Medical technology injection moulding at the highest level

Fresenius Medical Care is the world market leader in the treatment of kidney disease. Products from the globally active company are involved in every second dialysis worldwide. The French plant in L'Arbesle produces 36 million blood wash cartridges for dialysis per year. The injection moulding production was originally outsourced and was brought back to the plant a few years ago - with a doubling of the number of machines in 2018. Thibaud Robin-Rivoire, Technical Director of the plant, provides the reason for this decision: "With in-house production, we are more flexible. We can very easily adapt the products to our customers' requirements, especially as they are always changing."

The requirements for injection moulding of medical technology products are naturally particularly high. Production usually takes place in a clean room to avoid contamination of the plastic parts. The injection moulding machine must work absolutely cleanly - for example through encapsulated lubrication of the toggle lever. In addition, a 100 % reliable function of the parts must be ensured, since in an emergency a life depends on it. This is fulfilled with exact process control, quality control and complete documentation in production.

Six tools are active for the production of the blood wash cartridges. Different diameters and lengths of the cylinders result in a total of five different sizes of FX dialysers - to suit the body size and weight of the patients.

The specifications for the new injection moulding machines included the following typical features for medical technology injection moulding:

• Absolute cleanliness and highest precision due to clean room production and zero-defect strategy

• High dimensional accuracy across all cavities of the multiple moulds due to subsequent, fully automatic assembly of the injection moulded parts

• Consistent, maximum product quality in 24/7 continuous operation

• Simple and quick execution of regular tool changes

• Low unit costs in order to produce competitively, even for price-sensitive markets

The cartridges are made of polypropylene, which has a high shrinkage ratio. Ensuring the dimensional accuracy of the individual parts is therefore a challenge.

"We have to be able to rely on the reproducibility of the machines, we need maximum precision and absolute cleanliness," says Laurent Brancherau, Head of the Injection Moulding Department at Fresenius Medical Care. Fresenius contacted ENGEL with these requirements in mind.

ENGEL identified the all-electric e-motion injection moulding machine as a suitable basis for the requirements. It is the versatile high-performance variant among ENGEL's electric injection moulding machines. Thanks to its extensive range of options, it can be specifically adapted to challenging applications in medical technology injection moulding. Its dynamic servo-electric drives ensure the necessary precision and speed. Its high energy efficiency ensures low running costs. A particular advantage: the customer’s moulds with their electrically driven core pulls were already designed for use on an all-electric injection moulding machine. The intuitive, simple operability of the CC300 control system was another plus point.

"The CC300's easy navigation helps us achieve high process stability. In the end, this leads to better quality." (Eric Biguet, machine setter at Fresenius Medical Care)

Fresenius Medical Care opted for the e-motion in the 2200 kN clamping force class. With this size, all applications can be covered. ENGEL customised the machine to meet the customer's requirements. One example of this: the e-flomo electronic temperature control water distributor was mounted outside the mould area in this case - contrary to common practice - so that the differently sized moulds can be clamped easily and quickly.

The requirements defined in the specifications were solved as follows:

• Absolute cleanliness and highest precision

  The Cleanroom package of the e-motion is designed for medical technology injection moulding up to cleanroom class 7. All potential sources of dust or contamination are sealed. An encapsulated toggle lever is already installed in the e-motion as standard. The servo-electric drives on all axes enable precise control of all movements - shot by shot.

• High dimensional accuracy across all cavities of the multiple moulds

  The e-motion's solid clamping platens evenly dissipate spread the forces that occur, thus ensuring homogeneous clamping force distribution.

• Consistent, maximum product quality in 24/7 continuous operation

  The e-motion is designed as a high-performance machine for maximum continuous loads. Its field of application is highly automated production in continuous operation with particularly short cycle times. Even under challenging production conditions, it reliably delivers stable results. In the case study shown here, random checks every four hours are sufficient.

• Simple and quick execution of regular tool changes

  The mould area was designed free of peripheral units. This enables easy installation and removal of the injection moulds. The necessary free space was already achieved with the standard version of the e-motion 220. An optional wide-platen version with larger clamping platens and tie bar distances was not necessary.

• Low unit costs

  The short dry cycle time and high energy efficiency of the all-electric e-motion injection moulding machine ensure high output at low running costs. The customer was able to achieve a machine utilisation of over 90 %. This is directly reflected in the unit costs. The efficient temperature control system with ENGEL's digital assistance programme iQ flow control contributes to further savings in energy costs. Fresenius Medical Care can thus succeed with its products even in price-sensitive markets.