OM 300 1nd Edition Lecture 32 Outline of Last Lecture I JIT II Eliminate Waste III The 5 Ss Outline of Current Lecture I Sources of Variability II JIT III Supplier Concerns IV Scheduling Current Lecture Sources of Variability 1 Incomplete or inaccurate drawings of specifications 2 Poor production processes resulting in incorrect quantities late or non conforming units 3 Unknown customer demands Improve Throughput The time it takes to move an order from receipt to delivery The time between the arrival of raw materials and the shipping of the finished order is called manufacturing cycle time A pull system increases throughput By pulling material in small lots inventory cushions are removed exposing problems and emphasizing continual improvement Manufacturing cycle time is reduced Push systems dump orders on the downstream stations regardless of the need Just In Time JIT Powerful strategy for improving operations Materials arrive where they are needed when they are needed Identifying problems and driving out waste reduces costs and variability and improves throughput Requires a meaningful buyer supplier relationship JIT Partnerships JIT partnerships exist when a supplier and purchaser work together to remove waste and drive down costs Four goals of JIT partnerships are o Removal of unnecessary activities These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute o Removal of in plant inventory o Removal of in transit inventory o Improved quality and reliability Concerns of Suppliers Diversification ties to only one customer increases risk Scheduling don t believe customers can create a smooth schedule Lead time short lead times mean engineering or specification changes can create problems Quality limited by capital budgets process or technology Lot Sizes small lot sizes may transfer costs to suppliers Distance Reduction Large lots and long production lines with single purpose machinery are being replaced by smaller flexible cells Often U shaped for shorter paths and improved communication Often using group technology concepts Increased Flexibility Cells designed to be rearranged as volume or designs change Applicable in office environments as well as production settings Facilities both product and process improvement Impact on Employees Employees may be cross trained for flexibility and efficiency Improved communications facilitate the passing on of important information about the process With little or no inventory buffer getting it right the first time is critical Reduced Space and Inventory With reduced space inventory must be in very small lots Units are always moving because there is no storage Reduce Inventory Reducing inventory uncovers the rocks Problems are exposed Ultimately there will be virtually no inventory and no problems Shingo says Inventory is evil Reduce Lot Sizes Ideal situation is to have lot sizes of one pulled from on process to the next Often not feasible Can use EOQ analysis to calculate desired setup time Two key changes necessary o Improve material handling o Reduce setup time JIT Scheduling Schedules must be communicated inside and outside the organization Level schedules o Process frequent small batches o Freezing the schedule helps stability Kanban o Signals used in a pull system Level Schedules Process frequent small batches rather than a few large batches Make and move small lots so the level schedule is economical Jelly bean scheduling Freezing the schedule closest to the due dates can improve performance Kanban Kanban is the Japanese word for card The card is an authorization for the next container of material to be produced A sequence of kanbans pulls material through the process Many different sorts of signals are used but the system is still called a kanban Usually each card controls a specific quantity of parts Multiple card systems may be used if there are several components or different lot sizes In an MRP system the schedule can be thought of as a build authorization and the kanban a type of pull system that initiates actual production