Refrigerator liner vacuum molding is the main process of refrigerator production, and it is also a key process. The key factor affecting the quality of vacuum forming products, production efficiency and cost is the vacuum forming mold. The key point and difficulty of the vacuum forming mold design is the design of the core-pulling mechanism. Whether the core-pulling mechanism design is reasonable or not directly affects the reliability of the mold and determines the manufacturing cost of the mold to some extent. Therefore, in the vacuum forming mold design, the core pulling mechanism must be designed flexibly according to the structure and material characteristics of the product. Even in the same auxiliary mold, the core pulling mechanism has a variety of design methods. To ensure that the mold work is reliable and the molding quality is high, it is also necessary to simplify the mold manufacturing process as much as possible and reduce the manufacturing cost of the mold. The vacuum forming mold introduced in this paper is a relatively complex mold that incorporates a variety of core-pulling mechanisms. Its design has strong typical characteristics.
1 core extraction mechanism design program analysis 11 Refrigerator liner structure and material analysis A refrigerator plant has a freezing chamber gall, as shown. The freezer compartment D of the refrigerator refrigerator is an elongated lateral boss with its upper surface flush with the large plane (upper top surface). Obviously, it is not possible to use a straight pull core. Only the oblique core is used.
E is a large lateral boss, although the protrusion height is not large (only 5mm), but the distance is long, the area is large, can not force demoulding must be demoulded through the core. According to the structural features of the site, either straight or cored cores can be used. If the core is pulled straight, the upper mold part of the movable block will be on the arc surface, which will make it difficult to make the mold, and it is easy to form joint marks on the surface of the product. According to the force state analysis of the movable block, it needs a big Cylinder clamping can balance the blister pressure and increase the cost of mold manufacturing.
If the core is pulled out in an oblique manner, proper handling of the structural design can completely avoid these problems.
2 Core-pulling mechanism design 2.1 Core-pulling mechanism Movement and mechanics analysis The key to designing the core-pulling mechanism is to ensure reliable movement, accurate position, smooth ejection, long service life, and no harm to the product.
The straight pull core is used at A, and the motion of the moving block directly uses the expansion and contraction of the cylinder to realize linear motion. The actual expansion stroke of the cylinder is the movement stroke of the moving block.
During the plastic molding process, due to the pressure difference between the inside and outside of the mold, the movable block will be subjected to an adsorption force to urge the movable block to move away from the forming position inward. Therefore, there must be a force to balance, and this force is the clamping force. . Clamping force calculation formula is: =PXS:F* Clamping force S*pressure difference Effective area due to the smaller forming area of ​​the movable block at A, that is, the effective area of ​​the differential pressure is small, and the clamping force is small and can be made by the cylinder. The thrust is directly provided, and the cylinder diameter does not need to be large. According to the calculation, the cylinder diameter is selected to be 50mm, the stroke is 20mm, and the same core-pulling mechanism is used to pull the core at point B. The working principle is the same as that of point A, although the clamping force is not Large, but the active block is slender, in order to ensure the smooth movement of the moving block, must use a structural design different from A.
D is used to pull the core, the movable block can be along the direction of the stripping direction with a certain angle of the direction of the linear motion, but also around a point for circular motion. According to the characteristics of the structure of the product, the use of a moving block around a certain point for a circular motion program is more appropriate.
One of the advantages of slant core pulling is that it can directly use the stripping force (product pull force on the live block) to achieve core pulling. However, this activity block is relatively large, whether it can use the stripping force to achieve core pulling, and it needs to be analyzed in detail. According to production experience and field tests, it is found that for ABS sheet, because of its good toughness, it is possible to directly use the stripping force to drive the rotation of the movable block to achieve smooth demoulding, and the effect is good. For HIPS sheet, due to its relatively poor toughness, when this method is used to release the mold, the products are often pulled and the reject rate is greatly increased. In this case, an auxiliary demoulding cylinder must be provided, and the addition of an auxiliary demoulding cylinder is also conducive to the smooth reset of the movable block. Practice has proved that after adding an auxiliary mold release cylinder, the service life of the core-pulling mechanism at this place has been improved.
The movable block has a relatively large molding area and is subjected to a large adsorption force during the molding process. In order not to increase the mold clamping cylinder, all the adsorption force must be directly transmitted to the mold body. This requirement is based on the structure here.
