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Reassembling Siemens AC servo - aligning sensors

Mud

Diamond
Joined
May 20, 2002
Location
South Central PA
I'm repairing a broken 1FT5076 Siemens servo. The mounting end bell was broken, apparently by being hit with a forklift. I disassembled the servo,the rest of the motor seems fine, armature straight, etc, except for the connection junction box and connectors.

I found a donor servo of the same size to rob the end bell and junction box from from. What is required to put it back together properly? It appears the sensor plate in the end needs to be timed to the armature - is it possible to do that without sending it to a service facility with a test bench?
 
Are there any marks on the sensor plate and the housing that may be related?

If there are you might be able to put a low (less than 5) volts on a known good motor input leads and see where the armature lands. You may have to try a couple different combo's. If some thing looks like it lines up you can use that as a reference to the problem motor.

Ed.
 
Are there any marks on the sensor plate and the housing that may be related?
When I align the marks from the clamping screws with the screw holes, there is a fine blue line that lines up with the center of a casting boss, but no matching line on the boss. The screw marks are indistinct, they look like they were adjusted and moved possibly 2° or so.

If there are you might be able to put a low (less than 5) volts on a known good motor input leads and see where the armature lands. You may have to try a couple different combo's. If some thing looks like it lines up you can use that as a reference to the problem motor.

Ed.
I have another identical servo on another axis that is undamaged, and presumed good. Unfortunately I'm so illiterate on this subject I don't understand what you mean by see where the armature lands, or try a couple combos or looks like it lines up - - :o But thanks!
 
I'm repairing a broken 1FT5076 Siemens servo. The mounting end bell was broken, apparently by being hit with a forklift. I disassembled the servo,the rest of the motor seems fine, armature straight, etc, except for the connection junction box and connectors.

I found a donor servo of the same size to rob the end bell and junction box from from. What is required to put it back together properly? It appears the sensor plate in the end needs to be timed to the armature - is it possible to do that without sending it to a service facility with a test bench?

If you have any flexibility as to how it is coupled, ISTR that Servo-Tek lists a coupler that is meant to be field-adjusted for "timing" resolvers to whatever shares the shaft.

That item may be bought-in rather than of their own make, so they are around, somewhere.

That, of course, presumes there is a way to tell if it is properly timed once it is back in circuit by use of the rest of the machine rather than test gear.

You are probably already aware that Siemens are not famous for 'sharing' information willingly, so the other option is not so much whether you have the goods to perform an accurate static alignment, but rather "to what?".
 
Not that - the machine has glass scales for positioning. I believe the hall-effect sensors are for rpm feedback and etc. to the drives. The parts servo had the plate marked and the screws sealed against tampering, so it must be something critical to motor functioning.
 
Not that - the machine has glass scales for positioning. I believe the hall-effect sensors are for rpm feedback and etc. to the drives. The parts servo had the plate marked and the screws sealed against tampering, so it must be something critical to motor functioning.

If position is managed independently, and this critter is ONLY for RPM feedback?

Then adjustment and fixing same soundly may have been only to insure the 'sweet spot' in spacing gap did not shift and affect signal strength or linearity over the RPM operating range for its expected lifetime, nor the slightest of misalignment impose undue wear on delicate bearings.

If so, 'close' should be good enough.

I am not he who can assure that it IS so, however.
 
Many AC servos use an encoder for commutation. They have to be timed using an oscilloscope and the requisite knowledge.
 
Do you have pics of the sensor plate? If it uses encoder commutation it is beyond my knowledge but if the sensor plate is for Hall sensors it may be possible.

Ed.
 
This is how it was positioned when I took it apart. I can't be sure it wasn't moved before it got to me.

20170223_104234B.jpg

This is where the mark was positioned. The marks from the clamp screws don't show up well in the photo, they are barely visible in person.

20170223_104721B.jpg

20170223_113449B.jpg

If the position is off slightly, what will happen when power is applied?
 
If the position is off slightly, what will happen when power is applied?

Wes may have done this - all I know is the theory. "Slightly" enough, you'd barely notice. A bit more, both power delivered, and any commanded 'holding' at rest - if even it has such - are weaker.

More yet, it 'cogs' noticeably.

You are probably going to be close enough to not harm it, so given the forklift-damage, and bringing it back from 'the dead', I'd be inclined to just give it your best shot, button it up, and try it out in live use.

Might not get 100.00% lucky, but Wot the hey, 98% close - or better - may be good enough to get it back to earning a crust at a lot less cost than sending it off to Siemens.
 








 
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