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Articles from 2002 In July


Replacing the surgeon's scalpel

The Ancure Endograft system from Guidant Corp. eliminates the need for a large incision when repairing an aortic aneurysm. Collaborative design helped ensure the device's success.

One portion of the Hippocratic Oath physicians take is a vow to do no harm to the patient. Paradoxically, surgical procedures often require large incisions to allow surgeons access to specific organs. Much of the patient's recovery time is spent in healing these large cuts. Medical device designers are trying to minimize invasive procedures by developing endoscopic instruments that require only a tiny incision that heals quickly. These same designers are choosing injection molded plastic to house and support endoscopic equipment.

A recent entry in this field, the Ancure Endograft system from Guidant Corp. (Menlo Park, CA), exemplifies the trend toward less invasive surgery and offers a window on the need for teamwork in designing these devices. The Ancure system won a gold (first place) award in the 2002 Medical Design Excellence Awards competition presented by Canon Communications in June at the Medical Design & Manufacturing East show.

Deploying the Implant
Before we delve into the design and molding of this device, let's take a quick look at what it does. It is used to treat abdominal aortic aneurysm, a condition in which weakened walls of the aorta expand and threaten to explode. Without the device, a surgeon must make a large incision in the patient's abdomen to attach a blood-diverting sheath to the aortic wall.

Instead, the Ancure device requires only a 5-mm incision in the femoral artery (located in the leg) and is used in a stepped procedure. A catheter is inserted into the artery, and the sheath, or graft implant, is delivered to the aorta. It is remotely positioned, deployed, and fastened, and is used with a fluoroscope, along with markers on the product, that allow the doctor to see where the catheter and graft implant are located.

A relatively large-diameter graft and attachment system, up to 26 mm, is needed for the aorta. It collapses to less than 5 mm for delivery into the body. The delivery system handle includes numbered controls for manipulation and deployment of the implant, and clearly numbered safety tabs prevent out-of-sequence deployment. Benefits are said to include lower mortality, reduced complication rates, shorter hospital stays, and faster recovery.

Call for Design
When its in-house design engineers finished the functional engineering for the Ancure system, Guidant called Stirling Design to work on the housing, appearance, and user interaction issues. Other members of the design team included molder and tool designer Phillips Plastics, as well as resin supplier Bayer.

Loren Stirling, an industrial designer with more than 30 years of experience in plastics design, explains why the human interface portion of endosurgical devices is so critical. "In-house designers often deal with the total function and intent of the product. They must be focused on that part of it. Often, however, the rest of the human interface portions lose out to functionality. There is a balancing act that takes place between industrial designers and engineers to create the best product without losing functionality."

For one, this product had to be easy to use. "It's not what the surgeon is doing, but how they are doing it," says Stirling. "This instrument is essentially the handle for the puppeteer." The method of having a stepped process, a major part of the user interface, came out of meetings with Guidant's marketing group, which in turn interviewed doctors regarding their preferences. To add to ease-of-use, Stirling also minimized the overall size of the product after early prototype testing.

Another consideration was the material selection. The resin had to meet FDA requirements, structural requirements, and appearance standards. Says Stirling, "There is a brake that is under load constantly in the instrument's freestanding position. A surgeon releases the brake to place the catheter. Since this area is always under pressure, we needed a material that would not creep under load." Bayer provided material samples and documentation, and the team finally decided on an FDA-approved ABS blend.

Comfort was yet another target. "We made sure that the device felt comfortable in a surgeon's hand, and that any user could get a good grip on the pull rings, brake handle, and balloon actuator. We also eliminated sharp edges and flat parting lines to minimize flash," Stirling says.

Team Effort
Phillips Plastics' designers worked on design for manufacturability and assembly, adding draft and shutoff angles and determining nominal wall thicknesses. In addition, Phillips suggested P-20 tooling to meet the low volume requirements and time-to-market goals. Most tools were ready in four to six weeks, according to Steve Schultz, Phillips' project engineer.

Today, Phillips supplies Guidant with 21 molded parts, many of which have a sequence number printed on them to assist the surgeon in correctly deploying the implant.

All team members agree that the success of this breakthrough device required input from each party. "The only way to achieve the optimum product is to collaborate," says Stirling. Paul Bell, Guidant's design engineer adds, "We always strive to work cooperatively with our suppliers, but on this program, it went to new levels."

Contact information
Stirling Design, Aptos, CA
Loren Stirling; (831) 662-2414
www.stirlingdesignonline.com
[email protected]

Innovation in medical catheters

Trifurcate molding technology reduces leakage in catheter assemblies and eliminates the need for heat shrinking or bonding adhesives.

Life as a medical molder in today's competitive market means being creative and innovative. Pelham Plastics Inc. (Pelham, NH) is only five years old but has rapidly achieved a name for itself as an innovative medical molder. Pelham's R&D department has recently developed a method for catheter insert molding that reduces leakage in multilumen configurations.

The company uses Arburg's U-model injection molding machines that allow it to mold horizontally, vertically, and on the parting line, along with a proprietary molding process to insert mold trifurcate connections at the union of multilumen catheters and the adjoining port tubes. Three of the company's four molding presses (ranging from 40 to 110 tons) are the U-model type, says Stephen Lee, operations manager for Pelham.

The trifurcate molding technology has proved to reduce leakage of catheter assemblies, thus minimizing component rejections and assembly field failures. Additionally, it eliminates the need for heat shrinking or adhesives for bonding, which are often inconsistently applied and lead to leakage, resulting in high product failure rates. Other problems include curing and poor aesthetics associated with the adhesive.

To allow for deployment of multiple devices in a single-catheter design, each lumen has a port, or single tube, through which a specific device is introduced to the catheter. The union of these ports with the catheter can present aesthetic and functional challenges to both design and manufacturing engineers.

Pelham molds the trifurcate simultaneously, securing the three tubes to the catheter and providing a consistent seal upon molding. Using the ports as inserts while molding a trifurcate at the union is an ideal approach to both reducing leakage and creating an aesthetically pleasing design.

