Overview - ISO 12635:2021 (Plates for offset printing - Dimensions)
ISO 12635:2021 defines dimensional and physical requirements for metal lithographic printing plates used in offset printing, with additional flatness and edge criteria for computer-to-plate (CtP) applications. The standard applies to unprocessed plates (as supplied by the manufacturer) and aims to harmonize plate widths, lengths and thicknesses to simplify manufacturing and communication between plate, platesetter and press suppliers.
Key topics and technical requirements
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Measurement conditions
- Measurements are taken after equipment and plates stabilize at 21 °C ± 1 °C.
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Plate width, length and tolerances
- Preferred plate sizes are published in Annex D; where not used:
- Sheet-fed plates: dimensions must be specified in multiples of 5 mm (last digit 0 or 5).
- Web plates: width in multiples of 5 mm (last digit 0 or 5); length in multiples of 2 mm (last digit 0, 2, 4, 6 or 8).
- Size tolerances vary by process and dimension (e.g., typical tolerances for widths/lengths under 1500 mm are around ±0.8 mm to ±1.0 mm, increasing for larger sizes).
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Plate thickness
- The standard lists preferred plate thicknesses and associated tolerances (see Table 2 in the standard) to support consistent press handling and registration.
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Rectangularity
- The actual plate contour must always cover the inner tolerance rectangle and must not extend beyond the outer tolerance rectangle defined by length/width tolerances.
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CtP-specific edge requirements
- Edge waviness: Maximum wave height 3.0 mm, with recommended (should) limits of 1.5 mm (short edges) and 2.5 mm (long edges) depending on edge length.
- Cutting burrs: Shall not protrude more than 45 μm (recommended ≤ 30 μm), measured on each side and edge.
- Edge straightness (clamping edge): Deviation not greater than 200 μm over a 1000 mm interval (measurement points specified).
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Annexes provide test methods for waviness, burr height, straightness and preferred plate sizes (A–D).
Applications and who uses this standard
- Plate manufacturers - ensure supplied plates meet dimensional and burr/flatness tolerances.
- CtP and platesetter manufacturers - design equipment and handling to accommodate plate tolerances.
- Press manufacturers - specify compatible plate formats and clamping requirements.
- Printers and prepress technicians - QC incoming plates, minimize press set-up issues (register, gripping, web transport).
- Quality laboratories - perform acceptance testing using the test methods in Annexes A–C.
Related standards and context
- Developed by ISO/TC 130 (Graphic technology); aligns with other graphic-technology standards and ISO/IEC directives referenced in the foreword.
- Annex D lists preferred plate sizes to encourage format harmonization across the industry.
Keywords: ISO 12635:2021, plates for offset printing, CtP plates, plate dimensions, plate thickness, edge waviness, cutting burrs, plate straightness, graphic technology.
