Ergonomic Spray Gun
One of the tasks that was identified as a priority in the casegoods surveys and review of the OSHA Form 200
Logs were various spraying activities performed by these furniture workers. The ergonomic analysis of these jobs
revealed that these jobs required awkward and extreme wrist and shoulder postures. Specifically, when these
workers were spraying the material on the large horizontal surfaces (like the tops of desk, tables, conference tables
etc.) this activities require extreme shoulder flexion and near maximal ulnar deviation of the dominant wrist. In
addition to the postural risk factors, high trigger depression forces and significant shoulder forces to support the
weight of the spray guns and the hoses that supply the material to the guns were noted. In most cases, this is the only
task that the workers perform, indicating an extended exposure to these risk factors.
Our research team was able to identify a commercially available spray gun that addresses many of the risk factors.
The OMX spray gun manufactured by Devilbiss is made of a light-weight composite. It has an activation trigger for
both a pistol grip and in-line operation to address the concerns about the wrist, and to a lesser degrees shoulder,
postures.
LABORATORY TESTING
A tubular frame was built and covered with paper to replicate the workstation of sprayers in the furniture
manufacturing industry. Due to the fragile nature of the data collection equipment, the subjects could not spray any
fluid from the guns; therefore, the technique was simulated. The gun needs to be held approximately 18 inches from
the work surface. To achieve this, a straw was attached to the gun, extending 18 inches in a straight line. The spray
from the spray gun covers eight inches of the surface; therefore, lines were drawn on the paper approximately eight
inches apart to guide the subject. The orientation of the lines corresponded to the way in which the worker typically
uses the gun in industry. The lines on the top and front panels were horizontal. The lines on the side panels were
vertical. The subject held the spray gun in their right hand and traced the lines with the straw. The goal to simulate the
spraying technique on 4 sides of the frame was to hold the straw perpendicular to the work surface. They used two
different types of guns to complete the trials: standard and OMX. The frame was placed at two different heights for
the trials: low and high, to simulate different sizes of furniture.
These pictures show the testing set-up. The subject is simulating spraying the front of the box (simulating a piece of furniture) in the left-hand picture, and is spraying the top in the right-hand picture. Subjects also simulated spraying the side of the box.
Results
The most important results from this evaluation showed considerable reduction in awkward wrist postures with the
OMX spray gun. The differences in productivity were negligible.
This picture shows the wrist posture assumed as the subject simulates spraying the top of a piece of furniture using the traditional gun.
This picture shows the wrist posture assumed while using the OMX gun to perform the same task.
For more information about ergonomic interventions for the furniture manufacturing industry, please contact:
Dr. Gary Mirka, Professor of Industrial Engineering at North Carolina State University