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matsuura 500v trouble- spindle will not start


Jul 5, 2016
the machine:
Matsuura MC500V, 1980
the control:
Yasnac 3000G,
two line LED display, non CRT interface.

description of problem:

I have worked with this machine for 6 or 7 years now. Machine ran all operations without difficulty last week, was shut down correctly on friday. Start machine this morning by normal procedure. Home it and give code to run spindle as warm up, as is normal, S800M3, EOB, (cycle start). No action from spindle. The rpm meter and the spindle load meter rest at zero. Going to the diagnostic display, no errors codes are given, an active M code is shown. Press (RESET) and try a tool change, T16M6, EOB, (cycle start). The spindle takes a partial rotation as the pneumatic spindle detent pin is engaged, the spindle speed seems correct, a slow revolution as always. The spindle is now in the correct orientation for a tool change. There are two limit switches for the spindle detent pin, one at the released position and one at the point of detent engagement. Both switches move freely. While the spindle has now taken the correct position for the tool change, the spindle drive motor (belt driven) continues its effort to rotate the spindle- zero rpm because of spindle detent, but spindle load is bouncing to appx. 50% as the drive belt slips on the spindle pulley until I press reset. This behavior also occurs with an M19 input (spindle orient). Other manual input code seemed functional (G28 home return was tested and operated correctly)

I hope I have provided enough information, I am at a loss on how to proceed- this is my only cnc and I have a large standing work order I need to get rolling on.

Thank you

I have just pulled the pneumatic operated spindle detent mechanism. I have checked both limit switches on it, with out power for continuity and under power, actuating the cylinder. they function correctly. I was hopeful it was a limit switch problem

Mcc Tool
I have the same machine with an MX-1 controller. You sound like you know what you are doing, and I agree that the limit switches for the detent seem like a good place to be looking (I am not aware of a spindle detent on my machine, IIRC I can hear the spindle drive respond when I manually torque on the spindle after a M19 - does that mean no detent?). I would just suggest that you monitor those switch states from the control to see if they are actually getting to the controller intact. And don't focus on the "engaged" switch; the "released" may be just as important. The only thing I can imagine would cause the symptoms you describe is if BOTH switches are not getting to the control (won't start spinning because can't see that detent is released, and won't stop at the detent because it can't see that the detent is engaged). So maybe a cable problem? I assume you looked at the spindle drive electronics and see no unusual red lights.
If you didn't meter test the detent switches, you didn't actually test them. As well, I commonly see them in a "gray state" in which resistance is not OL vs 0ohms, sometimes open is say 4K ohms. Have to watch for this.

Check IO state in control. that should tell you what is up but my bet is on a sticky or bad switch. Pretty much a dead giveaway that spindle continues to try even with detent locked. I would NOT continue that exercise or you will be fixing more than a switch! That detent system should be dead simple to troubleshoot and you are on the rabbit!
SeeFair, Huleo, I must start by admitting I am not much for electronics, though I am learning.

I agree on checking at the control. On the spindle drive, I see LED lights, but I have not found diagnostic information to make sense of them. I believe the spindle drive is a yaskawa type CPCR-QR756SD-4K. I have not found where the wires from those two switches terminate. Do you think it will be on the spindle drive or somewhere else in the electronic cabinet?

"If you didn't meter test the detent switches, you didn't actually test them." please explain- are you saying there might be continuity but with some resistance? Resistance should be practically zero?

"Check IO state in control." The matsuura has what the manual calls "Online Diagnostics" for checking and trouble shooting the system, this is found through the alarm menu and given as a series of binary code showing open and closed states for IO. Unfortunately while the manual references some of this, I have not made good sense of it yet.

Thank you for your time and input.... and patience.
Im not sure about Yasnac, my shops Matsuuras are all Fanuc drive, but same age range. If similar, on the spindle drive, there is usually Green LEDs and Red LEDs. the greens indidcate everything is good, Red not good. But usually if you get alarms on the Spindle Drive, the machine will go to a "not ready" state similar to pushing the E-stop.
Yes, you must use a multimeter on your switches. When free, you should get infinite resistance, when depressed you should get 0 Ohms or damn near it (can depend on quality of meter). The wires probably terminate in a terminal block either in the cabinets or in a junction box in the body of the machine. The manual should give you an idea of where it is located. For spindle and tool change functions on my machines it is a box on top of the machine. A MTB electric schematic should tell you what wire numbers correspond to those switches.
I took a quick look at the manual for the 3000G here. I can find a description of how to read inputs (page 153), but you need a list of inputs for your particular machine, which should come from Matsuura, not Yasnac. The generic inputs from Yasnac do not include spindle detent switches.

With regard to what resistance reading you should see on the switches: short your ohmmeter probes together and see what the ohmmeter reads; this is what you should see (approximately) when the switch is closed.
If you are a rookie, I will point out that part of the redundant process of computers looking at switches, is a switch typically (maybe not being that old) has both a normally open and normally close position NO/NC. It is a double confirmation that the switch has changed state. If you have 3 wires, one is common, one is NC, other is NO. The NC and NO will (should) change state when switch is activated.

What is confusing is there are no alarms so the above may not be the case, because one of the intelligent ways of doing it this way is the control will always know what state the switch is in, and if they don't switch sides, it can be flagged as an alarm.

To put this another way, if using 3 wire, if you totally remove a switch from the circuit, it should alarm because it is still looking for one of the two contacts to be made, ALL the time.
Huleo, I have had two 80s vintage Matsuuras, in the last year, that one of the proximity switches for Spindle Position Orient went bad on, and wouldn't transmit that the lock pin was in position. In both cases, the machine never alarmed out. The technician I talked to after finding the problem said that a lot of these older Matsuuras are very simple and don't have timers or comparative logic to indicated an uncertain state with the switches. The Machine sees that the pin is neither locked nor unlocked, but will just sit and wait until the signal it is expecting arrives.
I'm not sure if it is just a few machines, or all the ones from the 80s, but they seem to be very simple in their operating system. I can't even access the ladder logic on them, the PC/NC button does nothing.
I appreciate the advice on checking the NO/NC operation of the switch. I did check that on a whim last night. Each switch seems fine. that includes checking ohms now.

Chimpwithastick, you describe correctly the function, the machine will sit and wait for the correct signal.

running a voltage check across the switches and at the spindle servo drive pack, I find 9.8 volts. I believe this should be 24 volts to operate a relay that would give the "permission" to start the spindle. Going to the power supply, I find the power supply test point is putting 24 volts out. somewhere between the power supply and the spindle servo drive there is a significant voltage drop

again, thank you for all the input. your time is valuable and appreciated on this end.
It looks like the source of the trouble has been resolved. I received a bit of an education on how to inspect the voltages and when I measured from the limit switches to a dedicated ground terminal, I found the spindle detent ("key lock" according to the manual) only has 14 volts across it. tracing the wiring schematic those two limit switches daisy chain off the wiring loom that goes to the tool clamp/unclamp switches.
I made a jumper wire from the clamp/unclamp switches down to the detent, input code for a 200 rpm spindle start, pressed cycle start... then connected the jumper to the detent, at which point the spindle started as it should. I now have a wiring fault to trace, but I believe the trouble has been discovered.

Thank you.
Don't be surprised if it is actually a switch! A DMM is very high impedance so trying to move any current at all, they may still cause voltage drop. But sounds like you are on the ball now.
What is a DMM?

This morning, I started chasing wires through the loom. I found a broken wire in a daisy chain, making a couple cuts and a repair and I am back in business! (both grateful and greatly relieved )

Thank you.