by Dennis Collin
Whilst Autodesk do have products for the modelling of duct and pipe elements like CADMEP and Revit MEP, there are still projects worked using the classic AutoCAD/LT platform which only require 2D drawings.
Fig 1. Centre mark and line functions have been available as a dedicated function since 2017!.
For round ductwork and pipes there is a need to show a centreline which helps identify the nature of the linework in any sitepipe or plant room drawing. This linework will often be a different colour and lineweight from the outer lines.
Since 2017 both LT and Full AutoCAD have had the Centermark and Centerline functions under the annotate tab. These elements can be useful when documenting building service drawings.
By default, all new objects are created on the current layer. However, it is possible to specify a default layer with the CENTERLAYER system variable.
If using these elements, it is worth considering these element limitations Centermarks and lines work best with Drawings that will be printed or published from model space. Or for drawings that are annotated on the Paper Space sheet. The objects do not currently support annotative scaling.
That is not to say you cannot use them in the layout annotative context, but specific variables may need to be set to suit a particular workflow.
The elements possess their own system variables
- CENTERLTYPE – can be used to specify a different linetype
- CENTERLTSCALE – sets a linetype scale used by centermark and line objects.
- CENTERCROSSSIZE – "ByLineType" (DEFAULT)
Uses the default size is derived from the linetype assigned to the marker
- CENTERCROSSGAP - “ByLineType" (DEFAULT)
Uses the gap between the center mark and its centerlines is derived from linetype assigned to it.
By default, the linetype used for center marks and centerlines is CENTER2 but if a different appearance is required, load in an alternate linetype and adjust the following variables to suit. Or users can also use the CENTERLTYPEFILE system variable to reference another linetype library specifically for center mark elements.
I have written a previous post on creating custom line patterns here:
There are also some tools for AutoCAD that make the creation of custom linetypes easier, I will discuss this process in a future post.