Generate Halftone Dots in CorelDRAW for Screen Print

Generating halftone dots in CorelDRAW allows screen printers to simulate gradients, continuous tone images, and photographs on screen print films. This process involves converting continuous grayscale tones into distinct patterns of solid dots that allow varying amounts of ink to pass through the mesh. Screen printers can generate these dots natively within CorelDRAW using internal bitmap conversion tools or output them through the PostScript print engine to a software RIP or PostScript-capable printer.

Method 1: The Native 1-Bit Bitmap Conversion

This method embeds the halftone dots directly into your vector workspace without requiring an external RIP (Raster Image Processor) software.

  1. Prepare the Artwork: Ensure your vector or bitmap design is finalized and sized to the actual print dimensions. Convert the graphic to grayscale by selecting the object and navigating to Bitmaps > Convert to Bitmap. Set the color mode to Grayscale (8-bit) and the resolution to at least 300 DPI (or up to 600 DPI for finer detail).
  2. Convert to 1-Bit Halftone: Select your grayscale bitmap, then navigate to Bitmaps > Mode > Black and White (1-bit).
  3. Configure the Halftone Screen:
    • In the conversion dialog box, set the Conversion Method to Halftone.
    • Choose your Screen type (Round or Elliptical shapes are standard for screen printing).
    • Enter the Lines Per Inch (LPI). A standard rule of thumb is dividing your screen mesh count by 4.5 or 5 (for example, a 200 mesh screen typically uses roughly 40 to 45 LPI).
    • Set the Screen angle. A 22.5° or 45° angle is standard to prevent moiré patterns on single-color prints. For CMYK separations, use standard offset angles (Cyan: 15°, Magenta: 75°, Yellow: 0°, Black: 45°).
  4. Finalize the Conversion: Click OK. CorelDRAW will render the continuous tones into solid black halftone dots. You can now output this directly to your film positive printer.

Method 2: Outputting via Print Separations (PostScript)

If you are using a PostScript printer, a RIP, or outputting to a .ps / .prn file, CorelDRAW can generate the dots dynamically during the print process.

  1. Access the Print Menu: Go to File > Print and select your PostScript printer driver or a software RIP printer driver.
  2. Enable Color Separations: Click on the Color tab and check the Separations option.
  3. Adjust Halftone Settings:
    • Click on the Separations tab in the print dialog.
    • Under the plates list, highlight the color channel containing your halftone artwork.
    • Customize the Frequency (LPI), Angle, and Dot Type according to your mesh count and ink viscosity requirements.
  4. Print to Film: Send the job to print. The PostScript interpreter will automatically convert the grayscale values into halftone dots on the film.
  • Resolution: Work with 300 to 600 DPI source artwork. Low-resolution artwork will produce jagged, deformed halftone dots.
  • Dot Shape: Use Elliptical dots when possible. Elliptical dots reduce dot gain in the midtones (around 50%) because the corners do not touch simultaneously as round dots do.
  • Density: Ensure the black color value is set to 100% K (single-channel black) to achieve maximum UV opacity on your film positive.