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Lost wax casting

  • Author:LanKai
  • Source:Www.xy-global.com
  • Release on :2018-06-22
Lost wax casting
is one of the glass forming methods. Its main process is to heat the glass to a high temperature to make it fluid and flow into a preformed mold. Because the mold shell is prepared by removing the wax pattern after heating, it is called dewaxing casting.

Process
Dewax casting process flow is: mold design - open mold - wax injection (mold) - trim wax model (weld wax model) - wax tree species (- weighing) - shell model - shell Mold roasting - casting - vibration shell - sand treatment

1. Making product mold
Get the engineering part of the drawing and design the corresponding mold according to the drawings and design the gate. Then a series of processing of the aluminum material through a CNC machine tool, to create a mold.

2. Wax injection

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

When waxing, you should use your hands to clamp the mold in the splint (can be a plexiglass plate or wood board, aluminum plate, etc.), pay attention to the distribution of the fingers should make the pressure of the mold evenly; align the nozzle of the mold to the wax nozzle parallel Proceed with the top of the beetle and hold the hand behind the bees, move it gently with your foot and release immediately. Hold your hands for 1~2 seconds, place the mold for a moment, then open the plastic mold (if the mold is bottomed , you should first pull out the mold bottom) and remove the wax mold. Wax mold carefully checked after removal, if there is a serious lack of edges, broken feet and other issues, such wax models are waste. If there are some minor defects, wax pattern trimming should be performed.

3. Trimming the wax pattern

In general, wax models taken after wax injection will have more or less problems, such as flash, multiple edges, broken claws, visible trachoma, partial or overall structural deformation, small holes, and unclear lines , take the first edge and so on. For the flash edge, multi-edge, flower head is not clear, take the edge and other defects can be used to repair light with a surgical blade; for sand eyes, broken claws can be welded with wax welding repair; hole can not be used to penetrate the needle; for wax Deformation of the mold can be corrected in hot water at 40~50°C.


4. Welding tree group

After the wax pattern has been trimmed, wax trees need to be planted for further operations.

The kind of wax tree is to make the wax pattern in a certain order, and weld it on a wax stick in layers in the circumferential direction with a wax welder, so as to finally obtain a wax tree with a shape resembling a big tree, and then wax The tree is filled with gypsum and other processes. The basic requirement for wax trees is that the wax patterns must be arranged in an orderly manner. The key is that the wax patterns cannot be contacted with each other. This can not only maintain a certain gap, but also can weld the wax pattern to the wax tree as much as possible. On the wax tree, it is necessary to try to "seed" the maximum number of wax patterns, which has met the needs of mass production.

The wax tree must be "planted" on a round rubber chassis. The diameter of this rubber chassis is matched with the inner diameter of the stainless steel cylinder. The diameter of the general rubber chassis is 3 inches, 3 inches and 4 inches. The center of the chassis has a protruding circular recess, the diameter of the recess equal to the diameter of the wax stick of the wax tree. The first step in the "speculative wax tree" is to pour some wax liquid from the wax stick head and insert it into the recessed hole of the chassis while hot, so that the wax stick and the recessed hole can be combined firmly. In the second step, the wax pattern is welded layer by layer on the wax stick, starting from the bottom of the wax stick (from the bottom up) or starting from the wax stick head (from the top down). If the technique of "planting trees" is more skillful, the two methods do not differ much in operation; however, the method of starting from the head of the wax stick (from the top to the bottom) is generally used because the greatest advantage of this method is that it can prevent Melted wax droplets fall on the welded wax mold to avoid unnecessary rework due to wax droplets.

The wax tree operation process should pay attention to the following issues.

1) There is generally an angle of 45° between the wax mold water channel and the wax bar of the wax tree, that is, the direction of the wax mold is inclined upward. Only in this way can the gold water be smoothly injected into the plaster mold. This angle can be adjusted according to the size and complexity of the wax pattern. The small and complex wax pattern can reduce the angle; on the contrary, the larger wax pattern can increase the angle.

2) Before the wax tree is planted, the rubber chassis should be weighed first. After the wax tree is completed, it is weighed again. Subtract the results of these two weighings to obtain the weight of the wax tree. The weight of the wax tree is converted into the weight of the metal by the ratio of the density of the wax and the cast metal, and it can be estimated how much metal is needed for casting.

3) When the wax tree is finished, it must be checked whether the wax pattern is welded. If there is no welding, it is easy to cause the wax mold to fall off during plastering, which will affect the casting process. Finally, you should check if there is enough space between the wax molds. If the wax molds stick together, they should be separated. If the wax tree drops on the wax, it should be repaired with a blade.V. Shell type

Shell mold making
Wax baking is an important process to ensure that casting is performed normally. In general, the 18K gold mold baking time is 6~12 hours, and the platinum mold baking time is 12~20 hours. The role of baking are: dewaxing, drying and casting insulation. Taking 18K gold baking as an example, dewaxing temperature is 0~350°C, holding time is 2 hours; drying temperature is 350~700°C, holding time is 2~3 hours; casting holding temperature is 600~500°C, holding time is 1~ 2 hours.

Finally, the molten steel is cast into the finished shell


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