Polar 76EM

[Martian]

Hi all, I am having a strange problem on a Polar 76EM with LMS.
The backgauge size was out by 1,9mm. I corrected size using TAM pots as done many times before, and recalibrate after adjusting.
Size will then be correct and accurate.
But every time the gauge moves over the reference point on the scale the size will "jump" by 2mm. It is on a very specific point everytime that this happens.
After recalibrate, I can bring backgauge to 280mm, then move the gauge forward with handwheel, and as soon as it gets to 276,2mm it will suddenly change to 274,2mm.
I have not experienced this issue before so if anyone has seen this before if you can please pass on some advice.
I am thinking it must be fault on LMS but good chance it can be fault on TAM card.
Any advice would be appreciated

 

[Mathew]

Hi all, I am having a strange problem on a Polar 76EM with LMS.
The backgauge size was out by 1,9mm. I corrected size using TAM pots as done many times before, and recalibrate after adjusting.
Size will then be correct and accurate.
But every time the gauge moves over the reference point on the scale the size will "jump" by 2mm. It is on a very specific point everytime that this happens.
After recalibrate, I can bring backgauge to 280mm, then move the gauge forward with handwheel, and as soon as it gets to 276,2mm it will suddenly change to 274,2mm.
I have not experienced this issue before so if anyone has seen this before if you can please pass on some advice.
I am thinking it must be fault on LMS but good chance it can be fault on TAM card.
Any advice would be appreciated

Hello Martian,
Have you tried cleaning the brake on backaguge motor? The disk brak is a worn and torn part and due to the machine age it needs some maintenance or adjustment. Try to remove the dust by compressed air and use some brake cleaner spray for cars. It helps a lot.

Good luck

 

[Martian]

Hello Martian,
Have you tried cleaning the brake on backaguge motor? The disk brak is a worn and torn part and due to the machine age it needs some maintenance or adjustment. Try to remove the dust by compressed air and use some brake cleaner spray for cars. It helps a lot.

Good luck

Hi Mathew, yes the brake is clean and air gap is correct. It always stops on size accurately. It just has this "glitch" when passing over reference point that changes the readout size by 2mm.

 

[andy martin]

Try moving the linear scale as a whole unit forward by 2.00mm. It can be moved by loosening both ends and use adjusting screw to move forward, the 274.2 will be the calibration point set into the linear ruler

 

[Martian]

I had a chance to go have another look at it today and found that if the gauge moves forward past the reference point its perfectly on size. But if it moves to the rear the reference point LED comes on exactly 1,5mm out from the opposite direction, and then the readout size changes by 1,5mm. If I take it forward again over reference it corrects again back on size. And once on size it stays on size from the rear most point all the way to the front most point, until I take it backwards.

So I think there is a bit of movement of the sensor that is causing it. It explains this anomaly. I will have to remove it to inspect inside.

I am a bit nervous as I have never removed this sensor part before.
Can it be safely removed without removing the complete scale? Looks like the whole thing should be removed to work on it.

 

[Martian]

I am taking the scale out on Monday, so if any of you can pass along some tips or advice on removing the scale that would save me making a mistake, it would be greatly appreciated.