CNC Machining: Prototyping with Aluminum Alloys

Posted on Feb 4 2021 - 7:55pm by admin

Aluminium die-cast prototype

The machining of Aluminum is one of the superior ways to produce a prototype for new concepts by precisely machining a component you are fabricating. Depending on the nature of your machining, whether it be for production or for prototype procurement, there are many factors that can come into play throughout the process of CNC aluminum that operators and designers should consider.

Aluminum Alloys

As Aluminum is a diverse metal that is naturally easy to work with, there are many different alloys in existence that were developed to serve different purposes.  The mechanical characteristics of each variation of aluminum are often visible throughout the CNC development techniques.

By characterizing aluminum further with an alloying element, you dramatically change the chemical composition and design the alloy to serve an intended purpose. For example, when Silicon is added to Aluminum, you dictate the material to be able to have a lower melting temperature which in turn allows it to be used for welding purposes.  4043 Aluminum serves to be a reliable alloy to serve as the basis of most welding operations as a result.

The characterisation of Aluminum then drastically changes the nature of the CNC operation and the possibilities of its outcome. With over 400 wrought alloys and over 200 casting alloys, the choices for your needs are bountiful. Different grades allow you to focus on certain properties, allowing the machined component to serve its intended purpose.

CNC aluminum parts

Mechanical properties of Alloys

The mechanical properties that you should be concerned with directly correlate with the end goal of your project. Making a list of desirable traits and ranking them in importance should be done at the beginning of every prototyping session. Ductility, Yield Strength and elasticity are some of the important mechanical properties that most tend to prioritize. Alloys that serve to be used in aerospace applications serve to have a high enough tensile strength to rely on while also being lightweight to hinder the dynamics as little as possible. 7075 Aluminum serves to possess a tensile strength of 572 MPa and is light enough to be a favorable choice for manufacturers for parts that require the utmost precision. 

Physical properties of Alloys

As important as mechanical properties, physical properties need to be prioritized and listed as well when selecting aluminum alloys to machine. Properties such as corrosion resistance, melting point and electrical conductivity are a few of the important that seem to stand out during optimization for durable components.

Seeking the utmost corrosion resistance is usually a significant factor in prototyping aluminum, as this property has a direct correlation with the life cycle of the component to be machined. 6061 Aluminum is a favorable alloy as the alloyed copper added to the aluminum through characterization dictates the alloy to be least susceptible to corrosion. An application such as maritime environments often look in this direction as the environment highly encourages corrosion to occur much more frequently and rapidly. 

Chemical Properties of Alloys

Lastly, chemical properties define the product’s relationship with its environment. Properties such as  toxicity, reactivity and heat of combustion can drastically change the operating conditions of the final product.

If a product were to be used in a situation where human contact is high, such as biomedical applications, low toxicity would be a property that would be prioritized throughout the product design.  3XXX wrought cast alloys are aluminum variants that are alloyed with Manganese. As oxidation is a typical process that can occur, these alloys should be avoided as all costs as manganese is a carcinogen to humans when introduced in excessive amounts. The close contact and breakdown of a product made up of this alloy would serve to be extremely detrimental in the long run.

The looming factor 

Depending on the expected outcome, the selection for the wide range of alloys can be easily narrowed down by cost estimations. If machining aluminum is only intended to serve as the beginning of a product’s development, then most properties can be overlooked and the determining factor of material selection can make the process simpler. By simply basing material selection for the prototypes to be machined based on the smallest price to pay for and use the component  to determine more accurate dimensions for future developed products, then an alloy like 6061 Al can be used. This alloy makes rapid prototyping to be cost effective and allows the designer to filter any issues with dimensions and features of the product. Most times, the designer can decide dimensions at the beginning of the project and through fabrication, an issue can go unnoticed until validation tests take place slowing progress or putting lifes in jeopardy. By using rapid prototyping to battle this specific issue, it is much more likely to find the mistake during embodiment design. 

Conclusion

Aluminum as a base material for CNC operations is a choice that will in turn save on project costs and allow designers to visualize and further conceptualize ideas. Throughout a timeline of a manufactured component, the plethora of Aluminum alloys can be switched between each other to determine the ideal properties you want your final product to possess. Seeing the effects of the pre-set criteria for a project be validated allows the quality of the final iteration to significantly increase. As with any material selection, there is always a trade off with certain properties and it is up to the user what should be sacrificed to achieve the top priorities for the material. An alloy may offer higher tensile strength than the other, but may be twice its weight. An alloy that offers less heat conductivity may also be more prone to corrosion over time. As with this, it should also be said that any material should be easier to work with using CNC machining, as more difficult materials may drive manufacturing costs much higher.  Through rapid prototyping, the gap between knowledge between fabricator and designer can be filled and the duration of the project can be shortened.

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