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Heat treatment of Air Cooler Mould(FURNITUREMOULD) is an important process to ensure mould performance, which has a direct impact on the manufacturing accuracy of air cooler mould, the strength of plastic mould, the working life of mould, and the manufacturing cost of mould.

The heat treatment of air cooler mould is to exert the potential of mould material and improve the service performance of mould. The performance of the air cooler mould must meet the following requirements: high strength (including high-temperature strength, cold and hot fatigue resistance), high hardness (wear resistance) and high toughness, and also require good machinability, (including good polishing) weldability and corrosion resistance, etc.

The deformation of air cooler mould after heat treatment is generally believed to be caused by cooling, which is incorrect. For complex dies, the correctness of the heat treatment process often has a great influence on the deformation of air cooler dies. Comparing with the heating processes of some dies, it can be clearly seen that the heating speed is faster and larger deformation often occurs.

(1) The cause of deformation

Any metal will expand when heated. As steel is heated, uneven temperature (i.e. uneven heating) in each part of the same mould will inevitably lead to an inconsistent expansion in each part of the air cooler mould, thus forming internal stress due to uneven heating. At the temperature below the transformation point of steel, uneven heating mainly produces thermal stress, and uneven heating beyond the transformation temperature will also produce uneven microstructure transformation, which not only produces microstructure stress. Therefore, the faster the heating speed is, the greater the temperature difference between the air cooler die surface and the core, the greater the stress and the greater the deformation of the air cooler die after heat treatment.

(2) Preventive Measures

When heating complex dies below the phase change point, they should be slowly heated. Generally speaking, the vacuum heat treatment deformation of air cooler dies is much smaller than that of salt bath furnace heating quenching. Preheating is adopted, and one-time preheating can be adopted for low alloy steel moulds. For high alloy rigid moulds, secondary preheating shall be adopted.

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In the process of plastic melting and plasticizing, the Crate Mould(FURNITUREMOULD) is prone to defects. The solution is to reduce the quenching stress after heat treatment to a minimum, because the quenching stress and the mesh carbonized structure, under the action of grinding force, can easily crack the workpiece due to phase transformation of the structure. Reasonable use of cooling and lubricating fluid, play the three major roles of cooling, washing and lubrication, keep the cooling and lubricating clean, thus control the grinding heat within the allowable range, and prevent the thermal deformation of the workpiece.

Specific Operation of Processing Defects of Crate Mould:

1. Improve the cooling conditions during grinding, such as adopting oil impregnated grinding wheel or internal cooling grinding wheel and other measures. When cutting fluid is introduced into the center of grinding wheel, cutting fluid can directly enter grinding area to play an effective cooling role and prevent workpiece surface burns. Reasonable use of cooling and lubricating fluid, play the three major roles of cooling, washing and lubrication, keep the cooling and lubricating clean, thus control the grinding heat within the allowable range, and prevent the thermal deformation of the workpiece.

2. Reduce the quenching stress after heat treatment to the minimum, because under the action of grinding force, the quenching stress and reticular carbonized structure can easily cause cracks in the workpiece due to phase transformation of the structure. In order to eliminate the grinding residual stress of high precision dies, low temperature aging treatment should be carried out after grinding to improve toughness.

3. To eliminate grinding stress, the crate mould can also be immersed in salt bath at 260 ~ 315℃ for 1.5min, and then cooled in oil at 30℃, thus the hardness can be reduced by 1HRC and the residual stress can be reduced by 40% ~ 65%.

4. For precision grinding of precision dies with dimensional tolerance within 0.01mm, attention should be paid to the influence of ambient temperature and constant temperature grinding is required. From the calculation, it can be seen that when the temperature difference of 300mm long steel parts is 3℃, the material has a change of about 10.8μm (10.8=1.2×3×3, the deformation amount per 100mm is 1.2μm/℃). All finishing processes should fully consider the influence of this factor.

5. Electrolytic grinding is adopted to improve the manufacturing precision and surface quality of the crate mould. During electrolytic grinding, the grinding wheel scrapes off oxide film instead of metal, so the grinding force is small, the grinding heat is also small, no grinding burr, crack, burn and other phenomena will occur, and the general surface roughness can be better than Ra0.16μm; In addition, the abrasion of the grinding wheel is reduced. For example, when grinding hard alloy, the abrasion of the silicon carbide grinding wheel is about 400% ~ 600% of the weight of the hard alloy, while when electrolytic grinding is used, the abrasion of the grinding wheel is only 50% ~ 100% of the abrasion of the hard alloy.

