From image to implant

Medical implant production involves an entire process chain – starting with the doctor and ending with the finished device. Using a computed tomography (CT) scan of a complex fracture, doctors select an appropriate implant and position it in the fracture area of the patient on a computer. 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, individuals need specifically manufactured implants, so doctors employ a different process. Instead of pre-machined parts, manufacturers custom-make implants with the help of 3D imaging. The machine tools are controlled using the implant geometries, and calculated contours and shapes are acquired by the CT scan to produce implants that are a perfect fit. Feasibility of production can be determined on a monitor using an NX CAM graphic simulation from Siemens PLM 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 and feed rates compared to those of conventional machine tools. They require control systems and part programs that perform equally fast.

Siemens engineers designed the Sinumerik 840D solution line CNC for the requirements of medical technology and precision HSC work. Functions onboard the CNC assist users with set-up and programming, allowing faster and more precise production sequences.

The Sinumerik CNC system, coupled with ShopMill software from Siemens, forms a milling technology package that gives machine operators the functions they need. Graphic function display and plain language input dialogs allow cycles to be used effectively. Errors can be corrected during operation using a multi-axis kinematic analysis.

Siemens safety-integrated solution provides protection for personnel and machinery by interlinking 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 cut.
 

Measuring probes

The production of artificial knee joints on an HSC 20 linear milling center manufactured by DMG MORI, for example, can be controlled and monitored by a Siemens Sinumerik CNC system. The milling center is equipped with linear drives on all axes and achieves acceleration rates higher than 2G. The machine can also generate a 0.2µm Ra surface finish. The liquid-cooled machining spindle operates up to 42,000rpm, covering medical sector applications where materials such as titanium, chromium-molybdenum, tantalum, and niobium are milled.

For precision during implant production, parametric measurements are continuously taken from both the machine and the workpiece. Renishaw probes 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, the targeted use of measuring probes can reduce setup times by up to 90%, and improve process control.

Siemens Industry Inc.
www.usa.siemens.com/840D-sl