{"id":7926,"date":"2022-09-29T01:00:00","date_gmt":"2022-09-29T08:00:00","guid":{"rendered":"https:\/\/www.fictiv.com\/?post_type=cpt_blog&p=7926"},"modified":"2026-03-15T22:53:54","modified_gmt":"2026-03-16T05:53:54","slug":"casting-vs-cnc-machining","status":"publish","type":"cpt_blog","link":"https:\/\/www.fictiv.com\/articles\/casting-vs-cnc-machining","title":{"rendered":"Casting vs. CNC Machining: How to Choose the Right Process for Your Part?"},"content":{"rendered":"\n

We\u2019re no longer in the Bronze Age, but some manufacturing techniques stand the test of time. Casting, a process where molten metal is poured into a mold, has existed for over 6,000 years and is still prominently used in manufacturing to this day. Advances in technology enable the casting of high-quality parts with tight tolerances\u2014not unlike CNC machining<\/a>, a newer manufacturing method that\u2019s also frequently used. <\/p>\n\n\n\n

Casting and CNC machining are both common manufacturing processes for metal parts, but they differ significantly in tooling cost, production volume, precision, and scalability. While CNC machining is typically best for prototyping and low-volume production due to its fast setup and tight tolerances, die casting becomes more cost-effective at higher volumes where tooling investment can be amortized. <\/p>\n\n\n\n

But have you ever considered CNC machining a part that you usually cast? Or are you considering which method is best to manufacture your design at higher volumes? This guide compares both processes across geometry, materials, cost, and break-even volume to help you determine the best option for your part.<\/p>\n\n\n\n

What Is Casting?<\/strong><\/h2>\n\n\n\n
\"Casting<\/figure>\n\n\n\n

Casting is considered a formative manufacturing process that uses molds to make parts. While multiple metal casting methods exist\u2014including sand casting, investment casting, and permanent mold casting\u2014this article focuses primarily on die casting versus CNC machining, since die casting is typically the preferred casting method for high-volume production.<\/p>\n\n\n\n

Other casting processes may be mentioned for context, but the economic and lead time comparisons throughout this article center on die casting.<\/p>\n\n\n\n

Die Casting<\/strong><\/h3>\n\n\n\n

In metal casting, molten metal is poured or injected into a pre-made mold. Cores or inserts may be added when complex internal geometries and cavities are required. Die casting<\/a> is a specific type of casting that uses pressure to force the molten metal into the mold. The pressures used in high-pressure die casting are significantly higher than those in low-pressure die casting.<\/p>\n\n\n\n

Once the part cools and solidifies, it\u2019s cleaned and processed to achieve the desired surface finish. Secondary operations may include CNC machining to hit even tighter tolerances, or removing other undesirable features from the die casting process, such as flash. Other deflashing methods include grinding, cryogenic freezing, and tumbling.<\/p>\n\n\n\n

\"material
This gym weight is an example of a cast metal part<\/figcaption><\/figure>\n\n\n\n

Train wheels, bus pedals, turbine blades, and engine blocks are common examples of die-cast parts. Cast parts are used in almost every industry, including automotive<\/a>, aerospace<\/a>, consumer products<\/a>, and medical devices<\/a>.<\/p>\n\n\n\n

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To learn more about part design for the die casting process, download our die casting design guide<\/a>.<\/p>\n<\/div><\/div>\n\n\n\n

<\/p>\n\n\n\n

What Is CNC Machining?<\/strong><\/h2>\n\n\n\n

CNC machining<\/a> is a subtractive manufacturing method that uses a cutting tool to remove material and achieve the desired geometry. A computer program using G-code<\/a> tells the machine where to move and how to cut.<\/p>\n\n\n\n

\"CNC<\/figure>\n\n\n\n

<\/p>\n\n\n\n

CNC-machined parts are everywhere. Metal laptop enclosures, small components inside cell phones, aerospace, and automotive parts, fixtures, and jigs\u2014even casting molds are manufactured using CNC machining.<\/p>\n\n\n\n

Choosing Between CNC and Casting<\/strong><\/h2>\n\n\n\n

When designing a part, there are two common approaches to determine a manufacturing method to make the part (CNC vs casting): <\/p>\n\n\n\n

