What is machined castings?

Fabricators often present metal machining and casting processes as mutually exclusive options. However, our recent article on casting versus machining suggests that combining these processes can result in a more efficient means of production. In this article, we highlight the advantages of machining castings and provide insights on seamlessly incorporating both manufacturing processes into your future designs.

What Is a Machined Casting?

Fabricators often present metal machining and casting as an either/or choice. However, it is increasingly recognized that the optimal production approach often combines both processes. involves using casting to create a semi-finished product and subsequently refining it through precision CNC machining.

To begin, various casting methods like die casting, investment casting, or casting can be employed to produce the initial castings. Nonetheless, these methods may have limitations such as rough surface finishes or constraints on specific design features.

By incorporating CNC machining, the quality of the product can be enhanced, and missing design elements can be added. CNC milling, turning, drilling, sawing, and even unconventional machining techniques can be applied to achieve superior finished products.

The Benefits of Machining Castings

The machining of castings has two primary benefits:

1. Adding features and removing unwanted as-cast material.
2. Improving precision and surface finish.

To better understand why these benefits are so important, let’s explore the applications relevant to each one.

Adding Machining Allowances to Your Designs

Regarding machined castings, designers must incorporate machining allowances into the mold design so that as-cast parts have enough material for precision machining.

For example, imagine your finished part has a small protrusion with tight tolerances. If the mold design has a feature the same size as the protrusion, any shrinkage or porosity will make the feature smaller than it was supposed to be. If you need any machining to improve the surface finish or refine the shape of the protrusion, machinists would be forced to remove even more material or risk leaving the part rough and unfinished.

Adding machining allowances to your part design slightly increases the size of any as-cast parts or part features that the manufacturer will finish with CNC machining. These allowances help fabricators consistently meet tolerance requirements with fewer rejected parts while significantly reducing machining times.