"Materials competence always means standards competence"

Punching and fineblanking are used to produce punched and fineblanked parts in a complete cut or by means of follow-on composite technology. The tools used for these processes usually involve many different work steps and are highly precisely coordinated with one another. However, before the respective tools can be built, etampa AG, a Swiss punching specialist from Grenchen (Canton of Solothurn), has to make at least equally precise considerations and trade-offs. If the greatest possible care were not taken here, the consequences could be disastrous - in the worst case even life-threatening, since the finished parts are installed in braking systems or medical devices, among other things. Particularly in demand, therefore, are the design and construction departments, which not only have to think "around the corner" in the truest sense of the word when creating the strip pattern. And of course, quality planning is also required, because at least as many considerations apply to the materials from which the parts to be manufactured are to be made.

Active co-engineering

At the beginning of a new project, there is always a drawing that reaches the manufacturer at a different early or late product or part planning stage. It is the basis of the part to be manufactured and must be thoroughly put through its paces. Many customers place the highest value on the active co-engineering and extensive experience of precision manufacturers. And the earlier they are involved in the planning and design process, the better. Imad Hussain, Head of Quality Assurance and Quality Management Representative of the company: "The customer drawings always include material specifications. These result from various tests that the customers have carried out in advance in their test laboratories to check the mechanical, electrical and chemical properties of the materials; these are, for example, fatigue, durability or load tests."

Understanding requirements

Daniel Brügger, etampa CEO: "We must never change materials defined by the customer on our own authority, as the selection and definition of tools often takes a very long time. This is precisely why our customers value our expertise and technical input at an early stage, because we can of course also advise on material planning and because productions can be realised more optimally and also more quickly as a result. The prerequisite for this is that we have a precise understanding of the requirements and functionality of the parts to be produced, only then can we go to the parts planning stage, make recommendations and specify appropriate functional tolerances and test specifications."

Materials expertise is always also standards expertise

Hussain: "It is extremely important to question not only the punching design, but also the choice of material in connection with it: Why is stainless steel used instead of steel or stainless steel? Why does the material have to have the specified hardness? How can material properties influence product qualities? " The Swiss also demonstrate their metallurgical expertise during on-site customer visits, among other things. Hussain continues: "With one customer, there were discrepancies because of the specified hardness of the steel. On his drawing, the hardness was specified as 110 HV Vickers hardness, but we always work with a hardness of 123 HV. We advised the customer that it was essential to increase the hardness. The tensile strength and hardness of the raw material acting on the coil from which the parts are punched out are simply too great, and during mechanical processing, i.e. punching and bending, the hardness increases again." As a result, he says, the customer adjusted the hardness levels and changed both the internal standards and the drawing. Hussain: "It clearly depends on the right planning. Materials expertise always means standards expertise as well."

Too narrow tolerance zones are really expensive

Not only the material, but also a jointly developed, punch-optimized design has a lasting influence on the tool design, on regrinding cycles and the service life of the tools. And of course, the effects on the quality of series production itself should not be underestimated. Brügger: "We tell our customers if minor changes to the original part design would significantly increase productivity. And we naturally point out if we could produce the part to be manufactured more cheaply by changing the tolerances, while of course maintaining the same quality." Again and again, they would find that customers choose tolerances on the parts to be manufactured that are far too small, and that, according to Brügger, costs a really lot of money: "Just by moderately adjusting the so-called 'scare tolerances' to a normal value, we've been able to save our customers real cash time and time again."

Material selection as the key to success

Marco Costa, a passionate designer and head of design at etampa for 20 years, also knows this topic only too well: "Quality optimisation can by no means only be achieved by producing in multiple lanes, making optimum use of the strip and optimising the use of raw materials by this alone. There's more to quality planning, and many customers underestimate the interaction of material selection and the punching or fineblanking process." Recently, he says, a customer brought him a stop valve that had originally been turned once and was now to be stamped. A prototype was created - and then the same part was produced again using fineblanking. The result: The surface was harder, smoother, and the repeatability was extremely high. Overall, this type of production meant less effort, but the functionality was significantly better than with the turned part. This makes planning really fun!

Feasibility analysis: Exactly one attempt

Once the design drawing has been produced and the material question has been clarified, the next important and above all indispensable step is the feasibility analysis. Because one thing is certain, Brügger emphasizes emphatically, and clarifies the great responsibility that is pronounced with the determination of the feasibility of a production part: "We have exactly one test. Once we have said that we are committed to feasibility, we cannot later revoke this statement - certainly not with reference to a previously unfinished or inadequate drawing. It's our responsibility to consider all design and production contingencies up front and take them into account accordingly when making a feasibility statement." In each individual case, he says, you have to weigh whether a part can be manufactured the way the customer envisions it. This also includes assessing whether the desired forming that the part to be manufactured entails is at all logical and feasible, and whether the individual work steps are also laid out in the correct sequence. Brügger: "Precision is the top priority in our company."