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

I bought a rotational axis ( 4th axis or A axis call it whatever you like) for my CNC with a 4 jaws chuck. I intend to use this as both a 4th axis on my CNC, or as an independent "poor man's lathe". I know, it will be a very primitive lathe with a lot of limitations, but I intend to try it out anyway to toy with and to learn. Maybe later on I'll buy a real lathe as well, but for now this will do. I am sure I can use it for some sort of work, but I will see that later.

To get the lathe function I had to design a control box. This is based on an Arduino Uno module with a 2x16 lines LCD. It is a very simple design, using only three buttons, one for clockwise rotation start, one for counter clockwise rotation start and of course, one for stop. Stepper acceleration and deceleration is also implemented, with a possibility to select acceleration in 7 steps. The chuck rotation can be adjusted between zero and 380 RPM, which is the maximum. This corresponds to 2280 RPM on the stepper, due to the 1/6 reduction pulley the stepper drives the chuck with. So it is a respectable rotation speed for being a stepper. The rotation speed is set using a rotary encoder and that speed is saved in the EEPROM, so after a power off, the last used rotation speed is restored. The rotary encoder push button is connected to the Arduino reset and acts as an emergency stop, in case there is a need for stopping as fast as possible. Of course, this means no deceleration, just an abrupt instant stop.

For powering and control I also built a separate PSU, which provides 48V 7A DC through four individual 12V power supplies connected in series. Three of these are 9A supplies, the fourth is though only 7A, which is why the maximum is limited to 7A, but considering that the stepper is only 3A, I figure that the PSU will be good enough for the purpose.

The PSU box also contains a DM542 stepper driver, which is configured to the maximum current and 2x micro stepping, which results in 400 steps per rev.

There is also a relay inside the box. This relay decides if the 4th axis is to be driven as A axis by my CNC using UCCNC software, or independently run as a "lathe", controlled from my control box and rotated non-stop until i press the stop button. The relay can be switched from the control box and the default setting (with the relay off) is that the rotational axis is controlled by UCCNC.

Yesterday I made a short video about testing the control box functions and showing the rotations. I have not used it yet as a lathe, still waiting for some necessary tools before I can do any real tests, but I thought this can be interesting to show as well. Maybe it will give other people some ideas as well.

I intend to share the Arduino code here as well. It is well commented, so based on the code, the simple box can easily be built by anyone understanding the basics of Arduino. I will need to add some file header information before I post it here, but it will be posted soon.

I hope you will enjoy watching this video. I will make a new one once I start using it as well.

https://youtu.be/qfiPTDvZlIs

Edit:

If anyone is interested to use the Arduino code, here is a link which you can use to download it:

https://drive.google.com/file/d/1CJN...ew?usp=sharing

Nice project. I'm looking forward to seeing what you make with it.

Kit

Brilliant work there!

Thank you to you both. If it works for something (I expect it will work for plastics and soft metal) I will toy with it and see if I like it enough to upgrade the motor, or to buy a real lathe. My problem is space. I already have too many machines and right now I don't have any space for a real lathe. Anyway, it will be fun to build something similar to a lathe, which I can use for simple things and for learning. ...and if it turns out to be useless... then so be it. We only live once, and the road ahead is more fun than the goal. Failing is part of the fun, but of course, success is even more fun.

I find speeds of 1000rpm and over to be ideal for small parts, Aluminium and plastics on the lathe.

Yes, I know it would be optimal and much better, but that would require 6000 RPM for the stepper...

My experimental project continues. I couldn't wait, I just HAD to do some tests, which I documented yesterday in a short video.

https://youtu.be/g8rXwJtne38

While one could wish for higher possible speeds, I think considering it is driven by a stepper motor, the results are very good so far, so I will definitely continue. I am still waiting for cutters to be delivered, but for drilling it seems to work. I am now pretty sure that it will work also for turning, but of course, that still remains to be seen. Anyway, I'll be happy I made this, also because I often end up wanting to drill centre hole into something, and that's not that easy without a lathe, so if for nothing else, I will definitely be able to use it for that.

Anyway, while I will finish this with the stepper I have on the chuck now, I am already planning for an upgrade with a more powerful servo or a closed loop stepper. I have already started to look for solutions even for that step. Unfortunately it is not just about changing the motor, because it means I have to change the plate it is fixed to as well, and also get a new timing belt as well as maybe a new pulley. So it may take some time before that step is done.

