GMI Troubleshooting & Problem Resolution 5

Question 1

A lithographic press is showing excessive plate wear after only 50,000 impressions on what should be a 1,000,000-impression run. The most likely cause is:

Accepted Answer

Fountain solution pH too low, causing acidic etching of the plate surface

Answer

Fountain solution that is too acidic attacks and erodes the plate's image-bearing surface, drastically shortening plate life.

Question 2

A wide-format print shows color shifts between passes on a multi-pass inkjet system. The technician has already confirmed ink density and substrate feed accuracy. The next item to check is:

Accepted Answer

Print head alignment and bi-directional calibration between forward and return passes

Answer

Color banding between passes on a multi-pass inkjet is commonly caused by misaligned print heads or incorrect bi-directional calibration causing offset dot placement.

Question 3

After a substrate change to a coated board with a higher surface smoothness, a flexo press shows fill-in of fine reverses. The appropriate corrective action is:

Accepted Answer

Reduce impression pressure and switch to a lower-volume anilox roller

Answer

Smoother substrates require less impression pressure and lower anilox volume to prevent ink from filling in fine reverse details due to reduced mechanical resistance.

Question 4

A quality control technician finds that measured ΔE values between proof and press are consistently high on cyan solids but acceptable on all other colors. The focused diagnostic step is to:

Accepted Answer

Check the cyan ink formulation against the target standard and verify the cyan curve in the ICC profile

Answer

A color deviation isolated to one channel points to either an ink formulation mismatch or an error in that channel's ICC profile curve, requiring targeted investigation of the cyan channel only.

Question 5

A screen printer is experiencing ink bleeding under the stencil edge, causing loss of fine detail. After confirming ink viscosity is correct, what should be checked next?

Accepted Answer

Mesh tension — if too low, the mesh does not snap off the substrate cleanly

Answer

Low mesh tension prevents proper snap-off, keeping the mesh in contact with the substrate longer and allowing ink to bleed past the stencil edge.

(GMI) Graphic Measures International Certification Practice Test

(GMI) Graphic Measures International Certification Practice Test

GMI Troubleshooting & Problem Resolution 5