Troubleshooting Guide - Pressroom UV
On Press Issue: Dot Gain
Potential Causes
Too much pressure from roller to plate, plate to blanket or blanket to impression cylinder
Solution: If the dots on the plate are square but on the sheet they are round, there is excessive pressure. Check setting and correct to proper pressure. Use a roller stripe gauge. Set form rollers to oscillators before setting to plates.
Double or slurred dots
Solution: Adjust plate to blanket pressure. Make sure blanket is secure. Check press for roller slippage and mechanical instability at high speeds.
Ink viscocity is too low
Solution: Ink may need to be higher in vescocity.
Ink is over-emulsified, taking on too much water
Solution: Clean up the press including all rollers. Re-ink and lower the water settings by approximately 25%. Start running dry and then increase the water settings.
Ink film is too heavy/thick
Solution: Lower the ink settings if possible. Check the roller settings (stripe). May need to increase the strength of the ink.
Type of blanket
Solution: Change type of blanket.
Paper/stock characteristics
Solution: Change paper/stock.
Improper plate dot size
Solution: Check plate exposure scales (stouffer scale). Read plates with a CCDot meter. Make sure plotting curves on CTP plates have not changed.
Fountain solution is too warm
Solution: Monitor pan temperature, maintain 62-65 degrees F.
Press temperature is too warm
Solution: Check chilled vibrator roller temperature and adjust.
