Need Help!- Following error Limit Exceeded

[inertialabs]

I Have a Bridgeport VMC 760 and with the help of the Forum it has been running very well for a year now until today, I am in the middle of a run of parts and the machine shut down and threw up this alarm

MSG 04:04:12 PM Following Error Limit Exceeded

I turned the drives back on and Homed the machine then started where I left off and finished the parts off. then and hour or so later it happened again Now it just won't work

Any thoughts or suggestions would be appreciated.

Thanks

[machintek]

The fact that it did home may mean an intermittent issue. MAYBE. 760-16 or 760-22?
Reason being the maintenance page. If you can get into it and in the left window bring up following error for X, Y and Z and monitor it in greater detail . You can actually see the positioning error on the right side of the page where it shows position and the error. With the drives off, grab the X and the Y ball screw and turn each. Does the machine count (change position value)? If you home it watch the position error for each axis and see which one is the offending axis.
It will probably be the encoder or the cable. Outside chance, the BMDC. I just had to replace a X axis encoder cable on a VMC1000. It moves in the plastic flexible wireway exposed to oil and coolant and eventually become hard and brittle. Th outside cracks, then wire flexes more where it is cracked and work hardens and breaks. You would be quite surprised the difference in flexibility where it is protected and where it is exposed.
Also if you try turning the X ballscrew by had and you have a lot of difficulty, it might be that the keeper plates became tight. I have had about half a dozen machine do this in the last 15 years. The fix is to rescrape the turcite on the keeper plates or use about a .001 shim to space them out. It cause the motor to run hot and melts the wires in the heidenhain encoder causing a short. Had to mention this because I have seen it more than once.
George

[inertialabs]

Hello George

Thanks for the advise, Just to clarify it is the VMC 760/22 with the DX32 control
ans Siemens drives, I should have put all of that in there first.

So I homed the machine while watching the following error for X, Y and Z and I saw

.0001 to .0004 on the Y
.0001 to .0007 on the x
.0001 to .0004 on the z

When I turned the ball screws the Y felt OK and there seemed to be good resolution between me turning the screw and the positioning from the encoder

The same for the X, except when I tried to turn the X it felt about twice as hard to turn as the Y, so I am thinking this is pointing towards your theory of the nut keeper plate


Also I notice a failure when the machine does a rapid in the X of more that 10 inches I never saw this problem because I am always milling a bunch of little parts and the machine rarely makes a big rapid move.

The problem you mentioned with the keeper plates becoming tight sounds like it could be it How do you get to it and check for that ?

Thanks again

Reason
--

[machintek]

You could turn your rapid down.
You could have a way oil supply issue as well as a gib that is loose and since it is tapered could jam in one direction and get loose in the other.
This machine has Box ways. There are steel keeper plates in the front and rear of the table clamping it to the saddle. There are socket head cap screws holding them to the table. They are accessed from the bottom. The part sliding on the saddle has turcite on it.
Crack the screws loose by about 1/4 of a turn. If the axis frees up then you indeed have a problem. I usually shim the keeper plates where they attach to the table to relieve the pressure. Bridgeport was not sure but believed that either the oil or coolant reacted with the glue holding the turcite and made it swell thus creating the additional sliding friction. My first experience with this was in Pensacola Florida at a place called Mercury Machine about 16 years ago. They had a house box fan on one side of the table to cool the motor to keep it running. Both axis should turn fairly easily with about the same force. There is a figure ratteling inside my head of 12 or 24 in pounds of force needed to turn the ballscrew. I had made a 10 inch arm and carried around a digital fish scale to measure it. If I find the true value, I will post it.

George

[inertialabs]

So I just got finished pulling everything apart and I found the following

1 Chips everywhere you don't want em
2 the ball screw for the X super tight
3 when I pulled the chip guards off the ballscrew felt really nice
4 the rubber wipers on the chipguards were swolen and it takes a ton of force to move
6 I pulled the rubber out and I am going to run it like that for a cycle ans see what happens

Could you please explain how I can slow down the rapid ?

Also could you recommend where I can get new wiper seals for the way covers.

Thanks Again

Reason

[machintek]

In the maintenance page, scroll through the parameters. One of them is the Z rapid rate. I believe another is the X and Y rapid rate,
Password is 111257.

Unknown where to get wipers. Try Hardinge but I would not hold my breath. Check the underside of the chip guards. I remember seeing a manufacturers ID tag on a VMC1000 a few months back.

George

[inertialabs]

Thanks I will give turning the rapids down a shot

I just ran the machine all day and only had 1 alarm go off, it was a different one

TL CHG NV Ram Write Error
Any Ideas what would make that alarm go off ?

Thanks Again

Reason

[JoBwan]

Originally Posted by inertialabs Also could you recommend where I can get new wiper seals for the way covers. Thanks Again Reason

inertialabs,
Try High Quality tools at www.hqtinc.com. I have a local tool supply company that buys a ton of bridgeport parts from them. Just a thought.

[machintek]

Each time the machine makes a tool change , it writes the current tool to the LCTLAUF board. It may be that the read write cycles for this flash memory is nearing its end.

George