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  1. Design engineers often start with a manufacturing method in mind, so the design is realistic, manufacturable, and well-suited to that process. <\/li>\n\n\n\n
  2. A part’s function may require a specific size, shape, or geometry that dictates the manufacturing process. CNC machining and die-casting are each best suited to particular geometries.<\/li>\n<\/ol>\n\n\n\n
    \"table\"
    Table 1: Comparison of Best-Suited Geometries for Die Casting and CNC Machining
    <\/figcaption><\/figure>\n\n\n\n

    <\/p>\n\n\n\n

    Casting vs CNC Machining: Choosing Based On Part Geometry<\/strong><\/h3>\n\n\n\n

    Choosing the correct manufacturing technique starts with considering the part geometry. Designs that require a large amount of material removal\u2014for example, hollow parts with thin walls and large cavities\u2014can be time-consuming and create excessive waste, making them strong candidates for casting. Complex geometries<\/a>, which take a long time to machine, are also well-suited for casting. <\/p>\n\n\n\n

    Internal cavities are often ideal for casting, as forming them with CNC machining can be costly and difficult. This is especially true for sealed internal cavities, which may require assembly or metal-joining processes in addition to CNC machining. Casting simplifies this. Instead of machining multiple small parts and assembling them, you can cast the entire part and eliminate assembly steps altogether.<\/p>\n\n\n\n

    \"CNC<\/figure>\n\n\n\n

    <\/p>\n\n\n\n

    However, certain features are more difficult to achieve with casting. Undercuts or internal features require more complex molds with cores and inserts. Sharp edges or corners are not ideal for casting either, and cast parts require a draft angle on all features. Large or oddly shaped parts with thick walls are also better suited to CNC machining, as those geometries are difficult to fill and cool evenly during casting.<\/p>\n\n\n\n

    Casting vs CNC Machining: Choosing Based On Materials<\/strong><\/h3>\n\n\n\n

    Casting results in less material waste than CNC machining. The process uses only the material needed for the final part, aside from a small amount of metal flowing through the gate, runner, and sprue. This excess material can be easily removed, remelted, and reused. <\/p>\n\n\n\n

    However, casting offers far fewer material options than CNC machining. Virtually any alloy can be CNC machined<\/a>, while the list of alloys that can be cast<\/a> is much shorter. <\/p>\n\n\n\n

    Casting vs CNC Machining: Choosing Based On Production Speed<\/strong><\/h3>\n\n\n\n

    The casting process is fast once the mold is ready, making it a strong option for high volumes. However, mold design and machining add lead time\u2014typically a few weeks\u2014and the mold must undergo quality checks and maintenance, though some casting types use expendable molds. Die casting uses a permanent mold, so time and cost per part decrease as volume increases. <\/p>\n\n\n\n

    CNC machining provides a faster turnaround for low volumes. There\u2019s no need to wait for a mold to be manufactured\u2014all you need is the CAD model, CAM program, and a CNC machine to get started.<\/p>\n\n\n\n

    \"Die<\/figure>\n\n\n\n

    <\/p>\n\n\n\n

    Casting vs CNC Machining: Choosing Based On Repeatability and Precision<\/strong><\/h3>\n\n\n\n

    Repeatability is essential in manufacturing, and the casting process produces highly repeatable parts. Once the mold and process are dialed in, every part can be made precisely the same. With precision die casting, tolerances can be held to +\/- 0.1 mm per 25 mm.<\/strong> <\/p>\n\n\n\n

    Those tolerances may vary by material and supplier. Aluminum<\/a>, for example, has a higher melting point than zinc, so it requires a higher injection pressure and a more aggressive process overall. That results in looser tolerances with casting versus machined aluminum. Zinc, by comparison, holds tighter tolerances when cast. <\/p>\n\n\n\n

    CNC machining metal is also highly repeatable and produces much tighter tolerances than casting. For standard metal machining, 0.025mm (0.001\u201d)<\/strong> is a reasonable expectation. Fictiv precision machining can produce parts with tolerances as tight as +\/- 0.0002\u201d<\/a>.<\/p>\n\n\n\n

