The Lean Anthology

35

Chapter 4

Achieving Single- Piece Flow

BELINDA, BAGS, AND BATCHES

Around 2:00 p.m. on Thanksgiving Day,

as guests began to arrive, Belinda Daniel

took the turkey, glistening and brown,

out of the oven. She had left just enough

time to whip up some gravy on the

stovetop and warm up the mashed pota-

toes and sweet potato casserole that had

been cooked the day before.

As her friends and family entertained

themselves and waited for mealtime,

Belinda peered into cabinets that had

not been cleaned out in over a year and

failed to find any flour for the gravy. All

the activity was starting to give her a

headache, so she took some ibuprofen.

“I need to go to the store,” she announced to no one in particular. “I’ll

be right back.”

Belinda Daniel takes a break from her

Thanksgiving preparations and her

houseguests to pop out to the grocery

store for a few last- minute items. While

checking out at the self- checkout line,

she thinks about different designs for

checkout lines and their effect on cus-

tomer wait times. She considers how to

determine the quantity that should be

processed at the same time.

As you read Belinda’s story, think

about the different reasons that might

exist for identifying an optimal batch

size, and the relationship between

batch size and wait time. What do

stores consider when designing check-

out lines?

36 THE LEAN ANTHOLOGY

At the grocery store, many other people were taking short breaks from

their cooking duties to pick up last- minute items. Belinda grabbed a

basket, found the flour and some detergent, and pondered whether to

use one of the traditional grocery store lines or a self- serve express

lane. She wasn’t in a hurry to return to her kitchen, but the store was

warm and noisy, and she wanted to get back outside to the cooler air to

help her headache.

The lines were longer at the self- serve stations, but each customer had

only one or two items. Although the full- service lines were shorter,

the customers in them had carts that were full to overflowing. Belinda

went with a line for one of the six self- checkouts.

While Belinda waited, she watched a few of the full- service lines to see

if people in those lines got through before she did. One line lacked a

bagger, so checked cans and cartons slid up against bread and lettuce.

At another line, an elderly man squinted at the total above the cash

ACHIEVING SINGLE- PIECE FLOW 37

register and then began writing in his checkbook, at the same time

chatting with the clerk. She could see the light flashing at another cash

register, indicating the need for a price check. Meanwhile, six people

ahead of her in her self- checkout line had finished with the process.

As Belinda had watched her line and the other self- checkout lines, she

had seen delays from time to time as customers had trouble entering

their frequent- shopper numbers or finding the barcodes on items. A

store employee helped customers get through the self- checkout sta-

tions. Belinda felt that she had chosen the right service line.

She had also been watching the store’s bagging system. At other stores,

self- serve checkout stations used a half- length conveyor belt system;

customers scanned their items and then placed them on the belt.

Scanned items moved along the belt, where they stayed until the cus-

tomer paid for them and then placed them in bags.