Right now I am considering this motor:

https://www.aliexpress.com/item/3285...4b6e2e0eyN2Gxo

I have no experience with any closed loop stepper, so I would like to ask the experts. Do you think it is worth the money? My steppers are 1.8Nm type, and this is 3Nm. Would that 1.2Nm make a big difference? Would it run faster? Remember that my current stepper is running at 2280rpm in the video, which due to the 1:6 reduction means 380 chuck rpm, so anything below that is not good. Currently I run the stepper at 2 microsteps, so 400 steps is one rev. and I intend to continue with that. The test condition in that link says 1600 microsteps but I think they mean 8 microsteps per step, which will give 1600 steps per rev. The motor is weaker at that high microstep, and is easier to get higher RPM at lower microsteps.

The fun continues. I continued with my "poor man's lathe" project, which has become quite an expensive activity. I made the first major upgrade, changed the stepper to a 180W servo, which required changes in gearing, the pulleys are now 60-20 teeth, so the ratio is 3:1. I also replaced the aluminium extrusion with heavy duty type, added 1605 ball screws and 20mm linear rails on all axes. Of course, the control box also needed to be updated since I can now get 1000 rpm chuck speed.

The change in gearing forced me to replace the belt to a longer one, and I also had to make a new fixture for the motor. I wish I could replace the old fixture with a new one, but I could not find any way of removing the old one, so I added a sort of piggy back plate. Anyone ever removed the motor holder plate, please tell me how to do it without destroying the whole thing. I can not for my life figure it out, and removing the chuck and the large pulley is not enough. Looks like the spindle needs to be dismantled, and I don't want to do it without knowing how.

One thing I am disappointed is the noise. I find the servo is quite noisy. I don't know why, but it is not what I expected. Also, the holding torque seems to be a joke compared with the stepper I had, so maybe this servo is far too weak as a rotational axis, where high holding torque is necessary. Anyway, I will finish the project first, before I buy a more expensive and larger servo.

https://youtu.be/ILFjNXn3Z0k

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Originally Posted by A_Camera

One thing I am disappointed is the noise. I find the servo is quite noisy. I don't know why, but it is not what I expected. Also, the holding torque seems to be a joke compared with the stepper I had, so maybe this servo is far too weak as a rotational axis, where high holding torque is necessary. Anyway, I will finish the project first, before I buy a more expensive and larger servo.

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That doesn't sound right to me, that doesn't sound like a true servo but more like a very resonant stepper motor.
Both DC or AC brushless Servo's are very quiet even at 3000rpm. This video I did about electronic gearing shows just how quiet, jump to the 4min and 16min marks and you will see the motor spinning and hear just how quiet. The motor is a 600W AC brushless servo but DC brushless servos are just as quiet.

https://www.youtube.com/watch?v=bIdzlIKDJeM

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Originally Posted by JAZZCNC

That doesn't sound right to me, that doesn't sound like a true servo but more like a very resonant stepper motor.
Both DC or AC brushless Servo's are very quiet even at 3000rpm. This video I did about electronic gearing shows just how quiet, jump to the 4min and 16min marks and you will see the motor spinning and hear just how quiet. The motor is a 600W AC brushless servo but DC brushless servos are just as quiet.

https://www.youtube.com/watch?v=bIdzlIKDJeM

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Actually, the sound is normal. The noise comes from the timing belt, not the motor. It is not fair to compare your servo on a test bench with one attached to this spindle through a timing belt. Anyway, my servo is also quiet when there is nothing attached to it. I also made a test bench video, but hadn't had the time to edit and publish it yet.

BTW, what's an AC or DC servo? There is only one servo, but I think you call AC servo a servo which has a drive connected to AC current and DC servo one which has a driver connected to DC current. The only actual difference is that in one case you have the rectifier built into the driver and in the other case you have it built into the PSU. Mine is called AC servo with integrated driver, which requires 20-50VDC, but it is still an AC servo and not a stepper.

There's no black and white definition of AC and DC servo but generally a DC brushless servo uses trapezoidal ("6 step") drive current waveforms and an AC (brushless) servo uses a sinusoidal current. If you drive the motor and look at the phase voltages, so you find an AC servo produces a fairly sinusoidal voltage and a DC servo produces more of a wobbly trapezoidal (rectangular) voltage. A DC brushed motor has just 2 terminals and is driven by a DC current.

