Author Topic: Options for Lathe Retrofit  (Read 1555 times)

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Offline vertcnc

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Options for Lathe Retrofit
« on: February 20, 2015, 09:57:11 AM »
Just looking for some options for retro-fitting Mach 3 or 4 to and older lathe.

It currently has a Siemens 5 HP DC servo and drive for the spindle. 200V 3 phase input, most likely analog control.  Encoder coupled to Spindle.  My thoughts were to replace the DC servo with a AC motor and VFD and retaining encoder on spindle, just because of the voltage and unknown condition of current servo/ drive.  Would I be able to sync spindle to axis for threading?  What capability would I be losing besides positioning?

Turret and closer are hydraulic with solenoid control and some type of rotary switch for the 8 turret positions.


What's my best options for control, as far as breakout boards?

Thanks

Offline BR549

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Re: Options for Lathe Retrofit
« Reply #1 on: February 20, 2015, 01:36:51 PM »
You need to talk to HOOD. He should be along shortly.

(;-) TP

Offline Hood

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Re: Options for Lathe Retrofit
« Reply #2 on: February 20, 2015, 03:26:26 PM »
I would say if at all possible keep the DC motor, it will be much better than an AC Induction motor and VFD, more torque through the range and most likely better speed control.
Regardless of what you have for a motor you will be able to thread, assuming it is powerful enough not to slow down too much under load. All that is required is an Index pulse per rev fed back to Mach.

Now regarding the encoder, it all depends on what hardware you use, if using an external controller then the Index pulse from the encoder will be of too short a duration for the PP to see so you will need another means of getting an Index to Mach, most use an opto switch and a disc with a single slot.
 If you use an external controller then it is likely the Index pulse from the Encoder will work well. Be aware however that not all external controllers can do lathe threading, so before you buy one make sure it can.

Personally I would try and keep the axis motors and drive that are on the machine, they will almost certainly be high quality industrial drives.  They will also almost certainly be analogue command, ie +/- 10v command. If that is the case then your  choice of external controller is between the few that can output +/- 10v.

The ones I know of are
CSMIO/IP-A
DSPMC
Kflop with Kanalog
Galil.

The only one I have used of the above is the CSMIO/IP-A, I think it is a great controller but the drawback for the lathe is the threading is slow to pull out at the end of each pass and thus a groove is cut at the end of the thread, if this is not a problem then it works exceptionally well as it uses the full encoder for threading. That means you can actualy slow the spindle right down and speed up again and it track perfectly.
 The IP-A can also do rigid tapping by means of the M74 macro supplied by CS-Lab, that works great as well.
Here is a video showing my wee lathe doing threading, it has the IP-S , the difference being it is step/dir but other than that it is the same as the IP-A.
https://www.youtube.com/user/HoodScotland/videos?sort=dd&view=0&shelf_id=1

Here is a vid of my Chiron doing rigid tapping, it uses the IP-A.
https://www.youtube.com/watch?v=GNL2XdsJz2E



Of the other controllers mentioned above I am not sure whattheir capabilities are regards threading and rigid tapping, I know the Galil can use full encoder and I think also the Kflop/Kanalog does but not sure about the DSPMC.
Regarding rigid tapping, I know the Kflop/Kanalog can do it with a macro in a similar manner to the CSMIO but not sure about Galil and DSPMC.

Hood
« Last Edit: February 20, 2015, 03:32:18 PM by Hood »

Offline Hood

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Re: Options for Lathe Retrofit
« Reply #3 on: February 20, 2015, 03:38:00 PM »
BTW you can usually pick up Mentor II spindle drives for DC Spindle motors quite cheap on eBay, they are fairly bullet proof and are good drives. That is in the UK though so if you are in another part of the world they may be harder to find.
Hood

Offline vertcnc

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Re: Options for Lathe Retrofit
« Reply #4 on: February 20, 2015, 06:00:39 PM »
Hood,

Thanks for the info.  I did look at the some of the Mentor drives on ebay in the US and they can get pretty expensive in the $1500 to 2500 USD range.  That's an option if something comes up.  I was thinking of a Sensorless Vector AC drive which should have good low end torque.

CS-Labs would be my choice.   I would like to keep the current servos and drives just have to see what condition there in.

Thanks for the info.

Offline Hood

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Re: Options for Lathe Retrofit
« Reply #5 on: February 20, 2015, 06:13:43 PM »
My friend picked up a couple of Mentor II's on UK Ebay three or four months back, think he paid about £500 for a new one and a bit less for a used one. It is however a totally different market and I have seen things the other way round with, for example, Allen Bradley DSD servo drives, crazy prices in the UK but reasonable in the USA.

Regarding the VFD, the newer ones are certainly better but you are talking fairly steep prices for decent makes, from what I understand the Chinese ones are not that great. Then again it is a long time since I moved away from VFD's so maybe even the cheaper ones are catching up now.

Hood