1. Size of dispensing
According to work experience, glue dot diameter should be half of product spacing. This ensures that there is enough glue to glue the components and avoid too much glue. The amount of dispensing depends on the time. In practice, the dispensing time should be selected according to the production conditions (room temperature, glue viscosity, etc.).
2. Dispensing pressure
The dispensing machine equipment provides a certain pressure to the needle tube (glue gun) to ensure glue supply. The pressure determines the glue supply and glue flow rate. Too much pressure is easy to cause glue overflow, too much glue; too little pressure will appear dispensing discontinuity and leakage, resulting in product defects. The pressure should be chosen according to the nature of glue and the temperature of working environment. The high ambient temperature will make the viscosity of the glue smaller and the fluidity better. At this time, it is necessary to adjust the low pressure value, and vice versa.
3, needle size
In practice, the inner diameter of the needle should be about 1/2 of the size of the dispensing spot. In dispensing process, the dispensing needle should be selected according to the size of the product. Different needles should be selected for products with different sizes, which can not only ensure the quality of adhesive paste, but also improve production efficiency.
4. The distance between the needle and the working face.
Different dispensing machines use different needles, and some needles have a certain degree of stoppage. The calibration of the distance between the needle and the working face should be done before the start of work, that is, the height calibration of the Z axis.
5. Viscosity of glue
The viscosity of glue directly affects the quality of dispensing. If the viscosity is high, the adhesive point will become small, or even wire drawing; if the viscosity is low, the adhesive point will become large, and then the product may be infiltrated. During the dispensing process, reasonable pressure and dispensing speed should be selected for glue with different viscosity.
6. Glue temperature
General epoxy resin glue should be stored in the refrigerator at 0 ~ 5 C, take out half an hour before use, so that the glue temperature and working environment consistent. The usage temperature of the glue should be 23 25 C. The ambient temperature has a great influence on the viscosity of the glue. The viscosity of the glue increases with the decrease of temperature, and the flow rate of the glue decreases correspondingly, which makes the wire drawing easier. Under the same other conditions, the difference of ambient temperature of 5 C will cause 50% change of the gel yield, so the ambient temperature should be controlled. At the same time, the temperature of the environment should also be guaranteed. If the temperature is too high, the adhesive point will become dry and affect the cohesive force.
7. Curing temperature curve
For the curing of glue, the temperature curve has been given by the general manufacturer. In practice, the higher temperature should be used to solidify the glue so that the glue has enough strength after curing.
8. Bubbles
Glue must not have bubbles. A small bubble will cause many products without glue; each time the replacement of rubber hose should be emptied at the junction of the air, to prevent the occurrence of air striking phenomenon.
9. Special fluids are needed.
Instant glue: Use safety piston and Teflon lined metal needle for water instant glue, use tapered oblique needle for thick instant glue, and use PP needle for flexibility.
UV glue: Use amber syringe, white piston and oblique needle (UV shielding). If you use other kinds of needle, please make a needle which can shield UV.
UV curing adhesive: use black opaque syringe to avoid photosensitivity.
Anaerobic adhesive: use 10CC syringe and white PE general piston.
Sealant and paste fluid: If the use of white piston rebound is serious, please use a safe type of flexible, use oblique needle.