Must admit, that machine of yours sounds more like a closed loop stepper. There are 2 quick tests you can do to check. A stepper will feel lumpy when you turn it by hand with the motor disconnected, whereas a true servo will run freely. You could also remove the belt to show that the noise is indeed due to the belt. Having said that, the belt shouldn't be making a racket....

Quote:

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Originally Posted by Muzzer

There's no black and white definition of AC and DC servo but generally a DC brushless servo uses trapezoidal ("6 step") drive current waveforms and an AC (brushless) servo uses a sinusoidal current. If you drive the motor and look at the phase voltages, so you find an AC servo produces a fairly sinusoidal voltage and a DC servo produces more of a wobbly trapezoidal (rectangular) voltage. A DC brushed motor has just 2 terminals and is driven by a DC current.

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The manufacturer calls it AC servo with integrated driver and that's good enough for me. I think they know what they are talking about, even if they are Chinese. JMC is selling all kinds of motors, so they have no reason to give us fake information about this motor.

Quote:

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Originally Posted by Muzzer

Must admit, that machine of yours sounds more like a closed loop stepper. There are 2 quick tests you can do to check. A stepper will feel lumpy when you turn it by hand with the motor disconnected, whereas a true servo will run freely. You could also remove the belt to show that the noise is indeed due to the belt. Having said that, the belt shouldn't be making a racket....

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Yes, I know the differences between motors, I have many different types and am an engineer, even if I am not designing motor controllers. Of course, I did the obvious tests, the motor when rotated with hands and is switched off, rotates freely with very little resistance, unlike a stepper. It feels totally different and is definitely brushless. I have also opened the driver case, and the motor is definitely a 3 phase motor, since there are three wires going into the motor case and there are of course no brushes. I did not hook up any oscilloscope since I did not feel I had the need to do it. Never the less, I think how sinusoidal the signal would look like depends on the quality of the driver also.

Anyway, I have made a video even without any load, but have had no time to edit and publish it yet. Will do it as soon as I have time. Yes, the motor is quiet on the table without load, so I am perfectly comfortable with believing that it is a real AC servo, just like what JMC is saying. They do actually sell closed loop steppers of the same size and with similar looking integrated driver, but then they call it closed loop stepper, and not a 180W AC servo.

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BTW, what's an AC or DC servo? There is only one servo, but I think you call AC servo a servo which has a drive connected to AC current and DC servo one which has a driver connected to DC current. The only actual difference is that in one case you have the rectifier built into the driver and in the other case you have it built into the PSU. Mine is called AC servo with integrated driver, which requires 20-50VDC, but it is still an AC servo and not a stepper.

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DC servo is breushed DC motor with attached encoder for feedback.
AC servo is kind of 3 phase BLDC motor with encoder for feedback.

Drives for both types of servo motors could, by design, ve connected to AC or DC power source (at the end it is ALWAYS DC source).

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Originally Posted by A_Camera

Actually, the sound is normal. The noise comes from the timing belt, not the motor. It is not fair to compare your servo on a test bench with one attached to this spindle through a timing belt.

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Chill your beans man, I was working on what you said "One thing I am disappointed is the noise. I find the servo is quite noisy." So I took it that most of that noise was from the motor and I was just showing how quiet a servo is compared to a stepper in case you didn't know.

Also, if you are saying most of that noise is from the belts then you need to look at the setup/pulleys/belts because they shouldn't make that much noise. I connect most of my motors to ball-screws with timing belts so have fit 1000's of belts and they make a fraction of the noise you have there.

Quote:

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Originally Posted by A_Camera

BTW, what's an AC or DC servo? There is only one servo, but I think you call AC servo a servo which has a drive connected to AC current and DC servo one which has a driver connected to DC current. The only actual difference is that in one case you have the rectifier built into the driver and in the other case you have it built into the PSU. Mine is called AC servo with integrated driver, which requires 20-50VDC, but it is still an AC servo and not a stepper.

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It's not that simple and the drives work differently regards the motor types, but in both cases, they are virtually silent compared to a stepper which was my point.
I didn't think for a minute or was saying they were steppers but the noise in the video certainly sounds like a badly resonating stepper.

I would say that holding torque is better than what I'd expect to get from a 180W servo.
You could probably improve it through tuning, but 180W is never going to have lots of holding torque.

A quick search tells me a JMC 180W 3000RPM servo has 0.6Nm and 1.5Nm peak torque, so even through a 3:1 reduction, that's only 4.5Nm peak.
You can put that kind of torque through a decent screwdriver with a bit effort, so on a 4" chuck, it's not going to take much effort to move things.

