Influence of Lost Foram Equipment on Lost Foram Process


1 The relationship between the process and equipment of the lost mode

As we all know, the lost pattern equipment appears after the development of the lost pattern process to a certain stage. We should understand that the mission of the lost pattern equipment is to ensure the smooth implementation of the lost pattern process, and to serve the smooth development of the lost pattern process. In other words, if there is no process to support, the equipment is just a pile of scrap copper and iron, which is meaningless. Therefore, only with a deep understanding of the lost model process and even years of commitment to the research and development and expansion of the lost model process can such enterprises produce equipment that is truly suitable for the lost model process. In a real sense, the concept of "lost model equipment is to ensure the lost model process" will not be reduced to an "equipment factory" that only makes equipment for the sake of business amount and efficiency ". This paper mainly focuses on the equipment that plays a vital role in the process of lost-vanity mold process and makes a brief analysis of the equipment that makes a great contribution to the implementation of the lost-vanity mold process. The purpose is to let the practitioners of the lost vanishing mold industry fully understand the important role of the lost vanishing mold equipment in the process of the lost vanishing mold process, and have a certain understanding of the performance and characteristics of these equipment. In this paper, the process of lost vanishing mold is divided into three modules: white mold quality, pouring process and sand treatment, mainly from these three directions. At present, the quality of lost vanishing mold equipment on the market is uneven, in order to unify the equipment listed in this article are all produced by Hebei Ruiou Intelligent Equipment Co., Ltd.

2 white models

2.1 Advance Process Requirements and Process Flow

2.1.1 Advance machine process requirements

As the first step of LFC method, pre-forming is the beginning of the whole lost foam process, which directly affects the quality and efficiency of the whole process. Now widely used in the field of lost foam production raw materials are mainly: EPS, STMMA. The process requirements are:

(1) higher production efficiency;

(2) controllable bead density;

(3) Uniform material, no sub-material;

(4) after the hair bead particle size to meet the use requirements.

2.1.2 Advance machine process flow

The process flow of the pre-development machine is as follows: original bead selection → bead pre-expansion density control → bead pre-expansion → bead aging. Reasonable bead size and density have a crucial influence on the surface quality and strength of the pattern, which in turn affects the quality of the casting. The selection of the pre-machine model and the setting of process parameters have a profound impact on the pre-foaming of the original beads and the subsequent process to the entire lost foam process. See Table 2-1 for the types and characteristics of the pre-generator. Figure 2-1 shows the electric steam pre-generator ROYF-Ⅰ EPS and STMMA dual-use.

Table 2-1 Types and Characteristics of Advance Machine

Figure2-1 Ruiou electric steam pre-generatorROYF-Ⅰ EPS,STMMAdual use

2.2 white mold molding quality

2.2.1 white mold process requirements and molding machine process

After the original beads are pre-foamed (once foamed) by the pre-machine to be qualified beads, the final white mold model can be formed by secondary foaming through the molding machine. In order to meet the process requirements, the white mold model should have the following conditions:

(1) Smooth and flat surface quality (without material breakage and insufficient molding);

(2) reasonable and accurate contour size;

(3) to meet the strength of the process.

molding machine process:

Process flow of molding machine: mold clamping → preheating → feeding → solid mold heating → moving mold heating → hot pressing → water cooling → vacuum cooling → demoulding. The function of the molding machine is to produce a qualified white mold model. The quality of the molding directly affects the quality of the white mold model, and then affects the quality of the casting, which is related to the success or failure of the entire lost foam process. Each process is essential and is designed to produce a white mold that meets the process requirements. Unreasonable molding process will produce defective products of the model. Figure 2-2 shows the defective products and good products of the well circle produced by Ruiou Company for Morocco.

 

Fig. 2-2 Reo's Production of Bad and Good Products in Moroccan Well Circle

At present, there are many kinds of molding machines. We take the hydraulic automatic (semi-automatic) molding machine produced by Hebei Ruiou Intelligent Equipment Co., Ltd. as an example for a brief explanation. The molding machine independently developed by the company adopts PLC programmable controller and touch screen, which can realize semi-automatic and fully automated production of the molding machine. Because the molding machine adopts PLC programmable controller, its process parameters can be written into the PLC controller through the touch screen, which can meet the production of different products for different molds. The parameters of the Swiss ROCX-I molding machine are shown in Table 2-2. Figure 2-3 is a ROCX-I hydraulic full-automatic molding machine produced by Reo.

