A major medical device manufacturer of innovative technologies was developing an endoscopy device used in minimally invasive surgeries. The design requirements for this new device specified a low cost articulating tube that could be controlled by guide wires during the surgery. The articulating tube also known as the A-joint would allow the surgeon to insert various instruments inside the tube while performing this procedure. After several years of development and costly design proposals, the customer decided to explore alternative materials and a more cost effective manufacturing method. They worked with OKAY Industries, Inc., a contract manufacturer of complex metal stamped components and sub-assemblies based in New Britain, CT, to develop the A-joint as a patent-pending stamped stainless steel link assembly with (28) springs to meet their cost/design goals.

OKAY partnered with its customer to understand the critical requirements of the application and developed methods for manufacturing a significantly lower cost stamped assembly in place of a competitive material. Additionally, the company’s R&D effort has uncovered several potential opportunities for this technology to benefit other customers who have applications for articulation joints in medical and non-medical applications. The two most significant benefits are the consistent quality & low cost.

The manufacture of the A-joint is very challenging because of the complex welding assembly process, the tolerances on key dimensions and target cost. The initial manufacturing method for the A-joint was to laser cut stainless steel tubing and weld springs to the individual links. For prototypes and low volume applications this method is very cost effective. However, for higher volume production requirements, in excess of 1MM units per year, a metal-stamped and welded assembly provides a more cost effective solution. In a patent-pending process the individual links are stamped and interconnected as a complete set to maintain their locations during the articulation joint welding assembly. After all of the inter-connected flat links have been joined together via laser-welded springs, the links are then separated and the assembled A-joint is then formed into the finished diameter. To reconnect the open ends of each link, a laser operation seam welds the last row of internal springs across each link from end to end.

OKAY used its Production Proven Prototyping® process to utilize the same tooling concepts, sequence of operations and grain direction that will be used in the production tool. Replicating the stamping manufacturing process during the prototype stage can minimize costly changes later in the project that would not have been identified using machining or other prototyping methods. Component strength, cracking, surface finish, burrs/edge condition and feature tolerance capability are a few of the concerns that were assessed. Prototyping can play a critical role in determining if the stamped solution will work for the customer’s application. The primary reason for prototyping is verification that the component or assembly will function as intended in its final application. However, for metal stampings, it is critical that you go beyond prototyping for fit, form and function and think ahead to manufacturing. Prototyping of metal stampings will allow you to determine if the stamping process is stable and capable, if cost expectations can be achieved and to identify opportunities for improvements in both cost and quality of the component or assembly.

1. The customer is receiving an extremely tight tolerance stamped assembly with (28) springs and high process capability at a significantly lower cost than a laser cut tube assembly.
2. With the automated laser welding operation and integration of the automated roll forming operation, the customer is insured every part will meet the print specifications without requiring secondary operations to perform these functions.
3. This research and development effort by OKAY has uncovered other opportunities for this technology to benefit customers in several industries who are looking to reduce cost by developing articulation joints as stamped solutions that were typically made using more costly manufacturing processes.

The utilization of metal stampings to produce the links in place of laser-cut tubing provided a tremendous cost savings for the customer. Additionally, the ability to weld the majority of the springs in place while the links are in the flat state proved to be very advantageous for tooling/welding fixture design and capital cost for the project.

One of the biggest challenges in stamping the (14) individual links for the A-joint was to develop a method for keeping the links in position prior to welding the (28) springs in place.

The final welding operation is the most critical operation in the process because OKAY had to combine welding the last row of internal springs and the tube seam at the same time.

OKAY provided the customer with the proper expertise and guidance to meet the challenge of stamping a unique Articulation Joint from the early prototype stage to final production tooling. Understanding the challenges and design guidelines of stamping a welded assembly can lead to a cost effective alternative to laser-cut tubing for many higher volume medical device applications. Metal stamping provides a capable and stable process for high volume, tight-tolerance components. Stamping is worth a look for OEMs looking for a more cost effective alternative manufacturing process for lower cost assembled products.