Inkjet R&D Solution Design — Printhead Arrangement Combinations and Optimization (Worth Saving)

Inkjet R&D Solution Design — Printhead Arrangement Combinations and Optimization (Worth Saving)

Table of content.

Inkjet R&D Design — Printhead Arrangement Methods

Preface

In previous articles, we introduced inkjet R&D topics related to encoder (grating) resolution and print resolution calculations. See:
 Inkjet R&D Design: Encoder Resolution and Print Resolution (Worth Saving).

This article focuses on scan-type inkjet printer printhead arrangement and combination methods. For different inkjet printers and application industries, a proper printhead arrangement can maximize printing efficiency while reducing unnecessary printhead waste.

 

 

Common Printhead Arrangement Methods

Two common arrangement methods are shown below: Method A and Method B.

 

Printhead Layout Method A

Using the Ricoh MH5340 as an example, with CMYK four-color inks, one color per channel, we analyze printhead arrangement and 1-pass data conversion.

Printhead Interleaving

Interleaving refers to how 1-pass image data is converted into physical channel data for each printhead.

Printhead Grouping

In the figure, printheads No. 1 and No. 3 are arranged along the Y direction, which is the scanning or carriage movement direction.
 (Printheads 1 and 3 form one group.)
 This grouping determines the 1-pass scanning resolution in the Y direction.

Option ① Interleaving in the X Direction

Treat printheads 1 and 3 as a single unit, where the nozzle positions of one printhead are offset by 1/2 nozzle pitch in the X direction.

In the Ricoh MH5340 single-head four-color mode:

  • Each printhead has four nozzle rows

  • Four ink channels (one color per channel)

  • Each color has a resolution of 150 dpi

  • Printhead No. 1 data: 150 dpi / 1 color (1-pass print width: 54.1 mm)

  • Printhead No. 3 data: 150 dpi / 1 color (1-pass print width: 54.1 mm)

Since the two printheads share identical color channels, the channels are interleaved in the X direction and merged into one channel, achieving a resolution of 300 dpi, as shown below.

If the encoder resolution is 150 dpi, the 1-pass print resolution becomes:
 300 dpi × 150 dpi

Option ② Channel Merging in the Y Direction

Treat printheads 1 and 3 as a single unit, and stack their channels side by side in the Y direction as one channel.
 In this case, the CMYK data from printheads 1 and 3 fully overlaps, doubling the Y-direction resolution to 300 dpi.

If the encoder resolution is 150 dpi, the 1-pass print resolution becomes:
 150 dpi × 300 dpi

 

 

Printhead Stitching

In the X direction, printheads No. 2 and No. 4 are stitched to printheads No. 1 and No. 3 respectively.
 (Printheads 2 and 4 form one group.)

The stitching width determines the scan print width per pass.

Taking the Ricoh MH5340 as an example:

  • Single printhead print width: 54.1 mm

  • Stitching printheads 1 and 2 results in a 1-pass print width of 108.2 mm (without feathering)

Stitching rule:

  • The last nozzle of the preceding printhead aligns with the first nozzle of the next printhead

  • This rule applies sequentially for multiple printheads

  • The same applies to printheads 3 and 4

 

Influence of Stitching Direction

The stitching direction mainly affects the image width printed in a single pass.

Examples:

  • Image size: 1000 mm (length) × 108.2 mm (width)
     Resolution: 300 dpi × 300 dpi
     Using Layout A (Options ① or ②):
     Only 2 passes are required:
     (300 × 300) / (300 × 150) = 2

  • Image size: 1000 mm × 216.4 mm
     Resolution: 300 dpi × 300 dpi
     Using Layout A:
     Requires 4 passes
     (2 passes in Y-direction scanning, then step in X-direction and scan another 2 passes)

 

 

Printhead Layout Method B

Printhead Grouping

In this layout, printheads No. 1 and No. 3 are aligned along the Y direction, which is also the carriage movement direction.
 (Printheads 1 and 3 form one group.)
 This configuration determines the 1-pass scanning resolution in the X direction.

Option ① Interleaving in the Y Direction

Treat printheads 1 and 3 as a single unit, where one printhead’s nozzle positions are offset by 1/2 nozzle pitch in the Y direction.

For the Ricoh MH5340 single-head four-color mode:

  • Four nozzle rows

  • Four ink channels (one color per channel)

  • Each color resolution: 150 dpi

By interleaving the channels in the Y direction, the combined channel reaches a resolution of 300 dpi.

If the encoder resolution is 150 dpi, the 1-pass print resolution becomes:
 150 dpi × 300 dpi

Option ② Channel Merging in the X Direction

Treat printheads 1 and 3 as a single unit, and place their channels side by side in the X direction.
 In this case, the CMYK data from both printheads fully overlaps, doubling the X-direction resolution to 300 dpi.

If the encoder resolution is 150 dpi, the 1-pass print resolution becomes:
 300 dpi × 150 dpi

 

 

Printhead Stitching

In the Y direction, printheads No. 2 and No. 4 are stitched to printheads No. 1 and No. 3 respectively.
 (Printheads 2 and 4 form one group.)

The stitching logic and width calculation are the same as in Layout Method A:

  • Single printhead width: 54.1 mm

  • Two printheads stitched: 108.2 mm per pass (without feathering)

  • Alignment is performed from the last nozzle of the previous head to the first nozzle of the next head

 

Printing Examples

  • Image size: 1000 mm × 108.2 mm
     Resolution: 300 dpi × 300 dpi
     Using Layout B (Options ① or ②):
     Only 2 passes are required

  • Image size: 1000 mm × 216.4 mm
     Resolution: 300 dpi × 300 dpi
     Using Layout B:
     Requires 4 passes
     (2 passes scanning in the X direction, then step in the Y direction and scan another 2 passes)

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