What is the Difference Between Sheet Metal and Machined Parts?

In the world of CNC machining and manufacturing, sheet metal parts and machined parts are two indispensable component types. Yet, they vary greatly across multiple dimensions. Whether you operate in the automotive, aerospace, electronics, or any other industry that demands precision parts, grasping these differences is vital for choosing the optimal processing method for your projects. Below, we’ll break down their key distinctions from 7 core perspectives to help you make informed decisions.

Sheet Metal Parts

Sheet metal parts are fabricated from thin, flat metal sheets, with a typical thickness ranging from 0.01mm to 6mm (slightly thicker sheets may be used for special industrial needs). The core of their manufacturing process lies in shaping the metal sheets without significantly altering the material’s thickness.

Common materials for sheet metal parts include aluminum, steel (carbon steel, stainless steel), copper, and brass. Thanks to their lightweight properties, high structural strength, and cost advantages in mass production, sheet metal parts are a staple in countless industries.

Machined Parts

Machined parts are produced through subtractive manufacturing: material is removed from a solid metal block (called a “workpiece” or “stock”) using CNC machining tools like lathes, mills, drills, and grinders. This material-removal process enables the creation of complex shapes and ultra-high-precision dimensions.

A broad range of metals can be used for machined parts, such as aluminum, steel, titanium, magnesium, and various alloys. They are primarily used in applications requiring strict tolerances, intricate geometries, and superior surface quality—think medical devices, aerospace components, and high-performance automotive parts.

Sheet Metal Processing Technologies

Sheet metal processing revolves around bending, cutting, and assembling flat metal sheets. Key techniques include:

●  Shearing: A shearing machine cuts metal sheets into the required size and shape, ideal for simple flat parts (e.g., metal panels for electronic enclosures).

●  Bending: A bending machine shapes sheets into specific angles, used to make brackets, frames, and enclosure edges.

●  Punching: A punch press creates holes, slots, or custom shapes in sheets using specialized dies, suitable for parts needing repeated cutouts (e.g., vent holes in chassis).

●  Welding: Techniques like MIG welding, TIG welding, or spot welding join multiple sheet metal components to form complex structures (e.g., car body frames).

●  Stamping: A stamping press applies pressure to form sheets into 3D shapes, perfect for high-volume production (e.g., aluminum cans, appliance parts).

Machined Processing Technologies

Machined processing relies on removing material to achieve the desired form. Common methods include:

●  Milling: A rotating cutting tool removes material from the workpiece, capable of creating flat surfaces, slots, grooves, and complex 3D shapes (e.g., engine blocks, custom brackets).

●  Turning: A lathe spins the workpiece while a cutting tool moves along its axis, used to produce cylindrical parts (e.g., shafts, bolts, nuts).

●  Drilling: A drill press creates holes of various sizes and depths, a foundational step for parts needing fastener holes (e.g., machine components).

●  Grinding: A grinding machine removes a tiny amount of material to refine surface finish and dimensional accuracy, critical for high-precision parts (e.g., medical instrument components).

●  EDM (Electrical Discharge Machining): Electrical discharges erode material from the workpiece, ideal for hard metals (e.g., tungsten) and complex shapes that traditional tools can’t handle (e.g., mold cavities).

The right material depends on the processing method—sheet metal and machined parts have distinct material needs.

Sheet Metal Parts

●  Structure: Typically simple, focusing on flat surfaces, straight edges, and basic bends. Complex 3D shapes or internal cavities are rare (due to processing limitations).

●  Assembly: Can be combined into complex structures via welding, riveting, or screwing (e.g., a welded sheet metal cabinet).

●  Thickness & Finish: Uniform thickness; surface finish depends on the original material (e.g., polished aluminum sheets) and processing steps (e.g., painted or galvanized surfaces).

Machined Parts

●  Structure: Highly flexible—can feature complex 3D shapes, internal cavities, and precise details (e.g., threads, grooves, or tapered surfaces).

●  Accuracy: Subtractive manufacturing enables tight tolerances (often down to ±0.001mm) for critical applications.

●  Finish: Surface quality can be enhanced via grinding, polishing, or coating (e.g., anodizing for aluminum machined parts).

Sheet Metal Parts: Cost-Effective for Mass Production

Sheet metal parts shine in industries needing high-volume, lightweight components:

●  Automotive: Car bodies, doors, hoods, and radiator supports.

●  Electronics: Enclosures for computers, servers, and industrial control panels; heat sinks for LEDs.

●  Aerospace: Aircraft fuselage panels, wing ribs (using high-strength aluminum or titanium alloys).

●  Construction: Roofing panels, wall cladding, and HVAC ductwork.

Machined Parts: Precision for Critical Applications

Machined parts are essential where accuracy and complexity matter most:

●  Medical Devices: Surgical instruments (e.g., scalpels), orthopedic implants (e.g., hip replacements), and diagnostic equipment components.

●  Aerospace: Aircraft engine turbines, landing gear components, and avionics parts (require extreme precision and durability).

●  Automotive: Engine crankshafts, transmission gears, and fuel injection system parts.

●  Tool & Die: Molds for plastic injection, stamping dies, and custom machining fixtures.

Sheet Metal Parts: Lower Cost for High Volume

●  Material Cost: Thin metal sheets are cheaper than solid metal blocks; less material waste (since processing doesn’t remove much material).

●  Production Efficiency: Stamping, bending, and shearing are fast—ideal for mass production (10,000+ units), reducing labor per part.

●  Equipment Cost: Shearing machines and bending presses have lower initial investment than CNC mills or lathes.

Note: Costs rise for complex shapes (e.g., custom stamping dies) or tight tolerances; small-batch production may be less cost-effective.

Machined Parts: Higher Cost, But Flexible for Small Batches

●  Material Cost: Solid metal blocks are more expensive; significant material waste (up to 50% for complex parts).

●  Production Efficiency: Machining is slower—each part may take minutes to hours to produce, increasing labor costs.

●  Equipment Cost: CNC machining centers are costly (often $50,000+), raising fixed costs.

Note: Large-batch production (1,000+ units) spreads equipment/tooling costs, lowering unit prices; small-batch or custom parts avoid expensive tooling (unlike sheet metal stamping).

Follow these 4 steps to pick the right method for your project:

1.  Clarify Project Requirements

     Choose sheet metal if you need simple shapes, lightweight parts, or high-volume production (e.g., 10,000+ electronic enclosures).

     Choose machined parts if you need complex geometries, tight tolerances (±0.005mm or better), or high surface quality (e.g., medical implants).

2. Select the Right Material

     Prioritize ductility/formability (aluminum, low-carbon steel) for sheet metal.

     Prioritize machinability (aluminum, low-carbon steel) or specialized properties (titanium for corrosion resistance) for machined parts.

3. Consider Production Volume

     High volume (1,000+ units): Sheet metal is more cost-effective (fast processing, low material waste).  

     Small batch (1–100 units): Machined parts save money (no need for custom dies/stamps).

4. Align with Budget

     If cost is a top concern and shapes are simple: Sheet metal.

     If precision/complexity is non-negotiable: Machined parts (factor in material waste and longer lead times).

Sheet metal parts and machined parts each have unique strengths—sheet metal excels at affordability and mass production, while machined parts deliver precision and complexity. By understanding their differences in definition, processing, materials, structure, applications, and cost, you can select the optimal method for your project.

If you’re still unsure which option fits your needs, or if you require custom CNC machining or sheet metal fabrication services, our team of experienced engineers is here to help. Contact us today for a free consultation and tailored solutions to meet your industry-specific requirements.