Making sure each of these elements is functional before the molding process is key. This is why it’s important to partner with a plastics manufacturer you can trust. If you’ve worked with a disreputable or inexperienced manufacturer, you may have encountered these defects.
Common Processing-Related Defects:
Burn Marks – Improper ventilation or extended heating of the mold can cause unsightly black or brown carbon deposits.
Blistering – Too much heat or inadequate cooling causes bubbles or raised imperfections.
Stringing – Much like a hot glue gun, stringing happens when the nozzle is too hot and an excess strand of plastic attaches to the part.
Stress Cracking And Crazing – Exposure to high temperature for too long can cause the appearance of crackling or single cracks.
Cold Slugs – When an extra tab of hot plastic becomes attached to the part, it causes a non-uniform area.
Sink Marks And Voids – Poor part design, non-uniform heating and/or inadequate cooling can cause depressions or hollows in a part.
Flow Marks – When a part cools too quickly, it can cause a wavy pattern or discoloration in the part.
Common Mold Design And/Or Maintenance Defects:
Warping – When the cooling system works improperly, the mold can cool unevenly, causing warped, bowed effect.
Drag Marks – Improper or misaligned injector systems can cause scratches when the part is ejected from the mold.
Jetting – Incorrect gate size, length or placement can cause a snake-like line of plastic that cools at a different rate than the main part.
Short Shot – An injection blockage can cause the mold to be improperly filled, which creates an incomplete part, or a short shot.
Flash Or Burrs – If the mold is damaged, poorly designed or there is poor clamping force, a thin protrusion can form beyond the body of the part.
Defects Linked To The Materials:
Splay (Often Called “Silver Streaks”) – These are circular marks caused by excess moisture in the resin. They appear where the molten plastic hits the mold cavity.
Delamination – This is caused by moisture in the pellets. The result is a flaky, crumbly surface layer.
Color Streaks – This is just as the name suggests, random streaks of color in your part. This comes from poorly mixing resins and colorants, or non-uniform ingredients.
Contaminates Embedded In The Material – This is caused by flecks or particles foreign material that often originates in the barrel of the press.
Discoloration – This is caused by residual color in the hopper, usually due to improper flushing or not flushing the hopper at all.
Baytech Plastics Helps You Avoid Defects For A Cost Effective, Clean Production Run
The best advice in avoiding defects in manufactured plastic parts is to pick a manufacturer you can trust. Baytech Plastics have been earning their customer’s trust for over 70 years. Contact us for more information on how we can make every production run defect free.