This technical information has been contributed by
Marshall Manufacturing

Medical Component Manufacturer Creates New Processes to Meet Customer Needs

Marshall Manufacturing uses proprietary CNC 2D and 3D bending processes to manufacture a variety of intricate, close-tolerance tube and wire components for the medical industry. Examples include introducers, needles, cannulas, implantable spine components, and orthopedic products.
Photo courtesy of Marshall Manufacturing

An example is a proprietary CNC 2D and 3D bending process that enables the company to create radical bend shapes not previously achievable through other processes

It can sometimes be surprising to learn how a manufacturing specialist got started in their area of expertise. Marshall Manufacturing, a Minneapolis-based precision machining company known for its CNC 2D and 3D bending capabilities for the medical industry, is a good example. The company, which traces its roots back to the 1950s, had built a reputation as a full service provider of precision machining services, including CNC Swiss machining, wire EDM, CNC turning and milling, and medical laser tube cutting. Then one day, about 15 years ago, a customer came to Marshall with a request that would turn out to have a big impact on the company's future operations.

"We were doing a medical part for a customer that came to us with a need for a complex, 3-dimensional bend," said Tom Plantenberg, Marshall's sales manager. "We went to a vendor that specializes in bending—that's all they do is bending—and they couldn't do it. That's when we said 'We have to do it ourselves.' From there, it grew rapidly, and now, 60 percent of our customers are in the medical industry."
Today, bending is a process that is frequently required in Marshall's work, which includes parts such as trocars, introducers, and spinal implants. Marshall has established a niche in providing complex, 2D and 3D bending of small diameter, pre-machined tube and wire—a specialty that the company says is a big differentiator from other contract manufacturing firms—for the medical industry. Marshall's CNC 2D and 3D bending processes are designed to help meet the rising demand for sophisticated surgical instruments that are necessary for minimally invasive surgical procedures.

"We have kind of a unique process for bending that a lot of other companies don't," said Mike Hedtke, project coordinator at Marshall Manufacturing. "Typically, you see a lot of the coil benders and spring manufacturers run off a long coil, bend it up, cut it off, and then try to do whatever else, machining wise, they want done on it. We've flipped that around a little bit."

 Marshall's process, Hedtke says, involves machining the part first. "We'll run the part complete, chop it off straight, and then bend it up as pieces. We can actually orient both ends of the feature in 3D space to however the customer wants it to be, and that's been very helpful in the medical industry for making surgical tools with handles on them, for example. Whereas, if you try to machine those tips afterwards, once it's bent, that's a whole lot more complicated—usually a milling operation instead of a turning operation."

Marshall Manufacturing ( employs an automated, CNC programmable bending system that incorporates 2- and 3-Dimensional precision bending of pre-machined, small diameter wire and tubing. The automated bending cell is capable of generating complex bends. Using CNC control is said to enable the company to reduce setup and cycle times and "create radical bend shapes that were previously unachievable."

"Customer requirements often dictate that a part feature, such as a machined flat or drilled cross hole, must orient to the bend," says a Marshall Manufacturing spokesman in a video explaining the automated bending process. "This is achieved by utilizing lasers and other sensing devices" (proximity sensor).

The video on Marshall's website goes on to explain the two types of bending modes: free form bending and rotary draw. "In free form bending, the product is pushed through two or more rollers that put pressure on the sides of the part in a right or left direction to produce the desired curves. In unison with the series of rollers, the part can be turned while going through the rollers in order to produce 3-dimensional helixes, curls, and other desired shapes. In rotary draw bending, the product is drawn around a second mandrel instead of being pushed through by the robotic arm. When needed, both free form bending and rotary draw capabilities can be used when processing a single part."

Because it is servo driven, the system is reported to provide extreme accuracy and is capable of forming tube diameters from 0.096 to 0.50 inch. Capacity for wire is said to range from 0.050 to 0.315 inch. Length capacity for wire and tubing ranges from 5.75 inches to approximately 60 inches, according to the company.

