Archive for November, 2010

Injection Molding is a manufacturing process for producing parts from both thermoplastic and thermosetting plastic materials. Plastic is known to be versatile and economical material that is used in many applications.

Products will be designed by industrial engineers and or an engineer. In modern age, the product can be designed using Computer aided design such as Solidworks, AutoCadd, Pro-E and many CAD softwares.

Design consideration

Always minimize undercut to minimize manufacturing cost. Can use slider if undercut is unavoidable due to its special feature.

Draft. Part design should include draft features to facilitate removal from the mold in direction of the mold opening . Typical draft angles should be 1 to 2 degrees for part surfaces.

Wall Thickness. Use uniform wall thickness throughout the part. This will minimize sinking, warping, residual stresses and improve mold fill and cycle times.

Radii, Fillets and Corners. External and Internal radii should share same center point. A fillet radius should be 25 to 60% of nominal thickness. Break all corners with radius. Suggested minimum radius is 0.5mm (0.020in).

Ribs. Rib thickness should be 50 to 60% of the nominal wall thickness and the maximum height is 3 times the height of the wall.

Boss and Gussets. Typical OD of boss is 2 times ID. It’s height should be less than the 3 times of OD. The height of Gusset can be up to 95% of the boss. While it’s length can be 30 to 100% of its height.

Reference:

http://www.engineersedge.com/injection_molding.htm

http://www.polymerhouse.com/datasheets/GE_Thermo%20Plastic%20%20DesignGuide_[1].pdf

http://en.wikipedia.org/wiki/Injection_molding

http://www.efunda.com/designstandards/plastic_design/plastic_intro.cfm