EMC2 and lathe retrofitting.

[GuntisK]

Hi everyone!
Im trying to retrofit old Soviet lathe 16K20T1, and so I have a couple of questions about it.
1) Spindle. There is a 11kw DC servo (Bulgar motors 47MBH) on it. Driver will be somewhat like modified UHU (but not the original one) controller. So-there will be STEP/DIR inputs for spindle. The first question- how threads cutting is controlled in EMC? As I understand to cut a very good threads, the detail need to be set on a zero point (from where cutting is started). Can I set a spindle like A axis? This thing will work or not? Or there is no need in servo? Im very confused with this one...
2) Turret. Can EMC control the lathe turret or there is just a manual tool change possible? I have 6-position, AC motor controlled turret (there is possibilities to change it to servo). Position is controlled with magnetic reed switches.
3) Limit/End switches. What is the situation with those?
Thanks for any help!
Guntis

[Big John T]

To thread you need an incremental encoder with an index pulse. The index pulse is what coordinates the spindle so each pass starts at the same spot.

Yes EMC can control your turret. Perhaps someone can chime in with some more info...

Limit/Home switches can be configured any way you like.

John

[GuntisK]

Thanks! Yes-there is an encoder with index pulse mounted on spindle. But what about spindle motor? This means that I can replace an existing DC motor with ordinary 3-phase AC motor?

[andy55]

If the DC spindle motor works and you have some way of controlling it that works well enough for you then you can keep it.
There's no need for the spindle to be under closed-loop. When doing threading EMC looks at how the spindle rotates and compensates with Z/X.

[GuntisK]

Ok-here is the overview of lathe. As all of You can see- there will be hard work to fully renew it- paint, do some mechanical works, etc.etc, but I will do my best.
In the next picture there is a spindle motor. In this case I will develop speed controller around MCU instead of STEP/DIR type controller as there is no need in this. This must work.
Third is encoder near the spindle shaft. I think there is no need to change it to anoter type as it give all necessary signals.Those encoders still produce in Lithuania, and they are very stable and good protected from electrical noise.
I would be very happy if someone could share with their experience about EMC controlled lathe.
Guntis

[samco]

Looks like fun

Good luck and keep us updated.

sam

[GuntisK]

Hi! New day, new questions. After thinking I conclude, that one LPT port is not enough to fully control lathe (beside step/dir, home/limit switches, spindle encoder there must be spindle on, turret control, coolant on signals (I think that it is not logical to operate these manually, coz there is computer to do this...)). As I know, for example TurboCNC can support 3 parallel ports. What is the situation with EMC?
Sorry about the noob questions- EMC is something new for me...

[samco]

emc2 will support up to 8 printer ports without modifying the source (strait from one of the developers - says it is a trivial change) There have been for sure people using 3 the I can remember.

If your going to use the printer port to count the spindle encoder - you will want to read this thread

http://www.cnczone.com/forums/showthread.php?t=53960

it has been said that if the encoder is of good quality you should be able to count at close to the freqency of 1/(base period+jitter)

sam

[GuntisK]

Thanks Sam for the fast reply!
Hmm- there is spindle encoder with 1000 pulses already installed on it. Maybe too much for this? From the link You given I understood that the ideal would be encoder with 100 pulses per revolution. (luckily I have other the same type with exactly 100 pulses ).

[skullworks]

Nothing wrong in keeping the higher count encoder, it will provide better feedback at low rpm. The only downside is it will limit the rpm you can thread with. BUT this is not a major limitation for most retrofits.

Only machines built as CNC from the factory can hope to have perfectly matched servos (to the moving mass) to say thread a 7/8-14 @ 2000rpm.

If your lathe ends up being limited to say 800rpm for threading its no big loss.

EMC can handle the turrit and spindle control. You can retain the DC motor or switch to an AC option. EMC is wide open to configure any way you need - provided EMC is getting the required feedback to control the hardware in realtime.

[GuntisK]

For me everything now looks like in schematic drawing below.Full circuit will be later. But... still dont know how to control that turret. Ok-there is possibility to use something like "semi-automatical tool change" by using microcontroller based device, but hey-thats not cool!

[samco]

couple things.. How are you going to change the spindle direction?

Also - your going to need the A/B lines from the encoder hooked up also. (this isn't mach you know )

sam