The Gate Function of Investment Precision Casting

The Gate Function of Investment Precision Casting

The gate function of investment casting is definitely something that everyone can talk about. For example: wax removal, water diversion, and replenishment. But in reality, it is unknown whether people consider it this way when designing. This may be a common problem among most casting engineers. Today, precision casting manufacturer Tianyao Metal will talk to you about the gate functions of investment casting.

Investment casting is mainly used for small and medium-sized parts, ranging from a few grams to several kilograms, and its gating system is relatively simpler compared to sand casting. For example, what we usually use is basically a straight rod shape, a gate shape, or a straight line shape. Unlike sand casting sprues, sprue cups, sprues, runners, overflow pits, internal gates, exhaust channels, and so on. However, its goal is the same as that of sand casting, which is to obtain high-quality castings. Therefore, relatively speaking, the gating system of investment casting is a bit more aggrieved than the gating system of sand casting. However, regardless of whether you are wronged or not, the things that need to be completed cannot be inferior at all. Therefore, attention must be paid to the design of the investment casting pouring system. This heart includes: being careful and serious.

Due to the fact that most of the investment casting runners have already been designed, the engineer's remaining work is only to connect themselves with the runners. Although it may seem simple, in reality, it still requires careful consideration. Why do you say that? Because of the function of the casting gate. As mentioned earlier, diversion not only needs to guide metal flow, but also needs to guide wax flow and supplement contraction. I want to emphasize one point here, most people may have forgotten another thing, which is slag blocking and exhaust. This is also an important function of investment casting gates. Due to the inherent reasons of the investment casting pouring system, 80% of the slag blocking function may need to be completed by the internal gate. (This data is my own estimation without any basis, only indicating the importance) The exhaust can be designed with an additional exhaust groove, but if both can be considered, of course, it is not desirable. So, the position and shape of the gate are relatively important.

Many people in our factory design gates and do not like to use inclined gates. Of course there is a reason for it. Adding a slanted gate on the mold can lead to complex mold structure and may pose a risk of difficulty in demolding. It not only affects efficiency but also easily deforms the wax parts, so it is better to use a gate without a slope. This type of gate is not good for filling and shrinking, and does not have slag blocking, so it is not a good gate design. The implementation of slag blocking function requires two methods: 1. Slow speed and long process; 2. By changing the cross-sectional area of the flow channel. The first solution is suitable for sand casting, and the second design is suitable for investment casting. Therefore, using a slanted gate with both filling and slag blocking functions is the best choice for investment casting.

Of course, where the cross-sectional area changes, it is best to have a smooth transition to reduce the impact of material flow on the mold cavity and the probability of sand inclusion defects.

Precision machining