Small injection molded part

Key Design for Small Parts

Designing small parts requires precision to ensure functionality, manufacturability, and safety.

• Draft Angles: Essential for ejecting the part from the mold. A minimum of 1° per side is standard; more is better for textured surfaces.

• Wall Thickness: Critical. For small PP parts, aim for 1.0 mm to 2.5 mm. Uniform wall thickness is paramount to avoid sinks (surface depressions), warpage, and internal stresses.

• Ribs: Use ribs to add stiffness and strength without increasing overall wall thickness. A good rule of thumb is that a rib should be 50-60% of the nominal wall thickness.

• Fillets and Radii: Always use radii on sharp corners. This reduces stress concentration, improves flow of plastic, and strengthens the part.

• Living Hinges: A classic PP feature. The hinge must be thin (typically 0.25-0.5 mm) and run the full length of the part. The mold must be designed to allow plastic to flow parallel to the hinge line for optimal flex life.

• Undercuts: These require complex and expensive mold features like side-actions, lifters, or hand-loaded inserts. Design them out if possible.

Household Appliance Examples

• Coffee Makers: Water reservoir lids, grounds funnel, small compartments.

• Blenders: Measuring cup lids, small pushers, ingredient chutes.

• Food Processors: Dough blade, small pushers, accessory lids.

• Electric Kettles: Lid opening mechanisms, water level indicator windows.

• Dishwashers: Detergent cup lids, small rack components, rinse aid covers.

• Air Fryers & Ovens: Button caps, small handle covers, interior racks.