Plastic Part Finishing: Printing, Painting and Laser Marking

Updated: 2026-10-22

Plastic post-processing can mean machining, joining, assembly or surface decoration. This guide covers printing, painting, marking and decorative coatings on moulded parts. For functional operations, see moulding versus CNC machining, ultrasonic welding and threads and inserts. These guides explain options; they do not confirm project-specific availability.

Which surface process fits the requirement?

• Pad or screen printing: compare for logos and legends; check access, curvature, texture, colours and registration.
• Painting: assess for coverage, colour and feel; identify masking, coating compatibility and permitted surface defects.
• Laser marking: assess contrast and readability on the selected grade. Durability still depends on the material, mark and service exposure.
• Foil, metallising or in-mould decoration: assess the required effect, geometry, tooling and handling. See IML and IMD.

How do you qualify adhesion and durability?

Use the actual resin grade, colour, moulded texture and chosen ink or coating. Surface preparation is system-specific: Marabu's pad-printing guidance describes treatments and product exceptions. It is not a universal treatment threshold or approval for every plastic.

Agree a reference sample and suitable adhesion, abrasion, chemical and weathering checks for the application. Record the method, exposure, pass criteria and inspection frequency. No decorative process is automatically scratchproof or suitable for every environment.

How should finishing be priced?

Separate artwork, fixtures, screens or plates, colour changes, masking, treatment, application, curing, inspection and packaging. Compare costs at the same accepted quantity, including rejects and repeat orders. Moulding in colour also has grade, pigment and quantity implications; neither route has a universal price advantage.

What should the artwork and cosmetic drawing contain?

Supply vector artwork with a revision, actual dimensions and a clearly identified datum on the moulded part. Specify the position and orientation of each mark, colours and areas that must remain free of ink or paint. A logo floating on a CAD screenshot leaves registration open to interpretation. Where a coating approaches a mating surface, thread, seal or electrical contact, show the masking boundary and permitted edge condition.

Separate appearance from function. Agree viewing conditions and reference samples for colour, gloss, texture and allowable defects. Identify the visible face and the surfaces hidden after assembly. If a safety label or machine-readable code must remain readable, define that functional requirement separately from general appearance. A colour code alone does not specify gloss, opacity or the look of a textured substrate.

How do you turn a durability requirement into a trial?

Write a test record containing the substrate grade and colour, moulded surface condition, treatment, ink or coating identity, cure conditions and elapsed time before testing. Use the supplier's current system instructions. Do not substitute a generic oven temperature or an arbitrary tape test for a documented process and method. The part must tolerate the preparation and curing steps as well as its intended service.

For each exposure, agree the chemical or cleaning product, concentration, contact time, temperature and application method. Define the abrasion tool, load and number of cycles where relevant. Then describe the acceptable outcome: retained readability, no unacceptable lifting, or a colour change within an agreed criterion. A pass on an unused sample cannot stand in for the required result after ageing. Keep a retained control sample for comparison and distinguish destructive test pieces from saleable parts.

Fictional example: an indoor control panel needs a printed symbol that is cleaned regularly. Compare two proposed ink systems on the actual moulded grade and texture, using the same artwork and agreed cleaning protocol. If one loses readability, log the failure and the process record before changing the ink or cure. The example supplies a decision method, not a universal solvent, cycle count or acceptance threshold.

How should defects, packaging and changes be controlled?

Separate a moulding defect from a decoration defect in the inspection record. Review poor registration, pinholes, colour variation, transfer marks and scuffing against the agreed samples. Check the finished part after assembly and representative packing: a finish that passes at the decorating station may be marked by contact with another part in transit.

Specify separation, protection of cosmetic faces, handling after cure and lot identification in the quotation. Confirm responsibility for scrapped mouldings when decoration fails. Artwork, pigment, resin, treatment, ink and curing changes need a defined reapproval route. Use the sample approval pack to record cosmetic checks and deviations, alongside the project-specific durability report.

What should you send for a quotation?

Include CAD, artwork, grade, cosmetic-face drawing, colour/finish reference, quantity and test requirements in the RFQ brief builder. Request review of moulding and finishing, with availability, samples and acceptance criteria confirmed in the written proposal.

Related: moulded surface finishes, quality and tolerances, quote comparison.