Connecticut Spring & Stamping (CSS), a manufacturer of precision parts for the medical, aerospace, firearms...
The pace of product launch in the medical device industry continues to pick up, responding to the speed at which information is exchanged and the perceived need to introduce the latest product revision to beat competitors. Original equipment manufacturers are pushing the envelope to get from concept to production in the fastest possible time.
To meet OEMs’ need for this fast pace in the world of metal stamped parts and springs, engineering expertise is taking on an ever-more important role. Expertise in prototyping parts to test and prove design concepts, suggesting ways to reduce secondary operations to reduce cost, and providing value engineering consulting expertise, are key engineering skills that ensure the success of projects. Behind it all is a foundation of communications and two-way dialogue that ensures that products meet customer requirements.
Starting off on the right foot – initial customer contact
The devil is in the details, so they say, and that’s what makes the initial customer contact phase so important. No matter what the industry, or the schedule requirements, each project should begin by establishing lines of communication to get an in-depth understanding of a customer’s design, objectives, and material requirements. A discussion of part dimension tolerance is essential. Some tight tolerances may add significant cost, and may not be critical, while others may be achievable at no additional cost. Understanding the key dimensions and the most critical part tolerances is extremely valuable to both parties when developing the final part print.
Familiarizing oneself with the product, including models and 3-D drawings, and following that up by talking to the customer to get a clear idea of what is needed and identifying critical characteristics are the next important steps. These steps are followed by internal discussions to develop recommended options for design, tooling and production.
This initial phase set the scene for a successful project for Aragon Surgical, a Palo Alto, CA-based startup medical device firm that significantly reduced its costs by converting a fully machined part to a stamped part with machined features.
Brandon Loudermilk, Aragon Surgical’s senior research and development engineer, explained that he was looking to reduce the overall cost of the firm’s previously released laparoscopic surgical device, and was given the task of finding ways to decrease costs on as many parts as possible. The jaw housing was one of the higher priced parts, making it a good candidate for alternatives. In addition, there were problems getting sufficient parts from the existing supplier.
At the initial contact with Aragon Surgical, engineers at Connecticut Spring & Stamping (CSS) began the process by looking at the part and discussing ways it might be stamped instead of machined from a solid tube.
“When we started I thought there was no way anyone could stamp this part to be perfectly round and make it function properly,” said Loudermilk. Engineers at CSS then hosted several conversations and went through numerous steps to arrive at the most important features on the part and figure out how it could be stamped within the necessary tolerances. Web-conferencing played a significant role, so the two groups could go back and forth quickly and remain on the same page. In just a few short weeks, they came to an agreement and were able to begin working on production tooling.
One interesting aspect of the early conversations was that CSS engineers showed Aragon another piece they make, a lock barrel for a high-end commercial door lock that was similar in many ways to the jaw housing. “When I saw how they could produce that part, how round it was and how good the finish was, it made me consider talking to them more about stamping this part.”
Once they started talking, CSS engineers went over the part print with a fine-toothed comb, adjusting the 3-dimensional CAD model and marking up the original drawing with their initial ideas. The groups discussed the tight dimensions, stepping through each feature to see if they could hold the tolerances, looking at the mating parts to see what the critical features were and how the mating parts interacted, discussing which features were critical and agreeing on which other features could be machined out, and how the part would have to be aligned. Many emails, redlined drawings, web meetings later, the agreement was made. And that was just the first phase.
The tooling costs were significant, but the high per part savings made the investment worth it. When the part was made as part of a tube, it was held to a tolerance of plus or minus 1/1000th of an inch. The stamped part is capable of plus or minus 2/1000th of an inch. Even though the tolerance is 1/1000th more, the part is fully functional in the design, at a significant saving.
The startup firm is conservative with its capital, and went through numerous discussions to arrive at an agreement, which included amortizing the tool costs used to stamp the part. “We paid up front for a certain quantity of parts, with the additional cost going towards paying for the tool costs. This enables us to get cheaper parts quickly, without putting out our capital up front. After the initial run was consumed, the tooling comes out of the piece price, making it that much more attractive and profitable.”
Loudermilk estimates that the initial run was 20%-30% cheaper; when the tooling costs come out the new stamped jaw housing is 50%-60% cheaper than the machined version, while still meeting all the design specifications.
Prototyping – if at first you don’t succeed, keep trying
One fact of life in the metal stamping and springs industry is that metal components are often the last to be sourced. Since plastic parts cannot be changed without significant mold costs and very long lead times, stamped metal parts and springs frequently need to adjust to other parts’ restrictions. This makes prototyping a very important part of the design development process.
