Need Help!- TNC155 POSISIONING ERROR

[mark562]

Hey All

Recently bought a INTERACT I Mk 2 with a TNC155 control. ( have 2 others with TNC151)
It ran great for 2 months, Then today started giving a POSITIONING ERROR when rapid in X-axis, this not the dreaded GROSS POSITION ERROR this clears easily from the CE button.
After 3 or 4 errors and clear and run cycle's the x-axis started running real rough while feeding. So assumed a bad servo motor and I replaced it with a known good working used one from my other machine.
This did not fix so I replaced the drive board also good working used. Still no luck and spent several hours checking wires. all seem good with no visible cuts and good continuity.

So now I am lost. Does any body have a suggestion?

Thanks
Mark

[gus]

servo amp needs tweaking

[mark562]

Servo amp? Is that on the drive board or in the control? And how is it tweaked?

[gus]

go through the back posts on this forum. there are several explanations

[mark562]

GUS

Found this in one of your posts DTD 11/18/10

sent a pm, have posted this or similar before

tweaking[tweeking] bosch servos on an heidenhain

fool the control door interlock to turn on power with door open
find the z axis servo amp, there is a pot marked 'tacho'

write a program running the subject axis at rapid to near its limits in a continuous loop.

you should set the parameter feedrate to what you want them to be [was it 5000 m/m...] you may want to leave the z a little lower, it doesn't hurt you much and I always had trouble keeping them reliably fast

change, IIRC parameter 22 to 'on' to enable trailing error mode

the control now shows you trailing error rather than position

turn feedrate pot down and run the program, turn it up to a point at which it will run reliably.
pull the contol around so you can see it while you turn the tacho pot. adjust the pot to get as near zero trailing error at the center of travel[tricky on z]

turn the pot up some and repeat.

it should be subtle changes, maybe a turn max.


If it will not settle or if the trailing error is random and noisy, you may have other problems, like a dirty tach.

trailing error should rise on accel and decel, stabilize in the middle, drop to near zero as it comes to a stop


Went to the shop and tried it on my X-axis problem. The first problem I encountered was when I change a parameter ahd push DEL to exit the parameters I get an POWER INTERUPT error and have to home the machine again. Is this normal for the TNC155?

NEXT the parameter 22 is for counting direction so Z home would go backward and gross position out.

I found on the matint. manual the proceedure balancing the tacho, however no matter how far I turned the tacho pot the numbers would not change and are still an approx. 30 % difference

Do you think this could still be a bad encoder/motor or could there be something wrong with the control?

[gus]

instructions were for a 145

on a 155 you just do it through the mod key

[Jukka Honkanen]

Hello Mark.

The problem that you are describing might be on the motor tacho.
So open up the (carbon brush coals), or what ever they are called, and clean them. One thing you could do is clean the whole collector. Maybe wiht a sandpaper. Anyway DO NOT TAKE the collector out of the motor.
It is a permanent magnet tacho and if you take it out without replacing some metall to its place you, will loose the magnetism on the tacho.
The "POSITIONING ERROR" comes when the LAG goes higher that MP56 or MP175 depending on the positioning mode (MP60).
This cleaning should help your problem.

Jukka

[mark562]

Thanks Jukka

I will try this in the morning. Would you happen to have a exploded view of this motor? As I have never taken one of these apart and do not want to remove more parts than needed.

Mark
E-mail: mvfabricationinc@sbcglobal.net

[Jukka Honkanen]

Send me some photos of your axis motor.
The motor should have caps for the coals.
First step is to remove them and blow the holes with compressed clean air.
Test the movement of the axis.
You might need to clean the collector as well. I need the photos to give you more information.

Jukka

[awemawson]

"Collector" = comutator
"Coals" = carbon brushes (probably actually graphite)

[Jukka Honkanen]

Thank you Andrew for clearing that out.
Hopefully mark can fix his problem.

Jukka

[mark562]

Had a typical Monday so did not get much done to the machine today.
Was able to remove x motor from the machine again and turn ball screw by hand, table & screw move freely with no drag at all.

I am not very good with pictures but will try tomorrow. The brushes are still over .650 long so I scuffed up the ends with ScotchBrite to no avail.

I did check the voltage output of the drive boards

Z @ 14.3 volts
Y @ 27.6
X @ 77.8

Is this a correct voltage for approx. 100 ipm feed?

Thanks Mark