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Fine form: Making microwire components for medical and other devices

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July/August 2013 Volume 6 Issue 4

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By Larry Adams

Senior Editor

(847) 714-0182

ladams@jwr.com

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Deflection coiling of a 0.008”-dia., nickel-coated stainless steel wire. Image courtesy D.R. Templeman.

If there is a common theme echoed by manufacturers of microscale coils, forms and springs—all produced using microwire—it is that customers want more from less. That is, less in terms of size, not capability.

Microwire-based products are used in a growing number of devices in the medical, consumer electronics, aerospace and safety industries.

Microcoils are typically wrapped or bent in a coil, while microforms are usually manipulated by automated bending machines for straightening, bending, swaging, looping, flattening, radiusing, stamping and knurling. While stainless steel is a predominant wire material for many manufacturers, companies also work with exotic alloys such as radiopaque, shape-memory alloys, medical-grade alloys and MP-35N nickel-cobalt base, niobium and titanium alloys.

To satisfy their customers’ smaller-is-better requirements, microwire-component manufacturers often let their engineering talents mesh with their imagination to tweak machines, build new devices and conjure ways to best fixture their tiny wire wares.

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Custom Wire Technologies works with ultrafine wire that measures down to 0.001" in diameter. Image courtesy Custom Wire Technologies.

As Bob Boldig, president of Custom Wire Technologies Inc., put it: “Our customers are finding more ways to apply smaller and smaller wire materials to their products, and we have to keep up. It is tough to go smaller when you are already working with material that is 0.001" and 0.002" in diameter—sizes that some people can’t even see with the naked eye—but that doesn’t stop us from trying.”

One project that challenged the Port Washington, Wis.-based company required drilling a small hole in a wire component. While Boldig couldn’t discuss the end product, he said Custom Wire Technologies is making holes with a 0.006"-dia. drill, just two times the size of a human hair.

Even those with the eyesight of a jet pilot need help seeing the material. “Almost everything we do is done under magnification of 100× or more,” Boldig said.

Another fine-wire specialist is Motion Dynamics Corp., Fruitport, Mich., a maker of microsprings, electrical contacts, medical catheter devices, guide wires, clips and other products from wire as fine as 0.0007" in diameter, according to Steve Dufon, sales and marketing manager.

And The D.R. Templeman Co., Plainville, Conn., a maker of products using microwire, recently produced “a spring for a customer out of 0.0031"-dia. beryllium copper wire,” according to Richard Williams, president.

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A custom-built machine packages microwire-based products. Image courtesy Custom Wire Technologies.

As wire gets progressively smaller, the material may lose consistency and be harder to work with, which is why Williams advocates continuous inspection. This is particularly important for certain microwire products the company makes, such as a spring for a fire sprinkler system. “If the spring doesn’t cause the alarm to go off at the right time, it could be catastrophic,” he said.

Closer look

Magnifying tools are ubiquitous at D.R. Templeman’s facility. Workers wear visors with an attached magnifying lens, magnification devices are stationed in front of machines, optical comparators magnify parts at 50×, and digital cameras project images onto video screens for closer examination and digital measurement.

Seeing the material is one thing, but fixturing it so it can be machined or inspected is another, added Boldig. “That is the challenge,” he said. “You can see the material, you can look at a drawing, you can conceptualize what the finished part will be, but the reality is, when you are working with something so minute that a thousand finished parts could fit in the palm of your hand and look like flakes of pepper, that is a challenge that takes creativity to solve.”

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A microcoil in the jaws of a micrometer. Image courtesy Shannon MicroCoil.

The company uses “anything and everything” for fixturing, from tweezers to adhesive boards to magnets. “We routinely make parts with what we call ‘a transition of scrap’ on the front and on the back so that we can hold it, and in between is the ‘good part,’ ” said Boldig. The remnants are later trimmed away and the surface of the good part is polished to specification.

Methods of production

In some ways, making a microwire product is not so different than making its macro counterpart. Forming a wire coil is typically done one of two ways: wrapping it around a mandrel and then removing the mandrel, or deflecting the wire against one or more coiling points.

D.R. Templeman uses both methods. Its smallest compression springs are coils wound with spacing between the coils so that they can be compressed from their free length to a shorter operating length. To date, the tiniest compression springs made by D.R. Templeman are produced with 0.005"-dia. wire with an OD of 0.025". These springs are wound with a deflection coiling process on an automatic spring coiler.

