4th axis as a "poor man's lathe"

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It's been a while since I posted any updates regarding this project, I was simply busy with some other activities, some hobby related some not, so I had no time to post anything.

But now it's time again for another video. The major difference is that after my tests and the last video, I decided to digitalize my DIY micro lathe since it works very well, not only for aluminium and brass, but also for steel. So I bought two steppers, made some tests, but then got busy with photography, buying new cars (EVs of course) and other activity, so the project got to a halt. However, a few weeks ago I thought that it's a shame not to carry on and finish it, so I fixed the two steppers more permanently and made some test cuts with the new CNC lathe, turning aluminium, threading, rounding and chamfering and my tests were so successful that I decided to make a video.



The video not only shows the CNC lathe in action, but it is actually used for making a real thing, a micro chuck adapter, so that I can use that micro chuck for drilling with tiny drill bits when I am too lazy to use the ER16 collets. The results were surprisingly good and in fact, I was so happy with it that I decided to carry on, and ordered a new Multifix type tool holder, which I believe will improve it a lot. It is a real one, made out of steel, not like the one I am using now, which is aluminium. The one I have now works also, but is not that rigid, so there is a bit of chatter and vibration. But that is OK, considering the price. I bought it knowing it's limitations, but also was ready to buy something better in case I am otherwise happy with my DIY CNC lathe. So that will be my next upgrade, apart from small bits and pieces which I intend to do.

One such thing will be adding emergency stops. As it is now, if the servo would stall the steppers will continue pushing the cutter, which no doubt will cause damage. So that must be fixed as soon as possible, because it is not a good thing. If it happens I want the machine to stop immediately on it's own.

I am controlling the lathe with UCCNC, which does not have a lathe function, but for my intended use it works pretty well for now. The G code is manually generated by myself, and for now I am happy to do it manually. It gives me some experience in handling the lathe since I am totally new to this type of work, so the slow progress is an advantage and is giving me a learning experience.

Anyway, if you are interested, please watch this video.

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My Multifix type tool post arrived and I used it also. It is way better than the aluminium quick change tool post I used before even if it is just fixed with a simple M10 bolt. However, the first use I made for it was to create a tool post holder screw. I measured all the dimensions, found a piece of steel rod in a hardware shop near me which I could use and made the tool post holder. It took some time and not without mistakes, but finally it is ready. It is not perfect, but will be much better than the threaded rod I used originally. I will probably make a new one without the mistakes, now that I learned something while making this one.

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I made a video regarding this upgrade and the making of the tool post holder screw and nut.

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I decided to make an upgrade (actually more than one...) of my CNA lathe.

Number one update is to change the spindle motor.



While the 180W 50V DC servo works surprisingly well, I want some more torque and higher RPM, so I bought a 600W AC servo. This motor will allow me to change the gearing from 1:3 to 1:1.5 so I will get a maximum chuck RPM of 2000 instead of 1000. I think the motor will be strong enough for me at that speed.



I made some modifications to the servo driver, added three LEDs and a small relay to the four outputs, and also a button to one input. Inside the driver there is more than enough space for the small PCB necessary for this modification. The parameters are set according to the following for this modification:

LED 1: Servo ready
LED 2: Servo motor power on
LED 3: Zero speed
Relay: Alarm detection
Button: Alarm reset

The relay NO output is connected to a 3.5mm contact, which in turn is connected to my eStop so that when everything is fine (no alarm) the relay is energized and the contact is shorted.When there is an alarm from the servo driver the relay will break the circuit and UCCNC will stop the G-code execution and all motors and halt. When the error condition is back to normal, by pushing the button the error flag is reset and the servo driver is ready again and UCCNC can start again. Of course, this condition is emergency stop, so the code can't continue from the same spot where it stopped.

This is all in theory and after bench tests. I can't run real tests yet, since I must make a new motor holder plate, and I won't have time to finish that work the coming weeks, since tonight I will be off to Hungary and Austria for two weeks.