LINGO Takes Sole Responsibility

While you may be fortunate enough to own a pair of hand-stitched Italian loafers, chances are you also have at least one pair of sneakers in your closet in which the soles were injection molded directly on to the shoe's upper. Efficiently allocating the molds for the injection process turns out to be a good optimization application.

Turntable or carousel molding machines are commonly used in the injection molding process. The carousels can hold up to 20 molds serviced by a single injection head. The molds are expensive and, given the distribution of sizes, some are utilized much more than others. Through astute planning and putting more than one style on the carousel at once, the shoe manufacturer can operate efficiently without having to have duplicates of many highly utilized molds. The challenge is to come up with a mold allocation scheme to produce a mixed basket of shoe orders (size, color, style) with the minimum number of mold set-ups.

LINGO Takes Sole Responsibility

An international group of five shoe manufacturers sponsored SATRA, a UK based research organization, to come up with ways to better solve their mold allocation problems. SATRA's aim was to develop a tool that could produce good allocations quickly, so that planners could interactively experiment with different order combinations.

The planners are generally comfortable within the spreadsheet environment, so SATRA decided to build the application around Excel. SATRA found it easy to quickly prototype the problem with What'sBest!. Once they were comfortable with the formulation, they moved the problem to LINGO. Using Visual Basic for Applications (VBA) within Excel, they were able to provide a polished front-end that insulated the user from the details of the optimization model. Their VBA application simply calls the LINGO DLL that builds and solves the problem and writes the solution back to Excel.

Schedules that used to take a planner up to four hours to prepare can generally be solved in three to five minutes with LINGO. SATRA found the development route to be very productive, and the shoemakers are very happy with the solutions. For more information on SATRA, visit their website at

For more information on LINGO, please see the product pages. You can also download a demo version from our download page or order a full blown version directly from our order page.

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