The company makes spring guides, which are long, slender, tightly wound coils, using a mandrel winding process. Mandrel winding can produce springs with a smaller spring index, which is the ratio of coil diameter to the wire size. The mandrel winding process also enables D.R. Templeman to make a more consistent product and to produce springs up to 50' long. But obtaining small-diameter mandrels can be a challenge. The company’s smallest mandrel is 0.007" in diameter. “Using that mandrel, we’ve gotten down to an OD of 0.0016" with 0.004"-dia. wire,” Williams added.

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Motion Dynamics can produce microsprings from wire as fine as 0.0007" in diameter, as exemplified by the spring in the numeral zero on a penny. Image courtesy Motion Dynamics.

Spring index is a measure of how tautly a wire is wound and provides clues as to the best method to use in manufacturing the spring to the desired shape. (The spring index is the mean coil diameter divided by the wire diameter.) For deflection coiling, a key number is four. “Anything smaller than that and you pretty much have to mandrel-wind it,” Williams said, “because the wire deflection method cannot produce such a tight radius without frequent tool breakage.”

Geometry is key

Shannon MicroCoil Ltd., Limerick, Ireland, a maker of microcoiled and formed-wire products for the medical device industry, also uses CNC deflection coilers to process its wire forms, according to Ger Mullane, sales and marketing manager. To reach required geometries and tolerances, the company uses single- and double-point tooling geometries on its coiling machines. “We have full control over all geometries and can vary pitch and diameter in any combination,” he said.

Mullane said the company makes components from both round and flat wire. Round wire comes in sizes from 0.001" in diameter and up, while flat wire coils range in size from 0.002"×0.004" to 0.016"×0.028" in lengths up to 2.5m.

Deringer-Ney Inc., Vernon Hills, Ill., is a vertically integrated manufacturer with expertise in many metalforming technologies. It produces high-precision fourslide, CNC wire-formed and micro- coiled parts that are commonly used in the electronics, medical, automotive and aerospace industries. In many cases, the parts are made from custom alloys of silver, platinum, gold and palladium that are designed and produced in-house.

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Microsprings made for hearing aids. Image courtesy D.R. Templeman.

One of the strengths of this company is its range of capabilities. In addition to making raw materials, the company’s micromanufacturing  capabilities include stamping, insert molding, machining and cold forming. The company has produced components as small as 0.003" in diameter and can fabricate both wire and strip materials to diameters and thicknesses of less than 0.001", added Dana Dubuc, vice president of development.

Do it yourself

While not all companies have these types of capabilities, many can offer value-added services such as laser welding and sub-assembly. Another commonality between micromanufacturers is the need to modify their equipment to complete an order.

“We almost always need to make adjustments to our equipment,” Custom Wire Technologies’ Boldig said. “We end up removing adjustment levers and knobs and swapping them out to get the fine tuning we need to make microparts.”

Recently, D. R. Templeman retrofitted a spring coiler. The problem was that the machine previously utilized adjustment rods with a 10-32 screw thread that, when the knob was moved a 16th of a turn, it moved the tooling too much. “We replaced it with a micrometer head and one turn now moves the head [exactly] 0.025", Williams said.

At other times, manufacturers must build from the ground up. Recently, an orthodontist contacted D.R. Templeman looking for a better way to move the actual roots of patients’ teeth, said Williams.

“We worked with him to develop a tiny, double-torsion type of spring attached to an arch wire to apply force on the root of the tooth,” Williams said. “The spring needed to be so small and tightly wound that we built a bench-mounted winder that simultaneously wound the two sides of the double-torsion springs.” µ


Learn more about microwire products

For more information on microwire products, including videos of wire operations, wiremaking materials and post-processing, visit the following link: micro.delivr.com/2djsh


Contributors

Custom Wire Technologies Inc.
(888) 310-1430
www.customwiretech.com

Deringer-Ney Inc.
(860) 286-6101
www.deringerney.com

The D.R. Templeman Co.
(800) 203-4290
www.drtempleman.com

Motion Dynamics Corp.
(231) 865-7400
www.Motiondc.com

Shannon MicroCoil Ltd.
+353 61 311666
www.shannonmicrocoil.com

FtrAuthorAbout

Larry Adams is the senior editor for MICROmanufacturing. Telephone: (847) 714-0182. E-mail:  ladams@jwr.com.