Inkjet Printing Waveform Optimization and Waveform Tools Introduction

Inkjet Printing Waveform Optimization and Waveform Tools Introduction

Table of content.

Waveform Adjustment in Inkjet Printing

During the use of inkjet printers, it is very common to encounter situations where waveform adjustment is required—for example, after changing ink, replacing the printhead, replacing the printhead driver board or mainboard, changes in printhead condition after long-term use, or verification of ink formulation and process parameters.

The following content covers waveform tools, waveform file types, factors affecting waveforms, and the steps and methods for waveform adjustment. Combined with practical application experience and best practices shared by industry peers, this guide aims to provide more useful support for your daily operation and product development work.

 

 

Waveform Tools

Waveform tools are software used to develop and create drive waveforms. By adjusting voltage levels and pulse widths, these tools influence droplet formation and landing position, thereby directly affecting overall print quality.

Common Waveform Tools

1. Xaar (printhead supplier) – waveform tool software and debugging interface

2. BluePrint / LanYin (controller board supplier) – waveform tool and debugging interface

3. TTP (controller board supplier) – waveform tool and debugging interface

If you want to know more about Metwave, Konica, and Minolta waveform debugging tools, please click the link

 

Waveform Files

A waveform is the drive signal and command applied to the piezoelectric actuator inside the printhead.
 A waveform file is a set of “data” that drives the printhead, including parameters such as printhead model, voltage, pulse width, and delay, grayscale levels, and more.

Waveform File Representations

For example, waveform contentis displayed in the TTP MetWave controller software.

TTP board tool: Konica Minolta 1024A nozzle waveform content👆

TTP board tool: Ricoh G4 nozzle waveform content👆

TTP board tool: Epson I3200 nozzle waveform content👆

TTP board tool: Xaar 2001 nozzle waveform content👆

Blueprinting board tool: Ricoh G5 printhead waveform editing content👆

Xaar Waveform Tool: Xaar Nozzle Waveform Editing Content👆

From the above waveform tools and waveform file examples, we can summarize the following common points:

  1. Waveform tools are provided by controller manufacturers or printhead manufacturers, and most require authorization to use.

    • For example, Xaar tools require paid licensing

    • TTP and BluePrint tools are generally provided with their controller boards

  2. Waveform tools and waveform data typically include parameters such as:

    • Voltage (V), VH1, VH2

    • T0 (µs), T1 (µs), T2 (µs)

    • Temperature

    • Small drop / Large drop

      Observe and adjust the ink droplet effect using an electronic magnifying glass at 200x magnification👆

  3. This indicates that waveform tuning essentially means adjusting voltage and pulse timing delays under a certain temperature condition to optimize droplet uniformity, consistency, and alignment.

  4. If no dedicated waveform tuning tool is available, waveform optimization can be done temporarily by:

    • Adjusting printhead voltage

    • Ink temperature

    • Printing speed

    • Printing nozzle status test patterns

    • Observing droplet behavior with an electronic microscope

  5. Adjust parameters step by step until suitable voltage, temperature, and speed values are found.


     Note: Some printheads (e.g., Kyocera) do not allow free waveform modification, as the waveform is written directly into the printhead.


PS: Once you understand the key factors affecting waveforms, the rest comes down to hands-on testing and experience accumulation.

 

 

Waveform Fundamentals

To better explain the purpose of waveforms, let’s examine the internal structure of a printhead nozzle chamber.

The figure below illustrates the commonly used fill-and-fire jetting process, applied in many printhead designs. In this process, a stack of piezoelectric ceramics deforms when voltage is applied, changing the ink chamber volume and causing ink movement and ejection. The method of applying this voltage is the waveform.

In this example, the piezoelectric actuator elongates only when voltage is applied. When powered, the actuator remains elongated at a certain voltage, keeping the chamber in a non-ejecting state (left). When the voltage is reduced, the actuator retracts, expanding the chamber and drawing ink inward (center). When the voltage returns to its original value, the chamber contracts and excess ink is expelled through the nozzle (right). This process repeats thousands of times per second.

Printheads may be driven by positive or negative pulses, depending on their design. Regardless of convention, the most critical waveform features are the two sloped transitions and the dwell (hold) time, during which the voltage remains at a level before returning to baseline. This timing determines nozzle behavior and is the first key step in waveform design.

 

 

Pulse Timing Basics

If you stand next to a printhead during printing, you may hear a sound that varies with frequency. This sound is caused by acoustic waves generated by the actuator. The most important waves are those generated in the ink itself, as they define the pressure changes responsible for droplet ejection.

Due to the mechanical properties of ink and energy loss during wave reflection, the pressure in the chamber behaves like a damped resonator. Any deformation of the piezoelectric element creates characteristic pressure oscillations. When the chamber expands, ink begins to oscillate back and forth.

This energy alone is often insufficient to eject ink—it merely causes oscillation. By applying voltage pulses at the correct timing, pressure is reinforced, making droplet ejection much more efficient. When pressure exceeds a critical threshold at the optimal moment, a droplet is ejected.

