Screen Printing Trouble Shooting

TROUBLESHOOTING TYPICAL SCREEN PRINTING PROBLEMS

 The follo$ing are suggestions for common screen printing printing problems that can occur $ith most models. These are geared to$ard using %& cure inks. 'or more suggestions or application uestions it is best to call ou ink supplier or manufacturer. manufacturer.

Problem

Cause

Root Cause

Trouble Shoot

Bubbling Small air bubbles on printed Ink too thick (viscous) solids.

 Thin out ink.

Ink contains bubbles from high speed mi#ing. *llo$ bubbles time to disperse or reduce mi#er speed. Reduce sueegee speed. Printing speed too fast.  Too  Too much ink deposited. deposited.

%se harder sueegee to transfer less ink.

Contamination +on!inked +on!inked spots in image area.

,int-dust in image area of screen.

Clean Screen Increase humidit level. Clean $ork area regularl.

Contaminated substrate.

*void handling substrate in area to be printed. Take steps to remove dust ust prior to printing.

Pinholes Ink spots in non!image area. 0oles in non!image area of screen.

Spot out $ith blockout or tape or remake stencil.

Ink leaks around image.

'oreign 'oreign material under stencil near image edge.

Clean underside of screen.

Ink too thin.

Sti"en ink or remi#.

Ink Spreading  Thickening of image unsharp edges ink spreading around image edges.

Ink too thin.

Sti"en or remi# ink

5#cessive 6ood coat pressure pushes ink through screen.

'lood bar should not be touching the screen during the 6ood ccle.

Sueegee pro1le too rounded. Sharpen sueegee.  Too little snap!o".

Increase o"!contact distance or retention-remake screen.

 Too much snap!o". Static7 press sheet does not completel drop o" screen.

Reduce o"!contact distance. *dd anti!static agent to ink. 2round the table bed. Incorporate static eliminators. 8ask out non!image area $ith paper on the underside of screen.

Blur-2hosting 3ouble edges at edges. Image blurred and-or distorted.

Insu4cient snap!o". Increase o"!contact distance Press sheet sticks to mesh due Reduce speed. Increase vacuum. to static. Increase snap!o". *dd anti!static agent to ink. 2round the table bed. Incorporate static eliminators. 8ask out non!image area $ith paper on the underside of screen. Ink contains bubbles from high *llo$ bubbles time to disperse or speed mi#ing. reduce mi#er speed. Print ing s peed t oo fast .

Reduce sueegee speed.

 Too much ink deposited.

%se harder sueegee to transfer less ink.

Streaks 3ensit di"erence across image in direction of printing stroke.

+ick in sueegee blade.

Sharpen or replace blade.

'ault-nick on 6ood-coater blade.

Smooth or replace 6ood bar.

+ick-scratch on press bed.

Smooth out 1ll in or replace 6ood bar.

* run in screen fabric. ink not throughl mi#ed. Ink trailing from sueegee.

Re!make stencil on ne$ f abric. Screen out solids and re!mi#. *dust viscosit.

%neven sueegee pressure.

*dust pressure relative to substrate.

Poor stock.

Change stock. Print clear!coat onto stock 1rst.

Insu4cient ink 1lm.

Print thicker ink 1lm. %se coaser mesh.

Ink too thin-transparent.

Increase pigmentation of ink.

Ink dring in. Ink too thick.

9ash out stencil. Thin ink $ith solvent.

0igh ambient temperature.

Thin ink $ith retarder.

Blunt or soft rubber on sueegee.

%se sharper or harder sueegee.

8ottling *reas of di"erential ink absorption b substrate.

Ink 3ring in Screen Selective parts of image areas.

Ink Coverage 'ailure Second color doesn:t completel cover 1rst (second color refusal).

 Too much silicone in 1rst ink do$n.

Change ink.

Second color too thick. Thin-reduce ink. Solvent release from 1rst color *llo$ 1rst color to dr properl through second.