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Principle of Multi-station Progressive Die Layout and Design
In the progressive stamping process parts in the progressive die with punch, each blunt once is sent to a forward step, arrive at a different location. Due to the processing content of each other is not the same for each station, therefore, in the progressive die design process, want to determine from a sheet metal blank to product parts forming process, the content of each station to the machining process, the design process is the layout design.
Layout design is one of the keys of multi-station progressive die design. The optimization of the layout is related to the utilization rate of materials, the precision of the workpiece, the difficulty and service life of the mold manufacturing, and the coordination and stability of the various stations of the mold. The layout of the multi-station progressive die should comply with the layout principle of an ordinary punching die and consider the following points.
- At first make stamping parts to expand the blank sample (3~5), repeatedly test row on the map. After the preliminary scheme is determined, at the beginning of the layout of the arrangement of punching, incision, waste cutting, and other separation station. Then to the other end of the arrangement of forming station, finally arrange the separation of the workpiece and the carrier. In the arrangement of the station, to avoid punching half hole, to prevent uneven punch force and break.
- The first station is generally arranged punching and punching process guide hole. The guiding pin is set at the second station to guide the belt material. In the following stations, the guiding pin is set according to the number of stations and the station where the movement is easy to occur. The guiding pin can also be set at every 2~3 stations in the following stations. The third station can set the error detection device of the feeding step according to the positioning accuracy of the stamping strip material.
- The number of holes on the stamping parts is more, and the position of the hole is too close, can be distributed in different stations on the punching. But the hole can not be due to the influence of the subsequent forming process and deformation. For holes requiring relative position accuracy, synchronous flushing should be considered. When the mold cannot be blown out synchronously due to the limitation of mold strength, measures should be taken to ensure their relative position accuracy. The complex hole can be decomposed into some simple hole out step by step.
- When there is a local reinforcing bar, it should be arranged before punching to prevent the deformation of the hole caused by the reinforcing bar. When the sudden package, if there is a hole in the center of the sudden package, to facilitate the flow of materials, a small hole can be punched first. Then the pressure of the sudden package is rushed to the required aperture.
- To improve the strength of die inserts, discharge plates, and fixed plates. To ensure that the forming parts of the installation position do not interfere, can be set up in the layout of the empty station. The number of the empty station according to the requirements of the mold structure.
- For bending and deep drawing forming parts, the deformation degree of each station should not be too large.The stamping parts with a large deformation degree can be formed several times. This is not only conducive to quality assurance but also conducive to the debugging and finishing of the mold. For the forming parts that require high precision, the shaping station should be set up. To avoid the deep drawing of the material in the deformation zone of U-shaped bending parts, it should be considered to bend 45 first, and then bend to 90°.
- In the layout of progressive drawing, techniques such as cutting and grooving before drawing can be applied to facilitate the flow of materials.
- The choice of forming direction (up or down) should be conducive to the design and manufacturing of the mold, is conducive to the feeding of the star Chang. If the forming direction is different from the stamping direction, the oblique slider, lever and swing block, and other mechanisms can be used to convert the forming direction.
Content of Multi-station Progressive Die Layout
The Result of the Layout Design of the Multi-station Progressive Die is the Layout Drawing. Once the Layout Drawing is Determined, the Following Aspects are Determined.
- Stamping sequence of each part of the blanked parts in the die.
- The number of mold stations and the processing content of each station.
- The arrangement and orientation of the blanked parts on the strip material. And reflect the high and low utilization rate of materials.
- The nominal size of the step distance and the way to set the distance.
- The width of the material.
- Form of the carrier.
Layout in Progressive Die Design Includes Three Aspects. That is, Blank Layout, Punching Edge Shape Design, and Working Procedure Layout.
- Blank layout refers to the arrangement of the developed shape of the parts on the strip. The blank layout must be carried out in the design of all types of stamping dies.
- The design of the punching edge shape refers to the decomposition of the geometric shape of the parts with a complex shape or inner hole to determine the stamping sequence of the shape of the parts. Which is the design work that must be completed before the process layout.
