Optical Print Alignment Dots (OPAD) are essential tools in the printing process, designed to enhance the accuracy of registration points for various printing and finishing equipment. This article explores the functionality, application, and customization options for OPAD, ensuring that users can effectively implement them in their workflows.
Understanding Optical Print Alignment Dots
Optical Print Alignment Dots (OPAD) are small circular marks strategically placed around artwork. Their primary purpose is to assist printers, finishing equipment, and vision-based cutting systems in accurately detecting registration points. OPAD are commonly utilized in:
Laser cutting
Zund machines
Automatic trimming
Camera-guided finishing
Alignment verification during duplex printing
This feature allows users to add, style, position, and repeat these dots across selected pages.
Key Features of OPAD
Execution Control
The execution toggle allows users to turn the OPAD feature ON or OFF:
ON → Dots will be added to the output PDF.
OFF → The step is ignored, which is useful for testing different workflows.
Page Selection
Users can apply optical dots to:
All pages
A specific page range
For custom selections, users can manually choose pages where dots should appear. Use cases include:
Adding dots only on the first page
Adding dots only on the print sheet, excluding final trim pages
Dot Radius
The radius specifies the size of the dot in millimeters. Typical sizes include:
2–4 mm for camera detection
5–8 mm for manual alignment marks
Fill Color
Users can specify the color of the filled circle. The fields include:
Field | Purpose |
Color | Visual display color (e.g., black, cyan, magenta). |
Code | Spot color name or CMYK name (optional). |
Fill Spot Color Name | Declare a spot color if the dot must be printed as a separate plate. |
Use spot colors when your cutting or finishing equipment expects a specific named color (e.g., "CutContour").
Stroke Options
Users can add an outline around the dot with the following fields:
Stroke color + spot color name
Thickness
Overprint Stroke toggle
Using a stroke is beneficial when equipment reads edges rather than filled shapes.
Overprint Settings
Overprint settings include:
Overprint Fill
Prevents the fill from knocking out underlying artwork.
Overprint Stroke
Ensures the stroke prints on top of all layers. It is recommended to turn ON for finishing marks to avoid unwanted white gaps.
White Background Radius
This feature draws a white circle behind the dot, which is useful when dots appear over dark or textured artwork. Typically set to:
Dot radius + 1–2 mm
This ensures the camera can detect the dot with high contrast.
Offsets
Offsets define where dots appear relative to the page boundary. For example:
Offset Top = 12.5 mm places a dot 12.5 mm below the top edge.
Offset Left = 7.5 mm places a dot 7.5 mm from the left edge.
Using four offsets allows for dot placement in all corners.
Repeat Distance
This controls the spacing between repeated dots. If set to 0, no repetition occurs (single dot). If set to a value (e.g., 100 mm), dots are placed at intervals along that direction. This feature is particularly useful for large-format or roll printing, where alignment may drift across long lengths.
Additional X Coordinates
Users can manually specify additional dot placement by clicking Add dot. This allows for:
Custom die-cut templates
Equipment-specific target placement
Support for irregular layouts
Frequently Asked Questions
What are Optical Print Alignment Dots used for?
OPAD are used to assist in the accurate detection of registration points in various printing and finishing processes.
How can I customize the size of the dots?
The size of the dots can be specified in millimeters, with typical sizes ranging from 2 mm to 8 mm depending on the application.
Can I apply dots to specific pages only?
Yes, you can choose to apply dots to all pages or select specific pages or ranges for customization.