UV Flatbed Printer: Causes and Solutions for bigger White Ink printed Grainy

UV Flatbed Printer: Causes and Solutions for bigger White Ink printed Grainy
White ink, which contains a high amount of titanium dioxide (TiO2) to achieve high coverage, is inherently more prone to settling, impurities, and graininess compared to colored inks. When the print result shows obvious graininess, it can typically be investigated and resolved from the following two aspects:

I. White UV Ink Quality Issues
Root Causes
Titanium Dioxide Characteristics: Titanium dioxide has a high specific gravity and settles easily. Poor-quality inks have poor dispersion, leading to severe pigment particle agglomeration or sedimentation.
High Impurity Content: Inferior inks may contain more impurities introduced during production or include large particles that haven’t been sufficiently ground.
Poor Stability: Poor ink formulation can lead to easy stratification, clumping, or chemical reactions causing sediment.

Consequences
High Risk of Nozzle Clogging: Large particles and sediment easily clog nozzles, accelerate printhead wear, and significantly shorten its lifespan.
Poor Print Quality: Uneven ink droplet ejection leads to noticeable graininess, roughness, uneven color, or even missing jets and banding on the printed surface.
Increased Maintenance Costs: More frequent printhead cleaning and filter replacement are required, leading to increased downtime.

Long-term Solution
Upgrade Ink Quality: Adopt high-quality white ink.
Better dispersion stability (reduces settling).
Finer pigment grind (smaller particles).
Stricter impurity control.
Good compatibility with the printer’s printheads.
Temporary Preventive Measures
Use High-Quality Filters (typically rated at 5-10 microns).
Shorten Replacement Cycles: Inferior inks clog filters faster. Be sure to replace filters (main tank, secondary tank, and those before the printhead) more frequently than when using high-quality inks or colored inks. Follow the ink manufacturer’s recommendations and adjust flexibly based on actual usage (such as print volume, downtime).

Strengthen Daily Maintenance:
Perform regular printhead cleaning and moisturizing procedures.
Before extended downtime, thoroughly clean the white ink circulation system and Moisturizd the printheads.

II. Mismatched Print Profile (Waveform/Dot Settings)

Root Causes
Ink Droplets Too Large: Using a print profile designed for high coverage or high speed, such as a “Large Dot” or “Bold Dot” setting. These profiles eject larger droplets. While they offer strong coverage and speed, the individual dots formed after these larger droplets land and spread on the medium are also larger, resulting in more visible graininess.
Profile Mismatched to Ink/Medium: The profile is not optimized for the specific brand/batch of white ink being used or the type of printing medium.

Solutions
Switch to a Finer Print Profile:
Prefer “Small Dot” or “Medium Dot” Profiles: These profiles control the printhead to eject smaller droplets. Smaller dots formed on the medium are finer, which can significantly reduce graininess and improve surface smoothness.

Sacrifice Speed for Quality: Using small dot profiles usually reduces printing speed, but this is a necessary trade-off for achieving a fine, smooth white ink layer.

Conduct Profile Testing and Optimization:
Before formal printing, print test patterns on the target medium using different “Small Dot” and “Medium Dot” profiles.
Observe coverage, surface smoothness (graininess), adhesion, curing level, etc., and select the profile with the best overall result.
If the printer manufacturer or ink supplier provides white ink profiles optimized for specific media, try these first.
Consider Pass Count: While ensuring adequate coverage, appropriately increasing the print pass count (number of printhead passes) can sometimes help distribute the dots more evenly, making the surface more uniform (but speed must be considered).

III. Application of Ink Cartridge Agitation Function

Critical Importance: For white ink, agitation is an essential function to effectively mitigate settling issues.
Operation Method:
With Automatic Agitation: Before starting each print job (especially after long periods of inactivity), always activate the automatic agitation function of the white ink circulation system first. Run it for 5-10 minutes to ensure settled titanium dioxide is fully and evenly mixed。

Without Automatic Agitation:
Manual Shaking: Before adding ink or after extended downtime, manually shake the ink bottle (or bag) vigorously for at least 2-3 minutes, ensuring no sediment remains at the bottom. For white ink inside the machine, if the structure allows and it is safe, attempt manual agitation (exercise extreme caution).

Install an Agitator: It is highly recommended to subsequently install an automatic agitation device (such as a circulation pump or built-in stirrer) for the white ink system. This is a long-term solution to prevent white ink settling, ensuring stable printing and printhead lifespan. Continuous, gentle agitation maintains ink uniformity.