Injection Molding Surface Finishing
The finish is decided in the tool, not after the part comes out. Texture, polish, colour and marking are specified together so the cosmetic result is repeatable from the first shot, with tooling, moulding and finishing under one purchase order and one quality plan.
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9 processes
Finish Options
ΔE < 1.5
Color Match Tolerance
0.025mm/°
Texture Depth
Materials
| Grade | Properties | Typical Applications |
|---|---|---|
| ABS and ABS-PC | Takes a fine texture consistently, accepts paint and plating with a primer, slightly higher shrinkage than PC, the most common housing material | Device housings, bezels, brackets, structural covers, painted enclosures |
| Polycarbonate (PC) | Excellent clarity and polish retention, high stress in thick sections, needs a drying step before moulding, accepts texture well at lower depth than ABS | Clear covers, lenses, transparent housings, optical parts, polished bezels |
| PMMA (Acrylic) | The best optical clarity of the common thermoplastics, polishes to a deeper gloss than PC, more scratch sensitive and hardens with UV exposure | Light lenses, light diffusers, display covers, premium decorative parts |
| PBT and PET | Dimensional stability, good chemical resistance, glass filled grades take a texture well, surface is slightly waxy and needs a treatment before painting | Connector housings, terminal blocks, structural frames, textured trim |
| PP and PP-GF | Low cost, high shrinkage, takes a coarse texture readily, paint adhesion needs corona or plasma treatment on the moulded surface | Interior trim, clips, covers, textured panels, appliance housings |
| Silicone and TPE (Overmoulded) | Soft 30 to 70 Shore A, matte by nature, cannot be polished, surface texture is a moulding feature and marking must be done by laser or pad print | Soft grip overmoulds, grips, seals, touch surfaces, wearables |
| ASA and LCP | Excellent UV and weathering resistance, ASA accepts texture and paint well, LCP gives a very smooth low shrinkage moulding surface | Outdoor housings, automotive exterior trim, weather exposed parts |
Process Parameters
| Parameter | Standard Range |
|---|---|
| Texture Depth per Degree Draft | 0.025 mm, adjustable to 0.06 mm |
| Texture Standard | VDI 3400, SPI-B, MT-11010 and equivalent |
| Gloss Polish Ra | Ra 0.02 μm on PMMA, Ra 0.05 μm on PC |
| Matte Polish Ra | Ra 0.8 μm |
| Spray Coating Thickness | 15 to 40 μm per coat, 2 to 3 coats typical |
| Soft Touch Coating Thickness | 30 to 80 μm |
| Metallisation Thickness | 0.2 to 1.0 μm base metal plus protective topcoat |
| Painted Color Tolerance | ΔE under 1.5 against the approved sample |
| Laser Mark Depth | 20 to 60 μm surface ablation |
| Pad Print Character Size | 0.8 mm minimum height |
| Surface Roughness (As Moulded) | Ra 0.4 to 1.0 μm depending on cavity finish |
Surface Finishes
VDI 3400 Texture
Chemically etched stainless steel cavity with a controlled grain that transfers into the plastic during moulding. The texture depth is a function of the etch depth and the draft angle, so the two are designed together. This is the standard for visible housings because it hides minor tool witness marks and gives a consistent grip.
Gloss and Matte Polishing
Multi-step polishing of the cavity steel produces a mirror surface for transparent parts and a soft satin for cosmetic opaque parts. Gloss polishing needs a draft angle below 3 degrees to pull off cleanly, which the design review checks before the steel is cut.
Spray Coating and Paint
Two or three coats of polyurethane or acrylic paint with a primer and clear coat, cured in a tunnel oven at 180 to 200°C. The moulded surface is treated with corona or plasma where the resin needs it for adhesion, and the colour is matched against an approved sample under standardised light.
Soft Touch Coating
Two component polyurethane with a matte or velvet feel, 30 to 80 μm thick, cured at 70 to 80°C to avoid distorting the part. The coating is a grip surface rather than a decorative one, and it needs a primer suited to the resin plus a cleaning step for the plastic to achieve adhesion.
