Yo-yo Base: An Injection Molded Part

A. The base mold has a parting line at surface where the base would meet the ring. The core mold is made using the lathe and the mill (the center shaft of the base mold, where the spinner is placed, needed to be milled into the core mold). Here is what the process of machining the cavity would look like. Here is what the process of machining the core on the lathe would look like. After the core is lathed, it is then put into the mill to drill the ejector pin holes and to hollow out the center shaft of the base mold. The cavity mold then uses the mill to create the runner from the sprue to the part. 

B. In class, there were example yo-yo base molds and a few of their injection molded parts. From these examples, I measured the injection molded base outer diameters and compared them to the outer diameter on their respective molds. From this I saw that the base molds shrunk around 2% in size from their mold sizes. Thus, we decided to have a scale factor of 1.02 for the base mold.

C. Process Plan for yo-yo base mold

Step	Operation	Machine	Tool	Justification
Cavity Mold
1	Bore cavity mold Rough Pass	PUMA Lathe	T1010 0.03125 Large Bore	Use bore tool to make a rough pass and cut out the design for the base of the yoyo cavity
2	Bore cavity mold finish pass	PUMA Lathe	T1010 0.03125 Large Bore	Use bore tool again on final pass to smooth mold
				1m 16.94s
3	Make runner from sprue to part	Protrak Mill	#9 sphere endmill	Use the sphere endmill to create the runner from the sprue to the part
Core Mold
1	Lathe rough pass core mold	PUMA Lathe	T0101 Turning Face tool	Turn down the face of the mold to match the core of the base part of the yoyo
2	Lathe finish pass core mold	PUMA Lathe	T0101 Turning Face tool	Finish pass over previous cut to smooth and clean
3	Lathe Groove rough pass	PUMA Lathe	T0909 Trepan Tool	Turn the center of the part down to match the central axis and mounting point for the earth part onto the base mold.
4	Lathe groove finish pass	PUMA Lathe	T0808 Trepan tool	Smooth out previous step using a slightly smaller radius trepan
5	Mill Peck Drill	Protrak Mill	3/16” flat endmill	Drill out the center shaft of the core mold
6	Circle Mill for center shaft	Protrak Mill	Circle mill	Fully mills out center shaft
7	Center drill for ejector pin holes	Protrak Mill	#13 drill: #2 center drill	Preps ejector pin holes to be drilled
8	Drill ejector pin holes	Protrak Mill	#17 Drill	Drills out holes for the ejector pins