In product design, draft angles—the slope applied to vertical walls of a part—play a critical role in ensuring manufacturability. A draft allows the part to be released cleanly from the mould without damaging its surfaces or creating excessive friction. Even a few degrees of draft can mean the difference between a smooth production run and costly rework or rejected parts. For new products, considering draft early in the design phase avoids last-minute compromises, ensuring the final design balances both form and function.
When developing new components, it’s essential to evaluate how draft interacts with other design features such as ribs, bosses, or undercuts. Too little draft can trap parts inside the mould, while too much draft can compromise the intended look or fit of the product. By planning for draft during CAD modelling, designers reduce the likelihood of tooling changes later, saving both time and money. This foresight also improves prototype testing, since early samples will more closely reflect production-quality results.
In the context of mould design, the draft directly influences how many mould components—or “parts of the mould”—are required. A simple product with uniform draft in one direction might only need a straightforward two-part mould. However, if the design incorporates multiple drafts in different directions, additional side actions or sliding mould components may be necessary. Each added element increases mould complexity, production time, and cost. Understanding this trade-off allows designers to make informed decisions about where to simplify geometry and where to accept higher tooling investment.
Achieving the right draft in the final mould is a collaboration between designers and toolmakers. Toolmakers will carefully machine and polish the mould cavities to the specified draft angles, ensuring consistent release during production. For products requiring high cosmetic finishes, polishing is especially important, as poor draft or tool wear can leave drag marks. By aligning design intent with manufacturing capability, the final result is a product that is functional, aesthetically refined, and cost-effective to produce.
Ultimately, thoughtful consideration of draft angles not only smooths the path from concept to production but also influences long-term efficiency. By reducing wear on tooling, ensuring consistent part quality, and minimising the need for complex mould assemblies, draft becomes more than a technical detail—it becomes a cornerstone of successful product design and manufacturing.
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