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If the design of the Daily Necessities Mould(FURNITUREMOULD) has not been fully reviewed collectively, the mould structure is unreasonable, which makes the mould undergo many improvements after the mould test, thus making the cost of the daily necessities mould exceed the budget.

If it can be fixed after several improvements, it is lucky. There are many cases that are not satisfactory. Even if the daily necessities mould has to be scrapped and re-made, the cost cannot be controlled. There are also cases where the design of the daily necessities mould is very good, but the processing of the daily necessities mould is not in place, which increases the number of mould tests for no reason and directly increases the mould cost. There is no objection to this problem, so many mould manufacturers have increased their investment in measuring equipment.

What will be the consequences of more tests for daily necessities mould?

1. The best moulding process and the model of the injection moulding machine were not selected during the mould test. Obviously, the mould was well done, but the injection moulded products were not ideal. For no reason, the number of mould tests is increased, which directly increases the mould cost. This is a common problem in some small mould factories.

2. The physical properties of plastics are not fully understood, and even the shrinkage rate is not accurate. This happens from time to time. Therefore, the physical properties of plastic must be made clear before designing moulds for daily necessities so as to effectively reduce the number of mould tests.

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During the use of Table Mould(FURNITUREMOULD), mould wear is a common phenomenon and inevitable. What we can do is to minimize the wear of the table mould and prolong its service life. When we reduce the wear of the table mould, we must first know why the mould wears.

The root cause of table mould wear is the mutual friction between mould parts and parts (or blanks) or between mould parts and parts. Wear leads to mould failure, which is manifested as blunting of blade gate, rounding of edges and corners, plane subsidence, surface groove marks and peeling of the mucosa. In addition, during the work of the punch, the lubricant is converted into high-pressure gas after combustion, which severely scours the surface of the punch and forms cavitation.

During cold punching, if the load is not large, the wear type is mainly oxidation, and the wear can also be occlusal wear to some extent. When the cutting edge becomes blunt or the punching load is large, the occlusal wear will become serious, thus accelerating the wear. In the case of severe carbide segregation or large particle carbides in mould steel, these carbides are easy to flake off, causing abrasive wear and accelerating the wear.

The impact of light cold work mould steel (sheet blanking, stretching, bending, etc.) is not heavy, mainly static wear. Under the condition of static wear, the mould steel contains more carbon and its wear resistance is greater. Under impact wear conditions (such as cold heading, cold extrusion, hot forging, etc.), excessive carbides in mould steel do not help to improve wear resistance but reduce wear resistance due to impact abrasive wear.

The above is an introduction to the causes of mould wear analyzed for everyone. in general, under the condition of impact abrasive wear, the carbon content of mould steel is limited to O.6%%, and the cold heading mould works under the condition of impact load, such as too much carbide in mould steel, which is easy to cause solid impact wear and peel off the surface. These exfoliated hard particles will become abrasive particles, accelerating the wear rate. Therefore, in the mould work, we should reduce the occurrence of this kind of situation.

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The selection of Chair Mould(FURNITUREMOULD) materials is also important because it not only affects the service life of the chair mould but also directly affects the manufacturing cost of the chair mould. Therefore, some principles should be followed in selecting chair mould materials. Let's take a look below.

(1) According to the type of chair mould processing and its working conditions, the selected materials shall meet the use requirements and shall have higher strength, hardness, wear resistance, impact resistance, fatigue resistance, etc.

(2) selecting materials according to stamping materials and batch production of stamping parts; Meet the processing requirements, should have good processing performance, easy cutting processing, good hardenability, heat treatment deformation is small;

(3) To meet the requirements of the economy, various chair mould parts can be roughly divided into working surface parts, plate parts, shaft parts, sleeve parts, etc. in the processing and manufacturing of chair mould according to the similarity of parts structure and processing process. The processing methods mainly include mechanical processing and special processing. The mechanical processing methods mainly include the cutting processing of various metal cutting machines. Using common and numerical control cutting machines to carry out turning, milling, planing, boring, drilling and grinding processing can complete the processing of most die parts, and then matching with fitter operation can realize the processing and manufacturing of the whole set of dies.

(4) With the continuous improvement of the quality requirements of the chair mould processing, the mould materials with special properties such as high strength, high hardness, and high toughness are appearing continuously and the number of complex profiles and holes is increasing. The traditional mechanical processing methods have been unable to meet the requirements of mould processing. Therefore, the process methods of directly using electric energy, heat energy, light energy, chemical energy, electrochemical energy, acoustic energy, and other special processing have been developed rapidly. At present, the special processing methods mainly based on electrical processing have been widely used in modern mould manufacturing, which is an important supplement to the mechanical processing methods.

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