Lee explains that the specialty molds used to produce the multilumen catheter have custom core pins to allow for the proprietary molding process. "All in all, it's a pretty complex component," says Lee.

Pelham's 10 employees all have backgrounds in the medical device industry, and this level of expertise has put the young company on the map with innovative solutions. "We do quite a bit of R&D," Lee says. "We can take an idea drawn on a napkin and come up with a design solution, which is why we get a lot of work from referrals."

Pelham recently moved into a new 10,000-sq-ft, custom-built facility with a white-room environment for molding and assembly, and specializes in insert molding and overmolding for the medical industry. The company became ISO 9000:2000 certified last year. 

Contact information
Pelham Plastics Inc.
Pelham, NH
Stephen Lee
(603) 886-7226
www.pelhamplastics.com

Arburg Inc., Newington, CT
(860) 667-6500
www.arburg.com

Focus: Medical Plant Tour: Metal injection molding smiles

Ortho Organizers is a vertically integrated manufacturer of orthodontic products, offering a full line of services. One hundred percent of its dental brackets are metal injection molded.
Manufacturing the small brackets used in its orthodontic products used to be a pretty ugly process for Ortho Organizers Inc. of San Marcos, CA. Its brackets were investment cast south of the border. Almost 90 percent of the metal used was wasted in sprues and runners. Excess material was sold to scrap dealers. The turnaround time was typically 30 days with the time wasted waiting on lines at the Mexican border. And capping things off, good parts yield ran anywhere from 30 to 60 percent. There had to be a better way.

Ortho found that better way in 1994 when it licensed metal injection molding (MIM) technology from Injectamax Corp. (Escondido, CA). MIM is a multistep process, involving feedstock preparation, molding, debinding, sintering, and, sometimes, secondary finishing procedures. Nevertheless, using manufacturing principles enlightened by lean thinking, Ortho has reduced the time wasted waiting for its parts from 30 days down to just two. That means smaller parts inventories, faster reaction to market changes, and lead time reductions.

With MIM, Ortho's good parts yield now is in the 90 to 95 percent range. Materials costs have been substantially minimized as well—it can mold 10 brackets per gram and MIM sprues and runners can be recycled and reused. What's more, Ortho now is able to achieve excellent part definition on all of the complex surface geometries of its brackets, which eliminates the need for many secondaries.


Ortho's brackets once were investment cast. Nearly 90 percent of the material used was scrapped, good parts yield was as low as 30 percent, and turnaround times were as high as 30 days.
Ortho has also taken on contract manufacturing for other orthodontic companies, as well as firms outside the industry.

Today, 100 percent of Ortho's entire bracket product line is done in MIM. Its entire production capacity is dedicated to serving the orthodontics marketplace, estimated to be a $700 million industry worldwide. MIM presently accounts for about $100 million of this market. Dentaurum J.P. Winkelstroeter KG (Ispringen, Germany) and Rocky Mountain Orthodontics (Denver, CO) also are orthodontics MIM molders, but our appointment's with Ortho. Let's tour.

MIM Mold Specialists
Our tour guide is Stephen Huff, director of clinical relations and new product development. He tells us that Ortho is a privately held company that is almost 30 years old. Most of top management has either been with the company, or in the business, for just as long.

Operations are spread over three buildings at Ortho's manufacturing campus in San Marcos, comprising a total of 60,000 sq ft. Our first stop is the 12,000-sq-ft engineering/moldmaking center. The company employs moldmakers and toolmakers, who handle the fixtures, EOAT, and other devices. Ortho uses Pro/E CAD software both for part and mold design, and SurfCAM via an IGES import.

It builds complete unit-frame molds for its MUD bases, about 100 every year, including the cores, cavities, and ejectors. Most of its bracket molds are 5x8 family molds with up to eight cavities. Some require artificial balancing, using a larger runner near the nozzle, for instance—a technique learned through trial and error.

Today, Ortho molds up to 9 million parts per year on its Boy injection molding machines at yields of up to 95 percent, turning around finished parts in two days. Brackets are molded in fully automated manufacturing cells running subgated, eight-cavity family molds at 30-second cycles. Each bracket costs $2 to $5. The small brackets are removed and deposited into a press-side product handling system designed and built in-house.


Vital Stats
Ortho Organizers Inc., San Marcos, CA




Square footage: 60,000, among three buildings

Annual sales: $18 million to $22 million

Markets served: Orthodontics

Parts produced: 6 million to 9 million/year

Powders processed: Nickel-free cobalt chromium alloy, 17-4 PH stainless steel

Feedstock consumption: 84,000 lb/year

Feedstock sourcing: Proprietary, Advamet

No. of employees: 200

Shifts worked: Two shifts, five days/week

Molding machines: Four, 22 to 30 tons, Boy

Debinding/sintering capacity: Solvent debinding, four debinding/sintering

furnaces

Secondary operations: Polishing

Internal moldmaking: Yes

Quality: ISO 9001

Ortho also uses three-plate molds. Materials of construction are usually A-6 and D-2. In operation, Ortho heats the A half of the mold, blowing the feedstock through the gate before it freezes in the cavities in the cooled B half.

A Mitsubishi EA8 sinker, which was a recent addition to its moldmaking equipment capacity, has all but eliminated Ortho's use of copper electrodes. The surface finishes it achieves with graphite are good enough to obviate polishing.

The Shop Is the Cell
Ortho's main MIM manufacturing floor is laid out like a lean manufacturing cell. In a lean cell, machines of different types sequentially perform their different functions for the waste-free, single-piece flow of products, and for a more flexible use of human resources.

Like many lean cells, Ortho's molding machines, mixing tanks, and furnaces are laid out in a U-shaped pattern, like a horseshoe, or, considering Ortho's product line, like teeth.

The shop floor's high ceilings and open doors keep things cool. Bright mercury lights make things easy to see. And the durable epoxy coating on the floors, the same kind used in aircraft hangars, minimizes wear and tear.