- process layout to determine the mold by the number of stations, each station of the specific processing procedures, is the blank layout and punching edge shape design of the synthesis. is the key to the design of the progressive die. Process layout is referred to as layout.
A schematic diagram of the above layout is shown in Fig. 1-1.
The blank layout is to determine the cutting azimuth of the blank shape of stamping parts on the strip and the relationship between the blank and the adjacent blank. Blank in the plate can be intercepted a lot of azimuths, so there is a variety of blank layout schemes. The following problems need to be solved when designing the blank layout.
- Type of layout.
- Determining the boundary value of the overlap.
- Determination of advance (step) distance.
- Determination of strip width.
- Material utilization rate.
The above content in addition to the edge value is larger than the ordinary stamping. Other content is the same as the ordinary stamping, and will not be repeated here.
Cutting Edge Design
In the design of progressive die, to achieve the complex parts (such as bending, deep drawing, forming, and other processes of the stamping parts) stamping or simplifying the structure of the die, the complex shape and inner shape of the hole is usually cut several times. The design of the punching edge shape is to decompose the complex inner or outer contour into several simple geometrical units. Each unit forms a new punching contour through combination and complement. To design a reasonable punching edge shape of the punch and concave die. This is shown in Figure 1-2. This process needs to address the following issues.
Decomposition and Reorganization of Contour
The stamping parts encountered in the actual products are often very complex. The shape design of the punching edge is the decomposition and reorganization of the cutting edge, as shown in Fig. 1-2 (b).
Cutting edge decomposition and recombination should be carried out after the blank layout, should follow the following principles.
- It is beneficial to simplify the structure of the die. The number of decomposed sections should be as little as possible. The shape of the punch and concave dies formed after recombination should be simple, regular, with sufficient strength. It should be easy to process, as shown in Figure 1-3.
- The cutting edge decomposition should ensure the shape, size, precision, and use requirements of the product parts.
- After the decomposition of the inner contour, the connection between the sections should be straight or smooth.
- Segmented lap contact should be as little as possible. Lap contact position to avoid the weak parts of the product parts and important parts of the shape, in an unobstructed position.
- The straight edge with tolerance requirements and the edge with sliding fit requirements in the process of use should be cut at a time, and should not be divided. To avoid the accumulation of errors. If surface A, as shown in Fig. 1-4(a), is the mating surface in the use process. It is better to choose the cutting edge decomposition as shown in Fig. 1-4(c).
- Complex shape and narrow groove or long and thin buttock part of the best decomposition, the best decomposition of complex shape.
- The burr direction should be decomposed when there are different requirements.
- The cutting edge decomposition should consider the processing equipment conditions and processing methods, to facilitate processing.
The decomposition and reorganization of the cutting edge are not unique, as shown in Fig. 1-4. The design process is flexible, empirical, and difficult, so several schemes should be considered in the design. And the optimal scheme should be selected through comprehensive comparison.
The Basic Form of Sectional Lap Joint in Contour Decomposition
After the decomposition of the inner contour, lap joints are bound to form between each segment. Improper decomposition will lead to quality problems such as burr, wrong teeth, sharp Angle, collapse Angle, uneven and non-smooth lap joints.
There are three common forms of lap joints.
- Handover, as shown in Fig. 1-5 (a). The handover refers to the blank contour after decomposition and reorganization, the cutting edge between each other. There is a small amount of overlap.
Cutting edge decomposition according to the handover way is more favorable to ensure the connection quality of the handover joint. It is widely used. Handover quantity should be greater than 0.5 times the thickness of the material; If not limited by the size of the handover hole, the handover amount can reach 1~2.5 times the thickness of the material.
- Flat connection, as shown in Fig. 1-5 (b). A flat connection is to divide the straight edge of the parts into two cutting. Two cutting edges are parallel and collinear, but do not overlap.
