| Problem |
Cause |
Corrective Solution |
Area of Weak Print
(appears as broken, weak or area of non print) |
Improper bearer pressure. Packing damaged. Blanket smash. Insufficient packing or back cylinder pressure. Low spot in cylinder. Plate blinding. |
Check for smashed area replace blanket & or packing. Also try adjusting back cylinder setting. Check blanket height, repack or replace. Press condition ... over pack or spot pack. Check plate to blanket squeeze remake plate. |
Embossed Blanket
(previous job shows in print due to image retained in blanket) |
Blanket swollen due to excessive pressure, very high ink tack, or lack of cleaning with proper blanket wash Solvents in ink may affect blanket (UV inks for example). |
Check blanket thickness and packing. Use quality blanket wash and clean blankets on a regular basis. If blanket is old, change to a new blanket, or one that works better with your inks. UV inks and washes can often swell blankets. If using UV ink, try a UV compatible blanket. |
Ghosting
(similar to Embossing, ghost of image appears in print) |
Ink form rollers starved for ink. Job layout causing problem. Ink/water balance issue. |
Not a blanket issue. Check roller settings, run a thicker ink film with minimum of water. Job layout often contributes to the problem...change direction of run or general layout if possible. |
Overall Light Print
(lack of desired ink density) |
Lack of pressure in nip between plate & blanket or blanket and
impression cylinder or blanket to blanket on webs. Underpacked condition. |
Check for proper blanket packing & tension. Insure adequate plate to blanket squeeze and blanket to impression squeeze. Blanket surface could be glazed, so check for shiny spots (glaze) on blanket surface. Clean or replace blanket as necessary. |
Loss of print at gap
(cannot print full image area typically on a web press) |
Blanket over-torqued, packing incorrect, Packing slipped. Press out
of phase (timing issue). |
Insure proper packing of blanket and use torque wrench to tighten to press manufacturer specs. Check torque wrenches for accuracy. Some print length problems are due to cylinders being out of phase. check cylinder timing to print length. |
Loss of Print
Continual Need to Repack (loss of print sharpness in overall print) |
Probably caused by blanket sinking or elongating under pressure Bearers heating up can cause loss of pressure often incorrectly blamed on the blanket. |
Be sure blanket installed so fabric stripe goes around the cylinder. Use a torque wrench so blanket is not overtightened. Clean bearers and perhaps change bearer wipes. If problem persists, change blanket and/or blanket brand. Blanket is defective. |
Loss of Print
Low Spot (localized loss of print due to damage) |
Blanket probably smashed. |
Damage to blanket by paper or foreign object creates a low spot. While blanket could be repacked, it is often more cost effective to simply replace the blanket. A blanket rejuvenator could be used short term to get a short run job finished. |
Muddy, Filled In Print
(dots enlarged and halftones plugged and overly dark) |
Too much plate to blanket squeeze. Excessive blanket to impression
squeeze. Blanket piled or swollen. Excess ink or emulsified ink. Incorrect form roller settings. |
Check packing adjust to press specs or measured .004 to .005 squeeze for compressible blanket. Back off impressions cylinder and set for best print quality. Check roller settings, reset if necessary. Clean blanket...be sure solvent compatible with blanket to prevent rubber swelling. Reduce ink, adjust ink & water balance. |
Piling
Ink (ink builds up on plate or blanket) |
Most frequently an ink problem (ink too short and not water repellent), fountain solution pH or conductivity wrong, or rollers set wrong & heat building up. Blanket underpacked. |
The blanket is least likely to be the cause of ink piling even though the ink piles on the blanket. If blanket related, it is generally due to insufficient packing. Verify proper packing and nip pressures. Check ink feed , roller settings and set to minimum, check fountain solution pH & conductivity. |
| Problem |
Cause |
Corrective Solution |
Piling
Paper (paper fibers or paper coating pile on blanket) |
Blanket tacky or low blanket to impressions squeeze, paper quality. Poor ink water balance, High ink tack. |
Try a new blanket. If problem persists, a different blanket may be required. Verify proper blanket packing and adequate squeeze for ink transfer to paper. Increase ink supply, reduce ink tack. |
Plate Blinding
(loss of image from plate so it will not transfer image) |
Excess plate to blanket squeeze, blanket surface too hard, improper pH, improper form roller settings, or bad or improperly made plate. |
Adjust plate to blanket squeeze to a measured .004 to .005. If blanket old and hard to the touch, try a new blanket. Compressible blankets will give more packing latitude. Check pH and conductivity. |
Paper Edge Cutting
(paper edge is cutting blanket surface |
Sharp edges of paper stock cutting blanket surface due to rough trim,
coating accumulation, or excess nip pressure. |
Use a compressible blanket. Compressible blankets have greater packing latitude. If from piling, clean blanket more often. Change packing size so it is smaller than sheet size to lessen pressure at stock edges. Use minimum back cylinder pressure. |
Paper Does Not Release Evenly
(release issues seen as wavy printed sheets; poor sheet release may be audible during press run) |
Excessive nip pressure, high tack inks. Tacky blanket from attack by harsh solvents. |
Proper blanket cleaning with low volatile blanket wash helps prevent release issues due to tacky blanket. Avoid regular use of harsh solvents or blanket rejuvenators. Insure blanket packing and impression settings are correct. Talk to ink manufacturer to insure proper formulation for your press and type work. |
Pinholes in Blanket
(small holes in blanket surface cause holes in print) |
Blanket defect, particles coming out of blanket surface |
Make sure holes in surface rubber rather than a hickey on blanket or plate surface. Replace blanket and save for evaluation and replacement by manufacturer. |
Registration
Circumfrential (colors not registering in the direction of paper feed) |
Loose blanket or improper packing from one unit to the next. Stock feed problems Excessive moisture gain between printing units Erratic infeed tension. Unstable stock. |
Insure blankets properly torqued. check proper packing of plate and blanket between units where fit is an issue. Reduce water feed or change stock if absorbing excess water is changing stock dimension. Check infeed rolls set properly. Verify plate installed and bent properly. |
Registration
Lateral (colors do not register across sheet or web at 90 degrees to direction of paper feed) |
Often relates to excess water absorption by paper, excess nip pressure causes paper to spread, paper roll tensioned poorly by mill Press infeed tension erratic. |
First check nip pressure by verifying blanket packing. Use less packing if overpacked. Try reducing water to minimize absorption. Adjust press infeed tension settings May require paper change. Discuss with paper supplier. |
Slurred Print
(dots elongated in direction of travel through the press |
Excess nip pressure at plate & blanket or blanket & impression.
Loose blanket. Improper form roller settings. Improper ink water balance. |
Check blanket packing and plate packing. On sheetfed or business forms web, check squeeze to impression cylinder... adjust. Check torque of blanket lock up. Many times too much ink or improper ink water balance is the problem. Check ink train settings. |
Streaking
(horizontal streaks in print, most noticeable in halftones) |
Press condition known as gear streaks, can be made worse by excess bearer pressure or plate to blanket squeeze, ink form rolls set wrong or too hard. |
Older or worn press gears can cause streaking. Compressible blankets can help minimize this. Other factors can include blanket or plate overpacked. Insure proper nip pressure between plate and blanket. Check bearer pressures... adjust. Adjust form rollers, replace if durometer too hard. |
