"Eight Key Points" to Achieve Perfect Printing
1. Pay Attention to Sample Sheets
① Sampling Inspection During Printing
After the start of formal printing, the preset ink supply and dampening levels determined during make-ready will change slightly. Frequent sampling and readjustment are required. When printing speed, ink supply, and dampening remain stable, perform sampling inspections at a frequency of about once every 500–1000 sheets.
② Insert Warning Strips
During formal printing, insert a narrow warning strip at the location where a malfunction occurs as a marker, so that it can be easily inspected in the post-press process.
2. Pay Attention to Changes in Dampening
① Monitor Dampening at the Start of PrintingThe dampening level set during proofing and that during formal printing will vary slightly. You must closely monitor sample sheets for ghosting or water streaks while adjusting the dampening supply.
② Monitor Dampening During the Print Run
Closely observe the effect of press body heat and workshop ventilation on dampening. For alcohol dampening, ensure the cooling system is functioning properly to control fountain solution temperature. Too little dampening causes plate scumming; too much causes ink emulsification, leading to multiple issues such as loss of gloss, paper distortion causing register errors, and delayed ink drying.
3. Pay Attention to Ink Changes
① Monitor Ink in the Ink FountainInk is dispensed through the gap between the duct roller and duct blade by its own weight. The ink level in the fountain directly affects output volume, so always maintain a proper ink level. Printing ink is thixotropic — its flowability decreases the longer it sits. Stir the ink regularly with a spatula or use an ink agitator.
② Prevent Ink from Drying on the Press
During extended stops (e.g., for meals or breaks), ink on rollers and in the fountain can dry on the surface. Use an anti-drying spray on areas where drying must be prevented.
③ Ensure Uniform Ink Distribution
Ink density will vary depending on dampening levels, ambient temperature, and press speed. Frequently compare printed sheets with the standard proof to avoid uneven ink coverage.
④ Maintain Fountain Solution pH
Adding ink additives can affect the pH of the fountain solution. A higher pH can cause plate scumming, so monitor pH levels carefully.
4. Prevent Backside Smudging
Backside smudging occurs when ink dries too slowly, the ink film is too thick, or the paper has a very smooth surface, causing wet ink from one sheet to transfer to the back of the next.
5. Prevent Ghosting
Ghosting refers to a misaligned or duplicated image printed from the same plate, visible as double or triple images on the sheet. Causes can be complex — paper, grippers, cylinders, blanket, press speed, ink tack, etc. Troubleshooting steps:① Perform double printing and check register accuracy; inspect and adjust side lay pulling force, feeder, impression wheels, and related components.
② Check blanket tension. New blankets can loosen over time; tighten gradually but avoid over-tightening.
③ Inspect cylinder packing and printing pressure.
④ Check paper quality. Poor paper, especially with wavy edges near the gripper margin, can cause ghosting.
⑤ Reduce ink tack if necessary. High tack can prevent proper paper release from the blanket, causing trailing edge instability and ghosting.
⑥ Adjust and maintain grippers regularly to ensure proper operation.
6. Check Register Accuracy
Pull out 20–30 consecutive printed sheets, align them neatly, and fan the edges slightly to inspect front lay and side lay accuracy. Perform a double-pass register check if necessary.7. Pay Attention to Other Operations
① Refill and stir ink as needed, and replenish fountain solution in time.② Remove Dirt and Debris
Ink skin, paper dust, and lint can accumulate on the plate or blanket and transfer to paper. Stop the press for cleaning unless an in-motion cleaning device is available. Never attempt to clean manually while the press is running.
③ Clean Blankets, Wipe Plates, and Apply Gum
When ink, paper dust, or spray powder builds up on the blanket and affects ink transfer, stop the press and clean the blanket. Exercise caution while wiping plates and applying gum.
④ Monitor Abnormal Machine Conditions
Pay attention to unusual sounds, heat, vibration, or smells during operation. Frequently check the ammeter and monitor the press for abnormalities.
8. Confirm the Print Quantity
Before printing ends, confirm that the total quantity matches the production order. If there is a shortage, notify production management promptly to arrange for additional printing.| 0 Comments |
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