Why is a printer double printing, ghosting, or blurry - and how do you fix it?
Double printing (horizontal or vertical ghosting) is typically caused by a dirty or slipping Y-axis optical encoder strip, uncalibrated bi-directional firing delay in RIP software, or Z-axis sensor oscillation on uneven walls.
Doubled text, shadow lines, or stepped registration in a vertical wall print indicate a synchronization mismatch between mechanical carriage travel and nozzle firing timing. Common diagnostic checks include: (1) **Inspect and Clean the Optical Encoder Strip**: Ink mist, drywall dust, or skin oil on the transparent encoder film causes missed position ticks - clean gently with lint-free foam swabs and 99% isopropyl alcohol (avoid acetone or harsh solvents that strip etched lines); (2) **Recalibrate Bi-Directional & Step Offsets**: Print the RIP software’s bi-directional vernier chart and adjust left-to-right firing delay in microseconds until overlapping lines align into a single hairline, or test Uni-Directional print mode to isolate timing vs mechanical backlash; (3) **Check Belt Tension & Z-Axis Ultrasonic Sensors**: Loose carriage belts, unlevel floor tracks, or ultrasonic sensor bounce over deep brick mortar or electrical outlets can shift print distance mid-pass.
- Inspect the vertical/horizontal optical encoder strip for dust or ink mist and clean gently with 99% isopropyl alcohol.
- Run a bi-directional alignment test chart in your RIP software and compare against Uni-Directional output.
- Check carriage timing belt tension and stabilize Z-axis sensor tracking over recessed outlets or mortar joints.
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