Fully tested compatibility of a wide range of materials and component tolerances.
A reliable TIER ONE supplier, from purchasing and manufacturing to assembly and delivery.
Unparalleled expertise in plastic injection moulding, liquid silicone injection moulding and system assembly.

Mixer housing for anaesthesia equipment – for the mechanical ventilation of infants, children and adults

There can be no compromises made when it comes to the mechanical ventilation of infants, children and adults. Uncompromising quality from GPE allows you to breathe a sigh of relief.

There is no such thing as only a bit of ventilation. This is exactly why the requirements that anaesthesia systems must meet are so extraordinarily high. GPE fulfils them. Even in emergencies – like now, when customer demand is skyrocketing as a result of the ongoing pandemic. With our mixer housing, we deliver a solution that extends from purchasing through design, highly complex plastic and silicone injection moulded parts to fully inspected module assembly. The finished products are delivered daily in returnable packages of 6 units directly to the customer’s production line in what is known as the ‘ship to line’ logistics model. As such, everyone can breathe a sigh of relief – whether on their own or with the help of a ventilator.

The Task

During the development of a new anaesthesia machine, the customer commissioned GPE to advise it on and realise a manufacturing concept and a technology solution for the machine’s gas mixer. In short, the project involved high-precision plastic injection moulding with a focus on a component design optimised for injection moulded plastic, taking into account all of the technical requirements and specifications – including supplier management, mould concepts, component assembly, testing, customer-specific packaging solutions and logistics services. In other words, a complete solution.

The Challenges

As extensive the tasks, so too were the challenges to be overcome. This began with the choice of materials. Since the AS ASM mixer housing comes into direct contact with anaesthetics from the anaesthesia workstation such as halothane, enflurane, isoflurane, sevoflurane and desflurane, the high-performance plastics used had to meet the most stringent requirements with respect to their mechanical, thermal and electrical properties, as well as chemical resistance. This alone required extremely strict quality assurance agreements with raw material suppliers. GPE was required to rigorously test the mechanical and flow properties of each batch of material, which needed to withstand extremely high processing temperatures of around 260 °C. The customer’s requirements for the raw materials also included hydrolysis resistance, improved impact strength and optimised heat resistance. The raw materials had to be antistatic/conductive (ESD) and flame-retardant in accordance with UL 94, as well as achieving fire protection class V-0. Further requirements included the use of laser batch coding, weight optimisation through low density, etc.

The requirements that the injection moulds had to meet were no less demanding. In this context, it was necessary to consider in advance all of the possible factors that might have an effect on the design of the tools. GPE assumed responsibility for designing the nine injection moulds for the functional components, enabling the compatibility of the items both individually and with each other to be achieved very quickly. In the process, GPE ensured that the extremely stringent customer requirements applicable to the various individual injection moulded parts with respect to tolerances, distortion, flatness and parallelism were fully met.

The Solution and The Added Value

Design and Production

GPE’s solution was based on the use of four materials – including 30% glass fibre reinforced PA12, liquid silicone and steel. The high-performance plastics are abrasive due to their high filler content. The geometries of the gas channel component act like undercuts that cause the components to effectively stick to the mould. The melt remained within the temperature ranges specified by the manufacturer during processing. When designing the tool, it was essential that the sprues were not positioned in the later welding and sealing areas. We therefore developed a special cooling device in which the gas channel injection-moulded parts are clamped, thus reducing distortion and maximising plane-parallelism by means of air cooling – resulting in fewer rejects during subsequent component assembly.

The production technologies utilised comprised plastic injection moulding, liquid silicone injection moulding under class 8 clean room conditions according to DIN EN ISO 14644-1, high-speed machining, laser marking, laser welding, inductive hot embedding of threaded bushes, assembly, complete testing and packaging in a class 9 clean room according to DIN EN ISO 14644-1.

An overview of the requirements for the parts provides an insight into how accurate and precise production needs to be:

  • Mould flash 0+0.1
  • Mould mismatch 0+0.1
  • Flatness < 0.10 mm
  • Plane parallelism < 0.60 mm
  • Tolerances, in some cases < 0.10 mm
  • Line profile tolerance 0.2 mm
  • Stress cracking resistance
  • Impermissible, open-pored surface structures, voids or vacuum voids
  • Due to the complex geometry, some of the dimensional requirements, such as flatness and plane-parallelism, can only be achieved by means of high-speed machining
  • Burst pressure resistance of 14 bar to 40 bar

Module Assembly

The gas mixer used in the anaesthesia machine system consists of 20 different components. All of the individual parts must meet the highest standards of quality before they can even be fitted into the final assembly. For this reason, every gas mixer is subjected to a full mechanical, optical and pneumatic functional check using customer-specific testing equipment. Each inspected gas mixer is laser-marked with UDI codes using order-related serial and production numbers to ensure that each and every functional assembly of the entire anaesthesia machine system is fully traceable.

Supply Chain Management

Supplier management for all of the assembly’s components, right down to the packaging material, is fully handled by GPE. Sealing and packaging the parts in antistatic ESD PE pouches, including label printing with a LOT no. and Data Matrix code, is carried out under class 9 clean room conditions to DIN EN ISO 14644-1. Complete documentation of incoming purchased parts and outgoing deliveries of the gas mixer is stored for each batch by GPE using a CAQ system, including test certificates.

The Application

Less work and peace of mind. This is the shortest summary of the benefits and added value provided by GPE with respect to the AS ASM mixer housing component. The customer was able to fully delegate to GPE the task of harmonising the plastic and silicone parts with each other – as such, the customer no longer needed to coordinate with several different suppliers.

Furthermore, GPE guarantees maximum quality with regard to the system assembly of the AS ASM mixer housing component, because in this case the most important aspect is the perfect interaction of the wide variety of materials and component tolerances in each drawing. If a relevant functional test dimension is not accurate in only a single component, the complete assembly of the AS ASM mixer housing may fail the final test. Our highly complex subassembly production, from the raw material to the fully tested and documented assembly, as well as the UDI coding of the various components which enables traceability back to the raw material for each batch, stands for uncompromising reliability.

Together with our customer, we here at GPE developed and defined carefully engineered and stable manufacturing processes. We organised and coordinated the management of suppliers of purchased parts, including smart scheduling. Thus, our customer receives its AS ASM mixer housings – in a forecast-driven manner and according to its needs – in returnable packages of 6 units daily, delivered directly to the production line every day in what is known as the ‘ship to line’ logistics model. It couldn’t be any easier or more reliable. As such, everyone can breathe a sigh of relief – whether on their own or with the help of a ventilator.

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