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September 1, 2003

11 Min Read
IMM's Plant Tour: Matching the technology to the market that pays

Medical Rubber’s 40 molding machines are all from Arburg and most are set up with LSR mixing units. The new factory has room for growth in this Class 100,000 cleanroom space.

Medical Rubber in Hörby, Sweden began in 1973 as a one-person general purpose rubber molding operation then known as Expaco. Business increased quickly and the company moved to a family-owned farm in 1979. The farm buildings rapidly became industrial and more space was needed again. Today, the farm site, which is still an active molding-based production center, is visible from the modern purpose-built facility opened in 1999 about a mile away. But it was around the time of the move to the farm that a number of factors converged to create today’s Medical Rubber.

Formed with an Inside-Outside Focus

The company, which had been using compression-set rubber molding technology, took a major step into its future by acquiring injection machines. In the same time period, medical sector business was increasing rapidly, particularly for technically demanding small components, and liquid injection molding (LIM) of liquid silicone rubber (LSR) was emerging on the scene. LIM was then still quite undeveloped, but the Persson family, which owns and runs the business, saw the potential. For starters, the company was renamed Medical Rubber.

This bipartite focus—LIM/LSR molding and serving the medical industry—became a unified driving force that has brought business growth averaging more than 20 percent per year. The direction has not changed, and in fact today is stronger than ever. Medical Rubber also serves industries such as food and electronics, but only those applications needing the technology and quality level of medical LSR components. Non-LSR molding is about 5 percent of the business.

Technology From the Ground up

Getting started in LSR molding around 1980 was a lot different from starting up today. MR’s general manager Mai Persson calls it pioneering, and anyone who knows the business would agree. Medical Rubber found support on the materials side from Bayer, Dow Corning, Nusil, and Wacker, which, not surprisingly, are still the company’s material suppliers. Machinery was a somewhat different story. No one was selling LSR molding machines as such in those days. Medical Rubber found molding technology it liked from Arburg, as well as support for modifications, particularly in screw design, to create LSR-specific systems.

The variety of the silicone parts molded for medical applications is broad. Just left of the white rectangle are some of the metal insert parts made in the vertical machine on p. 112.

Most molding machines are automated with picking and handling units designed by Medical Rubber. Nonautomated machines are a strategic choice for efficient short-run work.


Medical Rubber, Hörby, Sweden

Square footage: 7000 sq m (75,000 sq ft)
Annual sales: 80 million kroners ($10 million)
Markets served: Primarily medical, also food and electronics; 70 percent export
Materials processed: More than 90 percent LSR, plus TPE and thermoplastics
No. of employees: 130
Shifts worked: Five shifts, 24/7
Molding machines: 40 Arburgs, 25 to 150 metric tons
Molding technology: LIM, cleanroom Class 10,000 or 100,000, insert and overmolding
Secondary operations: Cleanroom assembly
Internal moldmaking: No
Quality: ISO 9002, EN 46002, FDA inspected

Mai Persson, general manager of Medical Rubber since 1985, was recently recognized for her business achievement and social involvement by receiving the prestigious Veuve Clicquot Business Woman of the Year Award for Sweden.

The relationship with Arburg has also passed the test of time, owing as much to the machine maker’s commitment to developing LSR technology as to what Persson describes as proactive service and support. Arburg and Medical Rubber, she says, learned LIM technology together as working partners, and Arburg is among those who refer to Medical Rubber as an LSR pioneer. Persson says Arburg also recognizes that MR’s machines need to be up and running, and they do whatever it takes to achieve that—often without being asked.

Each of Medical Rubber’s 40 injection systems is from Arburg, including four new Allrounders installed this year. Arburg’s LSR technology offerings now include specially designed cylinders, compression-free dosing screws, needle shutoff nozzles, and process-specific machine controls managing two-component mixing units and blowout systems as seamlessly as they manage the injection process itself. Persson says that since older units continue to work precisely, new machines are almost all additions, not replacements.

Make Changes; Stay with the Plan

Medical Rubber has from its beginning seen itself as a supplier of custom-made components that begin with part drawings from clients—and that still dominates its business. However, as its expertise grew it began offering clients a collaborative design service, and many now use it. The reason is simple: MR has become more knowledgeable about LIM technology than its clients want or need to be. The design service applies that expertise to helping clients develop components that meet performance specs and can be efficiently produced. Roberto Comisso, an area sales manager for MR who guided IMM through the operation, refers to that service as “the optimum cost containment strategy.”

Assembly work, here in the Class 10,000 cleanroom in Medical Rubber’s newer factory, is an important value-added service to clients.

This vertical machine used for insert molding over metal may be automated thanks to increased production of the principal application.

These machines in the new factory are outside the Class 10,000 cleanrooms in Class 100,000 areas. A tube takes parts through the wall and moves clean air into the mold area.

Although Medical Rubber saw itself as a component supplier, its staff developed a number of ideas for original medical products during the early 1980s. To avoid competing with its customers, the Persson family formed Atos Medical in 1986 to develop and market those products. Faced with the high capital needs of medical product development and testing, MR sold partial ownership to a multinational company to form a joint venture and Atos was relocated in 1991 to a facility on the other side of Hörby. Six years ago the two companies officially separated. The Persson family bought back all of Medical Rubber and Atos became a division of Perbio Science and a customer of Medical Rubber. MR, meanwhile, never wavered from its two-part strategy.

