Medical Device Link.

OUTSOURCING GUIDE

Medical moulding has grown more sophisticated over the last decade. It is time to take a fresh look at how plastics technology has changed relative to measurement, machines, methods, moulds, materials and “Mother Nature.” The best medical moulders understand these elements and have leveraged them to improve their business systems and renew their company culture.

Measurement. Section 7.1 of ISO 9001-2000 refers to the planning process as “product realisation.” The spirit of the standard demands that the organisation plan and develop the processes needed for product realisation and that it be consistent with the requirements of all processes in a quality management system.

Most moulders use inspection data, capability studies, and traditional statistical tools to meet this standard. Some forward thinkers have developed a comprehensive product realisation process that includes risk assessment, process validation, and documented protocols to ensure consistent performance to product specifications and standards.

Window studies, designs of experiment, and other tools are frequently employed to establish process extremes. Scientific moulding requires that the major process categories—time, temperature, pressure and cooling—be defined. Leading moulders have leveraged the standard as a vehicle to deliver an improved process and to comply with regulatory validation requirements.

The critical ingredients needed to build a comprehensive validation protocol demand finite studies to accurately define the process. The validation of the mould is achieved by performing studies that define the optimal process unique to each mould. Moulders who embrace the standard will use the following studies as analytical tools to define process variables: mould flow, mould cooling, water flow, resin viscosity curve, gate seal, balance of fill analysis and pressure drop segmentation. Taken together, these studies define the characteristics of the process for each mould. They establish a unique fingerprint—a genetic profile, of sorts—of the moulded part.

Machines. Moulding equipment has changed dramatically over the years. What once was considered extraordinary is today‘s baseline. Computer controllers enable moulding machines to react almost instantaneously to events. They allow the transmission and processing of data in real time.

Digitally controlled electric motors have replaced hydraulic pumps to deliver near-perfect repeatability. Some believe a blending of hydraulic and electric technologies in hybrid machines will be the long-term solution. Because of their accuracy and energy savings, electric machines and hybrids will dominate our future.

Automation, which once was viewed simply as a means to replace machine operators, has become a critical device for providing a consistent process. Pneumatic pick-and-place robots have been displaced by precise servomotor-driven multi-axis robots. Once expected only to remove parts from the mould, they have become integrated into an automation cell that can perform inspection, assembly and packaging.

Methods. The advent of scientific moulding caused a revolution within the moulding community. ”Old school” moulders “tweaked knobs” to produce acceptable parts. They had no regard for how these adjustments affected other characteristics and lacked an understanding of the relationship between the part and the process.

John Bozzelli, a founding father of scientific moulding, challenged the moulding community to study the cause and effect of the variables, and to optimise the process using scientific principles. The freedom of random process adjustments was replaced by process studies to define control limits. This prompted a revolution between “old school” processors and followers of the emerging discipline of scienctific moulding.

The advent of precision electric moulding machines, computer controllers and scientific moulding methods helped to establish a process that can be documented and repeated every time a mould arrives in a machine. A universal process was developed that made it possible to run the same mould in an equivalent machine with the confidence of delivering an identical part.

Moulds. The accuracy of electric machines complemented by scientific methods allows the mould to produce a part that can nearly replicate its precision. Over the almost 100-year history of plastic processing, a tension has played out between mould makers and those performing the moulding. Machine repeatability and scientific processing methods have left little room for anything less than an exceptionally well-crafted mould with excellent function and tight tolerances. In the hands of a scientific moulder, the mould remains the key to success.

Moulds are becoming more sophisticated. Rod Groleau of RJG Inc. invented and trademarked Decoupled Moulding and introduced the use of pressure sensors in the mould to provide real-time data. By connecting this feedback loop to a hot-runner system and valve gates that open and close, an intelligent system is created. Sequential valve gating results in a more complicated mould, but it provides the process engineer with an extraordinary degree of control.

Predicting a material’s shrink rate based on part geometry is among the moulder’s most difficult tasks.

Materials. One of a moulder’s most difficult tasks is specifying a material’s shrink rate. The material supplier provides a range, but it is incumbent upon the moulder to predict the differential shrink rate caused by a part’s unique geometry.

The mould maker can machine the critical cavity and core details to within a few microns. The moulder must predict the shrink rate of the material so the steel can be machined to compensate for the amount that the material shrinks away from the steel while it is cooling. Bear in mind that polycarbonate shrinks at approximately 0.006 in. per inch, whereas acetal shrinks approximately 0.018 in. per inch.