When flat joint, the step precision, punch, and concave die manufacturing precision is higher requirements. Which is easy to produce burr, wrong teeth, unequal quality problems. In addition to must be arranged like this, should try to avoid using this lap method. The direct pin should be set near the flat connection. If the workpiece is allowed, the width of the second blanking should be increased. And the punch should be trimmed to make a small bevel (generally 3~5).
- Cut, as shown in Fig. 1-5 (c). Cutting is in the blank arc section of sectional punching lap form, that is, in the first station punching a part of the arc section. Then cut off the rest of the subsequent station, before and after the two sections should be tangent.
The main content of the working procedure layout needs to be solved in the following aspects.
Process Determination and Sequencing
The sequence of the process is in favor of the next process for the principle, do easy process first, then difficult, first punch plane shape and then punch three-dimensional shape.
The Process Layout of Stage Blanking
- For punching parts with holes, punching first and punching later, as shown in Fig. 1-8.
- Try to avoid using the punch and concave dies with complex shapes, that is, decompose the complex shaped holes or shapes and adopt the method of segmented excision, as shown in Fig. 1-4 and Fig. 1-5.
- The relative size of parts with strict requirements should be rushed out at the same station. If it is not possible to rush out at the same station, you can arrange to rush out at a nearby station, as shown in Fig. 1-9.
- The contours with high size and shape requirements should be flushed out at the rear station.
- The punching of the weak part should be arranged at the earlier station.
- When the distance from the hole to the edge is small and the accuracy of the hole is high, if the hole is punched first and then the shape is punched, it may lead to the deformation of the hole. In this case, the outer edge of the hole should be flushed out before punching, as shown in Fig. 1-9.
- For the punching process with a large contour perimeter, the punching process should be arranged in the middle as far as possible to make the pressure center coincide with the geometric center of the mold.
The Process Layout of Progressive Bending
- For bending parts with holes, it is generally necessary to punch holes first, then punch and cut off the surrounding materials of bending parts, then bend them again, and finally remove the rest of the waste to separate the workpiece from the strip, as shown in Fig. 1-10. However, when the hole is close to the bending deformation area and accuracy is required, it should be bent before punching to prevent the hole from deformation.
- When bending, the outside should be bent first and then the inside, as shown in Fig. 1-11. When the bending radius is too small, a shaping procedure should be added.
- The direction of the burr should generally be located inside the bending zone to reduce the risk of bending rupture and improve the appearance of the product.
- The bending line should be arranged in a direction perpendicular to the fiber. When the parts are to be bent in the mutually perpendicular direction or several directions, the bending line should be at an Angle of 30°~60° with the fiber direction of the strip material.
- In one station, the degree of bending deformation should not be too large. For complex bending parts, they should be decomposed into a combination of simple bending processes, which are formed by successive bending, as shown in Fig. 1-11. For complex bending parts requiring high precision, the precision of the workpiece should be guaranteed by the shaping procedure.
- When two bending parts of a part have dimensional accuracy requirements, they should be formed at the same station to ensure dimensional accuracy.
- For small single-angle bending parts, to avoid carrier deformation and lateral sliding during bending, they should be bent in pairs and then cut apart.
- As far as possible, the direction of punch stroke is taken as the bending direction to simplify the mold structure.
The Layout of the Process of Progressive Deep Drawing
In the process of multi-station progressive deep drawing, unlike single process deep drawing in the form of a single piece to feed into the blank, it is through the material with the carrier, laps, and blank together, in the form of components in a continuous feed, progressive deep drawing. This is shown in Fig. 1-12. However, due to the lack of intermediate annealing in progressive drawing, the material is required to have high plasticity. And because of the mutual restriction between the workpiece in the process of progressive deep drawing, the deformation degree of each station can not be too large. Due to the large amount of workpiece waste left between the parts, the material utilization rate is reduced.
According to the deformation zone of the material and the separation of the strip, the progressive deep drawing can be divided into two technological methods: without and with technological notches.
