You will acquire systematic insights into the equipment needed in a paint shop. Some of the products are illustrated to enable you to understand the basics of the equipment.
When you have finished reading the module, you will be more familiar with the functions of the individual pieces of equipment, their use and the steps required to work with them.
EQUIPMENT PRESSURE SETTING
The work in a body shop involves many different working steps, and different kinds of tools and equipment are necessary of each of these steps. Apart from the basic knowledge about the different equipment, professional maintenance and care of the tools is a basic requirement for professional use. Only in this way can a simple, fast and satisfactory work result be achieved.
BASIC KNOWLEDGE-FINISHING & POLISHING
UV PRIMER FILLER PROCESS
DRYING PROCESSES / SYSTEMS
HEALTH AND SAFETY
Wear safety glasses
Wear protective shoes
Wear standard overall
Wear spray mask
Use dust mask
- BASIC KNOWLEDGE-HEALTH & SAFETY
A spray gun is a piece of equipment that atomizes compressed air with fluid paint. Due to this atomization it is possible to obtain a smooth paint finish.
A wide range of spray guns are tested for application of the products and are approved based on the results.
In principle, you can use spray guns with HVLP technology as well as other approved spray guns. However, spray guns with HVLP technology are preferred because they offer a significantly higher transfer rate. Please see the Equipment manual (SPRAY GUN TYPES AND APPROVAL) for the recommended spray gun settings, nozzle, air cap and inlet pressure.
Overview of spray guns:
- HVLP (High Volume Low Pressure)
- RP (Reduced Pressure)
- Mini Jet
Owing to the low atomization pressure at the nozzle for the HVLP spray gun, the spray gun is guided at an approximate distance of only 10 to 15 cm from the object to be painted.
You must guide the spray gun parallel to the object. You should follow the shape of the body with the spray jet, even on vertical surfaces.
For horizontal surfaces, such as the hood, perfect spraying action is critical for achieving a perfect finish.
Overlapping of the spray pass
The overlapping zone of the spray pass is around 75%.
To achieve the best result, it is important to use the correct spray gun with the correct settings for the products being used.
The nozzle size and spray pressure are always mentioned on the product and in the product information.
The other settings like speed, distance, angle to object and overlaps also influence the end result. These are “soft” settings and need to be adjusted by the painter.
All the settings must be compatible to achieve the best result.
Too slow and/or too close can cause runs.
Too wet, too dry or bad overlaps can cause mottling in the metallic basecoat:
(2) Wet (More colorful, darker)
(3) Dry (More silver, lighter)
Position of the aluminium particles
It is imperative that the spray guns are cleaned and dried after use.
Even the smallest contamination can have an impact on the end result.
PICTURES WITH THE DIFFERENT SPRAY PATTERNS:
|Optimum spray pattern||Sickle-shaped spray pattern||Pear-like or oval spray pattern||split spray pattern (Resembling a swallow;s tail)||Jet flutters|
1 Optimum spray pattern: In order to achieve an even spray pattern, make sure all bore holes are absolutely clean. It may impair the spray jet if you use objects for cleaning that are too hard. A damaged needle will also lead to an uneven spray pattern.
2 Sickle-shaped spray pattern: Cause: the full compressed air jet of a clean horn bore presses the flat jet to the clogged side.
3 Pearl-like or oval spray pattern: Cause: Contamination of spray nozzle or air outlet. Turn the air cap by 180 degrees. Clean the air cap and the nozzle if the uneven spray pattern remains unchanged. Clean the air cap if the spray defect keeps moving around.
4 Split spray pattern (resembling a swallow’s tail): Possible causes:
4.1. Atomizing pressure is insufficient.
4.2 Paint nozzle is not tight.
4.3 Paint nozzle seating is damaged at the paint nozzle or inside the nozzle set.
5 Jett flutters: Possible causes:
5.1 Product feed is insufficient
5.2 Paint nozzle is not tight
5.3 Paint nozzle seating is damaged at the paint nozzle or inside the nozzle set
The guns can be cleaned in an automatic gun cleaner that cleans the guns properly with the correct solvents. After cleaning, dry the gun and store it for the next use.
Details about paint strainers can be found in this module:
- COLOR AND PAINT PREPARATION - PAINT STRAINERS
Here you will find the different attachments of technical spray gun approvals:
SPRAY GUN APPROVALS
Effective flash off of a waterborne basecoat
Since it is much more difficult for water to evaporate from a waterborne basecoat than for organic solvents to evaporate from a solvent-borne basecoat, we recommend forcing the flash off process of the basecoat with a suitable venturi system.
A temporary increase in the booth temperature can also force the flash-off process and is recommended especially for complete resprays (10 min at 45°C). However, for smaller refinish surfaces, this is often less efficient and practical.
