CAM saves toolmaking & prototyping costs

Although medical device manufacturing is a growing sector, companies are subject to enormous time and cost pressures. With its surgical division Aesculap, B. Braun is one of the most important manufacturers of surgical instruments, implants, and extensive accessories. Aesculap has a high-performance prototyping department which meets these challenges early in product development by performing initial testing and trials. The versatile toolmaking shop, located at the main plant in Tuttlingen, Germany also ensures optimized unit costs. Progressive dies, injection molding and forging tools, deep-drawing dies, clamping devices, and custom machining tools are produced here.

Aesculap Toolmaking Manager Hans Keller has been responsible for both areas for many years: “Whether it’s machines, tools, or software – we keep a close eye on how the market is developing, and we invest when we feel we can make improvements to our process flows, quality, and cost-effectiveness. As a result, we are very advanced when it comes to prototyping and toolmaking in terms of all the equipment we have.”

Prototyping’s pioneering role

One of the people responsible in the prototyping team is CAM Specialist Frank Fedtke. With 40 years of tenure, he’s a pioneer in CAM programming at Aesculap. “In the beginning, milling – and therefore CAM programming – was limited to machines with three linear axes. When machines with an additional rotary axis came along, we were still able to meet the requirements with the programming software we had at the time.” When machining centers for 5-axis cutting entered the market, they seemed highly appealing and suitable for manufacturing the complex, partly free-form Aesculap prototypes, “However, with our software, we were initially unable to create suitable NC programs ourselves,” Fedtke says. “We had to hire external partners to do this. Even when our CAM system at the time offered the first 5-axis strategies, the calculations took many hours, and the results were uncertain. From an economic point of view, this meant we were unable to compete with our external partners.”

After several years comparing different 5-axis programming software, in 2013 Fedtke tested the hyperMILL CAM system from OPEN MIND Technologies for prototyping. “To me, this CAD/CAM system seemed ideal for us to use in prototyping where we must produce a range of different components, because hyperMILL provided various tilt strategies which let us generate suitable milling paths for each geometry and each of our machines. In addition, as we didn’t have much experience in 5-axis programming, the clear and intuitive user interface suited us very well.”

The trial was followed by the purchase of two licenses, and after only one year, the investment had paid for itself, and further licenses followed. The scope of machining strategies offered by OPEN MIND continues to increase, so today all requirements are covered. “We initially produce almost every new job as a single part or small batch,” Fedtke explains. “These include surgical elements, as well as housing, motors, and other components for our power systems, that are our electrically powered tools.” Prototyping is also responsible for special implants (knees, hip, spine). These are typically 3D printed and then machined.

Diverse 5-axis strategies

According to Fedtke, 5-Axis Equidistant Finishing, which allows steep and flat areas to be machined in a single operation, is one hyperMILL strategy most used in prototyping. The result is smooth and jerk-free transitions between the individual toolpaths, creating the best possible surfaces. This shortens rework times, which is particularly important for implants as they have very high finish requirements. For example, a quality of Ra = 0.05µm is prescribed for the surface finish of a knee prosthesis.

The prototype builders also like to use the Tangential Finishing strategy from the hyperMILL MAXX Machining package for machining custom knee implants. “By using a conical barrel cutter, we save ourselves time and also achieve the required parallelism of the inner surfaces of the femoral component much more easily,” Fedtke explains.

Field of application: toolmaking

After the initial experience gained in prototyping, toolmaking also switched over to hyperMILL and, “We’re able to achieve remarkable savings in programming, as well as in calculation times and ultimately in machining,” Fedtke notes.

An example of this is the deep-drawing tools for so-called sterile containers. These are boxes in which both the implant and all the tools needed for surgery are delivered in a sterile condition.

“In the past, programming 5-axis simultaneous milling paths in deep cavities presented us with considerable problems, especially due to the high surface quality we needed. The calculation times were more than 12 hours, and we were always on edge about whether the calculation would run through without aborting. With hyperMILL, it now takes 8-1/2 hours for a process-reliable NC program.”

Prioritizing automated production

Aesculap Toolmaking recently adopted hyperMILL AUTOMATION Center to standardize and automate complex process workflows. It’s based on feature and macro technology, but its automation options and capabilities go far beyond.

Automated programming was needed because Aesculap provides approximately 200 different standard hip prostheses differing mainly in size and geometric details. Manufacturing the prostheses requires many forging dies: one upper and one lower die each for the right and left hip (for a pre- and finishing die as well as for repressing).

Until recently, these were manufactured on a 5-axis machining center with a dual shuttle table. To take advantage of night and weekend shifts with fewer operators, an automated, 6-pallet loading and unloading system was added to the machine. They also selected new tools for more efficient machining, so 1,800 milling programs had to be rewritten – each program would have taken 2 hours to write manually, resulting in a total programming effort of 3,600 hours.

The toolmakers knew this programming must be done faster and contacted the CAM specialists at OPEN MIND for a joint project reprogramming the forging dies.

Michael Greisinger, automation and application specialist at OPEN MIND, led the project. “The hyperMILL AUTOMATION Center Advanced is based on our hyperMILL CAM system and the associated hyperCAD-S CAD software. It offers technology reaching far beyond the automation of standard geometry features. The specific characteristics of the CAD models are only of secondary importance in this context. The focus is on the elements a CAD model can contain. Experienced hyperMILL users can define the individual process steps using a wide range of template functions. This even makes it possible to define and standardize complex processes.”

Greisinger’s recommendation was that “automating the programming process is always worthwhile when families of parts need to be machined. In principle, it should be possible to program several similar components that differ in size, and the number and shape of the surfaces, holes, threads, and so on, to be machined,”

In the hyperMILL AUTOMATION Center Advanced, users can specify which operation they want to use for a particular geometry – such as Equidistant Finishing or another strategy – even how stock is positioned and clamped.

“Our automation environment can access and customize all hyperCAD-S commands and hyperMILL CAM commands. Basically, you can use it to automate anything that can be clicked,” Greisinger says.

2 hours to 12 minutes

Aesculap Application Engineer Thilo Hagen was involved in the project and the result completely convinced him, “The hyperMILL AUTOMATION Center has allowed us to reduce our programming time to 12 minutes. I attended a 3-day on-site workshop and learned how to use the AUTOMATION Center on my own projects. After that, I was immediately able to use the scripts I had developed and the outcome was excellent. The entire workflow is stored and can be applied to future components. From loading the STEP file all the way to the finished NC program, everything runs fully automatically in a matter of seconds.”

After purchasing the software last year Hagen has used the automation tool for seven projects of varying scope. “These include, for example, less complex components such as waterjet fixtures or milling jaws for reworking hip prostheses. The latest project – programming shaft covers – is already more demanding. In return, you end up saving more time.”

OPEN MIND Technologies
www.openmind-tech.com

Aesculap AG
www.aesculap.de