The forming area of ​​this movable block is much larger than that of D, and the adsorption force is quite large. We must think of ways to directly transfer the adsorption force to the mold body. This requirement cannot be achieved by properly designing the parting surface of the active block. Other design methods must be considered. Through repeated analysis and comparison, it was decided to adopt a parallel four-bar linkage mechanism, because the pulling distance of the movable block is not large, only 5, through the movable block to the inside of the mold for translational movement, can easily achieve demoulding. In the forming position, the four-bar linkage is rectangular, and the adsorptive force on the movable block is directly transmitted to the die body through four horizontal short links, and the live block is tightly locked by the adsorption force received on the upper surface of the movable block. Forming position. Considering that the active block is self-contained, an auxiliary demoulding cylinder should be set up to allow the auxiliary demoulding cylinder and the stripping force to pull the movable block together to make a translational movement to the inside of the mold. After demoulding is completed, the weight of the movable block and the cylinder block are used. Hysteresis to achieve a smooth reset.
2.2 Design of core-pulling mechanism structure The design of the core-pulling mechanism includes the selection of the movable die parting surface, the design of the core-pulling mechanism, the guiding device, the limiting device, the determination of the movement trajectory and the stroke of the movable block, the calculation of the clamping force, the selection of the cylinder bore and stroke.
Among them, the selection of the parting surface should be determined according to the structural characteristics of the boss or pit, and the parting surface should be avoided to leave marks on the product. In particular, straight core-pulling mechanism, in order to ensure that the movable block moves freely between the dies, there must be a certain gap between the movable block and the phantom. Generally, the unilateral clearance is taken as 0.05 to 0.1 mm, and in some cases it is 0.2 to 0.25 mm. At this point, the blister force at the gap is much greater than the wicking force of the suction holes around it, causing the product to form seams along the gap. Therefore, the parting surface is generally selected at a corner that is not easily adsorbed, or where it is easily covered by a partition or other objects.
The guiding device can be determined according to the specific circumstances. Generally, the moving block is large and the shape is complex. In order to ensure that the moving block moves smoothly, guide devices should be provided.
The structural design of the core-pulling mechanism is shown as shown.
A is the simplest, the mold surface is selected at the corner of the boss, and a special mold clamping device is installed to ensure accurate positioning of the movable block; the ejection stroke is controlled by the air cylinder to ensure that the guide portion of the movable block is always in the hole of the mold body. Due to the small size of the moving blocks, no special guides are required. However, the center of the cylinder should coincide with the center of the adsorption force on the moving block.
Mold assembly assembly. Movable block B2 Linear bearing and bearing block 3. Cylinder 14. Moving block C 5. Moving block A6 Cylinder 27. Connection plate B and C centering principle is similar to A, the parting surface is selected to be covered by the shelf Where, in the middle of the mold, a common cylinder is used, which controls the two movable blocks at the same time. Considering that the movable blocks are thin and long, each movable block is provided with two tie rods, and two tie rods are connected to the cylinders through connecting plates, and the two tie rods also serve as guide posts. In order to ensure smooth and smooth movement, with the guide column 13 connecting rod 2nd order, as a mold clamping limit, there is a special limiting block with a mold release limit.
The key to the structural design of the core-pulling mechanism at D is the determination of the rotation angle of the movable block. It involves the optimal design of the connecting rod and the support. The movement of the movable block is simulated by CAD, and this design requirement is easily achieved. The determination of the position of the parting surface on the movable block is also very important. It is necessary to ensure that the movable block can not be too large, but also to ensure that the movable block is equipped with linear bearings. The base block on the movable block is set to touch without interference.
The key to the design of E is the determination of the position of the center of force of the four horizontal links relative to the movable block, which must ensure that all the adsorption forces are transmitted to the mold body; and the second is to determine the position of the upper mold surface based on the motion trajectory of the movable block. Its tilt angle ensures movement of the moving block without interference. The selection of the auxiliary demoulding cylinder can guarantee the normal movement of the core-pulling mechanism as long as it is selected.
3 Concluding remarks Although the structure of the product is complex, the design of the mold is difficult, there are many places where the cores are pulled out, and the size and shape are different. Through analysis and comparison and flexible design, this problem is solved. Practice has proved that the mold design is reasonable, reliable, high-quality molding, mold manufacturing costs within the budget range, to achieve the design goal.
