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.
 

自動車業界全体に言えることですが、部品に対する精度要求は非常に高くなります。 「この部品はアダプターフランジだけでなく、トランスミッションの後部も含まれます。 したがって、ベアリング シートには最高度の精度が必要です」と Schlote社 の作業準備チーム リーダー、Sebastian Swiniarski 氏は説明します。 この部品には公差の異なる多数の穴が必要であるため、1,000 分の 1 ミリメートルの精度で製造する必要があります。

MAPALとSchlote社は、長年にわたる効果的な協力関係を振り返ることができます。MAPALは、PCD フライスカッター (シーリング材を塗布する面の荒面を製造する)、タップドリル、リーマー、多様な穴あけ工具の供給を委託されています。 「当社は、プロセス全体の開発を含む包括的なソリューションをお客様に提供しています」と MAPAL の Schlote 技術顧問、Stefan Frick 氏は述べています。

納品されたツールは注意深く管理されていました。 Harzgerode 工場の稼働以来、潜在的な弱点を見つけて製造を最適化するために分析が継続的に実行されてきました。 この継続的な改善プロセスの中で、Schlote 社と MAPAL は共同して、長年にわたる工具寿命の延長、工具支出の削減、生産量の増加を達成してきました。 量産初期は 1 日あたり最大 3,600 個の部品が生産されていましたが、現在では追加の機械を必要とせずに、 4,500 個の部品製造をするにまで引き上げられました。

最新の最適化には、トランスミッションのギア部に使用されるオイル チャネルの深穴の加工です。 「工具管理システムを使用して、どの工具をどのくらいの頻度で交換する必要があるかを毎月評価しています」と Swiniarski 氏は報告します。 「深穴用のドリルは特にセンシティブです、これらのドリルは比較的コストが高価のため、ツールのコストを削減するために、深穴用のドリルに集中しました。」 切れ味が鈍いドリルでは穴の出口にバリが生じるため、品質面は工具の摩耗にも影響します。

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.
 

Clutch housing manufacturing at the site was planned to last at least eight years with a peak output of 1.1 million parts per year. This peak was surpassed in 2020. Production has been ongoing for five years in the meanwhile with 900,000 parts produced per year.

Due to continuously improved productivity and the lower production quantities, there has been time to address future trends and produce different parts. The factory is already being modified for this purpose. The first of two new projects involves six different parts that Schlote is to produce for a hybrid model of super sports car manufacturer.

In the other project, Schlote’s expertise as a clutch housing manufacturer is once again called for – this time for an electric car. Schlote draws from the trend toward electric mobility by supplying e-cars with transmissions as well. For an innovative model with three gears, the connection between engine and transmission is to be produced in Harzgerode. Half of the factory capacity is currently being converted. The production of parts for combustion engines is to be ramped down to 50 per cent. In future, hybrid cars will account for 10 per cent and purely electric mobility for 40 per cent. Schlote has already produced the first parts for the new projects.