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

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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.

[JAZZCNC]

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.

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.

[A_Camera]

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.

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.

[JAZZCNC]

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.

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.

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.

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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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.

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).



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.

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.

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.



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.



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.

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 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.