Importance and control method of wax shrinkage rate in precision dewaxing casting

With the continuous development of economy and industry, people's demands and requirements for products are getting higher and higher. At the same time, the ability of precision dewaxing casting technology to solve the complex structure of products has also been recognized by the industry. The general precision dewaxing casting process includes water glass, silica sol, composite process and so on. Among these processes, the silica sol process meets the requirements of the highest casting quality and the lowest processing speed. Because of its high density, it is widely used in casting products, such as small and medium parts and ultra-small parts.
The process steps of silica sol dewaxing casting are as follows:
Pressing wax (wax injection molding)-wax repair-wax mold inspection-group tree (wax mold)-shell making (first dipping, sanding, re-dipping, and finally air-drying the shell)-dewaxing (steam dewaxing)-shell baking -Chemical analysis-pouring (pouring molten steel into the mold shell)-vibration dehulling-pouring and pouring rod cutting separation-wear gate-shot blasting cleaning.
It can be seen that half of the process is related to the wax mold. Because the precision tolerance of CT6 silica sol dewaxing casting can be guaranteed, the smallest tolerance precision is only plus or minus 20 filaments. Therefore, the shrinkage requirements of the wax mold used in the process are very high. In each step, the shrinkage of the wax mold is closely related to the size of the subsequent product. Therefore, the quality of wax mold is one of the important factors that directly affect the quality of castings. The size of the wax mold directly determines the size of the finished product after casting. Therefore, in the silica sol dewaxing casting process, green medium temperature wax with high stability is usually used. Water glass and composite dewaxing casting process usually use white low temperature wax, which is more advantageous in terms of cost.
This article introduces the stability control method of medium temperature wax adapted from BesserCasting in detail.
After long-term use, some components of the medium temperature wax material will be oxidized and deteriorated. In addition, metal ions will also enter the wax material, making the wax worse and containing more impurities. To make matters worse, the shrinkage of wax is very different from the shrinkage of new wax. Because shrinkage is different from solid impurities, it is difficult to completely solve it by precipitation dehydration or filtration alone. In order to ensure the overall stability of the wax, the factory must regularly remove part of the old wax and add new materials. In the case of large shrinkage fluctuations, it is necessary to separate part of the wax and increase the input ratio of new wax to neutralize the shrinkage rate of the wax. Now there are professional manufacturers of medium temperature wax, which can regenerate waste wax. Due to the special impurity removal process, the ash content in the regenerated wax can be lower than that in the original new wax, and other properties can be adjusted at will. Companies with general capabilities will also equip their factories with a system of medium temperature wax degradation and dehydration devices, which can greatly stabilize the shrinkage rate of medium temperature wax. It can be seen that different factories have different treatment methods, and different molds can be directly replaced to ensure the shrinkage of the original mold.
In order to strictly and stably control the shrinkage rate of the medium temperature wax, the quality of the medium temperature wax is very important. We need to control the wax material from the source, reduce the impurity content, pay attention to the treatment and use process of the wax, and do not allow high temperature treatment to extend the service life of the wax material. In order to control the shrinkage rate of medium temperature wax in real time, the factory will customize a mold specially used for the size measurement of wax parts and set up a designated waxing machine. In addition, professionals are assigned to operate the machine strictly in accordance with the specified parameter settings. At the same time, experts measure wax patterns and record data every day, compare the latest data, and confirm whether it is necessary to adjust the current operation.
In addition to the above control and supervision, in daily production, in order to control the size of the finished wax film, the setting parameters of the waxing machine must be set strictly according to the values ​​given by the technicians. part. Due to the high temperature of the medium temperature wax during the injection process, it will shrink slightly after cooling and forming, that is to say, the size will change slightly. If the temperature, pressure and time values ​​do not match during the waxing process, it will directly lead to the loss of waxing size control.
Hongzhe Hardware Casting is not only committed to providing customers with eye-catching casting solutions, but also committed to providing customers with stable mass product quality. The latter is the purpose of our strict process control, including the wax shrinkage rate discussed in this article.