The third chapter of the yellow area 3.3 vanish model cluster drying.


The first two sections talked about the type of paint, mixing and brushing, paint after the completion of the need for drying treatment, only to meet the requirements of use can be applied to the actual production.

3.3.1 The importance of model drying

Stirred paintThe model group is coated by dipping, brushing, showering and spraying.,It is better not to finish the coating at one time, which will make the coating thicker and the coating easy to crack.,GeneralIt is painted three times. After each layer of paint must be dried,abilityFor the next round of painting or styling, if the coating is notThere areDry, molten steel will produce a large amount of water when pouring.ofgas, causing backspray,If there are operational errors in lost foam casting, the phenomenon of back spraying often occurs,If the back spray is serious, it may endanger the personal safety of the pouring worker, so we must pay attention to it.;Additional coatingIfNot dry, paintofBreathabilityJustPoor, the gas cannot be discharged in time,CapacityEase to produce air holes and slag holes in castings, resulting in waste.

Therefore, drying is also an important part of the lost foam casting process.

BecauseEPS model internal andCoatingAll contain water, andEPS softens and deforms at about 80°C, so a reasonable drying temperature should be45-5Between 5 degrees Celsius. In addition to temperature control in the drying process, should also pay attention to the control of humidity, humidity can not be high, otherwise the paint can not dry, will cause stomatal defects, the general control of air humidity ≤ 30%. A good drying room should have uniform temperature distribution, controllable, smooth air convection, good heat preservation effect and reasonable humidity control.

 

The following points should be noted when drying the coating:

① During the drying process, pay attention to the reasonable placement and support of the model to prevent deformation;

② At the end of drying, check whether it is completely dry (up and down, left and right, inside and outside);

The model after drying should be placed in a place with low humidity, placed securely to prevent moisture, deformation, etc.

 

The following pictures pay attention to check whether the corners and interior are completely dry:

    

Figure 3.3.1Elbow Figure 3.3.2motor housingFigure 3.3.3model cluster

3.3.2 Requirements for drying room

Therefore, we need to meet the following requirements when designing drying rooms:

The first is the temperature and humidity, the general requirements of hot dry air temperature inBetween 45-55 ℃, the air humidity is less than or equal to 30%, such as drying in a well-ventilated drying equipment, the effect is better. Then, according to the painting process of paint, we roughly divide the drying room into four categories: white film drying room, one-time painting drying room, two-time painting drying room and three-time painting drying room, which is convenient for the classification and storage of models and the control of drying time. The fourth is the space size of the drying room. According to the number of drying shelves and the size of castings, it is convenient for workers to take the model. Generally, the height of castings without special size (the size of castings is within 1 meter) is within 2.5 meters. Fifth, the door opening size of the drying room, the drying rack is customized according to the casting size, and the drying rack is required to be convenient to turn and smooth in logistics. The size of the door opening is too small to be easy for logistics operation, and the general width is about 2.5-3 meters. Moreover, the movable door requires good sealing.

3.3.3 Design of drying room

  After understanding these requirements, we can begin to design the drying room.

1、To design a drying room, the first thing we have to determine isThe area of the drying room.

① Because the customer's output and castings are known, we can calculate the number of EPS models required per hour according to the output n, and calculate the appropriate drying rack size and the number of EPS models that can be placed in each drying rack according to the casting size x. According to these two data, we can calculate the number of drying racks required per unit time;

② Then, calculate the number of drying racks required for a day by the working system, and calculate the total floor area of the drying racks required for a day according to the layout of the workshop and the floor area of the drying racks;

According to the process requirements, the drying time of the white mold isFor 1-2 days, the drying time for one painting and the second painting is about half a day respectively, the drying time for three painting is not less than one day, and the drying room for three painting and brushing needs to store yellow molds that can be used at any time;

According to the time required for different drying rooms and logistics operation, it is concluded that the area of the drying room is not less than the total area of the drying rack required for 4-day production.

For the drying rack mentioned above, it is convenient to take the model. The height of each section and the width of the drying rack are determined according to the size of the model, and the total height is generally not more1.5 meters. In addition, the support of the drying rack can be made of angle steel, flat steel or steel bars. Special attention should be paid to the fact that when angle steel and flat steel are used, the thickness direction should be placed vertically, that is, the smaller the contact surface with the model, the better. For models that have been painted, a wider contact surface may damage the coating.

2. Next, explain the drying method in the drying room.

The current popular drying technology is mainly ultraviolet drying, infrared drying, electromagnetic drying and hot air drying. They have their own characteristics and are widely used in various mechanical equipment and food drying.Among them, the drying methods commonly used in the lost foam industry are the following.

  According to the heating and cooling methods and production mode, we can divide the drying room into the following three categories:

① Conventional heater indoor heating drying room

② Tunnel drying room

③ Sunshine collection type drying room

① Conventional heater indoor heating drying room

Conventional heater indoor heating drying room usually adopts electric heating, steam heating or electric and steam mixed heating. At present, the domestic more advanced and practical is the temperature and humidity automatic adjustment and control of energy-saving insulation drying room. This kind of insulation drying room adopts folk houses and insulation boards, or directly adopts about20cm thick flame retardant foam composite insulation board and color steel plate production, the wall and the door has a good sealing, good insulation effect. When the model is dried to a dry state, the weight is constant, and the drying time must be determined through tests. The initial drying speed of the coating is relatively fast. Generally, 70%-80% of the water can be dehydrated within 20%-30% of the total drying time, while the remaining 20%-30% of the water needs 70%-80% of the total drying time to be slowly dehydrated. The reason is that with the evaporation of water, the air humidity in the room is too large, such as the installation of air dehumidification system in the drying room, reduce the air humidity in the drying room, accelerate the air circulation, can greatly accelerate the drying of the model. In addition, the hot air dehumidified by the dehumidification system can be returned to the drying room for waste heat recovery and recycling, which can save a large part of resources.

