‘CNC milling of aluminum workpiece with coolant to reduce heat generation’
Aluminum is one of the most popular metals you can use for CNC machining. It is readily available and has an excellent strength-to-weight ratio. CNC machining aluminum is an accurate and precise process. However, it can pose a risk if you don’t carry it out properly. Your safety can be jeopardized due to a slight oversight such as incorrect machining parameters or using worn-out tools. It can also be a result of unnecessary vibration, chip build-up, and production of noise above the minimum permissible level.
Before machining aluminum, it is important to understand how the process works, the potential hazards, and how to avoid them. This article will explain what CNC machining aluminum is, the type of aluminum alloys you can safely machine, and some best practices you should follow when milling or turning aluminum.
What is CNC Machining Aluminum and How Does it Work?
Aluminum CNC machining is a subtractive manufacturing technique that removes excess material from a workpiece to create the final part. It is a computerized process that uses preprogrammed software to control the movement of complex tools and machinery. CNC Machining aluminum works by creating a model of the final design using CAD software. Thereafter, the CAM software converts the model to a CNC-understandable file in the form of G code and M code. The G code tells the tools how and where to move while the M code controls miscellaneous functions such as start and stop actions. You then configure the machine and execute the operation.
There are different CNC machining operations you can carry out safely on aluminum workpieces. Some of the most common ones include
Aluminum CNC Milling: In this process, the aluminum workpiece is stationary while the tool is mounted on the rotating spindle. The spindle moves along various axes to machine the part. CNC milling is compatible with many grades of aluminum and it creates parts exactly to specification.
Aluminum CNC Turning: CNC turning uses a chuck to hold a cylindrical aluminum piece. The aluminum part rotates at high speed as the turning tool engages and disengages to result in a cutting action.
Aluminum CNC Drilling: CNC drilling describes the process of making cylindrical holes in an aluminum part using a rotating bit. The holes may serve just aesthetic purposes. In other instances, it accommodates fasteners such as bolts and screws to aid assembly.
Is CNC Machining Aluminum Safe?
Aluminum is a common material for CNC machining because of its many properties. However, there are some safety concerns regarding aluminum CNC machining. The following are potential hazards you should know.
Chips Production
During CNC operations, the excess materials removed are nothing but chips. The production of chips can affect safety in many ways. Chips are usually sharp and long which can lead to cuts or injuries. Additionally, tiny ones generate dust and cause respiratory issues. You should note that aluminum chips can be uniform and continuous or discontinuous with nonuniform shapes.
Noise
CNC machining can be noisy especially when operating at a high speed. This can affect both the operators and other employees. The legal limit of noise at work is 85 dBA averaged over 8 hours. However, some CNC millers and lathes may produce noise up to 100 dBA. Constant exposure to this noise level can lead to detrimental effects.
Cutting Tool Breakage
Tool failure and breakage are also a potential safety hazard. In addition to causing delays in the production process, it increases the likelihood of worker injury. Several factors such as wear and tear or inaccurate cutting parameters can lead to tool breakage.
Vibration
Unchecked vibrations in aluminum CNC machining poses a risk. It can lead to tool and workpiece chatter or cause the machine to shift suddenly. Additionally, vibrations increase the wear of the machine’s components and generate a high level of noise.
Common Types of Aluminum that Can be Safely Machined
Aluminum is rarely used in its raw form. You will find it combined with other elements such as zinc, copper, and magnesium to enhance its machinability and overall safety. The following are common aluminum alloys you can safely CNC machine
6061 Aluminum
This grade contains 97% aluminum with silicon, chromium, magnesium, and traces of other elements. It has excellent corrosion resistance properties and you can easily heat treat it to higher strength levels. 6061 aluminum may be the most ideal if you want to manufacture automotive engines, aircraft components, and sporting goods.
6063 Aluminum
6063 aluminum is another popular type you can safely machine. It has up to 98% aluminum with magnesium and silicon as the major alloying elements. 6063 aluminum has a medium strength and is easily machinable and weldable. You can refer to this grade as ‘architectural alloy’ because its major application is in architectural fabrication. Additionally, you can use it for doors, window frames, and irrigation tubing.
7075 Aluminum
7075 aluminum contains a high percentage of zinc and chromium to enhance strength and corrosion resistance. This grade of aluminum is also tough and ductile. 7075 aluminum is mainly used for constructing transportation components in automotive, marine, and aviation industries.
2024 Aluminum
This grade of aluminum alloy has copper as its major alloying element. It also contains varying amounts of manganese, silicon, iron, magnesium, and others. 2024 aluminum is easily malleable and has high strength and good workability properties. You can use it to manufacture aircraft fuselage and truck wheels.
5052 Aluminum
5052 aluminum is primarily alloyed with magnesium with a smaller quantity of chromium. It has moderate strength, excellent corrosion resistance, and good weldability properties. 5052 aluminum has applications in heat exchangers, roofing systems, different types of rivets, and fuel tanks.
6068 Aluminum
6068 aluminum contains mainly magnesium and silicon as the main alloying elements. Magnesium enhances corrosion resistance while silicon lowers melting point and prevents the generation of excess heat. 6068 aluminum has a high strength which makes it useful when manufacturing fasteners, bridges, and cranes.
Safety Precautions and Best Practices
‘Work holding fixture securing an aluminum mold part during CNC operation’
Though aluminum is relatively safe for CNC machining, there are some safety considerations. Below are some precautions you should keep in mind to mitigate risks and ensure safety.
Proper Machine Maintenance and Setup
When setting up a CNC machine, it is important to follow the manufacturer’s instructions. Additionally, ensure there is adequate ventilation in the workplace and that the power source meets the required voltage. Furthermore, clean and replace blunt tools regularly.
Use of Personal Protective Equipment (PPE)
When machining aluminum parts, always use appropriate PPEs to prevent workplace hazards. These include protection for eyes, ears, hands, and feet. It also entails proper packing of long hair and avoiding loose clothing.
Ventilation and Dust Collection Systems
Because of the potential of dust generation during aluminum CNC machining, it is important to install a ventilation and dust collection system. This system consists of a dust boot, vacuum hose, dust separator, and shop vac. They function hand in hand to remove dust and harmful gasses which results in a safer and cleaner work atmosphere.
Use of Chip Breakers
Aluminum CNC machining will inevitably produce chips. Hence, you must use a chip breaker when milling or turning aluminum workpieces. The chip breaker is usually located on the tooltip. Its main function is to break up chips, improve chip control, and direct chips away from the workpiece.
Use Jigs and Fixtures
You need to invest in high-quality jigs and fixtures when machining aluminum. Though used interchangeably, jigs and fixtures serve different functions. Fixtures secure the workpiece in place to prevent unnecessary vibrations. On the other hand, jigs hold and guide the tool during cutting actions.
Conclusion
Aluminum is a popular engineering material used across various manufacturing industries from automotive and aerospace to military and defense. It is easily machinable, nontoxic, and does not produce harmful fumes. However, it is important to keep in mind some safety considerations when machining aluminum parts. These considerations include proper setting up of the machine, use of work holding fixtures to prevent vibrations and chatter, and use of appropriate PPEs. All these ensure a safe working environment for you and other employees.
