You can simulate an A-B-A sequence of a Co-injection molding
process.
During an A-B-A sequence, first a skin
material (polymer A) is injected followed by a core material (polymer B). Toward the end
of the process, a small amount of the skin material is reinjected to ensure the complete
encapsulation of the core material.
The image shows settings for an A-B-A
sequence where 60% of the cavity fills with material A. After a time delay of 0.2
seconds, material B is injected to fill 35% of volume. Injection switches back to
material A to fill the last 5% of cavity volume.