The theoretical basis of casting process CAD system design is the process design method used in the actual production of steel castings. According to the actual casting process design method, it is abstracted by program language and expressed in the process CAD system in the form of graphics.
In the production practice of large steel castings, the foundry workers in Erzhong foundry summarized a set of casting process design method suitable for large steel castings according to various experience. According to this method, Huazhu software center designed and developed the casting process CAD system of large steel castings. The following will specifically introduce the casting process design method of large steel castings.
(1) Process correction quantity
In the actual production of steel castings, dimensional deviation will be caused by shrinkage, deformation and improper production operation, which will reduce the wall thickness of steel castings too much after processing. In order to avoid the impact of this phenomenon, it is necessary to increase a certain thickness on steel castings, which is related to the structure, processing mode, pouring position, wall thickness and modeling materials of steel castings.
(2) Non cast hole
The hole or groove on the workpiece shall be cast during pouring as far as possible, so as to save the amount of metal for pouring and the time of machining, so as to reduce the production cost. However, not all holes and grooves can be completed during pouring. Some holes or grooves have complex structures and require a very difficult casting process. At this time, machining can be used to complete the processing of holes or grooves. For large steel castings, holes or grooves without casting can be processed according to the usual processing method. Those that can be cast can be cast, and those that cannot be cast directly can be machined.
(3) Subsidies
For steel castings with high density requirements, when the feeding distance of the riser is insufficient, subsidies can be set on the side of the riser (for horizontal feeding) or below the riser (for vertical feeding) to cause sequential solidification in the direction of the riser, so as to increase the feeding distance of the riser. There are two design methods of subsidies, namely, chart experience method and rounding method. The chart empirical method is summarized according to a large number of production practices. This method is usually very complex in classification. The rolling circle method draws the subsidy by means of geometric drawing. Firstly, the first thermal pitch circle needs to be designed, and the subsequent thermal pitch circle determines the radius and draws it according to the previous thermal pitch circle according to a certain mathematical formula, and then completes the subsidy design according to the drawn thermal pitch circle.
(4) Core head and core seat
When the iron core head and iron core base need to be used in process preparation, the provisions are as follows:
① Select the appropriate size according to the specification table and indicate it on the drawing, for example: Φ 100 iron core head and iron core base.
② When the model is made, the relevant parts shall be made according to the following provisions: when the model is made as the positioning platform of the external iron core base Φ 1. Make a decision. When making the iron core head seat in the core box, its size shall be as follows: Φ< When 100mm, press Φ 1 + 1mm, H1 + 1mm; When Φ When ≥ 100mm, press Φ 1 + 2mm, H1 + 1.5mm.
③ The electric furnace workshop and steel casting workshop are prepared for production according to the specifications in the process drawings.
④ For the iron core head and iron core base with special requirements, the specific design requirements shall be given in the process drawings or relevant documents.