In the production of plastic components for dialysis products in the cleanroom, maximum precision is required for every cycle. The task is to combine precision with process stability and cost effectiveness. Fresenius Medical Care masters this challenge with all-electric high-performance injection molding machines by ENGEL.
All-electric ENGEL e-motion meets strictest requirements at Fresenius Medical Care
Because it's a matter of life
The lives of two and a half million people with chronic kidney failure depend on what look like inconspicuous plastic cylinders at first glance: dialyzers are the central element in dialysis (“artificial kidney”) machines. On closer inspection, the FX-class series dialysis cartridges by Fresenius Medical Care are highly sophisticated. They contain up to 20,000 hollow fibers as wide as a hair with microscopic pores, through which toxins, urea, excess salts and water are removed from the blood during hemodialysis. The process takes four hours. The patients need to be connected to the machine three times a week.
Each FX-class filter cartridge needs six thermoplastic components, which Fresenius Medical Care SMAD injection molds in L'Arbresle, about 20 kilometers northwest of Lyon. The components include the transparent cylindrical housing and the blue caps that seal the cylinder with the hollow fiber bundle at the top and bottom, and house the connections for the dialysis fluids.
According to its own statements, Fresenius Medical Care is the world market leader in the treatment of kidney disease. ”At least one Fresenius Medical Care product is involved in every second dialysis performed worldwide,” as project manager, Alain Philibert, explains during a tour of the production plant. ”Currently, we produce 36 million cartridges a year here in France.”
L’Arbresle is one of 44 production plants worldwide and the only one in France. The plant has grown steadily, emerging from SMAD, a company which was acquired by Fresenius. SMAD has remained as the location name. More than 500 people work at SMAD – serving patients.
”We are very close to our customers here,” as technical director Thibaud Robin-Rivoire clarifies. Posters with pictures of everyday life in dialysis centers are on display in all the production areas, showing the people whose lives depend on the products manufactured in L'Arbresle. The top priority is uncompromising quality, and it was also a quality-driven decision to exclusively equip the location with all-electric injection molding machines from ENGEL's high-performance e-motion series.
In 2014, injection molding production, which had been outsourced, was brought back in-house, seeing significant expansion in 2018. ”The number of injection molding machines has doubled,” says Robin-Rivoire. Today, 26 e-motion injection molding machines – each with a clamping force of 2,200 kN – are running in the cleanroom. They all operate 24/7 with a utilization of well over 90 percent. ”We have to be able to rely on the machines' repeatability, and we need maximum precision and absolute cleanliness,” says Laurent Branchereau, head of the injection molding shop at the plant, explaining the choice of machines. Every four hours, random samples of the parts are visually inspected and the critical dimensions are measured.
The cylindrical filter housings are particularly demanding. They are injection molded from polypropylene in a 4-cavity mold. The wall thickness is 1.5 mm throughout, but the filigree structures at the ends, each with a circular undercut, require a sophisticated injection profile to be completely filled. Injection takes place from two sides at the center of the cylinder. There are two core pulls for each cavity that move out to the left and right respectively for part removal. ”The e-motion machines ensure high dimensional accuracy across all cavities,” as Branchereau points out. ”This is all the more important because we assemble the cartridges in a fully automated process.”
The material poses a further challenge, because PP is prone to a significant degree of shrinkage. On the other hand, it offers benefits in other areas. While filter housings are often produced from polycarbonate, Fresenius Medical Care deliberately chose polypropylene because it is significantly lighter and therefore boosts efficiency in both logistics and waste management.
”In-house production makes us more flexible,” as Robin-Rivoire explains. ”We can very easily adapt products to our customers' requirements, especially since these requirements regularly change.” For example, pricing pressure is also growing for dialysis products. ”The new markets in particular are price-sensitive, ”as Philibert reports. Optimizing the cycle time is an important factor here, and this was also an argument in favor of the high-performance machines from the e-motion series. The all-electric drives ensure very short injection times. The mold design makes a further contribution. All core pulls are electrically driven and can start moving at the same time as the machine's clamp is opening.
Six molds, for three different cylinder diameters, are currently used in cylinder production at L'Arbresle. In total, the FX dialyzers are available in five sizes. The version used depends on the patients' size and weight. A mold change is scheduled at least once a week. This was already taken into account in the design of the machines. The e-flomo electronic temperature control water manifold systems, for example, were installed outside the mold area to allow flexible mounting of different sized molds. Each mold has a different number of cooling circuits. ”e-flomo helps us respond quickly if the flow falters in a circuit,” says Branchereau. ”That gives us a good safety margin, especially at night when there are fewer machine operators on the production floor.”
Focusing on one type of machine also contributes to the goal of maximum production stability. ”It makes things easier for the machine operators and maintenance staff,” says Branchereau. ”The CC300 control unit of the ENGEL machines with its large display is intuitive to operate,” Eric Biguet points out. Biguet is a set-up technician and responsible for smooth production operations. He used to work with ENGEL machines for his previous employer and is familiar with all control unit generations. ”The CC300's easy navigation helps us achieve great process stability. And at the end of the day, that gives us better quality.”
”Our goal is to leverage the quality potential offered by the ENGEL machines to an even greater extent in the future,” Robin-Rivoire emphasizes. ”ENGEL gives us excellent support here. ENGEL also customizes the machines to meet highly individualized requirements. That's what characterizes our collaboration with ENGEL.” Among other things, digital solutions, such as the iQ smart assistance systems from the inject 4.0 program, are currently being evaluated. ”iQ clamp control is particularly interesting for us,” says Philibert citing an example. The smart assistance system determines the optimum clamping force for the injection molding process in question. In most cases, the optimum clamping force is lower than the value set manually.
Clamping force correction then not only improves quality consistency, but also saves energy. The trend toward greater sustainability has long since arrived in medical technology, too, and not just following the rapid rise in energy prices.
Energy efficiency, but also material efficiency, is a focus of continuous product development at Fresenius. You can see one example of this by following the path of freshly injection molded dialyzer housings. After a short interim storage period, they are filled with the hollow fibers, which are also produced on-site, and tightly sealed with yellow lids made of polyurethane. It is only after steam sterilization that the yellow lids are replaced by functional closures in blue polypropylene. The polyurethane lids are disposable parts, and that is precisely what is due to change. ”We have developed new closures with a core made of glass-fiber-reinforced polypropylene,” Alain Philibert reports. ”They are so robust that we can reuse them up to 50 times.”
Do you have an opinion about this story? Do you have some thoughts you'd like to share with our readers? Plastics News would love to hear from you. Email your letter to Editor at [email protected]