Optimisation in mould making

The predecessor company Ralf Grübel Werkzeugbau GmbH was a third-generation owner-managed company from Walterhausen in Thuringia, which Marco Schülken was able to take over as part of a regulated succession. By changing the company name to Schülken Form GmbH, the new owner made it clear that the new brand would also bring a breath of fresh air to this long-established die and mould making company.

In the past, Grübel supplied more than 90 percent of its products to the automotive industry. Marco Schülken has successfully abandoned this lopsided focus. The automotive share is currently less than 25 percent. Today, Schülken Form‘s main clients are companies in medical technology and packaging industries. In the medical sector, the Thuringians boast a strong position in the area of injection moulds for pipettes and blood lancets. Lancets are lancing aids for diabetics. However, now they are also being used for coronavirus tests.
 

„Wir realisieren für unsere Kunden hohe Produktionsmengen innerhalb kürzester Zeit“, erläutert Marco Schülken die Kompetenz seines Unternehmens. Mit hochfahrigen Werkzeugen, die bis zu 128 Kavitäten aufweisen, bewegt sich Schülken Form im absoluten High-End-Bereich des Werkzeug- und Formenbaus. Das wurde auch mit der Wahl zum „Werkzeugbau des Jahres“ in den Jahren 2016, 2018 und 2020 gewürdigt. Seinen Exportanteil hat Schülken während der vergangenen Jahre auf inzwischen über 60 Prozent gesteigert. Das Unternehmen liefert derzeit nach Polen, Russland, Weißrussland und die Schweiz. Der Markteintritt in Singapur und Vietnam wird gerade vorbereitet. In Russland haben die Thüringer 2016  eine Tochtergesellschaft gegründet. 

Neben der Ausrichtung auf neue Märkte wurde bei Schülken Form auch innerbetrieblich gründlich umstrukturiert. „Wir haben im Haus nahezu jede Maschine und jeden Prozess angefasst und dabei sehr viel investiert“ berichtet der Geschäftsführer. Bei diesem Umstrukturierungsprozess war von Anfang an Fertigungsleiter Marcus Vogt mit dabei, den ständig die Frage umtreibt, wie die Performance im Unternehmen weiter verbessert werden kann. Zwar gebe es auch beim Drahterodieren oder Senkerodieren immer wieder mal etwas Neues, aber das Fräsen sei die schnelllebigste Bearbeitungstechnologie. „Man muss hier ständig schauen, womit man etwas verändern und verbessern kann“, so Vogt. 

Schon die Firma Grübel hatte hier auf gute Maschinen Wert gelegt und setzte zum Fräsen ausschließlich Bearbeitungszentren von Hermle ein. Allerdings arbeitete dieser klassische Werkzeugbau noch eher wie ein Handwerksbetrieb. Ihre Programme haben die Mitarbeiter selbst direkt an den Maschinen erstellt. Vogt sah hier dringenden Handlungsbedarf: „Bevor wir an die Fräswerkzeuge herangegangen sind, haben wir die ganze Prozesskette überarbeitet. Wir haben Programmierarbeitsplätze eingerichtet und die komplette Fertigung auf ein neues System umgestellt.“
 

The next step was to approach the actual technology with the key question of how the parts could best be machined. “The classic way in toolmaking is, after all, either pre-milling, hardening and subsequent grinding or die-sinking EDM”, says Vogt, describing the initial situation. In order to make production more flexible depending on the manu­facturing workload, Schülken has added hard milling. Although parts are still manufactured using the traditional method in Waltershausen, starting the milling process immediately after hardening no longer poses a problem, especially when things have to move quickly. “Today, we’ve reached the point where we can choose a lot of machining operations according to the workload of the individual departments,” Marcus Vogt enthuses.

This was not the end of the optimisation measures, though. When Schülken Form was looking for new milling tools for high-feed roughing, it was around the time that MAPAL began to enter the Die & Mould sector. Similar to Schülken, the precision tool manufacturer from Aalen had set itself the goal of reducing its dependence on the automotive industry by exploring other sectors.
 

In the future, MAPAL has set a clear focus on market segments, explains Uwe Rein, Sales Director Die & Mould MAPAL. Besides the traditional Automotive sector, he particularly cites the segments Aerospace, Die & Mould sector and General Machining. “We operate very selectively and systematically in the Die & Mould sector”, says Rein. For three years, the company has been working towards market entry in September 2020 and has developed a product range especially for this segment. The result is a specialist catalogue with around 6,500 articles. 

