Tool design – 7 factors to a better tool

The success of any tool is in the planning. From the receipt of the customer’s drawing to the finished tool, tool design plays a decisive role. A clever design can reduce the costs of tool production and simplify or completely avoid possible corrections to the tool. Ultimately, a clever design also helps the production to produce with a tool trouble-free, economically and in the required quality.
1 The pencil concept
Despite all the technical aids, every tool concept starts with paper and pencil. Based on the customer’s drawing, the designer creates an initial concept. Decisions such as the positioning of the workpiece in the tool, the choice of the cutting sequence, the placement of centring forks, finder pins and other active elements, the sequence of bending operations and the choice of suitable tool monitoring systems are all incorporated into this. Through variations of different solutions and selective improvements, the concept is refined more and more in several steps. Finally, this is presented and discussed in a joint concept meeting with participants from the areas of design, toolmaking and maintenance as well as production. In this way, everyone who will later come into contact with the tool is involved in the design process. At this final concept meeting, input and new ideas are once again received from all sides, which ultimately complete the tool concept.
2 The physics of stamping and forming
A customer drawing not only tells us the appearance and dimensions of the desired part, but also another important physical parameter: the material. For the design of the tool, the tensile strength is of particular importance. Depending on the magnitude of the tensile strength, the cutting gap and the holding-down force required to obtain a clean cut change. Bending forces are also calculated based on the bending line and the tensile strength. These values serve as a basis for the choice of materials and panel dimensions in the design. Based on the hold-down force, appropriate springs can be selected, which in turn influence the space requirements. A balance must be found between the number and size of the springs. Ultimately, it is up to the experience of the designer to interpret these values correctly and to incorporate them into the design.
3. the proof of the pudding is in the eating
Unfortunately, physical calculations are not always precise enough. A bending test is absolutely necessary, especially for the deflection of bends. The external influencing variables such as the rolling direction of the material, the surface and geometry of the bending tool or even just the after-treatment of the raw material can have large differences to the calculated values. Therefore, a bending test with the respective material is a must. With the help of various bending moulds and devices, we are able to carry out these tests quickly and easily in our workshop. In addition, we are supported by our material warehouse, where we have access to almost all common materials and thicknesses.
4. standardised tool design
Standards take a lot of effort away from everyone involved. Through our internal standardisation, the tool structure has been unified and standardised. The designer does not have to think about the structure of the tool, as this has already been improved, tested and finally standardised several times. For the toolmaker and the tool maintenance department, it is therefore not necessary to think about each tool anew; everyone knows the standard structure and can estimate how and where an individual component is used. In addition, production benefits from the uniform operation of the tools. All machines are equipped with centring systems that automatically bring the tool to a predefined and aligned position. In addition, the clamping elements are also standardised, allowing quick changeover of the production machines.
5 DFM and Poka Yoke
The costs of tool production can be significantly influenced during the design phase. According to the basic idea of “Design for Manufacturing” (DFM), these are already kept low during the design process. The manufacturing of the parts is also considered at an early stage. Is a separate screw connection and pinning really necessary or can the component also be positioned and fastened via an adjacent component? Does a clearance necessarily have to be produced from the side or can it also be machined from above, where other machining operations are still taking place?
For assembly and later also for tool maintenance, there is another concept: Poka Yoke. This Japanese expression can be translated as “avoiding unfortunate mistakes” and describes the possibility of incorrectly fitting components in the tool. To achieve this, care is taken in the design of the tool to ensure that each component can only be mounted in its specific place and in the correct orientation. By means of shape coding and asymmetrical construction of the components, an unambiguous installation method can be enforced, which means that a tool is always reassembled in exactly the same way after disassembly.
6. in-house standard parts
If standard parts can be used in the mould, this has many advantages: Standard parts do not have to be drawn, can be produced in larger quantities and are usually available from stock. However, some standard parts that we use in our moulds cannot be found at the numerous standard parts suppliers: our own Schmid standard parts. These are partly our own developments, resulting from the everyday need for solutions for our tools. Some standard parts are also further developments of existing standard parts. In addition, we have succeeded in standardising and accelerating the design and production process of our tools by standardising semi-finished products.
7 The right material
In addition to the dimensions, a material must also be defined for the components of the tool. The designer can choose from a variety of different materials, each with its own characteristics in hardness, strength and machinability. In addition, various materials are suitable for further post-treatments such as hardening, nitriding or coating. In addition to the classic rolled materials, we use so-called powder-metallurgical steels for highly stressed components. These have a very homogeneous structure due to their manufacturing process and therefore have better strength. Our own stock of tool steels in various dimensions also ensures standardisation here. Thanks to our know-how in the use of different tool steels and the cooperation with our suppliers of finishing treatments, we always find a suitable solution for our tools.