Thermoforming against Injection for Volumes below Fifty Thousand Units
Thermoforming delivers lower total landed cost below fifteen thousand units by saving upfront tooling capital, beyond which injection piece price efficiency dominates.
Porous Aluminum
Meaning
Sintered metal alloys with open-cell porosity allow air to escape directly through the mold walls during forming operations. This tooling material, often called porous aluminum, contains microscopic voids that permit gas flow while preventing the polymer melt from entering the pores. It governs the venting efficiency of injection molds and thermoforming tools.
It is restricted to regions where mechanical wear and clamp forces are moderate.
Venting Mechanism
Entrapped air is a common cause of burn marks and incomplete cavity filling in injection molding. When using porous aluminum inserts, the pressurized gas vents through the mold body rather than through narrow parting-line vents. This continuous venting reduces the injection pressure required to fill the cavity.
Tool Manufacturing
Toolmakers can machine this material using standard milling and wire electrical discharge machining methods. Because the porosity must remain open, care must be taken during polishing to avoid smearing the metal surface and blocking the air passages. Regular cleaning with solvents or ultrasonic baths maintains the airflow.
Surface Quality
Using a porous metal insert eliminates the need for visible vent pins or parting-line vents that leave witness marks. Parts molded with porous aluminum have a uniform matte finish across the vented areas. This improves the cosmetic appearance of consumer housings.