“Puffing” and “surging” are the labels some manufacturers use to describe how powder material can form large compacted groups of particles (and clog up feed lines). Avoiding this clogging is key to maximum transfer efficiency, so it is more than helpful for manufacturers in the powder coatings industry to understand how to avoid such “puffing” and “surging.”
Powder Coatings Online (PCO) specifically references “a lack of screening” as the most common reason that powders puff and surge. Powder handlers in the coatings industry are incentivized to reuse the paint that falls to the floor of the spray booth, but that powder must be clean before it “goes back to the guns” to be sprayed onto surfaces again.
The most effective way for such paint to be reused cleanly is for it to be put through a screener uniquely prepared for the task. Unless you want to deal with discovering post-production that you have expensive scrap material on your hands, dirt and particulate matter must be removed before it can build up in the reclaim system. Centrifugal screeners actually pose a particular advantage over other screening machines for accomplishing this purpose.
In this AZO blog post, we’ll explain exactly how these types of screeners minimize “puffing” and “surging” to a greater degree than other screener types. We’ll also share a helpful tip to greatly reduce coating defects when utilizing screeners in general. Below we’ll explain how a centrifugal screener poses a significant advantage over other styles of powder coating screeners.
Centrifugal force shakes material through a screen
With screeners, it is generally recommended that an 80-mesh screen is utilized. This is because powder particles tend to be 35 to 45 microns in size (though some can reach 100). When higher-mesh screens are used, these powder particles tend to avoid passing through the screen. This ultimately leads to wasted powder and even more scrap product (an expensive pain-point for many manufacturers). Still, centrifugal screeners contain beater bars that help these particles get to where they need to be.
When powder is pushed through the screen by a centrifugal screener, it causes the screen to vibrate. Essentially, the three beater bars in a centrifugal screener rotate fast enough (at so many times per minute) that powder paint particulates hit the screen with great force and pass through it. The screen flexes up and down continuously, and undesirable material is kept from continuing down the path that only powder paint travels.
It’s this sheer force that beater bars and the very nature of centrifugal force that ensures that the screen itself does not become clogged in the same way that non-centrifugal screeners allow. Deck screeners, for example, may contain mechanical vibrators to assist that which is on top of the screener fall through it, but such a device does not contain the three entire beater bars to push such material through a screen forcefully. It is by nature of these bars and the centrifugal force they take part in that makes a centrifugal screener the perfect tool for the powder paint manufacturer.
Maintaining your screener reduces defects in material
Coating defects are often caused by undesirable material (aka trash) remaining in the paint particulates after said particulates are salvaged. The best way to ensure that powder paint defects do not occur is to ensure that the screener itself stays in peak condition. Checking your screens often and determining if any of the screener’s gaskets have failed are two actions that help keep paint powder particulates clean through the end of the process.
Some particularly effective ways to maintain a screener’s optimal performance that we’ve covered in an issue Powder & Bulk Engineering include:
- Establishing a company culture around maintenance and safety
- Establishing a routine maintenance schedule for your screener
- Working with suppliers to determine realistic mesh sizes (based on throughput)
Following these points will help mitigate the risk of screen failure, and a screener whose screens are in tip-top shape will continue to filter out undesirable material from the powder paint particulates to be used as reclaim material. Once a powder is baked onto a surface, that surface is bound to those attached powder paint particulates. The cost of labor to remove them generally outweighs the cost of a new part with a new surface altogether. In order to avoid scrap and continue to release a quality product on the market, centrifugal screeners aid the powder paints industry like no other method of screening.
As the founder of AZO was the inventor of the first cyclone screener on the market, we’ve had experience in this industry since 1949. Clients often come back to us with special requests and our sifting equipment has a high-quality robust design. If you have any questions about cyclone screening equipment or ingredient automation as a whole, please contact our sales team. Our screening buying guide can also help you specify, justify or maintain the right screener for your operation.