ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2026 24 not only move more slowly, it also spreads less evenly. This kind of layer-to-layer variation is what later shows up as porosity or dimensional error in the finished part. Particle shape had a similar effect. Spreading spherical particles with the same blade-type recoater gave an average film thickness of 38.3 µm, with a standard deviation of 2.58 µm. Angular particles gave a close average, 36.7 µm, but the standard deviation rose to 4.69 µm (Fig. 1). The extra scatter comes from friction: Angular particles catch on each other as they move, and that friction is what makes the layer less even, not a change in the average amount of powder laid down. Blade speed mattered too. At 50 mm/s, the recoater produced the same 38.3 ± 2.58 µm layer. At 100 mm/s, the average thickness dropped a little, to 36.9 µm, and the standard deviation rose to 4.31 µm (Fig. 2). A faster blade does not just move the powder faster—it also leaves a slightly thinner, less even layer. Unlike particle shape or surface energy, which are set by the feedstock, blade speed is a parameter a manufacturer can adjust directly on the machine. APPLICATION EXAMPLE 2: DESIGNING A FLOW-BASED BIOFILM REACTOR Biofilms form on material surfaces without exception, so in a sense, a biofilm is a kind of material-surface degradation. But historically, materials scientists and engineers have not looked at this problem enough from their own point of view, and this could be one important reason why research and development in this area, and the between particles and less free flow in a powder bed. This is the same result observed in the biofilm example below, where higher surface energy also means stronger initial bacterial attachment on a coupon. The team then moved to a geo- metry closer to the real process: powder spreading with a blade-type recoater, the part used in most powder-bed- fusion AM systems to lay down each layer. Here the surface-energy effect showed up not only in speed but in uniformity. The low surface-energy powder gave an average spread-film thickness of 38.3 µm, with a standard deviation of 2.58 µm—tight and consistent. The high surface-energy powder gave a slightly thinner average of 36.4 µm, but the standard deviation was 4.62 µm, almost double the scatter. Thus, the more cohesive powder does same particle idea to granular solids— gravel, sand, snow, and, in this case, metal and ceramic powders. The two platforms couple directly, allowing the operator to follow one powder through the free-flowing stage of a hopper discharge and the dense, packed stage of a spread layer, all in one simulation, instead of connecting separate solvers. APPLICATION EXAMPLE 1: POWDER BED FUSION The first example began with a basic check: comparing powders of high and low surface energy as they flowed from a hopper. The result was clear. The low surface-energy powder flowed at 13.9 g/s, and the high surface-energy powder flowed at only 11.0 g/s—about a 20% drop. Higher surface energy means stronger cohesion Fig. 1 — Effect of particle shape on powder spreading with a blade-type recoater: spherical particles (left) vs. angular particles (right). It was found that particle friction causes nonuniformity in film thickness. Created with Prometech Software. Fig. 2 — Effect of blade speed on powder spreading with a blade-type recoater: 50 mm/s (left) vs. 100 mm/s (right). It was found that overall film thickness decreases as the blade speed increases. Created with Prometech Software.
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