Leveling: Be More Like the Tortoise Than the Hare 155

Chapter 7. Leveling: Be More Like the Tortoise Than the Hare 155

through C are produced every day (ED), and items D through F are produced every other day (EOD). Items G through J are produced every four days (E4D— yes, yes, we know the goal should be to produce every part every day, but we are not there yet!).

One potential pattern is shown in Table 7-2. The daily requirement of 1,318 was adjusted slightly to 1,325 just to round the numbers. As we said, this is irrelevant because there is variation in the quantity of the “Other” items. This pattern is more evenly spread and allows for production of some “Other” items daily, but on some days the quantity of the “Other” items is low. If average order sizes of “Other” items are typically greater than these amounts, another pattern may be considered.

Table 7-3 shows an alternative pattern that groups more of the ED and EOD items on the same day. The ED items are a given—they run every day. The EOD and E4D may be changed to suit the needs of the process. For example, the EOD items could all be produced on the same alternating days as in this example. There are other potential patterns as well. The objective is to achieve the best level vol- ume across the pattern by row—leveled by individual item over a time window, and down the pattern by column—total volume, and mix per time increment (pitch). The production sequence is defined by following the patterns (A through J) in the order specified. The level across the time period is within a defined

A (ED) 250

250 250 250 B (ED)

220 220 220 C (ED)

210 210 210 D (EOD)

0 256 E (EOD)

0 250 0 250 F (EOD)

0 150 G (E4D)

0 0 0 240 0 0 H (E4D)

0 0 0 180 I (E4D)

0 0 0 J (E4D)

1,325 1,325 1,325 ED = every day; EOD = every other day; E4D = every four days. Table 7-2. Possible Leveled Production Pattern

T HE T OYOTA W AY F IELDBOOK

A (ED) 250

250 250 250 B (ED)

220 220 220 C (ED)

210 210 210 D (EOD)

0 256 E (EOD)

250 F (EOD)

0 150 G (E4D)

0 0 0 240 0 0 H (E4D)

0 0 0 180 I (E4D)

0 0 0 180 0 0 J (E4D)

1,325 1,325 1,325 ED = every day; EOD = every other day; E4D = every four days. Table 7-3. Alternative Leveled Production Pattern

repeating increment. In our case, the pattern has a four-day repeating sequence and each item is leveled (the totals are equal) every four days. Toyota typical- ly uses a monthly window for leveling, but it is based on a repeating multiple of one day. Note: The main vehicle assembly line has a repeating pattern on a short pitch frequency depending on the particular mix of vehicles produced, but the supporting operations that are producing to a supermarket or “selectivity bank” are producing to a different pattern that is a derivative of the primary pattern.

Notice that in the alternative pattern the total in days one, three, five, and seven exceeds the daily goal. This is not a major problem since the amount is within reasonable limits (normally a maximum of 10 percent). In most cases when working with actual demands, the numbers don’t work out as evenly as this example. For the first attempt, get the numbers as close as possible. After you’ve had the opportunity to produce based on a level schedule, you will gain

a clearer understanding of the true need and will adjust the pattern accordingly.