Just in Time

Chapter 9

Vollmann, Berry, Whybark, Jacobs

JIT in MPC

Major elements of JIT

JIT impact on MPC

The Hidden Factory

JIT Building Blocks in MPC

Major Elements of JIT – Definition

Minimize waste in manufacturing• Time, energy, material, and errors

The pursuit of• Zero inventories

• Zero transactions

• Zero disturbances (routine execution of schedules).

JIT Examples

Elimination of discrete manufacturing batches in favor of production rate goals,

Reduction of WIP inventories,

Production schedules that level capacity loads and keep them level,

JIT Examples (Cont.)

Mixed MPS where all products are made more or less all the time.

Visual control systems where the workers build the products and execute the schedule without a lot of paperwork.

Direct ties to vendors who deliver quality products frequently(?).

Physical System Changes

Set-up time reduction and drive towards constantly smaller lot sizes (EOQ).

Improved quality through process improvement to avoid work stoppages of the flow line (no defects goal – kaizen).

Total Preventative Maintenance Poka-yoke (fool proofing)

Physical System Changes

Group the equipment for cellular manufacturing (this minimizes travel distances and inventories between machines). “U” shaped layout.

Cells increase worker interaction (involvement) and reduce material handling. Increased cross training makes capacity more flexible.

JIT Benefits

Mfg. throughput time reductions. Less distance traveled. Reduced transactions Simplified MPC systems Reduce changeover times. Greater responsiveness to market

demand.

JIT Benefits

Inventory reductions Labor cost reductions More satisfied/cohesive workers. Better team working. Space reduction (only if). Quality cost reductions. Quality improvements

JIT Impact on MPC

JIT reduces the number of parts planned and the number of levels in the BOM.

JIT makes MPC work at the level of assemblies rather than at detailed planning.

MPS will use relatively level capacity loading (rate based – so many units per hour (or day)).

JIT Impact on MPC

Lead times are reduced so that inventories that used to be used to provide inventories in anticipation of customer orders (made-to-stock) are now doing MTO or ATO & better able to respond to customer orders.

This in turn can affect Demand Management.

JIT Impact on MPC

In JIT orders move through the plant so quickly that there is no need to have a complex production activity control.

In JIT the vendor is paid depending on the number of products that are completed each time period.

The intent is to design manufacturing cells so the goods follow through routinely. Simple systems are employed by shop people.

The Hidden Factory (one makes things and the other paper transactions).

Logistical transactions

Balancing transactions

Quality transactions

Change transactions

Logistical transactions

Includes ordering, execution, and confirmation of materials moving from one location to another.

It includes the costs of personnel, in receiving, shipping, expediting, data processing, accounting, error follow up.

Under JIT the goal is to eliminate as much of this as possible. If flow is simplified, fast, and guaranteed there is no need for paperwork.

Balancing Transactions

Includes transactions needed for production control, purchasing, master scheduling, forecasting, and customer order processing.

They are about 10-20% of the total manufacturing overhead costs.

JIT offers the opportunity to reduce these costs.

Quality Transactions

Includes identification and communication of specifications, certification that other transactions have taken place, and recording of backup data.

JIT with closer coupling of production and consumption has faster quality monitoring and response capability.

Change Transactions

Including engineering changes and all those that update MPC systems such as routings, bill of materials and specifications.

Attacks on transactions

Find ways to reduce the number of transactions.

Stability will help and JIT is based on stabilized operations.

Automate the transactions (bar coding, RFID).

Role of ERP?

JIT OBJECTIVES

Zero inventories Zero Lead Time Zero Failures Flow Process Flexible Manufacture Eliminate Waste

Fig. 9.4

Impact of Product Design

If the handle base is redesigned the handle base becomes a common part and the ring placement is common between the two handle models. Fig9.13

The only difference would be the choice of handle parts.

BOM is simplified Fig 9.15

Process Design

It may now be possible to use the same equipment to attach both kinds of plastic handles to the handle base.

Perhaps a cell may be formed Fig 9.14 Observe that inventory is smaller

(containers). Fig 9.14 There seems to be slack capacity. Fig

9.14

BOM Implications

Number of parts has gone down. Product structure tree now looks slimmer Handle assemblies have ceased to exist

as part of the structure. Handle assembly (Part 137) can exist as

a phantom assembly.