KR100887904B1 - Device of press bending and hydroforming for forming knobs or handles of household electric appliances - Google Patents

Abstract

Existing hydroforming products have inevitably generated clamp marks by bending and drain channel marks by hydroforming. If the micro-marks appear on the product appearance during the process when applying the forming as described above, it is not possible to produce a product of the quality required by the customer due to the increase in the processing time and quality instability of the surface polishing after the process.

The present invention is a method of manufacturing a device for removing the fine marks of the appearance occurring during the bending and hydroforming process in the manufacture of the tube hydroforming (tube hydroforming) molding of the handle for home appliances that absolutely requires the appearance quality The present invention relates to a handle having a very good surface state by shortening and stabilizing a process time of a product polishing, which is a post-process through securing an appearance quality of a hydroforming product.

Hydroforming, Monoblock, Press Bending, Drain Channel

Description

Device of press bending and hydroforming for forming knobs or handles of household electric appliances

1 is a diagram of a conventional hydroforming tube bending method

Figure 2 is a photograph of defects as an example of the surface defects generated by the conventional hydroforming tube bending method

3 is a photograph showing an example of applying a drain channel in a conventional hydroforming mold.

4 is a photograph showing an example of surface defects occurring on the outer surface of the product when the drain channel is applied in a conventional hydroforming mold.

5 is an explanatory diagram of one embodiment of a press bending device for applying a hydroforming of the handle for home appliances according to the present invention

6 is an explanatory view of one embodiment of a drain hole or drain hole processing method applied for product surface quality in a hydroforming mold of a handle for home appliances according to the present invention;

Main code: 1. Monoblock upper type 2. Monoblock lower type 3. Middle mold upper type

4. Middle block lower type 5. Jaw upper type 6. Jaw lower type

7. Guide mold (upper mold) 8.Guide mold (lower mold)

9.Main mold 10.Main mold

T: Tube T1: Tube before molding T2: Tube after molding

The present invention relates to a press bending and hydroforming apparatus for preventing the formation of fine marks of the appearance generated during the process in forming a molded article for home appliances by hydroforming which is absolutely required appearance quality.

The present invention also relates to a method for manufacturing a hydroforming mold and a press bending device for manufacturing a handle for a home appliance by forming a pipe or tube.

Conventionally, in the hydroforming molding method, a tube such as a tube (hereinafter, referred to as a "tube material"), which is formed by first fabricating a steel sheet prior to the hydroforming process, is subjected to a bending process and a preforming process to have the same profile as that of the final product. After inserting the molded product into a shape similar to the outline and shape of the product into a hydroforming mold having a profile and a cavity processed into a shape, the both ends are sealed by using an axial punch at both ends. After sealing (sealing) is a manufacturing method to fill the fluid inside and increase the pressure to be molded according to the mold shape.

This manufacturing method is made of various types of presses, and the steel plate is made without welding, and the pipe is made, and the hydraulic product is used to obtain the desired product shape. It has the advantage of high precision.

However, the conventional manufacturing method of the handle for home appliances has a disadvantage in that the design sensitivity is inferior because it is manufactured by melting the plastic resin as a plastic injection part and inserting it into the mold to solidify the molten resin.

Conventionally, the domestic home appliance industry is mass-producing premium stainless steel exterior products for overseas customers, and according to this trend, the handle is also applied to the handle made by applying a hydroforming method to the stainless tube to improve the emotional quality.

However, bending, pre-forming, and hydroforming processes are required to make hydroformed handles. In particular, elements that hinder appearance surface quality in conventional bending and hydroforming processes. There are many.

Conventionally, a clamp die designed in consideration of the shape of the pipe so as to clamp the front of the pipe (tube) to be bent to settle the pipe in the hydroforming die is fixed to the pipe and the other side of the pipe. Insert the mandrel needed to maintain the shape of the pipe when bending through the end, and then use the bend die mold having the desired bending curvature to rotate the clamp die to produce the desired bending shape. come.

