machining of magnesium

Why Use Magnesium?

Magnesium is for fourth most common element in the earth and makes up around 13% of our planet’s mass, but only occurs naturally in combination with other elements.

Magnesium and its alloys are a material growing in popularity within the engineering sector. This is primarily down to its attributes as a strong but lightweight material. Magnesium is the third most commonly use structural metal after Iron and Aluminium and historically has been used in applications including German Aircraft during World War 1. It is becoming much more common that Cast and Fabricated Magnesium Alloy parts will undergo CNC machining, but this is not a speciality that all machinist will be familiar with.

Machinability

Magnesium has a lower resistance to cutting, meaning it requires less power (around 55% of the power required to cut Aluminium) and will produce less tool wear. You can produce an excellent surface finish working with Magnesium, and this finish will not be influenced as much by the speed of cutting as it is the feed rate. If fine feeds are required to achieve a fine finish then the cutting speed should be reduced so as to avoid excessive generation of heat. The same is true where you are machining thin walled section which may result in excess heat.

In terms of Tool Material itself Carbide tools are often recommended and will have a significantly longer tool life when cutting Magnesium when compared to the likes of Aluminium. Polycrystalline Diamond (PCD) cutters could also be considered. Generally speaking you can machine Magnesium without the need for coolant, if coolant is necessary a light mineral oil will suffice. Never use a water based coolant as it will react with chips during storage.   

Dangers

Many machinists who will have encountered Magnesium know about is potential to combust. Even fine Magnesium dust is highly flammable and so it’s important to keep cutting tools sharp, dispatch chips frequently and store in steel closed containers. A Magnesium fire is usually white in appearance and it’s very important never to extinguish a fire with water as this will form Hydrogen which in itself is easily ignited. Safe storage of Magnesium parts are key as they can self ignite and cause major damage. 

Sub-Contract

If you are unfamiliar with Magnesium then it makes sense to send out components to a reliable sub-contractor. B&B have experience with Magnesium Alloy parts as well as Cast Magnesium and provide competitive prices in small to medium volumes.

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