Design for Manufacturability in Cleanroom Injection Moulding

Why Design Is as Important as the Environment

<a href="https://www.biplas.com/cleanroom-moulding/">Cleanroom injection moulding </a> is one of the most powerful ways to produce safe, sterile, high-precision components for medical and biotech applications. But even the most advanced cleanroom can’t compensate for a poorly designed part. Design for manufacturability (DFM) is essential to ensure that parts can be moulded efficiently, consistently, and cleanly under controlled conditions. This article explores how thoughtful design decisions support both process efficiency and contamination control.

The Challenge of Cleanroom Constraints

Designing a part for cleanroom moulding involves more than just choosing a geometry. Engineers must consider:

Material Compatibility: Only medical-grade polymers that can withstand sterilisation methods such as gamma irradiation, EtO, or autoclaving.

Tolerances and Precision: Cleanroom moulding excels at tight tolerances, but the design must enable consistent filling and cooling.

Assembly Under Clean Conditions: If the part requires assembly, the design should minimise handling and ease automation.

Ignoring these factors can lead to higher defect rates, longer cycle times, or even regulatory setbacks.

Design Principle 1: Optimise Wall Thickness and Geometry

Uniform wall thickness promotes consistent cooling and reduces internal stresses. Sudden changes in thickness can lead to sink marks or voids. In a cleanroom, where scrap and rework must be minimised to preserve sterility and cost control, uniform geometry is even more important.

Consider adding gentle radii instead of sharp corners, avoiding unnecessary undercuts, and ensuring smooth transitions. This not only improves mouldability but also makes parts easier to clean and inspect if needed.

Design Principle 2: Gate Location and Flow Paths

Where molten polymer enters the mould (the gate) affects how the cavity fills. Poor gate placement can cause flow marks, weld lines, or incomplete filling. In cleanroom production, defects like flash or burrs are not only cosmetic but can create particle sources or interfere with assembly. Early collaboration between designers and moulding engineers helps determine optimal gate locations to balance flow, pressure, and aesthetics.

Design Principle 3: Material Selection with Sterilisation in Mind

Many medical components must be sterilised after moulding. Each sterilisation method (gamma, EtO, autoclave) interacts differently with polymers:

Polypropylene (PP): Good chemical resistance and cost-effective, compatible with EtO and gamma.

Polycarbonate (PC): High strength and clarity, but may yellow under gamma.

Cyclic Olefin Copolymer (COC): Excellent optical properties, low moisture absorption.

Selecting the right material early prevents costly redesigns or regulatory issues later.

Design Principle 4: Tolerance Control at Micro Scale

Cleanroom moulding often involves micro-features such as tiny channels, snap-fits, or optical elements. Tolerances must be achievable not only in the mould but also under the environmental and process conditions of the cleanroom. Advanced simulation tools can predict flow, shrinkage, and warpage to fine-tune the design before tooling begins.

Design Principle 5: Surface Finish and Particle Control

Surface finish affects both function and cleanliness. For example:

Microfluidic channels may require very smooth surfaces to control fluid flow.

Textured surfaces can trap particles or microbes if not properly specified.

High-gloss finishes may show minor contamination more clearly.

Working with mould makers experienced in medical parts helps ensure the right surface finish for your application.

Design Principle 6: Tooling Strategy for Cleanroom Production

The mould itself must be designed for easy cleaning, minimal particle generation, and reliable performance:

Steel Selection: Use corrosion-resistant, medical-grade tooling steel.

Venting: Proper venting prevents gas traps and reduces flash.

Maintenance Access: Design moulds so inserts can be removed and cleaned without disassembling the entire tool inside the cleanroom.

These strategies minimise downtime and contamination risk during maintenance.

Design Principle 7: Facilitating Automation and Assembly

Automation is a cornerstone of cleanroom production because it reduces human contact. Designers can support automation by:

Including pick-and-place features for robotic grippers.

Designing parts to self-locate during assembly.

Minimising the number of components to reduce assembly steps.

Parts that are easy for robots to handle can move seamlessly from moulding to packaging without leaving the controlled environment.

Design Principle 8: Prototyping Under Realistic Conditions

Prototyping in a standard environment may not reveal all the challenges of cleanroom production. Whenever possible, create pilot runs in a cleanroom or at least under simulated conditions. This allows you to validate:

Material behaviour under cleanroom humidity and temperature.

Handling and packaging processes.

Inspection and measurement methods for micro-features.

Early detection of issues can save months of delay and prevent regulatory headaches.

The Role of Collaboration with Cleanroom Specialists

Designing for cleanroom moulding is a multidisciplinary effort. Partnering with a specialist provider early in the design phase offers several benefits:

Design for Manufacturability Feedback: Experienced engineers can suggest geometry changes to improve mouldability and cleanliness.

Material Guidance: Recommendations for polymers compatible with sterilisation and regulatory requirements.

Tooling Expertise: Access to mould makers skilled in medical-grade tooling and finishes.

Process Validation Support: Assistance with IQ/OQ/PQ documentation to meet ISO 13485 or FDA expectations.

This collaboration ensures that the part not only meets functional specifications but also can be produced reliably and cleanly at scale.

Case Example: Reducing Defects Through Design Adjustments

A medical OEM designed a diagnostic housing with complex snap-fits and variable wall thicknesses. Initial moulding trials in a cleanroom showed high scrap rates due to flash and incomplete filling. By working with a cleanroom moulding partner, the team adjusted gate locations, standardised wall thickness, and switched to a polymer better suited for gamma sterilisation. The result: a 40% reduction in defects and faster cycle times, all while maintaining sterility.

Beyond the Part: Designing the Whole Process

Design for manufacturability extends beyond the part geometry. It includes packaging, labelling, and logistics. For instance, parts that can be nested or stacked reduce packaging material and handling steps inside the cleanroom. Labelling areas should be accessible to automated printers to avoid manual contact. Thinking holistically about the part’s entire lifecycle under clean conditions enhances efficiency and compliance.

Good Design Is the Foundation of Clean Production

Cleanroom injection moulding offers unmatched control over contamination and quality — but only if the part is designed with the process in mind. By considering material selection, geometry, tolerances, surface finish, tooling, and automation from the outset, manufacturers can produce components that flow smoothly through the cleanroom with minimal waste and maximum reliability. In the high-stakes world of medical and biotech manufacturing, design for manufacturability isn’t just a best practice — it’s a competitive advantage.