[aaroncswenson]

Hello All,
I am new here, seeking some enlightenment A friend just purchased a used MC-5VA, not sure the year manufactured, S/N 0201-0995. Upon turning main power switch to "on", fuse D6 on the Vaci-Drive Unit, the 1st 5A fuse, blows out, but we get no alarm. Don't know if this has anything to do also with the Z-axis overtravel when attempting to perform a tool change cycle? Z axis moves fine, spindle rotates, clamps and unclamps tools manually just fine. Searched through books and am guessing a limit switch problem with the overtravel alarm, but as for the fuse, I dunno Not sure if this is a common problem or if it will cause problems if not resolved, or what leads to this? Any help would be GREATLY appreciated. Also would I be able to find out anywhere what the factory default limit settings are? I believe it is set to positive Z at 22.1226 (inch). That too high? Sorry for so many questions. Thanks!

[underthetire]

5 amp fuse sounds like a fan motor fuse. I don't remember any okuma's with only a 5 amp for the actual drive units themselves.

[Algirdas]

it looks, like the fuse did it's work - blowed out instead of device it protects.
There could be many reasons. The worst is weakness of power supply.
Limit settings are recorded on "data management card" which must be in the machine itself. Check all cabinets, open all doors to find it.
Don't leave doors open :-)

[Superman]

Underthewire may be on the right track,
Check the actual fans in the cabinet and on the spindle drive motor, they may be shorting out or seized ( stops you cooking a more expensive part )--early machines were very general and very vague with their error diagnosing.

Don't know if this has anything to do also with the Z-axis overtravel when attempting to perform a tool change cycle? Z axis moves fine, spindle rotates, clamps and unclamps tools manually just fine.

No, this is seperate from a blown fuse, normally with limits set corretly, an Okuma will only overtavel to the soft limit on all axes, if it goes onto hard limits a switch triggers a level B alarm shutting the machine down but leaves the control ON. If the machine goes onto hard limits, the look at the limit settings as per "Al".

These machines make use of a preset positioning code ( G30 ), similar to a G28 on a Fanuc
I think this machine has a minimum of 8
so instead of programming a

G15 H0
G0 Z25.
X-25. Y15.

try using a

G30 P1

if set, it retracts to the Z toolchange level first then ( if also set ) to a safe XY toolchange point. Try it with Rapid set down low ( if they are not set, then X0Y0Z0 is the reference point and that is the central top face of your table ( imagine if you had a tool in the spindle )) so your 1st movement should be Z+

I believe it is set to positive Z at 22.1226 (inch). That too high?

This machine has the tool carousel fixed onto the side of the machine and the toolchange swing arm location is also fixed and does not travel with the spindle head, so the Z axis must go to it to be able to change tools, arm swings onto the tool in spindle, swing arm lowers, and rotates to place the tool in the tool carousel pot

We have a MC-6VAE and the Z return point is 24" ( 615mm), mind you the tools are a BT50