Triggering thoughts – Spraygun feature
A paint technician has numerous factors to consider before, during and after any paint spraying process. Here, with the help of spraygun experts – DeVilbiss and SATA – we highlight some of the key areas to attend to and gain an insight into ensuring the right mind-set for the task at hand.
It’s a cliché but it’s one which is timeless in its relevance to any ‘finishing’ process – ‘fail to prepare, prepare to fail’. As the technical team at DeVilbiss put it, ‘Preparation is nine tenths of the law, not only the job, but the environment itself, so make sure that the spraying area is clean.’
So it would seem that long before a paint technician has even picked-up a spraygun, preparation is already well underway both physically and mentally. In an operational sense, DeVilbiss always recommends putting down a dirt control product such as DeVilbiss Dirt Control Floor Coat to minimise the risk of dirt inclusion in the paint work. Then, following degreasing the vehicle and tack ragging, DeVilbiss technicians wipe the job over with a DeVilbiss Anti Static Wiper to further reduce the risk of dirt inclusion in the paintwork.
SATA UK Ltd’s managing director, Matt Stevens agrees that the painter will need to have made sure that all the preparation work has been conducted to a high level and that they ensure there is no static build up in plastic components and that the substrate is free from any contamination.
According to DeVilbiss, although it might sound obvious, they are surprised how many painters suddenly find they have problems part way through a paint job. To counter this, they advise to ‘check that the air fed mask is in good working order, there are no breakages and that the visibility through the vizor is nice and clear.’ Another seemingly obvious recommendation DeVilbiss makes is to ensure that the painter selects the correct gun for the application and to check that the correct set-up is installed.
And choosing the right spraygun for the job is something SATA agrees is what might sound obvious, yet key area of consideration. Matt Stevens, managing director, SATA UK Ltd, explains, ‘We, in the UK marketplace, recommend that the basecoat material should be applied using an high volume, low pressure (HVLP) spraygun. This is because the successful application of waterborne basecoat is best achieved by a soft and uniform application, which is easily achieved with HVLP due to the reduced internal air cap pressure creating a fan pattern that ‘lays’ the atomised paint down rather than over atomising it causing patchiness and stripes.’
Matt continued, ‘The clearcoat requires much greater atomisation and the much greater activity created within the air cap of an RP technology (compliant), due to the higher internal air cap pressure, ensures a finer application resulting in greater flow and a peel free finish. However, as we all know, the skill of the painter in some situations is to not get a flat finish but match the inherent ‘orange peel’ of the production vehicle.’
So clearly, a paint technician firstly needs the correct spraygun technology, then requires the correct air cap, fluid tip and needle combination for the material in question. From here, the next step is to ensure that the correct air inlet pressure is being used. According to Matt, ‘It is absolutely vital that the atomising air pressure is not only at the right pressure, but is also perfectly clean and is available in sufficient volume.’
The technical team at DeVilbiss suggest the spraygun pressure is vitally important in order to ensure perfect performance with all types of modern automotive refinish paint, recommending two bar as a good starting point. However, the team suggest some materials will require slightly more or slightly less pressure depending upon their viscosity with exacting spraygun set-up information available online.
With all the aforementioned advice, it is worthwhile back tracking a little and considering the actual spraygun to hand. ‘So far we have assumed that the spraygun about to be used has been perfectly maintained and is ‘ready for action’ however, since we should never assume, a diligent painter will always do a spray test on a piece of masking paper prior to commencing the live job, then he can take any remedial action before the job starts.’
DeVilbiss suggests the painter should be looking for a nice even pattern, which is elliptical with rounded ends. ‘Bear in mind that spraygun performance and indeed fan patterns can change on a job-by-job basis due to a change in the atmospheric conditions, which is why DeVilbiss has developed the Intelligent Atomisation programme whereby a simple change of air cap and fluid tip will maintain perfect performance virtually regardless of climatic conditions.’
With what sounds like a great deal to contemplate with each and every job, it is little wonder the discipline of efficient, high-quality paint spraying is considered an art – and any untrained individual who has ‘given it a go’ will vouch for that.
Matt Stevens said, ‘From our perspective at SATA, a refinish spray painter is a very highly skilled artist as against a scientist. The reason we say that is that there are many trades that can in many cases been completed well by simply following logical steps and using the best equipment.
‘However in the case of a refinish spray painter it is his skill coupled with the various pieces of equipment and materials that combine to make the perfect finish.’
SATA’s three Cs
This applies to the spraygun, the compressed air supply, the actual compressed air-line, the object being sprayed, the painters overalls, the actual paint, as well as the spraybooth itself. Dirt inclusions are his number one enemy.
- Compressed air
Without the correct pressure and constantly regulated volume of perfectly clean compressed air the paint job will be a non-starter. The painter must always be sure that he has set his atomising pressure exactly; this is best achieved with a digital pressure gauge.
It is essential that the spraygun being used is compatible with the task in hand. Once the spra gun technology has been acknowledged it is also key that the correct air cap, fluid tip and needle be selected in terms of size. These three components make up the nozzle set and we believe it is those three individual components, working together in perfect harmony, that are the very heart of a spraygun. No spraygun or even replacement nozzle set leaves the SATA factory without being hand tested.
So by adopting the ‘Three Cs’ the painter will give themself the best chance of a successful paint job. Of course, there are many other issues to consider and do have an effect, but the basics above will certainly make a difference.