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Aluminum is a wonderful material used in a lot of parts around us. From heat sinks to engines to aerospace components, aluminum has relevance everywhere. It is highly appreciated for its low weight, high machinability and a variety of surface finish options. CNC milling adds great value to aluminum. It converts solid blocks into highly precise components featuring intricate geometries, deep pockets and accurate holes. Aluminum parts provide great ease in assembling. Instead of joining many different components together, a single solid block of Aluminum can be CNC milled to create a single part having complete functionality. Let’s find out more about CNC milling aluminum parts!
How CNC Milling Works for Aluminum
CNC milling is an incredible way to manufacture precision Aluminum parts. CAD files store all the necessary design details for the parts. While CAM software helps to make G Codes and M Codes for the CNC mill. The biggest advantage is that manufacturing process is repeatable and scalable. As human intervention remains at a minimum, so human errors are kept at bay. If you are looking for precision custom-made parts, then look for an approachable aluminium milling service center.
Material Removal Principle
Aluminum CNC milling relies on subtractive manufacturing principle. A rotating cutting tool progressively removes material from a solid block or billet to carve out CNC-milled aluminum parts. The CAM software guides the CNC to remove material bit by bit in the form of chips from the designated areas. Aluminum generally offers a low cutting resistance and a high thermal conductivity. So, high speed and feed rate are possible. Modern CNC milling of aluminum employs high-efficiency milling (HEM) and adaptive milling to minimize tool engagement and boost productivity.
Multi-surface and Pocket Machining
Modern aluminium milling service providers are equipped with new model CNC milling machines. These CNC milling machines have the ability to work on multiple surfaces and complex features in a single setup. The tool has the flexibility to move in multiple directions. So, different faces can be accessed without manual reclamping. The pocket machining technique is highly suitable for CNC milling aluminum parts that have intricate features. As an example, material can be removed from enclosed areas to carve out cavities, channels, or ribs in CNC milling aluminum parts like heat sinks and liquid cold plates.
Suitable Aluminum Alloys for Milling
Aluminum is CNC milled for quite a lot of applications. It offers low density, high machinability, high corrosion resistance and good aesthetics. Metallurgists have developed a few alloys for different applications. Understanding of the right alloy for the right use is essential from a design point of view. Broadly, aluminum alloys can be characterized as medium-strength alloys and high-strength alloys. Let’s take a glance at it.
Medium-strength Aluminum Alloys
Medium-strength aluminum alloys offer an excellent balance of machinability, corrosion resistance, formability, and cost. Generally, CNC milling of these aluminum alloys shows very few complications and thus gives a good consistency in quality. Medium-strength aluminum can be CNC milled at high speed with minimal tool wear. The surface finish of CNC-milled aluminum parts of these alloys is cleaner than that of other high-strength alloys. Anodizing further enhances the surface appearance. Medium-strength aluminum alloys are suitable for producing fixtures, enclosures, brackets, frames, heat sinks, and liquid cold plates. The table below highlights notable features of medium-strength alloys and their CNC-milled aluminum parts.
Alloy | Tensile Strength (MPa) | Machinability | Benefits | CNC milling aluminum parts |
6061-T6 | 290-320 | Excellent | Excellent machinability, good corrosion resistance and can be anodizing | Brackets, enclosures, heat sinks and liquid cold plates |
6082-T6 | 310 -340 | Very Good | Higher strength than 6061 and good dimensional stability | Structural parts, frames and plates |
6063-T6 | 240-270 | Excellent | Good surface finish and excellent extrudability | Decorative parts, profiles and housings |
5052-H32 | 220- 260 | Good | Excellent corrosion resistance and high ductility | Thin plates and covers |
MIC-6 | 230-260 | Excellent | High flatness and minimal distortion | CNC base plates, fixtures and custom machine parts |
High-strength Aluminum Alloys
High-strength aluminum alloys are preferred in applications where higher strength and weight reduction are the most desired characteristics. The alloys offer an excellent strength-to-weight ratio for CNC milling aluminum parts. As an example, in aerospace applications where designers are keen to reduce every extra gram of mass from components, these alloys play a vital role. On the downside, their machinability is a bit lower. So, extra care is required in CNC milling of these aluminum alloys. Some free machining alloys, such as 2011-T3, can be machined at a high speed. Normally, high-strength aluminum alloys are preferred in applications like aerospace components, structural parts, jigs, molds and precision tooling. The table below table show feature of some of the common high-strength aluminum alloys:
Alloy | Tensile Strength (MPa) | Machinability | Benefits | CNC milling aluminum parts |
7075-T6 | 520-580 | Good | Good strength-to-weight ratio | Aerospace parts and’ high-load components |
2024-T3 / T4 | 430-480 | Good | Excellent fatigue resistance | Aircraft structures |
7050-T7451 | 500 -550 | Good | Better stress-corrosion resistance than 7075 | Plates and thick machined parts |
2011-T3 | 380- 420 | Excellent | Free-machining aluminum alloy | High-volume production parts |
2618-T61 | 440-480 | Good | Thermal stability | Pistons and aerospace engine components |
Accuracy & Tolerance Control
Compared to other common manufacturing processes, CNC milling has the ability to produce highly accurate dimensions. Tight tolerances to the fraction of a millimeter are possible in the CNC milling process. Flatness, parallelism and dimensional accuracy provide great ease in proper fitting in assemblies. Surface treatment creates robustness for a long-term service life.