Is raw material cost a main concern, or is tooling cost the biggest issue? Getting this information up front is essential to develop a prototype or series of prototypes to meet their needs. With a brand new product, enough detail is needed to work out the best material to make a prototype that can be manufactured in a production scenario.
Tony Morefield, director of manufacturing and engineering services for Sunnyvale, CA-based Avantis Medical Systems, used the prototyping phase to great advantage to develop a cost-effective spring for a catheter, which is fitted on the end to lock the part into the working channel of a scope. Avantis had experienced quality issues with its original supplier and was looking for a spring that would perform well in the instrument.
Spring tolerances were key; there were tight angles Avantis needed to be held for the spring to perform properly. As part of the research and development process for the part, CSS went through four revisions during which they tested slightly different angles and dimensions on the spring.
“Actually, it’s interesting, but at first I didn’t even realize we were prototyping,” says Morefield. “We received feedback from the original drawings that the engineers were not comfortable they could manufacture the part as designed. We revised the drawings live on conference calls and discussed the design to see where we had leeway as far as changing tolerances. This method was great for coming to an agreement quickly on what the next revision would look like.”
From CSS’s perspective the Avantis process was different than many because Avantis came in with a design whose tolerances and bend angles made it extremely difficult to manufacture. Engineers made a few suggestions on the bend angles that connect two coiled sections of the spring. Opening up some tolerances to make the part manufacturable and supplying a prototype to try it out worked well.
The result of the prototyping effort has been successful, says Morefield. “We have been through a lot of benchtop testing and have used the instrument on about 100 patients. We are now in the midst of a full commercial launch.”
Stamped metal and springs are used in millions of products across the gamut of industries. Experience on how metals move and where they are likely to fail goes a long way to reducing costs and developing solutions. In addition, experienced engineers can increase value and reduce costs by designing tooling with flexible options for change. This is frequently done by adding skip stations in a die for a nominal up front tool cost where additional cutting or forming can be added if needed.
Value engineering helps customer design parts that are within a tight tolerance and yet very manufacturable and consistent in the long run. It is most effective when the engineer has familiarity with a customer’s product range and can take what they’ve learned in the past and apply it to new products.
There are multiple options for developing a customer’s individual production tools, and time pressures may play a factor in which ones are appropriate.
Progressive die tools provide more consistent results, and allow a higher capacity. With a progressive tool, there is not as much variation, and the process is more stable.
Bridge tooling, a lower cost tooling option that can be used to produce a certain number of parts, is an interim measure that can be used while the full blown production tooling drawings are being designed and produced. It is most often used when the customer is not 100% certain the design is stable; about 10% of projects use this type of tooling, which can be used to test the final assembly in the real world. If the design works well, the tooling is finalized; if not, changes can be made more easily. Bridge tooling may also be used if production lead times or budgetary concerns do not allow for a full blown progressive die sets. Since bridge tooling involves multiple single-stand operations, it may lead to process variation.
Nearing the end of the line – running parts off a progressive tool
At this stage, the issue is quality and capacity. At CSS, the new tool group gets each new order, builds the tool, stamps out tooling samples and conducts the first production run. When customer approval is obtained, the new tool group hands the tool and the process off to the production floor after working out the details of the required quality inspection program.
Tooling plays a key role in the race to get products to market quickly. For example, the Aragon Surgical part requires a unique rotary head used on milling the portion of the part that gets machined after it is stamped. After the part is formed, it goes into the milling operation to finish mill certain surfaces that need a particular surface finish and accuracy.
Quality control and inspection
While the manufacturing steps are all taken with the aim of moving parts from concept to completion quickly, the last step, quality control, is never sacrificed for the sake of speed. Every job goes through a rigorous quality inspection process that includes the inspection frequency necessary, in accordance with customer-specific requirements, which may vary by industry and type of job. All jobs are checked prior to the start of production and receive in-process inspections and a final quality inspection.
Other steps may also be taken for ensuring quality, depending on the part. For example, Aragon Surgical parts, which are electro-polished and sent out for laser marking, are packed in trays to eliminate scratching during shipping.
From the initial customer contact and quotation phase, to prototyping, to value engineering, production tooling, running parts off progressive tooling, and quality control and inspection, the metal springs and stamping business has had to adapt to this rapid pace. Lessons learned by medical device manufacturers Aragon Surgical and Avantis Medical Systems show that each step plays an important role in moving a part from concept to completion at the blazing speeds now considered normal.
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