ISQA 459 Mellie Pullman

1

JIT can be defined as an integrated set of activities designed to achieve high-volume production using minimal inventories (raw materials, work in process, and finished goods).

JIT also involves the elimination of waste in production effort.

JIT also involves the timing of production resources (e.g., parts arrive at the next workstation “just in time”).

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Elimination of waste Efforts concentrated on shop floor

Respect for peopleQuality improvement focus

3

(1) Waste from overproduction

(2) Waste of waiting time

(3) Transportation waste

(4) Inventory waste

(5) Processing waste

(6) Waste of motion

(7) Waste from product defects

4

5

Customers

Sub

Sub

Fab

Fab

Fab

Fab

Vendor

Vendor

Vendor

Vendor

Final Assembly

6

Final Assembly

CoordinationSystem Integration

7

A

B

C

A

C

B

Sporadic and Infrequent

Deliveries from Individual Suppliers

8

A

B

C

ABC

Regular and Frequent

Deliveries from Many Suppliers

Using Departmental Specialization for plant layout can cause a lot of unnecessary material movement.

9

Saw Saw

Lathe PressPress

Grinder

LatheLathe

Saw

Press

Heat Treat

Grinder

Revising by using Group Technology Cells can reduce movement and improve product flow.

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Press

Lathe

Grinder

Grinder

A

2

BSaw

Heat Treat

LatheSaw Lathe

PressLathe

1

11

Not uniform Jan. Units Feb. Units Mar. Units Total

1,200 3,500 4,300 9,000

Uniform Jan. Units Feb. Units Mar. Units Total

3,000 3,000 3,000 9,000

Suppose we operate a production plant that produces a single product. The schedule of production for this product could be accomplished using either of the two plant loading schedules below.

How does the uniform loading help save labor costs?

or

Company produces three products with a mixed model assembly line. Operates 16 hours

per day for 250 days/yr.

Determine the mixed model MPS for a daily batch.

Determine minimum batch MPS and the mix schedule for a day.

Products Forecasts (year)

1 20,000

2 10,000

3 5,000

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    #1 #2 #3

Year Forecast   20000 10000 5000

Daily Batch divide by 250 80 40 20

Hourly Batch divide by 16 5 2.5 1.25

Minimum Batch MPS   4 2 1

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For every unit of #3 (minimum batch), we need twice as many #2 and 4 timesAs many #1 so for minimum batch:Produce during each day produce #1,1,1,1,2,2,3 - repeated 20 times

Company produces four products with a mixed model assembly line. Operates 8hours per

day for 250 days/yr. Determine the

mixed model MPS for a daily and hourly batch .

Determine mix schedule for a day.

Products Forecasts (year)

I 500

II 1500

III 4500

IV 6000

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15

• Management philosophy• “Pull” system though the plant

WHAT IT IS

• Employee participation• Industrial engineering/basics• Continuing improvement• Total quality control• Small lot sizes

WHAT IT REQUIRES

• Attacks waste• Exposes problems and bottlenecks• Achieves streamlined production

WHAT IT DOES

• Stable environment

WHAT IT ASSUMES

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Work in

process

queues

(banks)

Change

orders

Engineering design

redundancies

Vendor

delinquencies

Scrap

Design

backlogs

Machine

downtime

Decision

backlogsInspection

backlogs

Paperwork

backlog

Example: By identifying defective items from a vendor early in the production process the downstream work is saved.

Example: By identifying defective work by employees upstream, the downstream work is saved.

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Storage Part A

Storage Part AMachine

Center Assembly Line

Material Flow

Card (signal) Flow

Withdrawal kanban

Production kanban

Setting up a kanban system requires determining the number of kanbans (or containers) needed.

Each container represents the minimum production lot size.

An accurate estimate of the lead time required to produce a container is key to determining how many kanbans are required.

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19

C

SdL

k

)(1

container theof Size

stockSafety timelead during demand Expected

k = Number of kanban card sets (a set is a card)d = Average number of units demanded over some time periodL = lead time to replenish an order (same units of time as demand)S = Safety stock expressed as a percentage of demand during lead timeC = Container size

A switch assembly is assembled in batches of 4 units from an “upstream” assembly area and delivered in a special container to a “downstream” control-panel assembly operation.

The control-panel assembly area requires 5 switch assemblies per hour.

The switch assembly area can produce a container of switch assemblies in 2 hours.

Safety stock has been set at 10% of needed inventory.

20

21

3or ,75.24

5(2)(1.1))(1

container theof Size

stockSafety timelead during demand Expected

C

SdL

k

Always round up!

Link operations

Balance workstation capacities

Re-layout for flow

Emphasize preventive maintenance

Reduce lot sizes

Reduce setup/changeover time

22

Standard product configuration

Standardize and reduce number of parts

Process design with product design

Quality expectations 23

Level payrolls

Cooperative employee unions

Subcontractor networks

Inverted pyramid management style

Small group involvement activities

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Worker responsibility

Measure SQC

Enforce compliance

Fail-safe (Poke-yoke) methods

Automatic inspection

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Damaged parts Missing parts Reversed parts Wrong parts Wrong size or shape Wrong chemical

properties Wrong physical

properties Wrong item shipped Wrong label Wrong package Damaged finished

product

Omitting a part Omitting a process Performing a process

incorrectly Performing a process on the

wrong part Performing a process in

improper environmental conditions

Performing the wrong process

Setting up equipment incorrectly

Setting up a work piece incorrectly

Adjusting equipment incorrectly

Tooling set up incorrectly Tooling adjusted incorrectly Installing wrong part Installing part incorrectly 26

DEFECTSDEFECTS MISTAKESMISTAKES

Reduce lead times

Frequent deliveries

Project usage requirements

Quality expectations

27

Look for other areas where inventory hides

Stores

Transit

Carousels

Conveyors

28

29

• MRP is a planning system that MRP is a planning system that does not do detailed shop floor does not do detailed shop floor schedulingscheduling

• MRP requires fixed lead times MRP requires fixed lead times which might actually vary with which might actually vary with batch sizebatch size

• JIT excels at rapidly moving small JIT excels at rapidly moving small batches of material through the batches of material through the systemsystem

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1.1. MRP “buckets” are reduced to daily or hourlyMRP “buckets” are reduced to daily or hourly

• The most common planning period (time The most common planning period (time bucket) for MRP systems is weeklybucket) for MRP systems is weekly

2.2. Planned receipts are used internally to sequence Planned receipts are used internally to sequence productionproduction

3.3. Inventory is moved through the plant on a JIT Inventory is moved through the plant on a JIT basisbasis

4.4. Completed products are moved to finished goods Completed products are moved to finished goods inventory which reduces required quantities for inventory which reduces required quantities for subsequent planned orderssubsequent planned orders

• Back flushing based on the BOM is used to Back flushing based on the BOM is used to deduct inventory that was used in productiondeduct inventory that was used in production

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• Used in repetitive operationsUsed in repetitive operations

• MRP plans are executed using JIT MRP plans are executed using JIT techniques based on “pull” techniques based on “pull” principlesprinciples

• Flows are carefully balanced with Flows are carefully balanced with small lot sizessmall lot sizes

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• Items used by many products are Items used by many products are held in a common area often called held in a common area often called a supermarketa supermarket

• Items are withdrawn as neededItems are withdrawn as needed

• Inventory is maintained using JIT Inventory is maintained using JIT systems and proceduressystems and procedures

• Common items are not planned by Common items are not planned by the MRP systemthe MRP system