Flatness and Parallelism
Maintaining flatness and parallelism is crucial for the proper fitting of mating surfaces. It determines the functionality of assemblies, sealing surfaces, and thermal interfaces. Although CNC milling is a highly accurate process, some factors can limit this accuracy. Residual stresses in the worked material can create distortion in the CNC milling of aluminum. A stress-relieving heat treatment can alleviate this problem. A good aluminum CNC milling strategy can produce CNC-milled aluminum parts with a high level of flatness. For example, balanced roughing and finishing passes and low aggressiveness in CNC milling parameters can bring about good parallelism. Proper fixturing is also pertinent.
Hole Position and Diameter Accuracy
Aluminum CNC milling can automatically create holes as per the CAD and CAM files. However, for achieving a greater accuracy, drillingis followed by reaming. As with all processes, an optimum CNC milling strategy should be adopted. Proper coolant flow and inclusion of thermal expansion allowance prevent dimensional deviations. The clamping setup should be rigid and the correct tool should be selected for clean holes. Further, adoption of appropriate cutting parameters also improve holes’ position and diameter accuracy.
Surface Finish Options
CNC milling aluminum parts normally come in two types of surface finishes: ‘as milled’ and ‘anodized’. Both surface finishes have their own benefits and limitations. Customers often choose the finish according to the applications.
As-Milled Finish
As milled surface finish is widely accepted for functional components, internal features, and non-cosmetic parts. It offers the advantage of low cost and high productivity. This natural surface condition has a surface roughness of Ra 1.6-3.2 µm. It might show fine tool marks that follow the cutter path. But, if the surface is for a non-cosmetic purpose, than as milled condition is preferred due to its low cost.
It also gives more accurate dimensions as parts do not undergo any oxide-building surface treatment processes.
Anodized and Polished Finish
Anodized and polished finishes offer an aesthetically appealing surface. This surface treatment provides enhanced corrosion resistance and wear resistance. Polished CNC-milled aluminum parts have a very low surface roughness. Little to no surface marks remain visible. A variety of colors beautify the CNC milling aluminum parts as per customer requirements.
Typical CNC Milled Aluminum Parts
Mounting plates
CNC milling of aluminum alloys offers excellent flatness and dimensional stability. These properties are highly suitable for mounting plates. The lightweight nature of
CNC milled aluminum parts do not unnecessarily increase the mass of the assembly. Parts like base plates, adapter plates, and equipment mounting surfaces give good alignment and precision.
Structural blocks
CNC milling aluminum blocks offers the advantage of creating complex geometries, pockets, and internal features in a single part. As a result, the assembly steps are greatly minimized. The CNC-milled aluminum components are lightweight. But still, they can be reliably used in load-bearing applications.
Machine brackets
Precision CNC milling of aluminum brackets produces incredibly correct alignment. What’s more, these brackets have a good strength-to-weight ratio, corrosion resistance, and repeatable accuracy. These features provide long-term mechanical integrity in mechanical assemblies.
Conclusion
CNC milling for aluminum is a widely practiced manufacturing technique used across a wide range of industries. Comparatively, CNC milling produces parts with higher accuracy and precision than most other processes. Surface finishing options, such as anodizing and polishing, further enhance aesthetics and corrosion resistance. For critical applications like aerospace components, utmost care should be taken during CNC machining. Optimum milling strategies can avert adverse impacts such as tool marks, hot spots, burrs, and rapid tool wear. This level of control is possible because CAD files store the design information, while CAM software translates the CAD into processable G-codes and M-codes. For precision aluminum parts and expert CNC milling, look no further than Conglin Aluminum.
