Aluminum is forgiving enough for fast prototyping and capable enough for aerospace hardware—if you match alloy, process, and finish to the job. This aluminum processing guide walks you through the full workflow engineers actually run in production: material selection, forming, CNC machining, surface finishing, inspection, and packaging. Along the way, you’ll see practical design windows, tolerance norms, and the trade‑offs that govern speed, cost, and quality.

Who is this for? Mechanical and manufacturing engineers, NPI managers, and technical buyers who want a single, credible reference for going from CAD to shippable aluminum parts—without bias for any one process route.

• Choose the alloy for the dominant constraint: extrudability and cosmetics (6063), general strength and machinability (6061), or maximum strength with tighter machining control (7075).

• Forming selection drives cost and lead time: use extrusion for long, repeatable profiles; die casting for high volumes and complex thin walls; billet CNC for low volumes and tight precision.

• Typical CNC practice holds many dimensions to ISO 2768‑m ranges; reserve ±0.01–0.05 mm for critical features with capability evidence and robust fixturing.

• Type II anodizing suits cosmetics and corrosion resistance; Type III hardcoat is for wear and durability. Specify thickness, class, color, and sealing.

• Inspection and packaging are not afterthoughts—CMM data, coating checks, and VCI‑based pack‑outs preserve function and finish through global transit.

• Lead time, cost, quality, and one‑stop execution are coupled. Align drawings and DFM early to avoid rework and schedule slips.

Choosing an aluminum alloy is less about memorizing datasheets and more about picking the right failure mode to beat. Think of it this way: What will break first—strength, surface appearance, tolerance stability, or budget? This part of the aluminum processing guide frames the common trade‑offs so you can specify with confidence.

A quick engineer’s comparison:

Notes that matter in production:

• Tempers: T6 yields strength; T651/T6511 adds stress relief for machining stability.

• Anodizing response: 6063 leads for cosmetics, 6061 is solid, while 7075 can show color variation and needs careful finishing specs.

• Stock strategy: Using common sizes (plate, bar, extrusion) reduces cost and lead, especially in early NPI.

This section of the aluminum processing guide helps you select and specify extrusion, die casting, or sheet/plate routes with realistic design windows.

Extrusion design fundamentals

Extrusion is unbeatable for long, prismatic shapes with consistent cross‑sections and repeatable cost at volume.

DFM windows that keep profiles stable:

• Wall thickness: practical minimums are often 1–3 mm depending on alloy and section size; aim for uniform walls and gradual transitions.

• Radii and blends: avoid sharp internal corners; add fillets to balance flow and reduce stress. Generous radii also machine better later.

• Straightness, twist, and flatness: specify only what you need. Precision classes exist, but tighter straightness or twist can drive up cost and scrap. Use referenced standards for the product form selected and align with your inspection method.

When to choose extrusion over billet CNC: volumes above a few hundred parts per year, long parts that waste billet, repeating internal features that can be built into the die, and cosmetic anodized surfaces that benefit from 6063.

For further tolerance class context and profile design precautions, align your drawings with the European EN 755 family and the Hydro manual cited above, then lock inspection methods accordingly.

Die casting selection and controls

High‑pressure die casting (HPDC) is the go‑to for high‑volume, thin‑walled housings with bosses, ribs, and integrated features. Low‑pressure die casting (LPDC) trades fill speed for lower porosity and better structural integrity in thicker sections.

• Process differences and selection

• Alloy data and DFM: the Aluminum Alloy Data from the North American Die Casting Association summarizes typical walls, draft, and mechanical properties by alloy. 

Practical DFM guidelines:

• Walls and ribs: 1–3 mm walls are common in HPDC; maintain uniformity and avoid abrupt thickness jumps that drive shrinkage.

• Draft: 1–2° is a reliable baseline; use more for deep ribs or textured surfaces.

• Gating, venting, and thermal control: these are the primary levers for porosity and surface quality. Engage the die caster early with CFD or flow simulation if the part is critical.

• Inspection: X‑ray or CT scans are standard in automotive and mission‑critical parts to confirm internal integrity when porosity risk is non‑trivial.

When to choose die casting over extrusion plus machining: higher annual volumes, complex geometry that would need many CNC setups, and when integrated features reduce assembly time.

Sheet forming and welding in brief

Sheet and plate are invaluable for enclosures and lightweight structures, but mind the tolerance stack. Minimum inside bend radius often starts near material thickness for 5xxx/6xxx series but increases with temper and thickness; prototype on the actual alloy and temper. 6xxx alloys are generally weldable, but the heat‑affected zone softens; if you plan to anodize after welding, preview color match and grain effects.

CNC machining that hits spec without burning time

This portion of the aluminum processing guide focuses on practical ways to hit tolerance while keeping cycle time in check.

Tooling and cut strategy:

• Use 2–3 flute, high‑helix carbide end mills for aluminum. This geometry clears chips and resists built‑up edge. 

• Start with manufacturer‑supported speeds and chip loads. 

Tolerances and capability:

• General dimensions: specify ISO 2768‑mK or similar for non‑critical features to avoid over‑inspection. Typical general tolerances translate to about ±0.1–0.3 mm depending on size band.

• Critical features: reserve ±0.01–0.05 mm for bores, datums, and fits that justify the control. Hit these with finishing passes, thermal stability, and a capable measurement plan.

