Definition
Annual Demand — also called Estimated Annual Usage (EAU) in North-American injection-molding RFQs — is the total number of identical plastic parts a customer needs in a 12-month window. It is the single most important input for cavitation, mold-class selection, press tonnage and target Cycle Time in any plastic injection project.
In a molding quote, Annual Demand drives every downstream economic decision: number of Cavity impressions, SPI mold class (101–105), required clamp tonnage, machine size, runner system (cold vs hot), and the amortization of tooling over the part price. Getting the EAU wrong by 2× usually means a wrong mold — either over-built and never paid back, or under-built and replaced 18 months in.
Annual Demand vs EAU vs lifetime volume
Three figures often get confused in RFQs and must be tracked separately:
| Term | Window | Used for |
|---|---|---|
| Annual Demand (EAU) | 12 months | Cavity count, mold class, press tonnage, machine selection |
| Lifetime Volume | Program life (3–7 yr typical for industrial, 1–3 yr consumer) | Mold steel hardness, total mold cycles spec |
| Order Quantity / Lot Size | Per release | Inventory, changeover frequency, raw-material POs |
A rule of thumb in the industry: if Annual Demand × program years > 1,000,000 cycles, the tool must be SPI Class 101 (production tool, hardened steel, > 1 M cycles). Below 100,000 cycles total, an SPI Class 104 or even Class 105 prototype tool is usually enough.
How Annual Demand drives cavity count
The classic cavitation formula uses Annual Demand directly:
Required cavities = (Annual Demand × Cycle time s) / (3600 × Annual press hours × OEE)
Worked example — Annual Demand 1,200,000 parts/year, target cycle 30 s, 5,000 productive press hours per year, OEE 0.80:
Cavities = (1,200,000 × 30) / (3,600 × 5,000 × 0.80) = 2.5 → round up to 4-cavity mold
The result is rounded up to the next mold-shop standard (1, 2, 4, 8, 16, 32, 48, 64, 96, 128) for layout symmetry and balanced filling. Higher EAU justifies higher cavitation, but only until tooling amortization stops paying back.
Typical EAU thresholds in plastics processing
| Annual Demand (EAU) | Typical molding decision |
|---|---|
| < 1,000 parts/yr | Reconsider process: 3D printing, CNC machining or vacuum casting often cheaper than tooling. |
| 1,000 – 10,000 | Single-cavity aluminum tool (SPI 105/104), prototype or bridge production. |
| 10,000 – 100,000 | Single or 2-cavity P20 steel tool (SPI 103), cold runner. |
| 100,000 – 1,000,000 | 2-, 4- or 8-cavity tool, hardened steel (SPI 102), often hot runner. |
| > 1,000,000 | High-cavitation 16/32/48/64+ tool, SPI 101 fully hardened, hot runner, automation, ideally dedicated press. |
These bands are rough but widely used in quoting; the exact break-even depends on part weight, resin price and cycle time.
Annual Demand and machine selection
Once cavitation is set, the molder works backwards to the press. Required tonnage is calculated from projected part + runner area and material [Tonnage Factor](glossary:tonnage-factor), then a press with at least that [Clamp Force / Tonnage](glossary:clamp-force-tonnage) and the right shot capacity (typically use 30–70 % of Shot Weight capacity) is selected. A high EAU may justify dedicating one press 24/7 to one mold; a low EAU usually means the tool shares a press with others, which raises changeover cost and lifts the effective Cycle Time.
Common pitfalls when stating Annual Demand
- Confusing peak-month with annual: customers sometimes state demand as their busiest month × 12. Always ask for the seasonality curve.
- Forgetting scrap and color changes: real demand from the press is
Customer EAU / (1 − scrap rate − sampling). - Ignoring family vs dedicated decisions: when two parts share a Design for Manufacturing family, splitting Annual Demand across a family mold can dramatically lower tooling cost.
- No growth assumption: a 3-year ramp from 200 k to 800 k EAU is a very different mold than a flat 800 k from day one. Quote both scenarios.
Related terms
See also: Cavity, Clamp Force / Tonnage, Cycle Time, Estimated Tonnage Required, Injection Molding Machine (IMM), Shot Weight.
FAQ
What does Annual Demand mean in injection molding?
Annual Demand (EAU) is the number of identical parts a customer expects to consume in 12 months. It is the input molders use to size the cavitation, choose the SPI mold class, select press tonnage and target a cycle time that hits the price.
What is EAU in plastic injection molding?
EAU stands for Estimated Annual Usage — the North-American name for Annual Demand. An EAU above one million typically requires an SPI Class 101 tool; under 100,000 a Class 103 or 104 is usually enough.
How do I calculate the number of cavities from Annual Demand?
Multiply Annual Demand by the cycle time in seconds and divide by 3,600 × available press hours per year × OEE. Round the result up to the next mold-shop standard cavitation (1, 2, 4, 8, 16, 32, 48, 64).
What is the difference between Annual Demand and lifetime volume?
Annual Demand covers 12 months and drives cavities, tonnage and machine choice. Lifetime volume covers the whole program (typically 3–7 years) and drives the steel hardness and the cycle-count rating of the mold (SPI class).
Is Annual Demand the same as forecast?
Almost. A forecast is a probabilistic estimate over time; Annual Demand is the point figure (often an average) the molder commits the tool to. Good RFQs include a low/medium/high Annual Demand band, not a single number.