Magnesium CNC Machining

Low weight

Compared to aluminum alloys, magnesium alloys not only have a lighter weight but also possess higher strength and superior rigidity. The stiffness of magnesium alloys increases cubically with thickness, making them favorable for the design of structural components.

Machinability: Magnesium alloys have low cutting resistance, approximately one-tenth that of steel and one-third that of aluminum, resulting in shorter cutting times and longer tool life. Their machining performance is excellent, leading to low machining costs and minimal energy consumption.

Corrosion Resistance: Magnesium exhibits good corrosion resistance in atmospheric conditions, surpassing that of iron. High-purity magnesium alloy AZ91D has significantly better corrosion resistance than low-carbon steel and even exceeds cast aluminum alloy A380. The presence of beryllium and calcium in magnesium alloys can enhance their corrosion resistance, while the presence of iron, cobalt, nickel, and copper significantly reduces the alloy’s corrosion resistance.

Damping Capacity: Magnesium alloys have excellent damping capacity compared to other metals. Even though the Young’s modulus of magnesium is low, it serves as an excellent damping material. Using magnesium alloy materials in automotive structural components can significantly reduce noise and vibration during vehicle operation.

Dimensional Stability: Magnesium alloys can maintain their dimensional stability over extended periods, with virtually no observable changes in the working dimensions.

Impact Resistance: When magnesium die-cast components are subjected to impact, they produce smaller surface scars compared to iron and aluminum components.

Abundant Resources: China is a major source of magnesium resources, with abundant reserves of high-quality magnesium refining materials, including magnesite, dolomite, and salt lake magnesium resources.

Magnesium is one of the easiest materials to CNC machining. It is easily machined at high speeds, far exceeding the maximum speeds achievable with cast iron and steel. Furthermore, it can achieve excellent surface quality.

During dry machining of magnesium alloys, there is no need for coolant, which can reduce machining costs and resource consumption.

However, due to the low heat capacity and relatively high thermal expansion of magnesium alloys, the chips produced during machining are prone to ignition. Moreover, during machining, the relatively large linear coefficient of thermal expansion of magnesium alloys can cause workpiece deformation, resulting in reduced machining precision. When machining magnesium alloys, cutting fluid is used to cool the workpiece, reducing the likelihood of part distortion and chip ignition. Therefore, in the machining of magnesium alloy components, cutting fluid is often referred to as coolant and is one of the factors that extend the tool life.

Proper Proportion of Magnesium Alloy Cutting Fluid: During the machining of magnesium alloys, phenomena such as atomization, splashing, and evaporation can occur. Therefore, it is essential to pay attention to the proper mixing ratio of the magnesium alloy cutting fluid. On one hand, the effectiveness of the cutting fluid may decrease due to some physical changes, and on the other hand, insufficient cutting fluid performance can affect the quality of magnesium alloy machining.

Flow Rate of Magnesium Alloy Cutting Fluid: In the process of machining magnesium alloys, a higher flow rate and pressure can help wash away the chips, keeping the cutting area clean. This contributes to an improvement in the precision of magnesium alloy machining. If the flow rate of the cutting fluid is too low and its performance is inadequate, it can result in rough machining of magnesium alloy products, leading to material and resource wastage, and increased costs for the company.

Effective Cooling: Magnesium alloys have a relatively low melting point. In high-speed and high-pressure machining scenarios, excessive heat can cause workpiece temperatures to rise significantly, leading to deformation of the magnesium alloy workpiece. To prevent such occurrences, it is important that the cutting fluid provides effective cooling, which can effectively reduce the temperature of magnesium alloy workpieces and enhance product quality.

Use of Dedicated Magnesium Alloy Cutting Fluid: It is necessary to use cutting fluid specifically designed for magnesium alloys. General-purpose cutting fluids can easily oxidize, releasing magnesium ions into the cutting fluid. The introduction of magnesium ions disrupts the internal stability of the cutting fluid, leading to stratification. This happens as the concentration of magnesium ions increases over time, ultimately resulting in an uncontrollable situation. Special additives in magnesium alloy-specific cutting fluids effectively prevent the oxidation of magnesium ions.

Additionally, it’s important to be cautious about magnesium alloy swarf (chips) because they can easily ignite when exposed to sparks.

Please note that while this is a translation, it is essential to follow specific safety guidelines and recommendations for handling cutting fluids and machining magnesium alloys to ensure a safe and efficient machining process.

Cutting fluids serve two major functions: cooling and lubrication. Therefore, cutting fluids are often not required when machining magnesium alloys, especially in small-batch production or simple machining processes where dry machining can be more cost-effective and cleaner.

The use of cutting fluid for lubrication may be necessary when deep-hole boring, when feed and cutting speeds are very high, or during large-batch production to provide cooling.  In large production batches, cutting fluid is one of the factors that extend tool life.

(1) Measures in Daily Management:

When processing magnesium alloy parts in designated areas, the work site should be clean, well-lit, and well-ventilated. It is essential to promptly clean up magnesium chips from the work area. Magnesium chips should not be piled up near the machine tools; instead, a designated container should be placed outside the workshop for chip disposal. Each machine tool should be equipped with dry powder fire extinguishers or fire-fighting sand.

(2) Technical Specification Measures:

Choose appropriate cutting parameters and tool geometry to minimize depths of cut smaller than 0.05mm. Maintain sharp tools and ensure continuous cutting to avoid generating thin ribbon-like chips.

(3) Equipment and Environmental Measures:

Whenever possible, employ dry high-speed cutting, avoiding the use of cutting fluids. Allow natural air cooling and provide chip evacuation equipment. Since magnesium alloy powder can produce hydrogen when it comes into contact with water, use mineral oil (acidic cutting agents are strictly prohibited) during production and processing. Machine tools using oil-based cutting fluids should have leak-proof designs. Furthermore, when removing magnesium chips, avoid contact with water as much as possible.