- Progressive drawing without cutting, that is, drawing on the whole strip material, as shown in Fig. 1-12 (a). Due to the mutual constraints between the two adjacent deep working parts, the material is difficult to flow in the longitudinal direction, and it is easy to crack when the deformation is large.
Therefore, the degree of deformation of each process can not be large, so the number of stations is more. The advantage of this method is to save materials.
Due to the difficulty of material longitudinal flow, it is only suitable for drawing parts with large relative thickness [ ( t/D ) × 100 > 1 ], small relative flange diameter ( dt /d = 1.1 ~ 1.5 ) and low relative height h/d.
- Progressive drawing with notches is to cut all openings or slits adjacent to the part, as shown in Fig. 1-12 (b). The interaction and constraint of the two adjacent processes are small, and the drawing at this time is similar to that of a single blank. Therefore, the drawing coefficient of each process can be smaller, that is, the number of drawings can be less, and the mold is simpler. But the raw material consumption is more. This kind of drawing is generally used for drawing more difficult, that is, the relative thickness of the parts is small, the relative flange diameter is larger and the relative height is larger.
Empty Station Design
The empty station is designed to ensure the strength of the die and facilitate the installation and adjustment of the punch and the installation of a special structure or a possible increase in the need for a station. The principle is as follows.
- For small step spacing (less than 8mm), more empty stations should be set; for large step spacing (more than 16mm), more empty stations should not be set.
- More empty stations can be set for the positive pin positioning; otherwise, fewer empty stations should be set.
- For high-precision punching parts, fewer empty stations should be set.
By controlling the total number of stations, the size of the multi-station progressive die with a large profile size can be controlled to reduce the cumulative error and improve the precision of punching parts. In the process layout, as shown in Fig. 1-13, the fourth and sixth stations are vacancies.
In the design of a multi-station progressive die, the working procedure parts are transferred to each working station for blanking and forming processing, and the working procedure parts keep stable and correct positioning in the dynamic feeding process, which is called the carrier. The Carrier and general stamping layout of the edge have similar, but the role is completely different. The edge is set to meet the process requirements of cutting the workpiece from the strip material, and the carrier is designed to carry the working procedure on the strip material to the subsequent station. According to the shape of the punching piece, deformation properties, material thickness, and other different conditions, the carrier generally has the following forms.
Edge Material Carrier
Edge material carrier is a form of using the scrap material as a carrier. At this time, there are scrap materials around the whole workpiece. This carrier has good stability and simplicity, as shown in Fig. 1-14.
A single side carrier is referred to as a single carrier, which is a material with a certain width set aside on one side of the strip material and is connected with the working procedure in an appropriate position to realize the carrying of the working procedure parts. A single carrier is suitable for punching parts with thickness t above 0.5m, especially for parts with bending at one end or in several directions. This is shown in Fig. 1-13.
A bilateral carrier is also called the standard carrier, referred to as both side carrier. It is a material with a certain width set apart on both sides of the material to carry the working procedure parts, and the working procedure parts are connected in the middle of the two sides of the carrier, so the double carrier is more stable than the single carrier and has higher positioning accuracy. This carrier is mainly used for thin material ( t ≤ 0.2mm ), the workpiece precision is higher occasions, but the utilization rate of the material is reduced, often in a single arrangement. This is shown in Fig. 1-15.
The intermediate carrier is similar to the unilateral carrier, but the carrier is located in the middle of the strip, as shown in Fig. 1-16. It is less material than a single-sided carrier and double-sided carrier. It is widely used in the process layout of bending parts. It is most suitable for the parts with material thickness t greater than 0.2mm and symmetrical bending on both sides. The width of the intermediate carrier can be flexibly controlled according to the characteristics of the parts, but should not be less than the width of the single carrier.
Selection of Positioning Form
Because the multi-station progressive stamping is to distribute the stamping process of the product in several stations to complete, the punching edge of the front and rear station process parts can be accurately connected and matched, which requires that the process parts can be accurately positioned in each station.
Positioning can be divided into vertical and horizontal, vertical and bar feed direction is the same, and horizontal and bar feed direction is vertical. General vertical positioning includes distance and guide, and transverse positioning guide material.
