Designing Ribs For Additional Strength

When designers need to add stiffness to a component, ribs are the most effective structural feature. They strengthen the part without adding excessive material.

Guidelines:

• Rib thickness should be 50–60% of the adjoining wall
• Height should be 3 times the wall thickness
• Provide adequate spacing to avoid sink marks
• Use fillets to ensure smooth flow at rib intersections

Well-designed ribs make the part lightweight, strong, and easier to manufacture.

Using Draft Angles For Smooth Ejection

Draft angles help the molded part release smoothly from the mold. Without proper draft, parts stick to the core and cause ejection problems.

General rules:

• Add a minimum of 1° draft per side
• Increase the draft with deeper cores
• Add more draft for textured surfaces
• Avoid vertical walls with zero draft

Proper draft avoids costly mold repairs and prevents part damage during ejection.

Gate Placement And Its Impact

Gates are the entry points through which molten plastic enters the mold cavity. Their placement directly affects flow patterns, weld lines, and shrinkage.

Factors to consider:

• Position the gate at the thickest section
• Ensure balanced flow to all areas of the part
• Prevent gate marks on visible surfaces
• Choose gate type based on part geometry

Correct gate placement ensures even filling and reduces costly defects.

Managing Warpage And Shrinkage

Warpage occurs when different areas of the part cool at different rates, causing distortion. Shrinkage happens when plastic contracts during cooling.

• Methods to control warpage:
• Maintain consistent wall thickness
• Use symmetric designs wherever possible
• Reduce stress concentration points
• Choose materials with lower shrinkage rates

Design adjustments during the early stages help avoid manufacturing delays later.

Material Selection And Its Influence

Choosing the right plastic material affects strength, cost, durability, and moldability. Designers must understand each plastic behavior during processing.

Key material considerations:

Tensile strength and flexibility
Heat resistance
Chemical stability
Flow characteristics
Cost and availability

Common choices include ABS, PP, PC, nylon, and PEEK depending on the application.

Avoiding Sharp Corners And Stress Points

Sharp corners create stress concentration during molding and in the final product. They also restrict smooth flow of molten plastic.

Recommendations:

• Use rounded corners and fillets
• Maintain internal radius aligned with wall thickness
• Avoid 90-degree intersections without the proper radius.
• Ensure smooth transitions between surfaces.

Rounded edges lead to stronger and more reliable molded components.

Incorporating Undercuts Carefully

Undercuts further complicate mold design, requiring side action, lifters, or collapsible cores, ultimately increasing tooling costs.

Good practices:

• Avoid unnecessary undercuts
• Replace undercuts with snap fits, holes, or redesigns
• Use lifters only when needed
• Simplify mold design to reduce maintenance

Smart design decisions keep the mold efficient and affordable.

Prototyping Before Full Manufacturing

Before starting mass manufacturing, it is crucial to test the design using prototypes. This step ensures the part performs as expected.

Prototyping options:

• 3D printing
• CNC machining
• Soft tooling
• Pilot molding runs

Prototyping helps detect problems early and speeds up final production.

Cost Optimization Tips

Cost efficiency is essential in high-volume manufacturing. Small changes in design can significantly reduce overall manufacturing expenses.

Ways to reduce cost:

• Simplify geometry and eliminate unnecessary complexity
• Choose materials that fit both performance and budget
• Reduce mold actions and avoid multi-sliders unless essential
• Optimize wall thickness to minimize cycle time
• Use standard mold components where possible
• Thoughtful planning ensures high-quality parts at lower cost.