CONCEPT GENERATION

Mike In Flight

AN INTERLOCKING INJECTION MOLDED CHILDREN’S TOY

As an exploration into mass manufacturing, I worked in a team of four to design and product a batch of 20 injection molded children’s toys from part design to scaled production. I served as the lead designer and engineer for the Mike and flame components, so those will be the focus of this breakdown.

SKILLS

  • 3D CAD and CAM

  • Design for manufacturing

  • Metrology and quality analysis

  • Injection Molding

  • CNC Machining

Channeling my younger self, I combined elements from two of my favorite Pixar films - Monster’s Inc. and Toy Story - to create Mike in Flight a.k.a Mike Wazowski riding a rocket ship.

REFLECTION

Planning ahead through the development process is key. Failure to preemptively design for manufacturing allows for issues to arise down the line, forcing the reworking of earlier steps - an inefficient use of time and resources. As an engineer, being conscious of how my role fits into more than just one's own responsibilities and recognizing your impact on others is key.

Documentation and communication are critical in collaborative projects. Each member of our team of four had their own roles and responsibilities, so to ensure all dimensions, press fits, and styles were aligned, we conducted frequent assembly checks throughout our process. This ensured that our final injection molds came together without interference or other avoidable issues.

OVERVIEW

I used NX CAD to design the initial parts and GD&T principles to calculate press fit pin connections. I made adjustments to ensure molds based on these parts would actually be manufacturable.

  • Split parts into two halves and hollowed them to create even wall thicknesses

  • Filleted all edges and drafted inner flat surfaces to aid part removal from mold

  • Eliminated undercuts and deep pockets because they are not injection moldable

  • Removed tiny, tight geometries because they were not achievable with available CNC tooling

DESIGN FOR MANUFACTURING

MOLD DESIGN

I used NX to translate the Mike and flame parts into core and cavity mold halves, adding a sprue, runners, gates, and bolt holes. I carefully oriented parts within the mold to:

  • Prevent undercuts and deep channels

  • Optimize runner widths and lengths to ensure equal fill time of parts, even of different sizes

I developed a manufacturing program in NX CAM to remove material from two aluminum blanks, forming the core and cavity. I generated toolpaths using few key design principles:

  • Stepped tool size down incrementally from large to small - a 1/4" end mill to a 1/16" ball mill

  • Debulked with large tools before details were fleshed out with smaller ones

I exported the completed manufacturing programs as gcode, loaded the CNC machine, and then ran the program.

MOLD MANUFACTURING

PRODUCTION AND METROLOGY

I experimentally varied injection molding pressure and temperature until identifying the combination of values that filled the molds completely, without overflow.

After producing 20 Mikes and 20 flame toys, I conducted a metrology analysis to compare produced lengths to the modeled lengths. Both parts consistently came in undersized. This can be attributed to the effects of shrinkage.

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