New Build, PM2700 lathe with Acorn, Videos and Photos <upgraded to AC servos>

[Aurelien]

Thanks a lot for your answers ! It is for me a real source of information, full of common sense.

[guitarchitect]

I found your videos on youtube, and safe to say I'm blown away! I've been on+off about converting my lathe, but if I could get to this level of functionality would I ever be thrilled! Quite a while ago I realized Centroid would be the best route for me, and this really seals the deal. Being entirely new to CNC I'm wondering if you could tell me a couple of things -

• why did you go the servo route for the spindle - do you think this approach is simpler than a VFD? I saw that you've basically set it up with a magnetic clutch - does that mean that you generally use your existing motor at a standard/pre-set speed for regular operations, or have you eventually just gone full servo for the spindle? my lathe has a DC motor already, is it safe to assume i can tap into it for CNC control (rather than needing a VFD) or are there certain criteria it (or the control board) needs to meet?
• do you even need the spindle encoder any more, now that you have the servo control?
• are there any headaches/challenges that you face today, or are there any things you wish you knew before you started?
• what did you do for limit switches - and did you do any gear ratios with the servos or is it all 1:1?

[suntravel]

Thank you-

I use a servo because it is smaller and better rpm control

C-Axis with clutch because of the lash in the gearbox

Encoder is needed because the gear ratio is not 1:1

Limit switches are NPN on one end, other end soft limit

Gear ratio for axis drive 2:1 with HTD belt

The conversion works like expected.

Uwe

[guitarchitect]

Thank you-

I use a servo because it is smaller and better rpm control

C-Axis with clutch because of the lash in the gearbox

Encoder is needed because the gear ratio is not 1:1

Limit switches are NPN on one end, other end soft limit

Gear ratio for axis drive 2:1 with HTD belt

The conversion works like expected.

Uwe

So in other words, would you have skipped the clutch and encoder if the lathe didn't have a gearbox and was fully belt-driven?
I'm in the final planning stages of my build and trying to figure out what I should do for the motor. the lathe has a fixed-speed AC motor and handles speed changes via belts, so a servo makes a lot of sense. If I can do both speed and position with one motor it would sure help!

[suntravel]

So in other words, would you have skipped the clutch and encoder if the lathe didn't have a gearbox and was fully belt-driven?
I'm in the final planning stages of my build and trying to figure out what I should do for the motor. the lathe has a fixed-speed AC motor and handles speed changes via belts, so a servo makes a lot of sense. If I can do both speed and position with one motor it would sure help!

Maybe, but then I would have used a 3kw Servo for the spindle to have enough torque and holding force for the C-axis.

Uwe

[suntravel]

Tested the precision with the scale on my lathe today again after some production time on it...

Very pleased with the result, stupid easy to set up, no jitter and a precision according to the 1 µm resolution of the scale



Uwe

[vanadium.f]

HI Uwe
what ingenious solutions...

you are a precious source of ideas

What model of electromagnetic clutch did you use?

Fabrizio

[suntravel]

HI Uwe
what ingenious solutions...

you are a precious source of ideas

What model of electromagnetic clutch did you use?

Fabrizio

Thank you.

I have a custom made one from Mayr,

Here are more infos:
https://centroidcncforum.com/viewtopic. ... 6&start=40

Uwe

[johannes]

Hi Uwe,
I am converting a Colchester Triumph 2500 lathe using the AcornSix, and happened to have a 3.8 KW AC Servo that I would love to try out for a spindle motor, driving the spindle direct with a 40mm wide belt.

I understand I should use an input on the AC Servo to switch between speed control and position control, but how did you wire this to AcornSix?

Is it correct to assume that you would run the AC Servo in Speed control mode using -10-0-10V analog outputs from AcornSix, and then use an input on the Servo to switch to Position control/C Axis. And use the Step/Direction outputs from the AcornSix for this.
Or do you use the Step/Direction outputs from the AcornSix only, to drive both Speed and Position mode of the servo?

Kind regards
Johannes

[cnckeith]

Hi Uwe,
I am converting a Colchester Triumph 2500 lathe using the AcornSix, and happened to have a 3.8 KW AC Servo that I would love to try out for a spindle motor, driving the spindle direct with a 40mm wide belt.

I understand I should use an input on the AC Servo to switch between speed control and position control, but how did you wire this to AcornSix?

Is it correct to assume that you would run the AC Servo in Speed control mode using -10-0-10V analog outputs from AcornSix, and then use an input on the Servo to switch to Position control/C Axis. And use the Step/Direction outputs from the AcornSix for this.
Or do you use the Step/Direction outputs from the AcornSix only, to drive both Speed and Position mode of the servo?

Kind regards
Johannes

no to this "Or do you use the Step/Direction outputs from the AcornSix only, to drive both Speed and Position mode of the servo?"