Table 2-2 Parameters of RYO Hydraulic Forming Machine

 

Figure 2-3 ROCX-I Hydraulic Fully Automatic Molding Machine Producing by Rio Company

2.3 model drying quality requirements

2.3.1 Process requirements of drying equipment group

The role of the drying equipment group is to dry the white mold single model and the model cluster that is brushed after group bonding in the whole process, remove the moisture contained in it, and finally make the model have a certain strength, and can meet the requirements of the buried box and pouring process. Moisture sources are mainly in several aspects:(1) pre-molding with moisture;(2) water-based paint containing moisture;(3) after drying is not timely pouring moisture. From this we can derive the process characteristics that the drying equipment group should have, as shown in Table 2-3.

Table 2-3 Process Characteristics of Drying Equipment Group

 

 

2.3.2 Basic configuration and technical requirements for drying room

A complete white area workshop has many levels of drying rooms, but its configuration is similar. Here we take the drying room configuration of white mold workshop of Ruiou Company as an example. Different types of drying rooms have different drying technical requirements, which can meet the drying of different models.

The heating configuration, classification and technical requirements of the drying room are shown in Table 2-4, Table 2-5 and Table 2-6 respectively.

Table 2-4 Basic configuration of drying room

 

Table 2-5 Classification of drying room

 

Table 2-6 Technical Requirements for Drying

 

Different drying rooms have different drying technical requirements. Do not mix the models when placing them so as not to cause incomplete drying or damage to the models. Figure 2-4 shows the drying room of the production workshop of Rio and the white mold it is drying.

There is a jargon for lost foam: "success is also white mold, failure is also white mold". White mold is the soul of the whole lost foam casting process. The quality of white mold is related to the success or failure of the whole process, so it is very necessary to control the quality of white mold.

 

Figure 2-4 White Mold Model and One-time Brush Model Drying Room of Rio Company

3 Pouring

Pouring is the process of pouring qualified molten iron into the casting mold and cooling forming. This process includes melting, box burying, vibration, negative pressure and pouring. Every process needs to be strictly controlled.

3.1 smelting

We say that the quality of the white mold is the soul of the whole process, then smelting is the soul of the pouring process. The role of smelting is to use pig iron, scrap steel, furnace material and other auxiliary materials to melt them into qualified molten iron with a certain temperature and chemical composition. See Table 3-1 for the main points of smelting control.

Table 3-1 Smelting Control Points

 

3.2 buried box

3.2.1 Process requirements for sand box

The structure of the sand box used in LFC method directly determines the formation and distribution of the negative pressure field in the sand box. However, there are many misconceptions that it is good to pump air inside the sand box. As for how to pump and how much to pump, it is irrelevant, as long as the box does not collapse. So now there are all kinds of sand boxes, which seem to be able to pour out castings, but the impact is very different. A sand box that meets the process requirements should have the following points:

(1) Reasonable outline and structure size (according to casting and process requirements);

(2) sufficient welding strength;

(3) Air chambers with uniform arrangement and reasonable distribution.

3.2.2 Process requirements for air chamber distribution in the sand box

From the perspective of the lost foam process, the ideal state is that the negative pressure field formed in the sand box is a stable and uniform force field, and the formation of the negative pressure field depends on the distribution of the sand box air chamber. If the air chamber is evenly distributed and reasonably, the more stable the negative pressure field formed in the sand box, that is, the probability of box collapse can be greatly reduced, and the better the surface and internal quality of the castings produced. However, practice has proved that the same model, in a negative pressure field under its various points of the force is not the same, for a only four-wall pumping sand box, the negative pressure is often from the sand box around to the center gradually weakened, and the larger the profile of the sand box, the more obvious this trend. The decomposition and gasification of the plastic model produces a large amount of gas, resulting in a sharp rise in the local air pressure of the mold. If these gases cannot be pumped away in time, it is likely to cause the phenomenon of pouring backspray and even the expansion of the box, resulting in serious casualties and product scrap. The sand box with reasonable and uniform distribution of air chamber can still complete the pouring task well even in a small negative pressure field, which not only will not cause scrap, but also can save energy and kill two birds with one stone. as shown in Figure 3-1.

  

Figure 3-1 Sandbox used in Rio's production line.

