Cost is, understandably, a major factor in most engineering and production projects. However, for high-end industries, particularly those with stringent quality standards such as medical devices, aerospace, or critical engineering components, for example, cost reduction can never come at the expense of integrity.
The key is finding the right balance. This isn’t about cutting corners; it’s about integrating Design for Manufacturability (DFM) principles from the earliest stage to achieve quality standards efficiently.
Early design choices have a direct impact on tooling and final component cost. Here are the core areas where proactive design can ensure quality while optimising costs.
Wall thickness and ribs – Plastic injection moulding is a heat process, and plastics are poor heat conductors. In simple terms, a thicker part section takes longer to cool, increasing cycle time and cost. Keeping wall sections as thin and uniform as possible without compromising strength and stability reduces material content and shortens the moulding cycle.
With polymers, thicker sections do not always mean stronger parts; in some cases, excessive thickness can lead to inconsistency or brittleness due to uneven cooling. If a part requires strength, achieving it with ribs rather than thicker sections will maintain strength, promote faster cooling, and minimize potential defects like sink marks.
Part consolidation – Proactively looking for opportunities to combine two or more separate parts into a single moulding can eliminate assembly operations, ancillary parts (like screws or baffles), and the risk of defects associated with multi-part assembly. While the resulting mould tool might be more complex, the associated costs savings will typically justify the initial tool investment, even on shorter production runs.
Material selection is important, and prices vary widely, from basic polyolefins to specialised high-performance polymers like PEEK, and we are always happy to advise. While a lower cost material may be tempting, final part performance and production efficiency should also be key considerations. For example, a slightly more expensive, stronger polymer (like Nylon or ABS) might allow for thinner sections and fewer ribs, leading to a faster cycle time and a lower final part cost. This is one reason we always advise consulting with our team.
Furthermore, polymer prices are affected by purchasing volume, so aligning with a grade we already purchase in bulk can provide you with a cost benefit that outweighs adherence to a specific grade.
Tooling is a significant upfront investment in any plastic injection moulding project, but intelligent design can keep this cost manageable and unlock cost efficiencies further down the process.
A simple mould tool will inevitably be lower cost to produce. Therefore, designing a component to avoid complex features such as side wall holes or deep undercuts avoids the need for cost-adding side actions (sliders or lifters) in the mould. Tools that avoid these complex movements are typically “straight open and close,” and are much cheaper to manufacture and maintain.
Where complex features or threads are necessary, the anticipated volume will determine the approach. For high volume production, for example, it’s often worth the extra upfront cost to “mould in” such features to eliminate secondary operations further down the production line.
For high volume projects, the higher upfront cost of a multiple cavity tool (i.e. two or more of the same part produced in a single cycle) or a family tool (multiple similar parts in one cycle) could drastically reduce overall production costs. We are always happy to advise on optimum cavity configuration for your volume requirements.
The old adage in engineering is especially true in plastic injection moulding: the sooner in a product lifecycle you make a design change, the cheaper it will be. We’ve seen promising products fail to reach full production because critical design changes needed to meet production and profitability margins were identified too late, making the entire project commercially unfeasible.
The team at Skar are always happy to offer advice, support, and DFM guidance on your project, from initial “napkin sketch” through to final delivery.
For further enquiries or more detailed information please call us on 01473 828000 or email us at sales@skar.co.uk