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MV-JR tool change swing arm over travel


Nov 15, 2010
Mori Seiki MV-JR with later style electric tool change - After completing a tool change the swing arm returns to home position and then moves slightly back towards the spindle. The electric motor driving the swing arm does not stop at the correct time causing the extra rotation of the swing arm.

Could there be an electrical adjustment or weak electrical component that is not allowing the electric motor to stop soon enough?

Video - https://photos.app.goo.gl/LiGNMFX6eXdZWr2Q6

Mathew- that style tool changer is totally different that the one i sent you the parts list for. In addition to a breaking contactor or a keep relay setting, I would check the cam followers that run in the tracks of the barrel cam and make sure they have not come loose. From your video, that looseness may well be a mechanical problem. The cam followers have studs that screw in and over time they can come loose, allowing slop in the mechanism. I found replacement cam followers on the internet with a little searching. Your tool changer appears to be much simplified from the on on our machine. Suggest you call Mori service or parts and ask them to send you a parts list for your serial # machine. Mori was very helpfull when we had our problem, but that was prior to the DMG merger- tell them you need the parts book oin order to order parts.
The mechanical side of things seem to be in good shape. The machine came from the local community college with less than 1,000 hrs of operating time and the swing arm has about 0.040" of free play.


I found the braking contactor that controls deceleration on the BU1 board position #2. During tool change the LED does illuminate. It may be safe to assume this means the proximity sensor is working to initiate the deceleration but would the LED illumination also indicate the contactor is working correctly too?

Video - https://photos.google.com/photo/AF1QipOB4R1kdfgfvcfU_zDl5GPUx2PsO4z4oiK-Mr1E
The contactor is driven by the relay on the BU board, not on the board. Do you have a schematic for the machine? If so post a picture of the page showing the connctions to the motor that drives the toolchanger. Someone here will then be able to give you better information on identifying the contactor.
Ah, ok.

Here are wiring diagrams:


It looks like MS4 is the contactor. Would monitoring voltage at S114 on the output side of the contactor tell me things are working up to that point?

Not likely. When a toolchange finishes MS4 should click on then off. Does it do that? If not then checking for voltage at 115B would tell you if the BU1-2 relay is operating. If MS4 does turn on and then off you should check for DC voltage on the output contacts of MS4. The injection of DC voltage into a 3 phase motor makes a powerful braking effect. Without seeing more of your schematics I can’t tell you exacly what voltage levels you should see on those tests.
Well, the plot thickens. The machine performed 20-25 tool changes yesterday and behaved perfectly. The arm rotation stopped in exactly the right spot and was very repeatable each time. I observed the MS4 contactor working correctly each time. The machine had been sitting for about 10 months and I wonder if there was some corrosion buildup on the electrical contacts which was presenting the issue? I will continue to run the machine and keep an eye on it.

I truly appreciate all the help from this group! I learn something every time I come here.