Automatic Adhesive Injection Machine for Can Lid

Automatic Adhesive Injection Machine for Can Lid

Most adhesive injection machines (using the Graco injection machine as an example) are suitable for water-based and solvent-based sealing adhesives. They can handle can lids with diameters ranging from 50 to 127 mm, achieving an output speed of 100 to 500 lids per minute in a single channel. The injection machine operates in a reciprocating manner, utilizing both single and dual-channel injection. The injection process involves moving the can lids from a stacking device to a rotating clamp, where a set amount of adhesive is injected to achieve appropriate distribution. Typically, the lids are transported from the punching machine via a conveyor belt to the stacking device.

In each mechanical cycle, each lid is separated from the stacked feed by a cutting blade on a feed rod. The feed rod then conveys the lid to the rotating clamp, and a lift cam raises the clamp to the injection position. The lid is pressed down by a top press, after which a mechanically or electronically controlled injection gun injects the sealing adhesive into the lid. Once injection is complete, the clamp returns the lid to the machine's flat surface, and the feed rod transfers the lid to the conveyor belt.

Adhesive Film Volume

The volume of the dry adhesive film depends on the size of the can, the type of can, the type of roll seal, and the nature of the contents being canned or packaged. Adhesive suppliers can recommend the appropriate amount of adhesive based on specific circumstances.

The correct adhesive volume will provide:

1. Sufficient adhesive to fill the gaps;

2. Adequate adhesive being compressed to enhance resistance to damage;

3. The adhesive itself should not interfere with the formation of the double roll seal or lead to adhesive overflow.

Measuring the volume of the adhesive film can be challenging; instead, the more easily measurable adhesive film weight is used. Once the adhesive film volume is determined, it can be converted to weight by multiplying the adhesive film volume by the relative density of the dry adhesive.

Dry adhesive film volume /mm3 = Dry adhesive film weight / mg

Relative Density of the Dry Adhesive Film

Factors influencing the dry adhesive film volume on the can lid include:

1. The viscosity and total solid content of the adhesive;

2. Injection conditions.

Generally, the total solid content and viscosity of the adhesive are predetermined during manufacturing, with no significant variation between batches. The viscosity of the adhesive is affected by temperature, and significant changes in adhesive injection temperature may require adjustments to the injection conditions.

Before use, the adhesive should undergo pre-treatment to ensure uniformity and consistency in injection. All adhesives should be stirred or pre-treated before being transported to the injection machine.

Injection conditions significantly affect the final adhesive volume. In principle, for solvent-based can sealing adhesives, the injection pressure should be within the range of 30 to 50 psi (206.84 to 344.74 kPa), while for water-based adhesives, it should be between 15 to 30 psi (103.42 to 206.84 kPa). Changes in the nozzle aperture (0.5 to 0.9 mm) may alter the pressure required to achieve the desired adhesive volume. Required pressure is also influenced by the needle opening time and injection time. Ideally, during the needle opening time for 2+ and 3+ rolls, adjustments to the uniformity and volume of injection should be made by altering the nozzle aperture size, injection temperature, and pressure.