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SQT 250 MS overload on startup (intermittent)

sasky115

Plastic
Joined
Mar 21, 2022
I recently started having this problem on my 1998 SQT 250 MS (T Plus) where sometimes when moving the X axis for the first time after startup it throws an overload alarm - even when moving as slowly as possible. Sometimes it does it before the machine even turns on completely, sometimes it doesn't do it at all.

Brake seems to work fine - you can unplug it from the board and hear it click and you can also see the turret drop a bit before the brake catches it when overload is triggered.

Sometimes you can hear the motor grumbling like it's struggling or maybe doing very small corrections. If you can slowly move the axis and get past this stage the machine then works fine all day. The load meter doesn't increase gradually before this happens. You can move in 0.001 mm increments and hit a spot where the motor just starts doing it and the load meter starts jumping all over the place, then you move by 0.001 mm and it stops. At rest, it usually shows 55%, after an overload and restart it goes to 33% so that's suspicious. It used to always be at around 55% (is that a bit high?).

After the overload is triggered the X axis position sometimes (I promise this is the last 'sometimes':crazy:) jumps by about 1mm randomly - that doesn't look normal either.

A Mazak tech came out, swapped X and Z drives - still the same. He's coming back next week and I'd like to find some suggestions as to what may be causing this. The most frustrating part is that it only does it after the fist startup and even then not every time. Any suggestions will be greatly appreciated.
 
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swap Z and X axis encoders. Check servo diagnostic page see if they are the same. Both should be OSE and whatever number follows.

Worse case scenario but you don't want to think about it is X axis servo motor rotor is demagnetized and behaves abnormally.
 
Thank you, we will try swapping the encoders on Thursday.
What's crazy is if it gets past the first move along X it just works all day after that.

Here you can see (and hear) it start when I reach X244.46

Here it can be heard better

And the X coordinate jumping after overload
 
I'm suspecting the encoder as well, I will try if it's any different on other turret positions.
 
unbelievable that Mitsubishi is still making money making those OSE and OSA encoders. 20 years old development and yet still brings jobs and profit to Japan ;)

next time u would be better off if you go to DIAGNOSTIC screen and look and CYCCOUNT data to see actual digits coming from encoder while manually moving axis somewhere. POSITION page says nothing at all when it comes to servo diagnostic. My bad I didn't mention it before
 
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In my case they won't be making much money except if the refurbished encoder I ordered doesn't work:scratchchin:. Thanks for the diagnostics tip, I'll add it to my troubleshooting folder, on a machine this old I may need it again soon:crazy:
 
Hi guys,
sorry that I use this page, If i'm wrong tell me.


I useed this post because I have almost the same problem in a Mazak integrex 400II mazatrol640
after summer the Z axis started to have a problem in the morning:
for one week i had to turn on two or three time the machine due to Z encoder problem,
then it stopped work definitively
so I asked mazak about that problem, he replied me to try to change the encoder from Z To Y axis (or x, but for me was more confortable the Y axis)
I had not told him but I had done it before...:D ; so the error moved form Z axis to Y axis and I decided to buy the encoder and changed it,
but when I tried with a new encoder mounted in Z axis the machine put out the error in Y axis....
then I excanged again the encoders and i had the Error in a Y axis
how is possible...I started with a one damaged encoder and now i have two damaged encoder?

noname777 wrote that there is a procedure to chek the signals... is possible use it?​

Any suggestions will be greatly appreciated.
 
My old encoder that was causing trouble did have a small piece of dirt or something on the encoder disk and a faulty capacitor. An electronics-savvy friend of mine cleaned it and replaced the capacitor but I haven't tested it as I don't want to mess with the machine just for that. Also, the encoder must not lose its reference point so you have to be careful when removing and installing it. That's all I can say about it, I don't really know much about it...
 
Problem solved!!!!:willy_nilly::willy_nilly::willy_nilly::willy_nilly:
I don't know how is possible but I had to change two encoders...fortunately i fuond some of them new on ebay
mitsubishi encoder OSE105S2 from mazak 1800€
same encoder from china (also new) €300/400 but didn't choose this way because it needed more than 30 days for shipment and customs...
same encoder from european seller on ebay 800€

I report my case for some other user :
in the first situation the machine started to have a problem in the morning:
for one week I had to turn on two or three time the machine due to Z encoder problem,

alarm 22 encoder malfuncion (2,0,&0043)
and sometimes
alarm 24 overload (2,0,&0058)
So, my machine use the same encoder for the z axis, y axis and z axis, then I decided to excange the encoder from Z to Y axis
Now the Z axis started to go and the problem moved to Y axis
alarm 22 encoder malfuncion (4,0,&0043)
now I moved the good encoder to the Y axis again and I bought a new encoder for Z axis.
when I received the new encoder I placed it on a Z axis but stangely the encoder of Y axis started to give me the same errors...
alarm 22 encoder malfuncion (4,0,&0043)
I Bought another encoder and I replaced it also for the Y axis...
now the machine run normally...

at the end: I heard the is necessary put in fase the new encoder with the motor? is true?msg1077314169-2510.jpgmsg1077314169-2507.jpgmsg1077314169-2509.jpgmsg1077314169-2508.jpg
 








 
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