You have been tasked with selecting the most economical way

You have been tasked with selecting the most economical way to fabricate a hollow plastic container (imagine the structure of a cup), at each production run (number of parts made) 100, 10,000 and 1,000,000. You must select between blow molding and injection molding. Assume that you can make the same size cup from the same material by each process. Be sure to explicitly state your answer(s).

Solution

Lifetime of mold in minutes for blow mold = 500000/0.5 = 1*10⁶ min

Lifetime of mold in minutes for injection mold = 1000000/1.8 = 0.555*10⁶ min

write off time for blow mold = 5*3000 = 15000 hours =0.9*10⁶ min

write off time for injection mold = 5*3000 = 15000 hours = 0.9*10⁶ min

Total cost for blow mold per part = 38000+240000 + (0.026*1.4) +(35*15000)+(25*15000) = $ 1.178*10⁶

Total cost for injection mold per part = 85000+425000 + (0.026*1.4) +(35*15000)+(25*15000) = $ 1.41*10⁶

Although total cost for injection mold per part is little higher than that for blow mold, but its production rate is almost double than that of blow mold.

So the most economical way to fabricate hollow plastic container is injection mould.