[cfranko]

I'm not really sure if this is the right place for this post, so mods please move if I put it in the wrong forum

The problem is with a Harrison Alpha 1550 S.

Everything works fine, except for when cutting certain threads in 'alpha' mode.

After a few passes, I get this '410 servo alarm: z axis excess error'
(this happens even with no material)

From looking through the manual, this is caused by an excessive deviation from the expected position.

This is controlled by parameter 1829 (current value is 500)

When I go to system parameters, how do I change them? I've tried entering '600' and hitting 'input', but I get a message saying 'wrong mode'


How am I supposed to edit these values? Any help with properly resolving the issue would also be greatly appreciated

Thank you

[underthetire]

you need to be in MDI mode, can't remember if the Harrison had an MDI mode. If not, try to press emergency stop and change the parameter. If this is a recent problem with the machine, I would check mechanical binding and lube before I changed a parameter though. Sounds to me like the carriage may be sticking.

[cfranko]

you need to be in MDI mode, can't remember if the Harrison had an MDI mode. If not, try to press emergency stop and change the parameter. If this is a recent problem with the machine, I would check mechanical binding and lube before I changed a parameter though. Sounds to me like the carriage may be sticking.

I'm reluctant to think that it is a mechanical problem since this doesn't occur when performing anything outside of cutting threads, and even when cutting threads, there are only certain arrangements (pitches/diameters) that set the alarm off.

I'll look into the MDI mode, and try it with the estop

Thank you

[cnc2149]

You'll also need to set the Parameter Write Enable bit to 1 in order to change a CNC parameter. On most machines, you press the OFFSET/SETTING hard key and set the Parameter Write Enable = 1 on the SETTINGS page. However, some (or maybe all) Harrison Alphas don't use the FANUC MDI keyboard so you can't get to the normal pages easily. Below is the procedure to turn Parameter Write Enable bit On with some Alphas.

"Ensure that the machine is in Emergency Stop. Slide the orange DIP switch on the A3 Spindle Load Monitoring board to the right (ensure that all the others are in the left hand position) and press the black pushbutton beneath it. Slide the orange DIP switch back to the left. Press the SETTINGS softkey on the apron panel and then press 1 and then ENTER."

With regard to your actual problem, the 410 is an Excess Error Condition while Stopped. If often fools you because you can get the problem in the middle of running a part. I've seen this occur when an axis has too much overshoot. The CNC uses the position error specified in par 1828 when it is commanded to move. At the end of the block, the axis is no longer commanded to move so it uses the error zone specified in par 1829. If it overshoots that zone, alarm 410 occurs. The reason you may be getting this in threading is that there are separate ACC/DEC parameters that apply only to threading moves. I suggest reviewing all the 1600 series ACC/DEC parameters with a master list (or contact your Harrison distributor if you don't have a good backup). btw: I have a parameter list from some type of Harrison Alpha lathe that calls for 1829 = 600 for both axes.

Failing that, I'd set par 3111.1 = 1 to enable the servo set/tune pages on the SYSTEM hard key. Then go to the Servo Tune page and see what the position error looks like at different points in the cycle (and even at standstill). Running the part program in Single Block will sometimes show you where the problem area exists. May not be able to do this if you're running a canned cycle.

[cfranko]

Here's what I got back from Harrison

Hi Chris.
You need to be in MDI mode in CNC mode. You also need to set PWE in your SETTING (HANDY) screen to allow changes. 500 is the normal setting. The alarm basically means that the slide cannot get to where it is supposed to be in the allowed time (lag) and is usually caused by mechanical restriction or something like that. It may be worth contacting our applications dept. with a copy of the program if the m/c functions alright normally.

[cnc2149]

It is true that the 410 alarm can be caused by a mechanical restriction (e.g. faulty brake, excess friction, etc. ); however, you only see the problem during threadcutting so that's why I said to check the acc/dec settings. There are probably multiple configurations of alpha lathes using various generations of FANUC CNC controls, so go with their advice on the recommended parameter values and the procedure to set the PWE bit. It still may be worth looking at the Servo Lag in DGN 300 (if this is a Series 18, 20, 21 CNC) in order to see what it looks like at stop and between moves when running Single Block.

[cfranko]

for anyone looking at this in the future, this is from someone else at harrison:

To change parameters you need to turn parameter write on.
This is on the offset setting pages.
Push offset setting hard key.
Then push setting soft key ( the rubber keys under the display).
Push MDI hard key.
Move cursor to parameter write then type in 1 input.
Ps 100 alarm will show up that is normal.
When you're done then you have to put parameter write back to = 0.