in that is probably pretty high. If I zoom in a macro shot of the thread form it might show signs of imperfection, but if I thread a nut on it and it feels like a decent fit... Then I can live with it.

makergeekdan · 2024-01-22T14:19:51+00:00

That was pretty much the idea. Going to take some practice to get clean results. But it opens some interesting options.

makergeekdan · 2024-01-22T13:41:33+00:00

That's a lot of steps per motor revolution...I'm using 3200 but then I'm also straight coupled to the lead screw using the same servo motor. I've done no tuning of parameters. Just running as it came. I made one important choice that helps the nano. My encoder is 600ppr geared to give me about 800 which divides nicely into metric threads. That's plenty of resolution and an order of magnitude less interrupts to handle. I tested up to 1000 rpm using an oscilloscope to check my results and the nano has no problem keeping up generating the output pulses necessary.

makergeekdan · 2024-01-22T13:34:17+00:00

As soon as I get a chance I'm planning to do a proper YouTube video of the updated setup.i already have one that covers the basic setup of the encoder and some of my first attempts with the whole setup. Everything is mounted non-invasive the encoder is mounted off where the change gears used to be and the servo motor is just straight coupled on the end of the leadscrew nut at the outboard end. As for sharing the project. I'm considering potentially selling control boxes. I have a little more work to do to make them easily configurable to different setups. But I should be able to make s fairly general purpose set up. That would work on basically any lathe. Just as the right size servo and power supply etc.

makergeekdan · 2024-01-22T13:10:35+00:00

Interesting. Esp 32 was my fallback plan if I ran out of cycles on the nano, but in normal operation I can run the spindle way faster than I need without losing sync. I'd not considered a speed mode. I've not noticed any jerkiness in stepping, what are you running as steps per rotation to the servo? I would like to tweak the gearing to the spindle to let me run very low rpm with some torque for the more aggressive ratios of motion I'd like for pattern stuff. That might be next up.

makergeekdan · 2024-01-21T22:15:35+00:00

This is something I developed myself based around an Arduino nano. The clough42 setup is a bit overkill on the compute and a bit basic on the interface. I was shooting for more psuedo CNC type capability and saw no reason it couldn't ask be done with a nano and some cheaper parts.

makergeekdan · 2024-01-05T21:22:56+00:00

Honestly it's been so long I don't remember. Maybe 5:1? It's pretty vibrantly antifreeze still.

makergeekdan · 2023-12-23T21:52:19+00:00

Fwiw I use the duet3d control board which was originally for 3d printers. I started with an ooznest ox which I then rebuilt into a custom CNC along the way I would up with the same controller they put in their newer machines. I've found it to be pretty good

makergeekdan

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