What's new
What's new

Turret will not find tool position

viper

Titanium
Joined
May 18, 2007
Location
nowhereville
We bought a new used Lico (POS) lathe that was supposed to be ready to go. Turret will not index a tool position. When you hit tool index on the control, it flips over like 6.5 positions and then errors out with bad encoder or problem relay. We replaced the encoder with another used unit with the same problem. Have verified drive motor contactor, relays, and prox switch are good. Acts like the turret motor just does not know when to stop turning or cannot stop in time.

I am thinking the encoder might be good because the IO chart indicates changes in position as it turns, and the control recognized which tool it is on. We are now working to test the encoder. What do you think?? Control issue or turret?
 
Did you check the prox. switch clearance or just if it was electrically functional? After the encoder the next thing I'd look for would be the prox. switch not being activated reliably.
 
Yeah, I checked what distance it would fire and also set the depth on the switch. Also verified that when the turret is in locked position, the prox switch is on. It is supposed to turn on when in ock position and it just seems like it just blows right by it and keeps turning. I guess I need to know the order of events to tell the turret motor when to stop. Also puzzled by why it stopped after 6 positions instead of just spinning constantly.
 
Count register just WAY off? Once it sees the "home" prox it prolly counts to a certain number and then locks up. Being out 6 positions would seem to be an astronomical number - but ???

Otherwise I would think that it would keep turing. Mine would! (and has)

Think Snow Eh!
Ox
 
What procedure did you use to initialize the encoder position? I suppose the encoder goes to its index when the turret is given the home command, but whether that really lines up the the turret #1 position properly is something that would have to be looked into.

I remember watching a technician retrofit a lathe for me. It seems to me he had to put the turret servo card into a maintenance mode, which decoupled the clamping of the turret. So the turret could be rotated at this point, by loosening a setscrew that clamped the encoder housing, and then rotating the housing. The turret would servo with the encoder housing rotation. When the correct position was reached, then the encoder housing was clamped solid and maintenance mode was then quit.
 
NO reference on the turret. It is an absolute position encoder. Seems to recognize position somewhat but the drive motor just never stops in a locked position.

With this unit, you cannot uncouple the clamping from spinning. All built in one. The motor basically spins on rev to the next index and one more rev to lock the cam, one more rev to unlock, and so on. The fact that the motor just keeps on going is telling me there is something not signaling the motor to stop. Encoder?? PLC??
 
What control have you got on the machine?Do you know what BCD code the control expects to see at each station?
From your original post it sounds like the turret only does single indexing and must clamp and unclamp before moving on to the next station,is that correct?
If that is the case it seems like the control is not seeing the code it is looking for and so starts another cycle.If it`s a six station turret that would explain the six and a bit indexes before it faults out.If it`s more than six station it`s likely the control is getting incorrect codes and faulting out.
If you know the bit sequence for each station,jog the turret one station by forcing the relay manually and check with a meter that you have the correct bit pattern,do that for each station.I don`t think it`s the proximity switch as the control would not re-index if it saw the station code from the encoder.
My experience with absolute encoders is that it is usually the most commonly used bit that fails first.When reading the output you also need to know if the control needs even or odd parity.
 
Yep, w sure do have the bit layout for each position of the encoder. I was kinda hoping we could reference positions in the IO chart in the control. The control is a Mitsubishi 500 and when I refer to clamping, I mean locking the turret in place. When you spin the motor it will just stop turning the turn head and flip a cam to lock the turret. It has an 8 station turret.
 
Anyone know if this was ever resolved or have an idea? I'm looking at making an offer on a Lico that has a similar problem and trying to base my offer off how difficult I think it will be to fix.
 








 
Back
Top