As described above, the conventional clamping force and mandrel movement are important factors for bending molding. However, if the clamping force is insufficient, the tubing slides when bending to make a desired bending shape. Therefore, the optimum clamping force considering the outer diameter and bending curvature of the pipe is required. However, this causes fine clamping marks on the parts where the clamp die and the tube contact after bending, which appears on the surface of the product even after the hydroforming molding, which may cause quality defects in the polishing process.

Another important factor is the mandrel, which is used to maintain the shape of the pipe during bending, which can also cause surface defects, such as scratches, on the surface of the pipe, which in turn causes bursting during hydroforming molding. Can be generated.

As such, the conventional bending method cannot be applied when there are too many surface defect causing factors, the spacing between bending points is too small, or the bending curvature is too large. Was difficult.

Accordingly, the present invention eliminates the surface defects generated during the hydroforming molding process when manufacturing a stainless steel handle of the premium high appearance quality using a hydroforming method instead of the conventional plastic injection molding in accordance with the current trend as described above. Attention was paid to the manner in which the necessary molding dies were manufactured. For example, the production method of the handle for home appliances using stainless steel pipe is cut according to the curvature of the door surface of the home appliance to be joined to the hydroformed handle shape, and the press parts manufactured for the joining are attached to the cut surface. The method of manufacturing by polishing the intrinsic surface of the raw material as described above is closely related to the final product quality of the final product quality before the polishing process.

Therefore, the present invention analyzes the molding result using a pre-form analysis program, and thereby configures a press bending mold capable of realizing an optimal bending shape and achieving high surface quality without using a clamp die and a mandrel. Its primary purpose is to eliminate surface defects caused by marks.

In addition, the present invention is to ensure the emotional quality of the final product by shortening the process time and stabilization of the final product by manufacturing the hydroforming mold to prevent the formation of marks on the surface of the product while preventing the lubricating oil sticking generated during hydroforming molding. There is also its purpose.

In order to achieve the above object, the present invention is to produce a molded handle for a home appliance by a hydroforming method so as to correct the outside surface of the tube by the spring back and the mold generated when bending the hollow tube,

 A press bending mold having a radius of curvature and a shape similar to the shape of a product can be divided into upper and lower molds based on pre-analytical analysis results, and the end positions of the mold can be moved by forming both ends of the tube to determine the final curvature. Press-bending and hydro for forming a handle for home appliances, characterized in that to correct the spring back generated when bending the hollow tube and to prevent the occurrence of surface defects such as stamping, clamp marks caused by the mold It is characteristic to make high appearance quality handle through forming device.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration of the present invention.

1 shows a bending method of a tube which is a conventional hydroforming tube.

Figure 2 shows a surface defect caused by the conventional bending method of the hydroforming tube.

In the case of the hydroforming process, the lubricating oil does not escape out of the product cavity cavity during molding according to the shape and remains as it is, so that unmolded and fine wrinkles occur in the product. This was solved by forming a drain channel in the channel so that lubricating oil flowed out by internal pressure during hydroforming molding.However, as a result, there is a defect that channel marks are formed on the outer surface of the product after hydroforming. Conventional methods are not applicable to home appliance handles that must have no marks on the exterior of the product.

3 illustrates a shape in which a drain channel is applied in a conventional hydroforming mold.

FIG. 4 illustrates surface defects occurring on the outer surface of a product when a drain channel is applied in a conventional hydroforming mold. FIG.

The bending method for the hydroforming application of the handle for a home appliance according to the present invention, first, the tube in the hydroforming mold cavity (machined) processed in the same manner as the final product profile and the hydroforming mold The press bending mold cavity shape is precisely designed to be molded without any problem in the seat resistance, and the primary molding analysis is performed based on the criterion. In addition, the press bending mold is divided by the location of surface defects such as dents due to stress concentration and wrinkles due to material movement of specific parts, the stability of the bent pipe in the hydroforming mold, and spring back analysis. It may also be designed by reshaping the shape.

Based on the revised design profile, secondary molding analysis is conducted to compare the primary molding analysis results with additional analysis and design the final press bending mold shape to be reflected for the mold design.

