How to Select the Right Custom Metal Parts Manufacturing Method

If you’re developing a new product, working on a limited production run, or require metal parts with tight tolerances and non-standard dimensions. It's likely you'll have to turn to custom metal parts manufacturing.

But choosing a custom metal fabrication method can be tricky. Especially when balancing costs, precision, and production speed. In this article, we’ll explore the key custom metal parts manufacturing methods, helping you find the best approach for your project.

What Is Custom Metal Parts Manufacturing?

Standard components fall short when companies require parts with tight tolerances, intricate designs, or materials capable of surviving extreme conditions. It's oftentimes in these situations that businesses turn to custom metal parts manufacturing.

In essence, custom metal parts manufacturing is a subset of custom manufacturing. But the concept is focusing entirely on metal components. Due to the nature of the complexity of the product, the production requires a high level of flexibility, customisation, and quality level.

How Do You Manufacture Metal Parts?

The way metal parts are created in custom metal fabrication greatly varies depending on which process you choose. There truly is no one-size-fits-all approach. Each manufacturing method for metals comes with its own advantages and trade-offs. Below we´ll give you the key information of each main method.

Method	How It Works	Use Cases	Advantages	Limitations
CNC Machining Services	Material is removed from a solid block using precise cutting tools controlled by computer programs (CNC).	High-precision parts, complex geometries, and low-to-medium production volumes.	High precision, flexibility with materials, quick prototyping.	High cost for small runs, material waste.
Metal Casting Services	Molten metal is poured into a mold and cooled to form a solid part. Common techniques include sand casting and investment casting.	Producing complex shapes and high-volume parts with intricate details.	Cost-effective for high volumes, suitable for intricate designs.	Longer lead times, limited precision for tight tolerances.
Metal 3D Printing Services	Layer-by-layer fabrication of parts using powdered metal and a laser or binder system.	Prototyping, low-volume production, and complex geometries that are difficult with traditional methods.	Low waste, rapid production, all-in-one assemblies.	Higher material costs, limited scalability for large volumes.
Forging Sevices	Heated metal is shaped using compressive forces, often through hammering or pressing.	High-strength components that require durability and resistance to wear.	Produces extremely strong parts, low material waste.	Less suited for complex geometries, high upfront tooling costs.
Sheet Metal Fabrication and Stamping Services	Metal sheets are cut, bent, or stamped into desired shapes.	High-volume production of lightweight parts and enclosures.	Fast production for large quantities, cost-effective for simple designs.	Limited to parts with thin profiles, high tooling costs.
Extrusion	Heated metal is forced through a die to create long shapes with consistent cross-sections.	Long, uniform parts with simple cross-sectional shapes.	Cost-effective for uniform profiles, strong finished products.	Limited to specific shapes, requires additional machining for detailed features.
Metal Injection Molding (MIM)	Metal powder mixed with a binder is injected into molds and sintered to form the final product.	Small, complex parts require high precision in large quantities.	Cost-effective for high-volume production, precise details.	Not suitable for large parts, higher initial tooling costs.

 

1. CNC Milling and CNC Turning

CNC machining is a core process in custom metal manufacturing. It's praised for its precision, versatility and ability to handle complex designs. Within CNC machining, the two main techniques are CNC milling and turning. While both are used to create precise parts, they take different approaches to achieve this goal.

CNC Milling Machining

CNC milling focuses on shaping parts by cutting away material from a solid block. The CNC milling process begins with a CAD model. This CAD model acts as a digital blueprint. It's then converted into a G-code, a sort of programming language. This programming language guide the machine on the exact movements and actions to take.

Once the material is secured on the milling machine’s table, a high-speed rotary cutting tool moves across multiple axes.

The way the machining works can differ depending on the axis:

• 3-Axis CNC Milling Machines: Moves the cutting tool along the X, Y, and Z axes to shape parts with basic geometries.
• 4-Axis CNC Milling Machines: Adds one rotational axis (A, B, or C) to the standard three, allowing machining of curved surfaces or multiple faces parts without repositioning.
• 5-Axis CNC Milling Machinery: Includes two rotational axes of any combination of A, B or C to approach the part from different angles.

