Should I open a new mould or adapt a stock case?

Start from the stock catalogue. A stock shell has already absorbed its tooling cost across thousands of units, so you inherit a proven geometry at no amortisation. Open a new mould only when something the stock range cannot satisfy is genuinely load-bearing for your product - a dimension that no stock size fits, an internal feature such as a mounting boss or panel cut-out that cannot be added by secondary machining, or a volume high enough that the per-unit saving pays the tool back within a timeframe you accept.

How do I calculate the break-even volume?

Divide the total tooling cost by the per-unit saving the new design delivers against your best stock alternative. If the new shell costs 4 less to make or lets you delete a component worth 4, and the tool costs 40,000, the break-even is 10,000 units. That is arithmetic, not a quote - and it should be compared against how long 10,000 units will actually take you to sell, not against an optimistic forecast.

Which design features drive tooling cost up fastest?

Undercuts, because each one needs a side action or slider; deep ribs, because they require EDM and slow cooling; tight tolerances on large dimensions; and cavity count, because a two-cavity tool roughly doubles the cavity machining while only improving output. Uniform wall thickness is the cheapest thing you can give a toolmaker and the single biggest lever on both cost and cycle time.

Should I prototype before cutting steel?

Yes, and the cheapest way is usually not a prototype mould. CNC-machined or 3D-printed shells from the same 3D data let you verify fit against the real equipment, latch feel and stack dimensions. A prototype mould in aluminium is the next step up when you need parts in the production material to test drop performance and seal compression.

Who owns the mould after the project ends?

Whoever pays for it, if the contract says so - and it must say so explicitly. Confirm in writing: ownership of the tool, whether it may be used for other customers, where it is stored and maintained, what happens if the supplier ceases trading, and whether you can have it moved to another moulder. Tool ownership disputes are far cheaper to prevent than to resolve.

Protective Case Tooling Cost: Amortisation and Break-Even

Tooling is the moment a case project stops being a purchase and becomes a capital decision. The arithmetic is simple; the discipline is in being honest about volume and in retiring design risk before steel is cut.

What you are actually buying

A case mould is a precision tool built to hold a dimensional tolerance for a defined number of shots. Its cost is dominated by three things: the size of the part, the complexity of the geometry, and the steel specified - which in turn is chosen for the expected tool life and the abrasiveness of the material running through it.

Cost driver	Why it costs	What you can do about it
Part size	More steel to machine, larger machine required, longer cycle time	Design to the smallest shell that genuinely fits the equipment plus foam
Undercuts and side features	Each needs a slider or side action - a moving assembly inside the tool	Redesign to pull straight from the mould, or add the feature by secondary machining
Wall thickness variation	Causes sink marks and warpage; forces lower injection speed and longer cooling	Keep walls uniform - the cheapest quality improvement available
Tolerance and surface finish	Tight tolerances need more finishing passes and more inspection	Specify tolerance only where function demands it, not across the whole part
Cavity count	Machining scales with cavities; output does not scale linearly with cost	One cavity for validation, multi-cavity only once demand is proven
Tool steel and expected life	Hardened tool steel costs more but survives abrasive and high-volume running	Match steel to realistic lifetime volume, not to an aspirational one

Mould library and custom mould work for protective cases — Tooling is amortised against cumulative volume — the number decides whether it pays off.

Amortisation done honestly

The most common error in tooling decisions is amortising over forecast volume rather than committed volume. A tool paid back over an optimistic three-year forecast is a liability the moment the forecast moves.

Write down the all-in tooling cost - tool, any trial shots, any design changes after first sampling, and secondary fixtures.
Identify the best stock-case alternative and price it honestly, including any compromise it forces you to accept.
Compute the per-unit difference between the two. Include saved components, saved assembly labour, and saved freight if the new geometry packs better.
Divide step 1 by step 3. That is your break-even unit count.
Convert that unit count into time using your actual, not aspirational, sales rate. If the answer is longer than your product's expected life, do not cut steel.

A tool that pays back in 18 months of real orders is a good decision even if the absolute cost looks high. A cheap tool that pays back in six years is not a saving.

Retiring risk before the steel is cut

Every design change made after steel is cut costs more than the same change made before it, and the ratio is steep. The sequence that minimises spend is deliberately low-tech at the start.

3D data and fit check. Verify the equipment fits the proposed internal envelope with foam, before anything physical exists.
Machined or printed prototype. A shell produced from the same data by CNC or additive manufacturing costs a fraction of a tool and catches fit, latch feel, handle balance and stacking problems.
Mould flow analysis. Simulation of how the cavity fills predicts weld lines, air traps and warpage while geometry is still cheap to change.
Prototype or aluminium tool. Parts in the real production material, for drop testing, seal compression testing and latch cycling.
Production tool. Hardened steel, built only after the above three have passed.

Buyers often want to skip to the last step to save time. In practice the intermediate steps are what make the last step fast, because a production tool built from validated geometry usually samples correctly first time.

The contract questions that matter more than the price

Who owns the tool, in writing, and is the ownership conditional on reaching a volume?
May the tool be used to produce cases for other customers?
Where is the tool stored, who maintains it, and who pays for refurbishment at end of life?
What is the quoted tool life in shots, and what happens at the end of it?
Can the tool be transferred to another moulder, and is there a charge for that?
How many trial shots are included, and who owns the resulting parts?

These are the terms that determine what your tooling money actually bought. Two quotes that differ on price but are identical on these points are genuinely comparable; two quotes that differ on these points are not comparable at any price. For a JUNZHIJIA project, the figures that apply to your geometry - tool cost, expected tool life, and the volume at which the tool pays back - are established during engineering review, because they follow from your part design rather than from a price list.

Protective Case Tooling Cost: When a New Mould Actually Pays Off

What you are actually buying

Amortisation done honestly

Retiring risk before the steel is cut

The contract questions that matter more than the price

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