Research on Precision Casting Technology of Sole Mold

In today's market situation where the design of the sample is becoming more and more complex, the development of traditional counter models is even more difficult, and only the replacement of Precision Casting is hoped for. With a small amount of diversity and a shortened market life cycle, the ability of the bottom mold development is related to the competitiveness of its own brand or its own brand or ODM manufacturer. Since the conventional bottom mold manufacturing method is directly processed with a whole copper plate (or aluminum plate), it can be said to be costly and time-consuming for a high-complexity bottom sample. Therefore, this series is focused on precision casting technology and puts copper mold casting test results for reference.

Tao shell mold casting

For today's foundry foundry builders, most of them are classified as Shaw Casting and Plaster Casting. The former is used in copper molds and the latter in aluminum molds. These are common practices. The following are separately elaborated:

Shaw Casting

Introduction

This method is one of the investment casting methods. It is widely used and has a long history. However, the earliest generalization method in the country is lost wax casting. This method is difficult to apply to the casting of large-sized workpieces. Therefore, for the dewaxing foundry, every time a large-scale job is encountered, no solution is available, and both are Applicable to the casting of non-cast metal, cast metal and superalloy. In terms of precision, surface roughness, etc.: both are the same. The difference is that shows proces casting can be applied to large or medium-sized castings (such as shoe molds, etc.). The shell mold used in Shaw's casting method is made of fire-resistant sand and silicate 40 hydrolyzate. After ignition and combustion, the surface generates small and even cracks. These cracks do not affect the surface of the casting. Instead, they help. Prevent mold shrinkage and deformation. The formation of these even and minor cracks is controlled by the refractory sand particle size distribution, hydrolyzate, hardener and baking technology.

Xiao Shi pottery production process is as follows:

Process introduction

Preparation of the prototype

According to the blueprint or sample production, and consider the shrinkage rate, processing and other factors to complete the prototype, and then make a soft mold prototype for use in ceramic molds.

Preparation of hydrolyzate

The hydrolyzed solution is water, hydrochloric acid, alcohol and ethyl silicate 40, which are added in sequence, and after thorough stirring, a clear and transparent solution containing silicic acid colloid is called hydrolyzed solution. The hydrolysate that is generally formulated must be used after standing for one day. It is better to increase the maturity of the hydrolysate. It is best used within one week to avoid aging and seriously affect the quality of subsequent mold making. The proportion of hydrolyzate is as follows:

Process description

A. The gypsum mixing program soaks the water in gypsum powder for approximately thirty seconds, stirs it with a mixing tray and raises the air into the slurry, creating bubbles, and lifting the mixing disk to the surface causes the bubbles to disappear or the large bubbles to become smaller. This mixing operation is completed and it is poured into the mold and released in approximately 30 minutes.

B. Precautions when mixing plaster

The purpose of using a stir plate is to achieve a smooth surface and a good air chamber structure, and it is a more air chamber and a more neat air chamber structure. If the porous, low-expansion, gypsum, water, air, etc. are uniformly distributed, good strength can be achieved, and in order to obtain better results, the use of warm water is a better method.

Drying operation

The plaster mold method uses water to make the powdery gypsum into a solution, and the moisture will have an adverse effect during the casting process. Therefore, the drying operation is necessary, that is, the water must be removed before the casting operation. Of course, the water removal method is very More, here we slowly bake in an oven under 300 degrees to achieve a drying effect.

Metal casting operations

Casting temperature is about 600 °C ~ 700 °C is appropriate (for aluminum alloys), of course, will change in different occasions is inevitable, after the completion of the casting, to wait for solidification, before moving better, generally Shoe mold foundry has adopted a fixed position method, so this should not be a concern.

Melting operation

The general process of smelting is as follows:

Test methods and results

Experiment summary

The shoe sole mold is characterized by precision and intricate product features. This feature is very suitable for the production of precision castings, in particular to meet the requirements of surface roughness and the reproducibility of the original pattern, which makes the application of precision casting technology more necessary. . The precision casting technology has a long history, and the number of applied product technologies is countless. It has only been used in the field of sole molds. It has only flourished in recent years. Due to the fierce competition in a small number of different markets, the design of the sample is becoming increasingly complex. The factors such as the shorter delivery time and other factors make the pressure on the shoe sole molds produced by traditional methods, so the precision casting 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 a shoe sole mold, problems that have not occurred or unexpectedly occur will arise. These common problems are summarized as follows:

Deformation control; shrinkage control; pattern reproduction; mold surface production.