The positioning methods commonly used in the progressive die are shown in Table 1-1.
|Positioning way||Legend||Scope of application|
|Stop pin||t > 1.2mm, large size product accuracy requirements (IT10~IT13)Simple shapeManual feeding|
|Side blade||Single side blade||t = 0. 1-1.5 mmIT11 ~ TT14 precisionLocation number 3-10|
|Side blade||Both side blade||t = 0. 1-1.5 mmIT11 ~ TT14 precisionLocation number 3-10|
|Automatic feeding mechanism||The machine is equipped with an automatic feeding mechanism|
|Guide pin||It requires high precision and is used in combination with rough positioning form|
Side Edge Positioning
Positioning with the side blade should generally be arranged in the first position, the purpose is to make the beginning of the stamping material can be sent according to a certain step distance. When the side blade works, it rushes a narrow strip to the side of the strip. The length of the strip is equal to the step distance, which is used as the feed distance.
There are 3 types of side blade shapes, as shown in Fig. 1-17. As shown in Fig. 1-17 (a), it is a rectangular side blade, which is simple to manufacture. However, after the side blade becomes blunt, burrs will appear on the edge of the material after cutting, affecting the feeding and accurate positioning of the material. Fig. 1-17 (b) shows the toothed side blade, which overcomes the shortcoming of the rectangular side blade but is difficult to manufacture.
As shown in Fig. 1-17 (c), the sharp corner edge is inserted into the notch of the sharp corner edge to control the step distance. Although the material is saved, the bar material needs to be moved back and forth during blanking, which is inconvenient to operate, so it is mostly used in the blanking of precious metals.
When the stamping production batch is large, the double edge is used, and the double edge can be placed diagonally or symmetrically. As shown in Fig. 1-18. Adopt a double edge, the precision of the workpiece is higher than that of a single edge. When the strip is detached from one side blade, the second side blade can still set the distance.
The thickness of the side blade is generally 6~10 mm, and the length is the length of the material feeding distance. Material can be made of T10, T10A, CrL2 steel, quenching hardness of 62~64 HRC.
Guide Pin Positioning
As shown in Fig. 1-19, the positioning of the leading pin is to correct the position of the bar by inserting the leading pin installed on the upper die into the leading hole on the bar, to keep the correct relative position between the punch, the die, and the working parts.
- Diameter of leading pinhole
The leading pinhole of the progressive die is mostly arranged on the carrier of the strip (it can also be arranged on the hole of the process part).
Therefore, the size of the hole diameter of the leading pin directly affects the utilization rate of the material. It can not be too large, but it can not be too small, otherwise, the strength of the leading pin can not be guaranteed. When determining the diameter of the guide hole, factors such as sheet thickness, material, hardness, blank size, carrier form and size, layout scheme, guideway, product precision requirements, and structural characteristics, processing speed, and so on should be comprehensively considered. Table 1-2 is the empirical value of the diameter of the leading hole.
Side edge of bar die block side edge.
|T (mm)||dmin (mm)|
|0.5≤ t ≤1.5||2.0|
- Position of leading pinhole
The positive pin can be positive in two ways: direct and indirect. The so-called direct guide is to use the hole of the product part itself as the guide hole, the guide pin can be installed in the punch, but also can be set up separately. An indirect guide is the use of a carrier or wastes out of the special guide pinhole to guide.
The leading pinhole is generally out of the first station, and the leading pin is immediately following the second station. After that, it should be set at an equal distance every 2~4 stations. The leading pinholes can be set double or single, depending on the shape of the workpiece and the structure of the die. When the strip width is large, the leading pin holes should be double.
The leading pin is in the fine positioning of the working procedure. Sometimes it will cause the deformation or scratch of the guide hole, so the product parts with high precision and quality requirements should avoid the direct guide on the workpiece.