Four small-tonnage presses from Boy Machines Inc. (Exton, PA) with mold temperature controllers from Sterling (Milwaukee, WI) are laterally configured along one wall of the shop. Three of the machines—with 30, 25, and 22 tons of clamping force—are equipped with Boy's Procan machine control system. The remaining 22-tonner, an earlier model, is not.

Automated Single-piece Flow
Injectamax uses Boy machines. They were a part of Ortho's licensing requirements. Ortho is considering the purchase of a larger 50-tonner. Business is good. In fact, David Dunn, director of operations, tells us that Ortho has exceeded the orthodontics industry's growth since its inception.

The three newer machines are equipped with robotic sprue pickers. These are the bracket molding presses, Ortho's main MIM product line. Green parts are retrieved from the subgated molds and are immediately placed into a press-side device that segregates the brackets by cavity. Scrap is carried over to a granulator from AEC/Nelmor Inc. (Woodale, IL) for reuse.

Ortho uses heated nozzles for its eight-cavity molds. To improve flow through small, sub-millimeter gates, the feedstocks are run at a temperature just below the breakdown temperature of the polymer/paraffin-wax binder systems.

Huff says the material freezes off at the gate all the time, thanks to cooling the mold's B half. The company makes its own feedstocks. It also purchases Advamet feedstocks from Advanced Metalworking Practices Inc. (Carmel, IN).

A Molded Competitive Edge
After they are debound and sintered, the brackets are polished in a room off the floor. The micro-etched bonding surfaces of Ortho's brackets (the base where the brackets adhere to the surface of the tooth) are micromolded in. Polishing is the only secondary operation required for brackets.

In addition to brackets, Ortho manufactures a full line of orthodontic products and appliances, including a precision molded intraoral bite corrector that provides gentle continuous force to teeth by means of two joined cylinders. It's designed for function, not looks. That's why they've nicknamed it "The Terminator" in the shop.

The third building on the campus manufactures shape memory wire out of a super-elastic nickel titanium alloy. The wire is used to fashion coil springs that are used in Ortho's orthodontic appliances. Once heated in belt furnaces and bent into shape, the wires remember their shape.

Through field reps and its B2B telemarketing department, Ortho sells to dealers in 75 countries. The competitive part costs and quality it has been able to achieve by using MIM have allowed Ortho to penetrate developing world markets. About 20 percent of its business is in Latin America.

In closing, Huff says, "With MIM, 99 percent of our manufacturing cost is in our capital equipment, not labor. That's one reason why MIM is staying afloat in the U.S. MIM is the solution worldwide."

Molds for its brackets, Ortho's largest-volume MIM application, are typically eight-cavity family molds. Only the B half of the mold is cooled. Ortho's Huff says material freezes off at the gates every time.


Ortho has four furnaces for thermal debinding and sintering, two of which were built in-house. It had only two furnaces two years ago. Ortho designs and builds all of its molds, about 100 per year. This North-South Machinery Mitsubishi EA8 sinker can run 24/7. Its programmable accuracy has nearly eliminated Ortho's use of copper electrodes.


The product handling system segregates the green brackets by cavity, improving flow and traceability. Chemical solvent debinding for some of its feedstocks is performed in this environmentally friendly, closed loop unit.

Contact information 
Ortho Organizers Inc.
San Marcos, CA
Stephen Huff
(760) 471-0206
www.orthoorganizers.com

Head immobilizer wins award

When emergency medical personnel arrive at the scene of an accident, one of the top priorities is to immobilize patients at risk of spinal cord injury. The SpeedBlocks head immobilization device was designed to meet this need. It's comprised of a universal base that mounts to the backboard and a pair of blocks that snap into the base on both sides of the patient's head. The blocks can be adjusted and are strapped to each other. This design brought a Medical Design Excellence Award at the June MD&M East show in New York City to design firm Machineart Corex and Laerdal Medical Design & Development Group.

The design team had to take into account human factors, mechanical design, material selection, part optimization, mold flow analysis, and an attractive and cleanable form. They wanted to give customers a hybrid system that was reusable but still inexpensive enough to be disposed of when significantly contaminated. A high-density polyethylene from United Plastics Group (Chicopee, MA) was chosen because of its resistance to cleaning solutions. A design was chosen that allows the mounting base to be disinfected and reused, while the patient contact parts (the blocks with straps and base pad) are replaceable at a lower per-use cost than most disposable devices. The entire system costs about a third of the most common reusable head immobilizer.

SpeedBlocks were molded by Promold (Cromwell, CT). The base measures 16 by 8.5 by 1 inches and weighs 8 oz. The head block measures 7.2 by 7.1 by 4 inches and weighs 5.2 oz.

Contact information
Machineart Inc., Hoboken, NJ
(201) 714-9846
www.machineart.com

Liquid silicone grows up in medical market

Tooling for liquid silicone molding is more self-contained than conventional molds. Each mold has its own cartridge heaters, thermocouples, and insulation for better portability.
Injection molding liquid silicone rubber (LSR) is tricky business, and it isn't something with which a lot of molders have expertise. Even fewer mold shops understand the nuances of building a tool to mold liquid silicone. M.R. Mold & Engineering (Brea, CA) is one of a handful of shops in the U.S. that is dedicating its resources to gaining and maintaining a cutting edge in this technology that is seeing its best opportunities in medical applications.

Rick Finnie, president of M.R. Mold, has been building tools for liquid silicone molding for most of his career. An increase in demand for molds in this arena, however, has driven the company to invest in an Engel liquid silicone press so that M.R. Mold can test molds as well as perform R&D on the development of cold runner systems.

"Something is needed to perfect this process. Automation and a better mold are the answers," says Finnie. For years, he points out, molders of liquid silicone have lived with the problems of flash and the waste of runner systems. "They've just put up with it because there was no alternative," Finnie adds. "Now, customers are demanding no flash and no waste. We've got some catching up [to do] with the Europeans in this regard. We're working with Kipe Molds on developing cold runner systems and automation, trying to compete with the Austrians in this arena."

