Expert Dialogue | After 15 Years in Mixing Technology, What Does He Most Fear Clients Overlook?

An Exclusive Interview with Yang Jiuyong, Planetary Equipment Expert at the Ross Equipment Technology Center

At the Ross Equipment Technology Center, Yang Jiuyong’s workstation is piled with drawings. Over the past fifteen years, his name has appeared repeatedly in the inventor column of a series of patents, including dual planetary mixing and dispersing machines, fixed-point stop devices for planetary agitators, and multi-axis planetary mixers. As an expert in the planetary equipment design group, he knows better than most: whether a piece of mixing equipment works well often does not depend on which parameters the client checks on the selection form, but on the things that were never written into the requirements list at all.

“What I fear most is that clients overlook one thing—they take a process that mixes well in the lab and directly use it as the basis for requirements after scale-up,” Yang Jiuyong said calmly, but a kind of helplessness repeatedly verified by experience could be heard in his voice. In mixing technology, success in small-scale trials followed by failure after scale-up is almost a commonplace trap. A 5-liter unit in the lab runs beautifully, but after scale-up to 500 liters or even 2,000 liters, the flow path of the material inside the vessel changes completely, the locations of dead zones differ, and the shear rate distribution is worlds apart.

“Clients often think that once the equipment is scaled up, they just need to adjust the speed proportionally. Far from it.” He gave a very specific example: a small unit performs well at a filling rate of 63%; in a pilot test it is adjusted to 74%, only 11 percentage points higher, yet the mixing effect may drop by a grade. Even more hidden is the discharge stage—a small unit discharges quickly, and the material is out before it has time to stratify; a large unit’s discharge time is longer, coarse particles roll to the sides, fine powder remains in the middle, and a batch of material completes “secondary separation” during discharge. Sampling may then happen to catch the “good” part, and the unevenness of the whole batch is masked.

In recent years, much of the work Yang Jiuyong and his team have done on the design side has essentially been a struggle against these “invisible deviations.” The fixed-point stop device for planetary agitators solves the problem of inconsistent stopping positions of the agitator each time, which causes batch-to-batch drift in the initial state; improvements to the mixing seal structure prevent slurry from quietly seeping into the bearing cavity and causing seizure—such failures often accumulate without the client noticing, and by the time the machine stops, it is already too late; the multi-axis planetary mixer uses container rotation instead of gearbox-driven revolution, which reduces the overall machine cost while also making the relative motion between the blades and the material more controllable.

“What the equipment can do is minimize dead zones, make the shear distribution more uniform, and smooth the discharge path. But the premise is that the client must tell us the true rheological behavior of the material and the true boundaries of the filling rate,” Yang Jiuyong said. The Ross Wuxi laboratory supports a large amount of simulation and data analysis precisely to verify, before the equipment is implemented, those variables in the scale-up process that are easily skipped.

After fifteen years of deep cultivation, Yang Jiuyong has always believed that the essence of mixing technology lies in the details. A stable and reliable planetary machine is not a pile of parameters, but a design that incorporates, in advance, those easily overlooked operating conditions, scale-up risks, and long-term production requirements. For him, every design is about blocking mass-production risks before production starts for the client.