The best deep bores with PCD

Schlote’s story begins in 1969 as a small workshop in Harsum, where the company is still headquartered. Today 11 companies with 1,800 employees belong to the Group. The OEM has eight factories in Germany as well as further manufacturing facilities in the Czech Republic and China. Schlote Group customers include big car manufacturers, system integrators and foundries. Schlote’s turnover stems from engines (55 per cent), transmissions (39 per cent) and chassis (6 per cent).

A successful cooperation with Trimet Aluminium already existed at other sites, manufacturing finished car components from cast blanks. The awarding of a contract for a component by a major OEM, which would involve very high quantities, led to a joint venture between Schlote and Bohai Trimet in Harzgerode.
 

The part being manufactured in Harzgerode is a clutch housing made of die-cast aluminium. A single version of the automatic transmission is being delivered to various major car manufacturers, where they are predominantly installed in vehicles with two-litre engines. The bell housing connects the transmission to the engine. While the transmission side is the same on all the clutch housings, the other side is adapted to the respective car manufacturer’s engine. The differences are mostly small, so the bell housing construction is 99 per cent identical for all of the car manufacturers.

Schlote Harzgerode GmbH is producing 4,000 parts per day currently. At over 80 per cent, the modern factory exhibits a very high degree of automation. Around the clock five days a week, 120 employees work at the Harzgerode site. Production can be expanded to six or seven days a week if need be.
 

As is the case for the entire automotive industry, the requirements placed on parts are very high here. “The part is not only an adapter flange, but also the back of the transmission. The bearing seats thus require the highest degree of precision”, explains Sebastian Swiniarski, Work Preparation Team Lead at Schlote. The part requires many bores with different tolerances, whereby precision manufacturing is needed down to the thousandth of a millimetre.

MAPAL and Schlote can look back on many years of effective cooperation. MAPAL is therefore entrusted with supplying PCD milling cutters (which create the defined rough surfaces on which sealant is applied), tap drills, reamers and an array of diverse drilling tools. “We offer our customers comprehensive solutions including the development of entire processes”, says Stefan Frick, MAPAL’s technical advisor to Schlote.
 

A watchful eye was kept on the implemented tools from the very beginning. Since Harzgerode went into operation, analyses have been performed continuously to find possible weak points and optimise manufacturing. Within the context of this continuous improvement process, Schlote and MAPAL have together managed to achieve longer tool lives, lower tool expenditures and higher production quantities over years. While 3,600 parts were produced at most per day in the beginning, the limit has now been raised to 4,500 parts – without the need for further machines.

The newest optimisation involves deep drilling for oil channels used to change gears in the automatic transmission. “We evaluate every month with our tool management system which tools have to be exchanged how often”, Swiniarski reports. “Time and again, the deep drills have proven to be particularly sensitive. As these drills are relatively cost intensive, we have concentrated on them to further cut our tool costs.” Quality aspects are also inherent in tool wear as a blunt drill produces burrs at the bore exit.
 

For the new tool, MAPAL started with the existing solid carbide drill and inserted a PCD cutting edge at its tip. The structure of the tool is reminiscent of a concrete drill with a carbide tip. The manufacturers in Harzgerode are very happy with the PCD deep drill’s tool life. While the solid carbide drill’s tool life ends after 2,500 parts, the PCD version keeps going reliably up to 15,000 parts. There is further scope for improvement in machining challenges, such as blowholes in the material and varying casting quality. The partners are currently working on this together. “We have occasionally been able to achieve a tool life of 40,000 parts. Naturally, we want to make this ultra-long tool life the norm”, Frick stresses.

The cutting data is the same as that of the solid carbide drill at a spindle speed of 8,700 rpm, a feed of 0.3 mm/rev and a cutting speed of 218 m/min. The new drill’s potential lays in its considerably longer tool life, the resulting lower tool costs and the higher process reliability. Less tool changes also means less machine downtime.

Production at Schlote in Harzgerode involves a total of ten manufacturing cells. Each cell is made up of three machines from the manufacturer SW, two W06 double-spindle machines and a one6 single-spindle machine. The parts are machined in three clamping setups, whereby the double-spindle machines handle the first two setups and finishing takes place during the third.
 

Die Fertigung der Kupplungsgehäuse am Standort war als Projekt mit einer Laufzeit von mindestens acht Jahren und einer Peak-Stückzahl von jährlich 1,1 Millionen Teilen ausgelegt. Der Peak wurde 2020 überschritten. Mittlerweile läuft die Produktion des Bauteils im fünften Jahr und liegt bei 900.000 Stück. 

Zusammen mit der kontinuierlich verbesserten Produktivität erlauben es die sinkenden Produktionsmengen, nun Zukunftsthemen anzugehen und erstmals auch andere Bauteile herzustellen. Dafür hat der Umbau des Werks bereits begonnen. Im ersten von zwei neuen Projekten geht es um sechs verschiedene Bauteile für ein neues Hybridmodell eines Herstellers von Supersportwagen, die Schlote produzieren soll. 

In einem weiteren Projekt ist wieder die Kompetenz des Fertigers bei Kupplungsgehäusen gefragt – dieses Mal allerdings für Elektrofahrzeuge. Schlote profitiert hier von dem Trend in der Elektromobilität, auch E-Autos mit einem Getriebe auszustatten. Für ein innovatives Modell mit drei Gängen soll die Verbindung zwischen Motor und Getriebe aus Harzgerode kommen. Die Hälfte der Hallenkapazität wird derzeit umgebaut. Die Fertigung von Teilen für Verbrenner wird auf 50 Prozent heruntergefahren, zehn Prozent sollen künftig auf Hybridfahrzeuge entfallen, 40 Prozent auf reine Elektromobilität. Erste Bauteile für die neuen Projekte hat Schlote bereits hergestellt.