The design of ship inspection castings must take into account seven aspects: die casting wall thickness, die casting fillet and demoulding slope, reinforcing rib, casting hole on die casting and small distance from hole to edge, rectangular hole and groove on die casting, insert in die casting and machining allowance of die casting.

Design specification for casting fillet: generally, each part of the die casting shall have a fillet (except at the parting surface), so that the metal can flow smoothly during filling, the gas can be easily discharged, and the crack caused by the acute angle can be avoided. For die castings requiring electroplating and finishing, the fillet can be coated evenly to prevent coating accumulation at sharp corners. Generally, the fillet radius r of die-casting parts should not be less than 1mm, and the smaller fillet radius is 0.5 mm.

Design specifications for inserts in die castings: first, the number of inserts on die castings should not be too large; Secondly, the connection between the insert and the die casting must be firm, and at the same time, it is required to slot, bulge and knurl the insert; Thirdly, the insert must avoid sharp corners to facilitate placement and prevent stress concentration of the casting. If there is serious electrochemical corrosion between the casting and the insert, the surface of the insert needs to be protected by plating; Heat treatment shall be avoided for castings with inserts to avoid volume change caused by phase transformation of two metals and looseness of inserts.

Design specification for wall thickness of die castings: thin wall die castings have higher strength and better compactness than thick wall die castings. In view of this, the design of die castings should follow the principle that the wall thickness should be reduced as much as possible and the uniformity of the wall thickness should be maintained on the premise that the castings have sufficient strength and rigidity. Practice has proved that the wall thickness of die casting parts is generally 2.5-4mm, and the parts with wall thickness more than 6mm should not be produced by die casting process. The influence of too thick and too thin wall on the casting quality: if the casting wall is too thin in the design, the metal fusion will be poor, which will directly affect the casting strength and cause difficulties in molding; When the wall is too thick or seriously uneven, it is easy to produce shrinkage and cracks. On the other hand, with the increase of the wall thickness, the defects such as porosity and shrinkage porosity in the casting will also increase, which will also reduce the strength of the casting and affect the quality of the casting.

Design specification for machining allowance of die-casting parts: generally, due to the limitations of the die-casting process, when some dimensional accuracy, surface roughness or form and position tolerance of die-casting parts fail to meet the requirements of the product drawings, the enterprise should first consider using finishing methods such as correction, polishing, extrusion and shaping to repair. When finishing cannot completely solve these problems, Some parts of the die casting should be machined. It should be noted here that small machining allowance should be considered when machining, and the surface not affected by parting surface and movable molding should be taken as the blank reference surface as far as possible to avoid affecting the machining accuracy.

Design specification for demoulding slope of die casting parts: when designing die casting parts, there should be structural slope on the structure. If there is no structural slope, there must be a demoulding process slope where necessary. The direction of inclination must be consistent with the direction of casting demoulding.

Wall thickness, wall connection form and fillet at the connection

Wall thickness design principle: thin wall, uniform wall thickness

It is difficult to form large area thin wall; If the wall thickness is too large or seriously uneven, it is easy to produce shrinkage porosity and cracks.

Effect of wall thickness of die casting machine on tensile strength

Therefore, in die casting, it is wrong to simply increase the wall thickness to improve the strength.

In general, the wall thickness should not exceed 4.5mm, and the ratio of large wall thickness to small wall thickness should not exceed 3;

Suitable wall thickness of medium and small die castings

Zn alloy: 1-3mm, small 1.0mm

Al and Mg alloy: 1.5-4MM, 0.8mm thin

Cu alloy: 2-4mm, 0.8mm thin

The larger the overall size of the die casting, the thicker the wall thickness; When the wall thickness is fixed, the area is also limited. For large aluminum alloy die castings, the wall thickness should not exceed 6mm;