As the raw material for silkscreen printing, ink requires the features of wear resistance, high temperature resistance and easy mixing. There are two types: solvent-based ink and light-curing ink.

 

Solvent-based ink

 

After silkscreen printing with solvent-based ink, plastic pieces needs to be dried in a three-stage dryer with good ventilation. For the last stage, it is recommended to dry at a constant temperature of 90℃ for 3-5h.

 

Therefore, the production cycle of solvent-based ink is long, and once the drying degree of the ink is not well controlled, it will have bad impact on the final injection molding.

 

Solvent-based inks do not dry completely after printing, residual solvents remain in the ink. When the solvent is heated in the injection mold, it cannot escape, and will diffuse into the ink inside and outside. When the pressure of solvent vapor is high, the pattern and text will be blurred.

 

Light-curing ink

 

Application of light-curing ink in IMD

 

1. Automatic printing with high production efficiency.

 

2. It can print finer lines with high resolution, thinner ink layer and larger printing area.

 

3. Before injection molding, if the UV ink is not coated, there will be no splashing of the ink.

 

4. UV ink has a small amount of solvent, so it does not require a long time to evaporate or dry the solvent. Therefore, during injection molding, the ink will not splash when heated.

 

Some issues (reasons & solutions)

 

The ink is dispersed during injection molding.

 

1. You have chosen wrong ink

 

Special IMD ink is good.

 

2. Improper viscosity before printing leads to problems such as pinholes or poor leveling in the ink layer.

 

You should use special diluent to adjust to appropriate viscosity.

 

3. Improper addition of ink additives

 

Additives should be added in the prescribed proportion.

 

4. The ink is not completely dried, and there is residual solvent.

 

The drying temperature should be higher, or the drying time should be extended. The density of product placement should be reduced.

 

5. The thickness of plastic pieces is not appropriate, and the ink dispersion area increases with the increased thickness of plastic pieces.

 

You should reduce the thickness of plastic pieces.

 

6. The ink layer is too thin.

 

You can use a finer screen. Appropriately reduce the hardness of the squeegee, and reduce the angular velocity of the scraper to increase the amount of ink and the thickness of the ink layer.

 

Another reason is that the design, shape and distribution of the injection port are unreasonable. They need to be improved.

 

7. The injection temperature is too low.

 

The temperature of resin should be increased to reduce the ink dispersion area. The temperature is related to the type of material and the structure of the injection mold.

 

Plastic pieces and ink are easy to separate.

 

1. The bonding between them is poor.

 

The plastic pieces or ink should be replaced.

 

2. There are residual solvents in ink.

 

The drying temperature should be increased, or the drying time should be extended. The density of product placement should be reduced.

 

3. The ink has too many pigments (such as silver), which does not match the injection molding.

 

The proportion of pigment should be appropriately reduced.

 

4. The design of the pattern is unreasonable. For example, the mirror ink pattern is printed on the curved edge.

 

The design should be modified.

 

5. Improper drying of adhesive

 

Drying methods should be improved.

 

6. Improper control of injection temperature, pressure and cooling system.

 

You need to take improvement measures.

 

7. The injection plastic contains moisture.

 

Preheat the material to remove water.

 

8. Improper material of injection molding or poor quality.

 

Choose right material, or replace with new one.