In the medical industry, metal parts play an integral role in a vast array of diagnostic, testing, medical instruments, and equipment. Although certain complex metal parts can only be machined, thinner gauge parts and enclosures are typically stamped using hard tooling or fabricated using lasers, turret presses, or press brakes. These parts include carts, cabinets, enclosures, and user workstations that safeguard sensitive controls, electronics, or hardware. While not as high tech as the diagnostic equipment itself, these structural components are still critical to the product's function and longevity.
In addition, medical instruments and surgical tools are often comprised of metal parts that must be stamped to meet stringent tolerances. For example, in a surgical stapler used to close incisions, stamping ensures a tight fit for mating parts. Given the critical nature of these types of medical tools, it is also important that backup or replacement parts hold the same tolerances as well.
To meet these requirements, medical device OEMs sometimes turn to contract metal fabricators and stampers for assistance to reduce the price-per-part. This typically requires a careful evaluation of production volume requirements as well as critical decisions about the type of tooling used. In some cases, completely finished, assembled products can be outsourced, allowing OEMs to focus on critical design aspects of the technology and less on manufacturing.
The Tooling Dilemma
One challenge for manufacturers that outsource metal parts is in estimating the initial production requirements for new products. As a consequence, forecasts are often conservative or the complete opposite — unrealistically high.
With this inevitable uncertainty, OEMs are hesitant to invest significant dollars in hard tooling, which can cost tens of thousands of dollars at the outset. Instead, less-expensive soft tooling options may be selected initially, even if it increases the price-per-part.
However, as production demands increase, soft tooling options quickly slow production. At the appropriate tipping point in demand, medical equipment and instrument manufacturers ideally should transition to hybrid tooling, staged tooling, and even progressive dies that speed turnaround time and drive down the price.
This laddering up of the range of tooling options requires assessing at each plateau whether or not greater up-front investment in tooling will pay off with a relatively quick return on investment (ROI). Because tooling plays such a key role in this equation, it also requires evaluation of the best available tooling options at any given time.
Tool selection for the medical industry involves factors such as part size, metal thickness, complexity, and finish, and the cost per part is often related to the type of tooling utilized. This progression generally ranges from soft to hard tooling, including hybrid approaches, staged tooling, and fully progressive dies.
Low-volume part manufacturing for the medical industry often involves soft tooling for sheet metal fabrication. Soft tooling usually entails having a flat or slightly formed part that has holes, slots, or tabs punched in it by a CNC laser or turret punch press, followed by bending using a press brake.
Soft tooling typically ranges from $75 to $500, but can cost up to $3,000 for more complex parts. This can work for medical part prototyping and low-volume production orders. However, it can take several minutes of machine time to make each part, depending on its complexity, and thus the cost per part is higher.
One strategy for medical equipment manufacturers to lower or even eliminate soft-tooling costs is to borrow the tooling from a supplier's library of tools. DureX, for example, has built up an inventory of soft tools in many sizes and shapes because it has been serving a variety of markets for over 30 years. When appropriate, these tools can be put back in service. If that is the case, there is no charge for the item.
When critical tolerances are required and/or volumes increase to 15,000 units or more annually, OEMs often benefit from moving from soft tooling to hard tooling to reduce costs. The cost of hard tooling can vary from $5,000 to $300,000 depending on size, complexity, and whether the tooling is designed to produce a finished part.
One OEM, for example, started at 500 parts per month with soft tooling. However, when production requirements increased to 4,000 parts a month, it was suggested that they move to hard tooling to reduce the price from $22 to $15 a part. With a hard tooling cost of about $85,000, they achieved ROI in about four months.
As the name implies, hybrid tooling is a combination of soft and hard tooling. Depending on the part, it might begin as a flat piece of metal that is punched or formed with a soft tool, with further forming by a hard tool.
For example, an enclosure could be started in a turret that punches all the holes and slots before it is moved to a hard die that forms up the sides into a box — in a single operation. Instead of putting a flat piece of metal in a brake and hitting it four times to bend the two sides and two ends, a die could be used and it could be hit once. So, it takes 30 seconds or less to make the entire part instead of 2 minutes.
To create metal parts for medical equipment at even greater speed and volume as well as lower price per part, staged tooling can be used. With this process, a metal part is moved between multiple stage tools, so the work is performed in unlimited processes that utilize hard tooling.
For example, instead of taking five minutes in a machine to punch all the features individually using a soft tool, the contract manufacturer could make a blanking die and punch everything in one hit in seconds. It would then be put into a forming die and formed into shape.
The fastest, highest-volume part production can be achieved by using a progressive die. This accomplishes multiple operations in a single process using hard tooling. Depending on the part, a progressive die utilizes metal coil and can often produce a finished part with every machine cycle.
For example, one OEM was spending about $125 for a metal card cage that held circuit boards. When volume rose to 1,000 parts a week, the cost was reduced to $55 per cage by switching to multiple staged tools. Although the hard tooling cost was substantial — about $350,000 — the OEM achieved ROI in only five to six weeks.
Finally, medical equipment manufacturers may benefit from working with a contract manufacturer with additional services such as finishing and assembly to further streamline the process.
The ability for a contract manufacturer to take a medical part from cradle-to-grave from design through prototype, into full production of a fully assembled, finished product — even including fulfillment — can further reduce costs and allow the OEM to focus more on core competencies.
Whatever the scope of manufacturing, medical equipment manufacturers can benefit by working closely with metal part fabricators to optimize the tooling for the job. In doing so, they can significantly reduce per-part costs with a surprisingly fast ROI.
This article was written by Bob Denholtz, President of DureX Inc., Union, NJ. For more information, click here.