Many industries rely on skilled contract manufacturers to supply blended powders that are key ingredients in the products they produce. Whether small 55-gal drum batches once a year or several thousand metric tons multiple times a year, contract manufacturers serve as a critical extension of manufacturing capabilities.
When this is required, contract powder manufacturers are often called upon to resolve difficult development or production issues through a consultative process. This can involve achieving specialized powder characteristics to improve both the manufacturing process and the end product.
For consumer products like cosmetics, improving powder characteristics can prolong waterproofing. For industrial products that involve 3D printing with metal powders, improving powder characteristics can enhance powder flowability and end product quality.
Whatever the industry or goal, however, achieving it usually requires a unique combination of sophisticated, precise blending and drying equipment as well as a deep expertise and knowledge of powder types, sizes, and interactions.
“To achieve the desired end result, you need to understand the characteristics and properties of the raw powders and materials, and how they will interact when blended,” said George Paffendorf, director of operations at Advanced Powder Solutions (APS). “This can include powder size, density, lubricity, and moisture content, among other factors.”
Specialized Blending/Drying for Cosmetics
Of particular importance to cosmetics and personal care product manufacturers, said Paffendorf, is working with an expert contract manufacturer can also help to more effectively and cost-efficiently achieve superior hydrophobic (waterproof) and other material properties, along with better distribution of active ingredients.
Having specialized equipment available is also critical to effectively blend powder and enrobe it in a hydrophobic coating. While hydrophobic materials are not new in the cosmetics and personal care industry, optimizing the process is important to create high-performance, powder-based products ranging from makeup and mascara to sunblock.
Unfortunately, traditional equipment such as plow, ribbon, and paddle mixers, which use blades or paddles to push material, often are limited to moving the material within the confines of their active area. The mechanics force the material bed outward, leaving dead spots inside the vessel where material moves more slowly or remains stationary.
“When the only particles that move are in front of the spinning blades, only some particles will be coated and others not – which will result in product fallout and failure,” said Paffendorf.
According to Paffendorf, this challenge can often be resolved by utilizing either liquid enrobing or powder enrobing, along with special tumble blending equipment.
“We do a lot of liquid enrobing to create a hydrophobic powder for waterproof makeup and sunscreen,” said Paffendorf. “We might use a solvent carrier to enrobe the powder, which essentially puts a waterproof shell around it.”
For such contract manufacturing, APS has end-to-end equipment capable of delivering product in quantities from 2 to 4000 kilos per batch. The contract manufacturer is the in-house testing/engineering arm of GEMCO, a leading manufacturer of tumble blending and vacuum tumble drying equipment.
In contrast to traditional mixing, GEMCO tumble blenders apply even turbulence in all corners of the mix through a combination of macro and micro blending that produces a better distribution of active ingredients.
Macro blending is achieved by rotating the shaped vessel, allowing the material bed to fall away from the vessel’s walls. The blender moves at a precise speed, with the vessel wall at a precise angle, so that the material cascades over itself. There is no additional force from paddles, plows, or spiral ribbons – just gravity.
While this occurs, micro mixing (if needed) simultaneously proceeds via agitator blades located in the mixing zone center of the vessel, where fine processing in the material transpires. Together, the macro and micro mixing evenly expose each particle to six times more active blending per revolution than traditional mixers.
“To manufacture cosmetic products, we utilize a tumble blender with an agitator to basically fluidize the entire bed,” said Paffendorf. “We can atomize the coating solution to achieve a perfectly even distribution or enrobing of the powder particle, whether it is zinc oxide or titanium dioxide.”
3D Printing Industry Powder Optimization
Refining powder characteristics can be essential in many industries, but it is particularly critical in the global 3D printing metals market, which is expected to reach $3.05 billion by 2025, according to a recent report by Grand View Research Inc.
However, to take full advantage of this growth and efficiently produce high-quality parts, powder producers, 3D printer manufacturers and others will need to ensure the consistent, repeatable quality of the metal powders used in the process.
3D printing applications range from aerospace, defense, and automotive to medical and jewelry. The metals involved can include aluminum, titanium, stainless steel, cobalt-chrome, copper, or nickel alloys, and precious metals such as gold, silver, platinum, or palladium.
In the 3D printing process, parts are created from digital specifications by laying down successive layers of metal powder and using a laser to fuse the particles until the part is complete. Like ink-based printers, 3D printing has its own consumables – in this case, metal powder in extremely fine, sub-micron sizes.
Although there are a wide range of metal powder suppliers, the industry is turning to contract powder processors for sophisticated heat treatments that improve the quality of the powder. As 3D printing techniques and equipment continue to advance, optimizing the powders with such heat treatments can improve powder flowability to prevent clogging, speed the process, and produce a higher-quality part.
Most metal powders used in 3D printing, such as iron, nickel, cobalt, aluminum, and titanium alloys, are produced by gas atomization. In this process, a feedstock is melted in a crucible before it is ejected from a nozzle into a high-pressure gas stream. This breaks the molten metal into fine particles, typically under 50-150 microns in size.
While the metal powders produced by this process are typically spherically shaped, it is also important to address the porosity of the surface of the powder particles to improve “flowability.” Otherwise, the powder can clog or slow during the process, affecting the speed and quality of printing.
“For reliable 3D printing production, the powder must flow continuously and smoothly,” explained Paffendorf. “However, uniform powder flow can be inhibited if the particles are rough or porous, which creates more friction.”
The attractive force between tiny, sub-micron size particles also increases as the particles become smaller. So, finer powders are typically less free flowing anyway, according to Paffendorf.
From a quality standpoint, metal particle porosity can also reduce the load bearing, fracture toughness, and fatigue properties of the finished part. Under cyclic stress conditions, it can also lead to cracks and part failure.
To eliminate porosity and enhance flowability, Paffendorf says a growing number of proactive powder suppliers as well as 3D printer manufacturers are adding a heat treatment step in the manufacturing process that involves tumble dryers to achieve a more consistent, high-quality product.
As an example, APS utilizes advanced vacuum tumble dryers that provides sparging (gas injection) in addition to heat application. With this approach, a perforated tube is positioned under the bed of material and distributes a flow of inert gas such as nitrogen. This helps to circulate heat evenly amid the powder.
“A raw metal powder may have a porous, craggy outer surface,” said Paffendorf. “When we heat treat it in the tumble dryer, it closes up the pores so the particle is more spherical and flows more smoothly.”
The gas purge also provides a solution to protecting oxygen-sensitive or volatile powders, which can otherwise compromise certain alloy chemistries. When a blanket of inert gas is used to cover the material bed, it provides a protective barrier that prevents the powder from being exposed to atmospheric oxygen.
Regardless of the blending or drying required, in bulk powder industries like cosmetics and 3D printing, product manufacturers that lack expertise or specialized equipment can benefit from outsourcing challenging powder blends to skilled contract manufacturers that can assist with development, then scale up to full production.
For more information on GEMCO, call 800-654-3626 or visit okgemco.com.