In today's market conditions where the design of the bottom pattern is becoming more and more complicated, the development of the traditional counter mold is more difficult, and only the replacement of precision casting is expected. With a small variety and a shortened market life cycle, the development level of the bottom mold is related to the competitiveness of the own brand or its own brand or ODM manufacturer. Since the conventional bottom mold manufacturing method is directly processed by a single copper plate (or aluminum plate), it can be said to be costly and time consuming for a high complexity substrate. Therefore, this series focuses on precision casting technology and proposes copper mold casting test results for reference.
Ceramic shell casting
For the current sample casting industry, most of them are divided into Xiao casting method and plaster casting method. The former is used in copper mold and the latter is used in aluminum mold. These are relatively common practices. The following are elaborated separately:
Xiao's casting method
Introduction
This method is one of the methods of investment casting, which is widely used and has a long history. However, the method popularized earlier in the country is the lost wax casting method, which is difficult to apply to the casting of large workpieces. Therefore, for the dewaxing foundry, every large-scale work is at a loss, and both It can be applied to casting of non-cast metal, cast metal and superalloy. In terms of quality such as precision and surface roughness: both are the same. The difference is that the shows proces casting can be applied to large castings or medium castings (such as shoe molds, etc.). The ceramic shell mold used in Xiao's casting method is made up of refractory sand and ethyl silicate 40 hydrolyzate. After ignition and combustion, the surface produces tiny uniform cracks. These cracks will not affect the surface of the casting, but will help. Prevent the mold from shrinking and deforming. The formation of these uniform and minute cracks is controlled by the refractory sand particle size distribution, hydrolyzate, hardener and baking technology.
The production process of Xiao's ceramic mold is as follows:
Process introduction
Prototype preparation
According to the blueprint or sample production, and consider the shrinkage rate, reserve processing and other factors to complete the prototype, and according to this prototype to make a soft mold for the use of ceramic mold.
Hydrolysis liquid preparation
The hydrolyzate is a solution of water, hydrochloric acid, alcohol and ethyl silicate 40, which are sequentially added and thoroughly stirred to obtain a clear and transparent solution containing colloidal silica, which is called a hydrolyzate. The hydrolyzate which has been prepared in general should be used after one day of standing, so that it is better to increase its maturity. It is best to use it within one week to avoid aging and seriously affect the quality of subsequent ceramic mold making. The proportion of hydrolyzate blending is as follows:
Process description
A. Gypsum mixing procedure Pour the water into the gypsum powder for about 30 seconds, use the mixing plate to stir to raise the air into the mud, and generate bubbles, and lift the mixing plate to the surface to make the bubbles disappear or the small bubbles become small bubbles. This mixing operation is completed, and then poured into the mold, and the mold can be released in about 30 minutes.
B. Precautions when mixing gypsum
The purpose of using a stir plate is to achieve a smooth surface and a good air chamber structure, and a more air chamber and a more tidy air chamber structure. If a uniform distribution of porosity, low expansion, gypsum, water, air, etc. is obtained, good strength can be achieved, and in order to obtain a better effect, the use of warm water is a preferred method.
Drying operation
The plaster mold method uses water to make the powdered gypsum form a solution, and the water has a bad influence during the casting process, so the drying operation is necessary, that is, the water must be removed before the casting operation, and of course the method of removing the water is very More, here we use the oven to slowly bake under 300 degrees to achieve a drying effect.
Metal casting operation
The casting temperature is preferably between 600 ° C and 700 ° C (for aluminum alloys). Of course, it is inevitable that it will change in different occasions. After the casting is completed, it is necessary to wait for solidification before moving better. Shoe mold foundries use a fixed position, so there should be no such concerns.
Melting operation
The general process of smelting is as follows:
Test methods and results
Experimental summary
The sole mold is characterized by insufficiency of precision and complexity. This feature is very suitable for the production of precision casting, especially to meet the requirements of surface roughness and the reproducibility of the original pattern, which makes the application of precision casting technology more necessary. . Precision casting technology has a long history, and there are countless product technologies applied. Only in the field of sole molds, has it flourished in recent years. Due to the increasingly fierce competition in a small number of different markets, the design of the bottom is more complicated. Factors such as shortened delivery time and other factors make the use of traditional methods to make the sole mold feel pressure, so the precision casting molding method will evolve into a necessary trend.
