Wax Mold Cleaning for Precision Casting Shell

Wax Mold Cleaning for Precision Casting Shell

Complete cleaning of the surface of the wax mold module during precision casting production is crucial for obtaining high-quality and excellent castings. This is a sentence from Mr. Yamaguya Yangshu's "Practical Technology of Precision Casting". From this sentence, we can understand the importance of wax mold cleaning for the shell making process. However, this important process is often overlooked by most investment casting manufacturers. Today, precision casting manufacturer Tianyao Metal will talk to you about the cleaning of wax molds before shell making.

We often refer to information that more than 50% of the defects in investment casting come from the shell making process. However, how many defects come from the uncleaned wax mold module and poor cleaning? In the surface defects of castings, the quality of the casting surface is good, and it is necessary to ensure that the surface coating can wet the wax mold well. Copying the wax mold can ensure that the surface roughness of the mold shell is low, and thus ensure that the surface of the casting is smooth and flat; The formation of iron beans at the corners of the casting surface is also due to the poor wetting of the wax mold by the surface coating. We are not sure how many factors are caused by poor cleaning of the wax mold, but at least there are factors related to poor cleaning of the wax mold; In addition, the bulging of the large flat surface is often related to inadequate cleaning of the wax mold module, resulting in the separation of the wax mold and the surface coating. In the cucumber thorn defect on the casting surface, due to inadequate cleaning of the wax mold surface, the surface coating selectively adsorbs, which is closely related to wax mold cleaning. Therefore, we cannot simply treat wax mold cleaning as an optional process, and must take it seriously.

The purpose of wax mold cleaning is to remove the parting agent, wax shavings, and moderate etching (also known as degreasing treatment) on the surface of the wax mold, and improve the wettability between the wax mold and the surface coating. In the process of using wax mold cleaning agents, there has been a transition from being harmful and toxic to being pollution-free and environmentally friendly. The first to be used are trichlorides, alcohols, ketones, etc., which are highly harmful and toxic. In addition, halogenated organic solvents such as dichloroflurane and trichloroflurane have also been used as fluoride solvents. In order to be environmentally friendly and pollution-free, people have developed water solutions with special surfactants, which are modern wax mold cleaning agents.

When is the module cleaning selection? Mr. Yamaguya Yangshu's book suggests that the wax model combination should be completed within two hours after completion. I think there is still some space for stress release after the wax model is assembled, so 2 hours is a time for the wax model to form. The cleaning operation should be as follows: before cleaning, blow off the wax shavings on the surface of the wax mold, then immerse the module in clean cleaning solution for a few seconds, and gently shake up and down to improve the cleaning effect. (Note that the time used here varies depending on the type of cleaning agent used, and cannot be generalized. Some take 3-4 seconds, while others take 8 seconds. This must be strictly followed according to the manufacturer's guidance or one's own practical experience, and cannot be ignored. Otherwise, it may cause poor cleaning of the casting surface or too rough the casting surface.) After the module is removed from the cleaning solution, if an organic solvent is used, it must be immediately blown away with compressed air and then dried; If a water-soluble detergent is used, it should be washed with water and then air dried after washing.

We often find that many factories often clean the surface layer before hanging it, without waiting for the cleaning solution to dry or simply blowing it with compressed air. This operation is actually not good. Some cleaning agent manufacturers claim that they can simply make shells without drying them after washing, which is also an irresponsible statement. Mixing organic solvents or tap water into the surface coating can cause the coating to solidify, which adds unnecessary trouble to the maintenance of the surface slurry. It is recommended that investment casting manufacturers take it seriously.

Speaking of maintenance, cleaning agents also require maintenance. Because cleaning agents are used to clean the wax shavings and parting agents on the surface of wax molds, over time these things will float on the surface of the cleaning agent and need to be cleaned regularly. Cleaning agents are not perpetual motion machines, and their cleaning ability may decrease over time. Therefore, when necessary, it is necessary to supplement the cleaning agent to avoid a decrease in cleaning effectiveness.

Another thing to note is that the temperature of the cleaning solution is generally between 22 ℃ and 25 ℃. If the temperature drops, it will seriously affect the effectiveness of the cleaning agent. A friend once had a very poor cleaning effect due to a decrease in the temperature of the cleaning tank. These are valuable experiences that are worth learning from. The following is the cleaning system designed by Mr. Yamaguya Yangshu, which is worth learning from, especially the ultrasonic assisted cleaning system.

Precision machining