Wax molding is the first step of precision casting.

2020-08-13 16:31:00 1489

Wax mold making is the first step of the process of precision casting, and the quality control of wax mold affects a series of subsequent quality problems. Here, we summarized some common shortcomings of simple mistakes for the appearance and specifications of wax parts, put forward some improvement plans, and pointed out that it is necessary for everyone in the wax mold workshop to follow the quality management principles, laying a good foundation for wax quality assurance. In view of the above, let's talk about the following points:

1、 In order to stabilize the function of wax materials in the wax production workshop, in view of the shortcomings of the original high-temperature dehydration process, the static water drainage and hydraulic press dehydration process are changed. The impurities and ash content of wax materials are greatly reduced, and the quality is guaranteed.

Wax molding is the first step of precision casting.

2、 Confess whether the equipment is in normal operation, repair it in time and conduct annual inspection every year

A: Ensure the temperature meter and pressure gauge of wax injector are normal

B: Hydraulic and air compressors operate normally

C: Regular planning for temperature requirements of chiller, normal insulation of wax conveying pipe and wax cylinder

In a word, ensure that the parameters of a wax injection machine are standardized. When other equipment has problems, this machine can be used for comparison and correction

3、 Quality Control of Wax Parts

3.1 Wax appearance shall be free from the following defects:

A) Wax flow pattern, rough appearance

B) Wax has cracks

C) Bubble, wax

D) Large flash, especially the local part of parting line (die wear)

E) The ceramic core cracks in the wax mold or the water-soluble core remains

F) Sag (mold and wax temperature is too high, pressure is short, wax inlet orientation is wrong, maybe too small, no quench block or cold wax is put)

G) Deformation (generally caused by short wax injection time or incorrect mold taking method)

H) Not full

1) Poor mold

3.2 Specification for control wax parts

In order to ensure the specification tolerance of the casting, it is necessary to conduct wax specification control, provided that the temperature of the wax mold is completely cooled to the room temperature required by the wax.

Wax molding is the first step of precision casting.

A) The biggest influence of specification changes is the shrinkage of wax. Grasping the shortening rate of wax is the key to obtain the correct mold specification. It is necessary to grasp the shortening rate of wax materials correctly at any time. To measure the shortening rate of wax, under the same specification wax injection process parameters, measure the wax sample data with stable specifications, and calculate according to the formula:

Wax molding is the first step of precision casting.

B) Generally, some casting specifications need to be carefully inspected and controlled on wax specification. For some large batches of wax, an electronic scale with an accuracy of 0.01 g can be used for weighing. If it exceeds the upper and lower planning of the rules, then a random inspection and recheck with vernier caliper can be carried out. In this way, full inspection with vernier caliper can be omitted. The following conditions generally need to be controlled on wax specification:

1. Castings have severe requirements for precision tolerance, and are generally fully inspected with caliper or vernier caliper

2. Important specifications related to parting surface (aluminum die worn or parting surface dirty)

3. Requirements for form and position tolerance, such as flatness, perpendicularity, etc

4. Products with simple dents, such as products with unequal structure thickness

5. Special products, such as U-shaped products

C) The biggest reason why wax specification is not firm

1. High wax temperature

2. Short wax injection time

3. The pressure is too low

4. The shortening rate of wax is large and unstable

5. The wax injection port has small flow channel or wrong orientation

6. No cold wax block or chilling block is used in case of depression

7. The U-shaped parts can also be processed with rebar

Wax molding is the first step of precision casting.

4、 Quality Control of Wax Components

4.1 Simple Disadvantages of Group Tree

A) The die head is not matched with the wax part, and the strength of the die head is short when it is fed, which is prone to shrinkage porosity, shrinkage cavity, cracking and steel leakage

B) The wax parts are too tight or too loose, the distance is unreasonable and inappropriate, and shrinkage cavity, burr and puncture are easy to occur

C) There is weld between wax part and die head, which is easy to cause defects of sand inclusion and shell casting

D) There are wax drops on the wax piece (which occurs during tree formation)

E) The die head has pinholes or floor wax

F) The waxing wax is not repaired and there are gaps

G) With flash

5、 Under the supervision of the quality assurance department, ensure that the wax mold workshop strictly implements the relevant process principle documents and follows the rules and principles of the workshop

5.1 Ensure the accuracy of wax type process flow

A) During the sample preparation in the wax molding workshop, ensure that the wax injection parameters are suitable and correct, and the wax mold appearance and specification are within the control planning

B) Record and seal the wax pattern appearance and standard control, and acknowledge the acceptable upper and lower limit plates and planning

C) Ensure the correctness of the process sheet of wax mold workshop, including wax injection process and tree forming process. Once admitted, it will not be modified. If there is any change, the project will be modified according to the ISO9000 quality system.

5.2 Contents of wax injection card

1. Wax injection time

2. Pressure maintaining time

3. Wax injection pressure

4. Wax making temperature

5. Mold number, product type, structure diagram and photos of disordered molds, mold taking sequence, etc

6. Indicate whether cold wax block and chilling block are used

7. Some special dewaxing agents or mold taking methods

8. Appearance requirements

9. Minimum Acceptable Disadvantages

10. Severe control specifications to be tested (indicated by testing tools)

11. Indicate whether to check whether the sand core is cracked (if there is X-ray machine condition)

12. Precautions for penetrating sand core and equipment for avoiding sand core falling

5.3 Contents that can be included in the tree card

1. Product type, corresponding die type and quantity of wax assembly

2. One or more corresponding photos of different viewpoints of the assembled tree

3. If it is a combination die head, please indicate the list, photos, quantity and combination diagram of each die head

4. Indicate the production rate and identification of products

6、 Summary

Although the process of wax mold workshop is simple, there are many problems that affect the quality of wax mold, involving a wide range of contents, such as the quality of mold wax, the stability of process, etc., which requires every operator and manager to carefully follow and implement. Only by doing each step well, can we make perfect precision castings.


Qingdao Xinnuoke Holdings Group limited company.

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