Due to the varying materials used in each product, defects occasionally occur in the IMD injection molding process. For instance, rigid plastic products often exhibit ripple marks. So, what causes these ripple marks, and how can they be effectively resolved? Causes of Ripple Marks in Injection Molding In rigid plastics like PS, dense ripple patterns often form near the gate, centered around it—this phenomenon is known as ripple marks. The primary cause is the high viscosity of the melt, which leads to sluggish flow during mold filling. When the leading edge of the melt contacts the cavity surface, it cools and contracts quickly, while the following melt expands and continues forward. This alternating effect results in the formation of ripple marks on the surface. 
Solutions for Eliminating Ripple Marks in Injection Molding
- Increase Barrel and Nozzle Temperatures: Raise mold temperatures simultaneously to reduce melt viscosity.
- Increase Injection Pressure and Speed: Enhance pressure and speed to ensure the melt fills the mold cavity quickly.
- Optimize Runner and Gate Dimensions: Design runners and gates appropriately to prevent excessive flow resistance.
- Ensure Proper Mold Ventilation: Set sufficiently large cold wells to improve ventilation.
- Avoid Overly Thin Product Design: Design the product with adequate thickness to prevent ripple marks due to thinness.
DAYIN Plastic Products Co., Ltd. is a high-tech enterprise specializing in product R&D, design, manufacturing, and sales services, offering one-stop solutions. Since its establishment in 1989, we have focused on mold making, injection molding, post-processing, and electronic assembly. In addition to contract manufacturing, we develop our own products and support clients with private label production. Our facilities cover 50,000 square meters, with 30 years of mold development experience, over 50 R&D staff, and more than 100 injection molding machines, dedicated to delivering high-quality manufacturing services to our clients.
IMD Ripple Marks: Reading the Film’s Complaint
In-mold decoration produces ripple marks when the film complains. Reading the complaint:
| Ripple signature | The film’s complaint | The fix that answers it |
|---|---|---|
| Waves at fill start | Initial jet too fast, film shoved | Slowed first-stage injection profile |
| Ripples near gates | Shear heat localising | Gate size or position review |
| Wrinkle arcs at corners | Film mismatched to cavity stretch | Formable film grade or geometry relief |
| Random dull patches | Moisture in film or resin | Drying discipline for both layers |
The first-stage row is IMD’s most common confession: conventional injection profiles fill fast for cycle reasons, and the film — a delicate passenger — records the speed as waves exactly where the melt arrives. Slowing the first stage costs fractions of a second and removes the majority of ripple complaints, which makes it the cheapest conversation in IMD troubleshooting. The corner row is the geometry lesson: films stretch where cavities fold, and wrinkles map the mismatch between printed flat film and three-dimensional cavity — solvable by film grade, by geometry softening, or by accepting the ripple as texture. IMD’s appeal — decoration that survives the part’s life — depends on this reading skill, because the film reports every process liberty taken with it. The gloss harmony IMD enables is in unique gloss techniques, and the contamination stakes in contamination control. Reference: in-mold decoration and fill dynamics.