The simulation failure was due to a segmentation fault in LIGGGHTS, which may be attributed to a specific ill-conditioned placement of some simulation particles, in this particular run. This type of problem is sometimes reported in the LIGGGHTS User Forum . In the 2500 rpm simulation, we can observe a tendency for the tagged AM and BC particles to stick at the end part of the extruder after the first passage through the recirculation circuit. A blockage phenomenon can be observed at the end of the extruder barrel, but at around 50 M 𝛥𝑡, a bunch of the blocked particles manage to go through the narrow region. This cancels the blockage phenomenon, and we see the tagged particles smoothly go into the recirculation circuit. In Fig. , the curve of 2500 rpm shows the significant change in porosity; in the particle blockage condition, the porosity is reduced to about 25 %, of the same order as the simulation under the sequential injection using 2500 rpm of rotation speed. After the blockage release, the porosity is quickly almost back to the initial peak. With the mixing action of the extruder, the particles are compressed and rearranged again. At around 67 M 𝛥𝑡, the porosity reaches again a low point: it returns to around 29 %, after which there is a slight pick-up. In the simulation at 5000 rpm, the AM and BC particles entered the extruder simultaneously and were quickly mixed. It can also be seen from Fig. that the porosity of the microstructure varies with time, hovering between 30 % and 36 %, and finally roughly stabilizing at around 33 %.