What is the difference between CNC and die casting?

Manufacturers face a critical choice when producing metal parts or components. Should you machine parts from solid blocks or cast molten metal? Both CNC machining and die casting give precision results, yet they work fundamentally differently.

CNC machining cuts and drills material in a controlled way to remove it. Die casting puts liquid metal into molds that can be used again and again under pressure. The choice depends on your intended application and features.

STEP does both processes in-house. Our 58 CNC machines can work with a variety of materials and achieve a precision of 0.005mm. We also have three aluminum die casting machines that can make 500,000 pieces a day. This dual capability means you can get expert advice on the best way to save money.

The choice you make will affect your production schedule, unit costs, and design options. Knowing how each process works helps you make smart choices. Let's look at how these two methods stack up against each other on important points.

What is CNC Machining?

CNC machining is a type of subtractive manufacturing that takes material away from solid blocks. Computer-controlled tools cut, drill, and shape metal into exact parts. The technology uses digital instructions to make parts with excellent accuracy.

The process starts by uploading a CAD design file. Then, without manual intervention, machines automatically move along multiple axes according to their programming. Cutting tools take off unwanted material layer by layer until the job is done.

CNC machining is optimum for complicated shapes that need tight tolerances and features inside. This method is often used for medical devices, parts for airplanes, and precision instruments. It makes sure that every piece is always of the same high quality.

How CNC Machining Process Works

Loading the Design File

First, you put your CAD drawing into the CNC software system. The program automatically turns 3D models into G-code instructions that machines can read. This code tells the machine exactly where to go and cut.

Setting Up Raw Material

Operators use vices or fixtures on the machine table to hold metal stock in place. If you clamp metal blocks down correctly, they won't move during the high-speed cutting that comes next. For the process to be accurate, the workpiece must stay completely still.

Alignment tools set zero points that exactly match the reference coordinates in your design. This setup phase decides where the machine will start cutting. Correct positioning makes sure that every dimension is exactly what is needed.

Executing Cutting Operations

Cutting tools move along programmed paths at 1000s of revolutions per minute. The machine moves several axes at once to make complicated 3D shapes. The material is taken off in layers until your part comes out of stock.

During operation, machining centers automatically switch between drills, mills, and taps. Coolant keeps chips from building up and keeps the heat in check at the cutting zones.

Final Inspection Process

After machining is done, operators use precise tools to measure critical dimensions. Calipers, micrometers, and coordinate measuring machines check that features meet tolerances. Every part is carefully inspected against the exact specifications you gave.

Today, automatic imaging equipment scans complicated shapes to check for dimensional accuracy. Before parts move on to the next stage, quality control systems find any flaws.

Where CNC Machining is Used?

Aerospace and Aviation Components

For safety-critical uses, aircraft parts need to be highly precise and reliable. CNC machining makes parts for engines, landing gear, and structural brackets. Aluminum and titanium are lightweight materials that are perfect for aerospace needs.

Medical Devices

For patient safety, surgical tools need to be made of materials that are safe for the body and have precise dimensions. CNC machining makes parts for implants, prosthetics, and diagnostic equipment with great accuracy. Stainless steel and titanium alloys are shaped into medical tools that save lives.

Automotive Industry

CNC precision machining is used for engine parts, transmission parts, and chassis parts. Machine custom brackets, housings, and mounting hardware to different specifications. Vehicles with high performance especially benefit from tight tolerance capabilities that make sure they work.

Consumer Electronics and Products

CNC machining is used for electronic device housings, heat sinks, and connectors with details. Aluminum cases for smartphones and tablets need to be the same size every time. Specifications for shielding components keep sensitive electronics safe from electromagnetic interference.

When to Choose CNC Machining

CNC machining is an ideal choice for projects that need fewer than 10,000 units because it is economical and efficient. You don't have to spend a lot of money on tools that large-scale processes need right away. The cost of programming is still low, so small batches and prototypes can be made without breaking the bank. No matter how many parts are made, each one costs about the same. This predictable pricing makes it easier to plan your budget for custom parts.

