To ensure the optimal function of artificial hips in a patient’s body, certain surface areas on the hip stem must have different finishes — such as a very smooth, polished surface on the neck area of the stems.

A manufacturer of these precision components recently replaced a combined manual grinding/ electropolishing operation with an automated two-stage mass finishing process using an R 4/700 SF drag finisher from Rösler to precisely finish 12 hip stems in a single operation. This not only results in significant cost savings and lower cycle times but also in a ‘drastically improved quality and consistent finish’.

The main focus of MBN Präzisionstechnik GmbH, located in the Austrian town of Pottendorf, is the production of orthopaedic implants and surgical instruments made from titanium and stainless steel; and while production is to a large extent automated and allows traceability of the entire manufacturing chain — from the raw material to the finished product — until recently polishing of the neck area of the hip stems was by manual pre-grinding and fine-grinding steps, followed by an electropolishing process — operations that were time-consuming, required a lot of manpower and were very costly. In addition, it was less than perfect regarding consistency.

This situation prompted Thomas Müllner, MBN’s general manager, to look for an automated alternative: “Since only a precisely defined surface area must be polished, and a variety of different hip stem shafts must be processed, automating the surface finishing process turned out to be quite challenging. Our first processing trials were undertaken by a supplier that competes with Rösler, but the results did not meet our quality standards.”

Based on the recommendation of one of MBN’s customers, further processing trials were conducted by Rösler’s sales branch in Austria, which ran processing trials in a drag finisher — a mass finishing system that allows the precise and targeted surface finishing of high-value work pieces with complex shapes.

Mr Müllner added: “Rösler’s comprehensive know-how and experience from the trials helped to quickly develop a two-stage process with the drag finishing technology comprising a wet grinding/pre-polishing step, followed by a dry polishing stage. Combined, these produce a consistently high quality in surprisingly short cycle times.

“A major feature of the Rösler drag finishing technology is the vibratory motor mounted below the processing bowl. The resulting vibration of this bowl ensures the optimal mixing of the processing media, which results in the reliable homogeneous finishing of all relevant surface areas on the hip stems. Moreover, compared to our previous finishing operation, the cost for finishing has been reduced by two thirds.”