What does the gray scale printing of the printer nozzle mean?

2017-07-20

Gray-scale printing means that in a nozzle hole, ink dots of different sizes can be ejected, that is, a function of merging a plurality of ink dots together to form a large ink dot, and the gray-scale printing has a transition color from dark to light. Better color effect.

What does the gray scale printing of the printer nozzle mean?

  UV printers use industrial nozzles. The gray scale printing technology of the nozzles is a very important topic when discussing single-pass printers. During the operation of a single-pass printer, the position of the print head is fixed, and the print media is constantly moving. Because the printhead is stationary, a large amount of fluid can potentially be placed to achieve higher ink throughput. Scanning the printer can be achieved by repeatedly moving the print head back and forth to achieve enhanced print quality, unlike a single-pass printer where the print media passes through the print head only once. This allows gray-scale printing in single- The pass on the printer becomes crucial.

The grayscale printing implementation technology can generate ink droplets of different sizes according to the data in a single image file to obtain image quality consistent with small dot high resolution imaging without sacrificing productivity associated with large drop printing.

The print head drive system (including hardware and software) needs to be specially designed to cooperate with the grayscale printing function of different brands of print heads.

There are three different ways to print ink droplets:

  · Two-state printing: Also called "native", 1-bit data per pixel (1bpp). Each pixel is 0 or 1 drop. All nozzles on the print head eject the same size ink droplets on each firing.

  · Adjustable binary printing: Also known as "Binary Multi Pulse." One bit of data per pixel (1bpp). The pixel value is 0 or 1. A plurality of ink droplets coalesce into a droplet of ink on the print medium in accordance with the size of the droplet desired by the user during the ejection. The adjustable binary print mode allows the user to select the right amount of ink on the single-pass printer without having to change the type of print head used.

   · Grayscale printing: Also called "Multi Bits". 2 bits of data per pixel 2bpp or 3 bits of data per pixel 3bpp. By controlling each nozzle to eject a certain number of ink droplets and coalescing into a single ink droplet, different pixels within one image will appear on the print medium with different droplet sizes. Each firing of each nozzle can generate different sizes of ink droplets as needed.

higher resolution:        lower resolution:         grayscale:


In two-state printing, each nozzle can only generate fixed-size ink droplets, and the final “pixels” printed on the media are “with ink droplets” and “without ink droplets”. In contrast, grayscale printing can produce droplets of different sizes and have more advantages in printing effects, such as clearer text, sharper edges, color matching using less ink, and for singles. The -pass printer is an extremely important point, without sacrificing high quality prints for production.

Two-state printing: The printhead requires a single, optimized trapezoidal pulse to generate the matched base drop size when the printhead is designed.

Adjustable two-state printing: The printhead uses successive trapezoidal pulses of increasing amplitude to produce ink droplets of a base ink drop size of 1.5 to 3 times. Each firing nozzle can only be switched on or off. In this case, all the pulses in the waveform will be used. Therefore, the size of the droplet cannot be selected according to different pixels within the same image. In this mode, a multiple pulse amplifier is required.


Grayscale printing: In any ignition pulse cycle, the nozzle on the printhead can be controlled to eject a small, medium, or large ink drop. Small, medium and large dots are generated based on the needs of the image. In this mode, a multi-pulse amplifier and multi-bit data encoding and decoding functions are required.

Supporting grayscale printing The design of the printhead driver board is a complex task that requires technology and experience.

The drive system must have the ability to generate a suitable high voltage waveform containing high quality trapezoidal pulses over a range of injection loads. The drive system must support several trapezoidal pulses of different amplitudes within a single waveform, and these waveforms must be Programmed so that the waveform structure can be optimized for different applications or inks. Finally, the data path circuit must timely update the state of the switch in the driver chip just before each pulse in the waveform occurs.

In order to ensure that all droplets have the correct size and jet speed, a very precise waveform shape must be generated in the drive circuit. And when generating these waveforms, the following complications must be considered:

· If an ink droplet is driven by a pulse at the beginning of a waveform, the droplet will appear earlier from the nozzle

· Small droplets travel longer in the air than large droplets (while the print media is constantly moving)

Due to different waveform pulse sizes, some droplets are faster than others

· The ink droplets may collide with other ink droplets during flight

· The distance between the nozzle surface on the print head and the surface of the print media is changing

Different types of ink need to match different waveforms

Ideally, the driver board will have a power amplifier for each nozzle row to allow each row of nozzles to apply different waveforms to compensate for the difference between each nozzle row. In contrast, cheap, simple driver boards simply switch between two potentials. For best results, each waveform pulse that generates sub-ink drops should have a different pulse shape. For example, the first ejection of an ink droplet requires more energy than the second ejection of an ink droplet because the piezoelectric element has been in an oscillating state at the time of the second ejection. This means that ideally the hardware that generates the voltage waveform should be able to support different shaped analog pulses. Instead of a fine driver board, you try to skip these complex requirements and simply generate waveform pulses by simply switching between the two levels.

By performing individual timing control on each pulse and being able to match any pulse segment to a specific droplet size waveform, more robust control can be achieved on simple multipulse operation.


Application-specific tuning is very important for accurate drop placement and high-speed drop ejection.

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