How to solve shell cracking in precision casting

How to solve shell cracking in precision casting

Cracking of the mold shell is actually a normal occurrence in investment casting, whether it is during dewaxing or during roasting and pouring. The cracking of the shell can only indicate one issue, which is the insufficient strength of the shell, which may be at room temperature or high temperature. So, for shell cracks, the first solution is to find out where the strength difference of the shell is. Today, precision casting manufacturer Tianyao Metal will talk to you about how to solve the problem of shell cracking.

Cracks. In fact, we are not taking this seriously because investment casting belongs to models without parting surfaces. In short, there are burrs on the smooth surface, and the molten metal is the most authentic. Whatever your mold looks like, I can replicate it. Based on this principle, we believe that the burrs on top are actually caused by shell cracking.

So, what is the cause of shell cracking? Overall, the strength of the shell is insufficient to resist the stress of wax expansion during dewaxing or the static pressure and thermal shock resistance of the metal under high temperature conditions.

1、 Do you want to check if your mold shell cracks after dewaxing? In many cases, people analyze and don't know what the reason is. It's very simple. Let's first break a shell and see if there are any cracks inside the dewaxed shell. Generally speaking, we should exclude factors such as whether the drying and wax discharge are smooth, as well as the setting of parameters for the dewaxing kettle. It should be pointed out that factories sometimes increase the tree formation rate without restrictions in order to reduce costs, which is a great test for the shell making process and product quality. In fact, it is not clear what problems exist with wax removal and drying. Personally, I believe that the high tree formation rate makes it difficult to achieve qualified shell production in the shell making process, which is a major factor. Of course, the thickness of the shell is also an important consideration and a component of strength.

2、 If your shell does not crack after dewaxing, then you need to check the condition after baking. Generally speaking, if the dewaxed shell has no cracks, the baked shell will not crack either. So, your second smashing should be done after roasting and before pouring. If your shell cracks after dewaxing, it will only expand after baking and will not disappear. Of course, if there are no cracks in both of these processes, then there may be a problem with the refractory material of your shell.

To sum up: What to do when encountering shell cracks? First, divide the area and identify which area has the problem, using the method of destruction; After identifying the area, make improvements accordingly. There are problems in the dewaxing area, and the reasons should be identified from the aspects of drying, shell thickness, dewaxing smoothness, and parameter settings of the dewaxing kettle; If there is a problem with pouring, find a solution based on the thickness and quantity of the surface layer.

Precision machining