If your design has internal threads, deep holes, or cavities, choose CNC machining. It can get to places that casting or forming can't reach as well. Multi-axis machines make complex shapes out of solid blocks of material with great accuracy. Tight internal tolerances and precise positioning make CNC capabilities much better. You can get exact measurements for things like bored holes and tapped threads.

What is Die Casting?

Die casting puts hot metal into steel molds under a lot of pressure. The liquid fills in all the details of the cavities, giving your part its shape. Metal hardens quickly, so finished parts are always ready in seconds or minutes.

This method makes complicated shapes on the outside in one step. Without putting anything together, fine details, thin walls, and complex shapes all come together at the same time. Steel molds can make the same parts over and over again for thousands of cycles.

Die casting works best with alloys composed of aluminum, zinc, and magnesium. When these metals are melted, they flow easily and harden with great detail. The process works well to make parts that are strong but light for a variety of industries.

Die casting is optimum for making a lot of things at once, where the cost of the tools is spread out over many units. The initial cost of the mold is high, but the cost per piece goes down a lot when you buy more. This method is economical for production runs of more than 10,000 pieces.

How Die Casting Works

Melting the Metal

In a furnace, manufacturers heat metal alloys until they are completely liquid. To be worked with, aluminum usually melts at about 660 degrees Celsius. For the best flow properties, the molten metal needs to be at the right temperature.

Injecting Into the Mould

A hydraulic system pushes molten metal into the steel die with a lot of pressure. Injection speeds can reach several meters per second, which fills cavities almost right away. High pressure makes sure that the material gets to the thin parts and small details all the way through.

Cooling and Solidification

As soon as metal reaches the cooler steel mold surfaces, it starts to harden. Cooling channels in the die take away heat, which speeds up the process of solidifying. Depending on the part size, cycle times can range from a few seconds to a few minutes.

If you cool something down properly, it won't warp, become porous, or develop internal stresses. Thicker parts need more time to cool than parts that are thinner.

Taking Out the Finished Part

When the metal has completely hardened inside, the die opens on its own. Ejector pins push the finished part out of the mold cavity. The part comes out cleanly, so it can be trimmed or used for other purposes if needed.

Where Die Casting is Used

Automotive Industry Components

Die casting makes engine blocks, transmission housings, and structural brackets for cars and trucks. Aluminum alloys make cars stronger while also making them much lighter. Die casting is used a lot in parts of the fuel system, steering system, and wheel hubs.

Consumer Electronics Housing

Die-cast aluminum is used to make the housings for smartphones, laptops, and tablets. The process naturally makes thin-walled housings that are great at letting heat escape. In one step, precise details like mounting bosses and connector openings are made.

Household Appliances

Die casting is used to make parts for washing machines, refrigerators, and air conditioners. Aluminum construction methods that are light but strong are good for the bodies of kitchen appliances. Die casting is used to make the cases for small appliances like coffee makers, blenders, and mixers.

Tools and Equipment for Industry

Die-cast parts are used in power tool housings for drills, saws, and grinders. The material is light enough for comfort but strong enough to resist vibration and impact. Motor housings and gear cases keep the parts inside safe in tough conditions.

When to Choose Die Casting?

Die casting suits high-volume production runs exceeding 10,000 units annually. The substantial mould investment only makes financial sense with large quantities. Per-unit costs drop dramatically as production volume increases across thousands of pieces.

Choose die casting when your design features complex external shapes and contours. Thin walls, intricate details, and lightweight construction favour this manufacturing method. The process creates near-net-shape parts requiring minimal secondary machining operations afterward.

Projects requiring fast cycle times benefit from die casting's rapid production capabilities. Components form in seconds to minutes, allowing hundreds of thousands of pieces. Consistent repeatability ensures every part matches specifications across entire production runs.

Get Both Capabilities Under One Roof

No need to work with multiple suppliers. STEP's integrated facility gives you access to precision CNC machining and high-volume die casting, ensuring faster timelines and seamless production from prototype to mass manufacturing.