Precision Parts and Mold Manufacturing for the Aerospace Industry

In aerospace, every gram counts; however, weight savings must be achieved without compromising strength and safety requirements. The material and the applicable material specification (e.g., AMS, EN or customer standard) are defined on the drawing.

• Aluminium alloys: 7075-T6/T7351 and 2024-T351 for high-strength structural parts; 6061-T6 for brackets and holders.
• Titanium and stainless steels: Materials such as Ti-6Al-4V, 15-5PH and 17-4PH are used for fasteners and fittings requiring a high strength-to-weight ratio or corrosion resistance; machinability is evaluated on a part-by-part basis.
• PEEK and PEI: Clips, bushings and cabin interior parts requiring high-temperature and chemical resistance as well as low smoke density.
• PPS and PPSU: PPS is preferred for fuel and chemical resistance, and PPSU for low heat release and impact strength in cabin interiors.
• PA12 and PC: Ducts, covers and lightweight enclosures.

For cabin interior parts, flammability, smoke and toxicity requirements (e.g., CS/FAR 25.853) drive material selection; resin grades backed by the relevant test data are therefore used. For PEEK and PEI molds, hardened steels such as 1.2343 that are suited to high mold temperatures are selected.

Aerospace parts are typically complex in geometry, low-to-medium in volume and subject to strict specifications. At the design stage, the part and the manufacturing method are optimized together.

• Method selection: CNC machining is preferred for low-volume structural metal parts, and injection molds for recurring plastic clips, bushings and covers.
• Mold flow analysis: For high-viscosity polymers such as PEEK and PEI, flow length, gate size and pressure drop are calculated in advance; weld lines are kept away from load-bearing areas.
• Thermal design: Plate expansion, guide clearances and thermal insulation plates are built into the design for high mold temperatures.
• Thin walls and lightweighting: Weight-reducing pockets and ribbed structures are validated by mold flow analysis against the risk of warpage and sink marks.
• Workholding fixture design: Part-specific workholding fixtures are designed so that thin-walled metal parts can be machined without distortion.

Design revisions are numbered and tracked; production is carried out only on the revision approved by the customer.

In aerospace parts, surface quality is critical for fatigue strength, coating adhesion and cabin interior appearance.

• Machined metal surfaces: Roughness values defined on the drawing (typically Ra 0.8–3.2 µm) are achieved; tool marks and sharp edges that could act as stress raisers are avoided, and all edges are deburred.
• Pre-coating preparation: On surfaces to be anodized, chromate conversion coated or painted, cleanliness and edge radii determine coating quality.
• Cabin interior plastic parts: Surfaces visible to passengers receive a fine VDI 3400 EDM finish or a finish matching the customer-approved texture sample; areas concealed in assembly receive an SPI C–D finish.
• Transparent parts: Lighting covers and display windows require an SPI A1–A2 polish.

Acceptance criteria for surface defects such as scratches, pits and flow lines are defined using boundary samples or the customer's standard. Texture and gloss matching of adjacent parts in the cabin is checked together at the sample stage.

Aerospace drawings are usually prepared according to geometric dimensioning and tolerancing (GD&T; ASME Y14.5 or ISO 1101) rules. The datum structure directly determines the measurement and workholding strategy.

In thin-walled aluminium parts, clamping forces and internal stresses can cause distortion after machining. The part is therefore allowed to relieve stress between roughing and finishing, and material is removed in a balanced manner. Hole patterns and precision features are machined in a single setup wherever possible to prevent error accumulation from re-clamping. Measurement is likewise carried out with fixturing that conforms to the datum structure on the drawing, so that the result reflects the part's actual condition in assembly. For plastic parts, dimensions are evaluated after the conditioning defined in the specification.

In the aerospace sector, CNC machining is a core technology not only for producing the part itself but also for manufacturing molds and workholding fixtures.

• Complex surfaces: Freeform parts and mold cavities are machined with toolpaths generated in CAD-CAM; toolpath simulation prevents collisions and machining errors.
• Pocketing and lightweighting: Thin-walled pockets in aluminium brackets and frames machined from solid are cut using trochoidal and adaptive milling strategies that keep the cutting load constant.
• Turning: Bushings, pins and threaded connectors are produced to tight diameter tolerances.
• EDM: Precision profiles and sharp internal corners in hardened steels are completed by wire or sinker EDM.

Approved CNC programs are archived with version numbers; every program change requires a new first article inspection for the affected characteristics. This approach supports the process stability expected by the aerospace supply chain and ensures the same result on repeat orders.

In aerospace, full conformity of the first part to the drawing must be documented before series production can begin. We run our trial and approval processes in line with this requirement.

• T0/T1 for molded parts: The T0 trial verifies filling, ejection and the operation of moving components at high mold temperatures; T1 samples are submitted with a dimensional report.
• FAI in AS9102 format: At the customer's request, part number, material and special process information, together with measurement results for all characteristics, are reported in line with the AS9102 form structure.
• Process window: For high-performance polymers, parameters such as drying, melt and mold temperature are defined within a narrow range, as they directly affect crystallinity and mechanical properties.
• Partial FAI: When the design, material, process or production location changes, first article inspection is repeated for the affected characteristics.

The approved sample and FAI report are retained as references throughout series production. In the first production batch, critical characteristics are re-checked to confirm process stability.

In the aerospace supply chain, quality requirements flow down to the lowest-tier supplier. We apply recording and inspection steps that support the supplier requirements of customers operating under an AS9100 quality management system.

• Measurement and verification: An inspection plan is prepared for critical characteristics; CMM or 3D scanning is established industry practice for freeform surfaces and is included in the plan when required.
• Material traceability: EN 10204 3.1 raw material certificates, heat/batch numbers and part lot numbers are linked to one another.
• Special processes: Documentation for processes such as heat treatment and coating is filed in accordance with the customer's approved supplier requirements.
• Foreign object debris (FOD) prevention: Cleaning and packaging controls are applied to guard against chips, burrs and contamination.
• Measuring instruments: Traceable calibration is one of the basic supplier requirements of aerospace customers and is tracked accordingly.

Nonconforming product is segregated and is not shipped without customer approval.