Troubleshooting & Problem Resolution Flashcards

A gravure print of a fine-screen tint shows missing dots in highlight areas on every other copy. The most likely cause is:

Answer: Worn or damaged doctor blade leaving residual ink in cells unevenly

A worn doctor blade can skip, leaving uneven ink in shallow highlight cells and causing every-other-copy dot skipping as the cylinder rotation pattern aligns.

After replacing a printing plate, a pressman notices that register is off on the first unit only. The corrective action is to:

Answer: Adjust the plate's lateral and circumferential register on that unit

When only one unit is out of register after a plate change, the plate itself was mounted incorrectly and requires lateral/circumferential adjustment on that unit alone.

A print shop receives customer artwork with text set in a light-weight sans-serif font at 6 pt. The most likely press-related problem is:

Answer: Ink spread causing fine strokes to fill in and become unreadable

Very fine strokes in small text are highly susceptible to ink spread (dot gain), causing hairline strokes to fill in and become unreadable on press.

When measuring a printed neutral gray patch, a spectrophotometer reads a* = +3 and b* = −4. This indicates the gray has a:

Answer: Slight green cast with a blue shift

In CIELAB, a positive a* value means red shift and negative means green; a negative b* means blue shift — so a*=+3 and b*=−4 represents a slight green-blue cast.

A flexo press operator notices that solid ink density is acceptable but halftone midtones are printing too dark. The most targeted correction is to:

Answer: Reduce plate impression pressure to lower mechanical dot gain

Excessive mechanical dot gain in midtones without affecting solid density points to too much impression pressure spreading halftone dots.

A batch of printed labels is returned because the bar codes fail to scan. The labels measure within density specification. What should be investigated?

Answer: Bar width accuracy and print contrast signal (PCS) between bars and spaces

Scanners read bar codes based on the contrast and dimensional accuracy of bars and spaces; even spec-density bars fail if widths are wrong or PCS is below scanner threshold.

A screen printing shop finds that a fine-mesh screen is breaking down prematurely during long runs. The most likely cause is:

Answer: Under-exposure of the photopolymer emulsion

Under-exposed emulsion has not fully cross-linked, making it mechanically weak and prone to breakdown under squeegee pressure during long production runs.