Product life cycle and product development process

Why it matters

Every product — a two-wheeler, a mixer-grinder, a CNC controller — is born, grows, matures and is eventually withdrawn. Where a product sits on that curve decides how it should be priced, produced and improved. The development process before launch decides most of its cost and quality, so production engineers who understand both can cut time-to-market and avoid expensive late changes.

Key ideas

Product life cycle (PLC). Sales of a product plotted against time typically follow an S-shaped rise and a later fall, divided into four stages:

• Introduction: low sales, high unit cost (small batches, learning, launch promotion), usually losses. Few competitors. Process is flexible and often job or batch type; design changes are frequent.
• Growth: sales rise fast, unit cost falls with volume and learning, profits appear and grow. Competitors enter. Focus shifts to capacity build-up, standardisation and reliability.
• Maturity: sales peak and level off as the market saturates; competition is intense and prices fall. Profit per unit is squeezed, so cost reduction, process improvement (automation, value engineering) and product differentiation matter most. Usually the longest stage.
• Decline: sales and profits fall because of substitutes or changed needs. Options: harvest (cut cost, minimal investment), rationalise variants, find new markets, or withdraw.

Some writers add a development (pre-launch) stage with zero sales and negative cash flow, and a saturation stage between maturity and decline.

Extending the life cycle. Product modification (new features, improved performance), new applications or markets (exports, rural markets), new user segments, repositioning and price changes.

Product development process. A structured sequence from idea to launch. A widely used generic process has six phases:

1. Planning — identify opportunity, market segment, technology readiness; produce a mission statement.
2. Concept development — identify customer needs, set target specifications, generate and select concepts, test them.
3. System-level design — product architecture, division into subsystems and interfaces, preliminary process plan.
4. Detail design — full geometry, materials, tolerances, drawings, process plans, tooling design.
5. Testing and refinement — alpha prototypes (production-intent parts) and beta prototypes (from intended processes) tested for performance, reliability and user acceptance.
6. Production ramp-up — pilot production, training, removing remaining problems, then full-scale production.

Stage-gate control. At the end of each phase a review ("gate") decides go, kill, hold or recycle, based on technical, market and financial criteria.

Concurrent (simultaneous) engineering. Design, manufacturing, quality, purchasing and marketing work in parallel in a cross-functional team instead of throwing the design "over the wall". It shortens development time and reduces late engineering changes.

Cost commitment. Most of a product's life-cycle cost (commonly quoted as roughly 70–80%) is committed by design decisions, even though little money has been spent by then. A change costs little at the concept stage and very much after tooling is made — the reason for DFMA, value engineering and QFD in the following topics.

Economic yardsticks. Development projects are judged by development cost, time-to-market, unit production cost and product quality. Break-even time — the time from the start of development until cumulative cash flow becomes positive — combines development spending with the PLC sales curve.

Formulas

• Cumulative cash flow at year t: CCF(t) = −C_dev + Σ (contribution in year k), k = 1 … t
• Break-even (payback) time by interpolation: t_b = t₁ + |CCF(t₁)| / (contribution in year t₁ + 1)
• Discounted version: replace each contribution by contribution / (1 + i)ᵏ
• Net present value of the product programme: NPV = −C_dev + Σ CFₖ / (1 + i)ᵏ

Symbols: C_dev = development cost at time 0 (₹); CFₖ or contribution in year k = sales revenue minus variable cost minus period costs attributable to the product (₹); t₁ = last year with negative cumulative cash flow; i = discount rate per year (decimal).

Worked examples

Example 1 (standard) — break-even time. A new pump costs ₹60 lakh to develop (treated as spent at year 0). Net cash contribution over its life cycle is: year 1 (introduction) ₹10 lakh, year 2 (growth) ₹25 lakh, years 3–4 (maturity) ₹40 lakh each, year 5 (decline) ₹20 lakh. Find the undiscounted break-even time and total net cash.

1. Cumulative cash: end of year 1: −60 + 10 = −50; year 2: −25; year 3: +15 (₹ lakh).
2. Break-even falls in year 3: t_b = 2 + 25/40 = 2.63 years after launch.
3. Total net cash = −60 + 10 + 25 + 40 + 40 + 20 = ₹75 lakh.

Example 2 (GATE level) — discounted break-even and NPV. Same data at a discount rate of 10% per year.

1. Present worths (₹ lakh): 10/1.1 = 9.091; 25/1.1² = 20.661; 40/1.1³ = 30.053; 40/1.1⁴ = 27.321; 20/1.1⁵ = 12.418.
2. Cumulative: −50.909, −30.248, −0.195, +27.125, +39.544.
3. Discounted break-even = 3 + 0.195/27.321 = 3.01 years.
4. NPV = ₹39.54 lakh, positive, so the programme is worthwhile.

Lesson: the decline-stage year adds little after discounting, and every year of delay before launch pushes the high-contribution maturity years further out, cutting NPV — the economic case for shorter development cycles.

Common mistakes

• Saying profits are highest in the growth stage by definition. Total profit often peaks in late growth or early maturity; sales peak in maturity.
• Treating the PLC as fixed; strategy (modification, new markets) can extend maturity.
• Confusing cost committed with cost incurred during design.
• Listing the development phases out of order — system-level design comes before detail design; ramp-up is the last phase.
• Treating concurrent engineering as simply "doing things faster"; its point is overlapping phases with cross-functional teams to avoid late changes.

For GATE PI

Expect conceptual MCQs: characteristics of each PLC stage (sales, cost, competition, strategy), order of development phases, purpose of concurrent engineering and prototypes, and where cost is committed. Numericals, when they appear, are usually cash-flow based — break-even time or NPV of a development programme. Practise matching each stage with its typical production strategy.

Quick check

1. In which PLC stage is unit cost highest?
2. In which stage does sales volume peak?
3. Which phase comes immediately after concept development?
4. Development cost ₹40 lakh; contributions ₹10, 20, 30 lakh in years 1–3. Find the break-even time.

Answers: 1. introduction; 2. maturity; 3. system-level design; 4. 2 + 10/30 = 2.33 years.