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【正文】 d JIT Purchasing ? Interbased information systems allow firms to quickly place orders for materials with their suppliers ? This is an efficient and effective purchasing process ? Saves the time of paperwork ? Avoids errors associated with paperwork ? Reduces procurement lead time ? Reduces labor costs ? … and Kanbans can be sent to suppliers 42 Reducing Inventories through Setup Time Reduction ? Central to JIT is the reduction of production lot sizes so that inventory levels are reduced. ? Smaller lot sizes result in more machine setups ? More machine setups, if they are lengthy, result in: ? Increased production costs ? Lost capacity (idle machines during setup) ? The answer is: REDUCE MACHINE SETUP TIMES 43 Setup Time Required for an EOQ ? The economic production lot size (EOQ) model (detailed in Chapter 14) is: where: D = annual demand rate d = daily demand rate p = daily production rate C = carrying cost per unit per year S = cost per setup … more 2D S pE O Q = C p d??????44 Setup Time Required for an EOQ ? The setup cost required for a given lot size can be derived from the EOQ model as: ? The setup time can be derived from the setup cost, S: 2C ( EOQ ) p dS = 2D p??????SSe tu p T im e = L a b o r r a te45 Example: Setup Time Required A firm wants to determine what the length of the setup time of an operation should be in order to make an production lot size (EOQ) of 50 economical. An analyst has made the following estimates: D = 16,800 units (annual demand) d = 84 units (daily demand rate @ 200 days/yr) p = 140 units (daily production rate) C = $20 (carrying cost per unit per year) Labor rate = $ 46 Example: Setup Time Required ? Setup Cost Required for EOQ = 50 2C ( EOQ ) p dS = 2D p??????2$ 4 2 ( 5 0 ) 1 4 0 8 4 = $ 1 .2 52 ( 1 6 , 8 0 0 ) 1 4 0??? ?????47 Example: Setup Time Required ? Setup Time Required for EOQ = 50 .0833 hours = minutes S $ 1 . 2 5S e tu p Tim e = = = 0 . 8 3 3 h o u r sL a b o r r a te $ 1 5 . 0 0 /h r48 Working Toward Repetitive Manufacturing ? Reduce setup times and lot sizes to reduce inventories ? Change factory layout to allow streamlined flows ? Convert processfocused layout to cellular manufacturing (CM) centers ? Install flexible manufacturing systems (FMS) ? …..more 49 Working Toward Repetitive Manufacturing ? Standardize parts designs ? Train workers for several jobs ? Implement preventive maintenance (PM) programs ? Install effective quality control programs ? Develop an effective subcontractor work 50 Benefits of JIT ? Inventory levels are drastically reduced: ? frees up working capital for other projects ? less space is needed ? customer responsiveness increases ? Total product cycle time drops ? Product quality is improved ? Scrap and rework costs go down ? Forces managers to fix problems and eliminate waste .... or it won’t work! 51 WrapUp: WorldClass Practice ? Focus on timebased petition to capture market share ? JIT method to reduce ordertodelivery cycle ? Prerequisites must be present to successfully implement JIT ? behave like repetitive manufacturing ? stable schedules 52 End of Chapter 12
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