Reason Tree¶

A reason tree is a structured way to show the various states possible for a machine or line. It helps to identify and address the primary drivers of downtime in order to monitor and improve the performance, for example, delays in supply or technical issues. A detailed reason tree is required to enable this type of examination.

Only in rare cases can one reason that a tree covers all machine or line states in a factory. Reason trees are typically built for a machine type or line of machines, so Insights Hub OEE allows you to add multiple reason trees.

The structure of a reason tree can be decided by the user based on the requirements. Typically, a reason tree contains more reasons than the number of states logged automatically by the machine through PLC codes. This enables the user to modify the original reason if, for example, they have more details on the root cause. For instance, the machine reports an emergency stop, but in reality, it was not caused by the machine itself, but the operator had pushed the emergency button. Then, in the post-production analysis, you can assign the right reason to the registered event and improve the data accuracy.

A reason tree is built out of the following categories:

• Time Category (described in the Time Model section)
• State (describes the machine state)
• Reason Layer 1
• Reason Layer 2
• Reason Layer 3
• Reason Layer 4

The reason tree time categories are fixed from the time model and cannot be modified here is the user assigns high-level machine states to these time categories. This could be, for example, run, idle, stop, emergency, end of shift, etc. The further details, which describe the machine state, are then built through the tree structure and the different reason layers.

The following image shows an example of the reason tree:

The sections for Production time, Planned Stop and Downtime can be collapsed or expanded so you can focus on each separately. In the example above, just the Downtime section is shown. Here you can see the tree structure of the downtime reasons. There are 7 Downtime categories, each can have one or more states and then multiple reason layers. For example, "Unplanned Downtime" is the time category, the state is "Stop" and "Supply Chain" is in reason layer 1. The next level of detail is “no supply” - this is the most detailed level of these downtime reasons. For the "Conveyor Belt" reason, the next layer splits into two: the problem could be either a mechanical or an electrical issue. In the example, there is also another reason layer, attached to the mechanical reason, that shows there is an issue with the "Bearing". The two examples described above should show how the user can build complex and detailed reason trees that can reflect all the different machine states. To enable in-depth analysis on downtime reasons later, it is useful to reflect as many states and reasons as possible in the reason tree.

For more information on how to set up the Reason Tree, refer to Configuring Reason Tree.