Manufacturing Materials: Metals, Plastics, Composites & Spec Charts

Metals & Alloys for CNC Machining, Sheet Metal & Tooling

Engineering metals and alloys provide isotropic crystal strength, high thermal conductivity, and predictable elastic moduli across precision CNC machining services, sheet metal forming, and mold tooling. While 6061-T6 aluminum serves as the baseline machinability reference, high-load brackets, surgical shafts, and die-casting cavities demand specialized alloy tempers and heat-treatment schedules.

Choosing between wrought bar, stretched plate, and cast tooling stock directly dictates part flatness after heavy pocket roughing. Compare the mechanical properties, cutting windows, cost ratios, and application boundaries of our stocked metal grades below:

Each alloy exhibits distinct surface reflectance and functional micro-textures after multi-axis milling and turning (as shown in the CNC-machined metal alloy comparison below). Inspecting the 5-axis simultaneous milled Ti-6Al-4V shrouded impeller blades, the masked bare-aluminum datum rails on the hard-anodized 6061-T6 linear stage base, and the brushed 17-4PH stainless ribbed coupling flange illustrates how cutter geometry adapts to substrate hardness:

Matching Metal Stock Form & Grain Direction to Part Geometry

Prismatic valve bodies, optical mounts, and heat-sink plates are routed to our Brother, Fanuc, and Mazak 3-axis and 4-axis Vertical Machining Centers (VMCs), which represent 75%–85% of shop capacity. Simultaneous 5-axis CNC machining on our AFMING trunnion center is reserved strictly for impellers, compound-angle manifolds, and contoured Ti-6Al-4V airframes.

Concentric shafts, threaded sensor bodies, and micro-medical pins run on Takisawa CNC turning centers and Star Swiss-type sliding-headstock lathes to hold ±0.005 mm (±0.0002″) diameter concentricity. For weight-critical structures, compare specific stiffness values in our lightweight metals engineering guide.

Tapping DFM Rule: Ductile 6061-T6, C11000 copper, and 304 stainless allow roll-form tapping (D_hole ≈ D − 0.5P, e.g., Ø5.5 mm for M6×1.0), whereas 7075-T651, Ti-6Al-4V, and hardened steels require cutting taps (D_hole ≈ D − P, Ø5.0 mm) or helical thread milling.

Engineering & High-Performance Thermoplastics

Engineering thermoplastics deliver electrical insulation, chemical inertness, low-friction wear resistance, and up to 50%–80% weight reduction over aluminum across CNC machining and custom plastic injection molding. However, polymers exhibit 30×–170× lower elastic moduli and 3×–8× higher thermal expansion than steel, requiring strict control of cutting heat, clamping pressure, and hygroscopic moisture conditioning.

Use the quantitative polymer matrix below to compare Heat Deflection Temperature (HDT), mold shrinkage, machining speeds, and dimensional stability across our stocked plastics:

Holding burr-free edges on thermoplastics requires high-rake polished carbide tooling and chilled-air cooling (as shown in the CNC-machined engineering plastic parts below). Notice the spotfaced ports and concentric sealing grooves on the natural PEEK manifold, the involute teeth and keyway bore on the white POM-C spur gear, and the milled isolation channels on the amber Ultem 1000 insulator:

Polymer Machining Physics, Stress Annealing & Optical Polishing

Machining high-temperature polymers like Ultem (PEI) and PEEK or low-friction POM-C and Delrin acetal requires vacuum chucks or contoured soft jaws to prevent localized clamping indentation. For polyolefins, see our HDPE CNC machining and chip-control guide to prevent stringy ribbon wrapping.

Optical polymers follow strict post-processing separation: CNC machined PMMA acrylic undergoes 70–80 °C stress-relief annealing followed by #800–#5000 wet sanding and diamond-paste buffing (SPI A-1) or Single-Point Diamond Turning (SPDT)—never flame polishing or aggressive solvent vapor. Conversely, molded or machined polycarbonate (PC) is annealed at 110–120 °C before Dichloromethane (DCM) vapor polishing.

When to Avoid Unfilled Nylon: Skip unfilled PA6 or PA66 for tight H7 bearing housings operating in humid climates; specify POM-C, PEEK-GF30, or PA66-GF30 so bore diameters do not shift by +0.3%–0.6%.

Carbon Fiber Composites, Laminates & Technical Ceramics

Fiber-reinforced thermoset composites and technical ceramics solve extreme engineering challenges where metals fail—delivering ultra-high specific stiffness in UAV airframes, >30 kV/mm dielectric insulation in high-voltage switchgear, and 1,650 °C refractory stability in semiconductor plasma chambers. Because cured carbon/glass fibers and sintered oxide ceramics are highly abrasive, they require specialized diamond tooling and dust-controlled machining cells.

Preventing laminate fraying and ceramic micro-chipping requires diamond tooling and rigid backing fixtures (as shown in the machined composite and ceramic parts below). Compare the radiused truss cutouts on the 4.0 mm 3K twill CFRP drone plate, the radial isolation slots in the aqua-green G10/FR4 disk, and the stepped inner seat on the sintered alumina (Al2O3) wafer ring:

Delamination-Free Composite Routing & Ceramic Diamond Grinding

Standard high-helix metal end mills pull upward on top carbon plies, causing peel-up delamination. As detailed in our CFRP, GFRP, and FR4 composite machining guide, we run Polycrystalline Diamond (PCD) compression routers and diamond-cut burr tools at 18,000–24,000 RPM with sacrificial phenolic backing plates.

