Blog Deliverable II

Blog Deliverable II

An in depth look at our Connector Piece Molds:

Description:

               Pictured above are the connector piece molds that are ready for injection molding.  The 

cavity has the important details for injection molding (sprue, runner, and gates) while the core has the important details of the actual part and the ejector pin holes. 

The key features of this mold design are the:

-    ejector pin holes

o   to allow the ejector pins to push the piece out

-    drafted sides

o   for the piece to pop off the mold easily

-    duplicate copy

o   to speed up the injection molding process

Dimension Justification:

The dimensions for this piece are based off of the two parts that it is connecting: the bearing and the hamster.  The inner diameter of the bearing is 6mm or .236 inches.  Meanwhile, the pin sticking out of the hamster is .15 inches in diameter.  To account for these two press fitting features, the hole for the bearing has a tolerance of +.005in while the pin for the hamster has a tolerance of -.005in.  To account for the shrinkage, the entire piece was scaled up by about 2%, like the rest of the pieces that we are injection molding, including the hamster. 

Manufacturing Process:

The manufacturing process for these molds is done all on the mill.  A detailed explanation can be found in our process plan.  The reason that we have two copies of the connector piece on the molds is to save time during the injection molding process.  Each copy of the connector piece takes about 25 minutes to machine.  By having two copies of the piece we cut our injection molding time from roughly 50 minutes to 25 minutes (assuming roughly 30 seconds per injection molding cycle).  This seems to be an equal trade-off but since there is only one injection molding machine in the shop, the time spend on the injection molding machine is worth more. 

Overall Time Estimates:

               We have created a machining time estimate sheet to help us predict the over time spent machining.  The spreadsheet can be viewed here.  Our schedule for the yo-yo production depends heavily on how quickly we can finish machining our molds.  As of now, we have completed the connector piece molds, the thermoform piece mold, and most of our hamster molds.  Any changes to our estimates will be reflected in our spreadsheet.

Other Molds:

               Our other completed mold at this time is for the thermoform piece.

Description:

               Pictured above is the thermoform piece mold that is almost ready for draft thermoforming.  The only thing that is missing are the small 1/32 holes that allow vacuum pressure to be distributed to the plastic.

The key features of this mold design are the:

-    locator pin holes

o   to easily center the piece for cutting

-    drafted sides

o   for the piece to pop off the mold easily

-    ridge

o   to fit the outer wheel bar

We expect that our thermoform piece will work well but some anticipated issues that we may have are the fit with the outer wheel bar and the clearance for the hamster in the yo-yo.  If we run into these issues we will have to re-size and re-machine the part.