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Originally Posted by ZASto

DC servo is breushed DC motor with attached encoder for feedback.
AC servo is kind of 3 phase BLDC motor with encoder for feedback.

Drives for both types of servo motors could, by design, ve connected to AC or DC power source (at the end it is ALWAYS DC source).

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That's the way I see it as well. But perhaps others see it differently, and that's OK as long as we understand what we mean. Mine is the brushless, 3-phase delta wired motor which I think all AC servos are. As for the drivers, yes, in the end, ALL driven by DC but installation wise it looks easier if you just have to plug one into the mains directly, compared to having to have a large power supply first. On the other hand, if a driver needs like 80VAC then it needs a large transformer and a box anyway, so while building a PSU out of that to provide DC output is a tiny bit more work, but that's really no big deal and in my opinion the benefits are basically gone. But sure, if directly mains driven then it is really nice and neat solution. Unfortunately, those motors are still pretty expensive.

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Originally Posted by JAZZCNC

Chill your beans man, I was working on what you said "One thing I am disappointed is the noise. I find the servo is quite noisy." So I took it that most of that noise was from the motor and I was just showing how quiet a servo is compared to a stepper in case you didn't know.

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Actually, I guess that my comment was a bit too emotional. Here is the sound of the stepper at 380 chuck rpm (2280 stepper rpm).

https://youtu.be/g8rXwJtne38?t=70

Somehow I expected (hoping for) some sort of miracle regarding noise, which didn't happen, but that's OK, I am fine with that for this experiment. In the end, if the whole lathe thing is going to work I may decide for a better solution and a more powerful motor. I think that a larger motor would also be more quiet, but that must wait for now.

Quote:

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Originally Posted by JAZZCNC

Also, if you are saying most of that noise is from the belts then you need to look at the setup/pulleys/belts because they shouldn't make that much noise. I connect most of my motors to ball-screws with timing belts so have fit 1000's of belts and they make a fraction of the noise you have there.

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I don't know the sort of installation you are doing, but I think that you don't build your motor holder the way I did here, which is the original 8 mm aluminium plate plus a 3 mm steel plate.

Attachment 30304

The reason for this solution is that I could not for my life come up with a way of removing the original motor holder plate, so I could not replace it with a new, single 10 or 12 mm thick plate, which I intended to do from the beginning, and also because I only had 3 mm steel plate at home, and I have lots of that, and don't want to get other. Of course, I could visit a local workshop and they would most probably free of charge make such a plate for me, or could give me a piece of scrap plate which is thicker, but for now I am happy to be able to do it this way. I also needed longer belt, the 350 mm is been changed to 420 mm long.

Attachment 30305

I also had to add some spacers otherwise the shaft would have ended up too far back. So I think the reason why you don't hear that noise is, apart from the fact that you probably don't run the motor for such long time, is that you also don't have such weird installation, which probably creates a lot of the noise also. With that in mind, plus the fact that my servo is also quiet on the table without load and with a dampening mat underneath, the comment I mage in the video is not fair, the motor is indeed quiet, but my own installation is generating a lot of noise.

So for the future, if I will otherwise be happy with this, then I will remove the original plate through cutting it off and replace it with a thicker aluminium plate in one piece. I think I can do that, but right now I don't want to destroy any part of the machine. Of course, if anyone have an idea about how to remove the original plate without cutting, I'd be glad try and do it that way, but I could not find any video or description in explaining how it was installed the first place or how it can be removed without removing the whole spindle assembly and risking the pre load of the bearings, or causing damage to the spindle or the spindle housing. All I know is that removing the chuck and the large pulley plus the four screws is not enough, the plate can still not be removed.

Quote:

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Originally Posted by JAZZCNC

It's not that simple and the drives work differently regards the motor types, but in both cases, they are virtually silent compared to a stepper which was my point.
I didn't think for a minute or was saying they were steppers but the noise in the video certainly sounds like a badly resonating stepper.

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I agree, it does sound like steppers, but again, that's only with the belt and everything attached. Regarding the driver, actually, my driver can start to buzz with some configuration. I did some experimenting and at one point it sounded like an old cheap Chinese built Toshiba 6560 chip based driver I had when I started my very first CNC build. That driver was also buzzing a lot when the motors were standing with the holding current applied.

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Originally Posted by m_c

I would say that holding torque is better than what I'd expect to get from a 180W servo.
You could probably improve it through tuning, but 180W is never going to have lots of holding torque.

