Manufacturing Technology concept on the gearwheels, 3D rendering

DIE-CASTING:

Die casting is a metal casting process characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool metal dies, generally made of steel, which have been machined into shape and work similarly to an injection mold during the process.

Stilopress only employs hot-chamber machines in which the molten metal tank is inserted in a furnace. The hot-chamber process, thanks to the presence of the furnace, will ensure a greater control of the operating temperature and high production rates, as a matter of fact the direct withdrawal from the tank makes the process faster. Moreover considering that the tank is larger, the alloy is more uniform in the composition and temperature compared to the cold-chamber, therefore also the structure of the product will be more homogeneous.

The injection pressure of the molten metal can vary from 2 to 150 MPa depending on the case: the pressure is maintained for the duration of the process until the glass solidification, while the hydraulic presses guarantee the closing of the mold even at high operating pressures. To ensure the quenching of the work piece, there is a liquid circulation system inside the mold. Once solidified and cooled the piece, the presses open the two molds so that it can be withdrawn.

The process is highly automated, therefore it has an elevated productivity. In addition, due to the nature of the molds, if the molten metal tank is inserted in a furnace the pieces produced with the die casting will have dimensional tolerances and surface finishing average better compared to other hot-chamber die casting processes.

The two main parameters to be set in the die-casting process are about pressure and temperature. Pressure should take into account certain desired characteristics in the process: a high pressure will facilitate filling times of lower molds, achieving greater productivity, while lower pressures avoid defects in the part due to the excessive speed of the molten metal, and they can also provoke less wear of the form. The high pressure values ​​also allow to increase the maximum permissible concentration of dissolved gas in the metal; this greatly reduces the risk of blowholes in the finished piece/item, provided that the pressure exerted persists until the complete solidification of the piece.

Stilopress group, besides the production of items with a particularly complex design, adopts the technology of vacuum with the aim of facilitating the filling of the form at the same pressure. This technology creates a strong vacuum inside the mold, in order to obtain a difference of additional pressure in the injection of the liquid.

POLISHING:

Depending on the different aesthetical and mechanical characteristics of each article, the polishing process can be automated or manual. For items with high aesthetic value, with complex geometries, requiring final surface such as electroplating treatments, painting and/or PVD. The polishing is a critical step to obtain a product realized according to the rules, which is best able to meet the highest quality standards. In these cases it is preferable the manual cleaning, which only experts artisans are able to do.

GALVANIC:

The tests:

  • Salt- fog test guaranteed for more than 220 hours according to ASTM B 117/97 DIN 50021 SS – UNI ISO 9227 NSS
  • Thickness gauge test: UNI ISO 2177 , with thicknesses CU 22 NI 18 CR 0,4 monitored micron
  • Thermal shock and grid according to UNI ISO 2819.