Device Manufacture Gets Up to Speed

16 September 2007 (Last Updated September 16th, 2007 18:30)

The demand for complex and sophisticated medical devices is escalating. Manufacturers therefore need to find the best way to provide custom-made appliances and rapid tooling can help.

Device Manufacture Gets Up to Speed

Custom manufacturing is taking on a more prominent role in today's manufacturing environment. It has become the complete package for low-volume production. The niche for low-volume production is increasing due to higher levels of product development, more frequent product revisions, segmented markets and the growth of higher margin/low-volume products commonly found in industries such as medical devices.

The demand to make revisions to currently available products seems to be at an all-time high. Changes can stem from attempts to improve functionality, make products more aesthetically pleasing or more cost effective. Seemingly, the release of a new product only sets the clock for the next revision or improvement. Product lifespan has been reduced, in part due to better, more cost-effective means of replacement.

The standards for medical devices in short-run custom manufacturing are still the same as those in high-volume production, but the targeted market is insufficient to support an investment in production tooling. These products still need to be quick to market, cost effective, thoroughly tested, qualified, packaged and be put through clinical trials.

A growing trend to help ease the pressures of custom manufacturing has been the evolution of rapid tooling for injection moulding. Rapid tooling typically consists of making an aluminium injection mould, a process that can be accomplished in two to three weeks as opposed to the four to six weeks common for hardened steel tools. Parts manufactured from engineering grade resins such as ABS, PC, Ultem® or Delrin® can then be made for a functional part for testing and clinical trials, or
be used as true production parts.

"Rapid tooling typically consists of making an aluminium injection mould, a process that can be accomplished in two to three weeks."

These moulds can be designed and constructed to capture complex geometry and undercuts using hand pickouts and manual slides. They are typically milled using high-speed CNC milling equipment, tipping tool speeds of greater than 40,000rpm.

A 7075- T6 grade aluminium is often used, allowing more effective heat transfer and minimising or eliminating the need for cooling lines in the cavity block of the mould. In some cases, these aluminium moulds have produced in excess of 50,000 parts, depending on the part requirements, resin material and complexity of the part design.

RAPID TOOLING IN ACTION

Restore Medical has used rapid tooling in two ways. One method was for R&D testing: the company was able to complete functional testing to evaluate an overmoulded sub-component, including the testing of several resins, effects of sterilisation/radiation exposure, accelerated ageing and early stage (moulding parameter) process mapping.

Once Restore Medical had compiled all of the test results, it was able to make educated part design, resin selection and tooling design decisions. This led to investment in production tooling, without fear of making expensive revisions to a complex tool.

The second use of rapid tooling was as a bridge to product extinction. In one instance, Restore Medical was phasing a product out of the market and used a rapid tool to accommodate that process. In excess of 11,000 parts were produced from the aluminium before the product elimination was complete.

Both of these rapid tools were produced by Vista Technologies. "The financial and time savings were huge," says Kurt Krueger, R&D manager of product development at Restore Medical. He sees tools being produced in six to eight weeks, with an occasional mould taking five weeks.

"This is definitely faster than in the early to mid-1990s when 12–18 week delivery times were not unheard of,’ he says, ‘but still cannot compete with aluminium tools that have a two to three
week-delivery when using high-speed milling."

Krueger also disclosed some less obvious benefits that were seen from making a rapid tool before launching into production. Not only could the tools complete many functional tests, they could also evaluate gating, venting, mould flow and the general processability of various materials. Krueger feels he can save approximately 30% with the knowledge gained through investing in a rapid tool prior to production. Savings can be greater on more complex parts.

MANUFACTURING PROCESSES

Vista Technologies has been making rapid tools for injection moulding since 2001. They have high-speed milling capabilities topping out at 42,000rpm. With in-house injection moulding introduced in spring of 2007, they have become a full-service rapid prototyping and rapid tooling service bureau.

Jim Mishek, founder and president of Vista Technologies, says, "The trends we have been able to identify are remarkable. For every ten moulds we produce, six get modified as a result of part redesign. It shows that some changes and tweaks can only be identified once the material and design are fully tested."

The time and cost of modifying a rapid tool is considerably faster and cheaper than modifying a hardened production mould, demonstrating the economics of investing time and effort into using rapid tooling for parts destined for long-term production.

"We are also surprised by the frequency of reorders that occur on these tools," says Mishek. "Many of our customers are using these tools for low-volume production or as a bridge tool until their final production tools are completely qualified. The latest trend we have observed is a dramatic shift from room temperature vulcanisation (RTV) moulding to rapid tooling spec-resin moulding."

RTV moulding is a prototyping process that yields approximately 20 parts per mould in a spec-like material and is traditionally used for early stage testing. Customers generally want fully functional parts, manufactured with the actual resin. In most cases, the investment breakeven point for manufacturing a rapid tool and producing parts compared to an RTV mould is approximately 50 parts.

"RTV moulding's primary advantage is the minimal time taken to produce the mould but the main concern is the time it takes to produce parts."

The savings become even more apparent when part reorders are taken into consideration. RTV moulding's primary advantage is the minimal time taken to produce the mould; but the main concern is the time it takes to produce parts. Demoulding time from an RTV mould can range from getting one to three parts a day.

These observations are echoed by Tom Spaulding, mechanical design engineer at Starkey Laboratories, Inc. By using rapid tooling technologies, the company is now producing prototype moulds in two to five weeks, rather than the 12–16 weeks of the past. "These moulds have been so useful," says Spaulding.

"They prove out the design that 80–90% of the time requires mould modifications, then when proven they function as bridge tooling or in short-run applications as the production tool. This shift allows the new product to be tested more quickly and then make it to market months faster."

Starkey has also seen another complete revolution in hearing aid manufacturing. Five years ago custom hearing aids were all handmade devices, now 99% of this product line is made using stereolithography, a rapid prototyping technology. According to Spaulding, "the evolution of new stereolithography materials now allows for the cost-effective manufacturing of custom hearing aids.

"The new materials allow for different colours to match the patient's skin tone and to denote right and left devices. This technology has been accepted so quickly that all custom hearing aid manufacturers are now using it."

This technology has performed so well in custom hearing aids that the company believes that the next manufacturing advancement may be using this rapid manufacturing technology for their other lines of hearing aid products.

THE FUTURE OF MANUFACTURING

The Wohler's Report, produced by Wohler Associates, Inc., noted this emergence of rapid manufacturing in the hearing aid business, prosthetics industry and in dental implants. As stated in the report, 13.6% of additive RP products are used in the medical and dental fields.

Rapid manufacturing (RM) is the direct production of finished goods from additive fabrication. The technique uses additive processes to deliver finished parts directly from digital data, eliminating all tooling. In conventional manufacturing, tooling is needed to produce parts and is one of the most restrictive factors for product developers.

The need for tooling is eliminated with the use of rapid manufacturing, along with the constraints of design-for-manufacture. One of the most significant elements of RM is freedom of design – it may involve custom parts, replacement parts, short-run production or series production. Parts with complex shapes and features are delivered in less time at a lower overall manufacturing cost.

With the elimination of tooling, there is no longer any need to produce thousands of parts to justify its cost. Cost-effective custom manufacturing is therefore becoming an attractive option. When a single part can be easily produced, it creates greater sales opportunities and a higher level of customer satisfaction.

Many see rapid manufacturing as a great opportunity for the future, but implementation may take time. However, as the market for custom manufacturing continues to increase, it seems likely that rapid tooling will become the manufacturing option of choice when it comes to producing medical devices.