Author Topic: Retrofit of an EMCO 120 CNC lathe  (Read 748 times)

Offline mukanico

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Retrofit of an EMCO 120 CNC lathe
« on: March 06, 2019, 07:42:59 AM »
Hello everyone,

I would like to present my project of retrofitting an EMCO 120 CNC lathe with a modern controller and new servos.

The lathe was bought in 2017 and it came from a high school. It was in good condition but the fact that it required three-phase power and had a vintage Emcotronic T1 controller (with the inherent risk of potential problems that could derive from its age) pushed me to take the decision to retrofit it and convert it to single-phase power.

For the axes, I chose to use 750W AC servomotors and drivers from DELTA, model ASD-B2-0721-B, to replace the original 5-pole Berger Lahr stepper motors.

The original spindle motor was a 400V DC motor with 3.5hp. To simplify its connection to the new controller, I decided to replace it with a three-phase motor (2.2kW ABB branded) controlled by a single-phase input VFD (DELTA VFD022E21A).

The choice of the controller was a bit more difficult ... At the beginning I thought to use Mach 3 or Eding CNC but the fact that these systems are PC based didn't convince me. Therefore I decided to take the risk of buying a dedicated Chinese controller on Ebay. My choice fell on a Szghauto "brand" controller (model SZGH-CNC990TDb-2).

Apparently, as with most products coming these days from China, there are many available controllers similar to this one in which only the brand changes (Szghauto, Newkye, Newker,...). From what I understand, they are all "inspired" by vintage Fanuc controllers. For the moment I am quite satisfied with it. The price was competitive when compared to the cost of a license Mach 3 or Eding CNC + computer + screen + cards, etc. The only problem was the documentation. The Chinglish was almost incomprehensible. I wasted a fair number of hours because of it...

I will add the photos next...
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Offline mukanico

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #1 on: March 06, 2019, 08:31:09 AM »
The original EMCO 120 lathe


The Emcotronic T1 controller


The original electronics


Beginning of the disassembly (original headstock motor removed)


Original headstock motor



Original 5-pole stepper motors


Disassembly of the lathe part


Cleaning the headstock



Disassembly of the electrical cabinet
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Online awemawson

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #2 on: March 06, 2019, 08:45:34 AM »
Welcome to the forum Mukanico  :thumbup:

Glad to see others rescuing and updating CNC equipment, good luck with the project and keep us updated.
Andrew Mawson
East Sussex

Offline mukanico

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #3 on: March 06, 2019, 08:46:36 AM »
The new controller (customized by the manufacturer with the EMCO logo :headbang:)




The 750W AC servo/driver from DELTA


The new headstock motor from ABB


To mount the new controller in the electrical cabinet, I ordered a 4mm thick laser cut steel sheet and attached it to the existing cabinet front cover




I also took advantage of my order to cut out the mounting plates for the new headstock motor, the servos, the limit switches and a back plate for the electrical cabinet




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Offline mukanico

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #4 on: March 06, 2019, 08:52:27 AM »
Welcome to the forum Mukanico  :thumbup:

Glad to see others rescuing and updating CNC equipment, good luck with the project and keep us updated.

Thanks!

The retrofit is actually already completed. I thought that sharing my experience might be useful to somebody that is now starting such a project, especially because I followed a different route than what is commonly seen on the web (Mach 3, LinuxCNC, etc.). 
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Offline mukanico

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #5 on: March 06, 2019, 09:11:00 AM »
Since the original headstock motor had a maximum speed of 6000 rpm and the new engine only had 2850 rpm, I had to increase the diameter of the driving pulley so as not to lose too much top speed. In the end, I managed to have a maximum spindle speed of 4250 rpm.


I also had to change the headstock encoder. I chose an "omron" with a resolution of 1024 steps/rev (x4). Its support was machined in a small EMCO Compact 5 CNC lathe that I had at the time...



