Experiencing Part Defects and Discontinuities From Molding and Painting Separately

For its backhoe hood and side panels, a leading manufacturer of agricultural and groundskeeping equipment used a production process that included molding and painting the parts separately. This often led to paint defects and part discontinuities. The manufacturer approached EVCO to explore the possibility of eliminating the paint process, using pre-colored resin for the backhoe parts instead.

An Integrated Team Facilitates Transition to Molded-In Color

EVCO Plastics produced the side panels and hood for the backhoe, with the pieces being molded and painted at a separate vendor. EVCO was a member of a fully integrated group—consisting of engineers, toolmakers and a resin manufacturer—to assess the parts and begin the transition to molded-in color.

The goals of the transition included:

  • Eliminating the painting process and paint adhesion issues
  • Increasing the resin rigidity to withstand high impacts
  • Eliminating surface variations caused by the paint process
  • Reducing costs



Enhanced Design and Material Selection Promote Part Success

EVCO was responsible for the part design and injection molding of the parts. The original painted parts had a four-drop manifold gating system, so EVCO began by running mold flow of the painted parts using SLX2271T (SLX) resin. This determined whether they would be able to process the parts with the four-drop manifold using the selected resin.

Next, EVCO ran the molds used for the painted parts in the SLX resin. This step determined cavity pressure, injection pressure, melt temperature, velocity, water flow and knit lines. EVCO ran this test using all four gates and again with only two gates. They then compared the processing results to the mold flow results. The results from molding the parts and mold ow were comparable, which allowed EVCO to pursue the next steps in the process.

The SLX resin is polycarbonate based and is much stiffer to process. Because of that, the original molds would not work for the SLX material. EVCO implemented several versions of mold flow to determine the best location for the gates, the size of the runner system, and the manifold and wall thickness required to fill the parts. With the teams’ collaborative efforts, a part and tool design were determined, eliminating painting and allowing for the SLX material to be used.


A Stronger, Higher-Quality Part

The collective and individual team efforts were paramount to the success of this project. Using the SLX material, the manufacturer not only met but exceeded the goals established at the onset of the project.

Full results included:

  • Eliminating painting and the volatiles released into the environment from the process
  • Eliminating transportation costs from EVCO’s facility in Oshkosh, WI, to the painting vendor    
  • Eliminating transportation costs from EVCO’s
  • Achieving better hood alignment with the SLX material
  • Producing a stronger, stiffer assembly
  • Eliminating all paint defects and discontinuities
  • Improving the visual appearance of the backhoe hood
  • Realizing an annual savings of $820,800

EVCO’s attention to detail and diligent efforts helped the greater team find a cost-effective and high-quality solution. Now, the same team is working with the manufacturer to redesign several other parts using the SLX material, creating additional benefits—and better parts.

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