The following is an experiment for these four common problems, and propose reference measures.

Third, the experimental parameters set

Mold size

length Width Thickness

A40035060

B40035030

C40035020

Mold type

A. Monolithic - the method used in the current domestic bottom mold casting.

B. Two-piece - including the mold surface casting.

C. Specimen - including the mold surface casting.

Mold material - SS41 (low carbon copper) or WCB

Casting temperature - 1640 °C

Shell mold sintering

No. Sintering temperature (°C) Holding time (minutes)

125040

250040

375040

490040

Table 1 Test record of flexural strength test of shell mold specimen

Specimen

Numbering

Section

Height and width

(CM)(CM)(CM)

Maximum load (kg) Maximum bending strength (kgf/cm) Break rate% Remarks

A56270.583.5 not available

B5627.50.633.7-

C56280.674 still available

D56290.754.5 is not stable

E5628.50.714.2 Good Reliability

F5628.30.694.1 reliability

G5628.40.74.2 has good reliability

H5628.20.84.3 has good reliability

I562914.2 has good reliability

J5621214.5 Excellent

Table 2 The amount of deformation after casting

The trueness of the casting position of the sample position (distortion value of deformation and prototype)

Bottom flower 1mm; Template 1.3mm

Bottom flower 1mm; Real template 1.3mm; Hollow template 1.2mm

Bottom flower 1.0mm; mold kernel 1.1mm; real template 1.4mm; hollow template 1.3mm

Table 3 Shrinkage after casting

Sample prototype size Casting 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)

(Deformation after casting (Table 2)

< Shrinkage after casting (Table 3)

Table 4 Pattern Reproduction After Casting

Sample cast product condition review

A-1 copper beads

B-2 difficulty in sand removal

C-1 Black skin is difficult to remove

D-1 is not complete

E-2 hole

F-3 falling sand

G-1 surface is clear

H-2 surface is clear, no black skin

I-1 surface is clear, no black skin, no holes, easy sand, no particles

J-3 no black skin, no holes, no particles, easy sand, clear surface, clear sharp corners

※ More representative sample number after sample selection

. Molded surface and mold clamping review (Table 5)

Table 5: Review of mold surface after casting

Sample split surface and mold surface review

A "partial die surface and die part application processing combination

. Split surface is flat

. Use of thicker plates, slower heat transfer, poorer workability, and lower production efficiency

B&C "Partitioning surface completed once

. Mold finishes once

. Machine completed once

. Parting surface changes with mold requirements

. Restore the outmoded production efficiency of traditional moulds

V. Analysis of the situation

The four major issues raised in this report are more common, and in fact there are many unexpected situations; for example, oxidation, shrinkage, etc. These emergencies involve the specialized field of casting technology and will not be elaborated here. First of all, the control of the deformation amount is discussed. When the temperature of molten iron drops from 1600°C to room temperature, the deformation is unavoidable, but according to experience, these deformations will not affect the usability of the shoe mold. The important problem is that Mold recipes and baking and soft mold applications. Secondly, the control of shrinkage rate is related to the application of raw materials and quality management techniques throughout the process. The third is the degree of reproduction of the pattern. To achieve a good degree of reproducibility, special requirements are required for the casting technique. Of course, there are some other points that need attention, such as shell molds, ingredients, etc.

in conclusion

According to the analysis of the current industry, the sole mold manufacturing process can be divided into professional divisions, that is, the casting project can be independently operated by the foundry, but in the future if the mold surface is included in the important role of the sole mold manufacturing process, the characteristics of the professional division of labor will be replaced. In the past decades, domestic companies have often slipped off when they were at a hot spot. This is also the result of vicious competition. Individuals predict that in the next five years, sole molds will face the challenge of “filter” filtration, which will result in poor technology and physical fitness. Will face the fate of being eliminated.