[greg b]

Hi all,once again im back on the bridgeport interact 1 mk11 y axis gross position error,I had a bit of a poke around like gus suggested on the tuning of the lag side of things and just couldnt see anything in the mode positions that co insided with this.Any how it has also failed when not in motion at all but only once and im hoping this is not a preveiw of something worse to come.It also has the last 2 digits in all of the axises flashing but it does'nt seem to worry its positioning when comanded however the hand wheel seems to drift of position in that mode when you let it sit and I was wondering if this has anything to do with this error that comes up at y axis feeds above 3000,anybody out there seen this before with a heidenhain 2500 control.Thanks in advance.Greg.

[machintek]

Check the brush length of the armature brushes. These are DC motors.

George

[greg b]

Hi George good to hear from you again,you suggested this once before and I pulled the motor out but really could'nt see anything that looks bad. How long is the minimum length for the brushes and would they have any real impact on the rest of the machine like those digits on the contol flashing (only last 2 digits) and the hand wheel drifting off its position while setting up.I must admit the Y axis motor sounds very different to the X axis when toggled at max speed. I did'nt want to poke around to much with the motor being a little worried about damaging the encoder,however if it needs further investegation Im happy to do so,could you think of anything in the control that may be causing these issues other than the motor. Regards Greg.

[gus]

Adjusting trailing error[lag] is a basic function you need to know how to do. Without doing it you are just wandering around.

mod

display

options should be something like ref actual lag

get a manual

[greg b]

I have the manuals and can not remember seeing it in there,but I will check it out again regards Greg.

[greg b]

Had a bit of time this morning to check things out a bit closer,how things get forgotten so easy when your machine runs realiable for a while,soon as I opened my manual it all come flooding back with some notes I added when I first bought the mill and had things to repair along with ajustments like possition Data.Soon as I looked at possition data I thought you goose,it was as simple as moving from acctual to nominal, to get the hand wheel from drifting and the numbers from jumping all over the place,however I dont ever remember having to touch the Lag and soon as I put it into that mode it became apparent straight away how far it had drifted from zero,it took a lot more than one turn from the pot to get to zero and stabilize, and I thought we almost had that Y axis error licked,but after several attempts to get it to work without error no good ,so I will take the motor out again and see if I missed something from last time.Thanks for putting me on the straight and narrow again Gus,I have'nt picked that manual up for years the mills been so realiable, its been my cincinatti Iv'e had all the hassles with over the last 12 months and the controls are totally different.Thanks again for all the help.Regards Greg.

[gus]

See, now you know something. If it will not adjust you have a tach error of some sort. If it is only really on the high speed, I would guess bad/dirty brushes. I have never had to change them, but have had them get gooey from coolant etc

[machintek]

Per a service bulletin I have posted here many times, the motors should be examined every 4000 hours of operation. This equates to 2 years of running at 40 hours a week.
I will be the first to admit that most run a lot longer before needing attention. Typically 7 years with the Z being the first to need attention.
To check the tach quick I put the suspect axis in a slow feed. If the tach is dirty, it will not move perfectly smooth.
If armature brushes are worn (or dirty or stuck), the necessary current to maintain acceleration and thus following error to a minimum is not there and the lag grows to more than allowed in the respective parameter and you fault out. Adjusting the drive may help but will not correct a bad brush situation.

George