Towards more sustainable AFO manufacturing: An exploratory life cycle inventory of partially digital production

Ankle-foot orthoses (AFOs) are medical devices supporting individuals with pathological gait. Manufacturing fully customized AFOs with a carbon dorsal leaf spring (C-AFOs) traditionally relies on manual processes involving material waste and resource consumption. Additive manufacturing (AM), commonly referred to as 3D printing, offers potential pathways toward a more sustainable production, yet its impact on sustainability-related metrics in orthosis manufacturing remains insufficiently examined.

In this study a partially digital C-AFO manufacturing workflow was developed using AM, initially tested and it was investigated how the partial digitalization affects selected sustainability-related metrics compared to the established manual manufacturing workflow.

An exploratory study was conducted at a German orthotic workshop, where a partially digital workflow for C-AFO manufacturing was developed and implemented. Two C-AFOs were produced using the traditional manual and the new partially digital workflow, while both workflows were analyzed and compared by means of a gate-to-gate life cycle inventory analysis in accordance with ISO 14040/44. Data collection encompassed the consumed material mass (divided into material incorporated into the C-AFO, in-house reusable material, potentially externally recyclable material, and disposable material), electrical energy consumption, and process water usage.

Partial digitalization substantially reduced total material use by 4.59 kg (21%) and process water consumption by 12 L (83%), primarily by reducing the use of non-recyclable plaster models. Additionally, the proportions of in-house reusable and potentially externally recyclable materials increase, while the proportion of disposable material decreases. Conversely, electrical energy consumption increased by 15.96 kWh (172%), largely attributable to the 3D printing processes employed.

Although the exploratory nature and limited scope of this study preclude general conclusions regarding overall workflow sustainability, the findings indicate that transitioning from manual to partially digital C-AFO manufacturing presents possible sustainability potential. A comprehensive evaluation within the framework of a complete life cycle assessment is recommended to substantiate these initial results.