Reversing ORAC's main spindle

[seaman77]

Hi everybody!
I'd like to discuss with you, ways to reverse the ORAC main drive motor.
In the PARAJUST manual it is written that in order to do this, one has to replace the
standard control module with another named...reversing control module. This makes the machine incomplete.
And for a lathe that was new back in the 80's I believe there is no much hope to find
extras.
Personaly I don't wish to upgrade this machine. I just want to restore it to its original specs if possible.
So maybe someone here knows another way for reversing the spindle without the use of the above mentioned module. I can only understand that one of the Orac's aux. relays could be programmed to be activated when the tool travel reaches the predetermined Z-coordinate. But how to pass this signal to the PARAJUST inverter is something that I totaly disregard.
If anyone has an idea of how to do this please give a hint.

cheers

[Denford Admin]

Does the motor have a tacho for speed feedback ?
If so you could try swapping the tacho wires over to see if it reverses direction (check it's possible in the manual first)
If not, does swapping a motor phase reverse the direction ?
If so, you could possibly use a relay to change-over the tacho wires, or a contactor to change the motor phases.
You'd need to interlock the changing of motor phases while it's running though, as it could well destroy something

[Martin]

The Orac was fiffed with 3phase motor so inverting 2 of the phases to the motor would reverse the direction.

If you wanted forward & reverse then you could as Andy says fit a changover relay driven through a additional output.

The normal drive would be a Parajust

The Orac never had a Tacho fitted.

[seaman77]

The Orac was fiffed with 3phase motor so inverting 2 of the phases to the motor would reverse the direction.

If you wanted forward & reverse then you could as Andy says fit a changover relay driven through a additional output.

The normal drive would be a Parajust

The Orac never had a Tacho fitted.

Well, there is a perforated disc revolving with the spindle and an infrared, pulse pick up, tiny board there. This simple pulse generator produces about sixty pulses per revolution I think. I should check the number of holes and know first hand. It looks to me all that, is not there for just counting revs. There must be a comparator circuit somewhere in the main board receiving a feed back and then sends the result to the computer for calculations and to adjust speed according to the programmed commands because Orac is capable of varying spindle speed during program execution.
This takes a little research and tracking of the signals to see which circuit or IC port is being triggered by these pulses but I do not evaluate myself as capable of doing this.

cheers

dimitri

[Martin]

The sensor feeds the spindle speed pulse & threading pulse back to the control system.

Once a requested spindle speed is called for the control outputs a anoluge voltage of up to 10 volts DC so at half speed it would output roughly 5 volts DC. When a cut is taken the control then monitors the actual sp[indle speed & will adjust the feed rate if set to run in constant surface speed. The spindle speed may drop slightly depending on the cutting load & current compensation set on the drive.
When threading the second optical sensor is used for the threading pulse.

[Martin]

The sensor feeds the spindle speed pulse & threading pulse back to the control system.

Once a requested spindle speed is called for the control outputs a anoluge voltage of up to 10 volts DC so at half speed it would output roughly 5 volts DC. When a cut is taken the control then monitors the actual spindle speed & will adjust the feed rate if set to run in constant surface speed. The spindle speed may drop slightly depending on the cutting load & current compensation set on the drive.
When threading the second optical sensor is used for the threading pulse.

[seaman77]

Yes right!
There are two sensors there and I was wondering why.
So the second one is for threading. I did not know that.
Also, the perforated disc has one single slot at the periphery next to the first hole.
The way Orac does threading is unique. I do not know another machine doing threads this way. Usually tool escapes at an angle equal to threading angle when reaches the end of thread (Z-coordinate). There is no need of reversing the spindle so far. But I was about to start a taping cycle with this lathe when I suddenly realized that this, can not be done on an Orac because Its spindle does not reverse.
...That's right Martin. I need forward & reverse. So a relay could be triggered by one of the auxiliary outputs right?
This sounds easy.

Thanks

cheers...Dimitri