(Continued from page 19) Since there are many holes and grooves in the punch part of the die, the punch of the die adopts an integral structure, and the die is of an insert structure, which is compact. For the case where the lateral core pulling distance is relatively short, the unique structure of the three sided guide pillars for lateral core pulling is designed. After injection molding, I once sub-typed to complete the lateral core-pulling action. When the limit pull rod hits the de-watering plate, it starts the secondary sub-type, the purpose is to make the aggregate fall off automatically, and then it starts three sub-types to complete the dynamic die and Separation of the fixed mold. The final injection machine pushes the pusher pad, the pusher and the pusher act simultaneously, ejecting the plastic parts.
The working process of the mold is as follows: After the injection molding, when the mold is opened, under the action of the spring 12 and the cold material point of the aggregate, the molding is started once, and the fixed mold base plate 7 and the dewatering plate 8 are separated and dewatered. The plate 8 drives the slider 20 to move backwards. Because the diagonal movement of the inclined guide column 25 and the slider 20 pushes the sliding movement of the slider, the slider moves laterally along the guided dovetail groove on the die pushing plate 3 Complete the lateral core pulling action. When the limit lever 26 hits the de-screwing plate 8, the de-screwing plate 8 stops, and once the parting is completed; the concave template 4 continues to move, and the secondary parting is started, so that the point gate is broken and the aggregate is broken off. When the limit pin 5 fixed on the concave die plate 4 hits the end of the limit pull plate 6, the concave die plate 4 stops moving and the secondary split ends. The mold continues to move, and the three sub-types are started to separate the concave template 4 and the core 14; under the action of the tightening force of the plastic model, the plastic model continues to move with the moving mold. When moving to a certain distance, the push rod of the injection machine pushes the push plate 18, drives the four push rods and the push plate 3 to push the plastic parts out of the movable mold.
When the mold is closed, when the movable mold moves to the concave mold push plate 3 and the movable mold base plate is engaged, the movement continues, and the convex mold core 14 and the concave mold plate 4 are engaged when moving to the I parting surface. At the same time, the return rod is reset; the mold is continued to be closed, and the dewatering plate 8 and the concave template 4 are engaged when moving to the parting surface. When the slider continues to move, relative movement occurs when the slider is under the double action of the diagonal guide and the wedge block, and the slider is forced to move laterally along the dovetail groove to force the lateral core to return when the stripper plate 8 and the fixed mold platen 7 When it is fully meshed, the mold closing ends and the next working cycle can be resumed.
4 Features of the mold The mold is designed into three parting surfaces. Clever use of the limiting lever 26 to perform the relative shedding movement of the stripper plate 8 to complete the automatic shedding action of the aggregate, and the spring 23 ensures the accurate positioning of the slider, thereby ensuring It can complete the side core pulling and resetting process of plastic parts and improve the production efficiency. The dovetail slot on the slider not only serves as a guide, but also is easy to install on the concave template. Because the plastic parts are thin and uniform plastic parts, and the punch part has many holes and grooves, there is a large tightening force, in order to ensure the launch of the plastic parts, so design four putter plus push Board to balance pushing force. After production practice has proved that the mold opening and closing mold movement fully meets the design requirements, and the product quality of the plastic parts has also been fundamentally guaranteed.
NINGBO RUICAN MACHINERY COMPANY has more than 10 years experience for Investment Casting, investment wax casting, silicon sol casting. It is widely used in carbon steel, stainless steel, copper castings, etc.
Our product is including stainless steel adapter BSPP Threaded quick coupling, aluminum camlock coupling, Polypropylen Camlock Coupler Type B Male Threaded Quick Connect Coupling etc.
Push and pull connection
With safe lock to avoid accidental disconnection
Standard material: Carbon steel, copper, stainless steel, aluminum
Material grade:GB, ASTM, DIN, BS, JIS, NF
Standard seal: Nitrile rubber, fluoride rubber
Quick Couplings,Coupling Quick Fitting,Quick Pipe Coupling,Fire Quick Couplings
Ningbo City Yinzhou Ruican Machinery Co.,Ltd , https://www.kstcasting.com