The relationship between the quality of lost foam casting foam pattern the particle size of beads

Reason: The large particle size range of the original beads will cause the following problems ---

1.Due to the different particle size of the beads, the content of foaming agent is also different;

Under normal circumstances, the content of the foaming agent of the beads with large particle size is more, it is easy to volatilize when the beads are placed, it is easy to foam when the beads are pre-expanded.

The content of foaming agent for beads with a small particle size is relatively less. When the beads are placed in the same environment, they are more volatile than those with a large particle size. The density of the pre-emitted beads with the same parameter is higher than that of the large particle size. weight.

2.Due to the different particle size of the beads, the expansion ratio of the beads is also different;

Under normal circumstances, the expansion ratio of beads with a larger particle size is larger.

Beads with smaller particle size have a smaller expansion ratio,

This causes the pre-emitted beads to be uneven,

In density measurement, the pseudo density is actually measured.

For example: It is required that the density of the pre-expanded beads is 22 grams per liter, the specific gravity is also measured during the pre-expansion process;

Actually: The density of large-diameter beads after pre-expansion is 19 grams per liter; the density of small-sized beads after pre-expansion reaches 25 grams per liter.

3.Beads of different densities cannot be adjusted due to the different requirements of molding parameters during subsequent molding, resulting in large gaps between beads on the surface of the pattern, uneven surface, the quality cannot meet the requirements of the subsequent process.

4.During subsequent molding, due to the fixation of the existing filling method (beads filled into the mold cavity, lighter beads generally deviate the filling port), which leads to an increase in the density of the pattern partial filling The occurrence of insufficient material defects.

5.As the density of the pattern is broken, the strength of the pattern with higher density on the same pattern is better; the density increases, the strength of the pattern itself is weaker, resulting in deformation of the pattern.

According to our long-term engineer's research on the white area of lost foam casting a large number of customer tracking, the orientation range of the beads obtained by the service should be controlled within 0.15mm; this is the most suitable replacement for the foam beads for lost foam casting!