How to make the handle printing more strong

The main issue: plastic surface is smooth, low surface tension. Ink can easily peel or scratch off, especially after dishwashing.

Common plastic types for knife handles: PP, ABS, TPE, PA nylon. Different plastics need different treatments.

1. Surface pre-treatment (the most critical step)

For PP / PE (hardest to print, non-polar plastic)

• Flame treatment: quickly flame the printing area to raise surface energy.
• Plasma treatment: better and more stable than flame, good for mass production.
• Corona treatment: another option for thin plastic parts.

Without this, ink will never stick well on PP.

For ABS / Nylon / TPE

• Degrease first: wipe with isopropyl alcohol to remove release agent, oil, dust from injection molding.
• Light blast (fine sand blast): create tiny micro roughness to lock ink. Do not over-sand.

Check surface energy: Use dyne test pen. Target ≥ 40 dyne for good printing.

2. Choose the right ink

Do NOT use general plastic ink. Use two-component (2K) food-safe plastic ink for cutlery:

• 2K ink (ink + hardener): chemical cross-linking after curing, high scratch & detergent resistance.
• Match ink to plastic material: PP dedicated ink, ABS dedicated ink.
• For dishwasher requirement: select ink resistant to alkaline detergent and hot water (60–70°C).

One-component air dry ink is cheap but weak, easy to rub off after washing.

3. Printing process control (pad printing / silk screen)

1. Mix ink and hardener strictly following ratio. Do not reduce hardener.
2. Control ink layer thickness: thin but full coverage. Too thick → crack; too thin → easy wear.
3. Flash off: let solvent evaporate properly before final curing.

4. Curing (very often ignored)

• 2K ink: full curing time is required. Some need 24–48 hours room temperature curing.
• Oven baking (low temperature 60–80°C) can speed up curing and improve adhesion. ⚠️ Do not use too high temperature, plastic handle will deform.

5. Add clear protective top coat

After logo ink fully cures, print a food-grade clear hard overcoat.

• Protect printed layer from friction, scratch and dishwasher chemicals.
• Big improvement for abrasion resistance.

6. Product & design tips

• Avoid very thin lines and small text; they wear faster.
• If possible, make a slight recessed area on plastic handle for logo. The ink sits inside, less friction.
• Avoid printing on the high friction grip area of the handle.

7. Strength test after printing

1. 3M tape test: stick tape tightly then peel; no ink flaking.
2. Eraser / steel wool rub test.
3. Dishwasher aging test: repeated hot wash cycles.

Alternative permanent marking (no ink peeling)

If ink still cannot meet durability requirement:

• Laser marking on plastic: no ink. The laser burns/foams the plastic surface to form mark. Permanent. Limitation: only single color, cannot do multi-color logo.