Takisawa TS-15, Fanuc 6T-B, 'random' stops, losing position offset after stop

I have an old TS-15 w/a fanuc 6t-b controller. This machine makes excellent precision parts, including threading at 80 tpi in stainless, and holding diameter to within 0.0003" (with some effort).

The lathe runs i'd say about 20% of the stuff that goes through my shop though and I don't give it a lot of attention beyond getting it to do what I want when I want it. I have a problem that has existed since day 1 (i bought it used, 1 prev. owner) - that is, the lathe will just stop. right in the middle of a program, or maybe in the middle of moving the axis with the spindle on in manual mode. I only notice when the spindle is running, I don't know if that means that it only happens when the spindle is running or not.

When the lathe stops, the axis' hold position, the program stops, and the spindle brakes to a stop (not an uncontrolled spin, but a nice braking stop). It's almost as though the E-Stop was hit. Maybe it's an intermittent e-stop? As I'm writing this I'm thinking I may hook up a datalogger to the e-stop circuit and see if it spikes or cuts out or whatever...

In any case, the really bad thing about this is that the lathe loses it's G54 position. The machine coord. system still works (reported in mm in the bottom left side of the screen). This causes me a lot of grief when running parts - for example if the part has threads, then it's scrap or I have to write a new program to resume carefully. Worse, is that it's a big safety issue for the machine. I once 100% rapided the turret right into my collet chuck because the machine lost it's coordinate system and I didn't realize it. When I started the next program, it's G54 was somewhere random and it went like hell right into the chuck. I hit the e-stop just in time enough that the only consequence was the tool holder got pressed out of the turret. Had I not been watching, it would have really crashed hard.

I have the maintenance manuals, and have tried to use the diagnostics page to learn anything. Everything looks normal. Also, no alarm codes ever show. The machine just comes to a stop, sort of 'resets' in a sense, and loses it's G54 offset.

There doesn't appear to be a machine memory problem as my programs never get lost, and the machine parameters are all there without trouble. The fanuc 6 has bubble memory - no batteries needed so it's not that.

I wonder about voltage stability. I run my shop on an RPC and cannot run my mill and lathe at the same time because of the fanuc's tendancy to stop more often when other devices are running.

Any experienced fanuc guys out there seen something like this before? Help would be much appreciated. I'm thinking of swapping the motherboard, but I don't have solid evidence that I need to.

Thanks!

I thought I should add a correction / more info about not being able to run other machines when I run the fanuc 6tb. When the machine stops, there are no alarms displayed, you don't have to e-stop and reset, you don't have to press reset. Nothing happens except it loses G54. When I have tried to run other machines simultaneously with the fanuc, inevitably the fanuc will stop, but with an alarm buzzer, then the whole machine has to be reset to shut up the buzzer and get back running again. This happens when one of the other machines in the shop brakes from a high spindle speed and dumps some voltage irregularity back onto the RPC. So, having read on the forums that fanuc's are voltage finiky, and having read in the maintenance manual that you're allowed only +/- 5% off nominal voltage, I fully believe that this kind of stop + buzzer (i dont remember if it gave an alarm code too) is due to voltage instability on my RPC.

All that being said, the machine stop problem i described above happens all the time, other machines on or not, and there is no buzzer, no alarm, etc. So, those two causes seem to be different, but it is still possible? that the stopping problem is due to faster voltage irregularities that do not generate an alarm or buzzer.

Another observation is that if you do e-stop the machine, it loses it's G54, and if you press the 'reset' button it also loses it's G54. I am suspicious that there is either some kind of intermittant open or shorted circuit in the e-stop, or a sticky reset button, or there are conditions that trigger an e-stop, or a reset.

that leaves a lot of options open. useful info would be, has anyone seen conditions that automatically generate an e-stop? or automatically generate a reset? could the motherboard be going bad in some way, or the power supply to the motherboard be going bad? so that it resets? notably, the reset that I am talking about doesn't blank the screen or anything, it just resets any alarms, and apparently clears the position offsets. it must be more like a bit reset not a power reset.

i'll check the circuits as soon as i have time. maybe I'll put my o-scope on in various locations to try and catch a triggered event, either a short, or an open circuit. I could test the e-stop circuit which is all in series, and I could check any circuits related to the reset button.

I have all the manuals for this machine and the fanuc controller so I have good circuit diagrams. I don't however have a good idea of how to read the fanuc logic diagrams to track down what an e-stop means, or what a reset means in terms of logic operations. that could be helpful info.

I found out why I lose my position when the spindle stops - I had the absolute / manual switch set to off, so anytime you press reset, it sets the x and z to zero, and the machine coordinates (in mm) don't get set to zero. that explains a lot, and it means that I am not losing my position in a bad circuit board way - it was a setting that intends to do that. so now that the switch is set to on (set to absolute) the machine no longer 'loses' / sets to zero its x, z absolute programming coordinate (work coordinate) system to zero. great!!!

so now I am still stuck with a problem of the spindle turning off randomly. its like someone pressed the reset button. the spindle shuts off and everything comes to a standstill / feed holds if running a program (luckily!). this tends to happen at low spindle speeds more than it does at higher ones. typically at around 1500 RPM or less the spindle is more prone to shut off at random.

Any ideas out there as to why my spindle might shut off at random with no alarm code given? also, the machine sometimes goes automatically to the diagnostic screen when this happens, but I have not been able to see any diagnostic bit information that indicates what the problem is.

We are experiencing a similiar issue, typically between tool changes when the spindle comes to a stop and turns back on. Our TS-15 generates an SFL on our FUJI amp board and throws the alarm half the time, and the other half it doesn't throw any alarm and just goes to machine not ready. The tech came out and cleaned the commutator on the motor and the tach, and now it happens much less frequently. I'm thinking about having the motor worked on. A local place said they could turn down the commutator and build new brushes to fit, so maybe that's the key right there. In the mean time I should probably figure out how to keep the spindle turning between tool changes.

If they turn the comm, make sure they undercut it as well.

Hello,, i m newer to this zone,, Recently brought old Takisawa-Ts15 with fanuc 6t controller. But unfortunately battery drained off and parameter vanished from machine. Need parameter to restart the machine .Please help me out