Finnie recommends using a moldmaker that has experience in liquid silicone molding and moldmaking because of the many idiosyncrasies of the process. "There's a lot that is completely different about LSR molds vs. regular thermoplastic molds," he adds.

Not Your Standard Tool
To develop his expertise in this special process, Finnie recently traveled extensively researching cold runner technology for these molds. Tooling for liquid silicone molding differs from conventional molds in that it is more self-contained, Finnie explains. "Each mold has its own cartridge heaters, its own thermocouples and insulation, and therefore can move from press to press very easily. Runners and gates can be very small because liquid silicone flows so easily. However, it also flashes easily, so tight fits and tolerances are critical."

To overcome problems with flashing, Finnie uses hardened tool steel in the cavities and cores, and mold base plates are made out of 420 stainless steel. Shutoffs have to be right on, Finnie emphasizes. "Conventional ejector pins will flash because they're not accurate enough," he says. "We use custom ejector pins that are exactly round, or reverse-taper ejector pins."

Air trap is also a big challenge, Finnie notes. "We have to be careful with venting because molders are worried about flash in the vent." One solution is to pull a vacuum on the mold. "It's a real Catch-22," Finnie says. "Some customers don't like vents in the mold, but it's a necessary evil."


Molded medical products have benefited from liquid silicone rubber thanks to its clean processing and excellent cure rate—around 1 mm in 5 seconds.
Ideal Applications
Finnie's success building tools for LSR molding applications includes molds for parts that other shops said couldn't be made. In one instance, Finnie constructed a mold in which the core bar rotates out of the mold with a rack in order to remove the part from the mold.

Some of the components for which he has built molds include a reseal device that is inserted into IV lines to allow for the injection of medication directly into the line. "They've tried to eliminate the use of needles as much as possible," notes Finnie. "In these needleless sites, they can inject a supplemental medication, and when they pull the syringe out, it has to reseal."

Because of the peculiarities of LSR, conventional thinking is that these molds can't run automatically. Finnie has proved that wrong, too. "We can run liquid silicone under full automatic conditions," he says. "In fact, you can't work out the bugs until the mold runs fully automatic."

Liquid silicone rubber is ideal for medical molding applications, Finnie notes. "The whole process is so clean. The material comes in 5- or 55-gal drums, which is then pumped out directly into the barrel of the molding machine, so there are very few problems with contaminants in the material."

Liquid silicone rubber also has an excellent cure rate—about 1 mm in 5 seconds. "So, if you have a component with a 2-mm wall thickness, the part cures in 10 seconds," Finnie says. The bottom line is that molders can achieve fast cycle times—as low as 15 seconds.

Because liquid silicone rubber is inert, it doesn't cause problems that other rubber products do, such as skin irritation or allergic reactions. It's becoming a popular material for various medical uses like oxygen masks, not only for the medical industry, but for scuba diving equipment as well. M.R. Mold has also made tooling to produce the small, nasal cannulas for oxygen delivery systems, ear tips for stethoscopes, and masks for resuscitation bags used in emergency medical procedures. Liquid silicone is ideal for use in diaphragms or in applications in which any type of seal is required. Catheter tips and the Y portion of the catheter are molded of liquid silicone, generally overmolded onto the tubing.
Contact information 
M.R. Mold & Engineering Corp.
Brea, CA; Rick Finnie
(714) 996-5511
www.mrmold.com
[email protected]

By Design: Polypropylene part design, Part 2 – Living hinges

Livinghinges-1-Des_Beall1.gif
Figure 1A, 1B. Without a living hinge, this box would require two molds, two molding operations, and assembly.

In this bimonthly column, Glenn Beall of Glenn Beall Plastics Ltd. (Libertyville, IL) shares his special perspective on issues important to design engineers and the molding industry.

Polypropylene is the ideal plastic material for integral, injection molded hinges. Polypropylene (PP) part design details were reviewed in the June 2002 IMM "By Design" article. This article discusses how to design strong hinges with extended flex life.

A few years after PP's introduction in 1957, engineers at Enjay (now ExxonMobil) noticed an unusual phenomenon while studying pigment dispersion in very thin-walled color chips. Below a certain thickness, the PP molecules oriented in the direction of flow. Bending perpendicular to this orientation resulted in a stronger part that did not break with repeated flexing. Bob Munns, who worked at Enjay at the time, coined the term "living hinge" and the name stuck.

The living hinge was introduced to the industry as a hinged recipe box at the 1963 NPE. Over the next 40 years, creative design engineers used living hinges in thousands of applications ranging from dispensing closures with hinged caps to automobile gas pedals and carrying cases. The current trend for parts consolidation and assembly minimization has created a renewed interest in integrally molded hinges.

Living hinges can have many shapes and functions. One common application is the pill box and cover shown in Figures 1A and 1B. These parts could be molded separately, but that conventional approach would require two molds, two molding operations, and assembly. Connecting the box and cover with a hinge allows both parts to be produced in one molding operation. This reduces cost while enhancing end-user convenience.

Living-Hinges-Des_Beall2.gif
Figure 2A, 2B. Thicker does not necessarily mean stronger when it comes to living hinges. The proportions shown here have remained essentially the same for four decades, and demonstrate the need to balance a hinge's thickness, radius, and length.



Design Criteria
Over the years, the industry has developed a good understanding of the relationship between material selection, part design, and processing that allows living hinges to be flexed more than a million cycles without failing. The proportions for a living hinge, as shown in Figure 2A, have remained basically the same since the early 1960s. The key design details are the thickness of the hinge, the radius below, and the recessed flat section above the hinge.

The thickness of the hinge must provide a restriction to melt flow that orients the molecules across the hinge. There is a significant decline in molecular orientation when the thickness of the hinge exceeds .015 inch. A thicker hinge is more resistant to bending, but it is a mistake to believe that it is more robust as it has less molecular orientation and a reduced flex life.

