GMI Troubleshooting & Problem Resolution 2 — Questions and Answers
Question 1: A print job shows banding artifacts running perpendicular to the paper feed direction. What is the most likely cause?
- Clogged or misfiring inkjet nozzles (Correct answer)
- Incorrect ICC profile selected
- Paper grain direction mismatch
- Insufficient ink viscosity
Correct answer: Clogged or misfiring inkjet nozzles
Horizontal banding perpendicular to paper travel is a classic symptom of clogged or intermittently firing inkjet nozzles that skip rows of dots.
Question 2: A customer reports that printed Pantone colors look correct on press but shift significantly when the job is laminated. What should be investigated first?
- The laminate's optical brightener content and UV absorption (Correct answer)
- The plate exposure calibration
- The anilox roller cell volume
- The dryer temperature settings
Correct answer: The laminate's optical brightener content and UV absorption
Laminates containing optical brighteners or UV-absorbing layers alter perceived color, particularly shifting neutrals and cool tones after application.
Question 3: When troubleshooting a flexographic press showing inconsistent dot gain across the web width, the technician should first check:
- Impression pressure uniformity across the cylinder (Correct answer)
- Ink pH levels in the fountain
- Doctor blade angle on the anilox
- Substrate moisture content
Correct answer: Impression pressure uniformity across the cylinder
Uneven impression pressure across the cylinder width creates differential dot spreading, producing variable dot gain from edge to edge.
Question 4: Color proofs consistently appear more saturated than the final press sheet. After confirming the proof substrate is correct, what is the next diagnostic step?
- Verify the press ICC profile matches current press conditions (Correct answer)
- Increase ink film thickness on press
- Reduce the proof resolution setting
- Replace the spectrophotometer calibration tile
Correct answer: Verify the press ICC profile matches current press conditions
A press ICC profile that was built under different conditions will cause systematic mismatches between proof predictions and actual press output.
Question 5: A UV ink shows poor adhesion on a flexible plastic substrate even after curing. Which corrective action is most appropriate?
- Apply corona or flame surface treatment to the substrate before printing (Correct answer)
- Increase UV lamp intensity to 100%
- Reduce ink viscosity with solvent
- Switch to a higher-opacity ink formulation
Correct answer: Apply corona or flame surface treatment to the substrate before printing
Flexible plastic substrates require corona or flame treatment to raise surface energy so UV inks can wet out and bond properly.
Question 6: During prepress, a PDF file intended for four-color offset printing contains RGB images that were not converted. What is the most critical problem this causes?
- Unpredictable color shifts because the RIP must convert RGB on the fly using a generic profile (Correct answer)
- The file will be rejected by all modern RIPs
- Ink coverage will exceed 400% total area coverage
- Spot colors will not separate correctly
Correct answer: Unpredictable color shifts because the RIP must convert RGB on the fly using a generic profile
When RGB images are converted by a RIP using a generic or mismatched profile, the resulting CMYK values are unpredictable and differ from an intentional conversion.
Question 7: A wide-format inkjet printer produces a gradient that posterizes (shows visible steps) in smooth shadow areas. Which setting is most likely at fault?
- Insufficient bit depth in the output file or RIP processing pipeline (Correct answer)
- Head height set too low above the media
- Ink density set above the linearization limit
- Print speed too high for the ink type
Correct answer: Insufficient bit depth in the output file or RIP processing pipeline
Posterization in smooth gradients results from insufficient bit depth, meaning the number of tonal steps available is too low to render smooth transitions.
GMI Troubleshooting & Problem Resolution 2
A print job shows banding artifacts running perpendicular to the paper feed direction.
What is the most likely cause?