AutoCAD Plot Styles – Explanation of Plot Styles (CTB and STB Files) and Their Role in Print Output

Introduction

Plot styles in AutoCAD are essential tools for controlling how drawings appear when printed. Whether you need clear distinctions between line weights, colors, or shading, plot styles allow you to set specific parameters that enhance readability and accuracy. Plot styles are stored in Plot Style Table (CTB and STB) files, which apply predefined settings to each element in your drawing, ensuring consistent print output across different projects. This article provides an in-depth explanation of AutoCAD plot styles, comparing CTB and STB files and explaining how they impact the final print output.

What is a Plot Style in AutoCAD?

A plot style in AutoCAD is a collection of settings that determine how different objects in your drawing will appear when printed or plotted. These settings control properties like line weight, color, screening, and transparency, allowing you to customize the look of your drawings for various presentation purposes.

Plot styles are especially useful in complex drawings where visual clarity is crucial, helping you emphasize certain elements, maintain uniformity across prints, and ensure adherence to industry standards.

CTB vs. STB Plot Style Tables

In AutoCAD, plot styles are managed using Plot Style Tables, which come in two types: CTB (Color-Dependent) and STB (Style-Dependent). Each type applies plot settings differently, offering unique advantages depending on your project’s requirements.

CTB Files (Color-Dependent Plot Style Table)

A CTB file assigns plot styles based on the color of objects in the drawing. Each color has specific settings for line weight, screening, and other plot properties. For instance, if red lines need to be thicker in a plot, you would assign a heavier line weight to the color red in the CTB file.

Key Features of CTB Files:

• Color-Based Settings: Every color in the drawing has an associated plot style. For example, color 1 (red) may be assigned a thick line weight, while color 2 (yellow) has a thin line weight.
• Ideal for Color-Coded Drawings: CTB files are suitable for projects that rely on color-coding, where line weight and style need to correspond directly to object color.
• Common in Architectural and Mechanical Drawings: CTB files are widely used in architectural, mechanical, and engineering drawings where color distinctions are essential for conveying information.

Example: In a floor plan, red may represent structural walls, blue may represent electrical components, and green may represent plumbing. With a CTB file, you can assign different line weights and screening values to each color, helping each component stand out in the final print.

STB Files (Style-Dependent Plot Style Table)

An STB file assigns plot styles based on named plot styles rather than colors. Each object in the drawing can be assigned a unique plot style, allowing for greater flexibility regardless of the object’s color.

Key Features of STB Files:

• Style-Based Settings: Instead of basing plot properties on color, STB files use named plot styles, such as “Thick Lines” or “Dashed Lines.” These styles can then be applied to objects regardless of their color.
• Greater Flexibility: STB files allow you to assign different line weights, colors, and styles without affecting the actual color of the objects in the drawing.
• Ideal for Monochrome or Multi-Layered Drawings: STB files are effective for projects that require complex layering or when color doesn’t play a functional role in distinguishing elements.

Example: In a wiring diagram, you might have multiple objects colored according to electrical standards. With an STB file, you could assign different plot styles (such as “Solid Thick” or “Dashed Thin”) to different elements without changing their color.

How to Create and Apply Plot Style Tables in AutoCAD

Creating and applying plot styles in AutoCAD involves configuring a CTB or STB file and linking it to your drawing. Here’s a step-by-step guide on how to set up plot styles for your project.

Step 1: Access the Plot Style Manager

1. Open the Plot Style Manager: Type STYLESMANAGER in the Command Line and press Enter. This opens the Plot Style Manager, where you can view, edit, and create CTB or STB files.
2. Choose a Plot Style Type: Decide whether your drawing will use a CTB or an STB file. This choice is generally made at the start of a project, as switching plot style types later can be complex.

Step 2: Create or Edit a Plot Style Table

1. Create a New Plot Style Table: In the Plot Style Manager, click Add A Plot Style Table Wizard to create a new CTB or STB file. Choose either a color-dependent or style-dependent plot style table depending on your project needs.
2. Edit Plot Properties:
   • CTB File: For each color, specify properties like line weight, screening, and end style (how line ends are drawn).
   • STB File: For each named plot style, define settings for line weight, color, and screening. Named styles can include options like “Thick,” “Dashed,” or “Light,” and are applied based on design standards.
3. Save and Apply: Once the properties are configured, save the plot style table in the Plot Styles folder. Your new CTB or STB file is now ready to be applied to your drawing.

