HSC milling for high-volume production of surgical instruments

“The requirements are stringent, and the competition is hard in the manufacturing of precision mechanical surgical instruments,” says Frank Pauschert, regional sales manager of Schwäbische Werkzeugmaschinen GmbH (SW), Waldmössingen, Germany.

A challenging one-time product

The manufacturer has not previously produced any of its own products, limiting profitability and future growth. To safeguard for the long-term, the company decided to enter an extremely challenging large-scale production project – manufacturing one-time-use forceps for neurosurgery with hundreds of thousands of units needed annually. The forceps are made of aluminum so they can grasp tissue components while simultaneously preventing minor bleeding with electrical pulses. Minute tubes integrated into each arm of the forceps direct irrigation fluid into the operating area. Despite its straightforward appearance, the instrument’s manufacture involves multiple mechanical and manual work cycles under strict quality standards. Setting up the process chain requires extensive development efforts as well as substantial investment in machines and special equipment.

High efficiency machining center

The starting point and key element of the process chain is an automated dual-spindle BA 321 machining center from SW (see sidebar), which mills the aluminum forceps halves. A custom-made automation unit supplies material and removes milled parts. Although it’s only intended for a limited range of parts, it’s more productive than other milling centers in the plant within that range.

With its horizontal, dual-spindle design, the new machining center delivers two completely milled forceps halves in just 3 minutes. Equipped with an automation system, it can produce forceps around the clock, largely without supervision.

Joint development of automation

SW was chosen primarily because of the productivity of the machine’s double-spindle concept, its trusted reputation, and proximity to the plant.

Initial contacts led to a collaboration clarifying the possibilities for automating machining processes. This was followed by joint design and development of a special machine based on the BA 321 model. Special press-drawn sections in three different dimensions are used for raw material. The forceps halves are machined from the sections and aren’t separated by sawing until the last work cycle. This neatly sidesteps clamping problems that accompany the extremely slender and delicate forceps halves.

The final cut from the saw is made so that a minimal amount of burr remains to prevent the pieces from falling and damaging the forceps’ delicate tips. Eventually, the forceps are removed by special adapters loaded into the spindles from the tool magazine. They hold the forceps parts, breaking off remaining burrs. They are then individually deposited on a transport drawer and moved via conveyor belt to the removal station, where they are manually inserted in basket racks for the next work cycles.

“The joint development of automation was very efficient thanks to the professionalism of both teams,” Pauschert says.

Delivery and commissioning

Joint development, project planning, setup, and trials prior to acceptance lasted about a year. Necessary tools were implemented during this phase and an initial NC program was created based on customer requirements. After acceptance, the system was placed in operation with tests and programming for 18 product variants. Once ramp-up began, production ran in 24/6 operation with the system sometimes running for up to a week with no human interaction other than supplying material and removing finished milled parts.

Satisfied with quality, support, service

Using SW’s Life StartUp production monitoring after commissioning allowed employees to quickly familiarize themselves with operating the machine. With SW’s online service, Life Data, the machine is continually connected to SW where essential machine parameters are monitored nonstop. If problems arise, immediate action is taken. When problems did occasionally occur, Life Data provided quick and competent consulting, and if a service employee was needed, he was often on site for less than an hour. An additional BA 321 has already been ordered and delivered.

Schwäbische Werkzeugmaschinen GmbH
SW North America
https://www.sw-machines.de/us.html