38 ISE Magazine | www.iise.org/ISEmagazine

Even though they were separated by half a continent and a major

ocean, Alexandria Industries in Minnesota and Bosch Hinges in the

Netherlands were facing exactly the same problems.

Both companies produced a high variety of products in low vol-

umes – Alexandria made aluminum extrusions, and Bosch manu-

factured specialty metal hinges (see Figure 1) – and both had long

lead-times of six to eight weeks. Despite having this large window of time,

both organizations were struggling with late deliveries, which required daily

expediting efforts in attempts to get jobs out on time. For several years, the two

enterprises had tried a plethora of manufacturing and control strategies, but

none had alleviated this ongoing problem.

Then, although separated by some 5,000 miles, management at each com-

pany independently decided to implement POLCA, an acronym for paired-

cell overlapping loops of cards with authorization. At that time, POLCA was a

relatively novel idea. Within a few months, both companies had reduced their

quoted lead-times by more than 50 percent, and even with this smaller time

window they were able to achieve near-perfect on-time delivery.

With the shorter lead-times and excellent delivery record, combined with

their reduction of expediting activities and costs, Alexandria and Bosch expe-

rienced signiﬁcant increases in sales as well as proﬁtability. And thus it was that

these two companies joined the ranks of the pioneers of POLCA in both the

new world and the old one.

POLCA picks the right job at the right time

So why was POLCA able to achieve in a relatively short time what these two

companies had been unable to accomplish for many years? The answer to this

question contains important insights for the industrial and systems engineering

community, and we will build up to the complete answer by the end of this

article.

One particular insight is worth mentioning right off the bat. ISE profession-

als have expertise in the design of systems, as clearly indicated in the profes-

sion’s name. These systems are often based on sophisticated mathematical mod-

els developed by the industrial and systems engineering community. However,

implementation experiences with POLCA have shown that another area of

ISE’s expertise is critically important – namely the human factors and socio-

technical aspects of a system’s design. This article will show that POLCA is

actually a fairly simple system, and the success of POLCA is strongly linked to

the “people side” of system design and implementation.

The terms used in the full name of the tool (again, paired-cell overlapping

loops of cards with authorization) are based on speciﬁc features of the system,

explained soon.

POLCA helps jobs dance

through your factory

Visual control system dramatically cuts lead-time by matching

cards against production capacity

By Rajan Suri

October 2018 | ISE Magazine 39

40 ISE Magazine | www.iise.org/ISEmagazine

POLCA helps jobs dance through your factory

First, let’s understand what POLCA

does for a company. POLCA is a card-

based visual control system that manages

the ﬂow of jobs through the shop ﬂoor:

At each of the main operations, it con-

trols which job should be worked on next

in order to meet delivery targets. Speciﬁ-

cally, it ensures that upstream operations

use their capacity effectively by working

on jobs that are needed downstream,

while at the same time preventing ex-

cessive work-in-process (WIP) buildups

when bottlenecks appear unexpectedly.

POLCA is particularly effective in

high variability environments where the

variability arises for external reasons such

as unpredictable demand, many different

types of orders and dynamic changes in

customer requirements, as well as inter-

nal reasons such as changes in equipment

and labor status and other day-to-day

conditions on the factory ﬂoor.

The context for POLCA stems from

the fact that in recent years manufactur-

ing companies have experienced signiﬁ-

cant market pressure to reduce lead-times

and be more responsive to customers.

Along with this, order sizes are getting

smaller, and companies are seeing more

orders for individually customized prod-

ucts.

To reduce lead-times signiﬁcantly,

companies are reorganizing their shop

ﬂoors into cells. A cell is a collection of

equipment along with a team of people

responsible for the cell’s operation. So,

to satisfy the demand for numerous dif-

ferent small-batch orders or customized

products, companies often need to route

jobs through various combinations of

cells. This leads to the ﬁrst feature of POLCA, which we will

explain via a simple manufacturing example.

Loops of cards between

pairs of cells

For our example company, let’s say certain types of jobs need

to go from the fabrication cell “N” to an assembly cell “S” and

then to a testing cell “T.”

