Low-pressure die casting agency one of the elements described
Low pressure casting product design basic requirement is the overall average of the thickness, or the thickness distribution of directional solidification considering the place is easy to implement. Is to say against the gate, the cross-section gradually from small to large product design change is required conditions, so if the product is not possible on the performance of this design is best to avoid the use of low-pressure casting method. In the cylinder head, cylinder block, wheels and other products in the popularity of using this method of casting the first reason is easy to achieve directional solidification shape.
Casting fairly simple program to enrich consider the overall directional solidification casting around the riser and the effect of the gate gate location, size, number of settings are also often required in black and white. The gate location should be the maximum overall thickness of the casting position, and to be located on the front and from above the molten metal reached about the site of directional solidification. Gene product shape, size, number of gates and other reasons vary, but is typically 1-4. If the position of the gate at the far wall thick riser unreachable, sometimes coupled with no top riser or transition bridge. But now the shape of a water-cooled cylinder head becomes huge, in order to achieve the desired thickness distribution monochrome often difficult to program on these topics in order to maintain directional solidification temperature control and the harsh conditions of management, credentials environment can also In the parts of a hot air, cooling water or cold iron buried. Preparedness to deal with the cross-sectional area of the gate molten turbulence in order to better fill the mold space in terms of black and white often stressful factors. The smallest cross-sectional area of the following formula:
(1) a = gate of the minimum cross-sectional area W = weight of castings (kg) T = from the gate at the beginning of the casting time (S) [filling time] m = proportion of molten metal (2.4 ~ 2.5) Υ = Resistance coefficient (0.3-0.4) g = gravitational acceleration (9.8m / s) H = pressure head (m) (melt noodles height from the upper to the product)
Made of round cross-section is an ideal, but what limited on the product shape is often forced to make an irregular shape. In this environment, in order to prepare the portion of the cold, the minimum cross-sectional area should preferably be similar to the product gate more than 2 times the wall thickness. Relatively low height of the gate can be lost because of the larger the gate providing heat and pressure caused by the feeding effect, and it is easy to achieve directional solidification, but it is prepare a solid oxide residues network site, the casting conditions due to changes caused by changes in the length of the gate, so as usual environment, consider 30-40mm more.
(2) the characteristics of tooling
Low pressure casting mold gate in the following, shown in Figure 5.4, under the type of pipe and some soup through a holding furnace maintained, so can not use the squeeze layout, while the use of the casting on the type or horizontal type in the method, the next type temperature is high, therefore undercut molds do need bigger than the other. The air inside the mold, sand core full account of the generated gas to exhaust typing method and so on, should be just even with the molten metal filling and reduce the back pressure generated environment crowding out. If the back-pressure high enough to affect the compression speed, it will produce molten flow of poor appearance shrinkage, etc., so look forward control 0.002Mpa less.
On bosses, ribs, blades, the shape of parts, can be considered embedded vent pull molds. In parting serene face design exhaust ducts, plus vent, drawing processing means exhaust just even do good design. Else sand core larger amount of gas generated, time is longer, the mold can be designed to determine the layout of the exhaust line, the additional suction mechanism.