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Why Grind and Classify Powder Coatings In-House

Why Grind and Classify Powder Coatings In-House
24 May 2021  |
A company developed a new product line for a specific customer. During the development phase, they discovered its powder coating equipment allowed oversized particles through the machinery, causing blemishes in the final product’s finish. The problem threatened an important opportunity, so they contacted Prater to help them resolve the screening issue.

An inspection showed that these oversized particles slipped through worn parts in the screening process, so Prater suggested adding gaskets as an immediate remedy. To preempt further issues, Prater engineers then modified the design to improve the company’s centrifugal sifters. This custom modification satisfied the customer’s needs, improved performance, and delivered a long-term solution regarding their powder coatings.

Had this process not been conducted by the company itself, this problem probably wouldn’t have been caught as soon, resulting in higher production costs. When arguments for outsourcing and offshoring such manufacturing processes are made, manufacturers should consider reasons for keeping these capabilities in-house.

Industries that Use Powder Coating Equipment

Used to color steel, aluminum, and other metals, powder coating offers a longer-lasting and tougher finish on metal products than painting. Besides adding to its durability, a quality finish also helps sell the product.

Items and industries that use powder coating processes include:
  • Appliances such as electric and gas ranges, refrigerators, washing machines, dryers, freezers, water heaters, dishwashers, microwave ovens, and vacuum cleaners.
  • Architectural components including facades, aluminum doors, windows, shutters, bathroom fixtures, mailboxes, ornamental fencing, metal guttering, guard rails, structural steel, and signage.
  • Electrical equipment such as housings for motors, transformers, junction boxes, connectors, lighting fixtures, computers, and telecommunications equipment.
  • For pipelines, gas pumps, piping, and valves used by the oil and gas industry.
  • Grain storage systems, tractors, trailers, plows, cranes, earth-moving equipment, and forklifts for agriculture and construction.
  • HVAC industry, such as heating devices and systems, air conditioners, and ventilation ducts.
  • Lawn and garden equipment, such as lawnmowers, snowblowers, leaf blowers, grills for barbecuing, chainsaws, garden tools, wheelbarrows, shovels, and patio furniture.
  • Medical devices and equipment, such as wheelchairs or surgical instruments.
  • Recreational equipment, such as golf clubs and carts, playground and exercise equipment, ski poles, and metal toys.
  • Safety equipment such as fire extinguishers.
  • Water transmission pipelines.
  • Wheels, bumpers, window trimming, door handles, windshield wipers, steering wheels, radiators, suspension systems, air and oil filters, motorcycles and mopeds, valve covers, braking systems, brackets for mirrors, ashtrays, luggage racks, frames for truck seats, and chassis for the transportation and motor vehicle industry.

Many other products also use powder coatings to increase longevity and durability, including fire hydrants, metal fans, toolboxes, desk accessories, and satellite dishes.

Making Quality Powder Coatings In-House

While outsourcing any manufacturing work has been touted as a way to reduce costs, this is not always the case. There are several things companies should carefully consider before outsourcing production. Weighing all these factors ensures businesses make the best decisions regarding product assembly.


Keeping manufacturing processes in-house allows companies the agility to change their products more easily. Implementing last-minute changes on outsourced work can be time-consuming and expensive. It may even require adjustments to or replacement of powder coating and powder grinding equipment.


In-house production allows companies to control quality better, a major problem when manufacturing equipment is located off-site. Many factors influence the quality of powder coatings, though highly efficient classification ensures particles don’t come out too coarse, which negatively influences the quality of powder-coated surfaces. By working in-house, it’s much easier to track production during the classification process.

Control of Production

Going hand in hand with quality, in-house manufacturing guarantees companies have complete control overproduction. It allows quality managers to directly supervise powder grinding equipment to ensure it produces narrow particle size distribution with well-defined top cuts while limiting the number of fine particulates. Manufacturers can also quickly increase or decrease production, better anticipating demand.


