[trademark]

Hi all:

I have a dyna myte dm4800 with mits m3 control.
monday morning when we turned it on the machine would not home in the y axis. x and z axis homed fine. The axis can be moved with the handwheel and the display works as should.
when we try to home in y the axis moves very slowly till it hits the soft limit.

here is a list of things we have checked:

over travel limits on y and home limit on y......both ok
i have swapped the encoder from x to y .......did not help
checked servo and encoder plug connections
reseated the board on the control that i think handles the limits and home switches
checked parameters .....there were a few differences but they seemed to be unrelated.

does any one have any suggestions?
I will be in and out all day
but thanks in advance

Mike

[Caprirs]

The most likely problem is the limit switch for the Y axis. The sequence for homing the axis after the operator initiates is:

- Axis feeds at rapid until the home switch plunger engages. The switch is normally closed so switch engagement opens the switch.
- Axis slows to a creep until the home switch closes again after passing completely over the tab mounted to the base.
- Control looks for home pulse on the encoder.

Thus, the control needs to see the switch go from closed to open to closed again, then looks at the encoder.

So if the switch is stuck closed (plunger sticking fully out of the switch housing), then the control never sees the home switch changing from closed to open to closed again. If the switch is stuck open (plunger fully depressed into housing), the control thinks the axis is already engaged to the tab on the base and feeds until the switch closes again before looking for the encoder pulse.

It is possible with the switch on that machine for the plunger visible on the outside to be working properly but the microswitch inside the housing to be sticking.

[trademark]

Thanks for the reply ..

the switch seems to work some of the time.

I have ordered a new switch. I think this will solve the problem

Mike

[Fastest1]

I bought a machine (DM2400) and it had an error caused by a dirty limit switch. If it is the cylindrical switch with a single wire. Take it apart and clean it all up and reassemble it. Switch contacts are all gold. I did that and my machine fired right up. Unfortunately I had no way to communcate with it.

[JHCHOPPERS]

If you need any parts for your DM4800, I have all the MITSUBISHI MELDAS parts for sale:

3 Axis Servo Amp
Servo Motors
MELDAS Control
MELDAS Display and User Interface MPG

Thanks,
JH

[lathe tech]

I would say this is a common problem with this machine. My y axis would get a white gel inside of the moron switch body. I would remove the shcs and two Philips screws air blow and electric cleaner. If you are looking for any parts contact me soon. My mill was in a fire and will be parting it out. x and Y servos are ok. Control was damaged from smoke and heat. Give me a call 740 701 1054 if you need any parts. Ps I found it best to move x y and z off home and power down for the night. When I power up in the morning zero was 99.9%

[chrisgraf2]

We had this problem every couple years or so. Coolant would get in the limit switch housing and either ruin the micro switch or gum up the actuator. We found that if you take the switch apart and replace only the little micro switch inside it is a $10 item through MOUSER.COM. Much cheaper than buying the whole switch ass'y from the manufacturer. Also, take lot's of pics as you take it apart and use RTV or other sealant liberally on the cover when you reassemble it.