Pen Settings

Most CAD software plots either using a colour based plotting system where a color represents a specific pen weight or alternatively a plot style base where colour and lineweight are independent.. By understanding the two systems it is possible to produce data that will replicate perfectly in both systems.

Colour based Plotting (AutoCAD CTB)

Color dependent plot styles or CTBs for AutoCAD users are the original method of mapping how a Cad entity plots, based upon its Color. Within AutoCAD the Ctb files store the mapping of the default 256 AutoCAD Colors to the plot Color as well as the lineweights, line end style, line join style etc.

The majority of users still plot using Ctb based plotting as this is the traditional method of plotting and most AutoCAD standards are therefore built around this

General CAD practice was originally to use the first 8 colors as Black and then use the other colr assignments for Color plotting. With the introduction of True Color and the Color books the use of all 256 colors for black has been adopted in various standards and is the basis for the BIMuk Colour based plot Style. The first 9 colours are based upon the ISO draughting Pen colours and the other 247 colours used a matrix to determine the pen thickness.

BIMuk have produced the following AutoCAD CTB files that may be used with this standard. These are based upon the pen colour mappings shown on the Pen Weights Section.

BIMuk Standard.CTB

Downloadable via above link for AutoCAD 2007 +

Colours 1 to 9 as per ISO Pen weights. Colours 10 to 255 as per Tri Services standard. All pens print black.

For Colour printing use True Colour or Colour book options.

Screening for Pens 1 to 249 is at 100% and Pens 250 to 255 is set to 50%.

BIMuk Light.CTB

As per above but penweights are halved. (i.e. Cyan 0.5mm will be set to 0.25mm). Primarily for use with A1 to A3 reduction.

Named Plot style Tables (AutoCAD STB)

Stbs contain Named Plot Styles which can be defined be the User. Named Plot styles make no reference to the AutoCAD color. Instead a name is defined such as “Fine” and then different plot settings such as Lineweights, Linetypes, fill patterns etc are applied to it. As many or as few plot styles can be defined as required within the Plot Style Table. The original thinking behind plot styles was to have a plot style defined for each pen such as fine, medium, thick etc…. With the introduction of the Line weight property for AutoCAD Layers and Entities the need to define this at the Plot style level has been negated.

The new AEC Standard.STB simplifies Plot Styles to the minimum with only five Basic plot styles. As all Lineweight, Line End Style, Fill style etc are set by object within AutoCAD the only properties to be changed by the Plot style are the plotting color and the screening. The five plot settings are:

Normal: Where the color (including true color) is defined by the AutoCAD Layer or Entity

Invisible Ink – This uses Cyan for creating Blue Print

Full Saturation – Where the plot color is defined as black and screening is 100%

50 Percent - Where the plot color is defined as black and screening is 50%

25 Percent - Where the plot color is defined as black and screening is 25%