Capama Blog

Prepress is the least visible and most expensive part of label printing. Discover only on press that a font is missing, trapping was never applied, or the color profile does not match the substrate, and the loss is not a few sheets — it is a full roll of material, a full shift of machine time, and a delivery date already promised to a customer.

Industry data shows why this matters. According to published industry statistics, China's label printing market reached roughly RMB 51.12 billion in 2023 with output of about 9.98 billion square metres, around a quarter of global consumption; by 2025 demand has moved toward fine-segment applications such as new-energy battery labels, medical-device identification and tea-beverage cup labels (Source: Baidu Baike, "Label Printing", citing industry statistics). The global digital label printing market was valued at about USD 12.12 billion in 2025 and is projected to exceed USD 20.7 billion by 2035, a CAGR of about 5.5% (Source: Research Nester, report dated February 2026). With runs getting shorter and lead times tighter, prepress throughput directly determines how much work a converter can accept.

Policy is pushing the same way. China's National Press and Publication Administration, in its "Three-Year Action Plan for the Digitalization of the Printing Industry (2025–2027)", calls for developing a "new-generation prepress workflow software system" and for fundamental standards covering "digital prepress file formats, cross-platform color management specifications and printing process control requirements" (Source: National Press and Publication Administration website, June 2025). Standardized, disciplined prepress has moved from a bonus to a baseline requirement.

1. Step One: File Preflight — Stop Problems Before They Reach the Press

The first gate is preflight. The standard checklist covers page size, bleed, text content, image format and links, color mode, fonts, applied effects, and print-critical factors such as overprint and trapping (Source: prepress preflight practice references).

• Size and bleed: the industry-standard bleed is 3 mm — extending 3 mm beyond the trimmed size on all four sides — so that die-cutting or trimming tolerance does not leave white edges (Source: prepress inspection practice references).
• Color mode: output files in CMYK; keep process elements such as spot colors, foil stamping and spot UV on separate spot-color layers.
• Fonts and images: convert text to outlines or embed fonts; calculate image resolution at final print size, no lower than 300 dpi.
• Overprint and trapping: adjacent colors of different ink require trapping — deliberately overlapping neighbouring colors so that a slight misregistration does not produce a visible white gap in the finished product (Source: Adobe InDesign documentation, "About ink trapping").
• Transparency and effects: when shadows, transparency and blend modes stack up, first confirm that the PDF specification and the RIP can interpret them correctly; rasterize and flatten where necessary, then re-inspect the converted file for broken or shifted elements.

Field note: Turn the preflight checklist into a written specification per product family — cartons, labels, nameplates. Running every customer file through it first costs far less than firefighting later.

2. Step Two: Color Management — Make Color Measurable and Repeatable

Color management is fundamentally about aligning what the screen shows with what the press produces, moving color from "whatever the operator dials in" to something measurable and repeatable.

The standardized route is: first optimize plate making and press settings so output can reach a standard (for offset, ISO 12647-2), then control incoming data properly. Proofs must carry a standard, recognized color wedge — such as the Ugra / Fogra Media Wedge CMYK — that can be measured and verified; separations, soft proofing and physical proofing should all use CMYK ICC profiles that accurately reflect real press output (Source: colourmanagement.net, prepress color management practice).

Commonly used color standards include G7 (gray balance and visual appearance), ISO 12647 (print color standard), ISO 15339 (a standardized set of global color spaces), and profiles such as GRACoL, PRINTWIDE and ECG for specific print conditions (Source: printing.org, "The 6 C's of Color Management", July 2025).

• One ICC profile per press and per substrate: coated paper, PP, PET and synthetic stock each need their own curve, or colors will visibly drift when the material changes.
• Control spot colors by ΔE: brand colors — especially reds — should be accepted against a ΔE target, not "looks close enough".
• Build a standard-light viewing area: judging color under workshop lighting is not judging color at all.
• Digital color tooling is going mainstream: automated calibration tools and spectrophotometers are becoming standard equipment for ensuring consistency across printing processes (Source: epssw.com, "12 Label Printing Industry Trends to Keep an Eye on in 2025").

3. Step Three: Plate Distortion Compensation — The Hidden Dimension in Flexo and Letterpress

When printing with flexo or photopolymer plates, the plate is wrapped around a cylinder and stretched in the circumferential direction, so the printed image measures longer in the web direction than the artwork. Compensation must be applied before plate making.

The industry rule of thumb is that the larger the plate cylinder diameter and the thinner the flexo plate, the smaller the elongation; the distortion ratio is calculated from the actual plate thickness and actual printing length in use, and only after compensation will the printed product match the original artwork (Source: Flexotech technical article, "How to Calculate Flexo Plate Distortion").

• Cylinder-based plate making (imaging and exposing directly on a cylinder) largely avoids the elongation problem of flat plate making.
• Flat plate making (imaging flat, then mounting) requires a calculated distortion factor, refined by measurement.
• Every press and plate material must be re-tested — another converter's empirical formula cannot simply be borrowed.
• Measure dot gain together with distortion: for new work, run a test plate first to establish actual dot gain per color, then set compensation values (Source: journal of Shanghai Publishing and Printing College, "On the Plate-Making Process of Flexible Photosensitive Resin Plates").

