Injection Molding Study
Over the course of this project, my team designed and machined custom molds to produce an injection-molded part, gaining experience with the equipment, processes, and techniques involved in injection molding.
Skills Used
Siemens NX CAD & CAM, CNC Milling & Toolpath Programming, Injection Mold Design, DFM, Precision Machining, Injection Molding
Initial Sketches & Conceptualization
In our product brainstorming, our goal was to come up with a fun, multi-part object that could creatively interact with its components. We settled for a freshly hatched penguin named Egguardo.
CAD Modelling: Part Design
Design Considerations:
1. Edge blend to remove sharp geometries.
2. Central alignment pin to hold penguin.
3. Convex curve to prevent lodging after cooling.
Finally, we loaded our molds into the hydraulic injection molding machine and found the optimal nozzle and barrel temperature, pressure, injection time, and cooling time to create our desired results.
CAM and CNC Milling
After we used the mold part files to make CAM programs in NX Siemens, we downloaded the generated G-Code to communicate with the CNC Mill and instruct the precise movements needed to machine our parts. Using 8 tools, four programs, and many hours, we were able to machine our core and cavity molds for both parts.
When modeling our part, we prioritized achieving a penguin-like form that fit within its shell, while ensuring manufacturability for injection molding. Key considerations included parting line placement, drafting surfaces for easy release, maintaining uniform wall thickness to prevent heat sinks, and oversizing to account for shrinkage. Below are detailed evaluations of these design choices.
4. 3/32” press fit pins and holes for snap assembly.
5. Increased wall thickness due to pin and hole supports.
CAD Modelling: Mold Design
We then designed our cavity and core mold components for each part, requiring four more part files. These would be used, along with blanks, to create the CAM program in NX that would guide our CNC milling process.
4. Parting line splits part along front plane perimeter in the middle.
5. Shutoff feature.
6. Runner extending from sprue to channel material into both halves evenly.
Results of Injection Molding
6. Shutoff feature to create alignment hole in bottom of penguin.
7. 2 degree draft to account for cooling.
Design Considerations:
1. Parting line set at the edge of the rim.
2. Location of gate from sprue to mold cavity from 0.15” away.
3. Cold well added to trap cold slugs and optimize material flow.
Dimensioned Drawings