Hedtke says that Marshall has proven its ability to create—largely through software programming and tooling—new processes in order to best achieve a customer's goals for a particular part. Its CNC 2D and 3D bending processes are a case in point. "Even the company we purchased our equipment from couldn't do what we do," he said. "We have some custom tooling with regard to our bend processes, and we've proven that when another company can't do it for us, we can figure it out ourselves."

Marshall, which offers an extensive range of Swiss machining capabilities, can machine a variety of cross-holes, contours, slots, flats, and trocar tips into a wire component before the bending process. This is said to assure the integrity of the machined features and the bending process. Marshall can also use its CNC bending machine to process pre-cut cannulas, hollow needles, and tubes that require special laser cut windows, slots, contoured edges, and 4-axis cuts.
When a customer requires certain machined features of the part to be oriented to the bend features, Marshall uses its automated bending processes to provide quick design iterations. Through its use of advanced bending techniques, the company says that it can offer its medical customers multiple benefits, including cost savings, faster prototypes, improved production turnaround, and consistent quality.

Marshall's capabilities are said to provide medical designers with the freedom to design numerous features and configurations into contoured tubes and wire components.  The company can manufacture a range of needle tips for wire, including trocar points, taper points, and bullet points.

Often, medical device components that require bending have machined features on both ends of the wire or tube, as well as additional features along the length. Frequently, these components require specific features to be oriented to other features in three dimensional space. For example, a cross hole or slot on a bent tube may need to mate with a similar feature in another component. However, it may be cost prohibitive to add this feature after bending, as opposed to creating the feature prior to bending. According to Marshall, its CNC bending capability often allows stock to be completely machined prior to bending, so that features are oriented as the part is bent.

"The thing that Marshall does very well, I think, is bring new manufacturing techniques in house," said Hedtke. It's why we're vendors. We weren't vendors 50 years ago, but we are now because the customer needed it. When our vendor couldn't do this, we figured out over a weekend how to do it and service our customer, and we did it. And that became this giant piece of our business now, which is the forming of metal." 

Design for Optimum Manufacturability

One customer came to Marshall with a 7-piece pinned component that Marshall helped them redesign to a single-piece part. How was Marshall able to achieve that degree of parts consolidation from a seven-piece assembly down to one part?

"We had to sit down with the customer and review what the design requirements were," said Hedtke. "It had a feature that needed this to happen, and it had a feature that needed that to happen, and the original design was basically to add a whole other component to the process whenever that product needed another feature added. And we said, 'OK, it needs to be able to do this, this, this, and this, and these 7 things,' so we came up with a shape that would do all of that in one. So, instead of having a bunch of added pins and rods sticking out of it, we found out where it needed to meet the requirements and we shaped the material so that it was only what was needed, and no more."

Mike Hedtke and Tom Plantenberg took time out recently to talk with Design2Part Magazine about Marshall's work for the medical industry and how the company differentiates itself from other manufacturers. Following are edited excerpts of our conversation.

D2P: To what do you attribute Marshall's ability to Design for Optimum Manufacturability?

MH: It's certainly the quality of our engineers. We've been in business since 1952, or somewhere in that range. We've seen a lot of stuff, and we've been in a lot of different types of industries where we've seen what stampers can do; we've seen what EDM, sinker, wire—all the types of machining that's out there—can do. We've certainly been experienced with these processes and our skill set is such that we can take that base knowledge and put it together and find the best way to come up with a solution.

D2P: What is it about projects for the medical industry that makes them more challenging, and how do your capabilities offer advantages in meeting these challenges?

MH: Often, what we see with medical companies is they are asking us to ensure that the processes are very well maintained. Validation and verification is important to medical customers, so what you're doing when you're validating a process is making sure that not only can you make some prototype parts for them, but you can make those over and over again. And that's the difference with medical companies; they're much more rigorous in that regard.

Tolerance wise, certainly, they're high end requirements. Some of the materials that medical uses are a little more challenging than the standards. We do a lot of 17-4 heat treated materials, stainless steels, and you don't often see that in regular industry. Cobalt chrome is another one that gets kind of challenging. Even the regular stainless steels, depending on how high a tensile strength you want, can get interesting, especially when you're doing metal forming or metal bending.

