Understanding revisions is important to using 4G:PLM effectively. This topic can be very confusing, so this section provides a detailed example of how it works.
When an item is created, it is in a preliminary state. No change order is necessary to do this, and the item's revision gets a temporary value of „0“, i.e. it is an introductory revision. At this point, it is freely editable and attachments can be added, removed or modified. The preliminary part is only relevant for engineering at this point (Step 1 in the illustration below – part number 4711). As it has not been released with a change order, it is considered a “pending“revision.
Figure 3.9: Understanding Revision
In the above example, an engineer creates an ECO and releases part 4711 to target, Production and target revision “A“. It is considered a „released revision“. Now, it should no longer be able to be edited. For further notes on what file attachment operations are possible and when, please see the separate section on incorporation. If another engineer creates another ECO with target phase „Production“ and target revision „B“, then we see the result in step 2: revision A remains the released revision, but revision B has a preliminary because the ECO has not yet been released.
In step 3, the engineer releases the ECO from step 2. This causes revision B assume the phase “Production“. Revision A retains the Production phase, but is now superseded. If an engineer creates a change order for a revision C, then that revision C will be preliminary. Note that the grey revision is retained in the database for historical information, but is no longer of interest to manufacturing. The green revision in production is the revision that manufacturing will actually build, whereas the preliminary yellow revision is of interest only to engineering while they are doing their design work. The green revision is sometimes called the „production revision“, „current revision“ or „latest released revision“, and is the one that should be shown in bills of material where the part is used.
Step 4 merely illustrates that this process can be repeated arbitrarily many times, and that the number of superseded revisions increases each time. Finally, step 5 illustrates how a part may be phased out of use in manufacturing by issuing an MCO. For the MCO, Manufacturing Change Order, there is no change in revision, but the latest revision changes its phase.