A make-or-buy decision is the analysis of whether a component, sub-assembly, or service should be produced internally or sourced from an external supplier. The decision is rarely purely about unit cost — it encompasses: strategic importance (does this capability represent competitive differentiation?), total cost of ownership (tooling, inventory, quality control, logistics), supply chain risk (single-source dependency, lead times), capacity constraints, and quality and reliability requirements.
Make decisions are justified when the component is core to competitive differentiation, when in-house production provides significant cost advantages at volume, or when supply chain dependencies would create unacceptable delivery risk. Buy decisions are justified when suppliers have specialized capabilities or economies of scale the company cannot replicate, when the component is commodity-like with multiple sources, or when internal production would distract from core competencies.
Make-or-buy decisions should be documented with explicit analysis, not made informally. The analysis should include: cost comparison (fully-loaded make cost vs. buy price), supply chain risk assessment, quality comparison, strategic alignment, and a sensitivity analysis for volume changes. Decisions made at low volume may need to be revisited at production scale, where the economics often shift significantly.
Practical Example
A robotics startup evaluates whether to design their own motor controller (make) or use an off-the-shelf driver (buy). Buy wins at prototype volume (low NRE, fast time-to-market). At 10,000 units/year, the analysis is reversed — custom design reduces unit cost by $12 and adds features that enable product differentiation.
How SpecZero handles this
Make-or-buy analysis appears in SpecZero as a concept comparison: one concept is 'custom-designed sub-assembly' (make) and another is 'purchased module' (buy). Pros, cons, difficulty ratings, and BOM cost estimates for each concept make the trade-off explicit before a decision is locked.
Related terms
Concept Trade Study
A structured comparison of design alternatives against a set of requirements and evaluation criteria.
Design Decision Log
A structured record of key engineering decisions, capturing the objective, alternatives, analysis, and rationale.
Bill of Materials(BOM)
A structured list of every component, material, and part needed to manufacture a product.
Design for Manufacturing(DFM)
An engineering practice of designing products to be easy and inexpensive to manufacture at volume.