Following the launch of our 2K series of Conformal Coatings, we have often been asked, “So, how do they work? What are the differences between applying 2K coatings versus traditional solvent based materials?”
To answer this, plus other very frequently asked 2K questions, we have created a series of videos to dispel the myths surrounding areas such as production set up and the application of 2K material. This illustrates how easy it really is to transition to 2K materials.
The first video in this series is now available to watch and covers the basics of how a 2K applicator actually operates.
So, which valves are required for application of 2K materials, and how do they work?
PVA, Nordson Asymtek and Mycronic have specialist 2K valves available which can be retro-fitted to existing production lines. These are The Nordson Asymtek AM range, PVA VPX-2KS and Mycronic MYC50.
Your machine manufacturer will provide you with technical support and assistance with the initial installation of the valves and most technicians familiar with the PVA, Nordson or Mycronic machines should have little trouble assembling them.
This being said, we wanted to briefly cover how the valves worked so as to give you a better understanding of some of the elements to come later in this series, and to highlight the key differences that technicians will need to be aware of both during production and during maintenance.
All the valves essentially work in an identical way; material is fed into the valve as 2K Coating, (referred to as Part A) and the Reaction Agent (referred to as Part B). This can either come from cartridges in the machine as we have here, or external reservoirs depending on the volume of production.
At the stage where material enters the valve, there is really very little difference compared to a normal solvent applicator other than there are two inlets side by side, as opposed to a single valve. However, as the material moves down the valve, it enters into a progressive cavity pump (effectively a helix screw). This consists of a series of cavities, and with each turn the material passess from one cavity to another (hence progressive cavity). The pumps can be spun at different speeds, to accurately control the flow of the two material parts. By selecting the correct speed for each individual pump, the mix ratio of the material can therefore be controlled. The mix ratio is controlled entirely by settings within the software making it easy for the operator to adjust accordingly for different 2K materials. Please refer to the product Technical Data Sheet for the correct mix ratio. The material then passes into a static mixer which, via a series of mixing elements, combines the part A and Part B mixing them together before dispensing.
Finally the material passes through a spray cap which attaches over the mixer. This uses compressed air to atomise the material as it is dispensed, allowing it to be sprayed over an area rather than dispensed in a single line.
So to recap, the key differences compared to solvent coating applicators are the twin progressive cavity pumps, and the static mixer.
Once the 2K material is combined in the static mixer, the curing reaction will commence. This means that unlike solvent coatings whereby you can drop the valve into solvent during line stop to prevent curing, with the 2K material this is not an option. Instead, the material should be purged from the static mixer during idle times. However, the static mixer has been designed to be easily replaceable with a simple interlock system so that if material does cure, or there is an extended idle time, you can simply change the static mixer when you are ready to continue. We generally would not advise material be left in the mixer for prolonged periods of time however.
The Static mixer is the cheapest and easiest component to change should you face blockages and should always be your first port of call should you get any problems during dispensing. It is highly unlikely that blockages should occur higher up the valve as the reaction agent and coating components are separate until they reach the mixer.
Electrolube have worked closely with both PVA ,Nordson and Mycronic to develop these valves to ensure they are suitable for our 2K materials and are happy to offer any further assistance required.
Stay tuned for part 2 of the 2K series.