SPRAY GUN TECHNIQUE - Vivilon

1 SPRAY GUN TECHNIQUEPAGE 1 SPRAY GUN TECHNIQUEPAGE 1 SPRAY GUNTECHNIQUESPRAY GUN TECHNIQUEPAGE 2 SPRAY GUN TECHNIQUEPAGE 2 SPRAY Gun Motion StudyIn finishing any component the mostefficient combination of SPRAY gunmovements must be carefully planned inorder to produce the best results. At thesame time the parameters within whichthe gun operates best must also beconsidered. The following notes areintended to highlight the best way to usethe gun. Before commencing spraying it isadvisable that an operator becomesfamiliar with the gun and surface to becoated by spraying some practice panelsto save time and rejects during Stroke (Pass)The SPRAY gun stroke, or pass, is made by Fig 1a moving the gun parallel to the work andperpendicular (at right angles) to thesurface.

2 The distance from the gun to thework, for Conventional Air Atomisingguns, should normally be between 6 and8 inches. A simple way to measure this touse your hand. A closed hand (withfingers and thumb together) measuresapproximately 5 inches wide and an openhand (with fingers and thumb apart)measures approximately 8 inches (asshown in figures 1a and 1b).Spraying should be carried out withstraight uniform strokes moving acrossthe surface in such a way that the spraypattern overlaps the previous stroke by aminimum of 50%. While this percentage Fig 1b may need to be increased for certaincoating types, once established, it mustremain constant for the duration of thework. Failure to do so will result in unevencoating thickness and poor visualappearance.

3 If the gun is held too close tothe work surface, more paint will beFig 2. deposited and the gun will need to bemoved faster to prevent runs and sagsand possible solvent , if the gun is held too far fromthe work, the atomised droplets may drycompletely before coming into contactSPRAY GUN TECHNIQUEPAGE 3 SPRAY GUN TECHNIQUEPAGE 3with the work surface, causing excessivespray dust and dry SPRAY , (as shown inFigure 2).The relation between the gundistance and the stroke speed is easier tosee when actually spraying. The sprayerwill soon become experienced in movingthe gun target distance closer or furtheraway to permit a comfortable speed,while depositing a full wet coating ofmaterial. Remember at all times that theConventional Air Atomising gun isFig 3.

4 Designed to SPRAY at 6 - 8 inches anddeviation from this distance by alteringfluid flows and air pressures is not goodpractice. It could lead to other paint gun must not be excessively arced ortilted while spraying, as shown in Figures3 and 4. In certain types of work it isnecessary to tilt the gun but this shouldonly be done when it is not possible touse the correct gun the GunThe gun must be held at right angles tothe sprayed surface at all times. Figure 4shows the correct position in which thegun should be held, and also the incorrectin dotted lines. It is especially important toremember this when spraying particularlyFig 4 SPRAY gun should be held perpendicular to thesurface as shown here by solid lines. Tilting the gunup or down gives an uneven SPRAY pattern andmaterial deposition low or high surfaces where holding thegun at right angles takes more effort onthe part of the sprayer.

5 Failure to do thiswill result in heavy and light bands ofmaterial caused by the deformed spraypattern shape brought about by theincorrect angle of the gun trigger controls the quantity ofmaterial emitted from the fluid tip, and theoperator needs to learn how to correctlyuse it to achieve the most efficientspraying TECHNIQUE . As the trigger ispulled back the flow of material adjustment of the fluid flow isnormally necessary when sprayingcomplicated or intricate components. It istherefore important to become familiar tothe trigger feel to prevent deposition oftoo much coating on certain areas of thecomponent. Correct use of the trigger willalso reduce the amount of paint wastedand contamination in the SPRAY GUN TECHNIQUEPAGE 4 SPRAY GUN TECHNIQUEPAGE 4 Spraying a PanelThe basic TECHNIQUE of spraying a flatpanel is shown in Figure 5.

