What is an approval sample and why does it matter legally?

The approval sample, sometimes called a golden sample or PP sample, is the physical part the buyer signs off as the reference for production. Once signed, it defines the agreed standard: colour, texture, latch feel, fit, print position and finish. If a later shipment is disputed, the question is not whether the buyer likes it but whether it matches the approved sample. That is why the sign-off should be recorded in writing, with photographs, and with a sample retained on both sides.

How many sampling rounds should I expect?

One round means either the specification was exceptionally clear or nobody looked closely. Two to three is normal for a case with a custom foam cavity, because foam fit is a physical question that drawings cannot fully resolve. More than three usually signals an unclear specification rather than a weak factory - the fix is to write down what was wrong each round and send the consolidated list, rather than feedback one issue per round.

What should I physically test on a first sample?

Fit the real equipment with the real cables and accessories, not a representative stand-in. Close and open every latch at least twenty times. Check the lid for warp by placing it on a flat surface. Verify stackability if cases will be stacked. If the case is rated, ask for the test report that corresponds to the sample in your hand rather than to a previous generation. And check the print position against the drawing, because print placement errors are the most common reason a second round is needed.

How do I handle colour approval?

Approve colour under defined lighting and against a physical reference chip, not from a photograph on a screen. Colour matches shift between displays and between daylight and warehouse lighting. Agree a tolerance rather than an exact match - in practice this means a delta E limit - and record which lighting condition the approval was made under.

What belongs in a sign-off record?

Date, sample identification, the drawing revision it was built to, photographs of the approved part including any accepted imperfections, the written specification of tolerances and colour limit, who approved it on behalf of the buyer, and where the retained samples are held on both sides. Also record what was explicitly not approved, so that no one assumes silence means consent.

Protective Case Sampling and Approval Sample Process

Sampling is where a case specification stops being a drawing and becomes an object. It is also the last stage at which changing your mind is cheap, which makes it the stage worth the most attention per hour spent.

The stages, and what each one is for

Stage	What it produces	What it is actually testing
3D data review	Agreed geometry and tolerances	Whether the design can be made at all, and at what tooling cost
Prototype shell	Machined or printed part	Fit against real equipment, ergonomics, stacking
First shot from tool	Parts in production material	Mould correctness - fill, warp, sink, latch engagement
Foam fit trial	Cavity in production foam	Whether the cavity holds the equipment under shake and drop
Approval sample	Signed reference part	Full specification compliance, including colour and print
Production validation	Parts from a normal production run	Whether the process repeats the approval sample at speed

Each stage exists because the next one is more expensive to iterate. A geometry problem found at 3D review costs an edit; the same problem found at first shot costs a tool modification.

Sample assembly and sign-off in the production line — First article, pre-production sample and mass production each run the same sign-off form.

What to check on a first-shot sample

Work through the sample in a fixed order so that nothing depends on memory. The order below runs from the things that are hardest to change to the things that are easiest.

Structure and geometry. Wall thickness consistency, absence of sink marks on visible surfaces, warp when the lid rests on a flat surface, and flushness of the lid-to-base seam.
Seal and closure. Gasket seated evenly in its groove with no twist or gap, latches engaging fully, and the lid not rocking when closed.
Latch cycling. Open and close every latch at least twenty times. Latches that feel stiff or gritty now will not improve in production.
Foam fit. Insert the real equipment with its real cables. Shake the closed case gently and listen. The equipment should not move.
Hardware and fittings. Handle return, wheel rotation if fitted, hinge smoothness, and the security of every fastener.
Finish and colour. Under agreed lighting, against the reference chip, checking both shell and any painted or printed area.
Print and marking. Position, size and adhesion against the drawing. Tape-test adhesion on a sample you are willing to sacrifice.
Documentation. Dimensional report, and where applicable, the test report that corresponds to this specific sample.

Test the sample you intend to keep, and keep the sample you tested. A golden sample that has never been opened, dropped or cycled is not a reference - it is a display piece.

Running a foam fit test properly

Foam fit is the most common cause of a second sampling round, and the reason is almost always that the test used a stand-in rather than the real thing. A foam cavity cut to a drawing will hold a drawing; it may not hold the actual device with its cable, its protruding connector or its aftermarket accessory.

Supply the real equipment, or a mass-and-dimension-accurate dummy, before foam is cut.
Include every item that ships in the case - cables, chargers, spare parts, documents.
Specify the orientation the user will actually open the case in, and confirm nothing falls out when it is opened.
Shake test: hold the closed case and shake in all three axes. Movement means the cavity is too large or too shallow.
If the contents are heavy, check that the foam is not bottoming out - the cavity base must not be the load path.

Writing a sign-off that protects both sides

A good approval record is not a formality; it is the document that ends arguments before they start. It should be short, specific and photographic.

Identify the sample precisely - part number, revision, date, and the drawing revision it was built to.
Photograph the approved part from fixed angles, including close-ups of texture, print and hardware.
State the tolerances and colour limit in numbers, not adjectives.
List any accepted imperfection explicitly, with a photograph, so it cannot later be raised as a defect.
List anything explicitly not approved, with the required correction.
Record where retained samples are held by each party, and for how long.
Name the approver and the date.

None of this requires the buyer and factory to distrust each other. It requires them to have the same memory, which no one does after six months and three production runs. For a JUNZHIJIA programme the sampling sequence, the number of rounds, and the tests performed on each round are agreed at the start of the project, because they depend on whether the shell is a stock size, a modified stock size, or a new tool.

From Drawing to Approval Sample: The Protective Case Sampling Process

The stages, and what each one is for

What to check on a first-shot sample

Running a foam fit test properly

Writing a sign-off that protects both sides

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