3.3 seismic

3.3.1 The effect of seismic reality on the process of lost-mode.

In the process of LFC buried box modeling, for castings with simple structure, the main function of seismic compaction is not to damage the paint on the surface of the model within the specified time, and to ensure the accuracy of its size, to quickly fill all parts of the sand box without deformation of the model, to make the sand evenly distributed around the model, to achieve the required compactness, and to ensure that the sand particles will not have large displacement when pumping negative pressure. For some castings with complex structure and many blind holes or dead corners, if these parts are not filled with enough molding sand during the molding process and there are gaps, the coating at this part is likely to crack under the scouring of high-temperature molten iron and high negative pressure field during pouring, resulting in molten iron being sucked out of the cavity and forming iron bumps on the surface of the casting, also known as iron coated sand, which may cause local collapse in severe cases, cause unnecessary waste. Another function of the seismic platform is to overcome these dead ends in the modeling process, and it is not easy to fill the sand. The effect of seismic platform directly affects the finished product rate, dimensional accuracy, surface quality and internal quality of castings. At present, in the design of seismic platform, the amplitude, vibration frequency, exciting force and how to configure the motor are often ambiguous and lack of basic accounting basis. The reference data that can be used for reference are that the amplitude is about 0.5mm and the frequency is not less than 1500r/min, which can achieve better seismic effect. With the development of the LFC method, the original one-dimensional seismic table has been difficult to meet the production needs, and it is necessary to use a more reliable three-dimensional seismic table, or even better seismic table. It is very necessary for the selection and use of seismic platform in the casting process of LFC method. However, many enterprises are not well aware of this problem, because the seismic effect is not up to standard, sand sticking or scrapping can be found everywhere.

3.3.2 Working principle and technical parameters of seismic platform

There are three main types of seismic platforms produced by Ruiou:(1) traditional three-dimensional seismic platforms,(2) suspended excitation seismic platforms, and (3) encapsulated seismic platforms. We take the suspension-excited seismic table as an example. The general three-dimensional seismic table uses a cylinder to clamp the sand box, and the air spring is lifted or the rubber spring pad is used for isolation. The four motors in the horizontal direction generate forces in the X and Y directions respectively, while the two motors at the bottom generate forces in the Z direction. There are three groups of six motors in total. The steering direction of each group of motors is opposite, and the exciting force can be adjusted, as shown in Figure 3-2. The process parameters are shown in Table 3. The disadvantage of the three-dimensional seismic platform is that when the model is too complex, dead corners are prone to occur during the modeling process. The suspension excitation type seismic platform produced by Ruiou Company changes the previous three-dimensional seismic mode. The sand box does not need to be clamped on the jacking column (the number of jacking columns is determined according to the sand box). There are only two vibration motors equipped with gravity sensors, which can detect automatic frequency modulation according to the gravity sensor to achieve appropriate vibration acceleration. In the process of adding sand, the gravity and center of gravity of the sand box change, and the load of the molding machine changes. To achieve a better seismic effect, suitable vibration acceleration is required. The vibration acceleration is proportional to the vibration frequency. According to the feedback signal detected by the gravity sensor of the molding machine, the frequency of the vibration motor is automatically adjusted to meet the requirements. To make up for the lack of traditional modeling vibration table for complex parts of the low efficiency difficult to shape. The suspension omni-directional shock molding machine is the reverse filling of vertical movement, which can reach the vibration of different parts in all directions and the filling of various dead corners. It has the characteristics of high frequency, low amplitude and high seismic efficiency.

Fig. 3-2 ROZS-Ⅳ Suspension Excitation Platform Produced by Rui Company

Table 3-2 Process Parameters of Seismic Platform

 

3.4 negative pressure

3.4.1 The influence of negative pressure system on the process of lost subside mode

LFC casting method is also called dry sand negative pressure vacuum solid casting, negative pressure link plays an important role in the whole casting process. As we all know, LFC casting method will produce a large amount of gas in the middle cavity during the pouring process, which will cause many fatal damages to the casting. The function of the negative pressure system is not only to provide a relatively vacuum model cavity before pouring, which is convenient for the molten iron to fill the whole cavity smoothly and quickly during pouring, but also to quickly and continuously suck the gas generated during pouring out of the sand box and stabilize the negative pressure field in the casting mold, reduce back spray, reduce casting gas defects. The negative pressure system can not only strengthen the compactness of the sand, draw away a large amount of gas generated during the pouring process, but also provide a high temperature and oxygen-free environment for the pouring, which is conducive to the control of casting molding and defects.

3.4.2 Principle and technical parameters of negative pressure system

At present, the negative pressure system structure produced by manufacturers of lost foam equipment is different. The author takes the negative pressure system produced by Hebei Ruiou Intelligent Equipment Co., Ltd. as an example to make a brief description of the negative pressure system. The ROFY-35A negative pressure system of Rio is shown in Figure 3-3.

