Since the core / coil assemblies are somewhat different between manufacturers, the following recommendations should be used as a starting point in developing a consistently repeatable casting process. Crosslink Technology Inc. manufactures a number of casting systems, which are finely tuned to achieve excellent results in terms of crack resistance, partial discharge and accuracy.
Although most, if not all, suppliers of formulated Epoxy and Polyurethane materials manufacture products under vacuum. This being the case, there may still be some undesirable trapped gases that appear while using these compounds.
Epoxy compounds are used to cast various shapes and sizes of components. Although epoxies are relatively simple to use, there are some basic steps that must be followed to establish a trouble free casting operation.
At best it is difficult to remove cured material without damaging the encapsulated components. In certain instances however, where the embedded component is reusable, such as an encapsulated conductor, it is worth while to remove the encapsulant and reclaim the embedded part.
Casting large amounts of material present special challenges in processing to minimize the possibility of cracking.
In addition to selecting the correct resin/hardener combination for the job at hand, the following suggestions will help in producing crack free components.
Cast, potted or impregnated devices containing cracks or voids within the insulation are susceptible to corona breakdown during operation. Persistent Partial Discharge (corona) will eventually degrade the insulation to the point where the device will eventually fail.
The following may be considered as standard instructions on how to use Epoxy and Polyurethane compounds in most applications. Since these materials are employed in a wide variety of applications, each with its own peculiarities, some of the steps presented here may not be applicable in all cases. It is best to contact the material supplier for specific instructions, especially for the more unique application of these products.
The purpose of evaluating new epoxy or urethane materials is either to achieve a cost reduction in an existing manufacturing process or there is a new product being introduced. Evaluating new epoxy or polyurethane compounds can be quick and efficient if all the necessary preparations are completed ahead of time and everything is ready on the day of the trial.
Proper surface preparation is critical any time an Epoxy or Polyurethane is used to bond to another surface such as a container in a potting application or when used strictly as an adhesive to bond two or more substrates. Glossy surfaces or oil contamination will drastically reduce the bond strength or prevent bonding altogether.
Vacuum impregnation is used in many different manufacturing processes to enhance mechanical strength, seal surfaces and to enhance electrical insulation properties.
At Crosslink we often get asked what is the difference between pot life and working time? Or, what does green strength mean exactly?
To help better understand the sequence and timeline of curing, we have created the below infographic and definitions for each curing milestone.
