Particles sphericity & sieving in metal powder industry – Virto-Cuccolini

For the purpose of industrial screening, particle shape does make a great difference in terms of efficiency. Let’s discuss this well-known issue with Asad Bilal, our expert in metal powders screening:

 

Q: Why is particle shape such a key factor within metal powders screening:

A: Irregular shaped particles represent a major hurdle within powder sieving. In facts, they tend to wedge into the mesh aperture, indipendently of their main dimensions. In some other cases, very fine particles accompanied by dust may tend to coat the mesh due to electrostatic forces or due to the product itself, tending to agglomerate.

Particles with irregular shape tend to wedge within the sieve mesh aperture

Fine powder particles coating the mesh

In the context of metal powders sieving, particles morphology directly impact on the final product’s features, such as its near net shape, its porosity degree, its flowability and finally on the properties of the alloy and its behaviour during its application.

It is for sure important for metal powders producers to have perfect control on the particle shape of their products in order to ensure accuracy and predictability of final product quality in HIP, MIM, EBM or SLM process.

Q. And what happens if particle shape is spherical?

A. Following recent improvements within atomisation technology, we experienced that the sieving – as well as the blending – phase is encountering difficulties due to the spherical shape of particles.

Innovation in atomising technology creates spherical particles, difficult to sieve and blend

The difference between a fine wire mesh and a thicker wire mesh within the context of sieving.

Another issue can come from the type of mesh installed in the sieve. The mesh wire size in facts can have some influence on the possibility for each particle to pass or not the mesh aperture, hence on the flowrate, since it has an impact on the total open surface area. On the other hand, meshes are now manufactured with far more accuracy than in the past, which means that sieving efficiency is also more directly connected than earlier to the required cut point.

Q: Which solutions do you recommend for obtaining maximum sieving accuracy?

A: At Virto-Cuccolini, we have a long experience in powder sieving. We do apply different sieving technologies based on Customer’s requirements in order to offer the widest possible range of solutions for their sieving needs: traditional vibrating sieving, ultrasonic sieving and multi-frequency sieving. Based on the hundreds of tests carried out on behalf of global metal powder producers in the recent years, we can confirm that the best combination of quality parameters was given by our patented Multi-Frequency X-Line Technology, also in case of spherical particles. Ultrasonic sieving – with expansion and contraction of the mesh in order to facilitate particles flow – is not able to guarantee sieving accuracy within a field of application – metal powders – where fine size is a must now. Moreover, this method is slowing down the sieving process and makes it in the end less productive than needed. We at Virto-Cuccolini, based on our accumulated know-how, investigate Customer’s specific application and context each time to check each key parameter, such as: core principle of mechanical sieving, selected mesh and its properties, particle size distribution (PSD) of Customer’s product, its bulk density, the impact of gravitational force on the product, the coefficient of friction between mesh and powder, the effect of vibrational forces produced by our sieving equipment.

It is with almost two decades of dedicated study and research, that we came  to the solution – which we proudly confirm even now – of X-Line Multifrequency-Technology sieving equipment. Each one of the typical sieving issues, including sphericity of the powder, was tested and overcome through our multi-frequency sieves, in the range from 10 to 350 µm. We are glad to invite our Customers to carry out sieving tests and compare X-Line performance with that of their current sieve, to find out how easy the sieving process can be. 

VIRTO changes the screening game.

YOU CAN RECEIVE OUR FREE ADVICE TO SELECT THE TYPE OF SIEVE MORE SUITABLE TO YOUR PROCESSING NEEDS, BY CONTACTING US




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