According to the needs of design and development of semi-solid vertical squeeze casting machine, a wheel like part (similar to worm gear blank) is selected as the prototype of squeeze casting. The shape and size of blank are shown in Figure 1.
According to the shape and size of the blank, considering the forming characteristics of squeeze casting, the part is a symmetrical revolving part, and one of the planes is selected to determine the position of the part drawing. Parting surface is how to determine the interface between convex and concave template of squeeze casting die. The part is relatively simple. Taking the upper plane as parting surface is conducive to exhaust and slag discharge, which is convenient to take out the parts, and will not produce dislocation and other defects. As the precision of squeeze casting parts is relatively high, there is no matching requirement for the worm gear in the height direction, so the machining allowance can not be put, and the allowance of 0.3mm can be put according to the outer diameter design. According to the requirements of squeeze casting parts, the outer diameter should be designed with demoulding angle, and the general design of aluminum alloy is 1 degree. Generally, the shrinkage of alloy must be considered when designing squeeze casting parts. In order to increase the service life of the die, there should be maintenance allowance when the die is worn, which can still reach the use tolerance range. In principle, the dimension of the cavity part is taken as the small value, and the dimension of the core part is taken as the maximum value of the basic dimension. The calculation formula of cavity part is as follows:
Where,
L ‘- the basic dimension of squeeze casting drawing used for die manufacturing;
L – the minimum limit size of squeeze casting parts;
Δ – dimension tolerance of squeeze casting parts;
L ε 1 – linear shrinkage of alloy for extrusion casting;
T – manufacturing tolerance of mould;
The dimension calculation formula of the core part is as follows:
Where,
D ‘- the basic dimension of squeeze casting drawing used for die manufacturing;
D – maximum limit dimension of squeeze casting parts;
The parts designed in the experiment only consider the cavity size, that is, the most outer circle diameter, and the tolerance is not indicated. They are manufactured according to GB / t1804-m. after checking the national standard, the tolerance Δ is 1 mm, t is generally (1 / 6-1 / 3) Δ, and 1 / 4 = 0.25 mm. Take ε = 0.5%. The minimum dimension of L (including machining allowance of 0.3mm on one side) = 160.6-1 / 2, Δ = 160.6-0.5 = 160.1.
Therefore, in the formula, there are:
Because the equipment used in the experiment is indirect squeeze casting process, a runner is designed at the lower part of the squeeze casting part. The diameter of the runner is equal to the diameter of the pressure chamber, which is indicated on the casting drawing. In addition, the drawing angle of 1 ° is increased with the small end dimension as 161.15. The specific shape and size of the squeeze casting part are shown in Figure 2.