Advanced machines can also rotate the tool or table to handle additional axes, allowing for more complex geometries. The rotary cutting tool carves out the desired shape with micrometer-level precision. After the cutting is complete. The completed part may undergo post-processing steps. For example, deburring, polishing, or coating processes.

CNC Turning Machining

While CNC milling uses a rotating cutting tool to shape a solid block. You could say that the CNC works in the opposite way. Instead, the workpiece rotates while the cutting tool remains in place. The whole process starts with a cylindrical bar of material. This bar is mounted on a lathe and spins at a high speed, while a cutting tool removes material layer by layer. Until it has shaped the workpiece into its final form.

Modern CNC lathes use advanced programming and multi-axis capabilities to add features like threading, drilling, and even minor milling without needing additional setups.

When Should You Consider CNC Turning and Milling?

CNC turning is appropriate when your components have tight tolerances and smooth finishes. It is the choice for creating cylindrical parts and components with rotational symmetry. For example shafts, bushings, and flanges.

Meanwhile, CNC milling excels at handling multi-faceted designs and irregular shapes. Therefore, it's ideal for applications that require tight tolerances and complex geometries. It's also suitable for features such as flat surfaces, angled cuts, slots, pockets.

 

2. Extrusion

Extrusion is known for its ability to produce components with consistent cross-sectional shapes. It works by forcing heated material, such as plastic or metal, through a die that shapes it into the desired profile.

There are three main types of extrusion:

• Hot extrusion: Uses high temperatures to make the material easier to shape. Ideal manufacturing method for metals like aluminum or magnesium.
• Cold extrusion: Performed at room temperature and produces stronger parts with tighter tolerances. Suitable for precision steel components.
• Friction extrusion: Takes a different approach, relying on mechanical force rather than heat, which helps preserve material properties.

Once the material exits the die, it’s cooled and, for metal parts, often undergoes finishing steps like machining or drilling to meet exact specifications.

When Should You Consider Extrusion?

Extrusion is ideal for parts with cross-sectional profiles, such as pipes, tubes and frames. It is particularly beneficial when you need to produce high volumes of components that require strength and precision and is versatile in handling various materials, from lightweight aluminum to robust steel and even plastics.

3. Casting

Casting is one of the oldest ways to manufacture metal parts. The casting process starts by pouring liquid metal into a mold, which gives the part its shape. The mold is then removed once the metal cools and hardens, leaving behind a finished part.

If you’re new to the process, you can explore how custom manufacturing works for a broader overview. In essence, there are two primary types of casting: sand casting and investment casting.

Sand Casting

Sand casting starts by forming packed sand around a pattern to create a mold in the shape of the desired part. The molten metal is then poured into the mold, filling the cavity and taking its form as it cools and solidifies. Once the metal forms, the mold is broken apart to release the part.

Investment Casting

Also called lost-wax casting, creates metal parts by coating a wax model in ceramic to form a mold. Once the wax is hardened, molten metal is poured in and left to cool and then separated from the mold. Once the part is removed from the mold, it may undergo additional processes such as polishing, machining, or heat treatment to meet final specifications.

 

When Should You Consider Casting?

Casting is a great choice when your project requires complex designs. For example, internal cavities or intricate shapes that are hard to achieve with machining or extrusion. It’s particularly effective for medium- to high-volume production of strong materials like stainless steel or brass.

5. Metal Injection Molding

Metal injection molding is a process whereby finely-powdered metal is mixed with polymers to produce a feedstock mix. This mix is then liquified and injected into injection molding machines to mold it into the desired shape.

The molded part, referred to as the “green part”, is cooled down and removed from the mold. It's followed by a few more steps. First, it undergoes a debinding process to remove the polymer binder. This process leaves behind a fragile metal skeleton known as the “brown part.” Next it's followed by sintering, where the brown part is placed in a high-temperature furnace. The metal particles fuse together, densifying the structure and shrinking the part to its final dimensions.