Laser Marking
Laser ablation darkens or engraves the surface without ink, so the mark does not scratch off or fade. It works on most engineering plastics, produces permanent part numbers, logos and traceability codes, and is the right choice on soft touch coatings where pad print ink would not bond.
Pad Printing and Screen Printing
Silicone pad transfer for logos, warnings and serial numbers on curved or textured surfaces. Screen printing is faster on flat large areas. Both are economical at volume, and both need a surface treatment on low surface energy plastics such as PP and PE.
Metallisation and Vacuum Metallisation
A thin base metal layer with a protective topcoat gives a decorative chrome or mirror effect on a plastic part. It is applied in a vacuum chamber so the deposit follows every contour, including the inside of a hollow shell, which is why it is used for bezels and trim that would be too heavy or too difficult to machine in metal.
Anti-CStatic and Cleanroom Grade Finishing
Conductive and anti-static coatings for electronics housings, plus cleaning and particle-controlled handling for parts that go into sensitive assembly. The coating resistivity is measured and reported so the grounding path can be verified rather than assumed.
Design for Manufacturing (DFM)
- Decide the cosmetic finish before the tool is cut, because the cavity finish and the draft angle are chosen to suit it, and changing the decision afterwards means a new tool
- Allow 2 to 3 degrees of draft for a textured surface and up to 5 degrees for a high gloss polished surface, since the polished cavity pulls off much harder than a grained one
- Keep the parting line, the ejector witness and the gate vestige away from the primary viewing surface, because no coating hides a geometric defect
- Leave 0.1 to 0.2 mm of extra material on surfaces that will be painted, otherwise the coating film builds up on a high spot and the part goes out of flat
- Design the wall for the coating, because a 0.5 mm wall with 40 μm of paint on each side loses 4% of the wall stiffness, which matters on a housing that clips or carries load
- Specify a matte finish rather than a glossy one on surfaces that are handled often, because a gloss surface shows fingerprints and micro scratches within a week of handling
- Plan masking or a two-shot process for areas that must stay bare, and note that a masked boundary leaves a visible line on a painted part
- Keep laser mark areas flat and away from curved surfaces, since the focus distance changes across a curve and the mark depth varies with it
- Route the part design so that a pad print area exists where the logo needs to go, because a texture that is too coarse will not hold ink cleanly
- Upload STEP, IGES or DXF files and get a free DFM report within 24h covering draft, parting line, cosmetic surface and coating allowance
Tooling & Capacity
| Type | Lead Time | Suitable For |
|---|---|---|
| No Tooling (Machined or 3D Printed Part) | 5 - 10 working days | 1 to 50 pcs, design validation, market samples and appearance approval |
| Aluminium Soft Tooling with Finish | 2 - 3 weeks | Pilot runs of 25 to 500 pieces, verifying the cosmetic standard before committing to steel |
| Steel Production Tooling with Finish | 4 - 6 weeks | Volume production where the cosmetic result has to be repeatable for years |
| Two-Shot Tooling | 6 - 8 weeks | Parts with a soft touch overmould and a rigid substrate, or with two colours or two hardnesses in one part |
Quality Assurance
- Cosmetic appearance compared against the approved sample under standardised light, at agreed viewing angles
- Colour measured with a spectrophotometer and reported as ΔE against the approved sample
- Texture depth verified on the first shot article with a profilometer, not judged by eye
- Coating thickness and adhesion checked on every batch, with a cross hatch adhesion test on painted parts
- First Article Inspection report with full dimensional data plus the cosmetic approval sheet signed against the sample
- Laser and pad print marks checked for legibility, depth and adhesion on production samples
- Metal parts tested for coating adhesion and thickness on curved and recessed areas
- In-process inspection at each setup change, plus a cosmetic check on every batch before packing
- SGS, Bureau Veritas or TUV inspection can be arranged at any stage on request for finished moulded parts
- Finished moulded parts ship with a dimensional report, material certificate and Certificate of Origin
Applications
- Consumer electronics enclosures and bezel parts
- Appliance exterior panels and control surfaces
- Automotive interior trim and touch points
- Medical device enclosures and grip surfaces
- Lighting fixtures and diffusers