The temperature and humidity automatic adjustment and control system uses temperature and humidity detection devices to monitor the temperature and humidity changes in the drying room in real time. If the temperature is too high, some heating devices will be turned off, and if the humidity is too high, the dehumidification system will be turned on for dehumidification. The whole process does not require manual intervention. After the range is set, the temperature and humidity inside the drying room will be automatically adjusted to save resources.

Figure 3.3.4Conventional heater indoor heating drying room (steam type)

Figure 3.3.5steam drying heater

    

Figure 3.3.6Electric heating device (13.5KW)

② Tunnel drying room:

Tunnel drying room is generally a long straight tunnel, the bottom of the laying of the track running kiln car. There is a drying pipeline for continuous drying, which constitutes a pipeline mode drying. On the premise of ensuring the requirements of the material drying process, the tunnel drying room scientifically uses the principle of thermodynamics to ensure that the surface water is not dry, so that the heat can quickly enter the inside of the material, and then the heat transfer gradient is used to transfer the internal moisture of the material to the surface (to prevent the material from cracking and peeling), and then the fresh air is quickly dried to improve the drying speed, discharge high-humidity waste heat gas, and use the waste heat recovery device to preheat the fresh air, play a role in energy conservation.

Figure 3.3.7Single group tunnel type

Figure 3.3.8double group tunnel type

Figure 3.3.9automatic catenary

① Features:

 Than conventional drying room can save50% plant investment;

 Than conventional drying room can save50% energy;

 Shorter than conventional drying room50% drying time.

② System overview:

  

   

closed loop heatingHomogenization (moisture regain) fresh air waste heat recovery drying

Figure 3.3.10Schematic Diagram of Tunnel Drying Room System

Picture 3.3.10   The tunnel type drying room systematic theory picture

This process uses two different functional areas in the same tunnel drying line, respectively, to complete the closed-circuit circulation of high-humidity air and rapid heat transfer of the material to make the material heat up quickly, the two-zone buffer zone is a homogeneous zone (moisture return zone), the use of heat transfer gradient to transfer the internal moisture of the material to the surface, in order to facilitate drying. The heat contained in the moisture exhaust outside the drying area is recovered by the waste heat recovery device, and the new air is preheated at the same time to save energy. After preheating, the air is further heated by the heater to keep the maximum relative humidity difference with the material to dry it to achieve the best effect, and the homogenization (resurgence) of this process is completed in progress without artificial setting and operation, especially suitable for surface water drying. The direction of travel of the material and the wind direction of the dry air are in the forward direction.-- Reverse, this process can completely ensure that the upper, middle and lower positions of the material are evenly dried, and the air volume, air temperature and drying time can be adjusted according to the actual production.

   

The components of the tunnel drying system are: the main circulation system, the waste heat recovery system, the secondary circulation system, the control system and the monitoring system.

 

There are three coating drying lines, one for coating, one for coating, one for coating and one for coating. The trolley speed can be adjusted according to the actual situation (coating baume, hanging coating thickness and leveling uniformity), so as to shorten or lengthen the drying time and meet the product drying requirements. If steam is used as a heat source in the drying room, the required steam pressure0.3-0.6MpA, if the condensate is recycled by a recycling machine, the energy saving effect is better. Recycling machine is 80 ℃ discharged condensate recycling back to the boiler for use, can save energy, no need to heat the water from room temperature to 80 ℃, directly from 80 ℃ heating to evaporation. In the drying, should be the corner of the accumulation of paint thicker place time appropriate extension or brush after drying.

③ Sunshine collection type drying room

Sunshine collection drying room is the use of solar collectors for heat collection, drying of materials.

Sunshine collection type drying roomSignificance and advantages:

Save conventional energy, reduce production costs and improve economic efficiency;

Protect the natural environment and prevent serious pollution to the environment caused by frequent fuel consumption.

Disadvantages:

Easily affected by weather conditions, normal heating cannot be carried out in rainy and snowy weather or at night, and electric heating or steam heating devices need to be installed to assist in heating.

The working principle of sunlight collection drying room:

The high-efficiency solar energy collection and conversion device is adopted to uniformly input the collected solar energy from the lower layer of the drying room, discharge the hot and humid exhaust gas from the exhaust pipe on the top or recycle it after dehumidification. Electric heating device or steam drying heater is installed inside the drying room for auxiliary heating and heating, so as to ensure that the temperature in the drying room is stableBetween 45 ℃-55 ℃.

Figure 3.3.11Design Diagram of High Efficiency, Equilibrium and Quick-drying Thermal Cycle Dehumidification Drying Room

Compared with the ordinary drying room, the heat cycle dehumidification drying room only adds a dehumidifier, but the drying effect and energy saving effect are incomparable to the ordinary drying room.

Figure 3.3.12 Ruiou sunshine collection type drying room

The above introduces three kinds of drying room, summarizes the advantages and disadvantages of three kinds of drying room and the use of effect, we can consider in the design of drying room, choose suitable drying room style. But should also pay attention to a few points:

Insulation effect and tightness;

The heating device or hot air inlet is below the drying room, and the heat is transferred from bottom to top;

It is best to install a dehumidifier and a waste heat recovery device, which is efficient and energy-saving.

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