MAKO 46 intermittent distorted image

[Ritchiec]

Good day
I have been investigating an intermittent distorted image in the rolling direction. (not across the width).
The distortion appears to occur on the last 15 meters of AGFA HNS film. Distortion ranges from 2 -5 mm.
Across multiple rolls of film, I could rule out material to a point.

A previous technician replaced the rubber bands on bottom roller. I speculate whether these are the correct diameter and type of rubber.
Is there a specific diameter the rubber O-Rings should be?
Belts feel tight, nothing else is visibly wrong.
I have to the best of my ability cleaned the rubber bands and sprung loaded pressure roller.
I would suggest that maybe the problem is coming from the input cassette.
Is there a particular procedure for setting tension on the input cassette clutches?
Will have another look at splitting the clutches and cleaning them. All old stuff.

Can anyone offer any other suggestions please.
Colin

 

[maxon]

Colin,
O-rings should be all same size and tight enough to fit on the OD of bearings without buckling or waving around. Press each segment by hand to make sure they sit properly on their springs, all aligned and no ball bearing is seized. I have yet to see a damaged bearing on a multisegment roller myself.
Anyway. Your problem is image size lengthwise and I presume distortion means smaller image height than expected. Run a checkerboard test pattern or a 50 percent dot image and check the result - is the raster area uniform or not. Post the result.

 

[Ritchiec]

Maxon,
O-Rings seem fine, all bearings seem fine.

You are correct, distortion was length wise and intermittently shorter by varied values (smaller image height).
I changed the input cassette and used another manufacturer of film and same problem occurred (intermittently).
The customer had another scrapped machine in a storeroom, I stripped the encoder from the spare machine and installed it in this problematic machine. So far I have had consistent results that all fit.
I am not convinced yet as I started with a new roll of film and most of the time problem occurs towards the end of the roll.
I will provide feedback as I hear.

Thanks

 

[maxon]

There is a friction control built in the input cassette you can adjust to a certain degree, clean those friction pads and reassemble. The film must come out pretty tight but not 'very' tight. The shaft encoder basically never fails better don't touch it, drive motors fail quite often though either the carbon brushes or the motor encoder.
Make sure the kapton belt is clean and tensioned properly.
Clean the idler pulley and confirm the ball bearings inside are in good condition.
If daylight film roll : load the cass in complete darkness and strip the end rings before inserting the roll onto the shaft. Sometimes the flimsy end rings cause problems.

 

[Ritchiec]

Maxon,
Thank you for your advice.
I cleaned everything carefully and well. Belts appear new (I never personally changed them. I don't have a tension tool so will need to find or make one. I did check the clutches and make some small adjustments to tension as I felt they were uneven. (not yet split and cleaned)
I had noticed the ring of sticky glue on the flimsy rings and cut them off for the current roll.
I have noted all your points.
I am monitoring each day, 3 days no problems so far.