In POLCA, if jobs ﬂow between any two cells, these cells

are connected by a POLCA loop. Thus, as shown in Figure 2,

there will be a loop from N to S and one from S to T. Each

loop contains a number of cards called POLCA cards that cir-

culate in the loop. The cards are speciﬁc to each loop and are

labeled based on the origin and destination cell.

For the two loops in the ﬁgure, they would be called N/S

cards and S/T cards. To support the visual nature of the sys-

tem, each cell is assigned a color, and the cards are color-coded

as also shown in the ﬁgure. This allows people to quickly as-

sociate a card with the origin and destination cells.

The function of the POLCA cards is to signal the availabil-

ity of capacity at destination cells. This is how the cards work.

When cell N is scheduled to start a job that next is destined for

cell S, then the cell N team needs to have an N/S card avail-

able in order to launch the job into their cell. After the job is

FIGURE 1

Unhinged deliveries

Bosch Hinges was having a hard time getting their specialty metal hinges, some of

which are shown here, out the door in a timely fashion.

FIGURE 2

Cards against capacity

POLCA cards travel in loops between pairs of cells. The color-coded cards help regulate

workﬂow and manage capacity.

Fabcell

Assemblycell

Test cell

S/Tloop

N/Sloop

October 2018 | ISE Magazine 41

launched, the N/S card is kept with this

job or with its paperwork to signify that

the card is associated with that job.

When cell N completes the job, it sends

the job along with the N/S card to cell S.

The decision-making at cell S regarding

when it can start this job will be discussed

below. For now, let’s say cell S does start

this job. It also keeps the N/S card with

the job. Only when cell S ﬁnishes work-

ing on this job does it send the N/S card

back to cell N.

This explains the ﬁrst key feature of

POLCA – the card coming back from

cell S essentially conveys the message to

cell N: “We ﬁnished one of the jobs you

sent us; you can send us another.” In oth-

er words, a returning POLCA card signi-

ﬁes the availability of capacity in a given

downstream cell.

If you are already familiar with kan-

ban – another card-based control system

with its roots in the Toyota Production

System and now a key part of lean manufacturing – you might

have noticed an important difference between kanban and

POLCA.

Kanban is an inventory signal. When a quantity of parts is

used up, it tells the previous operation to restock that inven-

tory. However, as just explained, POLCA is a capacity signal.

This difference is a major reason why POLCA works better

than kanban for low-volume and custom production. Speciﬁ-

cally, kanban requires you to carry inventory at many interme-

diate stocking points, but for low-volume parts this becomes

inefﬁcient and wasteful. And for custom-engineered parts you

can’t carry inventory in the ﬁrst place – you don’t know what

exactly to manufacture until you have received the order and

the custom engineering has been completed.

But neither of these situations is a problem for POLCA. For

low-volume parts, you will see from the next section that you

only make parts as needed based on demand. And for custom-

ized parts, since POLCA allows routing between any sets of

cells, the routing for a completely new part is treated no differ-

ently than that for a part that has been made before.

Authorization list and decision rules

So how does a cell decide which job to start next?

Based on the due date of a job, manufacturers calculate

authorization dates for each of the cells in the job’s routing

by backward scheduling from the due date using the planned

lead-times for each cell. If the company is using an MRP (ma-

terials requirements planning) system, this is a standard feature

of MRP. Otherwise this can be done easily with a spreadsheet.

These dates are similar to “start dates” for people who use

MRP, but there are some additional rules to follow, which is

why we call them authorization dates instead.

Through sorting the data for all the jobs, manufacturers ob-

tain a list of jobs yet to be processed in each cell. This is called

an authorization list. While this also resembles the “dispatch

list” in an MRP system, there are important differences as you

will see below. The authorization list only contains jobs that

have not yet been launched into this cell, sorted by authoriza-

tion date.

The ﬁrst rule in POLCA is that jobs with a date of today or

earlier are authorized, and jobs with a date of tomorrow or lat-

er are not authorized. Only authorized jobs can be launched.

The list also displays the “next cell” where each job will go

next. This leads us to the main decision-making logic used in

POLCA.

Despite the long acronym, the operation of POLCA is actu-

ally quite simple. When a team is ready to start another job in

its cell, the team just needs to answer three simple questions:

(1) What’s the next job on the authorization list? (2) Has the

material for this job arrived from the upstream cell? (3) Do we

have the right POLCA card for this job?