- Packaging and cosmetic containers
- Wearables and soft touch grips
- Point of sale displays and retail fixtures
- Laboratory and instrumentation housings
Why Choose FHY Precision
The cosmetic finish is designed into the tool, so the appearance is repeatable on every batch instead of being corrected after the part is moulded
One supplier covers tool, moulding and finishing, so the parts ship ready for assembly with one quality plan and one shipment
Colour controlled with a spectrophotometer and reported as ΔE against your approved sample, not judged by eye
Texture depth verified with a profilometer on the first shot article so the grained surface matches the standard you signed off
MOQ of 1 piece for machined or printed appearance samples, so you can approve the look before committing to tooling
A documented quality system backs third-party inspection and EN 10204 3.1 material certificates on request
Finishing handled inside our China plant, no trading layer on top
Stable capacity for repeat orders from appearance samples to 100,000 pc annual release
FAQ
1. What is VDI 3400 texture and why does it matter on moulded parts?
VDI 3400 is the German standard for a grained surface on moulded plastic. The grain is formed by etching the cavity steel, and the texture depth in the part is a function of the etch depth and the draft angle of the wall, at roughly 0.025 mm per degree of draft. It matters because a grained surface hides tool witness marks and minor flow lines, and it gives a consistent grip that a moulded gloss surface cannot. It is the default cosmetic finish for visible housings.
2. Should the finish be decided before or after the tool is built?
Before, and this is the single most important point in cosmetic moulding. The cavity surface treatment and the draft angle are chosen to suit the finish, so a gloss polished surface needs a lower draft than a textured one. Changing the cosmetic decision after the steel is cut means a new cavity, not just a new setting. If the finish is still open, the free DFM report compares the options and their consequences on the tool cost and the draft requirements.
3. Can you match a specific colour or a physical sample?
Yes. We colour match against your physical sample or a Pantone reference, run a first piece for approval, and then hold that approved sample as the standard. Colour is measured with a spectrophotometer and reported as ΔE, with a target under 1.5. Paint batches vary with resin lot and cure conditions, which is why the first piece approval and the recorded standard matter more than the nominal Pantone value alone.
4. What is the difference between soft touch and a matte texture?
A matte texture is formed in the mould, so it is part of the part with no coating and no extra process step. Soft touch is a sprayed or reaction-injected polyurethane coating applied after moulding, giving a rubbery or velvet feel that a moulded texture cannot match. Soft touch is a grip surface rather than a decorative one, it needs a primer matched to the resin, and it is typically 30 to 80 μm thick, so the part design has to allow for the film on mating faces.
5. Can you laser mark or print on moulded plastic parts?
Yes. Laser marking engraves or darkens the surface with no ink, so the mark cannot scratch off or fade, and it is the right choice for part numbers, logos and traceability codes, particularly on soft touch coatings where pad print ink will not bond. Pad printing transfers silicone ink onto curved or textured surfaces, and screen printing is faster on large flat areas. Both need surface treatment on low surface energy plastics such as PP and PE, and we flag this in the DFM report.
6. Can you make a plastic part look like metal?
Yes, through vacuum metallisation, where a thin base metal layer with a protective topcoat is deposited in a vacuum chamber. Because the deposit follows every contour, it works on hollow shells and recessed areas that would be difficult or heavy in real metal, which is why it is used for bezels and decorative trim. The alternative for small flat parts is chrome plating, which is more durable but needs the part to be plated and handled as a plated item.
7. What tolerance can you hold on a finished plastic part?
The part has to be moulded to tolerance and then coated, and the coating adds thickness, so the achievable tolerance on a painted part is looser than on a bare moulded part. Typical values are ±0.1 mm on a bare moulding and ±0.2 to ±0.3 mm on critical features after coating, with the coating thickness specified and controlled. Where a mating feature has to be held tighter, the design should keep that feature masked and uncoated, and the DFM report identifies where to do it.
