Injection molding with very thin walls

Secrid asked BPO for help with the engineering of a new plastic component. The main challenge was to ensure that the very thin walls were filled properly during injection moulding, while at the same time producing a visually optimal component.

The Secrid Cardprotector is a wallet with a patented mechanism that allows cards to be revealed step by step. Secrid has developed a variant that can be used in combination with MagSafe: Apple’s magnetic attachment technology. iPhones have a magnetic ring on the back, which automatically aligns and securely attaches MagSafe accessories.

Simulation of the expected warpage after injection moulding

The addition to the existing product consists of a ring-shaped magnet and a plastic plate the size of the Cardprotector. The wall thickness of this injection-moulded part is minimal (1.45 mm) to keep the Cardprotector as thin as possible. The recess for the magnet is even thinner (0.4 mm), which is necessary for optimal magnetic force. Such thicknesses and the differences between them are challenging for the overall manufacturability and visual quality of the product. Thin wall thicknesses make filling a mould critical. In addition, shrinkage differences can occur, causing the product to warp.

BPO provided advice on the design, material selection, and manufacturability based on injection moulding simulations. In a number of iterations, material advice was given for PC+ABS, the injection point was determined, and details in the geometry were fine-tuned. This gave Secrid more certainty about the feasibility of the injection-moulded part during its development. The result is a producible part that does not warp and contains no visual defects such as air inclusions or flow lines.

The Cardprotector for MagSafe is now available and a great success. For more information, see also: https://secrid.com/en-nl/collections/cardprotector-for-magsafe/