    Casting vs CNC Machining: Choosing for Prototyping<\/strong><\/h3>\n\n\n\n

    Although casting has its advantages, it\u2019s not ideal during the prototyping phase of the development process. Every design change increases lead times and cost, as expensive molds are re-created or adjusted. A prototype die cast can cost thousands, if not hundreds of thousands of dollars. And, while sand casting is typically cheaper, it cannot match the dimensional accuracy or surface finish of machining or die casting. <\/p>\n\n\n\n

    CNC machining is the better choice for prototyping<\/a>, due to its relative agility. When the design is still in flux, all you need to do is update the model and revise the CAM program, rather than remaking or modifying an existing mold. <\/p>\n\n\n\n

    \"cnc
    CNC machining is typically a better option for prototype parts than casting
    <\/figcaption><\/figure>\n\n\n\n

    <\/p>\n\n\n\n

    Casting vs Machining: Choosing Based On Quantity and Demand<\/strong><\/h3>\n\n\n\n

    The quantity of parts you need will also factor into your decision. Early in the prototyping process, volumes are usually low enough that CNC machining makes more sense. Demand variability is another consideration: how often do you actually need to produce more parts? If production needs fluctuate, CNC machining offers more flexibility. <\/p>\n\n\n\n

    CNC-machined parts can be ordered quickly and on demand, especially as digital manufacturing platforms<\/a> shorten lead times in the manufacturing industry. That makes CNC machining more economical when you\u2019d rather order parts as needed than try to predict demand and carry excess inventory. <\/p>\n\n\n\n

    However, if you\u2019re moving into production with consistently high demand, casting is the stronger choice because it\u2019s better suited to producing thousands of parts quickly and cost-effectively.<\/p>\n\n\n\n

    \"Die
    Die casting is an excellent option for higher-volume production of metal parts.<\/figcaption><\/figure>\n\n\n\n

    <\/p>\n\n\n\n

    How to Choose Between Casting and CNC Machining<\/strong><\/h2>\n\n\n\n

    When deciding between casting and machining, consider your stage in the development process, the quantity of parts required, demand variability, and part geometry. It’s also important to note that the two methods aren\u2019t mutually exclusive; for instance, you can post-machine a die-cast part if necessary.<\/p>\n\n\n\n

    The right manufacturing process will always come down to your specific situation. Some combinations of volume, geometry, and timeline will push you to find a creative solution that doesn’t fit neatly into one process or the other.<\/p>\n\n\n\n

    When Does It Make Sense to Switch from CNC to Die Casting?<\/strong><\/h2>\n\n\n\n

    For many product teams moving from prototyping to production, the real question isn\u2019t CNC vs. die casting\u2014it\u2019s at what volume does switching from CNC to die casting make sense? <\/strong>The answer comes down to tooling cost, per-part cost, and forecasted demand.<\/p>\n\n\n\n

    Casting vs CNC Machining: Tooling Cost vs. Piece Price<\/strong><\/p>\n\n\n\n

    Criteria<\/strong><\/td>CNC Machining<\/strong><\/td>Investment Casting<\/strong><\/td>Die Casting<\/strong><\/td><\/tr>
    Tooling Cost (Initial)<\/strong><\/td>None to Low<\/td>Medium<\/td>High <\/td><\/tr>
    Per-Part Cost (Low Volume)<\/strong><\/td>Moderate to High<\/td>Moderate to High<\/td>High<\/td><\/tr>
    Per-Part Cost (High Volume)<\/strong><\/td>High<\/td>Moderate<\/td>Low<\/td><\/tr>
    Ideal Volume Range<\/strong><\/td>0\u2013500 parts<\/td>~500\u20135,000 parts<\/td>10,000+ parts<\/td><\/tr>
    Break-Even Volume<\/strong><\/td>1\u20132,000 parts<\/td>~500\u20135,000 parts<\/td>~5,000\u201310,000 parts<\/td><\/tr>
    Production Speed<\/strong><\/td>Slower (machine time dependent)<\/td>Slower (multi-step)<\/td>Very fast (after tooling)<\/td><\/tr>
    Labor Intensity<\/strong><\/td>High (CAM and machining time)<\/td>High (manual steps)<\/td>Low (automated)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

    <\/p>\n\n\n\n

    What this means in practice:<\/strong><\/p>\n\n\n\n