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I did play with the parameters and did some tuning, but perhaps it can be improved even more. What I wish I could do is to prohibit the driver from going into low current mode, because I think that's what is the biggest problem. When the motor is on holding current, the driver reduces the current even more very fast after stop, which is OK if you are using the motor as a spindle motor, but not if you want to use it as a rotational axis, where the motor is mostly on holding. Of course, there are motors with dedicated electromagnetic brakes, but that might not be necessary if the current settings would allow full current all the time when the motor is stopped, as long as the driver is enabled. So maybe I missed one setting or maybe the PID regulator can be tuned even better.

Anyway, I have seen some YT video where the same issue was fixed by tuning, but those motors all had V6 firmware, and this is V5. I was in contact with the manufacturer and they said sorry, you need a V6 motor, which is why I complained to the seller, who in the end gave me full refund because he could not ship the motor he advertised. I am happy this way, but feel sorry for those who wont get a reasonable compensation, if the problem is due to the PID in the motor and requires parameters which don't exist in the V5.

Quote:

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Originally Posted by m_c

A quick search tells me a JMC 180W 3000RPM servo has 0.6Nm and 1.5Nm peak torque, so even through a 3:1 reduction, that's only 4.5Nm peak.
You can put that kind of torque through a decent screwdriver with a bit effort, so on a 4" chuck, it's not going to take much effort to move things.

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Yes, that was the way I was thinking also, I mean, 0.6Nm x 3 should work fine, but in the worst case, I can even change it back to 6:1, so the total holding torque should be fine, but what I noticed now that it seems like a sudden quick pressure can start the rocking, while a slow increase can not, so I think the problem with the PID must be fixed for this to work as I want it. Otherwise I can not use it. I don't know how other people manage with this servo, but it is my understanding that this is a very popular servo in the DIY segment of CNC builders.

What I also find strange is that I can NEVER, not once, force maximum current consumption, not even for a very short time. Because I think that is not good, since in that case it can not be called 180W at all. The maximum I could ever measure was below 2A. In my opinion, the driver should increase the current until maximum is reached when I try to twist the shaft when on holding, but long before maximum current, the motor throws an error and just release the tension all together, instead of increasing the current and applying more holding. So perhaps, the motor is a totally different one, while the label says it's a 180W but in reality, maybe it's just a 100W motor.

Anyway, I want to finish my "lathe" first, before spending too much time on the seemingly weak holding torque.

In case somebody have done this before, please help with some advice.

https://youtu.be/v9tR_K8eTek

I don't understand this crazy design. Why did they do it that way...?

Quote:

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Originally Posted by A_Camera

What I also find strange is that I can NEVER, not once, force maximum current consumption, not even for a very short time. Because I think that is not good, since in that case it can not be called 180W at all. The maximum I could ever measure was below 2A. In my opinion, the driver should increase the current until maximum is reached when I try to twist the shaft when on holding, but long before maximum current, the motor throws an error and just release the tension all together, instead of increasing the current and applying more holding. So perhaps, the motor is a totally different one, while the label says it's a 180W but in reality, maybe it's just a 100W motor.

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180W is the rated continuous power at rated speed.
Power output is directly proportional to speed, so at 300RPM aka 10% of rated speed, continuous power output is only 18W.

The only time the drive will draw full power from the power supply is when the motor is running at high speeds and loaded.

Now I had time to finish the video about the no load test. It is very quiet when there is nothing atached to the shaft.

https://youtu.be/NKZBIqMDUL8

Yesterday and today I 3D printed these wheels which will serve as machine wheels when it is time for the first turning job. Printing time: 7.5 hours each. Made out of three pieces each.

Attachment 30317


Have not yet decided if I will digitize my lathe or not. That decision will be made after some tests, and these wheels will be used until that decision is made.

If anyone is interested in the hand wheel, I made a video about it. There is also a link to more pictures and text and details about how to download the stl files in case you want to print and make one or two for yourself.

https://youtu.be/-YxlNM-9n5Y

I am now ready with the actual basic design and first version of my DIY micro lathe. So far it's only for manual drive, and not really did any test run yet, but the machine is ready and usable as a manual lathe. Not tested yet, because I want some safety features before I make a real test cut, so it is still only cutting air, but any day from now, I'll see if it works or not, but I am quite confident that it will work as I planned and designed it for, mainly small aluminium and plastic parts. If I manage to cut steel also then that will be bonus. Will probably also use for grinding and some threading.

