When encountering heavy paint lines on the outer edges of the spray pattern while using an airless sprayer, it is important to address this issue promptly to achieve a smooth and even finish. This problem may be attributed to several factors:

1. Tip Size: Using a tip that is too small can lead to higher pressure at the edges of the spray pattern, causing heavy paint build-up. Adjusting to a larger tip size can help distribute the paint more evenly. Choose an airless spray tip.

2. Pressure Setting: Incorrect pressure settings can also result in uneven paint distribution. Lowering the pressure can help reduce the heavy paint lines on the edges of the spray pattern.

3. Distance from Surface: Maintaining a consistent distance between the sprayer and the surface is crucial. Deviating from the recommended distance can lead to uneven paint application. Ensure that you are holding the sprayer at the optimal distance for a uniform finish. Typically 12 inches.

4. Sprayer Technique: Proper technique plays a significant role in achieving an even spray pattern. Move the sprayer in a smooth, continuous motion across the surface, overlapping each pass slightly to prevent heavy lines from forming.

5. Paint Viscosity: The viscosity of the paint can affect how it atomizes and spreads through the sprayer. Thinning the paint to the appropriate consistency specified by the manufacturer can help prevent heavy lines in the spray pattern.