Surface World May 2019 Surface World May 2019 | Page 70

PRODUCTS & PROCESSES driving comfort, noise minimisation, weight, durability, power transmission, accuracy of fit, frictional resistance, stability, turning circle and corrosion resistance are all optimised so that the drive shaft efficiently fulfils all these requirements to the greatest possible degree Only when the shaft has proved its perfect performance in subsequent laboratory and practical tests does it go into serial production. Always scalable to demand Whether it is a longitudinal, side or cardan drive shaft – the process always begins with a customised concept. On the basis of detailed customer specifications regarding shaft centre distance, material, form and type of connection, torque, weight and performance, Neapco’s experts develop a design which they agree on with the customer’s engineering team. One of the Düren-based company’s basic principles is always to make the front shafts the same in order to avoid differences in vibration. In order to follow up on the pure idea by presenting their customer with an initial result as soon as possible, Neapco combines mechanical and virtual procedures in the development stage. Quick decision processes enable the specialists to prepare prototypes very rapidly and put them into serial production. For example, in its prototype shop, Neapco may mill components like bell or tulip housings from solid blanks for test assemblies or for pre-tests, or perhaps occasionally weld together shafts just to get a first impression. Even jobs like rotary swaging can be performed at short notice thanks to access to the in-house production line. It is because of this enormous flexibility and job-based scalability that Neapco, a relatively medium- sized company in German terms, can successfully hold its own against strong competitors. In multi-stage tests, the prototypes are then subjected to up to 2,500 test cycles which are conducted according to the detailed specifications of the customer. But the shafts are not only put through their paces in Neapco’s own test facility. In addition, when close to serial production, their efficiency, functionality and durability are checked in real-world operation on the test ground and in road tests. Surface coating at the drop of a hat Anywhere from 50 to 200 prototypes are constructed for each shaft before it is ready to go into serial production, which at Neapco may involve the manufacturing of just a small batch or in large quantities depending on the particular intended use. On average, the company delivers up to 5,000 individual assemblies per year – complete systems consisting of drive shafts with joints and collars. Manufacturers of premium brands in particular expect the shafts to have corrosion-resistant coating, even in the prototype stage. But the special coating is also expected to give the components the high-value look of the later serial products. This is an elaborate and always extremely time-sensitive job, for which Neapco identified the surface engineering company Pallas as an eminently suitable partner. For many years now, the automotive supplier has been relying on the comprehensive procedural competence of the surface treatment experts at Pallas with regard to its tool-making needs. Whether these needs are for the coating of worn-out bearings with hard metal, or hard chromium plating as protection against wear or corrosion for shafts, or non-stick coating for filling machines – thanks to the wide range of equipment, working materials and procedures at its disposal, Pallas is always ready with the optimal solution for every task and is able to do the job practically at the drop of a hat. Depending on the specific procedure and working material, coating thicknesses from just 20 microns up to several millimetres can be achieved. Due to the lack of restrictions on base materials and a virtually unlimited choice of coating materials, thermal coating has a very versatile range of application. By combining several thermal spraying methods, in many cases Pallas actually improves the efficiency of the surface treatment even further. Cost-intensive components, time-sensitive functions or required enhancements of the properties of the components often make having such thermal coatings done by Pallas the only viable option. And these years of proven experience in the creation of customised thermal coatings are what made Pallas the perfect choice to also handle the surface coating of the drive shaft prototypes for Neapco. The first challenge related to the low- distortion application of the electrostatic powder coating. To preserve the dimensional accuracy of the hardened shaft, Pallas first had to find a powder that melts at a low temperature. Normally, powders are used that melt at temperatures of 180°C and higher. But, in the coating of the drive shafts, under no circumstances was a temperature of 160°C to be exceeded in order to stay below their annealing temperature. As a qualified expert for coating materials, Pallas helped the automotive supplier with the selection of a suitable plastic powder. A second challenge relates routinely to the extremely laborious manual masking before the coating process. Many a surface coater has already thrown in the towel due to the sheer number of inaccessible places and special masking requirements. Each component needs masking with a variety of special masking tapes – a very time- consuming task. In the case of shafts for electrically powered cars, the specific challenge is that, instead of the usual radial masking, covering of the upper surface has to be ensured. Thanks to its great experience and the range CONTINUED ON PAGE 70 68 MAY 2019 twitter: @surfaceworldmag