Distortion and finish control:

• Sequence roughing to release stress, leave uniform stock, then finish in one balanced pass per feature.

• Use rigid, repeatable fixturing. Vacuum and soft jaws shine on thin walls; balanced clamping reduces bowing.

• Coolant and chip evacuation are quality tools—don’t skimp on them.

If you want deeper process specifics for aluminum on a single supplier site, this overview of aluminum CNC machining can help you benchmark typical services and part types before you RFQ. For a focused discussion on holding tight tolerances in aluminum CNC, this internal engineering blog outlines common failure modes and countermeasures in fixturing and toolpaths (tight tolerance machining guidance).

Anodizing is the default finish for aluminum parts because it improves corrosion and wear resistance and can be cosmetic. Specify it precisely. In this section of the aluminum processing guide, we map the standards to practical drawing notes.

• Standards and thickness: The U.S. military specification MIL‑PRF‑8625F defines Type II sulfuric anodize and Type III hard anodic coatings, including thickness bands and classes. As a rule of thumb, Type II is about 5–25 µm and is dyeable; Type III hardcoat runs roughly 50–100 µm with limited color options and superior abrasion resistance. 

• Dimensional effects: Roughly one‑third of the oxide thickness builds up above the surface; two‑thirds penetrates. Critical fits should be masked or finished post‑anodize.

• Color and alloy behavior: 6063 delivers the most uniform cosmetic results; 6061 is generally consistent; 7075 can exhibit color variation—design your color spec and acceptance criteria accordingly.

• Alternatives: Powder coat and painting add color coverage and chip resistance at the expense of tolerance control and, sometimes, heat performance. Mechanical finishes like bead blast or brush can equalize appearance before anodize—call out media and Ra if critical.

For a concise view of finishing options commonly offered through one provider.

Inspection and packaging that protect your yield

Inspection is where drawings meet reality; packaging is where reality meets logistics. Both deserve engineering intent. This aluminum processing guide consolidates the essentials below so you can lock your plan early.

Inspection plan essentials:

• First Article Inspection: Before scaling, verify a representative part meets all drawing requirements with documented results. Include CMM data for critical dimensions, coating thickness verification, and material certifications with heat lots for traceability.

• Ongoing sampling: Apply risk‑based sampling plans after you establish capability. For critical features or early runs, use 100% checks; transition to AQL sampling when process stability is demonstrated.

• Coating checks: For Type II and III, verify thickness and sealing as required by the spec.

Packaging and corrosion protection:

• Use VCI films or papers inside sealed packaging with desiccants and humidity indicators for sea or multimodal shipments. 

• Prevent cosmetic damage: isolate parts with foam or separators; avoid metal‑to‑metal contact; use edge guards; manage strapping tension.

• Crating and labeling: ISPM 15‑compliant wood, bracing, and clear labels with PO, part, revision, and lot/heat numbers support traceability and receiving efficiency.

This section consolidates the four cross‑cutting concerns teams ask about most: speed, cost, quality and risk, and one‑stop execution. It’s the heart of the aluminum processing guide when you’re moving from prototype to production.

Speed levers from RFQ to dock date:

• Parallelize early: confirm DFM and tolerance tiers while material is sourced and, if needed, tooling is designed.

• Book capacity for downstream steps: reserve anodizing or coating early to avoid queue delays.

• Design for inspection: mark critical‑to‑quality features and measurement methods on the drawing to prevent late debates.

Cost optimization without compromising spec:

• Put tight tolerances only where function demands; leave non‑functional cosmetics to visual standards rather than numerical Ra unless essential.

• Choose the process that matches geometry and volume: long prismatic shapes love extrusion; high‑volume thin‑wall housings favor die casting; complex one‑offs belong to billet CNC.

• Reduce setups and re‑chucks; design features so a single datum structure can carry most tolerances.

Quality and risk control that scales:

• Insist on a documented QMS such as ISO 9001; if you’re in medical, require ISO 13485 for stronger traceability and risk management.

• Use FAI to lock the process, then evolve to PPAP‑style controls for serial production as needed (process flows, control plans, capability studies).

• Maintain traceability back to material heats, finishing lots, and inspection records. It pays off when audits and field returns knock.

One‑stop prototype‑to‑production in practice:

• Micro‑example: In a recent NPI for a handheld device housing, the team sourced 6063 for an anodized extrusion, rough‑cut profiles, CNC‑finished the interface features in 6061 test coupons to de‑risk tolerances, and pre‑booked Type II anodizing capacity while first articles were measured. A single coordinator handled CAD changes, extrusion die tuning, CNC fixtures, and finishing work orders, which prevented handoff loss and kept the builds aligned. The example reflects a typical one‑stop workflow many suppliers can execute; the lesson is that integrated scheduling across forming, machining, finishing, and inspection reduces iteration time and requalification risk.

You don’t need to memorize the entire aluminum universe to ship good parts. You do need a tight drawing that reflects real process windows, a forming route matched to volume and geometry, and a finishing and inspection plan that protects the spec all the way to the dock. Ready to review a current design against this aluminum processing guide? Start with the forming decision, mark your critical‑to‑quality features, and align the finish—then let’s dig in to the machining plan.