Molding Inside and Outside the Cleanroom

The original farm buildings Medical Rubber occupied in 1979 are today producing primarily long-term implants of various types in a Class 10,000 cleanroom, within which are the LSR machines in a walled-off section. Comisso says there is no difficulty maintaining Class 10,000 limits there or in the area used for the thorough quality inspections and any secondary work. The area includes a Class 1000 area under a laminar-airflow hood where medical catheters are produced.

The new factory, which was originally designed for industrial use, was changed to cleanroom production in response to continuing medical market growth. It includes a Class 10,000 cleanroom at its center; however, this one is for assembly only, not molding. The presses are in a Class 100,000 cleanroom area that surrounds the assembly cleanroom. Parts are conveyed into the assembly area directly from the molding machines through a tube. That tube is within another tube carrying air from the Class 10,000 cleanroom to the clamp area of the molding machine for increased cleanliness.

Quality + Technology = Added Value

Medical Rubber has been certified to ISO 9002 standards since late 1994 and has EN 46002 certification. The FDA has inspected the assembly area for conformance. Comisso says medical clients now assume you are ISO certified if you come looking for technically demanding applications. The advantages of LSR, particularly in medical applications, and the need for processing expertise mean Medical Rubber can concentrate on the complicated applications where it can add value. MR has Flow Groups of experienced operators and inspectors who take full responsibility for an entire production process—in particular, client applications, from planning to final inspection.

A molded part that is a price-driven commodity does not fit MR’s business model. Quality-driven, technically demanding production is the house specialty. There is more margin there, says Comisso, but the price has to fit the application. Medical companies, he adds, are very budget-conscious.

Many people feel that a reputation for high price has restrained the growth of LSR. Comisso says the cost of a kilogram or pound of LSR material is high compared to most plastic materials, but that is offset by its low density and the resulting high number of parts per pound. In addition, many of Medical Rubber’s molds, especially those with high cavitation, use cold runner technology to eliminate sprue and runner waste. Medical Rubber’s molds have as many as 64 cavities. Add to the cold runners a mold design that eliminates silicone’s traditional tendency to flash, and Comisso says material cost per finished part is often a pleasant surprise for clients new to LSR.

Medical Rubber has a mold maintenance and repair shop but currently does not make its own molds. Most come from specialist firms nearby in Sweden and a smaller percentage from Austria. Mold quality must be excellent if it is to run virtually flash free. Given LSR’s very low viscosity entering the mold, flash can occur in mold gaps as small as .01 to .02 mm. Ideal tolerances are less than .01 mm. If and when molds are made in-house, which is under consideration, the emphasis will be on simpler molds that are time sensitive. Complex molds would still be purchased to capitalize on the skill of the suppliers with whom MR has excellent long-term collaborative relations.

Supporting Technology, Services

Most of Medical Rubber’s molding machines are automated. Vacuum parts removal systems developed in-house and built by local companies solve the problem of LSR parts adhering strongly to mold cavity surfaces. However, one notices that quite a few of the machines are not automated, including a vertical Arburg machine molding silicone over a metal insert.

MR’s original Class 10,000 cleanroom specializes in long-term implantable devices.

Among the quality systems is this optical video probe with 200X magnification that allows detection of any flash or other defects.

The company’s design of the final inspection area in its Class 100,000 cleanroom includes benches specifically designed for the work being done.

The lack of automation is, in fact, an integral part of MR’s client service strategy. Many LSR runs are as small as 10,000 parts, or even less. Building an automation system for such a run makes no sense, says Comisso, but neither does turning away every short-run job. Economic feasibility is important, but how do you serve long-term clients with technically difficult but low-volume products? Answer: by hand, with highly skilled operators.

Comisso says the minimum feasible quantity is dependent on the part itself and how critical it is to the client. And over time, things can change: The metal insert part on the vertical machine has been increasing in volume, so MR is studying how to automate insert placement and part removal. The study includes engineering and economics; besides robotics, automation may require a new mold. The important thing, he says, is to offer the client a full range of the best choices.

Doing All It Takes

Medical Rubber is still primarily a component manufacturer, but it has been doing assembly work needed by clients for years. The new plant’s additional cleanroom assembly space is busy, as is that of the older facility. Specially designed assembly benches and equipment facilitate the work.

Medical Rubber’s concentration on LSR for medical applications makes it unique in Sweden, and as Mai Persson notes, there are very few companies in Europe or anywhere else with the facilities and expertise to meet the LSR demands of medical companies. Recent growth has averaged about 20 percent per year even given the poor recent economy. Growth in the past two years has exceeded projections, and business is coming from markets in Europe, North America, and even Asia.

This has put pressure on the company to find and train good people. Hörby is a small town. More importantly, there is no school anywhere teaching LSR molding. Therefore, Medical Rubber is putting even more effort than normal into training. In general, MR employees are long term, which is a good thing given the continuing growth of LSR in medical applications. The company looks to remain family owned. Mai Persson’s son Mattias is marketing manager and her daughter Hannah is an area sales manager.

Contact information
Medical Rubber, Hörby, Sweden
Roberto Comisso; +46 (415) 197 00

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