8. Do you machine or print parts if I do not want to tool yet?
Yes. For appearance approval and market samples we can machine the part from a plastic block or print it in SLS or SLA, then apply the same texture, paint or marking process. This runs 5 to 10 working days and costs a fraction of a tool, and it is the sensible way to settle a cosmetic decision before committing to steel. The trade-off is that machined and printed parts do not reproduce the exact surface a moulded part will have, so we use them to confirm colour and marking rather than to judge texture depth.
9. How long does a finished part take?
Appearance samples through machining or printing take 5 to 10 working days including the finish. Aluminium soft tooling with a finish runs 2 to 3 weeks, and steel production tooling with a finish runs 4 to 6 weeks. Repeat production orders with a dedicated tool typically run 7 to 15 days for 1,000 to 10,000 pieces, depending on the number of setups and the batch size in the coating line.
10. How do you stop fingerprints on glossy finished parts?
Handling is the main cause, so parts are handled with clean gloves, separated by soft interleaf rather than stacked bare, and shipped in individual sleeves where the appearance is critical. A clear lacquer or an anti-fingerprint topcoat is the durable answer for display parts and for surfaces people touch often. For a part that is handled continuously, specifying a matte texture at the design stage is more effective than any coating, because the grain does not hold a visible print.
11. What information do you need to quote a finished part?
A 3D model in STEP or IGES, a 2D drawing with tolerances and cosmetic callouts, the resin grade, the annual volume, and a description or sample of the required finish including colour and texture standard. If a physical sample exists, tell us and we plan the first piece approval around it. If the finish is still open, the DFM report compares the options and their consequences on the tool cost, and quotes come back within 24 hours on working days.
12. How do you know the texture depth is right on the first shot?
The texture depth is verified with a profilometer on the first shot article, not judged by eye. The cavity etch depth is set during tool build and the transfer into the plastic depends on the resin, the melt temperature and the wall draft, so a measured value on the first shot is the only reliable confirmation. If the measured depth is outside the agreed band, the cavity etch is adjusted rather than accepting a cosmetic variation that will repeat on every batch.
13. What are the cost drivers on a cosmetic moulding order?
Three things. The tool, which is a one-time cost amortised over the program volume. The cycle time, which is set by the cooling time for the thickest wall, and a cosmetic wall of 0.3 to 0.5 mm adds to that. And the finishing, where paint and soft touch add handling and cure steps that are not on the injection machine. This is why the cavity count study matters: it shows piece price against cavity count and against finishing route with the tooling cost included, rather than quoting a cheap part and a surprise tool cost later.
14. Can you apply a finish to parts you did not mould?
Yes. We apply texture matching, painting, soft touch, laser marking and pad printing to parts supplied by you as well as to our own mouldings. For a customer with an existing tool or an existing supply base, this is a straightforward finishing subcontract. In that case we ask for the material grade and the surface condition, because the coating system and the adhesion preparation depend on the resin, and we quote a sample job first to confirm the finish before the batch runs.
15. How is a glossy clear part prevented from scratching in transit?
Clear parts are individually sleeved after the final inspection, and they are not stacked bare in the carton, because a single rub mark on a gloss surface is visible and is usually the reason a cosmetic batch is rejected. Within the factory the parts are handled with clean gloves and separated by a soft interleaf. For shipments that cross several handling points, an anti-scratch film or a protective lacquer is worth adding, and the decision is made at the packaging stage rather than after a customer complaint.
16. Do you offer third-party inspection?
Yes. We arrange inspection by SGS, Bureau Veritas or TUV at any stage you specify, from incoming material verification to pre-shipment dimensional and cosmetic checks. You receive a neutral report from an inspector you did not appoint, which is often what a brand owner requires before accepting a first lot from a new supplier. We can also add a RoHS or REACH declaration to the shipment documents on request.