For a long time dispensing epoxies has been a difficult process for manufacturers. They can cause clogging of the dispensers and require cleaning of the machinery for each and every run. The clogging and cleaning process leads to lengthening of the process and increase in costs.
Controlling temperature and the rate of the process requires some skill on the part of the handler. Temperature variations can cause considerable variations of the viscosity of the fluid, which in turn will cause errors during manufacturing. If the temperature does not remain constant the adhesive will be ruined. The aim is to maintain temperature and precision while at the same time keeping up the rate of the process.
Types of Epoxies
There are two main types of epoxies used in the manufacturing process. There is the liquid epoxy and the Preforms. The liquid ones are more prone to polymerization due to temperature variations. They clog the needles and they do not guarantee accuracy when placing the adhesive on the material. These liquid adhesives take longer to place on the material.
They are however preferred because they are much cheaper and help to cut down costs. They are more cost effective for applications of relatively bigger sizes.
Preforms on the other hand are much more accurate compared to liquid types. They are pre-designed or 'pre-formed' to fit dimensions of different sizes and shapes. They are best for dimensions of 0.05 inches or less because of their precision. Placing the preforms on the parts is much faster and easier when using both impregnation machines and using the manual system. It provides a more predictable viscosity which is what makes it more predictable.
Types of Processes
The problem with performs is that they can be costly even though they are more suitable for a high volume manufacturing process. The may not be suitable for sealing certain materials due to their high temperature rating. In such a case liquid adhesives may be used to match the low temperature rating of the materials in question.
Stencil Printing and Nozzle Dispensing
One industrial method commonly used for dispensing epoxies is Stencil printing. A squeegee is used to apply the resin over the stencil and onto the material to get the required pattern. This method can be used to rapidly apply the epoxy, but it may demand that the stencil be cleaned often. The materials making the squeegee will also determine the speed and efficacy of the process.
Nozzle and needle forces the resin through the point of the needle by applying pressure. The desired pattern can be achieved by using the timed pumps that dispense at regular intervals. Complex lines and patterns can be achieved this way. The jet method is somewhat similar but it forces the resin through a jet. This is done to avoid contact with the material. The desired pattern and larger dots are achieved by repeating the dots a number of times. Whether it is an epoxy or plasma adhesion treatment, the most important thing is to ensure that the right machine and tools are used.