Bending the hinge, shown in Figure 2B, stretches the material on its bottom side. The thicker the hinge, the more stretching there is. With hinge thicknesses greater than .015 inch, the stretching can exceed the elastic limits of the material. This results in microscopic surface cracks that reduce the flex life of the hinge. PP materials with a high percentage of elongation are helpful in this regard.

The full .030-inch radius under the hinge is the ideal shape for melt flow through a restricted area. That radius also ensures that the hinge bends along a straight line at the apex of the radius.

As the hinge is bent, it stretches and deforms. The recessed flat section above the hinge allows the box and cover to fit together accurately while providing an open space for the deformed hinge (Figure 2B). The flat section above the hinge must be .060 inch in length. Its depth must be at least .005 inch to avoid a sharp bending of the hinge.

The force required to flex the hinge is determined by its thickness. This "feel" of the hinge is difficult to simulate, and as a result, the thickness of hinges is frequently changed after the first molding in order to create the desired feel. A trick of the trade that simplifies tooling modification is to start with the flat section above the hinge having a depth of at least .015 inch and a hinge thickness of .006 inch. If the cavity cannot be filled or the resulting hinge feel is too soft, the depth of the flat recessed section can be easily reduced to produce a thicker, stiffer hinge that is easier to mold.

Molding Considerations
The cardinal rule for good molding is to maintain a uniform wall thickness. Living hinges are a gross violation of that design rule. The restriction to melt flow across a hinge invariably creates a pressure drop on its far side.

The box shown in the opposite figures measures 3.250 inches by 2.500 inches with a combined height of 1.150 inches. The nominal wall thickness is .060 inch, with the gate located on the bottom of the box. A computer-aided moldfilling analysis indicated an average end-of-fill cavity pressure of 6687 psi in the box. The average cavity pressure in the cover was 3096 psi, with a low of only 743 psi. The reduced cavity packing pressure results in more mold shrinkage in the cover than in the box. These differences in shrinkage may require modification of the mold in order to achieve the desired fit between the two parts.

The .010-inch radiuses leading to the .030-inch radius and the flat recess above the hinge are important melt flow and cavity packing pressure considerations. These radiuses also minimize molded-in stress.

One technique for overcoming the differential cavity packing pressure is to provide gates on both sides of the hinge. In these instances the gates must be positioned to avoid a weldline in the hinge.

In order to encourage molecular orientation, the gate location must provide for the melt to flow across the hinge in a direction perpendicular to its length. Best results are achieved if the melt reaches the hinge along its entire length at the same instant. If melt reaches the hinge in some locations before others, it stops flowing and starts to cool. This condition results in molded-in stress and weldlines in the hinge. Moldfilling analyses can help indicate the best gate location for molecular orientation, uniform melt flow, and the avoidance of weldlines.

Additional molecular orientation and flex life can be achieved by bending the hinge a few times while the material is still hot from molding.

Forcing the melt to flow through the hinge requires high injection pressure and speed. Molds must be built strong enough to withstand these pressures. Flexing of the mold plates by only .001 or .002 inch has a drastic effect on the performance of the hinge.

The shear developed as the melt flows through the hinge generates heat. A properly designed hinge mold provides for adequate cooling at the hinge. Rapid cooling reduces crystallinity in the hinge and produces a longer-lasting living hinge.

Inmold technique for no-paint, Class A parts

Check out this inmold decoration technique offered by DPI Automotive. It produced the wood grain console for the Chrysler Concord (shown right) and LHS, and also provided the carbon fiber pattern for the Chrysler 300M.

DPI makes the inmold appliqués from preprinted foil that is laminated to a thermoformable substrate, usually ABS, PC, or TPO. In addition to preprinted films, DPI can produce PC film with a custom laminate and thermoform it onsite. The pattern on the laminate can be made to reproduce almost any design imaginable, such as wood grain, leather, geometric designs, or solid colors.

Other finishes include body color matching paint and even brushed metal. For instance, automotive molder Pine River Plastics is working with DPI on a satin nickel finish for the interior of the new Chrysler Pacifica.

Appliqués are thermoformed, die cut, inserted into a mold, and backfilled with a lower-grade resin, producing a Class A surface part that doesn't need painting or topcoating. According to DPI's Len Poole, this is where the process differs from roll-fed foils. "In other systems, the resulting part has a low scratch resistance and must typically be topcoated, adding a secondary process," says Poole. "This is not the case with our inmold appliqué process."
Contact information 
DPI Automotive
Grand Rapids, MI
Len Poole
(616) 451-3061
www.dpiautomotive.com
[email protected] 

Faster than a speeding compression press

StackTeck's patented Compact Slide Action Mold technology allows higher cavitation in a smaller machine for the high-speed molding of tamper-evident closures. This technology is also available in stack mold configurations.
Ealias C. Joseph didn't particularly like one thing he saw at K 1998 in Düsseldorf, Germany. What he saw was an extrusion-compression molding system producing tamper-evident closures at a 1200-parts/min clip. Why didn't he like it, you ask? The answer's simple. Joseph is the engineering manager for closure molds at StackTeck Systems Inc. (Brampton, ON), a $50 million-plus injection mold manufacturing conglomerate. He knew it would take several molds running in several machines to match that output.

By the time K 2001 rolled around, Joseph and his StackTeck colleagues had developed something to compete handily with that technology. They call their patented technology CSAM, which stands for Compact Slide Action Mold. At K 2001 they displayed a 32-cavity CSAM mold, which can run in a 90-ton machine and produce 375 parts/min. A 2x32 CSAM stack, which runs in the same size press, produces 750 closures/min. Impressive, sure, but that's still not good enough, you say?

Well, a 2x128 CSAM stack, the largest StackTeck has designed, would run in a 500-ton machine and mold 3000 closures/min. And, remember, these are tamper-evident closures—tamper bands are formed in a single step. No secondary slitting is required.

"We were comparing a single extrusion-compression molding system to several injection molding systems. Now, with CSAM, we can compare them one on one. CSAM makes injection molding a more economical competitor and a more technically feasible alternative," says Jordan Robertson, general sales manager.

