# 6.8.3 Scenario: Line Balancing — Harmonizing the Content of Work

### Intended learning outcomes: Present the routing sheets for parts production out of sheet metal of three products. Explain possible ways for line balancing through harmonizing the content of work.

Figure 6.8.3.1 shows a possible routing sheet for parts production out of sheet metal. Three different products are produced: items 1, 2, and 3. All have a similar routing sheet. For the different operations, the number in the table is the operation time, and the number in parentheses is the setup time.

Fig. 6.8.3.1        Harmonizing the content of work: routing sheets for three products.

In accordance with the discussion in Section 6.2.3, assume a duration of one unit of harmonized content of work of 12 time units. The task is to perform measures to change lead times of operations, chosen from the various possible measures to line ba­lance or harmonize the content of work listed according to Figure 6.2.3.3.

a. Suppose that the first two operations can be combined into one (why is this a feasible assumption?). Item 3 seems — at first glance — to fit quite well into three units of harmonized content of work. Thus, according to the first one of the measures listed in Figure 6.2.3.3, try to change lot sizes of items 1 and 2 (use the empty columns in Figure 6.8.3.1), to obtain for each of them a total operation time on the order of 36 units of time.

Solution: There are machines that perform both operations in one step (e.g., laser-cutting machines). Changing the lot size for product 1 to 200 results in a total operation time of 36, with 18 units of time for setup. Furthermore, the length of the combination of the two first operations is now 10 (or even less, due to complete processing), and this fits well into one unit of harmonized content of work. Changing the lot size for item 1 to 100 would result in a total operation time of 27, with 18 units of time for setup. Thus, a batch size of 200 is the better choice. In addition, changing the lot size for product 2 to 25 results in a total operation time of 31, with 10 units of time for setup. Again, the combination of the two first operations fits well into one unit of harmonized content of work, its total length being 11.

b. Is it possible, in practice, to combine the last two operations into one, fitting them into one unit of harmonized content of work?

Answer: Yes. Testing and preassembly can be done at the same physical work center. Furthermore, with a lot size of 200 for item 1, the combination of the two last operations would fit well into one unit of harmonized content of work.

c. For item 1, the third and fourth operations do not fit into a unit of harmonized content of work, despite significant changes to the batch size. What other possible measures listed in Figure 6.2.3.3 could be implemented?

Answer: Considering the very small run time per unit, the bending operation seems to be very simple (also, the second operation, pressing, appears to be rudimentary, as compared to the process for item 2). Thus, it might be possible to purchase sheet metal that is already profiled (bent). Another solution would be to combine this short process into the same unit of harmonized content of work together with cutting and pressing, using a dedicated (simple, but cheap) machine that could be installed not at work center C, but close to work center B.
Surface treatment is most likely a subcontracted process. This is probably the reason behind the long setup time, which may actually reflect transportation time rather than setup time at the supplier’s site. If so, why not look for a faster transportation vehicle or for a sub¬contractor in greater geographical proximity to the factory?

d. After implementing all these measures, are there still problems?

Answer: Yes. For product 1, setup time is now 50% of the operation time. If setup time is not reduced significantly with the measure in point c, then additional measures must be found to reduce the setup time (e.g., by implementing SMED techniques).