The process chain for a typical implant begins in the clinic, where the doctor uses CT scan imaging data to select an appropriate implant.
NX CAM programming from Siemens PLM enables realistic simulation of machine tool functions.
Implants for knee joints are precision machined with the HSC process on a machine tool run by Siemens SINUMERIK 840D solution line CNC technology.
The finished implant is a perfect fit.
The production of today's medical implants involves an entire process chain, starting with the doctor and ending with the finished device. Doctors use the imaging data of a complex fracture, acquired with a computed tomography (CT) scan, to select an appropriate implant and then position it in the fracture area of the patient on the computer. Of course, this is only possible if the implant geometries are stored in a database and the doctor has implants in stock or can access them immediately from a manufacturer.
In plastic surgery, however, where implants specifically manufactured for each individual patient are needed, a different process is employed. Instead of pre-machined parts, implants are custom-made with the help of 3D imaging. In this case, the machine tools are controlled using the implant geometries. Calculated contours and shapes are acquired by the CT scan to produce implants that are literally a perfect fit. However, the feasibility of the planned production process must first be determined on a monitor using, for example, an NX graphic simulation from Siemens to avoid potential collisions or damage to the workpiece contours.
High-speed cutting (HSC) is a machining process with high material processing speeds. HSC machine tools achieve high spindle speeds, combined with feed rates that are much higher than those of conventional machine tools. Consequently, they require control systems and part programs that perform equally fast. The Siemens Sinumerik 840D solution line CNC is specifically designed for the requirements of medical technology and this precision part HSC work. Integrated functions onboard the CNC assist users with set-up and programming, thus allowing faster and more precise production sequences, the company said.
"Together, the Sinumerik CNC system and ShopMill software from Siemens form a milling technology package that allows machine operators rapid access to the functions they need," said a Siemens spokesperson. "Thanks to graphic function display and plain language input dialogs, cycles can be used quickly and effectively, after a brief training period. Even the smallest errors can be corrected during operation, using multi-axis kinematic analysis. The Siemens Safety Integrated solution further provides protection for personnel and machinery. This software can be used to interlink emergency stop buttons and light barriers. In the event of an operating error, dangerous movements are immediately brought to a standstill and the power supply to the motor is quickly cut."
The production of artificial knee joints on an HSC 20 linear milling center manufactured by DMG, for example, can be fully controlled and monitored by a Siemens Sinumerik CNC system. "With its broad range of functions, this milling center is particularly well-suited for use in the medical technology sector," said the spokesperson. "It is equipped with linear drives on all axes and achieves acceleration rates over 2 g. The machine can also generate a surface finish down to 0.2 micrometers Ra. The liquid-cooled machining spindle operates at speeds up to 42,000 RPM, thereby covering an extensive range of potential applications in the medical sector, where materials such as titanium, chromium-molybdenum, tantalum and niobium are typically milled.
"In order to achieve maximum precision during implant production while also maintaining a consistently high level of product quality, parametric measurements must be taken continuously from both the machine and the workpiece. Renishaw probes, for example, on HSC production machines measure tool dimensions in-process, detect broken tools and are used for the set-up and measurement of workpieces. In medical machine shops currently, the targeted use of such measuring probes can reduce set-up times by up to 90%, while substantially improving process control.
"Metal parts used in medical technology are often extremely complex. Therefore, choosing the right tooling can have a great impact on the quality of the finished products. After all, proper cutting tools ensure that the parts leaving the machining center are absolutely precise and require no further finishing work. Although the materials used for many medical and orthopedic parts are often quite difficult to machine, the tools must fulfill high performance requirements with respect to the precision and surface quality of these implants. Iscar, one supplier of such tools, offers a program for monitoring the use of precision tools on turning, drilling, milling and finishing jobs. They also help users assess the performance qualities of non-vibrating carbide milling cutters, which are well-suited for machining implant materials, plus they can offer information on more cost-effective and efficient machining processes."
For more information contact:
Siemens Industry, Inc.
Drive Technologies - Motion Control
Machine Tool Business
390 Kent Avenue
Elk Grove Village, IL 60007