When flash off systems are used, the nozzles are oriented such that the airstream of the system is adapted to the air flow of the booth (pointed slightly downward toward the extraction grids). In addition, the angle of the air stream from the system and the surfaces to be flashed off is approx. 45°. The system works most efficiently in this position.
Orientation of a venturi system toward the surface to be flashed off
1. Some-times with integrated dryer
2. Volume should be designed to match peak consumption
3. The pre-filter, which is rinsed automatically, removes particle sizes in the range of 5 µm. Absolutely necessary for air cleaning (oil/water) at the compressor delivery end.
4. An air dryer works efficiently up to a maximum pipping length of 30 m.
5. Extraction filters in the spraybooth.
Screw-type compressor (the most common type at present):
Output capacity 7 m³/HP (Horsepower) (better than a piston compressor).
According to the manufacturer's instructions, this compressor runs without interruption at 100% capacity and is very well suited for high air consumption scenarios.
Output capacity 6 m³/HP.
Suitable for medium air consumption scenarios.
The air dryer reduces the water vapor content of the air.
It is effective only if the piping length does not exceed 30 m. You should regularly clean the dirt trap before the electric drain valve because if it clogs, the air will re-enter the piping.
In addition, residual water in the compressed air for spraying activities can cause surface defects!
The compressed air flow should be steady, but also technically pure, i.e. free of water vapor, oil and dust, in order to prevent problems with application and paint film durability.
- Screw-type compressor:
According to the manufacturer's instructions, as a rule, you should empty the compressor and replace the air and oil filters after 2,000 hours of duty (at least once per year). The oil separator filter must be replaced after 6,000 hours.
- Piston compressor:
Once a year, you should empty the tank of the compressor, replace the air filter and check the state of the valves.
The prefilter cleans the air delivered by the compressor (removes oil and water).
It must be replaced once a year or more frequently, depending on the state of the compressor.
You should regularly clean the dirt trap before the electric drain valve because if it clogs, the air will re-enter the piping. Monitor the draining function and the dew-point gauge, and keep the radiator free of dust.
Different dryer types:
- Adsorption dryer:
Adsorption is a physical phenomenon: A gas or liquid is bound by a solid, as a result of penetrating its surface. The dew point is -40°C. The residual water vapor content of decompressed air (1 bar) is 0.12 g/m³ at 20°C. This type of dryer is more expensive than a refrigeration dryer. It reduces the moisture content of the air more effectively and is used for products requiring compressed air that contains very little or no residual moisture.
- Refrigeration dryer:
The dew point is 2°C. This means that the air temperature is cooled down to 2°C. The residual moisture content of the air therefore is 5.57 g/m³ at operating pressure (approx. 8 bar).
- In our trade, all working steps serve a single goal: paint application. Therefore, we must do everything to avoid having to do the job all over again, thus losing precious time and material.
- "Daylight" lamps must always be used for lighting in spray booths to ensure a proper visual check of the color.
- The main purpose of the filters is twofold. On the extraction side, they remove paint solids from the air before it goes into the atmosphere and on the intake side, the filters remove dust to prevent dirt inclusions in the paint finish.
- The prefilter cartridges (of compressed air) must be checked regularly and must be replaced when they are dirty.
- All vehicles must be cleaned and degreased before they enter the spray booth.
- We recommend that you also replace the air hoses for the spray guns at regular intervals
- We recommend that you replace the floor filters and ceiling filters as per the supplier’s recommendation. Always make sure that this does not produce negative pressure in the spray booth (please observe national regulations).
Filter checks and changes, for example (shows position):
Pre - fillers Floor fillers
The air is filtered at 0.01 microns to prevent any contamination of the paintwork. Every six months, remove dust from the filter cartridge of the first tube and wash it out with high-quality thinner. Replace the filter cartridge of the second tube.
- The first tube captures dust and removes oil and water. This cleans the dried air to 98% purity.
- The second tube removes the remaining contaminants, resulting in pure, dry air => 0% relative humidity.
Technically pure compressed air used to apply refinish paints must have less than 5% relative humidity in normal air consumption conditions.
The appearance of a paint finish depends not only on the paint materials and how they are processed, but also on the condition of the spraying and drying booths and other equipment. Refinish paints should be applied at an ambient temperature of between 18°C and 25°C (64-77°F).
The air used for spraying must be free of oil and water (check the oil separator daily). The spraying pressure must be constant. Choose the correct nozzle and air caps. The cleanliness of both the nozzles and the air caps are also important as this will have an impact on the spraying pattern. Spraying and drying booths are kept free of dust mainly by means of an efficiently functioning ventilation system, which is also necessary for safety reasons, to avoid any build-ups of explosive mixtures of solvent vapor and air. The result of a repair job depends not only on the spraying technique, but to a greater extent on a proper ventilation system. The volume of air needed in a spray booth is approx. 20,000 m³/hour (700,000 cu.ft/hour). The air used for spraying should not be drawn from the workshop because this would require a higher level of dust filtering. The air drawn in from outside must be filtered and warmed. This applies particularly in the colder seasons and especially in the case of combi booths, i.e. spray booths that also serve as drying booths. The amount of air to be drawn in depends on the size of the spraybooth and is also directly related to the amount of air extracted. From technical perspective, enough air must be drawn in for the pressure in the spray booth to be higher than the pressure outside; a ratio of exhaust air to incoming air of approx. 1 : 1.05 is sufficient.