For example, if the team is in cell N and the next cell for

this job is cell S, then the team needs to have an N/S POLCA

card available. If there is an authorized job on the list and the

answers to questions two and three are “yes,” then this job is

launched into the cell, and the team can start working on it.

If the answer is “no” to questions two or three, then the team

goes back to question one and looks for the next job on the list.

FIGURE 3

Keeping it visual

This POLCA board is used in cell U at Bosch Hinges.

42 ISE Magazine | www.iise.org/ISEmagazine

POLCA helps jobs dance through your factory

In the event that all the authorized

jobs receive a “no” in questions two or

three and there are no more authorized

jobs, the team will not launch any other

production jobs into the cell (even if the

material has arrived and these jobs are in

the schedule for the near future). Instead,

it will engage in activities such as con-

tinuous improvement projects. We will

discuss this later in the article.

To help systematize the answer to

question three, each team has a bulletin

board where it organizes the POLCA

cards available for its cell. This is called

a POLCA board. Figure 3 shows an ex-

ample of a POLCA board used at Bosch

Hinges.

Later, we will explain the beneﬁts that

derive from the combination of using the

POLCA cards, authorization list and the

above decision rules. For now, let us complete the description

of POLCA by explaining the last key feature of the system.

Overlapping loops at intermediate cells

Let’s return to the job that went from cell N to cell S, and let’s

say it needs to go to cell T next.

Each cell must use the POLCA decision rules (the three

questions), so when the job arrives at cell S, the team must

ﬁrst wait till this job is the next authorized job (question one

above). Since the job has arrived at cell S, the answer to ques-

tion two is “yes.” For question three, the team needs to have

an S/T card available. If it does, the S/T card is allotted to this

job and it is launched into the cell.

Remember that the job arrived with an N/S card, and that

card will not be sent back to cell N until the job is ﬁnished.

So while it is being worked on in cell S, this job will have two

POLCA cards with it.

Figure 4 shows an example of a job in process at Bosch

Hinges along with its two POLCA cards. Except in the ﬁrst

and last cells in a routing, a job will always carry two POLCA

cards when it is being actively worked on in any cell.

Continuing with our example, when the job is completed

in cell S, the N/S card will return to cell N, and the job along

with the S/T card will go to cell T. And then the same logic

will repeat at cell T and so on through its entire routing. Note

that at the last cell in the routing, there is no “next cell,” so

question three does not need to be answered.

Operational beneﬁts of POLCA

POLCA has been implemented in many different types of

companies and industries. After implementing POLCA, these

companies have experienced numerous beneﬁts. Now that

you have seen how POLCA works, we can describe these ben-

eﬁts in more detail; knowing how the system operates enables

you to understand why the beneﬁts occur.

First, no complex software implementation is required.

Shop ﬂoor control software such as ﬁnite capacity scheduling

and manufacturing execution systems can be expensive and

take time to implement and customize for a given company.

Factories have been able to implement POLCA quickly and

without a lot of expense.

Second, POLCA ensures effective use of capacity while

also reducing congestion. Let’s return to the job going from

cell N to cell S. Let’s say it is the next authorized job, but the

cell N team does not have an N/S card. Suppose there are

ﬁve cards in the N/S loop, as shown in Figure 2. (POLCA

theory provides a formula for calculating the number of cards

in a given loop.) The fact that the team does not have any

N/S cards means that there are ﬁve jobs already at cell S,

or on their way to cell S, and none of those jobs have been

completed by cell S.

Working on yet another job would result in more jobs pil-

ing up for cell S. Instead, the POLCA rules would make the

team skip this job, and let’s say the next authorized job does

have the appropriate POLCA card available, then the POLCA

rules would redirect cell N to work on this job. Hence the

team would work on a job destined for a cell that could beneﬁt

by receiving this job.

Thus, we see that the rules accomplish two important goals:

Avoiding more congestion where there’s a bottleneck and en-

suring that upstream cells work on jobs that will continue to

ﬂow downstream instead of working on jobs that will just end

up sitting at a bottleneck.