For fully sintered Alumina (Al2O3), Zirconia (ZrO2), and Aluminum Nitride (AlN), conventional cutting tools cannot shear the 1,100–1,650 HV crystal lattice. Our technical ceramic CNC machining and diamond grinding cell utilizes resin-bonded diamond wheels on Okamoto precision surface and cylindrical grinders to hold ±0.005 mm (±0.0002″) without subsurface micro-cracking.

Ceramic DFM Rule: Replace sharp internal corners and thin cantilevers with ≥ R0.5 mm fillets and 0.3 mm × 45° edge chamfers; for rapid prototypes with complex internal threads, specify Macor machinable glass ceramic.

Elastomers, Vacuum Casting Resins & Industrial 3D Printing Materials

When part geometries require Shore A elastomeric sealing, 10–100 unit bridge production without hard steel tooling, or internal additive lattices, we route builds across liquid silicone molding, polyurethane vacuum casting, and industrial 3D printing services. Understanding Shore hardness scales (ASTM D2240 / ISO 868), silicone mold life (15–25 shots per cavity), and Z-axis layer anisotropy prevents premature field failure:

Cross-Family Functional Part Portfolio

Multi-Material BOMs

Shown: a bead-blasted 7075-T651 aluminum clevis bracket, a 316L stainless steel fluid valve manifold, a C3604 brass stepped fitting, and a virgin PEEK bearing bushing inspected on black granite.

• Single-Source Fit-Up: Mating metal shafts, polymer bushings, and elastomer seals are trial-assembled against shared GD&T datums before dispatch.
• Master Pattern Accuracy: CNC-machined or SLA and SLS 3D printed master patterns drive 15–25 bubble-free urethane castings per RTV-2 silicone mold.

Elastomer, Casting & Additive Design Rules

Shore A · PU · DMLS

Match durometer hardness, mold shrinkage, and post-machining stock allowances to your functional test conditions across urethane vacuum casting and elastomer molding:

• O-Ring & Seal Compression (AS568): Design static elastomer glands for 15%–25% compression (10%–18% dynamic) and 65%–85% groove fill.
• Injection Draft & VDI 3400 Texture: Provide 0.5°–1.0° draft on polished cores, adding +1.0°–1.5° per 0.025 mm (0.001″) of texture depth (1.5°–2.0° for VDI 24; 2.5°–3.0° for VDI 30).
• Uniform Polymer Wall Thickness: Keep molded plastic ribs at 40%–60% of nominal wall thickness to eliminate sink marks and weld lines.
• Hybrid DMLS + CNC Machining: Add +0.5–1.0 mm stock on critical DMLS metal bearing seats and sealing faces for post-build 3/5-axis CNC finish milling to ±0.010 mm.

How Do You Select and Verify Materials Across Processes?

Selecting the optimal material and manufacturing route requires balancing batch quantity, wall-thickness geometry, isotropic load requirements, and ex-factory turnaround time. While 3D printing and vacuum casting eliminate hard tooling upfront, subtractive CNC machining and precision sheet metal fabrication provide wrought metallurgical properties from unit one:

Every incoming billet, sheet, and resin lot passes a four-stage verification protocol before spindle release and final metrology inspection (as shown in the granite CMM datum setup below). Observe the vertical bridge CMM spherical ruby stylus probing the flat top datum face of a bare-metal 7075-T651 aluminum hydraulic manifold with four stepped cylindrical valve cavities:

Incoming Alloy Verification & Stress-Distortion Control

Shop-Floor Rule of Thumb: In our in-house CNC machining facility, when roughing asymmetric pockets removing >60% stock volume from 250 mm long aluminum plates, we mandate 6061-T651 pre-stretched rolled plate and alternating Flip-Flop roughing passes to balance internal stress release.

Troubleshooting Bowing (Symptom → Root Cause → Corrective Action): Symptom: A 250 × 80 × 12 mm housing bowed 0.18 mm after vise release. Root Cause: Extruded 6061-T6 flat bar retained cold-drawn skin stress. Corrective Action: Switch stock to 6061-T651 plate, anneal rough blanks at 155 °C × 3 h with 0.5 mm stock allowance, and finish on vacuum fixtures to hold ⏥ 0.02 mm flatness.

Metrology Routing: Rigid metals and engineering plastics are probed on our Zeiss Coordinate Measuring Machine (CMM), while thin sheet metal and soft Shore A elastomers use non-contact 2.5D Optical Vision Measuring Systems (VMS).

Material Stiffness, Thin-Wall Cutting Deflection & Shop-Floor Control

Material elastic modulus (E) and specific cutting pressure (kc) directly govern the thinnest wall we can machine without elastic push-away. Linear thermal expansion drift (ΔL = α · L · ΔT) is detailed in our aluminum residual stress and thermal deformation guide, and end-mill overhang deflection (δ ∝ L³/D⁴) is covered in our internal corner radius and tool deflection guide.

Material-to-Surface Finish Compatibility & Dimensional Growth Rules

Post-machining surface finishes and protective coatings alter surface hardness, corrosion resistance, electrical conductivity, and final bore dimensions. As established in our aluminum anodizing specification guide, anodic oxide grows 50% inward into the substrate and 50% outward, whereas ASTM A967 stainless steel passivation removes free iron with ~0.002 µm zero dimensional buildup:

Frequently Asked Questions (FAQ) About Manufacturing Materials