A CMF document is a factory instruction, not a colour choice. We took apart a cordless vacuum on the bench and counted: 27 parts, 19 of them appearance parts, produced by at least 5 different processes. That ratio is what our CMF work looks like every day.
Every one of those 19 parts needs its own written record. Leave one column blank and the injection moulder and the paint shop will each fill it with their own assumption. The result is a tray of parts that are individually correct and collectively wrong. The vacuum looks cheap without anyone being able to say which part is at fault.
One appearance part, five fields
A typical finished product carries 10 to 20 appearance parts. For each one, our specification sheet writes down at least five fields: substrate grade, colour code, surface process, texture number, and the colour-matching condition with its tolerance. Miss any field and you have handed the decision to the supplier.
Colour tolerance is measured as ΔE in CIE L*a*b*. Parts from the same process in the same batch are held to ΔE ≤ 1.0. Adjacent parts from different processes, a painted shell sitting next to a textured one for example, are usually relaxed to ΔE ≤ 1.5 to 2.0. Different processes colour by different mechanisms, so forcing one number on all of them makes the target unbuildable.
Anodised dyed aluminium is the hardest class to control on a whole machine. Shade variation between dye tanks is easy to see by eye under D65. The industry norm is ΔE ≤ 1.5 with a same-batch, same-tank requirement written into the spec.
Texture is specified by VDI 3400 number or by the texturing shop's own sample number. Always pair it with a gloss value in GU. A texture number alone lets two texturing shops deliver two completely different hand feels.
Three origins, three ways to write the spec
The parts inside this machine fall into three families, and each family needs a different CMF entry.
| Appearance part | Substrate and process | Result | Consistency risk |
|---|---|---|---|
| Metal wand | Aluminium extrusion plus anodised dye | Real metal sheen, cool and hard | Shade variation between tanks in one batch |
| Dust cup | Clear PC plus hard coat | Transparent, the most expensive-looking part | Hard coat hardness fights haze |
| Main housing | PC+ABS textured in-mould, or primer plus colour plus clear | Matte, fine, resists fingerprints | Tolerance bands differ by process |
The metal wand starts as an extruded aluminium profile, then gets anodised and dyed. The oxide layer is clear. Dye enters the pores and is sealed in. The advantage is that the metal look is genuine: light reflects with direction. No paint on plastic reproduces it. The limit is film thickness. Too thin and the colour is pale with poor wear resistance. Too thick and the fine extrusion lines get magnified, so a crisp highlight band turns muddy. Consumer electronics usually sit in the low tens of microns. Push past that and depth and uniformity both get hard to hold.
The dust cup is a clear part with a hard coat. The body is clear PC or a copolyester, and a hard layer goes on the outside to resist scratching. It does one job for the design: it makes the internals visible, which reads as precision, and it is a big part of why the machine looks expensive. The cost is that clear parts demand one grade more discipline from the tool and the room. Resin drying, mould temperature and airborne dust all become visible defects. Hardness and haze also trade against each other. Coat it harder and it hazes, and the transparency is gone.
The main housing is plastic with surface treatment, on one of two routes. Route one is texture-in-mould with no paint: the pattern comes from the tool and the colour comes from masterbatch at injection. Route two is painting: mould a gloss part, then primer, colour coat and clear coat. The difference in feel is obvious. A textured part has a fine grain under the finger and reads as one piece. A painted part can achieve a more even matte or gloss, but it adds three processes and three more yield gates.
A colour chip becomes three problems in production
When a client points at a chip and says "that black", the sentence splits into three questions on the factory floor.
First, one colour code does not produce one appearance across processes. Paint can be tuned accurately. A textured part carries masterbatch inside the plastic and its colour is further shifted by the texture surface. Anodising puts dye into pores. Three mechanisms, three results. We hit this on a small appliance: we sent the same Pantone code to a paint shop and an IMD supplier, and the T1 samples were visibly two different colours. Nobody had done it wrong. We had written one tolerance number where we needed three. Since then our specs give tolerances by process band, tight within a process, wider across processes with a signed-off sample.
Second, a spec with no viewing condition is not a spec. The same part can read as three colours under D65, TL84 and illuminant A, especially metallic sparkle finishes and sensitive dark greys. The document must state the light source, its power and the viewing angle. Otherwise the sample looks one way in the client's office and another under the yellow lamps in the workshop.
Third, decide where part boundaries go. On this machine the top cover and the handle shell are two parts in two processes, but the eye reads one colour zone. That is where colour error shows first. Our practice is to pull visually continuous areas into one part or one process. If that is impossible, put a step or a colour break on the split line, so the mismatch sits behind a designed edge instead of spread across a flat face.
The texture column is the one most often under-written
Texture looks like "just a pattern", so it gets written carelessly. It actually sets three things at once: gloss, hand feel, and how dirty the machine looks after six months.
Texture depth and draft angle are locked together. Deeper texture needs a larger draft. A larger draft puts a sloped wall in the pull direction, and the highlight band deforms across it. On our first version we drew side walls at gloss-part angles. The texturing shop came back and said that depth was not achievable at that angle, so either the depth came down or the angle went up. We split the difference, and the matte level came out slightly flatter than the render. The lesson: confirm the texture sample before the tool is cut. Depth and draft are decided together, and later changes mean cutting steel.
Gloss is the field that should be there and often is not. The same texture number, polished brighter at the shop, comes out semi-matte rather than fully matte. We specify a GU range and require the supplier to shoot a sample inside it. The visual difference is immediate. Drop one step in matte and the surface goes from a soft scatter to a thin sheen. The plastic look comes back, and the clean highlight line is eaten by a hazy reflection.
Why the whole list matters
Fill every column and the specification holds. The teardown gave us a plain conclusion. This machine does not look expensive because one part uses an exotic material. It looks expensive because metal, clear and matte plastic each carry a distinct role, the boundaries between them are clean, and the colours do not fight. That is the job: define each appearance part so it can be produced, repeated, and matched to its neighbours, so the machine on the line is the machine in the render.
FAQ
Is CMF colour work the same as graphic design colour work?
No. CMF has to answer whether a colour can be produced reliably on a real material with a real process. Colour is one field among five. The same code reads differently on paint, on texture-in-mould and on anodising, and the CMF job is to price those differences into the spec before tooling starts.
What is the minimum content of a CMF specification?
Five fields per appearance part: substrate grade, colour code, surface process, texture number with a gloss range, and viewing source with colour tolerance. Tolerances should be banded by process, tight within a process and wider between adjacent processes, with a signed sample as the final reference.
Texture-in-mould or painting, how do we choose?
Decide by the surface you want and the volume you can commit. Texture-in-mould removes three processes and three yield gates and reads as one integrated part. Painting gives a more even matte or gloss, and you pay for it in process cost and appearance-defect risk. Check where the split lines fall first, because texture depth and draft angle are set together.
What do we do when metal and plastic will not match?
Solve it in the part split first. Pull visually continuous zones into one process where you can. Where you cannot, hide the difference behind a colour break or a step, then close it out with a matching sample. Anodised parts always carry tank-to-tank shade variation, so write a same-batch, same-tank requirement and inspect under the specified source.
Sources: Compiled from Hezi Industrial Design's own project experience; no external citations.
Article by Hezi Industrial Design — Dongguan, China. Originally published at hezidesign.com.
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