Negative pressure system through the water ring vacuum pump suction insoluble in water, non-corrosive gas, in the closed container to form a vacuum and pressure, to provide the negative pressure required in the pouring process, to provide a stable negative pressure field for the sand box.

See Table 3-3 for the configuration of negative pressure system and Table 3-4 for the technical parameters of REO ROFY-35A.

Fig. 3-3 Negative Pressure System of ROFY-35A Producing by Rio Company

Table 3-3 Negative Pressure System Configuration

 

Table 3-4 ROFY-35A Technical Parameters

 

 
4 Sand treatment

Process requirements for 4.1 sand treatment

Sand treatment system as the name suggests, this is a complete system of processing LFC method with sand, LFC method with sand is generally 40~60 purpose jewelry sand or quartz sand. We all know that after the plastic model replaces the high-temperature molten iron, the molding sand around the model is bound to be heated by the high-temperature model, and the temperature will be very high. The closer the molding sand is to the model, the higher the temperature, the modeling personnel cannot operate at all, and the production line will have new production tasks every day, and must have a certain amount of sand storage to meet the production. After the casting is cleaned up, there will be a lot of impurities mixed into the sand, such as the shedding of the coating skin, the broken pieces of the gate cup, the molten iron splashed out during pouring, etc. These impurities need to be cleaned up. Therefore, a qualified sand treatment system should have the following process requirements:

(1) It has a certain sand storage capacity and can meet daily production tasks;

(2) can be high temperature sand cooling, to achieve recycling;

(3) the sand and various impurities can be separated, clean sand;

(4) It can remove the dust in the sand and improve the environmental quality of the workshop.

4.2 Sand Handling System Configuration

The author takes the sand processing system produced by Hebei Ruiou Intelligent Equipment Co., Ltd. as an example. A complete sand treatment system should include a box turning machine, screening conveyor, chain hoist, horizontal cooling machine, belt hoist, belt conveyor, sand temperature regulator, gas conveying, sand storage hopper and dust removal system.

For a complete LFC production line, a sand handling system is essential. Each equipment has its own unique performance to meet the requirements of the vanisher process. Table 4-1 lists the functions of conventional sand handling equipment.

The sand treatment system is indispensable for a lost foam casting workshop, which can not only recycle the jewel sand, but also purify the environmental quality of the workshop. In the 21st century, the requirements for environmental quality are getting higher and higher. How to build an environmental protection workshop that meets the requirements is our common goal.

Table 4-1 Performance Requirements for Sand Treatment Equipment

 


5 Summary

5.1 Lost-in-process Equipment Concept

Due to the huge advantages of LFC casting, its development in China is rapid, the rapid development of LFC method led to a large number of industrial chain outcropping, of which the development of LFC equipment industry is the fastest. Such a rapid development speed is bound to bring some negative effects. Many equipment manufacturers have never even set foot in the field of lost foam casting, and the company has no cultural heritage of lost foam casting. However, relying on the lack of knowledge of lost foam equipment by small and medium-sized enterprises, these manufacturers can also have a place in the lost foam equipment industry. However, the equipment they produce, it is conceivable that there is no basis, is a complete imitation, such equipment may be able to produce qualified castings, but it will never stand the test of the process. The real lost foam equipment is born to ensure the lost foam process. The process is always dominant. The equipment is only auxiliary. The starting point of equipment design and production is always the requirements of the process. Equipment that cannot meet the process requirements is unqualified and defective. The author believes that equipment manufacturers should take the concept of "lost foam equipment is to protect the lost foam process" as the criterion, and make contributions to China's lost foam industry in a real sense, not just to "share a piece of the pie". Only in this way, the lost foam casting will go further, its role can play a greater role, can then China's foundry industry shine.

Future Development Direction of 5.2 Lost-in-process Model Industry

Since the development of lost foam casting, it has come to the 21st century. This century is an era of big data. Every industry will have its own industrial chain, and enterprises that can integrate these industrial chain resources can lead the way in the era of big data. The author believes that the main development direction of the future lost foam industry is also resource integration. We all know that there are many fields involved in lost foam. Only by integrating these resources together to form a complete lost foam industry chain base, can such enterprises go faster and farther, and only such enterprises can really do a good job in lost foam casting. We can boldly speculate that the future of the lost foam industry will not belong to any equipment factory, paint factory or mold factory, it will only belong to the real base of the lost foam industry enterprises, and only such enterprises can be in the lost foam industry has been developing and growing, for China's lost foam casting industry to add luster.

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