Field note: Distortion ratio is a per-factory value. Build a lookup table of the distortion factor for your commonly used plate thicknesses and cylinder diameters, and post it at the plate-making station.

4. Step Four: Screen Making — The Precision Foundation of Screen Printing

In screen printing, finished-product precision is largely decided by the screen frame. Three parameters matter most: mesh count, tension and exposure.

4.1 Mesh selection

The finest reproducible line width depends directly on thread diameter and mesh opening. The empirical formula is: finest line width = 2 × thread diameter + mesh opening. For a 200 threads/inch nylon mesh with a 0.05 mm thread diameter and 0.077 mm opening, the finest reproducible line is about 0.177 mm (Source: Rihe screen printing equipment technical reference). Start from the finest line and smallest text in the artwork, then work back to the required mesh count.

4.2 Screen tension

Screen tension should be held at 20–30 N/cm. Too low, and the screen deforms during printing, degrading pattern accuracy (deviations greater than 0.05 mm); too high, and the mesh can break, shortening its service life. Tension uniformity matters just as much as the value (Source: Chinese patent CN101716847B).

4.3 Off-contact and squeegee parameters

For a standard-tension screen, the standard off-contact (snap-off) distance is about 1/300 of the inner frame dimension; squeegee pressure can be estimated at roughly 400–500 g per 1 cm of squeegee length (for example, a 50 cm squeegee corresponds to 20–25 kg or more), and insufficient pressure undermines the uniformity of the printed film thickness (Source: Asada Mesh technical reference). For high-definition screens, combination tensioning is preferred, with a standard mesh angle of 22.5°, adjusted to 30° or 35° if moiré appears.

5. Step Five: Imposition and Registration — Know Your Material Utilization

Labels are produced roll-to-roll, so step-and-repeat imposition directly determines both material utilization and registration stability.

• Leave enough gap: sufficient process clearance between adjacent images and between images and register marks, so that die-cutting and slitting do not interfere with each other.
• Register marks: every color needs recognizable register targets so the press can track them inline.
• Imposition automation: mainstream prepress systems such as Esko Automation Engine automate step-and-repeat, imposition and nesting, pulling data from external databases or MIS systems and supporting labels, folding carton, digital and other production types — reducing manual intervention and making imposition predictable and repeatable (Source: Esko product documentation). Industry observation shows prepress automation moving down from large operations to smaller converters, where automated prepress workflows, color management and finishing systems significantly improve efficiency, reduce errors and shorten turnaround (Source: epssw.com, 2025).

6. Step Six: Digital Prepress — No Plate, but the Work Does Not Disappear

Digital printing removes the physical plate, but the prepress workload simply moves to the file side:

• File discipline: vector files preferred, text converted to outlines; keep die-lines on a separate spot-color layer, never mixed with artwork.
• Variable data handling: manage QR codes, serial numbers and anti-counterfeit codes through a controlled data table (CSV/Excel), with field names mapped one-to-one to the template to eliminate misalignment errors.
• Profiles per substrate: digital presses also need device-specific ICC profiles, one per material.
• Link to inspection: prepress data can drive inline inspection directly. Esko has introduced an end-to-end digital label inspection workflow, AutoSet Digital, from prepress through AVT print inspection — evidence that linking prepress, printing and inspection data is becoming an industry direction (Source: Esko company news).

7. Step Seven: First-Article Approval and Archiving — Turn Experience into Assets

• Approve the first article: verify color (ΔE and visual), registration, die-cut depth and waste removal before running at volume.
• Archive everything: approved samples, substrate, color curves, imposition files and screen parameters stored together, ready to reuse on the next repeat order.
• One file per customer: lock down each customer's materials, color requirements and process combination, and repeat orders can be turned around very quickly.

Common Prepress Mistakes

Summary: Every Minute Saved in Prepress Is Profit

Prepress is not "preparation before the press" — it is the first line of defence for yield and delivery. File preflight blocks errors, color management guarantees consistency, distortion and screen parameters guarantee precision, imposition and automation guarantee efficiency, and first-article approval plus archiving guarantee repeatability. Get all seven steps right, and what happens on press is simply expected.

CAPAMA (Shanghai) Machinery Co., Ltd. has focused on label printing equipment for more than 20 years, covering Roll-to-Roll Screen Printers (CPM 520SX/SXT, RR-320S/520S/320ST), Rotary Letterpress (CPM270L), Digital Printing & Die-Cutting Machines (ZH-CW65), Multi-Layer Label Laminating systems (CPM-350ET/ETS/ETF), Screen Printing & Foil Stamping Machines (TJ-350) and Cushion Box Lid Machines (HCZ-6G/8G). Our technical team can help review your prepress workflow and match equipment and process parameters to your product mix.

CAPAMA (Shanghai) Machinery Co., Ltd.
Original content by the CAPAMA Technical Team. Please credit the source when republishing.