There are some significant differences between how you manage layers in AutoCAD and AutoCAD Mechanical toolset.
AutoCAD commands always create objects on the current layer. As such you must set the layer corresponding to the object type as the current layer before you create the object. It also means that you must create the layers and specify settings such as color, lineweight and linetype beforehand.
AutoCAD Mechanical toolset commands, using a feature that is known as Automatic Property Management, are pre-configured to create objects on specific layers. Regardless of what layer is set current, these commands create geometry/objects only on the predefined layer. If the layer doesn't exist, the command automatically creates the layer. Settings such as layer color, lineweight and linetype are taken from a set of pre-configured settings that are referred to as layer definitions.
The layers that AutoCAD Mechanical toolset creates on the fly are called mechanical layers. The AMLAYER command enables you to see a list of mechanical layers as well as layer definitions. Similar to how the LAYER command enables you to change the properties of a layer, the AMLAYER command enables you to change the properties of mechanical layers and layer definitions. Additionally, the AMLAYER command shows you what objects are created on each layer.
AutoCAD Mechanical toolset ships with 31 layer definitions, which have been assigned to different objects by default. The names of these layers begin with “AM_”, followed by a number or a phrase as described below.
AutoCAD Mechanical toolset allows you to customize the properties of each object type so that AutoCAD Mechanical toolset commands can create them on a layer of your choice instead of the ones they are created on by default. For information on how to customize AutoCAD Mechanical toolset object properties, please refer to the topic Configure Automatic Property Management in the Configuration and Setup Guide.