Slot broaching in the medical industry
Narrow slots, long tool life and a favourable cost per cutting edge? With the expansion of its slot broaching system, HORN demonstrates how the shaping process can be used economically in small diameters. For field tests, HORN looked for customers with special components and high quality requirements. A key component of a medical endoscope was ideally suited to this. The contract manufacturer Öschger GmbH from Emmendingen agreed to participate in the long-term tool tests and was impressed by the performance of the new system.
Medical endoscopes are important in modern medicine and are used for minimally invasive diagnostics and therapy in numerous medical disciplines. They enable the optical visualisation of body cavities and organs in real time and contribute significantly to the reduction of surgical trauma, shorter recovery times and increased patient safety. Technically, endoscopes consist of precise optical components, illumination units, mechanical structures and, increasingly, digital image sensors that provide high-resolution image data. Depending on the application, rigid or flexible designs are used, with flexible endoscopes having complex internal channels and movable segments. The materials used must be biocompatible, sterilisable, durable and meet strict requirements.
Customer question to HORN
Several customers approached HORN to ask whether the existing 117 slot broaching system could be extended to accommodate smaller bore diameters. Previously, the minimum machining diameter was 14 mm (0.551"). For applications below this range, the Supermini 105 system was used from 6 mm (0.236") and Supermini 110 from 9 mm (0.354"). For slot broaching operations, the disadvantage of the 110 system was the high tool cost. The need for a more economical solution for the diameter range 9 mm (0.354") to 14 mm (0.551") was thus clearly defined and formed the basis for a new development project at HORN. The aim of the project was to strategically extend the 117 grooving programme downwards to cover the diameter range 9 mm (0.354") to 14 mm (0.551"). The focus was on a solution that could be integrated into existing processes, works reliably and at the same time reduces the cost per component. Instead of a customised solution, a standardised tool system was to be developed that would offer users an alternative to the existing System 110. Harnessing the familiar System 117 meant that production, handling and use would remain as simple as possible.
The project work was spread across several specialist departments. Product management took on the role of project initiator and coordinator. The design department carried out fundamental research and feasibility studies. Based on this, new tool holders and matching inserts were developed. At the same time, Research and Development analysed the stability of the holders using FEM calculations. The results were incorporated directly into the design and formed the basis for safe machining of small diameters.
Production and automation specialists were also involved in the project at an early stage. The team focused on the safe handling of the small inserts, the design of the clamping screw and its defined tightening torque. The constant torque on the screw ensures even, precise insertion into the insert seat, but must not be too high due to the fragility and small size of the screw. Another team was responsible for automating the grinding processes to ensure reproducible quality. The holders were manufactured in-house. The close cooperation between all those involved resulted in the extended application range of the 117 slot broaching system.
Field trials
After development, production planning and manufacture of the prototypes, the first trials are on the agenda. Every newly developed tool has to prove itself at this stage of development in the HORN test centre. Does it function as planned or does it require a design adjustment? This question is at the heart of every test. If they are successful, HORN specialists task the field sales engineers to find customers who will test the tools in real-world production environments. One such user was the company Öschger. "The endoscope component was an obvious choice," says Clemens Fürderer, head of the turning technology team at Öschger. The component, made from 1.4307 stainless steel, has an internal diameter of 13 mm (0.512"). The internal keyway is 2 mm (0.079") wide and 10 mm long (0.394"), with two defined 45-degree chamfers.
Before the tests with the new tool system, the team produced the keyway with two type 110 inserts, one of which slotted the groove and the other broached the edge chamfers. HORN then supplied a special insert for the field trial, whereby the groove is cut and the edges chamfered with the same insert in one process. Broaching takes place via reciprocating stroke movements of the tool turret. A separate broaching unit is not economically viable due to the relatively small batch sizes.
Successful deployment
"After the first batch of components, the performance of the new tools was already apparent," says Fürderer, who continues: "We have already cut 2,500 keyways with the tool. There are still no signs of wear on the insert edge. It will probably last for another 2,500 machining operations." The tool previously used had a service life of just under 1,000 keyways. Major advantages of the new system are, firstly, the stability of the holder system and, secondly, the internal coolant supply directly to the cutting zone. "Besides the very good performance, the new tool also offers us considerable cost savings," says Fürderer. One of the reasons for these savings is that a significantly lower proportion of carbide is used in the insert.
With the expansion of the 117 slot broaching system, HORN offers a practical solution for small-diameter applications where process reliability and cost-effectiveness are equally important. The results from the field trials show that the system can be reliably integrated into existing production processes and enables stable broaching. Improved tool life, reduced tool costs and the combination of several machining steps in one tool have a positive impact on component costs.
Öschger GmbH
The company Öschger from Emmendingen is a specialist contract manufacturer of demanding medical components (ISO 13485), as well as CNC precision parts for other industries. Together with Oesterle+Partner, Öschger also specialises in the manufacture of driven tools for CNC lathes. The company manufactures complex components to high dimensional accuracy and consistent quality – from individual parts to series production. State-of-the-art CNC machines, precise measuring and testing technology and clearly structured processes ensure reliable results, even with the tight tolerances. Öschger partners with its customers from the initial technical consultation through production to on-time delivery. Technical expertise, process reliability and a strong commitment to quality make the company a high-performance partner for precision contract manufacturing.