6 The stroke isstarted off the work and the trigger ispulled only when the gun is moving andabout to pass over the edge of the trigger is released at the other edgeof the panel but the stroke is continued afew inches before reversing direction forthe second pass. The point at which thegun is triggered is one of the mostimportant factors of the SPRAY gun must follow the precise shape ofthe work, maintaining full coverage overthe wok with minimum waste in 5 When spraying a panel use alternate right and leftstrokes, triggering the gun at the beginning and endof each stroke. The SPRAY pattern should overlap atleast one-half of the previous stroke for evencoverage without order to reduce overspray and wastesome sprayers use an end stoke TECHNIQUE as shown in Figure 6.

7 The firstsingle vertical stroke at each end of thepanel allows the gun to be triggered offjust before the panel edge. This methodstill assures complete coverage but helpsreduce paint waste which results whenspraying up to and over the vertical edgewith the usual horizontal workFig 6 End Strokes - Vertical strokes sprayed at theends of a panel help reduce overspray fromhorizontal strokesA long panel can be sprayed with verticalstrokes, but most sprayers have bettercontrol with the more natural horizontalstroke. The panel should therefore besprayed in several separate sectionstypically 18 to 36 inches long (acomfortable reach of the sprayers gunarm) as shown in Figure 7. This methodwill use the same triggering action as witha smaller panel, but eachsection must overlap the previous one byabout four inches.

8 By feathering the gunFig 7 Long Work is sprayed in sections of convenientlength, each section overlapping the previoussection by approx 4 inchesSPRAY GUN TECHNIQUEPAGE 5 SPRAY GUN TECHNIQUEPAGE 5trigger and slightly arcing the gun for thisfour inches, heavy material depositionfrom two full coats can be avoided. Donot attempt to SPRAY the complete panellength in one pass - this will easily lead tooverlap and target distance SurfacesWhen spraying horizontal surfaces oneoption is for the SPRAY strokes to start atthe near side of the work as shown inFigure is essential where rapidly dryingmaterials ( cellulose lacquer) areFig 8 Start at near edge to avoid depositing dry SPRAY onalready coated work. used, as drying droplets from thebounce-back landing on wet work can drywith a sandy finish.

9 A very small amountof gun tilt is usually needed for horizontalsurfaces to sweep the bounce-backtoward the far edge. The newly depositedwet coat will tend to bury any dry sprayalready deposited on the opposite action is also acceptable (iestarting at the far side and sweeping towardss the sprayers body. However, thesprayer himself will become covered indry spraying horizontal surfaces toowide to be coated from a single side it iscommon to start at the near side andspray towards the middle using the sweeping TECHNIQUE described reaching the middle the sprayer willmove around to the far side and sprayfrom the middle to the new near edge,again sweeping the dryspray, but thistime towards the sprayers latter TECHNIQUE is typically usedwhen spraying the roof and bonnet ofcars, as it has the advantage of keepingthe wet edge , allowing wet paintdeposited by SPRAY strokes to merge intothat deposited by the previous strokeacross the complete surface.)

10 Care must be taken not to allowthe sprayer or the gun hose to touch thewet surface while the GunWhere a suction feed SPRAY gun is usedon work that requires the gun to be tilted,care must be taken to ensure that the tiltis not excessive as the paint may clog theair vent in the cup lid and interfere withmaterial flow. As an alternative the air capcan be rotated to keep the gun and cupvertical while the SPRAY fan is spraying at an upward angle for anylength of time one option is to rotate thecomplete cup assembly through 180degrees so that the air vent lies in front ofthe fluid inlet, and the fluid tube, withinthe cup, curves to where the material willlie when the gun is tilted. An even betteridea is to use a pressure feed GUN TECHNIQUEPAGE 6 SPRAY GUN TECHNIQUEPAGE 6 Outside Edges and CornersFig 9 Edges and Corners should be done first, sprayingdirectly at the corner to catch both surfaces withone stroke of the gun.