Anyway, here is my latest video, showing the current status.

https://youtu.be/bVynxWKIoyI

Very nice little lathe look forward to seeing it cutting.

Phill

Thank you. I will keep this thread updated and will definitely post about success or failure after the first cut.

The last video of 2021, before popping the Champagne... :toot:

I am finally ready enough to use my lathe, and in fact have even used for more than just testing, in this video I am making parts for my lathe, but I even made some parts on order, which are not in this video. Of course, free of charge since the order was made by my son who needed two adapters and some aluminium plugs for his own DIY Christmas present project.

https://youtu.be/GLJs5FEZY1o

Anyway, I am very happy with the results so far, and will continue improving and digitizing it.

Happy New Year everyone.

This is what I have been working on the last two weeks, it's a huge power supply, providing 50V 82A (4kW) to supply DC power which is enough for all my DC driven machines if I'd want to connect everything to the same. It is based on four HP server PSUs, each giving 12.4V 82A, and those are all connected in series. Have a look at the details if you are interested. The primary reason why I made it this big and powerful was the fact that I have more than enough server PSUs to make it. The second reason was that I needed something more powerful for my lathe. Then I realized that I could connect my CNC to this one as well. So now I have connections for both my CNC and the lathe, and also for a desk motor which will be made for my lathe to be placed on.

https://youtu.be/dPv5n4Ds6W0

Nice job you've made of that!

BTW, if you connect PSUs in series, it's good idea to fit a reverse polarity protection diode across the output (not in series), to avoid damage if you accidentally short circuit the combined output. Otherwise there is a good chance you can damage one (or more) of them by forcing it into reverse voltage. Also the wiring to the shunt looks a little thin for 50A, although I'm guessing you won't be using the full current for a while.

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Originally Posted by Muzzer

Nice job you've made of that!

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Thank you.

Quote:

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Originally Posted by Muzzer

BTW, if you connect PSUs in series, it's good idea to fit a reverse polarity protection diode across the output (not in series), to avoid damage if you accidentally short circuit the combined output. Otherwise there is a good chance you can damage one (or more) of them by forcing it into reverse voltage.

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It's a good idea. I will consider this, or some other solution, but I believe actually that these server PSUs have internal protection against all kinds of errors. These come from servers with dual PSUs connected in parallel, where if one PSU breaks down for any reason, the other will continue powering the server without interruption. So I trust these have all the protection needed, but of course, one or two or three extra safety feature is not a bad idea. That's why I have the overheat shutdown function also, even if I expect the PSUs will shut down on their own also. In fact, I know they will, since where we have used these at my work, there have been several PSU failures and not a single fire or any other damage. The servers been replaced by more modern ones, so I removed a few PSUs and reuse those before scrapping the servers.

Quote:

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Originally Posted by Muzzer

Also the wiring to the shunt looks a little thin for 50A, although I'm guessing you won't be using the full current for a while.

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The wires are 2.5mm² so it will be a while before those become a problem, but I will keep an eye on them when the current more permanently exceeds 15-20A. I think up to that I am definitely safe with those, and to be honest, I don't think I will ever use it above 20A, which is 1kW on the 50V side.

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.

https://youtu.be/P0-3K8x2U9M

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.

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.

Attachment 31834

Attachment 31835

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

https://youtu.be/uQzUsYaM68Y

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

Number one update is to change the spindle motor.

Attachment 32276 Attachment 32277 Attachment 32278

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.

Attachment 32279 Attachment 32280

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.

This thread had over 100k views, and considering that, amazingly few comments, so it is sort of a monologue, but because of the fairly high interest, I will continue.

The recent updates of my lathe turned out to be really worth wile, the 600 W servo is really making magic. Cuts steel as I never could do before and not really thought it ever will. The new servo is also a lot quieter, which is good as well, so I am very happy with it. I also changed the tool holder saddle plate from aluminium to steel, and I think also that improves things. My next plans are to actually make it a bit wider and maybe also taller. As it is, the "throat" (the space below the chuck) is too narrow, it does not swallow as much chips and swarf as I want to. It is fine for very small jobs, but as soon as I want to make something bigger, it needs to be cleaned a bit too often. Anyway, using it is a real joy now.

This is what I made on it this week:

https://youtu.be/808WNVtjevI

The round bar was not turned down, it was a 12 mm diameter 48 mm long piece readily available, but most of the work is done on my DIY CNC lathe.