Magnesium Lightweight Design ThinKing August 2020 - From Heavy to Light with Magnesium
Circular table saws are not necessarily a typical field of activity for lightweight design, as they must be stable and heavy. Torun Bark Magnesium GmbH shows why lightweight design still makes sense here and even brings advantages for users and the environment with gantries and table tops made of die-cast magnesium.
The Baden-Württemberg State Agency for Lightweight Design will present this innovation with its ThinKing in August 2020. With this label, Leichtbau BW GmbH provides a platform for innovative products or services in lightweight design from Baden-Württemberg every month.
At a glance:
- Lightweight: Approximately 10 % weight saving due to a weight reduction of more than three kilograms compared to die cast aluminum
- Material efficiency through design optimization
- Cost-effective: Production shortened by one process step
- Handling of the saw is simplified
"Magnesium is a lightweight material due to its low specific density alone. But the real innovation lies not in material substitution, but in the weight-optimized design and manufacture of the panel," says Dr. Cyrus Bark, Managing Director of Torun Bark Magnesium GmbH.
The plate is a challenge due to its size alone, because magnesium plates produced by the company to date are significantly smaller. It measures about 45 x 75 x 1 cm and has a recess that makes production more difficult, in which the saw blade is later guided. The gantries, in example the underframes, as well as the table top of the circular table saw are made of die cast magnesium.
"The component geometry of the table top was a special task here, because it must be pot-flush in order to guide the workpieces cleanly during sawing. In addition, the surface quality of the top is also decisive, because the impression of quality that the power tool makes is an important criterion for professional users such as carpenters, joiners and cabinetmakers at Festool GmbH, a premium manufacturer of power tools," reports Bark about the specific requirements for this component.
Flatness is Achieved by Cooling Alone
Very often these plates for table circular saws are made of aluminum, the surface is CNC machined and coated after die casting. At Torun Bark Magnesium GmbH the flatness of the magnesium plate is not produced by additional machining, but by "pre-stressing" in the die casting tool. This eliminates a costly machining step in the production of the component.
"We cast the component in the die casting tool in a deliberately crooked manner so that it is straightened when it cools down following the casting process and is then absolutely flat," Bark describes the manufacturing process with a smile: "This means that the surface does not have to be reworked, but only receives a powder coating that protects it from corrosion.
Design Optimization Saves Resources
This has been achieved through an innovative gate design and - based on several simulations - an optimized, sophisticated and thin-walled component design. In places, the wall thickness is less than 1.5 mm.
For the necessary stiffness there are ribs and honeycomb structures on the underside of the plate. These structures not only increase the stability of the plate with significantly less mass, but also, together with flow aids such as the so-called "crow's feet" in the die casting process, ensure optimum distribution of the molten metal in the mold.
Light, but Not Too Light
The plate produced in this way is particularly thin-walled and therefore not only light but also material-efficient. Compared to the aluminum plates weighing almost four kilograms, the 2.5 kg magnesium plate is over 30 % lighter. Together with the portals made of die cast magnesium, this results in a total weight reduction of more than three kilograms - for the entire circular table saw, this represents almost 10 % of the total weight of around 45 kg.
This is because stability and mobility must be finely balanced in this application. For mobility on the construction site, the weight reduction means a noticeable relief. Nevertheless, the circular table saw remains heavy enough overall and thus provides the stable stability required for sawing.
Magnesium - The Specialist among Lightweight Design Materials
In order to use magnesium as a lightweight design material in a meaningful way, certain key factors are required. The material is ideal if the component is to be particularly light. This is achieved by the low specific density of magnesium and the possibility of thin-walled design. In addition, the non-ferrous metal is 100 % recyclable and very temperature-resistant. However, unlike aluminum or GRP, it is susceptible to corrosion. Moreover, components produced by die casting generally only pay off from medium to large series.
"The experience we have gained with these components can also be transferred to other industries. Until now, the material has not been approved for use in aviation, for example. But today there are flame-retardant magnesium alloys that can also be die cast, opening up further areas of application in civil aviation and electromobility, among others," says Dr. Cyrus Bark, giving an outlook on the future of the lightweight material.