The final product may then undergo additional treatments, such as machining or heat treatment, to meet exact specifications or achieve surface finishes.

When Should You Consider Metal Injection Molding?

Metal injection molding is suited for producing small parts with fine details, complex parts with tight tolerances. Specifically, it can achieve dimensional tolerances of between ±0.3% to ±0.5% of the nominal dimension. It is much more cost-effective than other methods, as it can mass-produce the parts and subsequently offer lower per-unit costs.

6. Forging

Forging uses compression forces and heat to shape the custom metal part into the desired form. The process is straightforward and follows five steps. First the metal is heated to a malleable state. Then it undergoes the initial shaping to create an outline of the part. This is followed by a precision forging pressure which defines the final shape. After it's been cooled to solidify its shape, it undergoes finishing processes. Including machining, polishing to refine the surfaces and reassure that the part meets the exact specifications.

When Should You Consider Forging?

Even though forging can't achieve the tighter tolerance levels of machining, it stands out in its ability to deliver metal parts with a high structural integrity and strength. In particular, the process helps to align the metal´s grain structure with the shape of the part so that it can withstand high stress, heavy loads and extreme operating conditions. Making it the ideal choice for components like gears and connecting rods that requires high mechanical properties.

7. Sheet Metal and Stamping

Sheet metal fabrication cuts, bends or press flat sheet metal into the desired shape using so-called “stamping presses”.  The stamping presses use high pressure to shape the sheet metal into the desired shape by using punching, blanking, bending, coining, embossing and flanging stamping techniques. After the stamping process, the parts may undergo finishing processes such as anodizing, painting, or powder coating for improved performance and appearance.

When Should You Consider Stamping?

The stamping process is ideal for large-scale production that requires faster production times and lower costs with consistency, as it has uniform shapes or multiple repeating features. The method excels when you need components with moderate tolerances, lightweight designs, and strong structural integrity.

8. Metal 3D Printing

Metal 3D printing is an additive manufacturing process. Meaning that it builds parts layer by layer from metal powders. The 3D printer begins by following a CAD model, which provides the blueprint for the part. Using techniques like direct metal laser sintering (DMLS) or electron beam melting (EBM), the printer fuses each layer of metal powder with precision. The process continues layer by layer until the final part is formed. There may be additional steps after printing. For example, stress relief, machining, or surface finishing to ensure it meet exact specifications.

When Should You Consider Metal 3D Printing?

Metal 3D printing can be used as a substitute for low-volume casting, and is often used for experimentation, prototype or shorter production runs, as it is not as scalable as the other methods mentioned in this article.

Frequently Asked Questions (FAQ)

What Is the Difference Between CNC Machining and Sheet Metal Fabrication?

CNC machining uses subtractive processes to shape parts from solid material, achieving high precision and tight tolerances, making it ideal for complex geometries and small batches. In contrast, sheet metal fabrication involves cutting, bending, and shaping flat sheets, offering cost efficiency for large-scale production of lightweight, uniform parts.

How Expensive is Sheet Metal Fabrication?

Sheet metal fabrication offers cost efficiency. Particularly for high-volume production, with expenses influenced by material selection, design complexity, and batch size. While it’s ideal for producing simple, uniform parts in bulk, smaller runs or intricate designs with tight tolerances might be better suited to precision-focused methods like CNC machining or 3D printing.

Conclusion: Selecting the Right Method for Custom Metal Parts Manufacturing

There are many manufacturing methods used in custom and small metal parts manufacturing. In this article, we've outlined some of the key ones. From high precision CNC machining, to the oldest way to manufacture metal parts by casting. Each metal parts fabrication method comes with its advantages and disadvantages.

No matter which method you choose, comparing quotations from multiple suppliers is important because costs can vary drastically. Use our free custom manufacturing RFQ tool to submit your requirements to over 700,000 manufacturers and receive same-day proposals.