Wax Injection Process of Investment Casting

Wisdom is a manufacturer specializing in cobalt and nickel based investment casting components. Investment casting is also called lost wax casting, including wax injection, wax repair, group tree, dipping slurry, melting wax, casting molten metal and post-treatment. Next couple of articles will introduce step by step in details about the entire process.

Wax injection

After the mold is opened, the wax injection operation can be performed. The waxing operation should pay attention to factors including wax temperature, pressure and compression of the mold.

The wax used in the production of the wax pattern is generally paraffin having a melting temperature of about 60 ° C and a waxing temperature of about 65 ° C. Wax temperature and injection pressure are determined by the wax injection machine. The types of waxing machines are usually available in both pneumatic and vacuum. The wax injection principle of the two wax injection machines is basically similar i.e. the molten state wax is injected into the mold by using air pressure. The difference between the two is the vacuum waxing machine vacuum the mold before injecting the wax. Therefore, the operation is usually easier to master with a vacuum waxing machine, while the pneumatic waxing machine requires a certain amount of experience.

The heater and the temperature sensor in the wax injection machine enable the wax liquid to reach and maintain a certain temperature. Usually, the temperature of the wax in the waxing machine should be kept between 70 and 75 ° C. This temperature can ensure the fluidity of the wax liquid. If the temperature is too low, the wax liquid is not easy to fill the wax mold, resulting in the wax mold being defective; on the contrary, if the temperature is too high, the wax liquid to overflow from the gap of the mold or the wax injection port, and easily form a flash or burn fingers.

The pressure inside the wax cylinder of waxing machine is provided by the external air pump. It should be kept at 0.5~0.7at (or kgf/cm2), i.e. 0.051~0.071Bar. It can also be adjust according to the volume and complexity of the wax mold.

Before waxing, the mold should be opened first to check the integrity and cleanliness. If it is a used mold, it should be sprayed with a dewaxing agent (or a small amount of talc powder) in a relatively small and complicated shape, in order to facilitate the removal of the wax mold. Secondly, the wax injection machine should be preheated and then turn on the air pump and adjust the pressure and temperature.

When waxing, you should use both hands to clamp the mold in the splint, paying attention to the distribution of the fingers as the mold should be evenly pressed. Then let the mold nozzle be aligned with the wax nozzle. Do not move your hands after the nozzles are paired, and then gently press the wax switch with your foot and release it. Hold your hands for some time. After that leave the mold for a while, then you can open the mold (if the mold has bottom, you should first pull out the mold bottom) and take out the wax mold, and then check it carefully. If there are serious problems such as missing edges and broken feet, such wax patterns are defective products. If it is a small defect, the wax mold should be trimmed.

Stellite 6, 12 and 20 are the mostly used cobalt based alloys for investment casting. We’ve exported different types of components to global market, for example valve seat, valve ball, bar, plate, bushing etc. Welcome to contact us for quotation.