Overview #
Pad printing is one of the most technically demanding short-run decoration processes we run — the margin between a clean, fully transferred image and a smeared, incomplete one is often less than 0.05mm in cliché engraving depth or 5 seconds of ink open time. Brand partners who specify pad printing for cosmetic caps, promotional items, electronic accessories or rigid packaging components need to understand that the cliché and ink system are inseparable: get either wrong and transfer efficiency collapses regardless of how well the substrate is prepared. This guide walks through the exact process parameters we control on our pad printing lines, the quality thresholds we hold, and the production decisions we make when a job brief lands on our floor.
For a related specification, compare Gravure Cylinder Engraving: Cell Depth, Screen Angle & Ink Volume Specification before finalising the packaging brief.
Cliché Engraving: Depth, Geometry and Steel Grade #
The cliché is the master variable in pad printing. We use laser-engraved steel clichés for all production runs and polymer clichés only for sampling or very short runs under 500 pieces. On steel, our standard engraving depth for solid fill areas is 22–28 µm. Fine line work and halftone areas are engraved shallower — typically 18–22 µm — because deeper cells hold more ink than the silicone pad can cleanly lift, leaving residue in the cell and causing fill inconsistency on the substrate.
The cell geometry matters as much as depth. We specify a 60° included angle on the cell wall for most jobs. A steeper wall (closer to 90°) traps ink and resists pad pickup; a shallower wall (closer to 45°) releases ink too readily and causes image spread. For fine-detail logos under 0.5mm stroke width, we move to a 55° wall angle and reduce depth to 16–18 µm to maintain edge sharpness.
Steel grade is specified to DIN 1.2379 (equivalent to AISI D2 tool steel), hardened to 58–62 HRC. Below 56 HRC, the engraved cell walls deform under repeated doctor blade passes within 50,000–80,000 cycles, causing progressive depth loss and ink volume inconsistency. Our production clichés are rated for 500,000+ cycles at correct hardness.
| Parameter | Fine Detail (<0.5mm stroke) | Standard Fill | Heavy Coverage |
|---|---|---|---|
| Engraving Depth (µm) | 16–18 | 22–28 | 28–35 |
| Cell Wall Angle | 55° | 60° | 65° |
| Steel Hardness (HRC) | 58–62 | 58–62 | 58–62 |
| Recommended Ink Viscosity (s, DIN4) | 14–16 | 16–20 | 20–25 |
| Typical Transfer Efficiency | 85–92% | 78–88% | 70–82% |
Ink Viscosity, Open Time and Solvent Management #
Ink viscosity is measured on our floor using a DIN 4mm flow cup (per ISO 2431) at 23°C ± 1°C. We do not accept viscosity readings taken at ambient temperature without temperature control — a 5°C shift in room temperature changes solvent evaporation rate enough to move viscosity by 3–4 seconds on the DIN4 scale, which directly affects transfer efficiency.
Our standard one-component pad printing inks run at 16–20 seconds (DIN4) for most rigid substrates — ABS, polycarbonate, anodised aluminium and coated paperboard. Two-component inks with hardener, which we specify for chemical-resistant applications like cosmetic packaging that contacts alcohol-based products, run slightly higher at 18–22 seconds due to the hardener’s contribution to body.
Open time — the window between ink flooding the cliché and the pad picking up — is controlled to 3–6 seconds on our machines. Beyond 8 seconds, solvent flash-off raises viscosity above the pickup threshold and transfer drops below 70%, which is our internal reject threshold. We run enclosed ink cups on all production lines (not open ink troughs) specifically to extend open time consistency and reduce solvent loss between cycles. This is a non-negotiable setup requirement for any job running at under 1,000 pieces per hour.
Retarder solvent is added at 3–8% by weight when ambient humidity drops below 40% RH or temperature exceeds 28°C — both conditions accelerate surface skinning. We log temperature and RH at the press every 2 hours during production runs exceeding 5,000 pieces.
Pad Geometry, Shore Hardness and Transfer Mechanics #
The silicone pad is the transfer medium, and its geometry and hardness determine how ink releases from the cliché and deposits on the substrate. We stock pads in Shore A 5–12 range. Softer pads (Shore A 5–7) conform better to curved or irregular surfaces — cosmetic bottle caps, pen barrels, rounded packaging corners — but compress more under press force, which can spread fine detail. Harder pads (Shore A 9–12) hold image geometry better on flat or slightly curved surfaces but require more precise substrate height control (±0.1mm) to achieve full contact.
Press-down force on our machines is set to achieve 15–25% pad compression. Below 15% compression, ink transfer is incomplete at the image edges. Above 30% compression, the pad deforms laterally and image dimensions grow — we have seen logo widths increase by 0.3–0.5mm at 35% compression, which is outside tolerance for most brand identity specifications.