Tubes, such as tubes, that are applied to hydroforming molding, may have a difference in spring back when bending due to differences in physical properties of the production lot, and thus the bent tubes may not be inserted into the cavity grooves processed in the same shape as the product of the hydroforming mold. As a result, when the upper and lower molds are closed, the tube may be stamped. The present invention may improve the appearance quality of the tube by changing the bending curvature through the shifting of the setting position of the divided mold.

In the case of general press mold, the bending spring back by the press cannot be modified because the mold shape profile is fixed, but the present invention can adjust the setting position of the mold that affects the final molding curvature among the divided molds in the hydroforming mold. By changing the curvature of the tube by press bending molding, it is possible to solve the surface defects caused by the instability of the mold caused by the spring back of both ends of the tube.

5 is a diagram illustrating a configuration of a press bending mold for hydroforming application of a handle for a home appliance according to the present invention. Bending molds are the upper mold (1) and lower mold (2) of the monoblock mold forming the basic structure of the bending mold, the upper mold (3) and the lower mold (4) as the middle mold for forming the center curvature of the product, the final bending curvature and To the upper and lower jaws (6) and lower (6) of the jaws, which determine the appearance quality of the bend, and to the upper and lower molds (7) and lower (8) of the guide molds, which shift the jaw's setting position to change bending curvature and improve quality. The jaws (5, 6) and the guide molds (7, 8) are fastened by screw plugs to the monoblock molds (1, 2), so that the jaws are in the up and down directions, and the guide molds are in the left and right directions. It was configured to be movable.

The press bending molding method of the tube and the quality improvement method according to the spring back generation are as follows. First, a straight tube T1 is seated on the lower jaw 6 located on both sides of the mold. The tube is bent by closing the upper mold to the lower mold. At this time, spring back is generated in the bent tube (T2). If the spring back is larger or smaller than expected, the tube is molded differently from the final bending curvature and is not seated or unstable in the hydroforming mold. The setting position of the mold must be adjusted to change the curvature.

If the spring back is larger than expected, the problem can be solved by changing the setting position of each component mold as follows. That is, the upper die guide mold 7 moves in a direction away from the monoblock upper die 1, and the lower die guide mold 8 moves in a direction closer to the monoblock lower die 2. If the setting positions of the jaws (5, 6) are moved up by a certain amount in consideration of the spring amount generated, the middle molds (3, 4) forming the intermediate curvature of the tube are fixed, and thus the curvature of the final formed bending is greater than before. Since it becomes small, it is possible to compensate the amount of spring back generated during molding. As described above, the phenomenon of the appearance of the tube during spring back generation and bending can be removed by adjusting the setting positions of the jaws 5 and 6 in the up and down directions, thereby improving the quality.

Next, the hydroforming molding method fills the tube with an incompressible pressure medium, such as a fluid, and seals both ends of the tube and applies molding pressure to the internal pressure medium to produce a desired product shape. At this time, as the tube expansion ratio required in the product design profile increases, the material flow should be improved by minimizing the friction between the mold and the tube to secure moldability. For this, lubricate the outer surface of the tube before the hydroforming molding.

In the case of lubricating oil, the higher the viscosity, the more favorable for the hydroforming molding. In the case of the handle for home appliances, the expansion ratio of 40% to 60% is generally required, so that a high viscosity lubricating oil is used to secure moldability. However, the higher the viscosity, the more likely it will remain in the mold product cavity even if the mold is fixed after the molding due to the hydroforming mold, and the product is incompletely molded or finely wrinkled due to the high viscosity lubricating oil. In order to solve this problem, conventionally, by solving the drain channel so that the lubricating oil in the mold cavity escapes during the hydroforming molding, there is a defect that the channel marks are generated on the outer surface of the product after the hydroforming molding. The present invention provides a 0.8 mm Ø drain hole in a cavity processed with a product design profile to prevent lubricating oil in the mold during hydroforming molding of the handle for home appliances by forming and processing the anti-wrinkle oil lubrication. The viscous lubricating oil is forced out through the drain hole by the high pressure generated during hydroforming molding. However, if the drain holes are made in a narrow portion in the high pressure forming hydroforming mold, the mold durability is weak and cracks may occur, so the number of drain holes should be designed to the minimum. For this reason, machining positioning for applying drain holes is very important.

