The Cause and Solution for an Airless Paint Sprayer that Is Not Spraying Consistently

Airless Paint Sprayers depend on consistent pressure to be able to supply and atomize material.  Sometimes I will be visiting a customer and their painter will have an issue where there spray pattern changes in the middle of spraying. In essence the pattern shrinks and expands out during painting. When this happens the common term for it is called a “wink”. The issue with a wink is that it negatively effects finish quality due to having a changing spray pattern. In order to avoid this issue and ensure excellent finish quality with an airless it’s important to consider the source of this issue and how to solve it.

Winks occur due to a change in the pressure as the airless units piston travels through its stroke. When a wink occurs is due to the piston not having a controlled movement throughout its stroke. Fortunately, the solution for inconsistent spray is usually one of two things.

1. Your ball checks on the airless unit are not seating.  Airless units have ball checks at each end of their pistons travel. These ball checks seat during the pistons stroke on the end opposite of the pistons motion, which allows material to be transferred and pressure to build. If these checks wear out pressure will not remain consistent during the stroke of the piston in a particular direction. The end result is inconsistent spray patterns. You can usually tell if this is happening by watching the piston during operation.  If it ends up quickly moving through the travel at any point instead of slow and controlled movement you most likely have a worn ball or seat (these are the two components that make up a ball check). Before throwing away your ball check, check to see if you have a reversible ball (some airless units come with a reversible ball that can be used on both sides reducing replacement part cost).
2.  Your packings are worn. Airless units have packings that surround the piston. The packings are like seat checks in that they help maintain pressure but in a different way. Packings prevent fluid pressure from changing due to leaks around the small gap of the piston and piston wall inside the airless pump. Packings allow for fluid pressure to build in the pump which translates into controlled fluid pressure throughout the pumps travel. The end result is a consistent spray pattern. When packings are bad the wink will typically be occurring but with what will seem like a consistent piston movement. Sometimes you will hear the piston moving too fast during the stroke as well is. In either case we always recommend replacing the packings as they are a minor expense and can often be contributing to the problem even if it is primarily the worn seat checks causing the problem.

If you have a piston that is moving too fast the solution is to break the piston down, inspect/replace the ball checks, and replace the packings. To be safe just replace the ball checks to, although they can be a bit of an expense, replacing them will ensure that you do not have to tear the pump down after replacing the packings because you failed to diagnose a failed ball check.