For two-colour registration on a single pad printing station, our achievable tolerance is ±0.2mm. Multi-station sequential pad printing can hold ±0.15mm with fixture-based substrate registration. We always confirm registration tolerance requirements before quoting multi-colour pad print jobs — if a brand’s artwork requires tighter than ±0.15mm, we recommend a different decoration process.
Quality Control: Inline Checks and Pass/Fail Thresholds #
Every pad printing production run goes through three QC checkpoints:
First Article Inspection (FAI): The first 10 pieces of every run are inspected against the approved colour standard under D65 illumination (per ISO 3664). We measure ink film thickness using a dry film gauge — acceptable range is 2–6 µm for standard one-component inks. Below 2 µm, opacity is insufficient on dark substrates. Above 8 µm, adhesion failure risk increases significantly, particularly on non-porous substrates like polypropylene without flame or corona pre-treatment.
Mid-Run Sampling: Every 500 pieces, 5 units are pulled for visual inspection and adhesion cross-hatch test per ISO 2409 (GT0 or GT1 pass; GT2 or worse triggers line stop and ink viscosity recheck).
Final AQL Inspection: We apply AQL 2.5 (per ISO 2859-1) for cosmetic defects on all pad printing jobs. Critical defects (missing image, wrong colour, adhesion failure) are held to AQL 0.65. This is the same AQL level we apply to our screen printing and hot stamping lines for brand-identity-critical decoration.
Specification Notes for Brand Partners #
When you brief us on a pad printing job, the three things we need immediately are: substrate material and surface finish (including any existing coating or treatment), the exact artwork file with stroke widths called out, and the end-use environment — specifically whether the printed surface will contact solvents, UV light or abrasion in use.
The most common brief mistake we see is artwork supplied at final size without stroke width annotation. A 0.3mm stroke looks fine on screen but is at the absolute limit of what a 22 µm engraving depth can reproduce cleanly — we will flag this and recommend either simplifying the artwork or accepting a slightly heavier stroke. We would rather have this conversation before cliché engraving than after.
Our typical process timeline: digital proof and cliché specification confirmation in 3–5 working days, physical strike-off sample on your actual substrate in 8–12 working days, production lead time 15–20 working days after sample approval. Steel cliché tooling cost is quoted separately and is a one-time charge — clichés are stored at our facility for repeat orders at no additional fee.
Frequently Asked Questions #
Q1: What engraving depth do you use for fine logo detail, and why does it matter for transfer quality?
A: For fine line work and strokes under 0.5mm, we engrave at 16–18 µm depth with a 55° cell wall angle. Deeper cells hold more ink than the silicone pad can cleanly lift at fine detail scales, which causes fill inconsistency and ragged edges on the substrate. Getting this depth right is the single biggest factor in reproducing small-scale brand logos cleanly.
Q2: What is your standard MOQ and lead time for a pad printing job on cosmetic packaging components?
A: Our standard MOQ for pad printing on cosmetic caps or rigid packaging components is 1,000 pieces per colour/design. Production lead time after sample approval is 15–20 working days. For repeat orders using an existing stored cliché, lead time reduces to 10–15 working days.
Q3: Which compliance standards apply to pad printing inks used on cosmetic or food-adjacent packaging?
A: For cosmetic packaging with any possibility of skin contact or indirect food contact, we specify inks compliant with EU REACH regulation (SVHC substance restrictions) and, where applicable, EU 10/2011 for indirect food contact migration limits. We can provide full ink TDS and SDS documentation for compliance review. For direct food contact surfaces, pad printing is not recommended — we will advise alternative decoration methods.
Q4: Can you print multiple colours in registration, and what tolerance should we design to?
A: Yes — on our multi-station pad printing lines, we hold ±0.15mm registration tolerance using fixture-based substrate positioning. For two-colour work on a single station, tolerance is ±0.2mm. We recommend designing brand artwork with a minimum 0.2mm colour separation buffer to ensure clean results at production scale.
Q5: What causes ink adhesion failure on pad-printed plastic components, and how do you prevent it?
A: The most common cause is insufficient surface energy on the substrate — polypropylene and polyethylene have surface energy below 36 mN/m, which is too low for ink adhesion without pre-treatment. We flame-treat or corona-treat all low-energy plastic substrates to raise surface energy to 42–48 mN/m before printing, and we verify with dyne test pens before the run starts. Adhesion is then confirmed by cross-hatch test per ISO 2409 at FAI — GT0 or GT1 is our pass standard.
Planning a packaging project? Contact our team to request a complimentary specification review and sample quote.
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