Products Of Lost wax castings

Definition: Molding material is made of molten material (usually a low melting point material such as wax material) and made into a mold. Then, the coating (refractory) on the surface of the module is heated and cured. After the module is heated and melted The mold material to form a hollow shell, after high temperature sintering after pouring metal liquid, after cleaning to get castings. As the molten material is usually wax-based material, so also known as "lost wax casting."


  1. 1. The casting has high dimensional accuracy (CT4-CT7); low surface roughness (Ra1.6-6.3μm), which reduces the cutting allowance of castings and even achieves near net casting.
  2. 2. Can produce complex shape of thin-walled castings.
  3. 3. Alloy material is not restricted. Steel, copper, aluminum, titanium, magnesium and so on. High melting point nickel-based superalloy; zinc, tin and other low melting point metal.
  4. 4. Investment casting there are some limitations.

The process flow of wax loss casting is: pressing the mold - open mold - injection wax (mold) - dressing wax mold (wax wax mold) - kind of wax tree (- weighing) - filling granules - Gypsum Vacuum - Gypsum Natural Solidification - Baking Gypsum - Melting, Casting - Gypsum - Flushing, Pickling, Cleaning (Weighing) - Shearing (- Rolling).

One . Press the mold

The glue used to make the mold is a rubber sheet with both sides of the gum. General use of imported film to Castaldo card for more. One of the relatively low prices, due to the composition of natural rubber containing less, slightly higher hardness after vulcanization, but the die time is shorter, suitable for more experienced mold division to operate; another price slightly higher , Contains more natural rubber, soft texture, toughness, suitable for more complex pattern, contour size is small, convex and concave silver plate stamping, in the removal of wax mold is not easy to break wax mold. Health film preservation must pay attention to control its storage temperature, below 20 ℃ can generally save a year, at 0 ~ 5 ℃ storage time can reach 2 to 3 years. In addition, there is also a pre-made a series of size and thickness of the rubber mold, the wall of the concave and convex connecting feet, the use of more convenient.

Two . Open mold

Open plastic mold in the jewelry factory is a demanding technology, because the plastic mold directly affect the wax mold and the quality of metal blanks, but also a direct impact on the life of plastic mold. Technology master mold out of the mold, after the wax is basically no deformation, fracture, cloak of the phenomenon, basically do not need to repair wax, wax welding, can save a lot of repair work hours, get a higher production efficiency. The tool used to open the mold is relatively simple, there are scalpels and blades, tweezers, scissors, pointed nose pliers and so on. Note that beginners must use a new blade when using a scalpel, but it is not easy to scratch your fingers. During the cutting process to ensure that the blade and the rubber film between the mold lubrication, you can dip in the blade of water or detergent (but do not dip in oil, because the oil will make the mold hardened, brittle). Plastic mold is usually used four-foot positioning method, that is, out of the plastic mold has four feet each other fixed, four feet between the part of the use of linear cutting, but also the use of curve cutting.

Three . Note wax

After the glue mold is opened, the waxing operation can be carried out. Note wax operation should pay attention to the wax temperature, pressure and pressure clamping and other factors.

The wax used to make the wax mold is generally blue model paraffin wax, the melting temperature is about 60 ℃, the wax temperature is about 65 ℃. There are some other colors of paraffin, the nature is slightly different. Wax temperature and injection pressure is determined by the wax machine. The type of wax machine is usually wind and vacuum type two. The two wax injection machine waxing principle is basically similar, that is, the use of air pressure will melt the wax into the mold. The difference between the two is that the vacuum injection wax machine can first vacuum mold, in the mold to the wax; and wind pressure injection machine can only directly to the mold injection wax. So the operation is usually easy to grasp the vacuum-type wax machine, and the wind pressure wax injection machine will need to have some experience.

Four . Adjust the wax mold

In general, wax wax removed after the wax will be more or less there are some problems, such as flash, multiple edges, broken claws, visible eye trachoma, part or the overall structure of deformation, small holes unreasonable, flower head lines are not clear , Flower head and so on. For the flash, the broken edge can be welded with a welding machine; Modification of the mold can be corrected in hot water at 40 to 50 ° C. In addition, for the different ring of hand-held, if you wait until the mold and then change the finger ring, no doubt both labor and food. So the general production enterprises are in the wax mold when the direct change to the ring. Change the use of welding wax welding machine is very convenient, after welding with a blade to repair the weld can be.

Five . kinds of wax trees

Wax pattern after finishing, the need for wax tree, in order to carry out further operations.

The kind of wax tree is to produce a good wax mold in accordance with a certain order, with a wax welding machine in the circumferential direction of the sub-layer welding in a wax stick, so that the final shape of a tree similar to the tree, Tree for plaster and other processes. The basic requirement of the wax tree is that the wax pattern should be arranged in order, the key is the wax mold can not contact, both to maintain a certain gap, but also as much as possible wax pattern welding in the wax tree, that is, Wax tree to try to "species" on the maximum number of wax mold, has to meet the needs of mass production. The kind of wax tree must be "kind" on a circular rubber chassis. The diameter of this rubber chassis is matched with the inner diameter of the stainless steel cylinder. General rubber chassis diameter of 3 inches, 3 inches and 4 inches. The center of the chassis has a raised round concave hole, the diameter of the hole and the wax tree wax bar diameter quite. "The first kind of wax tree" is the wax stick head dipped in some melted wax solution, hot plug into the concave hole in the chassis, so that the combination of wax sticks and concave hole firmly. The second step, layer by layer wax welding on the wax bar, you can start from the bottom of the wax bar (from the bottom up), can also start from the wax head (from top to bottom). If the technique of "planting trees" is relatively skilled, the two methods are not very different in operation; however, there are many ways to start from the head of the wax bar (from top to bottom), since the greatest advantage of this method is that The melted wax drops onto the welded wax mold, which avoids unwanted rework caused by dripping wax.

Six . plaster, vacuum

Put the wax tree with the chassis together with stainless steel tube (steel bell), wrapped in steel bells outside the single-sided adhesive tape (adhesive tape should be higher than the bell on the 20cm or so).

Seven . Baking gypsum

Gypsum mold baking is an important process to ensure the normal casting. In general, 18K gold casting baking time of 6 to 12 hours, platinum casting baking time of 12 to 20 hours. Baking the main role are: dewaxing, drying and casting insulation. The drying temperature is 350 ~ 700 ℃, the holding time is 2 ~ 3 hours; the casting temperature is 600 ~ 500 ℃, the holding time is 1 ~ 2 hours.