 

Why Pulse Width Is Critical

If the pulse width is too short or too long, the pressure waves and actuator motion fall out of sync. Instead of reinforcing momentum, the forces cancel each other out.

This is similar to pushing a child on a swing: push at the right time and momentum increases; push at the wrong time, and the swing stops abruptly. Likewise, incorrect pulse width results in inefficient and unstable jetting.

Although nozzle chamber length is fixed, pulse timing also depends on the speed of sound in the ink, which varies by ink formulation. This is why waveforms must be tuned for each specific ink–printhead combination—a single universal waveform is not sufficient.

 

 

What Is Resonance?

A waveform that works well at one frequency may perform poorly at another. As firing frequency increases, pressure waves from successive pulses can interact.

At certain frequencies, these interactions reinforce each other, producing resonance. At higher frequencies, pressure may not fully decay before the next pulse, increasing the risk of unstable jetting, excessive ligaments, satellites, or nozzle wetting.

If printing speed is flexible, it is wise to study droplet formation across a frequency range to avoid resonance zones.

 

Multiple Pulses

If electronics allow, multiple pulses can be applied per pixel to generate larger or faster droplets. Multi-pulse waveforms typically rely on the first or second resonance cycle.

The first pulse increases ink pressure; some ink ejects, while the remainder rebounds. When the ink moves toward the nozzle again, a second pulse reinforces momentum. Pulse timing must be carefully tuned—overdriving can cause nozzle wetting and satellites.

If pulse amplitudes are identical, the second droplet will be larger and faster due to resonance. Drops may merge on the substrate or in flight, depending on head design, timing, voltage, and ink properties.

Real-time droplet visualization (e.g., with a drop watcher) greatly aids waveform optimization.

Additional pulses may also be used as pre-pulses (to agitate ink without jetting) or post-pulses (to dampen meniscus oscillation and enable higher frequencies). Some advanced waveforms incorporate these techniques and are derived from Ricoh desktop printer patents.

 

How to Optimize a Waveform

The first step in waveform optimization is to establish a reasonable baseline for our jetting so we can view it with a dropwatch. If possible, a simple approach is to start with the single-pulse waveform recommended or defaulted to by the printhead manufacturer. In addition to the typical pulse timing, there is usually some kind of calibration voltage (sometimes called a "tag" voltage). Use this as a starting point because it should produce reasonable jetting. For our Dimatix Samba example, we'll start with the waveform from the printhead user manual: pulse width 2.18µs, amplitude pulse 26V (including a 40V/µs rise time). The next step is to make the ink droplets visible in the field of view of the ink watcher. If possible, it's important that you can see the printhead panel; this is also very helpful in finding the cause of failure if you're not performing well. The image below shows an ideal view of the Dimatix Samba printhead.

If you're only doing initial testing with a syringe filler, then ink consumption should be minimized during testing. Select about 10-20 nozzles in the same row of the printhead and jet at a medium frequency of 8kHz; this can be tested for a period of time without needing to replenish the liquid. Quickly measure the descent speed to ensure it's reasonable, perhaps 5-6 m/s. Even with higher targets, this setting can usually be easily measured without too many satellites. If the speed is found to be too slow, the pulse voltage needs to be increased slightly, and vice versa. If the speed is acceptable, no waveform modification is needed, so 26V is a suitable setting.

 

Step 1: Optimize Pulse Width

Start with a manufacturer-recommended or default single-pulse waveform. Ensure droplets are visible in the drop watcher field of view. Measure droplet velocity (e.g., 5–6 m/s). Adjust the voltage slightly if needed.

Scan pulse width from −50% to +50% of the recommended value and measure droplet speed and volume at each point. The optimal pulse width typically corresponds to maximum velocity.

For example, a Dimatix Samba head showed optimal performance at ~2.1–2.2 µs, matching the manufacturer’s recommendation.

 

Step 2: Optimize Voltage

With timing fixed, vary the voltage (e.g., in 0.5 V increments) and measure droplet speed and satellite formation. Choose the highest voltage that achieves target speed and volume without satellites.

 

Step 3: Increase Printing Frequency

Test waveform performance across the operating frequency range, including sub-harmonics (½ and ⅓ frequency). Avoid resonance zones identified by sudden velocity increases and satellite formation.

 

Step 4: Introduce Multiple Pulses

If a single pulse cannot generate sufficient volume, use multiple pulses. Optimize inter-pulse spacing to align with ink resonance. The optimal spacing produces the highest second-drop velocity.

 

Creating Multi-Pulse Grayscale Waveforms

Grayscale printing varies the droplet size per pixel. This requires dividing waveforms into selectable segments and assigning pulse combinations to each gray level.

The maximum printable frequency is determined by the total waveform duration, regardless of gray level.

 

Advanced Waveform Design. Advanced techniques include:



  • Pre-pulses: Improve jetting efficiency by pre-conditioning ink motion

  • Damping (cancel) pulses: Reduce residual oscillation and nozzle wetting

  • Slew rate control: Limits voltage transition speed for safe operation

  • Bipolar waveforms: Use both positive and negative voltages for greater efficiency

Modern waveforms are often defined as multi-segment voltage transitions over time, rather than simple trapezoidal pulses.

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