How to Resolve Doming Problems when using Cartridges
The enclosed information will resolve your problems. If the domes are not satisfactory, is almost certainly because the resin and hardener have not mixed properly.
Please follow our link below, which will connect you to a short video. This will explain the probable cause of any problems you may encounter when with using the our Doming Cartridges.
Unsatisfactory domes usually result from either an imbalance of the two liquids (Parts A & B) resulting in the resin being out of ratio. or alternatively, the two parts of the polyurethane being improperly mixed at the point of application.
The following instructions should help you to determine and correct any problems:
1) Are the domes that failed at the very start of the cartridge? Before commencing doming a small amount of resin should always be shot to waste first, to balance the pistons on both sides of the cartridge.
It also helps to shoot to waste upwards at a 45 degree angle then rotate the cartridge 180 degrees and do the same - this helps to remove any air in the system which can also give rise to an imbalance in the liquid dispensed from the two sides of the cartridge.
2) The other cause of problems is improper mixing. This is where the customer triggers the gun too quickly. With manual operated dispensing guns customers can accidentally put too much resin through the mixer tubes too quickly. When expressed too fast the parts A & B tend to ‘slide past’ each other in the mixing tube, and so do not mix sufficiently.
Warning, this is particularly common when customers are doing large domes, or doing a lot of doming, when the tendency is to speed up the application of the resin to the surface of the labels.
Both the above points are covered on the short video which can be accessed by using the link provided above.
Curing Bubble Problems in Doming
If you encounter bubbles in the domes the following should resolve the problem.
It is important to point the tip upwards to expel any bubbles in the mixer tub before dispensing on to the surface of the label, to ensure the two liquids are mixed and dispensed at the correct ratio. Out of ratio mixing can give rise to both bubble problems and curing problems resulting in uncured labels with a sticky surface.
Bubbles which are created in the process of doming and which are clearly seen at the time, can be removed either with a needle or other sharp implement, or more easily by the application of heat, which makes the air in the bubble rise to the surface and burst. It is important not to touch the surface of the dome with the flame from the bubble remover gun as this will 'burn off' some of the chemicals in the formula and can cause large gas bubbles due to incorrect ratio. Just hold the flame about 1 inch (25 mm) above the surface of the domes and allow the heat to remove the bubbles.
Bubbles which appear sometime after the domes are dispensed are created by chemical reaction between the liquid polyurethane and the ambient humidity in the doming room. This is why the problem can often be seasonal, because warm air holds more moisture than colder air. For this reason it is important to maintain a consistent temperature of about 72 F (22 C) and relative humidity of 35% in the doming area. Please note that the term is "Relative Humidity" meaning that both the temperature and humidity must be correct, 35% humidity at a higher temperature is not the same as at 72 F. Problems can also be caused by air conditioning which is turned off at night leaving the trays of domes exposed to an increasing humidity as the room becomes warmer.