Transport costs money, so producing products on-site can negate the transportation costs from the outsourcer. It also means any raw materials used in manufacturing the product require transportation as well. Before outsourcing, consider the time and cost of transportation to both markets and from the raw materials necessary for production. Offshoring can increase costs further through import taxes, which may negate any lower production costs used factored into this decision.

Public Relations

Moving production to an international location can lead to a public relation nightmare, particularly if offshoring to a place where environmental and labor legislation is lax or labor costs are significantly lower. Manufacturers should consider foreign outsourcing very carefully before committing to it, as it may unintentionally lead to lower sales, as many customers view foreign outsourcing negatively due to the perception that it leads to local job losses. This could additionally result in political investigations that can further hinder the business. Avoiding foreign entanglements with production can result in lower profits, so it’s a good idea when outsourcing production to do so as locally as possible.

Classifying & Grinding Equipment for Powder Coating

As industry necessitates high productivity levels, highly efficient processes are necessary for powder coating equipment, whether for large-scale production or small production runs. One widely used piece of powder coating equipment is the air classifier mill. The air classifier mill offers an excellent means of controlling the top end of particle distribution, a trait desirable for achieving a uniform powder coat finish. To make it even better, research was conducted to determine ways of reducing the number of fine particles as well. They experimented with the pitch, or spacing of the grinder blades as well as the impact speed, both of which had a profound effect on the particle size distribution.

Powder Grinding Equipment Systems

Grinding systems primarily operate by impact milling extruded powder coating chips inside an air classifying mill. A rotary airlock dispenses the chips from a storage hopper into the powder grinding equipment. The air classifying mill then grinds the powder with gentle impact, classifies, and separates the particles by size.

In the air classifying mill, grinding blades impact and accelerate particles outward. Additional collisions take place against a specially designed, screenless grinding frame until small enough to pass through a gap in the frame. Partially ground particles are circulated outside the grinding chamber, where a secondary intake drafts pneumatic air to help fluidize and cool the particles. The particles are pulled inward toward the classifying rotor, where size separation takes place. On-size particles pass through the rotor and are pneumatically conveyed to a dust collector while off-spec particles are recirculated back into the grinding chamber for additional size reduction. The air classifier rotor is independently controlled, allowing for precise control of particle size simply by adjusting the RPM.

Product leaving the air classifying mill is pneumatically transported to a dust collector that separates the product from air. A fan on the clean side of the dust collector provides the pneumatic air for the system.

Powder Grinding for Small Batches

Most large-scale powder grinding systems can process well over a thousand pounds per hour, making smaller-scale production problematic, as it wastes capacity. Reducing particle size distribution on smaller scales is also more difficult to achieve, so more compact powder grinding equipment has been developed. These smaller systems allow companies to produce small quantities for samples and smaller orders quickly.

Prater Coating & Grinding Equipment

Powder coating equipment and systems can be used for a wide variety of applications. Prater Industries recognizes this, which is why we make equipment that can be readily adapted across many manufacturing sectors.

Along with offering powder grinding equipment, we also provide machinery that supports full production systems. Our in-house process controls team’s knowledge, and expertise ensures that your project will be done punctually, cost-effectively, and with precision. Additionally, we can assist your operations with complete project management services, from layout design to scheduling charts, to meet all your production requirements as well as installation and supervision of mechanical and electrical systems and equipment.

Prater’s testing and tolling facility are among the largest in North America. Rather than estimating parameters, we can test run your product, supporting system calculations to identify what’s necessary to operate your systems correctly. With nearly a century in business and constant advancement of our technology, Prater’s equipment can be customized to meet all your powder processing applications.

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Prater Industries, Inc. offers a wide range of equipment for particle size reduction, enlargement, feeding and separation such as hammermills, fine grinders, lump breakers, classifiers, rotary airlocks and valves, briquettors/compactors and more. All Prater equipment,...

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