The decision to use an odd number of blades is based on engineering principles derived from aircraft and mechanical engineering in order to minimize resonance frequencies. Symmetrically opposed blades can induce resonance phenomena, while odd numbers help to distribute the resulting forces and vibrations more homogeneously. Furthermore, the probability of imbalance, which can be caused by adhesion of grass clippings, is reduced with an odd number of blades.

This assumption is an overgeneralization. The robustness of 3D printing begins with the careful selection of the material. A knife plate made from high-impact polymers such as ASA can exhibit adequate impact resistance even under high loads, such as contact with solid objects. The rotation speed of almost 3000 revolutions per minute leads to significant forces proportional to the mass of the rotating components in the event of sudden obstacles, so the choice of material is crucial to absorb these forces.

Impact resistance in particular is an important property for materials that are used outdoors in mower disks. ASA is known for its good impact strength, even at low temperatures. Compared to other plastics such as PLA, PETG and ABS, ASA offers the following advantages in terms of impact resistance:

These properties make ASA a preferred material for applications that require high impact resistance, such as in the automotive industry, construction or sports equipment that is subject to frequent shocks and impacts. ASA's ability to maintain its integrity and performance under these conditions makes it an excellent choice for outdoor use.

Innovative design possibilities through 3D printing:

3D printing is revolutionizing manufacturing technology with its ability to create complex structures that would not be possible with traditional methods such as injection moulding. A significant advantage of this technology is the ability to realize highly stable structures through targeted design and the use of finite element methods (FEM), while at the same time saving on material and weight.

Material economy and structural integrity:

An illustrative example of the principle of material economy is the comparison between a double T-beam and a solid beam with a rectangular cross-section. The double-T beam, which is known in the construction industry for its high bending stiffness and load-bearing capacity, uses the material more efficiently by concentrating the mass where it contributes most to the load-bearing capacity - far away from the neutral fiber. This principle can be transferred to 3D printing, where the mechanical properties can be optimized by integrating cavities and specific wall thicknesses.

FEM analysis for optimization:

FEM analysis supports this process by simulating the load-bearing capacity and the behavior of the structures under load conditions in order to adapt the design accordingly. This results in components that offer high strength and stability with reduced weight. The ability to use cavities in a targeted manner makes it possible to create lightweight but highly stable structures that are suitable for demanding applications.

Summary of advantages:

In summary, 3D printing offers the advantage over injection moulding that it enables hollow structural stability with optimized material usage through the integration of cavities and the use of FEM analyses. This results in lightweight but extremely resilient components that are designed for demanding applications. 3D printing uses the principle of material economy, similar to a double-T beam, to achieve a higher load-bearing capacity with less material.

Rigid blades harbor risks, especially with thin material thicknesses (less than 0.5 mm). They can break on contact with solid objects and act as dangerous projectiles. The direct transmission of force to the drive and bearings in the event of an impact can lead to damage and increased wear, which shortens the service life of the robotic lawnmower. Rotating blades, on the other hand, reduce the impact forces and are more suitable for most lawns.

Multiple blades improve the cutting pattern and mulching effect as they cut the lawn more finely. The load is distributed over more blades, which extends their service life. Physically, the arrangement of the blades at the edge of the mower disc increases the moment of inertia, which results in a more stable rotational movement and less interference. For dense lawns or deep cuts, a higher number of blades may be necessary to ensure a uniform cutting pattern.