Punch presses for prototype construction? We haven’t quite reached that stage yet. In practical applications, however, the average lot sizes for punching have been growing ever smaller for a number of years.
The increasing variety of vehicle models in the automobile industry is just one reason for this trend. Punch machine manufacturers are predominantly responding to this situation by continually increasing the speed of punch tool changes. Automatic tool changes, including automatic tool clamping, are key innovations in this context. However, the trend towards smaller and smaller lot sizes also results in a twofold challenge for the manufacturers and users of punch tools: Such tools must be both flexible and cost-effective. In order to achieve these objectives, punching operations generally use the same basic tool for all the individual variants of a part or for several similar parts, simply changing the mold insert for each. Along with the aforementioned flexibility and cost savings, this method has other benefits – for instance, not much storage space is required, as there are fewer tools to manage overall.
At this point, we should also talk about innovative guide and centering elements. Here, we are referring to those that can do significantly more than ensure that the stamp and mold somehow find one another or simply fix the mold inserts in place. The use of innovative systems like these scales up the aforementioned efforts to significantly reduce set-up times and tool costs. What’s more, these systems also simplify many processes and tasks, thus greatly increasing the satisfaction of the employees involved. But one thing at a time!
In many punching operations, the current state of technology involves simple and cheap pinned connections that join mold inserts with a basic tool. To prevent the individual mold insert from having room to move, the pin connections are generally extremely rigid. The consequence of this is that changing the inserts requires a certain amount of force, which not only makes the change difficult and slow, but also results in wear on the tool inserts, as tilting cannot be prevented. After some time, the corresponding bore hole is worn down. This creates play, which first lowers the quality of the punching process and also has the effect of unduly wearing down the stamp and mold. This is particularly a problem with thin sheet metal applications in which the cutting gap is usually extremely small.
The perfect pair – rolling Mini Fine Centering and quick-change guide system
As an alternative to such pin connections, this spring Agathon brought rolling Mini Fine Centering to the market that is almost entirely wear-free. In static applications of Mini Fine Centering, mold inserts can be centered without play and with slight rolling, as well as changed quickly with no tilting. This keeps wear on the stamp and mold to the absolute minimum, which in turn reduces the costs of manufacturing punched parts. Since the molds in punch toolmaking are generally hardened to 60 Rockwell or more, a centering bush is not necessary. The centering pillar and cage are inserted directly into the mold insert. With this variant, very little installation space is required for centering. And because the inserts can be changed in no time without any specialist knowledge or skills, tool maintenance as a whole is also significantly easier. “This not only saves time, but also means much less stress for the employees in question,” says Stefan Nobs, Head of Engineering, Standard Parts at Agathon, who has had several related discussions with customers.
Ideally, Mini Fine Centering should be used in punch toolmaking in combination with Agathon’s quick-change guide system. This ensures that the precision of the punching tools is increased further and wear on mold inserts is reduced even more. In contrast to conventional primary and secondary guides, the quick-change guide system is not pressed into a bore hole in the base plate. Instead, its cone-shaped end fits precisely into a retaining bush that is fixed to the base plate. The guide and bush are screwed together from below. This design allows the guides to be removed extremely quickly so that the tools or mold inserts on the base plate can easily be reground. Afterwards, the guides can be installed again quickly and easily.
The cone-shaped end of the quick-change guide is perfectly fitted into a retaining bush, which in turn offers almost perfect concentricity. This means the quick-change guide system continues to be more precise than other guides even after multiple installations and removals. The entire tool thus works even more precisely, burrs in punched parts occur even less often, and the service life of the stamp and matrix are increased even further.
Mini Fine Centering for variant injection molding
Let’s take another look at Mini Fine Centering. Of course, punch toolmaking is not the only field where this highly innovative solution can be applied. Other areas of application include precision automation – for positioning gripping tools, for example. Here, Mini Fine Centering ensures maximum process safety. It eliminates vibrations and guarantees careful and precise parts removal.
Mini Fine Centering is also increasingly being used in injection mold construction, in particular variant injection molding. In this field, until now the master mold and mold inserts each had to be extensively machined to allow the latter to fit precisely. In addition, changing the mold inserts is anything but trivial and also time-consuming. In static applications of Mini Fine Centering, it will be possible to center the mold inserts without play and with slight rolling – and thus highly precisely – as well as to change them quickly and with no tilting. In this way, the mold and core inserts retain their form perfectly for a long time, which in turn dramatically reduces the costs of manufacturing the injection-molded parts and their variants. Depending on how hard the material of the mold insert is, it may also be possible to do without the centering bush. The centering pillar and cage can then be placed directly into the mold insert. With this variant, very little installation space is required for centering. In other words, the outlook is promising for injection molders who would like to combine maximum quality with cost savings.