Screen E-Book (.PDF) - MacDermid Autotype

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Dark spots / HickiesDescriptionDark spots in the half tone area usually0.5-2mm in diameter.CauseThe cause is dust or debris on the substratelifting the stencil away from it. Thisallows the ink to flood under the stencilcausing a dark spot. The dust may stay attachedto the substrate or it may then stickto the stencil causing the same blemishover many prints.Under magnification it can be seen that the ink is severely undercutting the stencil.SolutionThe immediate solution is to wash up thestencil and clean subsequent sheets ofsubstrate using antistatic wipes or tackyrollers.In the long term antistatic and clean roommeasures can be taken.There is still evidence of the intended image within the blemish which means thatit is not a pin hole in the stencil.128
StaticPresence of static will cause more dust tobe attracted to surfaces. Static is producedin 3 ways.1. Separation2. Friction3. InductionThe simple act of removing a sheet of filmfrom a stack produces static by separationand friction.Antistatic wipes, static eliminator bars andantistatic air knives can be used to reducethe problem.use. Card and paper should be kept awayfrom the printing area if possible.5. Raise humidity, care should be taken ifdamping down the floor to avoid slip hazards.6. Wear clean room overalls.7. Filter air conditioning. Care should betaken if turning off air conditioning that thenew source of air is not more dust laden.Light spotsDescriptionLight spots in the print caused by gain inthe stencil.Basic clean up measuresContamination is present on surfaces andin the air. Clean up measures can be employedto minimise dust.1. Clean all surfaces and floor.Use a damp cloth or vacuum with a HEPAfiltered exhaust.2. Close doors and use tack mats to minimisedust and dirt entering the screenprinting area. Also minimise the numberof people moving around in the area.People are the biggest source of dust. Ifadding additional enclosure take care thatair movement into the area is from a cleansource. For instance shutting the door willbe a waste of time if the air is then going tobe pulled from filthy air space above ceilingtiles.3. Use lint free wipes.4. Avoid fibrous packaging, sheets shouldbe removed from the transit box prior toCauseUndercutting caused by a dust particlebetween the stencil and positive duringexposure.129
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HowHow to be agreat ScreenprinterEd
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About this eBookI’m passionate ab
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06Table ofContents07 The Theory Bit
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The wrong way: a strong-deep flood.
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why a light flood is recommended so
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This is the single most important f
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When I first pointed this out to my
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The Theory Bit20Why is the 1-2-3 so
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The mesh does the meteringThe 1-2-3
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This gives us the ‘real’ TIV fo
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simple, in-control process.Years of
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The Optional Theory28At the shear r
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I’ve come across examples in all
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The Optional TheoryOur 50µm line b
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oughness can slow slumping; it prob
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The Optional TheoryThe exact part o
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atches of the ‘same’ mesh. My f
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The Optional Theory40The industry r
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the screen frame itself to compensa
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Print Faults - Making and fixing th
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Print FaultsThey include tape marks
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Wrong ink - Too much viscous drag (
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DustPrint FaultsWe threw some dust
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What’s the best order to print yo
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Colour shifts54high-frequency (non-
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We formed our own (subjective) opin
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And the winner is...Colour shifts58
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Getting the right exposureAnna Harr
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Getting the right exposureThe light
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3/4 full exposureEFFECTS: Emulsion
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Getting the right exposureThere is
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Undercutting from a rough stencilSo
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Getting the right exposure(or numbe
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Solving problems in the real worldA
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Solving problemsThe simple act of r
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Emulsion coatingThe advice about cl
Page 78 and 79: Solving problemsA quick tip to help
Page 80 and 81: stencil causes a thick edge needed
Page 82 and 83: Solving problemsThis screen-shot fr
Page 84 and 85: A modest Rz gives amodest absolute
Page 86 and 87: Solving problemsThe root cause of n
Page 88 and 89: Now the ink fully fills the extra s
Page 90 and 91: Solving problems90Stencil X gives b
Page 92 and 93: Moiré, causes and curesSteven Abbo
Page 94 and 95: Moire, causes and cures94fluential
Page 96 and 97: Figure ii. The overlayedpattern fro
Page 98 and 99: Moire, causes and cures98Causes and
Page 100 and 101: 2 15° moiréIt’s an unfortunate
Page 102 and 103: Moire, causes and cureson top of an
Page 104 and 105: Ideal. Find a RIP with an option fo
Page 106 and 107: Moire, causes and curescan’t pick
Page 108 and 109: frequency tend to have a lower ampl
Page 110 and 111: Moire, causes and curesis a half-tr
Page 112 and 113: Incidentally, note that the ratio o
Page 114 and 115: Moire, causes and cures114So, surpr
Page 116 and 117: grid) in a conventional set that wa
Page 118 and 119: Moire, causes and cures118what this
Page 120 and 121: Arguably the skipping takes place p
Page 122 and 123: Moire, causes and curesSummaryAs Ma
Page 124 and 125: MoiréDescriptionAn unexpected patt
Page 126 and 127: Problem solving GuideCause1. The mo
Page 130 and 131: Problem solving GuideTechnical refe
Page 132 and 133: 6. Substrate unstable.7. Changes in
Page 134 and 135: Glossary of terms used in this eBoo
Page 136 and 137: Glossary136Moiré amplitudeThe ampl
Page 138: A Macdermid Autotype HowTo eBookEdi
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