Precision Aerospace Machining and the Seven Wastes of Lean (Part 3)

In continuing on the Lean Journey, we will talk about the third of seven wastes: Inventory.  Historically, inventory was not considered a waste.  Large batch manufacturing was a necessity at the beginning of modern machining and manufacturing.  Inventory stocks were considered healthy as they indicated that a business could ship to their customers quickly.  The story of Inventory becoming considered a waste starts in post WWII Japan.  Japan underwent a transformation in their productivity and processes after WWII and began to compete well on the world market.  Unfortunately Japan does not have the land area that America does, and therefore the cost of holding inventory was much greater – due to the higher property costs, etc.  Toyoda quickly realized that smaller batches, when made efficiently, lead to lower overall costs than large batches do.

In a precision aerospace machining environment, a balancing act is needed.  Since CNC Industries machines a large variety of precision parts we cannot afford to have a specialized machine for each part or process that we do.  Small machine shops also do not have the luxury of a rolling assembly line between our machines.  With these restrictions, and the large amount of processing and manufacturing time that it takes to make a single aerospace part, we are put into a more difficult position that a production facility.  We cannot truly operate with no inventory as the goal would be, so we must decide on the ideal inventory to keep on hand.

Precision aerospace machining processes typically have rather long setup times relative to simpler machining processes.  This causes the ideal batch size to increase in order to compensate for the lost time on the machine while it is down for setup.  At CNC Industries we have worked long and hard to decrease our setup times and have successfully lowered our setup time by 75% over the last 5 years.  This has enable us to lower the ideal batch size as well, which in turn allows us to hold less inventory.

In addition to the setup process improvements that we have made over the years, information management is key to efficiently running small batches.  Smaller batches will mean more switchovers, more setups, and more jobs running at the same time.  With all of these issues, scheduling is both critical and difficult.  Job Manager II allows us to have a visual reference of the schedule at any computer throughout our facility and quickly identifies and problems or potential problems at an early stage of the process which allows us to quickly make any necessary adjustments.