616.368.2684 chris@bluebilles.com

The Problem
“Where will the weld lines be?”  “What is a meld line?”

  • “Weld lines” is term that is used when two plastic flow fronts come together.  Typically, this happens around screw bosses, differential thicknesses in part geometry and multiple gate locations in a part.  Weld lines are a weak condition in the plastic part since these two flow fronts do not mesh together very well upon contact with each other.
  • Weld lines cause weak areas in the part geometry where the part is likely to fail, by strength or is a visual defect where a faint line or gloss variation exists.
  • Typically, the greater the angle of the flow fronts coming together the less dramatic the impact of part performance, this forms a “meld” line (>135°).  The shallower the angle the greater the impact on part performance, referred to as a “weld” line (<135°).Weld Meld Lines
    As the graphic shows, weld lines are red/yellow in color, meld lines become teal/blue.

The Solution
SOLIDWORKS Plastics filling simulation.

  • Weld lines are not eliminated, their impact is minimized with simulation.  After a solution is generated, the analysis can further refine gate locations, recommend geometry changes, etc. to reduce that impact.

Screw boss meld line

How The Solution Helps

  • One issue that is evaluated is “are there any weld lines at the top of the screw boss”?  This could lead to the boss cracking during a screw insertion process.Identification is critical to understand where weld lines may show their face, even though you may not be able to eliminate them, you can accurately predict them.
  • Once identified, part design modifications can be done or if there is an assembly process done with the part, modification of that assembly process can be considered.
  • Without identifying them, you cannot be proactive, you will always be reactive.

Want to know more?  Contact us at:
BlueBill Engineering Services