A pneumatic rack and pinion opens and closes the slides in a CSAM mold independent of mold opening and closing, thereby reducing cycle times. Also, the entire mechanism is recessed, saving space.


How CSAM Works
StackTeck's CSAM molds are not your typical slide-action molds. In more conventional ones, the slides have slide bars on which the slide inserts are mounted. Angled horn pins or delta cams mounted to the cavity plate drive the lateral movement of the slide blocks. And slide retainers have components that protrude from the mold sides. These components can enlarge the size of the mold, reduce possible cavitation, and obstruct space between the mold plates during ejection.

The component lubrication required on conventional slide-action molds can contaminate products when they're ejected. You've got to slow down the mold to handle the actuation of the slide mechanisms as the mold opens and closes. That means slower cycles. Parts can get trapped, too, and the slides can become misaligned, resulting in costly downtime.

CSAM technology is something altogether different. It uses a pneumatic rack and pinion—a reciprocating driving rack drives two pinions. Each pinion drives a pair of driven racks, which are movable in opposite directions. Slides are always connected to the driven racks, so misalignment is impossible. The entire actuation mechanism is clean, compact, and recessed into the stripper plate, away from the mold parting line. And the slide mechanism is independent. It doesn't rely on mold opening and closing for actuation, so cycle times are reduced.

Modular CSAM technology substantially reduces the distance between rows of cavities, which optimizes the cavitation for a given machine. It eliminates the protrusion of components from the mold by eliminating the components that protrude. It's more compact, with no obstructions between open mold plates, thereby reducing any chance of greasing products. Part jam-ups are also eliminated. And CSAM molds allow higher cavitation in smaller machines. A CSAM stack can run in the same size clamp as a single-face CSAM in many cases.


Tamper bands are formed before the parts are ejected from a CSAM mold, so the cost of a secondary scoring operation is eliminated.
All For One
StackTeck developed its CSAM technology all on its own. It has a very active R&D commitment. Henry J. Rozema, director of commercial operations and innovation, heads a team that constantly looks at new projects and marketplaces to minimize threats to StackTeck's business, while targeting new growth opportunities.

StackTeck is lucky to have a treasure chest of resources to draw on, as well as top management that encourages creativity. StackTeck is a self-described "technology entity" comprised of three moldmaking firms, each one a specialist in its own field: Tradesco (thin-wall packaging, medical, stack molds, housewares), Unique Mould Makers (closures, screw caps, multicavity molds), and Fairway Molds (high-precision technical parts, multimaterial molds).

The StackTeck campus in Brampton includes two 100,000-sq-ft buildings and employs about 250. Fairway Molds, located in Walnut, CA, employs about 100. It builds roughly 170 molds/year in Canada, with machines ranging up to 1000 tons. Lead times for steel prototypes are four to 10 weeks and generally 10 to 22 weeks for production molds, depending on the product.

Joseph says he's pleased with the successful introduction of CSAM technology and promises that new innovations are coming. In CSAM alone, he says a 4x128 stack is the company's ultimate goal. (For more on StackTeck innovations, see "Lean Tool Solutions Found in Stack Molds," October 2001 IMM, pp. 68-70.)
Contact information 
StackTeck Systems Inc., Brampton, ON
Jordan Robertson
(416) 749-1698;
www.stackteck.com

Hybrid presses for a hybrid process

The TXH500-M60 is Husky's first new Hylectric magnesium molding machine. It has 550 U.S. tons of clamping force (5000 kN), 40 by 40 inches between tiebars (1020 by 1020 mm), a 76-oz (2159g) maximum shot capacity, and can reach injection speeds of up to 19 ft/sec (5.9 m/sec). On the right is Husky's latest, patent-pending TXM injection unit featuring robust construction, a two-piece barrel that separates melt preparation from injection, proprietary high-performance heating elements, and a special nozzle designed to prevent blowback.
Husky has carried all that it has learned about TXM—a hybrid diecasting/injection molding process for molding thixotropic metals like magnesium—over to its hybrid servoelectric/hydromechanical Hylectric injection molding machine platform. Husky revealed at the Third International TXM Magnesium Conference (May 22-24, Toronto, ON) that it expects to take orders this fall for 2003 deliveries, following the completion of Beta-site testing and validation protocols. Husky's Hylectric TXM machines will be available in sizes ranging from 120 to 1000 metric tons and reportedly will be price competitive with TXM presses from JSW Plastics Machinery Inc. (Elk Grove Village, IL).

Husky was licensed by Thixomat Inc. (Ann Arbor, MI) to manufacture and service TXM machines in North America and Europe in 1998 (see "Husky Licensed to Manufacture Thixomolding Systems," April 1998 IMM, pp. 112-113). The Japan Steel Works Ltd. (Tokyo, Japan) was licensed by Thixomat in 1991 to build TXM presses in Asia. Both OEMs compete for global market share, each with their proprietary machine designs.

More than 200 TXM presses are in commercial operation with Thixomat's 40 licensees. Less than a handful are Husky machines. These were built around its now-defunct G Series press platform. Husky began accepting orders in 1999, but marketing reportedly slid through the cracks shortly thereafter, largely because of the introduction of its Hylectric Series.

Officials of Husky's Thixosystems Div. are confident that the technical improvements they have made to their new Hylectric TXM presses will more than make up for any lost time. They are equally confident that machines bearing their mark will further advance the acceptance of magnesium TXM in the design and molding communities.

Two-piece Barrel Design
The hydromechanical clamp end of Husky's TXM Hylectric looks pretty much like its plastics molding counterparts. Husky sources say Hylectric clamps can run molds at lower tonnage requirements than any other machines—30 percent lower—and that they have the largest tiebar spacing in their class. They add that they can run 20 percent faster than other comparable machines.


