What are the defects of wax molds in precision casting

What are the defects of wax molds in precision casting

Due to various reasons in the production process of precision casting, wax molds produced by wax forming machines may have some defects. Today, we will analyze the defects of wax molds in precision casting.

1、 The wax model is not fully filled and lacks meat

1. The temperature of the wax material is relatively low, cold wax

2. The slow injection speed and low molding temperature cause the wax material to cool quickly during the flow process

3. There is cold residue on the wax nozzle

4. Improper nozzle position

Manifested in insufficient filling of corners and edges or thin-walled parts of wax molds, with rounded corners appearing at edges, similar to insufficient pouring in metal castings.

2、 Wax bubble

1. Wax flow rate too high

2. Improper exhaust in mold design, wax containing moisture

3. Wax temperature too high

One type is surface bubbles, which are visible subcutaneous bubbles to the naked eye, with individual distributions and dense distributions; Another type is the deep bubbles in wax molds, which are usually concentrated and large bubbles that cannot be seen by the naked eye, but bulge locally from the wax mold and appear in the center and final cooling part of the wax mold. This is the result of the release of internal pressure and gas expansion.

3、 Surface wrinkles

1. Insufficient wax temperature and low injection speed

2. Improper coordination between wax movement and molding temperature

3. Due to damage or lack of cleanliness on the inner surface of the mold, improper placement of chilled metal blocks, etc

Wax molds leave traces of movement on the surface, with deep patterns similar to cold shut defects in metal castings; Minor wrinkles can be polished off. Another issue is that around the core and holes, sometimes seams can be seen, slightly concave. In fact, the convergence of the two streams of wax is not well fused, which is the result of insufficient temperature and pressure of the wax material.

4、 Wax mold depression

1. The gas content of wax is too high

2. Insufficient injection pressure and time

3. The wax material has a high temperature and insufficient cooling time

Too much release agent may also cause a decrease in the properties of the wax. Surface shrinkage involves a large area and repair is relatively difficult.

5、 Wax mold deformation

1. After the wax mold is removed from the molding, in addition to a reduction in size, it is also artificially deformed due to improper removal techniques

2. The wax injection pressure holding time is too short

The wax mold is still cooling, causing a change in temperature field and bending deformation. Therefore, the wax mold that has just been taken out of the mold should still be carefully placed, usually flat based on a larger plane. If necessary, a shape suitable for the deformation part should be used to make a metal block embedded in the wax mold to prevent deformation, that is, to fully cool it. It is also possible that the wax is too soft, and the components of the molding are not suitable.

6、 Wax model fly edge, feather wings (draped seam)

1. The mold is too dirty and the loss causes the wax flakes to escape from the joint

2. Excessive wax injection pressure

3. Die temperature too high

Mainly due to insufficient molding accuracy, damage or adhesion of unclean substances to the parting surface or internal parts of the mold, or insufficient molding force, resulting in excessively high injection pressure. Or the temperature of the wax may be too high. The hairy wings must be thoroughly removed before the wax molds can be used.

7、 Wax mold cracking

1. Excessive wax injection pressure holding time and high pressure

2. Missing draft angle during mold removal

Precision machining