Choosing the right manufacturing process is an important step in controlling production costs, meeting quality requirements, and ensuring reliable delivery. For custom metal components, CNC machining and die casting are two widely used options, particularly for aluminum parts, industrial housings, brackets, and precision mechanical components.
However, neither process is the best choice for every application. The right solution depends on part geometry, material requirements, dimensional tolerances, production volume, tooling investment, and the expected product lifecycle.
In this guide, we explain the key differences between CNC machining and die casting to help engineers, product designers, and purchasing teams make more informed manufacturing decisions.
CNC (Computer Numerical Control) machining is a subtractive manufacturing process. Computer-controlled cutting tools remove material from a solid workpiece, such as an aluminum block, steel bar, brass stock, or engineering plastic, to produce the required shape.
Common CNC operations include milling, turning, drilling, boring, and tapping.
Design flexibility: Suitable for prototypes, customized components, and parts with complex machined features.
No dedicated die-casting mold required: This reduces initial tooling investment and makes design revisions easier.
Dimensional control: Critical bores, mating surfaces, threads, and other functional features can be machined to specified tolerances.
Material versatility: CNC machining can process a wide range of metals and engineering plastics, subject to equipment and tooling capabilities.
CNC machining removes material from a starting workpiece, which can create significant material waste when producing complex shapes. Machining time may also increase with deep pockets, intricate features, demanding tolerances, or extensive finishing requirements.
For these reasons, CNC machining is often attractive for prototypes, low-to-medium-volume orders, and components requiring specific precision features.
Die casting is a manufacturing process in which molten metal is injected under pressure into a reusable metal mold, commonly called a die. After the metal solidifies, the component is removed and prepared for subsequent operations if required.
High-pressure die casting is widely used for suitable non-ferrous alloys, particularly aluminum, zinc, and magnesium alloys.
Efficient repeat production: Once the tooling is ready and the process is established, components can be produced repeatedly at relatively high output rates.
Complex geometries: Ribs, bosses, mounting features, and other details can often be incorporated into the molded shape.
Reduced material removal: Near-net-shape production can reduce the amount of material that must be machined away.
Potentially lower unit costs at volume: Initial tooling costs can be distributed across a sufficiently large production quantity.
Die casting requires an upfront investment in tooling, and mold design and manufacture add time before production can begin. Design changes after tooling completion may involve additional cost and lead time.
The process also has material and design constraints. Mold filling, solidification, porosity risk, draft angles, wall thickness, and dimensional requirements must be considered during product development.
Die casting is therefore particularly worth evaluating for stable designs with recurring or higher-volume demand.
| Factor | CNC Machining | Die Casting |
|---|---|---|
| Manufacturing method | Material removal | Molten metal formed in a die |
| Initial tooling | No dedicated casting die required | Dedicated die required |
| Design changes | Generally easier to implement | May require die modification |
| Production volume | Often attractive for prototypes and smaller batches | Often attractive for repeat and higher-volume production |
| Material selection | Broad range of machinable materials | Primarily suitable non-ferrous casting alloys |
| Complex molded features | May require multiple machining operations | Ribs and bosses can often be integrated into the casting |
| Critical tolerances | Machined features can meet specified precision requirements | Critical features may require secondary machining |
| Cost structure | Driven by material, machining time, setup, and finishing | Driven by tooling, casting cycle, finishing, and production volume |
Important: These are general tendencies, not absolute rules. Actual costs and achievable tolerances depend on the part design, material, equipment, tooling, quality requirements, and supplier capabilities.
The lowest unit price does not always mean the lowest total manufacturing cost.
For CNC machining, major cost drivers include material consumption, machine time, setup, tooling, inspection, and surface finishing.
For die casting, the total cost also includes mold design, mold manufacture, sampling, validation, maintenance, and any secondary machining or finishing.
A useful way to compare the options is to calculate the total expected cost:
Total manufacturing cost = Initial tooling and setup + Production costs + Inspection and finishing costs + Other project-specific costs
The unit cost can then be estimated by dividing the total cost by the number of accepted parts, while accounting for scrap, rework, and other relevant expenses.
CNC machining may be preferable when:
You need a prototype or a small initial quantity.
The design is still being developed.
The component requires several precise machined features.
You need to avoid a large upfront tooling commitment.
Material options outside the usual die-casting alloys are required.
Die casting may be preferable when:
The design is stable and expected to remain unchanged.
Demand is recurring or sufficiently high to justify tooling.
The component has complex features that can be integrated into the mold.
The selected alloy and part geometry are suitable for die casting.
Production efficiency and repeatability are important priorities.
There is no universal quantity at which die casting becomes cheaper than CNC machining. The break-even point must be calculated using the actual drawing, quotation, tooling cost, and expected demand.
Yes. In many projects, combining the two processes is a practical solution.
A component can first be die-cast to produce its overall shape. CNC machining can then be used to finish critical bores, threaded holes, mounting surfaces, sealing faces, or other features requiring tighter dimensional control.
This approach can combine the production efficiency of casting with the precision of machining where it matters.
For example, an aluminum equipment housing may be die-cast with integrated ribs and mounting bosses. Selected holes and mating surfaces can then be CNC-machined to meet the assembly requirements.
The appropriate manufacturing route should be determined by the functional requirements of the finished part, rather than by choosing a process in isolation.
To help a manufacturer assess the most suitable process, provide the following information whenever possible:
Technical drawings or 3D CAD files: Include dimensions, critical tolerances, and relevant geometric requirements.
Material specification: Identify the required alloy or material grade where specified.
Surface finish requirements: State any requirements for anodizing, plating, powder coating, painting, or other treatments.
Order quantity: Include prototype quantity, initial order quantity, and estimated annual demand if available.
Quality requirements: Identify critical dimensions, inspection requirements, material documentation, and any applicable industry standards.
Project timing: Provide the target date for samples and production delivery.
With this information, a manufacturing supplier can evaluate process feasibility, tooling requirements, secondary operations, and potential cost-saving opportunities.
CNC machining and die casting serve different manufacturing needs. CNC machining offers flexibility, broad material options, and precise control of machined features. Die casting can offer efficient repeat production and complex near-net-shape components when the design and alloy are suitable.
For some projects, a combined approach delivers the best balance of cost, precision, and production efficiency.
The key is to evaluate the finished component, expected production volume, quality requirements, and total project cost before committing to a manufacturing process.
Looking for a manufacturing partner for your custom metal components? Share your technical drawings, material requirements, and estimated quantity with CPRMFG for a manufacturing review and quotation.
Neither process is universally better. CNC machining is often suitable for prototypes, smaller batches, and precision features, while die casting is often suitable for stable designs and higher-volume production.
It can be at higher production volumes because tooling costs are spread across more parts. However, the result depends on the component design, tooling investment, machining requirements, and actual order quantity.
Yes. Selected features, such as holes, threads, and mating surfaces, can be machined after casting when the design and material are suitable.
Technical drawings or CAD files, material specifications, surface finish requirements, order quantities, tolerances, and quality requirements help a manufacturer prepare a more accurate quotation.