A new Mg molding process

At the initial request of Sony Corp., Sodick Plustech Co. Ltd. (Yokohama-city, Kanagawa, Japan) has developed a magnesium injection molding machine that is unlike any other. It works like a plunger machine, except in this case the plunger is the material.
  • A solid billet of magnesium alloy is inserted into the injection cylinder, which has three zones of heating control. In one zone the solid stick of magnesium stays hard, in the next zone it is rendered soft, and in the last zone it is molten. 
  • With each shot, the hard zone is pushed forward, the soft zone seals the inside of the cylinder, and the molten zone is injected into the mold. Self-sealing reportedly minimizes flash and improves good parts yield. The process can repeatedly and accurately produce a wide variety of both thin- and thick-walled products, according to Sodick sources. 
  • Price for an 80-metric-ton Mg-Plus Model MP-80 is $365,615 (Â¥45 million); a 260-metric-ton MP-260 is $487,487 (Â¥60 million).

    The company plans to add 350- and 650-ton models in September and expects to eventually sell 30 units per year.

    Sodick Plustech Inc., Cypress, CA
    (714) 892-0322
    www.sodickimm.com
  • The TXM Hylectrics are equipped with Husky's proprietary Reflex platens. Reflex platens are designed to provide uniform force distribution, minimizing deflection, mold wear, and, of particular interest to TXM molders, flash. Also, a proprietary spigot nozzle is on the end of the machine nozzle. Since no carriage cylinder force is applied directly to the mold in the two-piece barrel design, there reportedly is no magnesium blowback. The result is predictable good-parts yield with minimal downtime, according to Husky engineers.

    The ultrahigh-speed, reciprocating screw shooter on the TXM Hylectric is a brand-new design. Like the injection units on Hylectrics for thermoplastics, a servoelectric screw drive is standard, but that's where the similarity ends. TXM barrel temperatures are up around 600C. And shots of the thermally conductive, quick-setting magnesium slurries are injected at speeds from 2 to 5 m/sec (16 ft/sec).

    The new inline Hylectric injector is built more like one you would find on a diecasting press. It's much more robust. The old unit was more like a plastics shooter. It was supported back at the cold end. Shock and load were distributed through the barrel, which had to be beefy enough to take it. The nozzle end of the barrel is supported in a cradle, which is clamped directly onto the stationary platen.

    Heating of the material is done in the first stage of the unit, which has a thinner barrel for better thermal conductivity. The second-stage barrel at the nozzle end is built thicker and stronger. A heavy casting running along either side of the barrel and butted up against the stationary platen is sized to withstand 1.5 times the force generated by melt injection to reduce shock and vibration. By separating melt preparation from injection and isolating force distribution, the unit is supported only where it needs to be.

    Too Fast to Profile
    Husky presently is using Inconel in its barrels. The two-stage approach may open up the possibility of using less expensive materials of construction. Electrical current going into each zone on the barrel is constantly monitored. One to three heating elements are used, depending on the zone. Husky has developed a new, top-secret type of heating element for its new TXM injection unit, one created to deliver the heat without burning out.

    TXM injection is too fast to profile. Magnesium is incompressible and flows like water, Husky technicians say. As soon as the runner sets up, you're done. Its TXM Hylectrics are equipped with a dedicated black-box injection unit controller capable of achieving 250-ms scan times.


    A fully integrated, dual-arm, top-entry servo robot is programmed to remove parts and spray mold release with minimal cycle time penalties. A smaller model than this demo unit will be used when systems go into full production.
    Conventional position sensors used in plastics molding can't keep up with injection speeds as fast as 6 m/sec. Instead, Husky prefers using a transducer that has been used in CNC applications. It is directly connected to the centerline of the injection piston and can deliver accurate readings at speeds of up to 20 m/sec. Vertical piston accumulators now are used to assist injection.

    TXM Secondary Systems
    Husky's Internet-capable PC-based Polaris machine control system is standard. Pierre Pinet, Thixosystems product manager, says it is conceivable that Husky could integrate the control for all of the downstream equipment in a TXM cell into the powerful Polaris controllers. He says Husky intends to take the same approach integrating TXM secondary systems as it does integrating plastics molding systems.

    Husky has switched from using one of its side-entry servo robots to a dual-arm, top-entry design. One arm is programmed for part removal while the other dispenses lubricant (mold release) after every shot. The activities of each are choreographed to reduce cycle time. An integrated air curtain draws out the mist and fumes. Husky also has integrated an automatic die lubricant mixing system, parts conveyors with integrated cooling fans, and an Argon gas management system with automatic switchover.

    Among a number of other specially designed auxiliaries, the company has developed systems for quick and easy screw removal and servicing to minimize downtime. These include a barrel stand with its own integrated temperature controller, a screw removal cart, and a screw-cleaning apparatus. A number of different screw sizes are presently available for each model of injection unit. Husky works with its network of strategic partners to outsource other secondaries such as hot oil mold temperature controllers—one each for the core, cavity, and sprue.

    Work on hot sprues is the first step Husky is taking toward developing its own complete hot runner systems. Hot sprues can eliminate the cone-shaped sprues typically found in TXM cold runner molding, in some applications saving as much as 40 percent of shot weight, reducing cycle times by 35 percent, and opening the processing window a little wider. Husky's TXM hot sprues presently use traditional mineral-insulated bands. They will be manufactured at Husky's hot runner facility in Vermont.


    Direct NAFTA sales for JSW TXM machines

    JSW Plastics Machinery Inc. (Elk Grove Village, IL) has formally announced that it is now selling its entire line of TXM presses (75 to 850 metric tons) in North America. The machines are built by the JSW Magnesium Injection Molding Div. in Hiroshima, Japan. JSW-PMI will use its existing network of plastics industry sales reps in the U.S., Mexico, and Canada to promote and sell its TXM systems. JSW-PMI also has technical centers located in Chicago, IL; Los Angeles, CA; and Monterrey, Mexico for demonstrations and mold trials.

    Until now, sales of JSW-MG machines were handled directly out of Hiroshima. JSW-PMI had been offering parts and service for them since 1999. JSW-MG has been building TXM molding machines since obtaining its license from Thixomat Inc. (Ann Arbor, MI) in 1991. JSW-PMI announced its expanded role in promoting TXM to North American molders at the Third Annual TXM Magnesium Conference (May 22-24, Toronto, ON).