Next, POLCA works well for high-mix, low-volume and

FIGURE 4

Cards can carry your production

This shop packet at Bosch Hinges shows two POLCA cards associated with a job

while it is in cell K. The job came from cell U carrying the U/K card on the left, and

since it is going to cell V next, it needed the K/V card on the right in order to be

launched into cell K.

October 2018 | ISE Magazine 43

customized production. Since demand is moving more and

more in this direction, it is important to have a system that can

deal with this environment.

Materials requirements planning (MRP) systems have dif-

ﬁculty coping with the variability in a high-mix, low-volume

company. As documented in the literature, the MRP logic can

result in lengthening lead-times, late deliveries and an increas-

ing cycle of rush jobs.

Also, kanban systems, while simple, are not appropriate for

low-volume or custom production as explained above. In-

dustry case studies show that POLCA has provided excellent

results in such environments by eliminating expediting and

achieving near-perfect levels of on-time delivery.

POLCA is a visual system. There is strong belief in manage-

ment circles today that visual systems can be very effective in

keeping day-to-day operations on track. Simple visual systems

are also in keeping with sociotechnical systems design. The

POLCA system aligns well with these principles.

The system builds on existing structures and systems. POL-

CA builds on the cell structure that is becoming more widely

used, plus it supports better coordination between cell teams.

While POLCA does not require an MRP system, if compa-

nies already have an MRP system in place, POLCA seamlessly

complements this system.

POLCA rules provide a formal framework for continuous

improvement activities. As explained in the rules above, if all

the authorized jobs receive a “no” in step two or step three,

the team will not launch any other production jobs. Instead,

it will engage in improvement activities such as putting time

into cross-training, studying a setup in order to come up with

ideas for setup reduction, engage in preventive maintenance

tasks and so on.

Today’s manufacturing strategies place great importance on

continuous improvement activities, and such activities form

the core of jobs for many ISE professionals. But the truth is, if

we just keep launching jobs to keep people busy, when can a

team have time to engage in any of these improvement activi-

ties? When implementing POLCA, teams can be coached that

whenever their production activity is stopped due to POLCA’s

decision rules, they can use these periods of time productively

for improvement.

And ﬁnally, POLCA builds on the capabilities of humans

in the system. Many so-called “optimum” scheduling systems

lose sight of the fact that such systems are deployed by people,

and these people need to buy in to the system and support it.

This oversight has resulted in ineffective or even failed imple-

mentations.

In contrast, experience with many companies has shown

that people on the front line like using POLCA; they ﬁnd it

simple and easy to understand, support its implementation and

help to ensure that it continues to work well.

Success through simplicity

Sophisticated systems can fail in their implementation if they

don’t get buy-in from people on the front line. Industry appli-

cations have shown that POLCA accomplishes with simplicity

what complex systems offer but are often unable to achieve.

Having the full support of shop ﬂoor personnel is key to

POLCA’s success. Feedback from one company included the

statement, “It’s the folks on the shop ﬂoor that are singing the

praises of POLCA.”

The ﬁnal proof of success, of course, comes from the

bottom-line results for companies that have implemented

POLCA: Shorter lead-times, signiﬁcant savings in expedit-

ing activities and costs and an excellent delivery record. As

stated by Fried Kaanen, president and CEO of Bosch Hinges:

“Implementing POLCA was revolutionary for our company.

Now our delivery time is revolutionary for our customers.” 

Rajan Suri is emeritus professor and founding director of the Center

for Quick Response Manufacturing (QRM) at the University of

Wisconsin-Madison. He is author of several books on QRM and re-

cently published the book The Practitioner’s Guide to POLCA:

The Production Control System for High-Mix, Low-Vol-

ume and Custom Products, which includes numerous POLCA

case studies.

Shorter lead-times satisfy customers

Customers, whether they are end-users, upstream departments or other businesses,

are demanding shorter lead-times across the board. As described in the main story,

POLCA can help.

Writing for IndustryWeek, Larry Fast also suggests that enterprises check that their

major suppliers have plans to reduce cycle times in their plants – the quickest way to

reduce lead-times. If they don’t, perhaps you can volunteer one of your resources to

work with a supplier engineer to ﬁnd a suitable corrective action.

A 35-year veteran of the wire-and-cable industry, Fast also suggested that

organizations check with their suppliers’ ﬂex capacity options, which would indicate

how quickly they can respond to increased demand.