W&H Headquarters - EN
Trendsetting development methods
A high degree of innovation is of vital significance to a company’s international competitiveness. This requires state-of-the-art development methods, which aid the realization of creative product ideas while retaining the focus on the optimal benefit for the user at all times. As a leading supplier in the field of dental technology, W&H has been renowned for the high quality and reliability of its product solutions for 125 years. The utilization of trendsetting development methods allows the company to offer technologically sophisticated product solutions on the market after just a short development period and thus cater to customer requirements all over the world quickly and comprehensively.
The finite element method, or FEM for short, is an innovative tool in the field of development. FEM is a mathematical approach for calculating complex component geometries with multiphysical tasks. W&H has already been successfully employing this simulation method in a wide range of development projects in different fields for some time, including structural mechanics for around 15 years as well as in fluid dynamics and electromagnetics for several years.
The aim when using the simulation programs is to be able to perform technical assessments of new product developments and their versions at a very early stage in the project and consequently reduce the number of prototypes required. In the case of very extensive product tests in particular, this makes it possible not only to make considerable cost savings but also to shorten the development time overall. In addition, it also allows us to launch product updates and new products on the market even quicker and yet still with the expected, high W&H quality.
Development focus on maximal ease of use
In the scope of product miniaturization, the aim is to find the ideal composition of components in terms of the mechanical limits of their materials, e.g., tension, strain and distortion. Ergonomics and user friendliness generally represent further requirements which are decisive for iterative geometry optimization. For example, the W&H FG push-button chuck system is a key component of turbines, and straight and contra-angle handpieces. The part is responsible for the keeping the bur held firmly in position. A minimal size and maximal ease of use for the dentist when changing the bur are decisive aspects of the chucking system.
The term “FG” stands for “Friction Grip” when applied to the chucking system and it is a clamping system in the instrument head based completely on friction and which is composed of two main components: the chuck and the splined sleeve (see illustration). In this design, it is important to find an “optimal compromise” between retention force and actuating force. Employing the FEM method makes it possible to get closer to the maximum stress using geometry optimizations.
Video: FG push-button chuck system
The video shows the equivalent stresses acting on the interacting components (chuck, splined sleeve and bur) when the user actuates the FG chucking system. The visualization of the friction at the contact points can be used to draw direct conclusions about the actuating and retention forces.
Suitable material models and non-linear contact conditions (= including the visualization of friction between two bodies or surfaces) can be used to simulate all the function-relevant steps during actuation of the chucking system in the structural analysis, which displays mechanical loads graphically.
When actuating the chucking system, the user performs the following steps:
- Spreading of the jaws of the chuck via the splined sleeve (actuating force on the part of the user)
- Insertion of the bur
- Releasing of the splined sleeve and clamping of the bur (retention force of the bur)
All the decisive parameters such as maximum stresses in the chuck, compressive stresses at the contact points between the bur shaft and the chuck as well as the splined sleeve and chuck can be easily assessed with the FEM method.
Targeted product optimization employing simulation
The following three illustrations show examples of the equivalent stresses acting on the chuck as they present during use in the dental laboratory. The colours show both the areas with high stresses (red) and those with low stresses (blue).
This makes it possible to calculate the actuating force which is so important for the user. In addition, the retention force is also determined in a static analysis, e.g., when the bur is not running, and dynamically at bur speeds of up to 400,000 rpm. Concentrated analyses of contact areas, e.g., of areas where the actual retention process occurs, make it possible to estimate the wearing behaviour and service life of the W&H push-button chucking system by evaluating contact surfaces and friction forces.
One particular advantage of the FEM method is in the visualization of the stress in the individual components. On the one hand, this makes it possible to identify critical areas, analyse them and then subsequently optimize them, and, on the other hand, it can be used to make the designer more aware of possible interactions. For example, the following images shows chucking systems with different material thicknesses.
Summary
The illustrations show clearly that the simulation can be used to determine the perfect dimensions for components quickly without the need to perform extensive prototype tests. As such, FEM ensures shorter development times and promotes a shorter time to market. Product solutions are available not only sooner but also in the usual, high W&H quality. The simulation-supported product development allows W&H to satisfy the enormous requirements in the field of medical technology and set high-quality and reliable standards on the global dental market.
comments