Modular cleanrooms supporting process control for medical plastics

Jeni Thomas, content and communications leader at Connect 2 Cleanrooms (C2C), and Alisdair Watson, MD at Optimold Limited, explain how modular cleanrooms support manufacturing process control for medical plastics.

There are certain challenges that plastics manufacturers face when producing moulded parts for medical devices. Controlling air quality with a modular cleanroom protects the production of medical plastics. 

The injection moulding process—in particular the material conveying equipment—naturally creates a degree of particulate contamination. When moulded parts are removed from the tool, the type of polymer and the process can also generate static, even with the use of an antistatic device. When combined, the particulate and static can cause problems for manufacturers who have tight AQL (Acceptable Quality Limit) sampling requirements. This is why the manufacture of medical devices must be performed within ISO 14644-1:2015 Class 5 to Class 8 cleanrooms. 

Cleanrooms and processes aligned to control contamination

The way that the governing ISO standard looks at compliance is by minimising the introduction, generation, and retention of particles. This can only be achieved through a partnership of cleanrooms and processes. 

Cleanrooms stop the introduction of contamination through HEPA filtration. Controlling the generation of contamination is then down to organisations’ SOPs, protocols, and process controls. The responsibility of controlling the retention of particles comes back to cleanrooms again as they effectively flush that facility of contamination with appropriate air change rates.

Optimold Limited, the sister company to mould manufacturer Microsystems (UK) Limited, is a contract manufacturer producing injection moulded components for medical devices, such as auto-injectors, asthma inhalers, drug delivery and blood diagnostics for both hospital and laboratory use. Over the past decade, C2C has supported Optimold with modular cleanrooms to facilitate growth in the medical device market.

Starting clean production

To stay competitive, companies need to be able to incrementally grow their cleanroom offering in line with the growth of the company.

When Optimold won its first contract for medical device parts back in 2011, one machine out of the five they had at the time needed to be enclosed in an ISO Class 8 cleanroom. Converting the entire room which housed these machines into a cleanroom and encapsulating the whole area into a single level of control would have required a huge investment. The higher overheads would inevitably have driven up the cost of the parts that didn’t require cleanroom production.

The solution was simple. C2C installed a localised cleanroom to house an individual machine. As contracts grow or new work is won, machines can be upgraded with a cleanroom accordingly and, as freestanding units, they can easily be retrofitted to moulding machines.

Optimold now has 13 injection moulding machines, of which seven are enclosed in modular cleanrooms. The modular cleanrooms create a clean environment to prevent contamination issues and, when combined with the controls put in place, they manage contamination well within the requirements of customers’ AQL criteria.

Energy efficiency

Modular cleanrooms give flexibility within the production environment, whilst still providing the customer with a quality product. 

Energy consumption in the manufacturing sector represents a huge proportion of overall consumption by industry and—with the UK Government’s net-zero strategy—manufacturers need to do what they can to control usage. With the rising costs of energy, reducing energy consumption supports not only the environment but has a significant impact on overhead costs. 

The primary cause of energy consumption within a cleanroom is the operation of the HVAC system to deliver the level of compliance. Using a localised approach to create clean environments, there is no over-processing of air. Only the zone that needs to be controlled has the high air change rates required to deliver the particulate concentration limits according to its ISO class.

Mobile cleanrooms offering part coverage

Part coverage of an injection moulding machine means only the mould area and clamp end are covered by a cleanroom, leaving material conveying equipment external to the controlled environment.

The material conveying equipment can create a degree of particulate so separating it from the clean area makes a big difference to the overall cleanliness of the environment. In turn, a reduction in contamination generated within the cleanroom reduces the number of air changes that are required to keep within its classification. If machines were fully enclosed, a different method of conveying would have to be utilised. 

Having the cleanrooms on castors means they can easily be wheeled away from the machine to give access to change tooling easily.

Temperature and humidity controls

Temperature variation can cause inconsistencies so certain products will run better when the process is kept at a consistent temperature. As Optimold have several injection moulding machines in the same white room area, the external room is temperature-controlled. Each cleanroom features a ceiling-mounted HEPA fan filter unit that intakes air from the controlled surrounding environment. This keeps the temperature at acceptable limits within the cleanrooms.

Additional heat gains from operatives will affect this ambient temperature. For the most part, operators only need to enter the cleanrooms periodically to package parts or take samples for inspection, so this approach to HVAC delivers the appropriate parameters.  

There is one unit, however, where a small amount of secondary work on components is performed within the cleanroom by an operator. Here comfort cooling is supplied to the cleanroom by a localised air conditioning unit. This unit supplies the cooled air to the fan filter unit, to provide terminal HEPA filtration and ISO compliance.

When to invest

The build of a new cleanroom can generally be delivered within the lead times of a new mould, so modular cleanrooms are fully scalable without the need to speculate to accumulate.