Mold manufacturing

Casting parts design requirements and precautions

Casting parts design requirements and precautions
 
Casting parts design requirements
First, the shape of the die casting structural requirements: a, eliminate internal undercut; b, to avoid or reduce Pulling site; c, to avoid crossing the core;
Reasonable casting structure not only simplifies the structure of die-casting type, lower manufacturing costs, but also to improve casting quality,
Second, the wall thickness of the casting design requirements: die casting wall thickness (usually nominal wall thickness) is a factor in a die casting process has a special significance, the wall thickness of the entire process specifications are closely related, such as the calculation of filling time, the gate speed selection, calculation of clotting time, analyze the mold temperature gradient, pressure (final pressure ratio) of action, the length of time left mold casting ejection temperature level and operational efficiency;
a, the wall thickness of the mechanical properties of the parts would die casting partial thickness decreased, thin-walled castings good compactness, the relative increase of the intensity and pressure of the casting;
b, the wall thickness of the casting can not be too thin, too thin can cause adverse aluminum liquid filling, forming difficulties, poor welding of the aluminum alloy casting surface defects such as cold shut easy to produce and difficult to die-casting process;
Casting as the wall thickness is increased, the internal porosity, shrinkage and other defects increased, so the casting of ensuring sufficient strength and rigidity of the premise, should minimize the thickness of the casting and to maintain uniform thickness section, in order to avoid shrinkage and other defects, for thick-walled castings should be reduced at the thick (less material), increased muscle; for large area flat class walled castings, set up to reduce the thickness of the casting rib; based on reasonable surface area die casting, aluminum die casting wall thickness as follows:
  
Casting surface area / mm2
  
Wall thickness S / mm
≤25
1.0 to 3.0
> 25 - 100
1.5 to 4.5
> 100 ~ 400
2.5 to 5.0
> 400
3.5 to 6.0
Third, the casting rib design requirements:
Role ribs after thin wall thickness change, to improve the strength and rigidity of parts, preventing the reduction of the casting shrinkage and avoid distortion occurs when the top of the workpiece from the mold for action auxiliary circuit (metal flow path) filling , casting rib thickness should be less than the thickness of the wall is located, and generally where the thickness of 2/3 to 3/4;
Fourth, casting rounded design requirements:
Casting on all the walls and wall connections, regardless of right angles, acute or obtuse, blind holes and roots grooves should be designed rounded only when the site is expected to determine the parting surface, it does not connect with rounded corners Other locations generally must be rounded off to not be too big or too small, too small casting easy to crack, easy to produce loose excessive shrinkage, casting rounded general admission: 1/2 wall thickness ≤R≤ thick;
Fillet role is to help the flow of metal to reduce eddy or turbulent; avoid the presence of rounded corners on parts and stress concentration caused by cracking; when the parts to be plated or coated, rounded obtain uniform coating to prevent deposition sharp corners; can extend the life of die-casting mold, not because of the presence of sharp corners of the mold cavity and lead to chipping or cracking;
Five die casting foundry gradient design requirements:
Gradient effect is to reduce the friction casting and the mold cavity, easy to remove castings; casting surface to ensure no strain; extend the life of die-casting mold, aluminum die casting foundry general minimum slope as follows:
  
Aluminum die casting foundry minimum slope
  
The outer surface
The inner surface
Core hole (unilateral)
1 °
1 ° 30 '
2 °
Note casting part design
First, the casting design involves four aspects: a, namely pressure casting for the part shape structure requirements; process performance b, die castings; dimensional accuracy and surface requirements c, die casting; d, casting parting surface determination;
Die casting parts casting production technology in the design is an important part of the design must consider the following issues: selection of mold parting surface, the gate opened, select the jack position, shrink casting, casting dimensional accuracy assurance, casting precautionary aspects of internal defects, cast holes with the relevant requirements, and the requirements of shrinkage allowance of size;
      Second, the design principles of die castings are: a, the correct choice of materials die casting, b, reasonably determine the dimensional accuracy of the die casting; c, try to make the thickness distribution; d, each corner of the additional process rounded corners, to avoid sharp corners .
    Third, according to the use of die casting requirements can be divided into two categories, one bear a greater load of parts or a higher relative velocity of the parts, check the project size, surface quality, chemical composition, mechanical properties (tensile strength , elongation, hardness); the other for other parts, check project size, surface quality and chemical composition.
In the design of die casting, it also should be noted that the part should meet the die-casting process requirements. Die-casting process of parting from the position, the position of the top surface of the plunger, the casting hole of the relevant requirements, the relevant requirements of shrinkage and the allowance of the size and other considerations. Reasonably determine the parting line die-face, not only to simplify the structure of die-casting type, but also to ensure the quality of the casting.
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