Why do spray guns break down more often when using white primers?

The major furniture manufacturers are continually faced with a demanding external market that is demanding ever lower prices, a market they must take into account if they want to stay in the game. Many of them are choosing the right path - re-engineering - for both woodworking and furniture finishing. Finishing lines with automatic spray guns ensure consistent film quality, reduce wastage and labour costs. But continued pressure on prices is also seen in negotiations for ancillary materials, with varnishes and paints directly targeted. And so some economical products emerge that produce equally beautiful and durable films. Only, the spray guns on automatic lines end up breaking down much faster. Why? I try to answer that question below.

Changes in finishing materials affecting spray gun parameters

It's hard to understand what happens when all of a sudden nozzles and gun barrels fail more often than at other times and need to be replaced for quality production. As nothing seems to have changed in the meantime, the conclusion is that the guns are to blame. Sometimes it may be the primer or varnish used. Even if the product remains the same, the raw materials included can be changed.

Price pressure is driving paint and varnish producers to find cheaper raw materials. In good faith, they want to maintain the final quality of the film and its mechanical and physico-chemical resistance. A finishing product is composed of resins that determine its basic properties (acrylic, urea, ester), solvents, auxiliary materials that determine certain properties (stretching, thixotropy) and fillers. In order not to alter the basic properties of the product, the only materials that can be replaced or modified are fillers.

Such changes, which do not require a change of product name or code, are mainly made to white or coloured water-based primers and paints. Talc, chalk or other fillers can be replaced with similar, cheaper materials. The main qualities of the product do not change. However, the grains of the new fillers may be harder, more abrasive. This leads to changes in the parameters of spray gun nozzles, especially those working in the Airmix system, and other components that come into direct contact with the finishing products.

As a result, the guns used will suffer more if they are not made of durable materials. Spray gun and spray equipment manufacturers have adapted to the new conditions and are producing special, more resistant guns for primers and water-based white lacquers. Automatic airless guns ASI 24 and ASI 40 from Sames Kremlin are such products.

Sames Kremlin spray guns with increased resistance

The ASI 24 and ASI 40 are spray guns recommended for applying hard and/or abrasive materials. You can also find them in your country at the French company's distributor, Falk Consulting. The main advantages of these guns are:

• simple construction with a small number of components;
• durability;
• low maintenance cost,
• compact and lightweight;
• easy to clean and change.

Works in Airless system which makes them very suitable for factories where high productivity is needed. The atomisation of the spray product is very fine and the material flow continuous and constant. It results in a good quality film even if the applied product is hard or abrasive.

The strength of the gun is given by the use of steel for the inner passages, nozzle and rods treated to resist abrasion. The tip of the rod that closes the nozzle orifice is made of nickel carbide, ensuring spray consistency even when using difficult products such as UV or waterborne primers with abrasive fillers. The nozzle is mounted directly to the gun's diaphragm, without any other intermediate parts.

Such a spray gun, even though it may seem expensive at first, is a good investment because it ensures long use with consistent film quality. Gun nozzle failure at high flow rates and a finishing line travel speed of a few metres per minute means a large number of broken parts. And if this happens often it means big losses of material and time. That's why I think the philosophy of the Englishman who says he's too poor to buy a cheap coat also fits very well in industry. By approaching things this way there is a real chance of being able to lower production costs and enter the foreign furniture market at competitive prices.