IMD&IML Injection Molding

What is IMD?

① The product offers exceptional durability and scratch resistance.

② Complex visual designs can be easily achieved with consistent results, something other processes cannot match.

③ It supports a wide range of colors, even in small production runs, including the ability to print over four colors and metallic inks.

④ Design changes can be made without requiring additional molds, leading to substantial cost reductions.

⑤ One-piece molding exclude the need for color separation and disassembly, accelerating the design and development process.

⑥ The product features high color contrast, and the plastic material allows light transmission, making it ideal for screens and light guide columns.

⑦ The product has excellent chemical resistance due to its extremely durable and flexible surface printing. The image is actually printed on the inside of the film.

⑧ Plastics and films can be recycled and reused.

⑨ The product can meet precision requirements and enable efficient mass production through automation.

Since IMD ink can withstand temperatures between 250-260°C for 3-4 seconds, designing the injection mold requires careful consideration of factors such as injection pressure, injection time, gate size and quantity, and the material’s physical properties. To achieve low injection pressure and short injection times, the following methods can be considered:

① A shorter runner design is preferable, with hot runners being the ideal choice.

② Consider increasing the gate area or using multi-point gates.

③ Opt for plastics that have better flow and inject them at a lower temperature.

④ To prevent ink from being flushed out, add it at the gate.

⑤ Ensure that the IMD injection mold cavity and mold shape align properly.

⑥ Avoid selecting the highest stretch points for the injection material, usually at the four corners, as these areas are thinner, expand and contract more, and are prone to wrinkles.

⑦ Since IMD injection conditions tend to be consistent, using an injection molding machine with superior control is recommended. Additionally, the plastic’s physical properties should be uniform.

⑧ Since the FILM expands and contracts with temperature changes, the mold temperature should not be too high during molding. Using a mold temperature machine is a good approach.

⑨ The presence of film inside causes thicker areas to shrink more. Traditional methods like holding pressure and overpacking won’t solve the shrinkage issue. The solution lies in reducing the material and making the part hollow.

What are the process steps of IML injection molding?

Trimming → Surface printing → Ink drying and setting → Applying protective film → Drilling positioning holes → Heat forming → Shaping peripheral edges → Injection molding procedure. The specific instructions are as follows:

• Cutting: Cut the rolled film into square blocks of the specified size for use in the printing and molding processes.
• Flat Printing: Print the required icons and text onto the cut square film to create the film web.
• Ink Drying and Fixing: Place the printed film squares in a high-temperature oven to dry and fix the IML ink.
• Apply Protective Film: Apply one or two layers of protective film to prevent surface scratches during the punching of positioning holes.
• Punch Positioning Holes: Accurately punch the positioning holes required for thermoforming. In some cases, the holes for the shearing process may need to be punched in advance.
• Thermoforming (High Pressure or Copper Mold): After heating the printed film, use a high-pressure machine or copper mold to shape the film while it is still hot.
• Cut the Peripheral Shape: Trim off the excess material from the formed three-dimensional film to create the desired shape.
• Injection Molding Process: Place the molded film, which matches the exact three-dimensional shape of the front mold, onto the front mold and proceed with the injection molding to complete the IML product.

① Injection Molding Thickness: It is recommended that the average flesh thickness should not be less than 1.2 mm (excluding the Film, the thickness should be 1.0 mm).
② Film Thickness Specifications: The standard thickness for film is 0.1 mm, 0.125 mm, and 0.175 mm.
③ Film Single-Piece Printing: Single-piece printing is best suited for small production runs and situations requiring various design options.
④ Color Limitations: This method is not recommended for metallic colors such as electroplated silver when the appearance color is bright silver, as temperature fluctuations may cause the film to peel off.
⑤ Film Edge Size: The size of the film’s outer edge is directly linked to the size of the mold cavity. If the film edge is too small or too large, it can cause mold cavity stretching during injection and lead to edge leakage.
⑥ Minimum Hole Diameter: The minimum diameter for round holes on the lens is Φ1.0 mm.
⑦ Lens P.L Position: The P.L of the lens is typically positioned at the bottom. If there are issues with the draft angle, it can be located 0.2 mm from the lower edge of the film coating.
⑧ Lens Draft Angle: The draft angle for the lens is generally 3 degrees.
⑨ Lens Appearance: For lenses with differing appearances, the film must be pre-formed before the injection molding process.
⑩ Rounded Corner Design: IMD/IML molding cannot create sharp edges. The appearance outline should avoid sharp corners, and all corners must have a rounded radius of at least 0.3R.
⑪ Hemming Issue: Hemming refers to the edge where the film and plastic meet, which may not be very clean after injection molding. To address this, the product design can incorporate plastic parts to cover the edge where the film and plastic connect.
⑫ Requirement for Surface Wear Resistance Hardness: The product surface must achieve a wear resistance hardness rating of above 3H to guarantee long-term durability.

How to test and verify IML products?

Testing and verifying IML (In-Mold Labeling) products is crucial to ensure they meet required standards and specifications. Here are key methods to test and verify IML products:

• Hardness Test: Use a polished 2H~3H pencil with a 500g force and push it flatly towards the surface of the product at a 45-degree angle. If the surface shows no obvious scratches or marks, it is considered qualified.
• Temperature Test: Place the product in a furnace with a relative humidity of 95%-100% and a temperature of 57±3°C for 48 hours. If there is no bursting, discoloration, deformation, color loss, or loss of function, it passes the test.
• Wear Resistance Test: Rub a rubber with a 500g weight back and forth 300 times (one back and forth equals one cycle) at the same spot, with a length of 2 inches. If no obvious wear or degradation occurs on the surface, it is considered qualified.
• Sand Washing Test: The fixed test coating is placed at a 45-degree angle with the friction instrument. The coating surface is washed using the specified sand amount and flow rate (2 liters/21~23.5 seconds) until 500ml of sand grains have been applied. If the material beneath the paint becomes visible after washing with 500ml of sand, it is considered a serious defect. If it becomes visible after 100ml of sand, it is considered a minor defect; If minor defects exceed 20% of the total samples or if serious defects exceed the total number of samples, the product is considered unqualified.