Production conditions and technical requirements
Casting material: HT200.
Casting shape: There are two bosses on the ground, with a hollow in the middle and an arc-shaped frame on top. The structure is shown in Figure 1.
Fig. 1 Structural diagram of the shaft support
Casting size:
The ground thickness is 5mm, and the boss height is 7mm.
Casting weight: 5kg
Service conditions:
The shaft bracket is used to support the shaft parts. There are two bosses on the bottom, and the middle part is hollow and irregular in shape. The upper semicircular groove is used to place the shaft parts.
The main technical requirements for the shaft support include its mechanical properties and load-bearing capacity, as it is a small, thin-wall casting designed for this purpose.
For this application, the HT200 casting is suitable and meets the necessary requirements. While the overall dimensional accuracy of the shaft support body may not be critical, the parallelism and thickness of the bottom surface, as well as the height gauge of the boss, must meet assembly requirements. Additionally, the surface finish must meet aesthetic requirements.
After casting, the semicircular groove that matches with the shaft parts must be machined to ensure proper dimensional matching.
Casting techniques
Casting Process Type: Sand Casting using three-box molding
Mold Design and Parting Surface Selection: Please refer to Figure 2 for the mold design.
The casting’s middle hollow structure and upper semicircular structure are formed using a mold core.
Fig. 2 Schematic diagram of model, parting surface and box surface
Based on the structure and shape of the casting, three boxes have been selected for molding. The surface of the casting box serves as the mold parting surface, as indicated by the dotted line in Figure 2.
Core selection:
To create the middle hollow and upper semicircular structures of the casting, two sand cores are needed.
The sand core used to make the middle hollow structure should have the same shape as the hollow part of the casting.
A fixing device should be present at the rectangular plane to secure the sand core in the upper box molding sand after mold lifting.
The fixing device must avoid the sprue and have minimal interference with the transverse sprue.
The core used for the upper semicircular structure should be semi-cylindrical, with a diameter smaller than the casting’s semicircular structure, leaving a machining allowance of 3mm.
The center of the semi-cylindrical’s rectangular longitudinal section should have a fixing device to secure the core in the lower box molding sand after mold lifting.
Pouring position selection:
Since the main body of the casting is a thin-walled, hollow structure, the gate should be placed above the center of the rectangular plane of the shaft support. To ensure even flow of the liquid metal along the wall of the frame, a transverse gate should be set.
Solidification principle:
The self-hardening sand mold, made with resin, is used to maximize graphitization expansion and achieve self-feeding of castings.
The gating system functions as the main riser, with several air holes punctured through the molding sand of the upper box.
Modeling method:
The castings are small and directly molded in a small sand box using three boxes. After creating the sprue, the mold is lifted and the core is installed, followed by the creation of the transverse sprue. Finally, the box is closed and ready for pouring.
Main specifications
Machining Allowance:
A machining allowance of 3mm should be reserved for the large plane at the end and the upper parts of the two bosses.
In the direction of the semicircular structure, a machining allowance of 3mm shall also be reserved.
No machining allowance is necessary for the other parts.
No casting hole:
As the internal hollow structure of the casting can be cast through the installation of sand core, there is no need to design a casting hole on the mold.
Formwork lifting slope:
The casting is small in size. According to its dimensional parameters, the required draft angle on the table should be 2.20°.
Casting shrinkage:
The casting is small, and its shrinkage mode is restricted shrinkage. The casting shrinkage rate is 0.8% to 1.0%.
