Improving Job Methods with TWI

Why it matters

Before teaching a job, you need to examine whether the current method carries unnecessary load. Asking why a tool has to be searched for at all can give a more lasting result than speeding up the search. The job methods improvement part of the TWI (Training Within Industry) approach carries this questioning down to the details of the task. Linked to method study, it records the work done, questions the reasons for it, generates alternatives and tests the result. The employee's job knowledge is one of the main sources of this review. However, a good idea does not count as the new standard without evidence from practice. The improvement claim must be shown under the same start, end and acceptance conditions; it does not rest on one operation part that merely looks shorter.

For each step, you first ask what is done, then why it is necessary. After that, place, sequence, person and manner of doing are examined. The purpose of these questions is not to fill in the boxes of a chart. An unnecessary activity can be eliminated; necessary activities can be combined, resequenced or made easier to carry out when appropriate. These options are not mixed up. When separate jobs are written under one heading, the number of rows may fall while the real load stays the same. Conversely, using a safe fixture may increase the number of rows while reducing the total load. The result is therefore not judged by the number of steps alone; duration and acceptance conditions are also kept visible.

Unnecessary motion load does not mean that every piece of non-value-adding work can be removed. A check that verifies the conformance of the product, an operation that holds the part securely or a record that ensures traceability may be necessary. Their durations can be examined separately; but their necessity does not disappear by looking at their durations. If the check is to be assured by another arrangement, it is tested what the new arrangement verifies, under which condition and how. Relying on the employee's attention does not replace a physical safeguard. Removing the check and leaving the cost of errors out of the calculation is not a method gain either. In this lesson the time difference is an input to a choice; it is not a superiority score that invalidates the acceptance conditions.

Removing a motion does not always shorten the cycle by the same amount. If jobs run simultaneously, the elapsed time is calculated separately. Transferring replenishment to another person does not eliminate the total human load. While the time at the work station falls, the time of the support work may rise. For this reason the scope of both the tested part and the support work is stated. The comparison must not confuse the learning period with settled practice. After the new tool or layout has been learned, safe and repeatable practice is observed. The job breakdown and the instruction content are updated for the chosen method; running the old instruction and the new arrangement together may cause the gain to be lost in a short time.

Formula