Unlike the automotive industry where MAPAL has been very successful for many years, particularly with custom tools for large quantities, the requirements of the Die & Mould sector initially appear to be quite different. The focus here is always on individual pieces or small batches, which need to be machined with standard tools as far as possible, so that the companies can process a wide range of orders with these. However, a change has also begun in classic toolmaking, and this is already clearly visible at Schülken Form.

“The trend is towards industrial toolmaking”, Marcus Vogt sums it up. “In the past, all we cared about was releasing a decent part. Nowadays, we also have to look at the times.” Digitalisation and automation are also filtering into the Die & Mould sector. Vogt schedules the manufacture of all parts for each department with a specific time in advance. It may not be a matter of seconds, but it is still a matter of minutes. Process reliability plays an increasingly important role when it comes to achieving the specified times.

The materials that have to be machined are becoming more and more challenging. Today, stainless steels with a chromium content of 13 percent are common, resulting in increased tool wear. The ductility of new powder-metallurgical steels also imposes a challenge. Here, dimensional accuracy and surface finish are important aspects.
 

The bar was already high when Schülken tested the OptiMill-3D-HF-Hardened, the first MAPAL tool. Due to its special lens head geometry, this high-feed milling cutter made from solid carbide is suitable not just for roughing, but also for high-gloss finishing of planes in hardness up to 68 HRC. This matched Marcus Vogt’s requirements: “We don’t want a special tool for a special machining operation. I always choose tools that allow me to tackle several areas. These are exactly the kind of solid carbide tools that allow me to do both hard and soft roughing.”

The results achieved with the solid carbide high-feed milling cutter were immediately impressive, resulting in this roughing tool with its higher performance being included in Schülken’s standardised tool list instead of the previously used tool from another manufacturer. The Manufacturing Manager limits his tool set to 300 different types and claims to be able to meet all requirements with it – even though no two parts are the same. “From now on, we don’t use any other tool than MAPAL’s milling cutter for the corresponding applications,” says Vogt.

This also applies to the next tool Schülken subjected to a comparative test: the finishing milling cutter OptiMill-Har­dened-Finish, which can finish up to 68 HRC surfaces with a 3xD ap material removal rate in one cut. Vogt describes how enthusiastic the machine operators are: “When it comes to finishing hardened high-alloy tool steel 1.2083, the milling cutter impressed greatly with superior surfaces and a long tool life. Among other things, small pockets are milled to fit with this tool.” After the two solid carbide milling cutters, Schülken is currently testing a high-feed milling cutter with indexable inserts: MAPAL’s NeoMill-4-HiFeed-90, whose positive cutting edges produce a soft cut.
 

In close cooperation with MAPAL, Schülken is also venturing into areas that were previously considered extremely problematic, e.g. deep hole drilling in hardened steel with cross bores. With this, the company from Thuringia is crossing the final frontier to produce a completely hardened mould insert. Thanks to several saved machining steps, Schülken has now halved the machining time for these mould inserts to two weeks. The drill is a good example of MAPAL’s customer-oriented tool development.

Bei einem Durchmesser von 8 mm schafft er Tiefen von 20xD und weist einige Besonderheiten auf. Er hat eine speziell geformte Spannut, die den Bohrer gegen Verdrallen stützt und das Werkzeug sehr stabil macht. Die Nut verleiht dem Span eine ganz eigene Form, welche die Spanabfuhr unterstützt. Die Pyramidenspitze unterstützt das Anbohrverhalten nach dem Durchbrechen der Querbohrungen maßgeblich. Das Werkzeug stützt sich über vier Führungsfasen in der Bohrung ab und übernimmt die Führung, wenn die Spitze sich gerade in einer Querbohrung befindet. Einziger Wehrmutstropfen: Dieser Bohrer ist derzeit noch ein Sonderwerkzeug. Bei entsprechender Nachfrage erwägt MAPAL allerdings, ihn in sein Standardsortiment aufzunehmen.

Schülken demands performance in more than just machi­ning, as Vogt explains: “When it comes to selecting tool suppliers, we want the tools to be available immediately, and that if a problem ever arises, I want to have a contact person who knows what they’re talking about.” This contact person is Product Specialist Felix Wendler, who is responsible for the Die & Mould sector and is based at the MAPAL site in Meiningen. He considers it important to be on site with the customer, especially when testing new tools: “I like to hear how the tool sounds during machining. One can deduce a lot from that. When I see and feel surfaces, I can tell what needs to be changed to make it work better.”

MAPAL’s logistics concept ensures that the standard tools are quickly replenished. Of around 6,500 items that are in the catalogue for the Die & Mould sector, the majority are available within 24 hours. Somewhat more specialised dimensions can be delivered within five days. This is very convenient for Schülken Form, which has less and less time to produce its complex injection moulds.