Beginning of the wiring




Wiring finished






And new vinyl decals (of course  :headbang:)



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Offline mukanico

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #6 on: March 06, 2019, 09:21:21 AM »
And here is the finished lathe on its new custom made bench


And doing its job...



Overall, I am quite satisfied with the end result. The controller takes standard G code (USB or RS-232) and is quite simple to use. The mechanical part of the lathe does not seem to have much wear neither. The backlash in the ball screws is less than 2um and I can easily work within 0.01mm on mild steel.

The only annoyance I have is the lack of torque at low speed. I may need to reduce the belt pulley ratio and tweak the VFD settings to mitigate this.

I hope someone finds this project useful  :wave:.

Cheers!
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Offline RotarySMP

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #7 on: March 07, 2019, 08:32:01 AM »
Nice clean retrofit. Thanks for sharing it.
Putting that 3.5hp DC motor back in would also solve your low torque but also high speed issue.
Mark

Offline mukanico

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #8 on: March 07, 2019, 09:46:32 AM »
Nice clean retrofit. Thanks for sharing it.
Putting that 3.5hp DC motor back in would also solve your low torque but also high speed issue.
Mark

Thanks.

Indeed, I felt bad for not using the original motor (it was a beast compared to the new one). Unfortunately I don't know much about electric motors and their drivers, so I decided to play it safe and go for the straightforward solution of a 3 phase motor + VFD, instead of messing around with the EMCO driver.
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Offline RotarySMP

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #9 on: March 08, 2019, 04:02:25 AM »
Wonder what the EMCO spindel motor driver interface was? Analog 0-10V?
To replace a DC motor with a AC motor, you normally need to go up significantly in power, not down.
Mark

Offline David Jupp

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #10 on: March 08, 2019, 04:06:02 AM »
Was there a specific reason for using a flameproof motor, or was it just 'available'?  They usually carry a significant price premium and can have a long lead time...

Offline mukanico

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #11 on: March 08, 2019, 07:32:34 AM »
Wonder what the EMCO spindel motor driver interface was? Analog 0-10V?
To replace a DC motor with a AC motor, you normally need to go up significantly in power, not down.
Mark

Honestly, I have no clue... When I saw the 400V on the motor tag I decided to use a VFD, as I only had 230V single phase available at my home shop. Probably there was as a way to use the original motor, but I chose the easiest route for me at the time.     

Quote
Was there a specific reason for using a flameproof motor, or was it just 'available'?  They usually carry a significant price premium and can have a long lead time...

No reason at all, just what I found at the time on the local classified ads. It was a new old stock motor that I was able to get for 100...
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Offline PekkaNF

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #12 on: March 08, 2019, 11:11:38 AM »
Very good work. Well done.

....
For the axes, I chose to use 750W AC servomotors and drivers from DELTA, model ASD-B2-0721-B, to replace the original 5-pole Berger Lahr stepper motors.
....

How are those Delta motors/drivers documented and how easy they are to work with?

Offline mukanico

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #13 on: March 08, 2019, 11:30:12 AM »

How are those Delta motors/drivers documented and how easy they are to work with?

Pretty easy, actually. It was my first time using AC servo motors and I found it quite straightforward. They take standard differential pulse/dir signals. The documentation is very well written and the parameters are pretty clear to understand. In addition, DELTA provides a free PC software that you can use to communicate with the driver and setup everything as well as do the tuning.

The only thing to note is that there seems to be a few clones/counterfeits of these motors/drivers going around. To be honest, to this day I'm not sure if I bought the original or the clones. They look and feel too good to be a clone, but since I bought them on Ebay directly from China, I can't be sure of their authenticity.   
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Offline mukanico

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Re: Retrofit of an EMCO 120 CNC lathe
« Reply #14 on: March 11, 2019, 01:56:13 PM »
Hello,

Quick update to this build: I went back to the original motor pulley. I had to increase the VFD max. frequency to 83Hz to reach the original 4000rpm max. spindle speed but the additional low end torque is quite useful.


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