Shuttle molds are made through the shuttle injection molding process. It is one of the more complicated types of molds and requires injection mold makers who understand more than just the basics of that process. Where injection molds usually produce a single product at the end, shuttle molds typically produces two bottom halves with a single top half.
The shuttle mold process creates a single unit – the top half and the first bottom half are made simultaneously. At the same time a second bottom half is being processed to include all of the additional aspects, such as inserts. Once the process is complete, the completed mold is moved further down the assembly line. The lower half with the added inserts is then worked with the top half to ensure it fits like the first one did.
Custom mold makers then begin the process again, closing the mold so that the bottom can be adjusted to align with the top as the second lower half is assembled.
The primary purpose of shuttle molds is to reduce the amount of time required to process each mold. Because the more complex portion of the mold is done at the same time as the top and bottom half are aligned, the custom mold makers do not have to wait for the inserts and other additions to be completed before completing another one. Since the top half does not require additions, it only needs to be included in the first round of the process.