Because magnesium is lightweight, strong and resilient, it is an excellent choice for components that must be carried by personnel in the field, shot into space, or jostled repeatedly in transportation systems.
- Magnesium is by far the lightest structural material—more than a third lighter by volume than aluminum and 50% lighter than titanium.
- It has superior fatigue resistance.
- Magnesium must have well designed fixturing to hold tight tolerances and high finish quality.
- It has superior vibration damping capacity.
We see an increasing number of requests for machined parts out of magnesium. For example, PEP recently machined an 8” x 11” x 3” block of magnesium into the housing for a hand held military vision system. This component replaced an aluminum design and eliminated four extra pounds of carrying weight. This application was a winning solution for all involved.
However, design engineers considering taking advantage of these properties should also know that there are aspects of magnesium that can make it more difficult and costly to machine:
Heat: Because of its high salt content, magnesium is very abrasive and generates far more heat during the machining process than aluminum. Excessive heat can wear out tools quickly, adding an extra layer of cost to the project. To avoid this, the manufacturer must use sharp, high quality tools. Magnesium itself is more prone to heat distortion and this must be taken into account so that tolerances can be held tightly.
Porosity: Cast magnesium is very porous and should be ruled out for applications such as underwater components where sealing is essential. When a cast work piece is not an option, more material has to be removed to arrive at the desired geometry. This adds machining time and cost; however, it also eliminates the high cost of the tooling for cast parts.
Thin-walled manufacturing processes: Extreme lightweight part designs rely on the removal of a high percentage of material from the work piece, leaving only thin walls to provide strength. The manufacturer must be adept at creating manufacturing processes that remove large amounts of material efficiently without distorting or damaging these structural sections. Advanced CAM and multi-axis machining capabilities are important adjuncts to these processes. If this work can’t be done efficiently with a near-zero scrap rate, then cost and lead times can be impacted.
Finishing: Magnesium cannot be traditionally anodized, so consistently controlled, special processing may be necessary. Your manufacturing resource should have a working relationship with one of the small number of plating companies qualified to both do this work, and to apply effective EMI/RFI shielding to magnesium components if this is required.
Waste Handling: Magnesium chips are considered hazardous waste and therefore must be transported in sealed drums by certified haulers to special disposal facilities—another cost factor.
Precision Engineered Products LLC has many years of experience working with all the complexities of magnesium machining. We are equipped to deal with them from the very outset of a project, so that unanticipated issues do not compromise quality, lead times and costs.