A 10-week project to manufacture an injection molded toy designed by 4th grade Nettelhorst Elementary School students.
The mini globe toy was created in a design for manufacturing course I took Winter quarter of 2016. My team of three students set out to transform a globe concept by Nettelhorst students Sophia S., Leslie, Ada and Oskar into a real 4" injection molded toy.
We won a second place design award of 30 toy designs.
MY ROLE: CAD modeling, CAM programming for one of our two molds, and optimizing injection molding parameters
DESIGN + MANUFACTURING PROCESS
TRANSLATING SKETCH INTO CAD ASSEMBLY
The first part of the process involved transforming the concept sketch to 3D models in NX that could be manufactured.
What we kept in mind while designing parts:
•A required snap or interference fit between two parts of the entire globe assembly
•Appropriate parting lines and cores to avoid undercuts in molds
•Uniform wall thicknesses to avoid shrinkage defects
•Staying true to the original concept sketch
CREATING PART MOLDS
Mapping the parts onto 4"x 4" aluminum block molds limited both our part size and the amount of cavity area available. For the stand and axis parts, I maximized the production space by including two cavities for each part on one mold block.
Another design consideration here was ensuring flow path ratios were within acceptable limits for all parts. This determined where runners, gates, and relative spacing of parts were mapped out on the 4" square block.
INJECTION MOLDING THE GLOBE
The optimal injection molding parameters were individually tuned through a series of trial runs for each mold. We performed statistical analysis of a 180-part production run. The 180-part run began with our optimized settings, experienced an intentional parameter shift, and a return to our original baseline. Measurements of the stand height were taken as a measure of our part variation throughout the entire run.
A Shewhart control chart revealed the effects of the parameter shift in group 2. The overall distribution was normal as expected.
We produced an injection molded toy that brought a group of fourth grade students' idea to realization, and won a second place design award.
This project allowed me to focus on design for manufacturing and to thoroughly understand the injection molding process from part design to post-production analysis.