The state of Baden-Württemberg in south-west Germany has established itself as a leading location for high-quality machine tools, while also establishing an impressive reputation in the area of medical instruments.

The town of Tuttlingen in particular continues to enjoy respect as a global centre for medical instruments, making a name for itself in the production of medical devices as early as the 19th century. Several hundred companies work in Europe’s largest medical instrument cluster on innovative products for the medical industry.

One category of such instruments deals with traumatology – specifically, products for the treatment of bone fractures such as bone nails and screws. When fractures occur in hip joints and in the upper and lower extremities, bone screws may be used to compress the fragments and lock implanted intramedullary nails. These nails usually have two transverse bores, via which the nail is secured against dislocation with two screws.

Why do bone screws require deep drilling? When a bone fracture has to be fixed with plates, nails, or screws, a so-called guide wire is positioned in the bone at the point in question. This wire is used to push the bone screw with the deep bore, guiding it safely to the bone so that orientation of the fracture compression can be precisely ensured by screwing in the screws.

TIBO Tiefbohrtechnik, based in the nearby town of Pfullingen, established itself in the high-precision deep-drilling machine market years ago and is familiar with the high standards of quality in the medical instruments industry.

“We know all about the requirements of quality and precision in medical instruments and have no problem meeting our clients’ demands because we use precision parts in our deep-drilling machines,” says Benjamin Röcker, TIBO’s Sales Manager. “We simply do not have any oversized machines – they are expensive, and their performance potential is far above what is necessary. At TIBO, the modular design essentially means that each deep-drilling machine is tailor-made, just like a tailored suit.”

One leading manufacturer of bone nails and screws from the Tuttlingen cluster has partnered with TIBO for designing its process. Because TIBO has delivered deep-drilling machines for other applications for this client in the past, it was clear TIBO would be a competent partner for the bone screws that were to be planned, offering a packaged solution with machines that could fit into compact on-site spaces. In addition, the client expressed the desire for workpieces to be loaded and unloaded automatically so the system could be operated unmanned.

The framework conditions were a bore diameter of 2.5mm-5.0mm with a drill path of 0.06mm for up to 160mm drill depth in titanium alloys (Ti6Al4V) and implant steel 1.4441. Solid carbide drills were used, in which the drill head and drill shaft are manufactured from a carbide blank. This increases the tool’s rigidity and reduces the drill centring and any torsion fluctuation. The clamping sleeves that are soldered to the drill shaft transfer the torque from the machine to the tool. A high concentricity between the drill shaft and the clamping sleeve reduces additional vibrations and improves cutting capacity and process safety.

Deep drilling is the last machining level in the manufacturing process so the bone screws already have their outer geometry. Consequently, workpiece machining and sealing of filigree screw threads and screw heads that have already been slitted are given special attention. The process therefore returns reliable results with steplessly variable tensioning forces, coolant pressures of more than 160 bar, and solid carbide tools.

“Thoroughgoing solutions that put the process within our sphere of responsibility are part of the standard at TIBO,” says Röcker.

As early as the bidding phase, TIBO designers came up with a compelling tensioning concept. Because the wall thicknesses between the bores and the outer contour were as small as 2mm in places and the screw thread and screw-in geometries differed greatly, special clamping sleeves were constructed that could be easily inserted into the deep-drilling machine’s basic universal holders.

The E10 series deep-drilling machine selected from TIBO’s modular system was able to fulfil these requirements, with a vertical supply magazine for a total of 80 workpieces and a gantry gripper for loading and unloading the deep-drilling stations. Intensive communication with the customer and detailed analysis of the numerous workpiece drawings were extremely important for the design of loading and unloading automation processes, and for the necessary clamping equipment in the deep-drilling stations. The process data storage devices integrated into the series’s control units facilitated customer set-up of the wide variety of parts. A single tap on the machine control unit’s touch panel allows the necessary cutting data to be loaded for every workpiece, including defined parameter monitoring.

“That has been our standard for a long time,” says Röcker. “Ultimately, it is our own desire to continuously reduce set-up time, both for mechanical components and for machine control units, so as to remain the leading provider of deep-drilling machines.”