The Over-Specified Phone Case
A pupil is designing a phone case for a school enterprise project. The brief says: 'protect the phone, be sustainable, cost under £3 to make, and look premium'. The pupil proposes a two-part case: a recycled-PET shell plus a moulded TPU bumper, joined with adhesive, packed in a printed card sleeve inside a plastic window box. Bill of materials per unit: shell £0.90, bumper £1.10, adhesive £0.15, card sleeve £0.35, plastic window £0.25, labour ignored. The teacher notes the school cannot recycle mixed PET/TPU, and the enterprise mentor says buyers judge 'sustainable' by what they can see and by end-of-life.
1. Calculate the material cost and judge the design against the brief, identifying the weakest requirement.
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Material cost = 0.90 + 1.10 + 0.15 + 0.35 + 0.25 = £2.75, leaving only 25p of headroom under £3 before any waste, rework or postage - so the cost requirement is met only on paper. The weakest requirement is sustainability, and it fails in two places. First, the product is a bonded PET/TPU laminate: the adhesive means the two polymers cannot be separated, so neither can be recycled in practice, which contradicts the recycled-PET selling point. Second, the packaging uses a plastic window in a card sleeve - again a mixed-material pack that is hard to recycle and is the first thing the buyer sees. 'Premium look' is subjective and not evidenced. Judgement: the design is over-specified; the second material and the window are buying little protection and costing the strongest claim.
2. Propose a simplified redesign and explain how you would test that it still meets 'protect' and 'premium'.
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Redesign: a single-material shell in recycled PET (or a single recycled TPU), with protection coming from geometry rather than a second polymer - a raised lip around the screen, corner ribs and a wall thickness chosen for impact, all in one moulding. Drop the adhesive entirely, so the case is mono-material and genuinely recyclable. Replace the window box with a single printed card sleeve from recycled board, no plastic window; the printing carries the premium message. Cost falls to roughly £1.25–£1.50, restoring headroom. Testing 'protect': a controlled drop test - same phone mass dummy, drops from 1.0 m onto a hard floor at corner, edge and face, repeated, checking for case cracking and transmitted shock (e.g. a simple accelerometer app or a brittle indicator). Compare against the two-part design as a control. Testing 'premium': a short user panel scoring appearance, feel and perceived value blind to cost, plus a check that the card sleeve survives handling. Success = equal or better drop performance, lower cost, and mono-material recyclability confirmed with the local waste contractor.