Step 3: Assign the Plot Style Table to Your Drawing

After creating or editing a plot style table, you need to assign it to your drawing to ensure the correct settings are applied when plotting.

1. Open the Plot Dialog Box: Type PLOT in the Command Line or access it from the Quick Access Toolbar.
2. Select Plot Style Table: In the Plot Style Table (Pen Assignments) section, choose the CTB or STB file you want to apply from the dropdown menu.
3. Preview the Plot: Click Preview to see how the plot styles will affect your drawing. Check for line weights, colors, and other properties to ensure the output matches your requirements.
4. Save Plot Settings: Once satisfied with the settings, save them in a Page Setup to quickly apply the same plot style across different layouts or drawings.

Understanding Plot Style Properties

Each plot style file contains multiple properties that control how objects appear in the printed output. Here’s an overview of the most common properties:

• Color: Defines the color of an object in the plot. Colors can be changed for monochrome or grayscale output.
• Line Weight: Controls the thickness of lines in the plot. Heavier line weights are often used for structural elements, while lighter line weights represent less critical details.
• Screening: Reduces the color intensity of an object, allowing for lighter shades. Screening is useful for backgrounds or non-essential elements.
• Dithering: Adds a stippled effect to colors for smoother transitions. Dithering is used sparingly as it can affect print clarity.
• Transparency: Sets the transparency of objects in the plot. Transparent objects can be useful for overlays but may reduce clarity when printed.

Best Practices for Using Plot Styles in AutoCAD

1. Choose the Appropriate Plot Style Type: Decide early whether to use CTB or STB files based on your project needs. Color-based CTB files are useful for quick color coding, while STB files offer more flexibility for complex layering.
2. Test Plot Styles Before Printing: Preview the plot in the Plot dialog to ensure the line weights, colors, and transparency look as expected. Make adjustments as needed to avoid costly reprints.
3. Standardize Plot Styles for Team Projects: Use a shared plot style table for projects with multiple collaborators to ensure consistency in printed output across the team.
4. Save Common Plot Configurations: For frequently used settings, save plot configurations in Page Setups. This allows you to apply the same plot styles to multiple layouts without manually adjusting each time.
5. Use Descriptive Named Styles in STB Files: When creating named styles, use descriptive names like “Thick_Dash” or “Gray_Background” to help team members understand and apply them correctly.

CTB vs. STB: Which One Should You Use?

The choice between CTB and STB files depends on your project requirements and personal preferences:

• CTB Files are ideal for projects that rely heavily on color distinctions. If you need to quickly set up different line weights or styles based on color, CTB files can be more straightforward.
• STB Files provide more flexibility and control, as plot styles are not color-dependent. This makes STB files suitable for projects that require layering or where line weights and styles are applied irrespective of color.

In many organizations, CTB files remain the preferred choice for color-coded designs, while others adopt STB files for their versatility, particularly in projects where multiple plot styles are needed for the same color.

Conclusion

Understanding plot styles in AutoCAD, particularly CTB and STB files, is essential for creating precise, consistent, and professional print output. Plot styles offer complete control over how each element in a drawing is represented in the final print, ensuring that design intent is clearly communicated. By learning to set up, edit, and apply plot style tables, you can streamline the plotting process, improve print clarity, and maintain uniformity across your projects. Whether you’re working on architectural plans, mechanical schematics, or electrical layouts, AutoCAD’s plot styles provide the flexibility and customization needed to meet diverse project requirements.

FAQs

1. What is a CTB file in AutoCAD?
   A CTB file is a color-dependent plot style table that applies specific line weights, colors, and styles based on the color of objects in a drawing.
2. How do I choose between CTB and STB files?
   Use CTB files for color-coded drawings where plot settings depend on object color. STB files are better for projects requiring named styles that offer more flexibility.
3. How can I apply a plot style table to my drawing?
   Open the Plot dialog, select the desired CTB or STB file under Plot Style Table (Pen Assignments), and apply it to the drawing layout.
4. Can I change the plot style table type in an existing drawing?
   Yes, but it involves converting between CTB and STB types, which can be complex. It’s best to decide on the plot style type at the start of a project.
5. What properties can I control with plot styles?
   Plot styles control properties like color, line weight, screening, transparency, and line end/corner styles in the final printed output.