Negative pressure inside the booth will inevitably lead to defects in fresh finishes because the air coming in from outside around doors and through other openings carries dirt particles that will contaminate fresh paintwork. This is why overpressure in the spraybooth, combined with efficient filters in the ventilation system, play a particularly important role for a flawless finish. The above does not apply in the UK, where pressure in the spray booth is required to be lower than the pressure outside the booth. If there is a drying oven connected to the spraybooth, pressure in the oven must be higher than that in the booth in order to prevent contamination of the objects being dried by overspray from the spray booth, for example. The filters used must of course be adapted to this purpose and kept clean at all times. The fine filters should remove at least 99.8% of the dust contained in the air being filtered. It is particularly important that the incoming air be directed through a suitable system of distributors that can prevent the creation of excessively strong air currents. Such air currents would not only inconvenience the spray painter, but also form vortexes that retain the paint dust longer. This paint dust would then gradually be deposited on the freshly painted surface and spoil it. The air speed should not be too high either, since the paint applied would then dry too quickly on the surface. The result would be poor flow and also the formation of specks due to insufficient overspray absorption. Furthermore, if the surface dries too rapidly, this can lead to loss of gloss and wrinkling. Wherever possible, the incoming air ducts or distributors should be spread over the entire ceiling area. An air speed of 0.3 m/sec (which means that the air is renewed approximately 350 times per hour), measured right across the spray booth, is generally sufficient. The air is best extracted via outlet ducts down near the floor of the spray booth (separation by means of filtering).
Employee safety and operating regulations Finally, it should be noted that installations of this kind must be designed, set up and operated in accordance with the applicable rules on the prevention of accidents, i.e. in Germany in accordance with BGV D24 and D25. The storage of paints, solvents and thinners is subject to the regulations concerning flammable liquids. Applicable MAC values (maximum allowable concentrations of substances that are hazardous to health) must be observed in all work areas. Noise pollution from the equipment used can be avoided if all machines and tools comply with the maximum levels laid down in the accident prevention regulations concerning noise (in Germany, BGV B3).
Remark: All national and/or locally applicable working directions, operating instructions and safety regulations as well as existing rules for the prevention of accidents and regulations on dangerous substances must be observed.
Details about oven, infrared and UV drying can be found in this module:
- DRYING PROCESSES / SYSTEMS - BAKING / OVEN, INFRARED & UV DRYING
UV LAMP TYPES AND APPROVAL
Here you will find an OVERVIEW OF UV LAMPS.
Details about mixing machines and mixing lids can be found in this module:
- COLOR AND PAINT PREPARATION - MIXING SHELF
A wide range of sanding machines for sanding different car panels and substrates are available on the market.
A sanding machine is a power tool (air- or electric-powered) with attached sanding paper to smooth or shape surfaces. Different machines sizes and shapes are available for different purposes: flat, rotating, eccentric rotating, orbital, and random orbital. These machines are directly or indirectly driven, mostly vibrating in a straight line or in an orbital path and can be used with a hard, medium, soft or interface pad to produce different pressures on the surface.
This influences the depth of the sanding scratches and pattern. Many machines are equipped with dust extraction. Dust extraction removes the sanding residues between the sanding paper and the surface. When using dust extraction be sure that the sanding paper holes fits to the sanding pad holes. This gives you the best extraction which leads to a safer environment, clean workplace and a longer working time of the sanding paper.
These hand-held machines with replaceable sanding paper are moved over the substrate and rapidly produce a fine, smooth finish.
The machines have different hub sizes, which are specified on the machine.
The bigger the number, the bigger the hub, and the coarser the finish result.
The sanding finish that will be achieved in the different production stages depends on the choice of the optimal combination of machine type, sanding paper, hub and pad.
- 3-5 mm hub sizes:
for universal sanding (body filler, filler, topcoats), ensures uniform roughness
and reduces the risk of visible sanding marks in the topcoat
- 7 mm hub sizes:
only for body filler (high working speed, higher risk of sanding marks on softer and solvent-sensitive paint layers)
Details about sanding paper can be found in this module:
BASIC KNOWLEDGE - PREPARATION - SANDING
Details about masking foil or paper can be found in this module:
BASIC KNOWLEDGE - PREPARATION - CLEANING & MASKING