Second, the purpose of the experiment
Although the precision casting method has many advantages, when it is actually applied to the sole mold, it will produce problems that have never happened or are unexpected. These common problems are summarized as follows:
Control of deformation amount; control of shrinkage rate; reproducibility of pattern;
The following is an experiment for these four common problems and proposes a reference countermeasure.
Third, the experimental parameter setting
Mold size
length Width Thickness
A40035060
B40035030
C40035020
Mold type
A. Monolithic - the method currently used in domestic die casting.
B. Two pieces - including casting of the parting surface.
C. The ginseng - including the casting of the parting surface.
Mold material - SS41 (low carbon copper) or WCB
Casting temperature - 1640 ° C
Sintering of shell mold
No. Sintering temperature (°C) holding time (minutes)
125040
250040
375040
490040
Table 1 shell mold sample bending strength test record
Sample
Numbering
Section
Length, width and height
(CM)(CM)(CM)
Maximum load (kg) maximum flexural strength (kgf/cm) breaking rate% Remarks
A56270.583.5 is not available
B5627.50.633.7-
C56280.674 is still available
D56290.754.5 unstable
E5628.50.714.2 good reliability
F5628.30.694.1 good reliability
G5628.40.74.2 good reliability
H5628.20.84.3 good reliability
I562914.2 good reliability
Excellent J5621214.5
Table 2 Deformation after casting
The straightness of the finished product of the sample position (the error value of the deformation and the prototype)
Bottom flower 1mm; template 1.3mm
Bottom flower 1mm; real model 1.3mm; hollow template 1.2mm
Bottom flower 1.0mm; mold core 1.1mm; real model 1.4mm; hollow template 1.3mm
Table 3 shrinkage rate after casting
Sample prototype size casting finished product size size error %
A. 2842820.7; 5049.60.8; 150148.50.99
B. 284281.50.8; 5049.70.6; 1501490.7;
C. 2842820.7; 5049.70.6; 1501490.7
Fourth, the actual test and results
<The bending strength of the shell mold (Table 1)
(The amount of deformation after casting (Table 2)
<Shrinkage rate after casting (Table 3)
<Reproduction degree after casting (Table 4)
Table 4 after the casting
Sample casting condition review
A-1 copper bead granule
B-2 difficulty in clearing sand
C-1 black skin removal difficulty
D-1 acute angle is not complete
E-2 etched hole
F-3 falling sand
G-1 surface is clear
H-2 has a clear surface and no black skin
I-1 has a clear surface, no black skin, no etched holes, easy sand cleaning, no particles
J-3 has no black skin, no etched holes, no particles, sand sand is easy, the surface is clear, and the deep groove is sharp and sharp.
※The sample selection is more representative.
. Parting surface and mold review after casting (Table 5)
Table 5 Review of the parting surface after casting
Sample parting surface and clamping surface review
A"The parting surface and the mold part are processed and combined.
. Parting surface is flattened
. Use thicker formwork, slower heat transfer, less workability, lower outsole production efficiency
B&C "Molded face once completed
. Mould finished once
. The machine is finished once
. Parting surface varies with mold requirements
. Restore the outsole production efficiency of traditional molds
V. Brief analysis of the situation
The four major problems raised in this report are the more common situations. In fact, there are many emergencies; such as oxidation, shrinkage, etc. These emergencies involve the specialized field of foundry technology and will not be detailed here. Firstly, the control of the deformation amount is discussed. When the temperature of the molten iron is lowered from 1600 °C to room temperature, the deformation is inevitable, but it is shown by experience; these deformations will not affect the usability of the shoe mold, and the important problem is Tao. Formulation and baking and soft mold applications. Secondly, the control of shrinkage rate is related to the application of raw materials and the quality management skills of the whole process. The third is the reproducibility of the pattern. To achieve good reproducibility, special requirements are required for the casting technique. Others of course have some points to be noted, such as shell mold, composition, and so on.
in conclusion
According to the current industry analysis, the sole mold process can be professionally divided, that is, the casting project can be operated independently by the foundry, but in the future, if the mold face is included in the important role of the sole mold process, the characteristics of the professional division of labor will be replaced. Over the past few decades, domestic companies have suddenly slipped down at a hot high. This is also the result of vicious competition. Individuals predict that within five years, the sole mold will face the "filter" filter test, when the technology and physical fitness are not good. Will face the fate of being eliminated.
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