The machining position of the drain hole is examined through the actual tryout, where the lubricating oil is fixed in the hydroformed product and the mold shape cavity after molding, the area where wrinkles were expected during pre-molding analysis, and the maximum expansion molding part. The final machining position is determined by considering the durability.

6 is a view illustrating an example of a drain hole processing method applied to a product surface quality in a hydroforming mold of a handle for a home appliance according to the present invention. The hydroforming mold consists of a main mold (9) having a product-shaped cavity and a basic mold for installing hydraulic components (piercing cylinder for product hole processing, ejector cylinder for product extraction, hydraulic piping). The assembled mold is assembled on the main mold 10 to determine the structure, which is assembled together with an axial cylinder on a base plate for installation on the upper bolster and the lower bolster of the press. do.

In the embodiment shown in Figure 6 the present invention is to process the 0.8mm Ø drain hole in the egg molding portion and the lubricating oil fixation expected portion in the cavity processed according to the product shape profile of the main mold (9) 5 mm escapement was performed on the surface of the main body mold 10 to be joined. And 10mm Ø hole was processed toward the outer side so that the lubricant comes out of the main body mold (10). In the conventional method, if fine marks are generated on the surface after hydroforming, the present invention has a possibility that holes are formed on the outer surface of the product even when the tube is expanded by high pressure molding because the hole outer diameter is 0.2 mm Ø or less than the tube thickness. There is no surface quality.

According to the present invention as described above, it is possible to obtain a hydroforming product having a high surface quality, and through this, it is possible to make a handle for a home appliance having a beautiful surface, which is a final product through cutting, press part welding, and surface polishing.

Hydroforming after high-moulding process can be made by manufacturing the mold using the above-described method, and it is possible to make a high surface quality hydroforming process product without the clamp marks caused by the bending and the drain channel marks caused by the hydroforming. It can shorten the production process of the ongoing process, reduce the number of people, and stabilize the quality of the surface polishing process, which can improve the utilization rate and reduce the defective rate, and in turn, can produce high quality hydroforming handles with excellent appearance sensitivity and excellent dimensional accuracy. Can be.

In addition, by using the molding analysis program, the formability of the product is analyzed to predict the spring back and the shape result by bending molding in advance, and reflect it in the production of press bending mold, which is a waste of tryout time and mold manufacturing to secure the appearance quality. Can be reduced.

Claims (2)

In order to mold the handle for home appliances by the hydroforming method,  Press bending molds with curvature radius and shape similar to product shape can be divided into upper and lower molds based on the result of preforming analysis, and the mold setting position can be moved to determine the final curvature by forming both ends of the tube. Press-bending and hydroforming to form a handle for home appliances, which is designed to correct spring back generated when bending a hollow tube and prevent surface defects such as stamping and clamp marks by a mold. Device. Press-bending molds for hydroforming application of handles for home appliances, upper molds (1) and lower molds (2) of monoblock molds, which form the basic structure of the bending molds, and upper molds (3) ) And lower die (4), upper and lower jaws (6) and lower jaws (6) of jaw to determine final bending curvature and bending appearance quality, and guide molds to shift jaw setting positions to change bending curvature and improve quality The upper mold (7) and the lower mold (8) of the jaw (5, 6) and the guide molds (7, 8) are fastened with a screw plug to the monoblock mold (1, 2), the jaw is upper, In the downward direction, the guide mold is configured to be movable in the left and right directions, and the cavity processed into the product shape profile of the hydroforming mold to prevent the unmolding and the wrinkle of the product caused by the fixation of the lubricant during the hydroforming molding. Drain Press-bending and hydroforming apparatus, characterized in that the hole is processed to the site where the failure is predicted through pre-molding analysis and the actual tryout to make the handle of high appearance quality by allowing the lubricant to escape during the pressure-resistant molding.

Images