Gating System Design
Because the iron mold of the iron mold sand coating process has sufficient rigidity, it can realize the riserless casting, which can effectively improve the process yield. Generally, the production rate of crankshafts of about 40 kg is about 90%. Because the castings produced by the iron mold sand coating process are easy to form tiny slag inclusions, in the case of no riser, the design of the pouring system should especially consider the purification of the molten iron. Therefore, the pouring system should be designed as a semi-closed form to facilitate the floating of inclusions and at the same time to filter the molten iron. There are two methods for filtering molten iron, one is filter screen and the other is ceramic filter.
The filter is cheap, but the filtering effect is poor, and it is easily broken by molten iron during use, so ceramic filters are mostly used in actual production (Figure 6). In order to reduce the cooling of the molten iron flowing through the gating system, reduce the premature fatigue cracks of the iron mold at the gating system due to overheating, and at the same time, to avoid the premature solidification of the gating system when the casting is solidified and the liquid feeding of the casting cannot be achieved.
The sand coating is thicker than the sand coating of the casting. Generally it is 8～10 mm. The design of the sand-shooting board The sand-shooting board is connected with the sand-shooting head. During sand shooting, the iron mold is pushed up and pressed against the sand-shooting board and aligned with the sand-shooting hole, and the coated sand in the shooting head is injected into the iron-shaped cavity. Since the iron mold will deform after being used for a period of time, the sand shooting head and the iron mold cannot fully contact during sand shooting, and sand will run out, which not only wastes sand and pollutes the environment, but also causes false sand shooting in the cavity. Therefore, insert a high-temperature resistant silicone sleeve at the perforation of the sand-shooting board and make it protrude 3～5 mm from the plane of the sand-shooting board. There are generally two types of layout of the sand-shooting head and the pattern of the current double-station molding machine.
One is that the upper and lower type respectively correspond to a sand shooting head, the pattern is directly below the sand shooting head, and the pattern only has one movement up and down, which is shaped by the horizontal movement of the iron; the other is the upper and lower type share a sand shooting head, after shooting After sanding, the iron mold and the shape are removed together. The first situation: when the sand is shot, the iron mold is baked against the sand shot board. After the iron mold is removed, the shape and template are still baked on the sand shot board, so that the coated sand inside the sand shot head is easy to solidify and agglomerate. In this case, the sand shooting board must be designed with a water cooling system to prevent the coated sand from solidifying. The second case: the iron mold is only used to bake the sand shooting board during sand shooting. After the sand is shot, the iron mold and the pattern are removed together because the sand shooting time is very short and only takes 3 to 4 seconds, which will not cause the shooting head. For the solidification of the inner coated sand, the cooling system may not be designed when designing the sand shooting board.
Top hole cone plate
The top hole cone plate is used to push out the solidified sand of the iron-type sand shot hole through a cone to facilitate the next cycle of modeling. Generally, there are many sand shot holes on the iron type, for example, there are more than 20 four-cylinder crankshafts. If the length of the top hole cone is the same, and the top hole is in contact with the iron type at the same time, a lot of force is required to push through. In order to resolve this force and facilitate the top hole, the top hole cone can be made into different lengths. The design of the template base and the falling sand bucket mainly considers the height design. After being jacked up, it can fully contact and maintain a certain pressure, and after falling, the iron mold can be moved freely.