D2P: Are you seeing any trends within the medical device industry that are influencing the development of new types of products?

TP: We see the need for specialized bending because we're getting a lot of inquiries for it.

But Marshall is one of those companies that's unique in that we understand the innovation of our  customers. Our customers are after new ways to help surgeons and the medical professionals do their jobs. And it takes a special company to keep up with that type of innovation. So when we're talking about being innovative ourselves—Marshall Manufacturing—we're actually talking about coming up with ways that meet the demands of these particular companies that are creating things that didn't exist before, and finding ways in order for those parts and those procedures to be accomplished. I think part of that also comes from the fact that we are so willing and able to create something that didn't exist before—both in terms of tooling and software.

MH: Another trend that I'm seeing, actually, is a willingness on the part of medical companies to have input from people that can not only prototype for them, but produce the part. Prototyping doesn't necessarily get you a production part. You need, actually, an understanding of how it's going to be produced in production terms.

A lot of the medical companies have separation between their R&D people and their product development people, and what we're seeing is that tie becoming closer, where we're actually getting access to both R&D people and the product development people. And if we're all on the same page before we move forward with it, the part becomes a whole lot more robust and produced faster and less expensively.

TP: I know we talked about precision machining of bent rods, but the laser cutting is really another important part of orienting features on a laser cut tube and bending the tube in specific—sometimes three dimensions.

MH: Right, and there's opportunities for adding those features in straight form—that's a whole lot cheaper—and then bending, or vice versa. And a lot of the parts that we're seeing, even if it's relatively simple bends, what gets it complicated is all the features around those bends, and how close those features need to be to the bends, and how they're called out.

A lot of times, an engineer is used to calling out machining tolerances of plus or minus 5 thousandths (+/- 0.005). Well, that doesn't necessarily apply when you're dealing with the spring back involved in bending a big tube in a big swooping radius; 5 thousandths (+/- 0.005) doesn't make any sense. But if we call it out where it needs to fit within this shape and these features need to be within this position, it's a whole lot better, and the print becomes manufacturable at that point.

TP: And we're also innovative with how we check parts. A lot of things we do are three dimensional, so instead of doing everything on a CMM or under a vision system, the operator will sometimes 100 percent check them, like in a solid gauge, while the parts are being bent. 

MH: Yes, a custom, drop-in gauge.

TP: So that they know right then and there the part's good, or if it needs tweaking.

MH: And typically we want to 100 percent inspect our bends while running, without any cost to the customer.

TP: I think that's a good example of Marshall's desire for a design for optimum manufacturability, because really there are three things that fall under that umbrella. One of them is the innovation that we're talking about; the second one is the full capability set of the company. We can literally make just about anything that a customer brings to us. But the third one is the quality, which we were just alluding to. It goes beyond simple recognition through a CMM; it goes much further than that because it has to, often.

D2P: Are there any cases where a design engineer would come to you with an idea where they don't necessarily know what the part is going to look like, and you're able to help?

MH: Yes, a napkin sketch. It often happens.

TP: That's really where Marshall shines.

MH: And that's what we're alluding to, that the more you can deal with that stuff upfront, before we even start cutting metal or forming it, you're so much better off. The more we know about the fit, form, and function of the part, the better off we are.

TP: It's great if we can be included in the concept stage, versus once somebody else has had the manufacturing and has produced mating components and things like that. It's better if we can be in front of that.

D2P: What are some of the particular advantages of laser welding for your projects versus other types of welding processes?

MH: We've found that laser welding is much more common in the medical industry than other places. Laser welding stainless steel is very, very common in the medical industry. We've had projects where we've had to laser weld some parts, and we've sent them out. And over the course of time, we've decided that we need to learn it in house because it's much better for our customers if we can do it in house.

TP: And we've also run across quality problems sourcing it out.

MH: It's the same thing. You send it to places that specialize in laser welding, and you don't like their quality, so you bring it in house and learn it yourself. It's crazy, but it works and our customers are happier because we do it.

This technical information has been contributed by
Marshall Manufacturing

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