Industrial Design and Mechanical Engineering for Injection Moulding
InDesignLabs developed the industrial design and mechanical enclosure of a compact hemoglobin-testing dongle intended for portable, point-of-care diagnostics. The challenge was to package the sensing components, electronics, device connector and sample interface inside a small enclosure that remained intuitive to use, visually credible and suitable for injection-moulded production.
The Challenge
Unlike a conventional benchtop analyzer, a diagnostic dongle has extremely limited internal space. Every surface and internal feature must perform a specific function.
The enclosure needed to:
- Accommodate the PCB, sensing system and connector within a compact footprint.
- Maintain the required alignment between the sample interface and sensing components.
- Provide straightforward sample loading and testing.
- Protect sensitive internal components from impact, contamination and ambient light.
- Support the external connector against bending and handling loads.
- Allow convenient assembly and servicing.
- Eliminate unnecessary bulk while retaining adequate structural rigidity.
- Be engineered for repeatable, economical injection moulding.
Our Design Approach
1. Component Packaging and Product Architecture
The design process began with the internal electronic and sensing architecture. Component envelopes, optical clearances, PCB mounting points, connector position and assembly sequence were established before the external form was developed.
The enclosure was divided into functional zones for:
- Sample insertion and measurement.
- Optical and electronic components.
- PCB mounting and cable management.
- Host-device connection.
- Status indication.
- Opening, inspection and assembly.
This prevented the exterior styling from interfering with the instrument’s functional requirements.
2. User-Centred Industrial Design
The product had to communicate its orientation and operation without requiring unnecessary instructions. The enclosure form therefore guides the user toward the sample-loading area while visually separating it from the connector and electronic section.
The industrial design incorporated:
- A clearly defined sample interface.
- Rounded edges for comfortable handheld use.
- A compact, low-profile form suitable for portable testing.
- Contrasting colours to distinguish functional zones.
- A visible status-indicator area.
- Sculpted surfaces that provide direction without adding separate labels.
- A protective lid for accessing the internal measurement region.
The blue-and-grey colour scheme gives the device a professional diagnostic identity while making its main interaction areas immediately recognizable.
3. Sample Access and Lid Mechanism
The lid was designed as an integrated functional component rather than a decorative cover. Its geometry provides controlled access to the measurement area while helping protect the internal components when the device is not being used.
The mechanism was developed with attention to:
- Reliable opening and closing.
- Repeatable positioning.
- Adequate finger access.
- Protection against accidental detachment.
- Clearance from internal components.
- Mouldable hinge and retention features.
- Simple assembly without excessive hardware.
The lid and enclosure interface also helped control gaps around the sensitive measurement region.
4. Optical and Mechanical Alignment
Consistent diagnostic performance depends on maintaining the required relationship between the sample, sensor and optical path. Internal locating features were incorporated to position the PCB and sensing components accurately within the enclosure.
Datum surfaces, ribs and component supports were used to control alignment while avoiding an unnecessarily tight tolerance across the entire housing. The critical dimensions were concentrated around the measurement system, allowing non-critical cosmetic areas to retain practical moulding tolerances.
Light-control features could also be incorporated around the sensing region to reduce interference from ambient light.
5. Connector Protection
The external connector was one of the most mechanically vulnerable parts of the device. A connector mounted only to the PCB would be exposed to bending loads during insertion, removal and accidental side loading.
The enclosure was therefore developed to provide mechanical support around the connector and transfer handling loads into the housing instead of allowing them to act entirely on the PCB solder joints.
Clearance around the connector was also considered to ensure reliable mating with the intended host device.
Engineering for Injection Moulding
The housing components were engineered according to plastic injection-moulding principles from the beginning of the development process.
Key design considerations included:
- Consistent nominal wall thickness.
- Appropriate draft on mould-release surfaces.
- Rounded internal corners for improved material flow.
- Ribs and gussets for stiffness.
- Supported bosses for fastening and PCB mounting.
- Controlled transitions between thick and thin sections.
- Reduction of sink-mark and warpage risks.
- Practical tooling directions and parting lines.
- Avoidance of unnecessary undercuts and side actions.
- Concealed joints and fastening features where practical.
- Suitable clearances for repeatable production assembly.
ABS and PC-ABS material options could be evaluated with the manufacturer according to impact resistance, surface quality, dimensional stability, chemical resistance and applicable safety requirements.
Assembly and DFM Development
The enclosure architecture was reviewed against the complete assembly sequence. The design considered how the PCB, sensing components, indicator, connector and lid would be installed and secured without creating inaccessible fasteners or fragile operations.
Before tooling, the CAD data was prepared for toolmaker review covering:
- Draft analysis.
- Wall-thickness analysis.
- Parting-line feasibility.
- Boss and rib proportions.
- Ejection requirements.
- Gate-location implications.
- Potential sink and weld-line areas.
- Critical assembly tolerances.
- Surface-finish and colour-break requirements.
The Outcome
The resulting design transformed a collection of sensitive diagnostic components into a compact and coherent point-of-care product.
The project delivered:
- A distinctive portable medical-device identity.
- An intuitive sample-access arrangement.
- Protection and support for the external connector.
- Controlled positioning of critical sensing components.
- An integrated access-lid mechanism.
- Injection-moulding-oriented enclosure geometry.
- CAD data suitable for prototyping, DFM review and tooling development.
- Product visualizations for design approval and communication.
This project demonstrates InDesignLabs’ ability to combine industrial design, precision mechanical packaging and injection-moulded plastic engineering for compact diagnostic devices.
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