Automated 2-component potting

The industry standard in many sectors

 

Through the potting process parts, mostly electronics, are potted into a housing using 2-component cast resin, or circuit boards are covered with a potting layer. Or component surfaces are covered, often with a transparent protective coating. The potting hardens at room temperature and becomes an integral part of the potted part or final device.

The great advantage is that potting can be achieved through fully or partly automated processing and dispensing. The part application is carried out in an economical and reliable fashion with an automatic SONDERHOFF mixing and dispensing system.

The chemical basis of the 2-component cast resin systems used for this are polyurethane (PU), polyurethane-epoxy mixes or silicone. The chemical and mechanical properties of these plastics can be varied over a broad spectrum. The potting is therefore suited to a wide range of applications.

When the potting has cured, it protects electrical and electronic parts from damp, dust, dirt, temperature, shock and accidental contact. Potting improves the electrical insulation and can be rendered fire-resistant.

 

 

The potting process

 

In the potting process, in contrast to foam sealing, nucleation is left out, as potting is about the production of a compact elastomer without foam structure. The air present in the potting mass (A-component) is completely evacuated by thin film degasification in the storage tank of the potting dispenser system.

The two components, potting polyol and hardener, recirculate in separate pipelines from the reservoirs of the system to the mixing and dispensing head. Gear pumps ensure a constant flow rate. Line valves open the flow of material to the mixing and dispensing head and interrupt it after a time specified in the dispensing programme. Not until reaching the mixing chamber of the dispensing head does an agitator mix the two components in their pre-determined ratio. With electronically regulated rotational speed, the dynamic, homogeneous mixing of the components can be exactly controlled.

Only then does the dispensing and automatic material application begin. After a curing of a few minutes, a bubble-free potting mass is formed.

Automatic potting with the 2-component technology

 

 

The mixing and dispensing systems of the SONDERHOFF DM40x series achieve extremely reliable part processing to create hard to gel-like potting with 2-component technology. They process medium to large batches very efficiently and economically in volume production.

Employing 2-component technology, standard within the industry, the mixing head of the dosing system applies the potting mass in the exact quantity required for the part. This high volume accuracy facilitates the reproduction of identical potting masses to fill cavities of equal size. The varying viscosity of the potting products ensures uniform potting distribution even in the most convoluted cavities of complex components. Bubble-free potting is essential for all-over adhesion to the part surface without any disturbance through air inclusions.

Dynamic mixing, as opposed to static mixing, has the advantage of making the mixing duration and homogenising intensity of the potting components adjustable at any time. Specially developed agitator designs allow gentle mixing after a few turns.

In contrast to volumetric dispensing, which relies on the determination of a constant output volume, SONDERHOFF potting systems measure gravimetrically. They dispense by weight, weighing the exact quantity to be dispensed. By weighing and comparing the dispensed quantity with the set value in the machine programme, deviations are adjusted and the applied quantity kept constant.

A vital reason for the employment of 2-component potting is the ease of automation of the material application on to the industrial components.

 

 

 

Atmospheric plasma treatment  

Successful potting is dependent not only on the potting material and potting system, but also on the upper surface of the part being potted. For example, a dividing layer of fats or dust prevents ideal adhesion between potting material and the upper surface of plastic parts.

Via a plasma nozzle on the mixing head, atmospheric plasma treatment can take place on the part surface directly prior to the potting application. The part is purged of minuscule accretions of organic material down to the narrowest crevice. At the same time, the surface tension is increased, so that the potting can flow into every cavity of the part surface. Through strong chemical bonds an ideal adhesion between potting mass and surface is achieved.