A sophisticated mould maker will machine the steel to nearly perfect dimensions. A miscalculation in estimating the shrink rate, however, could cause the moulded parts to be skewed on either side of the nominal dimensional value. Forcing the process can compensate for an over- or underestimation of the shrink rate, but this violates the fundamentals of a scientific method.

Software models are available to predict material flow, cooling and shrink rates. When used by an experienced process engineer, the software can help prevent costly mould and part design issues.

Material viscosity remains an issue between the material producer and moulders. The viscosity of the resin will vary within a stated range. Scientific moulding principles can significantly reduce the impact of this material variability.

Mother Nature. Sustainable manufacturing has become the new buzz term for aggressive marketers, but most medical moulders have quietly adopted Earth-friendly techniques without drawing attention to their efforts.

High-cavitation moulds coupled with hot-runner systems eliminate waste and, in some cases, reduce moulding cycle times. Moulders who generate plastic waste are grinding parts and runners and releasing the material to nonmedical applications for which virgin material is not required.

Electric moulding machines consume approximately 50% less power than their hydraulic counterparts. Energy savings and the elimination of hydraulic oil have contributed to cleaner moulding facilities and the elimination of an environmental contaminant.

Most leading moulders embraced RoHS requirements and are moving aggressively to meet the new REACH initiatives. Industry leaders are committed to minimising the use of toxic chemicals and are seeking alternative substances for use on the manufacturing floor.

Sourcing suppliers. So, now you may be thinking: What is so difficult about sourcing a moulded part to 0.10 mm tolerance on 100% of all the components produced? The superficial answer lies in an assessment of the system’s capability. But the real value of a moulding partner lies in the care and commitment of the people who operate the system. Serious consideration and emphasis needs to be placed on the people who make up the company and form its culture.

The assumption is that you have developed a robust part design and are ready to build a mould, validate the process, and begin production. Your intention is to determine if the moulder has a history of managing parts of like size, complexity and tolerance, and in equivalent quantities.

We have determined that measurement, machine, materials, methods, moulds and Mother Nature are the essential ingredients critical to our success. To apply the stated principles to the real world, we must recognise the diversity of medical product manufacturing and the need for excellence in each of the noted disciplines. What is common to all medical products is the demand for strict adherence to comprehensive quality, development and validation processes as vehicles to eliminate risk.

It is nearly as much work to qualify and validate a mould that will produce 1000 parts as it is a mould that will produce one million parts. The ideal solution is to develop a full-service partner who can deliver on both counts. In addition, systematic preventive mould maintenance is critical to ensure mould performance and the reliability of the moulding process. Even if you have relatively low volume requirements or low-cavitation moulds, you will need the same system dictated by high-volume, high-cavitation moulds.

Medical moulding does not always require a cleanroom—that is left to the discretion of the OEM. Companies with experience serving medical manufacturers routinely apply Current Good Manufacturing Practices and understand the requirements of moving goods from one clean controlled environment to another. Regulatory authorities are making it more critical for OEMs to partner with companies that have integrity, capability and the right culture. The common denominator demanded by all medical products is strict adherence to comprehensive quality and developmental systems.

The ideal medical moulder has embraced scientific moulding principles and has a comprehensive product realisation process. Electric and hybrid moulding machines, computer controlled processors, automation and moulds built to micron-level tolerances are your benchmarks for performance. Ultimately, you must determine if the moulder has the right systems by peering deeply into the organisation and verifying that it meets your requirements. The ideal partner will have a culture that exhibits discipline and whose company is populated by caring people who breathe life into those systems.

About the Author

Chuck Brewer III
CEO of C. Brewer Co. (Anaheim, CA, USA; www.cbrewer.com), Chuck Brewer III was mentored by his family of metal craftsmen, who pioneered the birth of the plastic moulding and mould building industry in Southern California. In the 1980s, he was elected to the Society of Plastics Engineers Board of Directors, Southern California section, ultimately serving as President. He chaired a RETEC conference and was vice chairman of SPE’s prestigious ANTEC technical conference in Los Angeles. His hands-on experience accented by a formal education and, most importantly, more than 40 years working in the moulding industry gives him the unique qualifications to speak with confidence about plastic moulding.