Rotary Batch Mixers Blending Without Segregation: Meeting the Demand of the Powder Industries

Rotary batch mixer enables an addition to capacity — Blending plays a key role in producing metal powders. The requirements of a Japanese metal powder manufacturer are therefore pretty high. The company demands good blending, complete discharge without segregation and short mixing times even with large capacity.

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Nippon Atomized Metal Powders Corporation uses a patented water-jet atomisation process to make high-quality super-fine metal powders from copper, bronze, brass, silver, gold, and stainless steel that are of consistent composition and particle size. Following the water atomisation stage, the resulting metal powders are dried, screened and blended. Each step must be carried out correctly to yield the correct particle size distribution for the planned end-use including electronic components and assemblies.

Avoiding Segregation

The Munson Rotary Batch Mixer plays a key role in producing metal powders having particle sizes from 10 micron up to 500 micron (30 mesh) and specific gravities in the range 1.8–3.5. The mixer’s volume is 2.5 m², and typical batch sizes are 4,000–5,000 kg.

“We use the mixer mainly as a homogeniser to avoid material segregation,” says Koji Yamamoto. He is General Manager of the R&D division of Nippon Atomized and heads one of the firm’s two production divisions. “We need to be sure that particle size distribution is the same across the batch, and from one batch to the next. With the Munson, we get good blending and complete discharge without segregation, and short mixing time, even with the large capacity.”

Nippon Atomized purchased the mixer to increase capacity. “Our previous double-cone blender was limited to 1,500 kg per charge,” Mr. Yamamoto says, “and a batch took 20 minutes to blend. This was too small and too slow for our production needs. The rotary batch mixer blends up to 5,000 kg in just 5–7 minutes.”

The unit's four-way mixing action — tumble, turn, cut and fold — achieves batch uniformity rapidly, and more gently than with agitated blenders. Continuous rotation keeps material in motion at all times, preventing particle-size segregation during discharge.

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