Encoder Strip, Linear Scale and Banding: Diagnosis and Replacement

When a printer suddenly starts banding, drifting lines or stops mid-job with a position error, the encoder strip is one of the first places to look – and one of the cheapest to fix. It is also a part that operators damage by cleaning it the wrong way.

What the Encoder Strip Does

The encoder strip is a transparent strip printed with very fine graduations that runs the width of the machine. A sensor on the carriage reads those graduations as the carriage moves, giving the printer a continuous, precise position reading.

Without an accurate position reading, the printer cannot place dots where the RIP told it to. The result is not a random fault – it is a systematic one, which is exactly why it looks like banding.

Symptoms of a Failing Encoder Strip

• Sudden banding that appears overnight on a machine that was printing perfectly.
• Vertical lines or a random horizontal offset in the middle of a print.
• Banding that changes position from print to print rather than staying in the same place.
• Position or encoder error codes, or the carriage stopping mid-job.
• Image stretched or compressed in the carriage direction.

Compare this with a nozzle problem, which produces banding that stays in the same place and follows the head.

Ten-Minute Diagnosis

1. Clean the strip first. Use a dry lint-free swab or wipe, and wipe gently along the strip. Do not use solvent-heavy cleaners, and do not scrub. Ink mist and dust are a common cause and cleaning often fixes the fault completely.
2. Inspect it against the light. Scratches, creases and worn areas where the carriage rests are permanent – the strip has to be replaced.
3. Check the sensor. The encoder sensor head accumulates ink mist. Clean it and check the connector.
4. Check the tension and routing. A strip that is loose, twisted, or sitting off its pulley gives an unstable reading.
5. Print a test pattern. If cleaning fixed nothing and the strip is visibly damaged, replace it.

Replacing the Strip

1. Note the orientation. The graduations face a specific way. On most machines the printed side faces the sensor; get it backwards and the printer will not read it at all. Photograph the old strip before removing it.
2. Do not touch the graduated surface with bare fingers. Skin oil is enough to cause misreads.
3. Route it exactly as the old one was routed – over the same pulleys, through the same guides, and connected to the same tension spring.
4. Re-tension gently. Enough to remove slack, not enough to stretch the strip.
5. Run the encoder check or carriage calibration the service manual specifies, then print a test pattern before production.

Prevention

Fitting a cap top that seals well and keeping the wiper clean reduces the ink mist that ends up on the strip. A monthly dry wipe takes a minute and is far cheaper than a mid-job failure.

FAQ

Can I clean the encoder strip with alcohol?

Use the mildest option that works – a dry or very lightly dampened lint-free swab. Aggressive solvents and repeated scrubbing can remove the graduations, which turns a cleaning job into a replacement job.

How often should the encoder strip be replaced?

There is no fixed interval. Replace it when it is scratched, creased or worn through, or when cleaning no longer resolves position faults.

Will a bad encoder strip damage the printhead?

Not directly, but a carriage that positions badly is more likely to strike lifted media. Fix the strip before it takes the head with it.

Encoder Strips and Related Parts

We stock encoder strips, sensors and the motors and drive parts that sit around them, for Mimaki, Roland, Mutoh and Epson wide format machines. Send your model through the contact form and we will identify the correct part.