Gross Position Error

[Mike Conboy]

We have a Bridgeport series 1 Interact machine fitted with TNC145 controller.

On rapid Z traverse away from work (never towards work) it gives a "Gross Position Error".

What does gross position error mean?
Why do we only see it on rapid Z up?

Also does anyone have circuit schematics or a service manual for the same machine? Need something showing how all the servos and tachos are wired.

All help and ideas will be gratefully received.

[pestana1957]

Hi I also have a bridgeport serie 1
you can find all you want on the bridgeport site at the adress, http://filebase.heidenhain.de/doku/o...9E/N12B9E.html

[Al_The_Man]

Probabally the following error gets too large, the difference between where the axis is supposed to be and really is.
This error margin can usually be widened by parameter.
Al.

[gridley51]

"Gross positioning error" definitely heidenhain`s most common message.It`s machine related as opposed to control and as Al says can be got around by changing a parameter.I would check the axis mechanical things first.Are they Sem motors on that machine with tacho and encoder built in?Is it possible the gib adjusting screw is letting the gib tighten the slide in one direction?I have wiring and maintenance manuals for that machine with a 150 control but the electrical drawings won`t copy.I need a magnifying glass to read them.If you have specific electrical questions,ask and I`ll look at the drawing.
Mark.

[machintek]

As mentioned when the actual position lags behind the command by exceeding a value specified in a parameter, it will give that error.
Note that the error occurs going up against gravity.
Possibly: a weak motor. It is a DC motor with brushes which are probably worn out. The drive tuning may be off, and lastly the oil around the quill/ballscrew is incorrect/lacking/gummed up. Try flushing it with kerosene and reoiling with a mobil vactra number 2 or eqivilant.

George

[caniggia_100]

My mahine gets this same error not always, but often in this same position on axis X, when fast move is done up.
with slow ones it works ok.

Any ideas?

Greetings
Pawel.

[machintek]

What model Bridgeport?
What control?

Jurek

[caniggia_100]

Hi,

It;s Bridgeport Series II Interact II with Heid TNC 151B
control.

I'm going to check motor and tacho next day, as decribed in some posts before.



Pawel.

[machintek]

Check motor brushes, armature, cable and gibs/oil, ballscrew, and bearings.
Swapping X and Y motor would tell you quickly, if it is the motor.

George

[caniggia_100]

Thanks Jurek,

I'll check my motor on Z (I did mistake -my problem is with Z).

Thanks a lot.
Pawel.

[caniggia_100]

I did some invetigation today, checked tacho, brushes, all clear. Brushes like new ones. Exact Error is with letter A -
Gros positioning error A. I called Heidenhain,
they told me that this can be mechanical fault, in the moment that it stops it has not enough power to pass trough this moment.

i'll check today.

Pawel.

[gridley51]

Al said
"
This error margin can usually be widened by parameter."

Which is what I usually do if I`m in a hurry asnd don`t want to spend time looking for the fault.Reasoning being when it gets worsre it should be easier to find.

Thing I`ve noticed with Interact 1`s is,if they are on short X cycles I can get a shortage of lube eventually on the slides at the drive end of the X.
Has anyone else noticed this?Does the lube get pumped to that end or does it rely on table travel?
Mark.