Mixed Positioning of Side Edge and Guide Pin
When the side blade is mixed with the guide pin, the side blade is used for rough positioning and the guide pin for precise positioning. Fig. 1-20 shows a schematic diagram of the combination of the two. At this time, the stamping of the side edge and the guide pin hole should be placed in the first position, and the guide pin should be set in the position after the punching guide hole.
Example of Layout
Layout Design Process
The parts shown in Fig. 1-21 are taken as examples to illustrate the design process of the layout. Because it is a curved piece, first of all, should find out its expansion diagram (if the blanking piece, this step can be omitted; For deep drawing parts, it is necessary to calculate the size of blanks, The Times of drawing, the size of semi-finished products and the width of strips after each drawing before the layout, and then according to the first layout of blanks, then the outline design of punching cutting edge, and the final process layout steps.
- Blank layout
Fig. 1-22 shows the four layout ways of the blank after the expansion of the bending parts. The entire workpiece area is about 1133.1mm (including the square hole in the middle of the workpiece and the small holes at both ends). After calculation, the material utilization ratio of each layout is respectively: ηa = 1133.1/(64 x 26.6) = 0.67, ηb = 1133.1/(26 x 64.3) = 0.68, ηc = 1133.1/(25 x 64.3) = 0.7, ηd = 1133.1/(52 x 30.1) = 0.72.
Thus, Fig. 1-22 (a) has the lowest layout utilization rate, and Fig. 1-22 (d) has the highest layout utilization rate. However, Fig. 1-22 (d) makes the workpiece tilt, which requires that the modules on the progressive die should also be set. The mold manufacturing process is complex, as shown in Fig. 1-22 (c) Although the layout has a high material utilization rate because the workpiece is only connected in the middle, it is not conducive to the stable feeding of subsequent stations. It is generally believed that the feeding stability of the layout in Fig. 1-22 (b) and Fig. 1-22 (d) is good, so the layout as shown in Fig. 1-22 (b) is selected here.
- The shape design of the cutting edge
According to the fixed blank layout, the cutting edge decomposition diagram as shown in Fig. 1-23 can be designed. First punch the positive hole, two small holes, and the middle square hole, so that you can use the positive pinhole for positioning in the subsequent processing. Because the four sides should be bent, it is necessary to separate the bending part from the strip material before bending. To simplify the mold structure and ensure mold strength, the connecting groove between the two working parts is rushed out in two steps. Then just cut off the parts that are attached to the two sides of the strip to bend it.
- Process layout
Based on the above layout design, design the process layout drawing as shown in Fig. 1-24. There are 6 working stations: punching and guiding hole, two small holes, and the middle square hole at the first working station; Open position at the second station; The third and the fourth working position in two steps out of the connection between the two workpieces; The fifth is an empty seat. The 6th position bends and separates the workpiece from the material.
After the layout design is completed, it is finally expressed in the form of a layout drawing. Process layout drawing can be drawn according to the following steps.
- First, draw a horizontal line, and then draw the center of each station according to the determined input distance.
- From the first station, draw the content of stamping processing. Such as the first station incision, only draw the shape of the incision; If the first station is to punch the positive pinhole or the side edge distance, the positive pinhole or the blanking edge shall be drawn.
- To draw the processing content of the second station, at this time the first station out of the hole or cut mouth should also be drawn.
- Draw the processing content of the third station, even if it is empty, should also be drawn, and the shape processed by the first and second station should also be expressed here.
- And so on, until all the stations are drawn, the last step is blanking, only need to draw the blanking shape.
- Check whether the content of each station is drawn correctly, and modify the incorrect place.
- After the check and then draw the shape of the strip, if the layout using molding side edge positioning, should draw the processing shape of the side edge, this time the shape and size of the strip will be determined.
- For the convenience of map recognition, the processing content of each station can be drawn on the section line or painted with different colors.
- Label the necessary dimensions, namely, feed distance, material width, the diameter of the leading pin, width of side edge, etc., and note the feeding direction, number of stations, and stamping process name of each station.
A concrete example of a layout drawing is shown in Fig. 1-24.