1. Applied Methodology Design for Manufacturing (Injection Molding) Daniel Codd, Jason Liang, Dan Tulayasathien, & Keith Ip

2. Background Project objective: –Reduce assembly time and cost. Design concept: –Replace existing honeycomb side-panels with injection molded plastic panels.

3. Design Rationale Why injection molding? –Reduce part count. –Less labor intensive. –Reduce assembly time. –Increase yield rate of the final product. –Reduce manufacturing cost. –“Unlimited” quantities. –Little or no finishing process.

4. Introduction to Injection Molding Plastic hopper Die and press Injection Screw

5. Common Problems with Injection Molding Process Part shrinkage Insufficient venting causing air bubbles Sink marks due to unequal thickness Poor surface finish Distortion from insufficient cooling

6. DFM: Injection Molding Sharp corners restrict plastic flow.

7. DFM: Injection Molding Radiused corners also add to the stiffness of the design.

8. DFM: Injection Molding Webs around bosses reduce weight and prevent sinkage marks and voids. BadGood

9. DFM: Injection Molding Keep in mind flow direction when making changes in wall thickness

10. DFM: Injection Molding Uniform wall thicknesses will minimize shrinkage and reduce void formation and sinkage.

11. Strategies to Increase Strength and Stiffness Ribs: rule of thumb for proportions. Rib thickness should be 2/3 of wall thickness.

12. Strategies to Increase Strength and Stiffness Ribs: rule of thumb for preventing sink marks.

13. Strategies to Increase Strength and Stiffness Ribs: Circular or diagonal ribbing reduces twisting; bidirectional ribbing reduces sagging and bending.

14. Strategies to Increase Strength and Stiffness Lip The rounded lip (C) not only draws the eye away from misalignment, but also acts as a decorative element and functions as a handle for taking the pieces apart.

15. Strategies to Increase Strength and Stiffness Webs around bosses

16. Strategies to Increase Strength and Stiffness Gussets

17. Strategies to Increase Strength and Stiffness Part contour and Metal reinforcement

18. Knowledge Captured Ribs = less weight, more stiffness. Rib thickness = 2/3 wall thickness Oriented to provide maximum bending stiffness. (waffle pattern) Contoured shape helps increase stiffness. Use of lips and gussets stiffens the panel. Use of webs around bosses prevents sink marks.

19. Applied Methodology to Design Ribs Lips Webs

20. Any Questions?