Team Website!

Our Team has been working on a website in addition to a blog to keep a more detailed track of the project as is progresses. Click the link below to check it out!

http://2008team.wix.com/around-the-world

Part STL files

https://www.dropbox.com/sh/5nqgzxin2fqlz9k/AACDpdpQhOYN_0KWCK_SyFG5a?dl=0

Earth Cap STL

https://www.dropbox.com/s/f8o02y23lq18rux/Earth%20Cap%202.008.STL?dl=0

Injection Mold: Outer Ring

Ring Mold Models (molds currently still in production)

Cavity Mold

Core Mold

Diagrams of the outer ring mold are shown above. Potential rework on the ring mold largely centers on the press-fit aspect of the ring size. Because the ring must sandwich the thermoform plastic dome piece onto the yo-yo base, shrinkage and tolerances are the most important factors. Before optimization runs, it will be important to check the fit of the ring over the base/thermoform parts and adjust any features to account for minor changes in the base/thermoform shape or thicknesses.

Injection Mold: Yo-yo Base

A picture of the mold for the base of the yo-yo is shown below. Some key features, such as the sprue, the runner, the center shaft, and the ejector pin holes, are labeled. A more detailed description of the base mold and the base part can be found in an earlier post, "Yo-yo base: An injection molded part."Since the base is the largest part, we are going to try to avoid needing to change the base. If there need to be adjustments for snap fits, we shall adjust the earth cap mold or the ring mold, keeping the base the same.

Injection Mold: Spaceship and Moon Ring

Cavity Mold 

Core Mold w/ Shutoff surface

The possible changes we will make to this mold will be to increase the diameter of the sphere side so that it can be more easily machined with a ball endmill of the appropriate diameter, and to change the basic shape of the spaceship side of the spinner to a bit more elongated and a less narrow nose, so that the tight corners and radii can be machined without ordering more expensive tools and without sacrificing the precision of the machining.

Injection Mold: Earth Cap

Possible changes we may need to make to the molds are the inner diameter of the bottom of the Earth Cap, if it does not fit with the post after shrinkage/ if the ejector pin effects it in any way.  Also, we may need to add draft angles to the part if it is not ejecting well.

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