CNC machining and 7 reasons to select aluminium for workTDB Machining
7 reasons why aluminium machining is chosen for CNC machining
In this article, you will go with us through seven reasons why aluminium is one of the most popular and ideal materials for CNC machining, from cost to its ease of machineability to keep your budgets on track, to the material properties that you need for your part.
No time to wait
Any CNC machining manufacturer would point out how easy it is to machine parts using aluminium. The dimensional stability of aluminium means that you can cut a lot of it away and still keep residual stress in check. To achieve a great finish for your aluminium machined part, carbide tooling and modern coolants can be used. If you want a matt finish then sandblast can be applied. If you want a consistent aesthetic finish and additional corrosion resistance, anodizing is the go-to option.
And best of all this available machineability will help keep the cost of your part down. But you select a material based on what characteristics you need from your part, hereunder are what aluminium offer.
Great strength-to-weight ratio
Aluminium will save weight for your machined part because it is lighter than most metals. Pure aluminium has a tensile strength of less than 100Mpa, but its hardness can be enhanced significantly as follows:
- Alloying: The grain structure will be improved by mixing with other elements.
- Heat treatment: An ideal-sized crystal will be formed by heating and then cooling at a specific rate.
- Strain hardening: Strengthening the material by deformation. This strengthening occurs because of dislocation movements and dislocation generation within the crystal structure of the material.
Compared to stainless steel 315L, most aluminium alloys have a higher strength-to-weight ratio or specific strength.
While Titanium is a clear winner from the table below, when stiffness and weight saving are important, high-strength aluminium alloys are a great cost-effective alternative if budgets are an issue.
Wide choice of alloys and material properties for CNC machining
There are a lot of alloys available, each of which has different properties and uses to meet your needs. Aluminium is such a great base material to work with.
These are grouped into nine different series with each series numbered by a thousand, so for example 6000 series. This is then further subdivided by a number. Generally, the closer the number of the aluminium grade to another the more similar they are, so 5082 and 5083 are nearly identical.
Here are some of the more popular grades:
- 2024 – Aerospace grade, with high fatigue strength, it trades ultimate tensile strength (UTS) for more ductility/toughness, by alloying with copper.
- 5083 – Marine grade, with good corrosion resistance, as it has higher magnesium content.
- 6082 – General purpose and aerospace grade, it has a good blend of strength, ductility and corrosion resistance which make it versatile and commonly used. This is achieved by alloying with a mixture of magnesium and silicon.
- 7075 – High strength aerospace grade, good balance of properties, particularly where high static loads occur. It can be heat treated and contains more zinc, as well as magnesium and chromium.
High corrosion resistance
Corrosion resistance varies at each grade, Aluminium is an excellent choice if you need this from your material.
The metal and its alloys have an ideal affinity for oxygen – metals that are too reactive like magnesium will oxidise easily, while less reactive metals form a loose oxide layer such as rust on iron and steel.
In contrast, when aluminium is exposed it forms a passivating layer of aluminium oxide that seals the surface preventing further oxidisation and erosion. This layer is “self-repairing” even if scratched, so the material may not need painting or surface treatments, giving you a cost saving on manufacturing and lifetime service costs. This natural corrosion can be enhanced by anodising.
Good thermal conductivity of aluminium also means that it is commonly used for heat sinks and heat dissipation.
When it comes to conductivity, copper is often the go-to material. However, because of the cheaper price and lighter weight, aluminium is often selected for electrical components. In fact, it is often used for busbars, battery cables and connectors, particularly in automotive and EV applications.
Recyclability of aluminium part
Recycling aluminium uses much less energy than producing it. Recycling scrap aluminium requires only 5% of the energy used to make new aluminium from the raw ore. For this reason, approximately 36% of all aluminium produced in the United States comes from old recycled scrap.
Aesthetics for the machined part
For added aesthetics on your aluminium machined parts, you can even have it in a number of different colours by anodizing.
This is an electrolytic passivation process not only used to increase the thickness of the natural oxide layer on the surface of metal parts, but it makes it easy to add colour.
In conclusion, material selection for your part is crucial and will depend on what characteristics you need from it. Aluminium is often a great choice for the reasons outlined above.