Composites and precision manufacturing go hand-in-hand. And in highly competitive industries like defense and aerospace, composites companies must pay as much attention to tooling as they do final parts. A poorly designed tool creates unnecessary quality and cost burdens. On the other hand, a well-designed tool sets the stage for high-quality precision manufacturing.
Composites companies need to look at a long list of considerations when designing high-performance tooling. Here is the top five:
Curing at high temperatures is normal for composite materials. In fact, autoclave curing is the most commonly used method. Unfortunately, parts and tooling both expand with heat and contract as they cool. So the tooling material and part must have similar Coefficients of Thermal Expansion (CTE).
Composite companies often rely on carbon fiber tooling because it offers the closest CTE match to most carbon fiber parts. This close match minimizes warping, dimensional deviation, and even residual stress.
Composites companies must take into account the durability of each new tool. For example, a prototype tool might hold up just fine for 5-10 cycles. Yet it would not hold up to hundreds of cycles or full-run production. So tool materials and design must offer the required life expectancy.
For prototyping, when speed and cost effectiveness cannot be sacrificed, composites companies can rely on things like machinable epoxy boards and 3D-printed tools. But for high-volume and high-temperature runs, they must use more robust materials capable of handling the stress.
Parts can be manufactured through any number of processes. Composites companies work with prepreg layups, resin transfer molding, and even vacuum infusion. Each manufacturing process has its challenges. One process might be susceptible to poor resin flow, while another presents constant challenges with trapped air.
Engineers must account for manufacturing processes in relation to both preventing quality issues and creating parts that are up to spec. In addition, they must pay attention to where and how they locate features like drill bushings and indexing points.
Some tooling, especially in large-scale applications, requires complex handling and support structures. Simply put, a tool is virtually useless if it cannot handle its own weight. It will not hold up well if it cannot handle autoclave pressure or becomes unstable when being moved across a facility.
Composites companies address structural rigidity by engineering torsion-resistant substructures. This often involves combining steel or aluminum framing with a composite face. Such designs introduce additional challenges relating to deflection, thermal management, and safe handling.
Tolerance is everything in precision manufacturing. The overall dimensions and surface roughness of every finished part must meet extremely tight tolerances without exception. Poorly implemented tooling makes meeting those tolerances more difficult.
Compensation is a big part of achieving tight tolerances. Unfortunately, composite parts are subject to something known as ‘spring-in’. The phenomenon results in angles that slightly close as a part cools. To compensate for spring-in, engineers must build negative angular compensation into their tool designs.
In terms of surface finish, tooling directly impacts quality. For example, tools cannot be allowed to create fiber print-through. Engineers rely on high-quality surface coatings to achieve the required surface smoothness. And proper surface smoothness helps engineers achieve the tightest tolerances.
Precision manufacturing is not for the faint of heart. Fortunately, manufacturers have access to composite tools capable of meeting the most precise needs. Companies like Aerodine contribute to that tooling. If not for advanced composites, today’s precision manufacturing simply would not be possible.
