In robotic spray painting, understanding the spray pattern is essential for achieving stable quality and predictable results. One of the key standardized metrics used to describe the spray pattern is the SB50 metric.

What does SB50 metric mean?

SB50 is a standardized metric used in spray painting to describe the spray pattern width at 50% of the maximum paint density or film thickness.

The abbreviation SB originates from German practice, but several interpretations are used across different sources.

Origin of the SB50 Term

The following terms are commonly used to describe SB50:

• Spritzbild 50 – literally “spray pattern 50”
  Commonly used informally in German paint shops.
• Sprühbreite 50 – “spray width at 50%”
  Appears in patents and process documentation.
• Sprühstrahlnennbreite SB50 – “nominal spray jet width at 50%”
  Used in official German research reports, for example in DBU publications.

How Is the SB50 Calculated?

The spray pattern is applied to a foil or metal sheet.

The point of maximum paint thickness is identified, usually at the center of the pattern.

From the center outward, the points at which the thickness drops to 50% of the maximum value are identified.

The distance between these two points represents the SB50 value.

What Is SB50 Metric Used For?

SB50 is used to:

• evaluate spray pattern consistency and repeatability,
• help optimize applicator settings,
• enable comparison of application equipment,
• serve as a core metric for coverage and film thickness simulation.

Practical Examples of Use

An SB50 of 280 mm means that the spray pattern is 28 cm wide at 50% thickness.

A change to 260 mm or 300 mm indicates a process deviation, such as:

• wear,
• incorrect settings,
• or process instability.

SB50 helps verify whether the spray width matches the trajectory overlap.

Misalignment between SB50 and the trajectory can cause coating defects and production instability.

Example 1

SB50 Pattern Does Not Match the Trajectory

Example 2

SB50 Matches the Trajectory and Overlapping