Minimally invasive surgeries force manufacturers to shrink parts

Whether producing consumables, implants or surgical tools, today’s medical device manufacturers face continuously shrinking part sizes, increasingly complex geometries, and tighter tolerance requirements than ever before – all within high-mix/low-volume (HMLV) production environments. The root cause of these production challenges is the growing trend toward minimally invasive surgical (MIS) procedures, together with implants and devices that continue to become increasingly patient specific.

Fortunately, the prognosis is good for medical manufacturers if they apply fully automated turnkey cells that combine multiple advanced process technologies such as high-speed milling, electrical discharge machining (EDM), and laser texturing. With this approach, medical manufacturers can cost-effectively maintain compliance with stringent ISO 13485 medical standards, easily generate complex part geometries, and keep pace in an HMLV production scenario. Such was the case for one medical parts manufacturer in the production of bone saw guides.

Matching parts to individuals

Made from vacuum-hardened 45HRc 17-4 stainless steel, bone saw guide blocks position saw blades during hip and knee replacement procedures and involve extremely complex curved surfaces and specified matte finishes, along with guide slots that must be smooth and precise. The real challenge is that the guides must match the shape of the individual patient’s bone.

To meet all part requirements and tight turnaround times, the manufacturer incorporated 5-axis milling, wire EDM, and laser texturing into one fully automated cell supplied by single-source original equipment manufacturer (OEM) GF Machining Solutions. It also included advanced software and robot and pallet systems.

The software, WorkShopManager (WSM) from GF Machining Solutions’ System 3R, functions as a digital command center distributing production orders and managing parts and data while identifying each pallet through integrated radio frequency identification (RFID) chips. Working in tandem with the software, the pallet and zero-point chucks allow the manufacturer to accurately position workpieces in different machining systems.

The part process begins with raw material mounted on pallets. Next, a coordinate measuring machine (CMM) measures offsets, which are assigned to the pallet ID and transferred to a Structured Query Language (SQL) database within WorkShopManager. Other data, such as raw material references and operator ID, can also be stored within the same database.

Pallets allow the manufacturer to automatically load/unload in seconds using a robot for positioning repeatability within microns. Automating the data exchange directly with the manufacturing cell controller also prevents selecting the wrong computer aided manufacturing (CAM) file or incorrectly reading or writing data.

High-speed milling, EDMing

Once pallets are loaded, they move to a Mikron MILL X 400 U high-speed milling machine for 5-axis milling to generate the shape and most of the features on the guide blocks. The machine features direct drives on all five axes, a 42,000rpm Step-Tec spindle, and a table with 220º of swivel.

Milling cycles are 46 minutes, and the machine generates surface roughness  <Ra 0.7μm. This high-quality surface partially stems from the range of table swivel, which provides ample access to the part, allowing the manufacturer to use shorter cutting tools, reducing vibration and increasing tool life.

The MILL X 400 U also integrates Automatic Machine Calibration (AMC) hardware and software, enabling the system to maintain accuracy even in challenging conditions. With AMC, calibration takes only a few minutes and is possible at any time – without the need for specialized personnel.

To machine the highly critical slots that guide bone saw blades during surgery, the manufacturer uses a GF Machining Solutions AgieCharmilles CUT P 550 wire EDM, to make the angled cuts at both edges of the slots that help when surgeons insert the saw blade. This is a highly challenging operation because the curved features of the guide block alter the amount of material being removed during the cut. To compensate, the machine’s Intelligent Spark Protection System automatically analyzes spark position and spark intensity in real time and makes necessary adjustments for complete control of cut quality.

The CUT P 550 uses a Quadrax system design where its table and workpiece remain stationary and stable while axis movement displaces the wire, allowing for straight and angled cuts. This design, together with the machine’s low thermal conductivity and vibration dampening, provides greater dimensional accuracy and improves overall system repeatability. With ±45º angling capability, the machine eliminates multiple setups to save time and effort.

Laser texturing

Bone saw blade guide block surfaces must be non-reflective to prevent glare while in use. To produce this matte finish and mark parts with hidden logos and other critical data, the manufacturer opted for a GF Machining Solutions Laser P 400 U 5-axis laser texturing system that performs both operations in a single setup.

Additionally, the laser system eliminates the need for masking or other manual operations, such as grit blasting, to achieve required surface finishes. Because it’s digital, the laser system is much more repeatable, cleaner, and faster than grit blasting, reducing waste and the risk of human error.

Turnkey

For today’s medical manufacturers, fully automated turnkey cells that include milling, wire EDM, and laser texturing technologies ensure much needed part quality, efficiency, and 24/7 production capability. Truly advanced cells also allow for complete system monitoring, as with rConnect software and hardware from GF Machining Solutions, which provides all the benefits of digital connectivity and Industry 4.0 to optimize operations.

GF Machining Solutions: https://www.gfms.com