Coating Factory
Coatings are formulated for specific applications. PPG’s coatings for consumer electronics are trusted by original equipment manufacturers to withstand the demands of use and extreme environments.
Manufacturers may choose to complete powder coating operations in-house or outsource them to job shops and finishing service contractors. The latter can be cost-effective options for prototype and short production runs.
Pretreatment
The pretreatment process is a vital step in the powder coating process that sets up a substrate for superior bonding. It’s the foundation for a high-quality finish that’s durable and resists corrosion. The pretreatment process can include chemical etching, phosphating or even Zirconium for maximum durability. The type of pretreatment used depends on the type of metal, its end-use and environmental constraints.
The first step of a good pretreatment process is cleaning the surface thoroughly. This is often done using a spray cleaner that contains chemical agents. It can also be accomplished through shot blasting where the parts are blasted with a mix of sand, shells and “shot” that removes any dirt or other contamination on the surface.
After the cleaning process is complete, a phosphate treatment is often used to help improve the adhesion and prevent corrosion of the powder coating. This is usually done with iron phosphate, zinc phosphate or a specialized non-chrome phosphate process.
Henkel’s Ecoat technology provides the auto industry with a pretreatment process that helps reduce corrosion and allow for a stronger finish. This helps the industry meet strict environmental regulations around fuel efficiency and safety. Additionally, it supports the shift toward lighter materials in vehicles.
This phosphate process textures the surface of the metal to create microscopic pits to which powder paint adheres more securely. It also increases corrosion resistance, a necessity to protect the metal from rust and other harmful chemicals.
In order for the phosphate to be effective it must be followed by a rinse stage and then a conversion coating. This is generally done with a zinc, iron or trivalent chromium phosphate, though other alternatives are possible.
It is important to understand that pretreatment is a multi-step process, and not something that can be sped up or cut short without negatively impacting the quality of the finished product. As such, it is important to consider all the variables and find the right solution for each individual application. A good pretreatment process will be one that is tailored to the specific coating you are working with, as well as your local environment and the demands of your customers.
Spray Booth
The spray booth is a ventilated work area designed to contain the application of surface coatings to a work piece. Typical spray booth designs provide a work chamber that is airtight and sealed to the rest of the facility, with an exhaust stack for venting to the atmosphere. Some systems also include a regenerative thermal oxidizer (RTO) to control volatile organic compound emissions and meet air quality standards for environmental compliance.
There are many types of spray booths available to suit the unique requirements of different industrial product manufacturers. For example, a woodworking manufacturer will need a booth that can be opened or closed to accommodate part sizes and shapes. Large metal fabrication companies often use a dip-spin system, where an entire assembly is dipped in liquid paint or coating media. The spinning action removes excess coating and then the parts are placed on a conveyor belt for curing.
Most spray booths are built from non-combustible materials to limit flammable vapors and smoke. This is important because spraying flammable liquids can quickly cause fire and explosion hazards. In addition, the design and construction of spray booths should comply with NFPA (National Fire Protection Association) standards and codes to ensure that workers are protected from exposure to harmful substances during the spraying process.
Whether you are using an automatic or manual powder spray booth, it’s vital to have a well-designed and properly maintained system. This helps ensure that the powder coating system produces a high-quality finish, and that you can avoid costly downtime. The type of powder used will have a significant impact on how well your system performs.
To maintain the highest level of performance, your manual or automated spray booth should be equipped with several different monitoring devices. These can help you identify problems before they become serious. A simple manometer can be added to the booth to indicate when the intake filters need replacing, while a photohelic or magnehelic sensor can detect the presence of vapors in the air.
Some manual powder coating spray booths have a collector module that rolls out (folds out like a book) for easy color change and can be upgraded to support multiple colors. This allows the operator to roll out a new cartridge and continue production without having to stop and clean the gun. This also eliminates the need for a large dust collector duct and helps to save on energy costs.
Electrostatic Gun
The electrostatic gun process uses an electrostatic atomizer to charge the coating powder as it is being sprayed toward a grounded workpiece. This allows the powder to be attracted to the object instead of the gun and can significantly reduce application times. This process is also particularly well suited to tubular products because it is more likely to wrap the paint around them rather than spraying in front of them like conventional spray guns would.
The gun can be charged with either voltage, called Corona Charging or through frictional contact with the inside of the gun barrel, called Tribo Charging. The atomised coating powder is then blown through the gun with compressed air and an electrostatic field is created between the gun tip and the object to be coated. The negative ions that are freed from the powder as they are sprayed search for the closest grounded object to be attracted to, and once found are deposited onto the workpiece.
This is a highly efficient and reliable method of spraying, with a high transfer efficiency of up to 95%. There is less overspray, which keeps the spray booth cleaner and reduces maintenance costs. The paint is also more evenly applied to the workpiece, which increases production efficiency.
When choosing the right spray equipment it is important to consider the resistance of the coating material, which is measured in megohms per centimetre. If the paint is not formulated specifically for electrostatic use, it may not have the correct resistivity and will not perform to the highest standards.
Another consideration is the speed at which the gun can be operated. The ideal speed is 4.5 to 5.5 m/min, as higher speeds can lead to uneven coverage or even break the powder apart. The final consideration is the safety of the operator, which is ensured by a full range of protection outfits and eye and ear protectors.
The advantages of using an electrostatic gun are clear: more paint ends up where it is supposed to be, with less being lost to overspray, and the finish is much smoother. Additionally, it is more environmentally friendly than a liquid coating because VOC (Volatile Organic Compound) emissions are lower.
Curing Oven
The curing oven is the last step in the coating process. It heats the product and the coating to a predetermined temperature and then keeps it at that temperature for a certain period of time. This step is critical for ensuring that the product is properly cured and protected. If the curing process is not done correctly, the final product may look fine but it will likely fail to perform as intended.
There are many different types of curing ovens. They can be batch ovens or continuous process ovens and they can be powered by natural gas or electricity. Some are also designed to use UV curing technology to accelerate the desired chemical reaction. A good composite curing oven should have a digital temperature controller that makes it easier to set, engage and maintain a heating profile. Other important features include fast ramping and cooling rates, a robust safety system, and the ability to meet AMS2750, BAC5621 and NADCAP standards.
One of the most common uses for curing ovens is to cure adhesives. Some adhesives are cured at room temperature, but others need to be heated in order to achieve the desired bond strength. A good curing oven should be able to handle a wide range of applications and temperatures.
When choosing a curing oven, it’s important to consider the manufacturer’s experience and expertise in the industry. They should be able to provide detailed information about the specific product they’re selling. They should also be able to offer advice on the best solutions for your application. It’s also important to check whether the manufacturer offers factory acceptance testing or after-sale service.
The oven’s airflow pattern is another important consideration. The airflow needs to be effective in distributing heat throughout the entire oven. This is especially important if the product is large and has a lot of surface area.
When selecting a curing oven, it’s also important to make sure the manufacturer is UL and CSA certified. This will help you avoid purchasing a substandard machine that could put your employees at risk. It’s also a good idea to choose a supplier that can design and implement the electrical systems and PLC programming in-house. This will ensure that the supplier has the resources necessary to support and troubleshoot any issues that may arise during installation and operation.