Design for refurbishment of child car seats – Towards circular safety critical products

This graduation project investigates the challenges of designing a safety critical consumer product suitable for the refurbishment loop of the circular economy through a case study on child car seats. Currently when child car seats are reused or resold on the second-hand market, their safety cannot be guaranteed as it is unknown whether the child car seat has previously been involved in a car accident. When child car seats are integrated in a refurbishment system, their safety can be guaranteed and thus their lifespan of safe use can be elongated. The refurbishment of child car seats starts with determining whether the child car seat has been in a crash, for example by integrating impact sensors in the child car seat through which the history of a child car seat can be known. Subsequently, it consists of inspecting all priority parts of the product; those are the parts most relevant for refurbishment because of their functional importance, failure frequency, and economic and environmental value. Based on these aspects, the priority parts of baby car seats are determined. The parts with the highest functional priority in child car seats are the parts that fulfil a safety critical function: either the part is responsible for the absorption of the crash impact, or the part contributes to the correct installation of the child in the child car seat or of the child car seat in the car. Three existing baby car seats and ISOfix bases are assessed on their ease of disassembly following the Hotspot Mapping method and the results are visualised in a Disassembly Map showing their disassembly sequence and product architecture. Based on this analysis it can be concluded that currently not all priority parts of both baby car seats and ISOfix bases are removable and that the product architecture of these product can be further improved for ease of disassembly and thus for refurbishment. The Disassembly Depth Index is developed to illustrate the level of parallelism within a product’s disassembly sequence. A set of guidelines is established which can be used to design safety critical consumer products tailored to refurbishment. This set of guidelines firstly incorporates guidelines specifically for safety critical products and furthermore consists of guidelines for product architecture, materials, and fasteners. To illustrate these guidelines a redesign of a baby car seat and of an ISOfix base has been made. These products are improved for refurbishment through the elimination of non-priority parts, by making safety critical parts removable and bringing them to the surface, by increasing the level of parallelism in the disassembly sequence, and by substituting materials with alternatives better suited for refurbishment.Integrated Product Desig