Screen E-Book (.PDF) - MacDermid Autotype

More documents

Recommendations

Info

Glossary of terms used in this eBookEOMEmulsion Over Mesh (sometimes calledProfile) – the extra thickness provided bythe stencil material, i.e.Thickness of the screen with stencil – Thicknessof the screen without stencil.One of the themes of this eBook is that ingeneral High EOM is a bad thing.RzA measurement of the roughness of thestencil. A stencil profilometer can give differentmeasures of the roughness, suchas Ra or RMS. But Rz is the most useful asthere is a very strong correlation betweenhigh Rz and bad edge definition. The picturesillustrate where Rz comes from (thestencil follows the ups and downs of themesh) and the difference between high(bad) and low (good) Rz.High EOMLow EOMFor capillary films, the stencil usually penetrates~50% into the mesh so the two imageslook like:High RzHigh EOM capillary filmLow EOM capillary filmLow Rzwith, of course, the stencil being on theprint side of the mesh.134
MacDermid Autotype DSPThe MacDermid Autotype Digital ScreenPrinter is a suite of PC programs that letyou explore many aspects of screen printingscience. You can download the suitefrom the same website as this eBook.MMCMoiré Mesh Calculator – one member ofthe DSP which lets you calculate moiréclashes between your halftone patternand your mesh.Mesh rulingMeshes are specified as so many threadsper inch or threads per cm. The finer themesh the higher the ruling.You have to be aware that some stainlessmeshes are measured in threads perFrench inch, which is 0.9384 of an Americaninch.Thread diameterThe thickness of the mesh thread (or fibre)is important as it influences the ink depositand the amount the mesh interferes withthe image. The diameter is specified in microns,μm.Halftone rulingHalftone images are made up of dotsspaced at regular intervals specified as lpi(lines per inch) or lpc (lines per cm). Higherquality usually implies higher halftone ruling.Dot shapeThe printer can choose the shape of thehalftone dots. They can be circular, elliptical,rhomboid etc. Shapes such as ellipticalare different in each direction (thinner inone direction, thicker in another) and arecalled asymmetric because they are nolonger symmetric. This asymmetry can affectthe visibility of a moiré pattern.Rosette patternWhen you print a 3-colour or 4-colourhalftone the dots overlay to produce theclassic rosette pattern that printers andcustomers seem to like.Dot buildThe thickness of the printed dots of ink. Ahigh build will give you stronger coloursbut also gives you a rough surface (andplenty of problems) if you print anothercolour on topDot gainIncrease in size of the printed dot overthe size in the positive and/or the stencil.Negative dot gain is a decrease in the size.Sawtoothing is one form of dot gain.Positive sawtoothing (or simplySawtoothing)When you print with a high Rz stencil, theink leaks underneath the stencil and convertsa smooth dot or a line into a sawtoothedversion.The sawtooth makes the dot or line bigger,so it’s called positive sawtoothing.Negative sawtoothingHere the dot or line is sawtoothed, butthe dot or line is smaller than it should be.This is negative sawtoothing and is usuallycaused by stencils with a high EOM.Moiré frequencyA frequency is simply the number of timessomething repeats itself. So a moiré frequencyis how many moiré spots or linesyou find per inch or cm.135
Page 1 and 2:
HowHow to be agreat ScreenprinterEd
Page 3:
About this eBookI’m passionate ab
Page 6:
06Table ofContents07 The Theory Bit
Page 11 and 12:
The wrong way: a strong-deep flood.
Page 13 and 14:
why a light flood is recommended so
Page 15:
This is the single most important f
Page 18 and 19:
When I first pointed this out to my
Page 20 and 21:
The Theory Bit20Why is the 1-2-3 so
Page 22 and 23:
The mesh does the meteringThe 1-2-3
Page 24 and 25:
This gives us the ‘real’ TIV fo
Page 26 and 27:
simple, in-control process.Years of
Page 28 and 29:
The Optional Theory28At the shear r
Page 30 and 31:
I’ve come across examples in all
Page 32 and 33:
The Optional TheoryOur 50µm line b
Page 34 and 35:
oughness can slow slumping; it prob
Page 36 and 37:
The Optional TheoryThe exact part o
Page 38 and 39:
atches of the ‘same’ mesh. My f
Page 40 and 41:
The Optional Theory40The industry r
Page 42 and 43:
the screen frame itself to compensa
Page 44 and 45:
Print Faults - Making and fixing th
Page 46 and 47:
Print FaultsThey include tape marks
Page 48 and 49:
Wrong ink - Too much viscous drag (
Page 50 and 51:
DustPrint FaultsWe threw some dust
Page 52 and 53:
What’s the best order to print yo
Page 54 and 55:
Colour shifts54high-frequency (non-
Page 56 and 57:
We formed our own (subjective) opin
Page 58 and 59:
And the winner is...Colour shifts58
Page 60 and 61:
Getting the right exposureAnna Harr
Page 62 and 63:
Getting the right exposureThe light
Page 64 and 65:
3/4 full exposureEFFECTS: Emulsion
Page 66 and 67:
Getting the right exposureThere is
Page 68 and 69:
Undercutting from a rough stencilSo
Page 70 and 71:
Getting the right exposure(or numbe
Page 72 and 73:
Solving problems in the real worldA
Page 74 and 75:
Solving problemsThe simple act of r
Page 76 and 77:
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 128 and 129: Dark spots / HickiesDescriptionDark
Page 130 and 131: Problem solving GuideTechnical refe
Page 132 and 133: 6. Substrate unstable.7. Changes in
Page 136 and 137: Glossary136Moiré amplitudeThe ampl
Page 138: A Macdermid Autotype HowTo eBookEdi
show all

Screen E-Book (.PDF) - MacDermid Autotype

Create successful ePaper yourself

Delete template?

Save as template?