Question

Explain how the production schedule is developed and communicated to the shop-floor in a Just-in-Time (JIT) manufacturing system. Q. B8 (a) (10 marks) Define kanban as it is understood in JIT systems and explain the role and operation of a conveyance or C kanban in the production system. (b) (6 marks) (c) Data for a particular part that is controlled by a two-card kanban system on a JIT feeder line is as follows: daily demand: 500 units average waiting and moving time: 2 hours per standard container average processing time per container: 30 minutes Due to uncertainty within the process and fluctuating demand, the system has a safety stock factor of 20%. A standard container holds 30 units. The company operates an 8-hour working day. Determine how many standard containers are needed to operate the system. Briefly explain how kanbans can facilitate a process of inventory reduction. (4 marks) Note: k (number of standard containers) -

Answer 1

There are two methods of scheduling followed in JIT system – a) Forward Scheduling   b) Backward Scheduling

Forward scheduling Let’s take an example for forward scheduling: An order has been received from a customer who wants products in three shipments of 2000 units delivered on 5th Nov, 7th Nov and 8th Nov. Let's schedule this with a production scheduler. Scheduler Diagram below indicates JIT production schedule: The sales production item (JIT item) production schedule. The three orders are assigned so that each of them finishes precisely on their respective specified due dates to become a JIT schedule.

Backward scheduling The schedule is made so that the order's final process is assigned so that it finishes on the LET (due date) with the previous processes being assigned in order to pack in towards the right. Because of this, we know when we should start the orders so that they finish just before the due date. In this way we can do a JIT schedule. In this way, the result of the scheduling is like below Diagram. The sales production item (JIT item) orders are assigned so that they finish exactly on their respective due dates. Prospective production item orders are assigned to the remaining free areas available for Machine1

b) The Kanban System was developed to achieve objective that include reducing costs by eliminate scrap, quick change alignment and best extraction of quality work.

Withdrawal (Conveyance) Kan-ban The main function of a withdrawal Kan-ban is to pass the authorization for the movement of parts from one stage to another. Once it gets the parts from the preceding process and moves them to the next process, remaining with the parts until the last part has been consumed by the next process. The withdrawal Kanban then travels back to the preceding process to get parts thus creating the cycle. A withdrawal Kanban usually carries the following information:

• part number                                        - routing process
• part name                                           - name of the next process
• lot size                                              - name of the preceding process
• location of the next process - container type and capacity

3. Number of Containers required = DT(1+x)/C    D: Demand per unit of time   T: Lead time   C: Container capacity X: Buffer, or safety factor--Following through above formula 40 Containers required.