Fabricating through CNC is very versatile because aside from the great precision and accuracy you get for your CNC parts, is the fact that you have a wide variety of available materials to work on. Unlike other fabricating methods, CNC machining does not have much constriction on the workable materials you could use for your part. That sure is great, right? But before you get hyped too much on creating your own CNC part, let me just warn you that selecting materials is not as easy as it sounds. First and foremost, you’ll end up boggled with one question: “Which one should I choose?”
Let me walk you through the different factors and varying aspects you should be mindful of when choosing the material for your CNC parts.
Common Materials Used for CNC Parts
There are numerous materials you can use for creating your custom part but here are the most common ones being used in the industry:
Aluminum Alloys
Aluminum alloys are one of the most common raw materials used in machining prototypes because of their excellent machinability, lightweights, and corrosion resistance. In addition to their desirable mechanical properties, these alloys are one of the most economical choices.
Brass
Brass is probably the easiest material to a machine that is included in the list. These are commonly used for fittings because of their high corrosion resistance, low friction coefficient, and compressibility.
Stainless Steel
Stainless steels are typically used for precision machining due to their high strength and corrosion resistance. There are many grades of stainless steel depending on your application whether it will be used for marines, automotive, or aerospace applications.
Steel
This metal also has high strength, however, steel is prone to corrosion if not processed for coating or plating. Steel is used for mechanical components in the oil and fuel, mining industry, and other heavy-duty industries.
Titanium
Titanium is one of the machinable materials with very desirable mechanical properties. Aside from its high strength to weight ratio, titanium is also resistant to heat and corrosion. This material is perfect for aerospace and medical applications.
Engineering Plastics
These are specialty plastics designed to withstand high heat and high impact applications. Through the advancements of technology nowadays, there are a lot of variations of this material that is perfect for any type of applications (e.g., Nylons, ABS, HDPE, Delrin, PEEK)
What to Consider for CNC Parts
Now that you have been briefed on the common raw materials used, let’s go on to the main juice of the article. For you to choose the most cost-effective and appropriate material, you must be aware of the different factors as summarized below:
A. CNC Parts Design and Application
In narrowing down your choices for materials,you should clearly define the main requirements for a certain component. These might include the size of parts, strength needed, criticality, tolerances, overall geometry, and many more. Below is a comprehensive summary and explanation of these requirements.
- Parts Geometry
Part size and complexity fall under this category. Some materials are not good for machining large sizes and there are also some materials not good for complex profiles.
Use case: It is impractical for you to use steel for a very complicated design with a lot of irregular profiles and undercuts. The reason is that your design might fail during the machining process. You might encounter tooling breakage, due to the stubbornness of the steel.
As a takeaway, choose materials that are easy to machines, like aluminum alloys and brass or CNC parts with complex profiles.
- Functionality Requirements
Another aspect of the parts’ design you should be aware of are the functionality requirements like the strength a part needs during its course of utilization, operating temperature conditions, magnetic requirements, insulation, and other mechanical requirements.
Use case1: Treated stainless steel is used in making pistons for an automotive engine so that it can withstand the high stress and high-temperature conditions for this application. In addition, stainless steel is a wise choice for creating pistons because this material is compatible with other processes like carbide plating.
Use case 2: Titanium is one of the best choices for machining implants for the body because of its high strength-to-weight ratio, meaning it is highly durable without it being too heavy. Furthermore, titanium has unparalleled corrosion resistance.
Use case 3: The best material to choose when you want your part to be chemical and corrosion resistant is engineering plastics.
Use Case 4: For rugged applications like that in the mining and construction industry, where there are repeated impacts and corrosion is not much of a concern, steel and other nickel alloys (Inconel) are best used.
B. Economics of Manufacturing
Another factor that will narrow down your choice of material will be the economics behind the fabrication of your CNC part.
- Price of the Material
It makes sense for you to choose the cheapest material there is as long as your primary requirements are met.
Use case 1: You don’t have to use titanium when your part can just be made from aluminum alloy which also has a high strength to weight ratio.
Use case 2: Designers usually split a CNC part into components so that only the critical component will be made up of the expensive material while other components can just be made up of a cheaper material. One example is a machining center in which the contact tip is made up of expensive carbide while the rest is made up of fair-priced steel.
- The overhead cost of processing the CNC Parts
Materials that are harder to machine and process are relatively expensive compared to softer materials. Hard materials include steel and its alloys.
- Availability of Materials
As a rule of thumb, never use a material that is not abundant in your area. You have to make sure that the material for your part is available at your local CNC shop to help save you from tedious procurement processes or even expenses.
Put it all together
As a wrap-up, in the material selection process, you have to:
- Be aware of the different factors to be mindful about.
- Establish your material requirements
- Identify available materials
- Select the most appropriate one based on the factors discussed in this article.
