Troubleshooting 2

TROUBLESHOOTING TYPICAL SCREEN PRINTING PROBLEMS

Streaks


Density difference across image in direction of printing stroke. Nick in squeegee blade. Sharpen or replace blade.

Fault/nick on flood/coater blade. Smooth or replace flood bar.

Nick/scratch on press bed. Smooth out fill in or replace flood bar.

A run in screen fabric. Re-make stencil on new fabric.

ink not throughly mixed. Screen out solids and re-mix.

Ink trailing from squeegee. Adjust viscosity.

Uneven squeegee pressure. Adjust pressure relative to substrate.

Mottling


Areas of differential ink absorption by substrate. Poor stock. Change stock. Print clear-coat onto stock first.

Insufficient ink film. Print thicker ink film. Use coaser mesh.

Ink too thin/transparent. Increase pigmentation of ink.

Ink Drying in Screen


Selective parts of image areas. Ink drying in. Ink too thick. Wash out stencil. Thin ink with solvent.

High ambient temperature. Thin ink with retarder.

Blunt or soft rubber on squeegee. Use sharper or harder squeegee.

Ink Coverage Failure


Second color doesn’t completely cover first (second color refusal). Too much silicone in first ink down. Change ink.

Second color too thick. Thin/reduce ink.

Solvent release from first color through second. Allow first color to dry properly.