GMI Equipment Maintenance 2 — Questions and Answers
Question 1: Which cleaning solvent is most appropriate for removing dried UV-curable ink from a flexographic printing plate?
- Isopropyl alcohol
- Acetone
- UV-compatible plate wash approved by the manufacturer (Correct answer)
- Mineral spirits
Correct answer: UV-compatible plate wash approved by the manufacturer
UV-curable inks require a UV-compatible plate wash specified by the manufacturer to avoid damaging photopolymer plate material.
Question 2: During a preventive maintenance inspection of a large-format inkjet printer, technicians discover that the encoder strip is dirty. What symptom would this most likely cause?
- Banding or misregistration in the print output (Correct answer)
- Ink starvation at the printhead
- Excessive media curl
- Clogged ink dampers
Correct answer: Banding or misregistration in the print output
A dirty encoder strip causes the carriage motor controller to misread position, resulting in banding or misregistration artifacts.
Question 3: A gravure press cylinder shows signs of pitting on the chrome layer. What is the recommended corrective action?
- Polish the cylinder with fine-grit abrasive paper
- Re-chrome and re-engrave the cylinder (Correct answer)
- Apply a chrome repair pen and continue production
- Increase doctor blade pressure to compensate
Correct answer: Re-chrome and re-engrave the cylinder
Pitting on a gravure cylinder's chrome layer compromises cell integrity and print quality, requiring re-chroming and re-engraving.
Question 4: What is the primary purpose of performing a nip pressure test on an offset printing press?
- To calibrate ink viscosity
- To ensure uniform contact between blanket and impression cylinder (Correct answer)
- To measure roller hardness durometer
- To verify ink/water balance
Correct answer: To ensure uniform contact between blanket and impression cylinder
Nip pressure tests verify that the blanket and impression cylinder make uniform contact across the full width, preventing uneven print density.
Question 5: An operator notices that the doctor blade on a flexographic press is leaving streaks. After replacing the blade, streaks persist. What should be checked next?
- Ink pH level
- Anilox roller for damage or worn cells (Correct answer)
- Plate mounting tape thickness
- Web tension settings
Correct answer: Anilox roller for damage or worn cells
Persistent streaking after doctor blade replacement typically indicates a damaged or worn anilox roller that must be inspected.
Question 6: Which maintenance task is most critical for extending the service life of an inkjet printhead?
- Running high-viscosity inks periodically
- Performing regular purge and cap cycles when idle (Correct answer)
- Increasing print speed to reduce dwell time
- Storing the printer with caps removed for airflow
Correct answer: Performing regular purge and cap cycles when idle
Regular purge and capping cycles prevent ink from drying in the nozzles, which is the leading cause of premature printhead failure.
Question 7: When lubricating press bearings during scheduled maintenance, what is the most important consideration?
- Using the highest-viscosity grease available
- Following the OEM-specified lubricant type and quantity (Correct answer)
- Applying lubricant while the press is running at full speed
- Lubricating only bearings that show visible wear
Correct answer: Following the OEM-specified lubricant type and quantity
Using OEM-specified lubricants in the correct quantities prevents over-greasing, under-greasing, and chemical incompatibility that can accelerate bearing failure.
GMI Equipment Maintenance 2
Which cleaning solvent is most appropriate for removing dried UV-curable ink from a flexographic printing plate?