    JSW Plastics Machinery Inc.
    Elk Grove Village, IL
    (847) 427-1100
    www.jswpmi.com
    Though Husky builds molds, it specialized in PET preform tools and has no intention of building TXM molds. Instead, it plans to develop strategic partnerships with a network of global TXM moldmakers, lending them its expertise in thin-wall moldmaking to build hybrid molds for this hybrid process that will run on its hybrid presses.

    Editor's note: TXM is IMM's abbreviation for the process of molding a thixotropic metal slurry usually referred to as "Thixomolding" or "Thixomolded," which are registered trademarks of Thixomat Inc.
    Contact information 
    Husky Injection Molding
    Systems Ltd., Bolton, ON
    (905) 951-5000
    www.husky.ca

    Branding: A new approach for molders and moldmakers

    Websites should differentiate the company, and not just describe it. Kelch's goal is to position itself as a products firm rather than a molder.
    When you think of branding, you usually think of products like Coca-Cola or McDonald's. Branding is the creation of that specific identity that, when the name is spoken, the product automatically comes to mind. It's the last thing a custom injection molding or moldmaking company thinks about when creating a marketing or sales strategy.

    However, says Susan Ball, sales and marketing director for Plastikon Industries Inc. (Hayward, CA), it's a strategy that can work just as well for a molding or moldmaking company as it does for Pepsi. "Branding doesn't have to be about products," says Ball. "Branding can be an alternative method of keeping your firm right out in front of the customer and leaving it there."

    Branding involves differentiating your company from the dozens or even hundreds of competitors out there who do basically the same thing you do. It means getting your brand so ingrained in the minds of customers and potential customers that they will think only of your company when someone says "molder" or "moldmaker," explains Ball.

    Plastikon, for example, has been establishing its brand for many years. "The company intuitively understood that its new building, a 90,000-sq-ft, state-of-the-art technology center, should speak to its brand," says Ball.

    The facility exterior is emblazoned with two modern logos, like its other locations, to demonstrate the consistency of the Plastikon brand. Though it's not necessarily known throughout the country, Plastikon's customers and target market see a brand that describes many of its services and capabilities such as engineering, customer service, and value. Those are woven into the company's promotional materials to present a consistent message.

    "Consistency is one of the keys to building your brand," says Ball. "Each and every area of the company must be formally integrated to be a part of this strategy."


    Outside Plastikon's new building, the company's brand is carried out in double signage.
    Communicating a Brand
    A big part of building a brand is communicating the right message to the right customers. Mary Scheibel, a principal with Scheibel Halaska (Milwaukee, WI), a PR and marketing firm, says that in her experience working with custom molders, the real value of a strategic, well-executed, brand-based program is often overlooked. "A quick review of molder websites will bear out that many are describing their companies rather than truly differentiating themselves from the competition.

    "Therein lies both the good news and bad news," Scheibel continues. "In a marketplace earmarked by shrinking demand and increased competition, there will be winners and losers. We believe the winners will be those who can embrace change, rethink their value propositions, and position themselves in the marketplace in a compelling and differentiating way."

    Kelch Corp. (Mequon, WI), a molder with a history of designing and manufacturing plastic products for holding and transferring fuel, made a conscious decision in the late 1990s to narrow its focus to fuel containment systems. "We had provided these products to leading OEMs for many years, but we also drew a significant portion of our business from contract molding other plastic parts," says Doreen Lettau, director of marketing and business development.

    In a market littered with thousands of injection molders, Kelch knew it would be difficult and costly to differentiate itself from the crowd when going after different contract molding jobs. "We looked instead at whether it made more sense to focus our resources on fuel tanks, caps, gauges, and sensors," explains Lettau. "We found there was enough of an untapped market for us to continue growing the business by selling our core products without having to chase down unrelated contract molding work."

    Kelch called upon its long-time relationship with Scheibel Halaska to help it communicate this new focus to its marketplace and employees. "Scheibel Halaska's work helped us reposition the Kelch brand in a way that reflects our strengths," Lettau says. "In particular, our brand is positioned in a way that lets us speak to the niche expertise we've built by designing and manufacturing plastic fuel tanks for more than 20 years, and caps, gauges, and sensors for more than 40."

    Gaining a Position
    Mary Scheibel sums up the company's goal: "Kelch wants to be known for its niche expertise, not as an injection molder, so the message to their market is, `We make fuel containment systems.' They're positioning themselves as a products company, not a molder."

    Creating brand awareness and positioning in the marketplace are similar, but serve different purposes. "Branding is about differentiating," says Scheibel. "If you don't have some type of brand or compelling story about your unique value proposition, you're leveling the playing field. Your customers will think all molders or moldmakers are the same, so all you have to compete on is price." For instance, a molder's brand can include press tonnage, type of materials being run, or the products molded, adds Ball.

    Positioning in the marketplace answers the question, "What is the space I want to occupy in the minds of my target audience?" Scheibel explains.

    Ball says that a company's marketing plan is then built on company goals and objectives for getting the message to that target audience in a consistent way. "An integrated marketing plan shouts this message in everything considered controllable: public relations, every piece of paper that goes out the door, how your back lot looks, how the landscaping looks, how employees communicate."

    It's really about inventing the company rather than "reinventing"—the new buzzword. Scheibel and Ball both agree that for most molding companies, defining who they are or what they do best is a challenge. "Decide what it is you want to be, and then how to get there," says Ball.

    However, it's important to keep in mind that branding doesn't mean that you can't change or evolve as a company, Scheibel notes. "Your brand reputation can grow with you if you position your company correctly."

    Contact information
    Plastikon Industries Inc., Hayward, CA
    Susan Ball; (510) 400-1124
    www.plastikon.com
    [email protected]

    Scheibel Halaska, Milwaukee, WI
    Mary Scheibel; (414) 272-6898
    [email protected]