Daewoo Puma 12 Lathe - Spindle

[pinguS]

Hi All

Does anyone have a clue as to how the spindle can be made to stop rattling like mad, let me explain....

I have run a a part from Aluminium 2.5 inch diameter, worked perfectly.

Loaded up 56 mm Hexagon Brass, increased the pressure on the pressure knows behind the door as the chuck holds on the corners only. Run a few, but now there is a big ratling, sound from the spindle are, maybe the gearbox.

However we have checked the gearbox area, seems fine and has correct amount of oil. I don't think it could be a parameter accidently changed, as this is not going to change anything machanically.

Could it be that the chuck jaws are too close to the bar diameter, and do not have enough movement so the sensor is not picking up or something. Maybe the chuck unit itself is loose. Proximity switch gone bad, but this wouldn't explaing the rattling noises.

What happens now is that as you select gear (high / low) everything ok. But when you start the spindle, even manually at slowest speed, you can see the thing jumping and one would normally assume the gearbox. It sometimes spins for a while then just holts, this being in Automatic, manual it does stop, or doesn't even start spinning. (could this be a knackered door safety switch)

I have also noticed the chuck clamp light starts to flash after the chuck stops itself unexpectidily, also it is not on when the chuck is closed with the foot pedal. Only turns on when you flick the key on the machine, but as the machine is old, I have no books, so do not know what the key labelled chuck lock does. It doesn't seem to move anything. It is always supposed to be on??


Does anyone have a clue, please help.....

[Al_The_Man]

If its an older m/c, the spindle is probabally DC? Check the tach, tach brushes and the main brushes also.
Al.

[pinguS]

Machine has the Fanuc 10T controller, I don't like controller because I can't get angles working, have to put in X and Z everytime, but this is not the issue. The machine is around 1990's I believe.

[positiverake1]

Are you running bar stock? if you are what kind of spindle linner are you using?

[pinguS]

Nope, not bar stock, just billets. Another problem were seeing is that you cannot program like for example

G01 X1.0 A60.

If your starting at X0.0 and Z0.0, this should move up at 60 degree angle at least left or right, but the machine just travels straight up. Tried various combinations. But no luck.

[positiverake1]

You probley dont have the option for blue print programing, you know, using the A for angles and such, I know its nice,let the machine figure it out, you say its a t10 fanuc, if it has fapt software on it, it would be good to learn it, I have used it, and think its great for turning, some times I would use it just to get numbers, and put them in my rough and finish cycles (G71/G70) fapt for milling wasn't very good, but the turning is vary nice for how old it is, I wish I had it now, anyway back to your spindle problem, Im running a 1996 pumma 8s with a mits control (dont like the control) it dont have the chuck lock key, but my guess would be it is just to lock out the foot swicth, and how my machine works is when the chuck lite is on , it means it is clamped, when it is off its unclamped, what I would do is pull the chuck off and start the spindle, see if still makes noise, could be a loose draw tube , I swicth back and forth from the chuck to a collet closer all the time, its a 8 inch chuck, yours sounds like its probley a 10 inch, so dont hurt your self, let me know how you come out, you can e-mail me if you like at: pedub@yahoo.com

[pinguS]

Ok,

We have identified, or so an engineer has. It has something to do with the spindle drive board not set up propery. So the machine is not accurately picking up speeds properly, like a piston mis firing on a car.

We assume the Puma 12 has max speed of 2500 revs, correct me if I'm wrong. Even when you manually job the speed in forward, at speed of 0, yes zero, the machine still spins at around 90 revs. In reverse it spins at around 25 revs. Wierd. Engineers tried using a adjusting the dials on the board using some sort of machine reading out voltages, but still spindle jumps like hell when accelarating. (like a spe

Does anyone have and Daewoo Puma 12 spindle setting manuals to help, we only have the Fanuc 10t ones, but need something more specific to Daewoo Puma 12. Showing voltage outputs or something.

God this is confusing.

Even some parameter settings would help, as I have nothing.

thank you in advance

[Big_d]

I would say it is the spindle motor resolver. This causes the spindle motor to hunt as the controller try's to fire the phases to keep the rotation correct.

Drop the belts of the motor and check if it has any float in the bearings as this is normally the cause of this problem. No parameters or drive tuning will fix this problem if it is the resolver. When replaced it should be set with a crow to get the best possible wave form. Alternatively you could check this with a crow before you replace it. It is normally located on the fan end of a Fanuc spindle motor.
Cheers
Daza

[pinguS]

We have removed the belts and the spindle motor rotates almost perfectly, speed up and down and has no vibrations. The motor runs very quietly. We have checked this with the engineers and they said this seems to be ok. The motor seems to have no play at all.

As the belts are removed, no actual speed is seen on the screen, so by the look of things it has got to be something to do with spindle speed readout, as this when it all jumps about.

Am I making any sense?????

[Big_d]

Hello pinguS
When I normally test this I do something a bit dodgy but it gives me a good answer each time. I will put my foot on the motor pulley (Belts removed) and load it a little at low jog revs. You can feel if it is hunting.

If you are having trouble with RPM (Different to speed in this case) feed back it could be the spindle encoder. I have never seen one of these particular model machines but most use an encoder driven by the spindle shaft, belt or gear probably belt in your case. These can give trouble if the bearings are a bit rough. You will defiantly get finish issues if using mm per rev when this is giving trouble. I normally drop this belt off and spin the encoder and pulley to A) feel if it is rough and B) look at the feedback on the controller display. Disconnect the encoder plug and jog the machine does it still misbehave?

Another possibility is it could be related to the chucking confirmation/door switches (Although this will normally stop the spindle and it wont restart) Check the prox or switch and the cables feeding it, the power supply could be faulty or resetting due to excessive load. I have had this in the past when a hydraulic coil was faulty and overloading the power supply (Some bright spark had replaced the fuse with one that would never blow).

Spindle controllers are normally set and forget you should never have to tune them during the life of the motor. Something has changed to cause this to occur and this normally means something that moves. I have seen this happen with a rewound spindle motor before but not in service. Have the windings of the motor been checked as it could have an internal resistance problem (cooked,loose terminal) get it checked with an insulation tester and an ohm meter. Am I assuming correctly this is an A/C motor. May be a dodgy power transistor but you need someone to check that for you. If it's D/C with brushes it may be a semi conductor fuse other than that just call me Blind Bambi.

Good luck

Cheers
Daza

[ttorqueshop]

I have a Puma 6s with the O-T control. I don't know about your machine but on mine the chuck key changes the direction of the clamping pressure. One way makes it clamp with pressure pushing in. The other makes it clamp with pressure pushing out. So depending on which way you have it set, the light will only be on if the chuck is under clamping pressure. I feel your pain on not having any manuals! Mine didn't come with any either.