Punching Machine

How to Design Multi-station Progressive Die

How to Design Multi-station Progressive Die

Estimated reading time: 25 minutes

Classification of Multi-station Progressive Die Parts

The structure of the multi-station progressive die is complex, and the number of parts is relatively large. The general multi-station progressive die is composed of dozens or even hundreds of parts. According to the different functions of the mold parts in the mold, the mold parts can be divided into working parts and auxiliary parts, as shown in Table 1-1.

UnitFunction The major parts
Working partsStamping processing Punch die, concave die
 Discharge Discharge plate, discharge screw, the elastic element
Auxiliary partsPositioningX DirectionBlocking pin, side blade
 PositioningY DirectionGuide plate, side pressure device
 PositioningZ DirectionFloating roof pin, etc
 PositioningPrecision positioningThe guide pin
 GuideExternal orientationGuidepost, guide sleeve
 GuideInternal guidanceSmall guidepost, small guide sleeve
 Fixed Fixed plate, upper and lower die seat, die handle, screw, pin
 Other Backing plate, limit plate, safety testing device, etc
Table 1-1 Component of Multi-station Progressive Die

Design of Working Parts for Multi-station Progressive Die

Working parts mainly refer to punch and die. The working parts of the multi-station progressive stamping die and other stamping processes are the same in many places, and the design method is the same.

The Punch Design for Multi-station Progressive Die

General short punch can be selected according to the standard or according to the conventional design. In the multi-station progressive die, there are many punching holes punch, punching narrow long groove punch, breakdown punching punch. These punches should be based on specific punching requirements, the thickness of the material to be blanked, punching speed, punching clearance and punch processing methods, and other factors to consider the structure of the punch and punch fixing method.

For punching a small punch, usually, increase the diameter of the fixed part, reduce the length of the cutting edge to ensure the strength and stiffness of the small punch. When the diameter difference between the working part and the fixed part is too large, the multi-step structure can be designed. The transition part of each step must be connected smoothly with a circular arc, and knife marks are not allowed. Especially small punches can be used in a protective sleeve structure. About ф0.2 of the small punch, the top of the protective sleeve is about 3.0-4.0mm. The discharge plate should also be considered to play a guiding and protective role on the punch to eliminate the effect of side pressure on the punch and affect its strength. Fig. 1-1 shows a common small punch and its assembly form.

Fig. 1-1 Small Punch and Its Assembly Form(a-e)
(a)          (b)          (c)          (d)         (e)
Fig. 1-1 Small Punch and Its Assembly Form(a-e)
Fig. 1-1 Small Punch and Its Assembly Form (f-j)
(f)         (g)           (h)           (i)           (j)
Fig. 1-1 Small Punch and Its Assembly Form (f-j)

The waste after punching is pasted on the end face of the punch and taken out of the die with the return of the punch and falls on the surface of the die. If the waste is not removed in time, the die will be damaged. Measures should be taken into consideration in the design to prevent waste material from running up the punch. Therefore, the punch above ф0.2 should be used to eliminate the waste punch. Fig. 1-2 shows a punch structure with ejector pins, using elastic ejector pins to remove waste from the punch end face. It also can be added in the punch center vent, reduce the punching waste and punching punch on the end face of the ‘vacuum pressure’, so that the waste is easy to fall off.

Fig. 1-2 Punch With Ejection Pin
Fig. 1-2 Punch With Ejection Pin

It should be pointed out that the working order of the punching bending multi-station progressive die or the punching and drawing multi-station progressive die is generally that the rectifying pin guides the rectifying material first after the elastic discharge plate compresses the material, the bending or drawing begins, and then the punching, and finally the bending or drawing work ends. Blanking is performed after the forming work has begun and completed before the forming work is completed. So punching punch and forming punch height is not the same, to the correct design punching punch and forming punch height size.

The Concave Die Design for Multi-station Progressive Die

The design and manufacture of the multi-station progressive die are more complicated than punch dies. The structure of the concave dies commonly used types are integral, block, and block. The integral concave die is not suitable for the multi-station progressive die because of the limitation of the precision and manufacturing method of the die.

Block Type Concave Die

The combination form of block die is divided into two structures because of the different processing methods used. The concave die is assembled by the block of the discharge machining, and the structure of the concave die is mostly combined in parallel. If the contour of the concave model hole is segmented for forming grinding, and then the ground blocks are assembled on the required pads, and then inserted into the concave die frame and fixed with bolts, the structure is a forming grinding assembly combined concave die. Fig. 1-3 shows a schematic diagram of the structure of bending parts with parallel composite die.

Fig. 1-3 Parallel Composite Die Structure
Fig. 1-3 Parallel Composite Die Structure

The block hole manufacturing is completed by electric processing, and the processed block is installed on the cushion plate and fixed on the lower die seat. As shown in Fig. 1-4, this part adopts the concave die structure of grinding assembly. The assembly block is fixed on the cushion plate with screws and pins, inserted into the die frame, and installed on the concave die seat. Round or simple-shaped holes can be nested with circular concave dies. When a block needs to be corrected due to wear and tear, it can continue to be used only by replacing the block.

Fig. 1-4 Grinding Assembly Die
Fig. 1-4 Grinding Assembly Die

Grinding block assembly die because the block is all through grinding and grinding, the block has higher precision. To ensure the interrelated dimensions during assembly, the grinding process can be added to the matching surface, and spare parts can be made for the wearing parts.
The fixing of block die mainly has the following 3 forms.

  • Planar stationary type

The planar fixing means to insert each block of the die on the plane of the fixing plate according to the correct position, and locate and fix it on the backing plate or the lower die seat with the positioning pin (or positioning key) and screws respectively, as shown in Fig. 1-5. This form is suitable for the larger block die and fixed according to the section method.

Fig. 1-5 Planar Stationary Type
Fig. 1-5 Planar Stationary Type
  • Grooved fixed type

Reclaimed groove fixing is to insert the block die directly into the groove of the fixing plate, the depth of the die on the fixing plate is not less than 2/3 of the thickness of the block, each block does not need a positioning pin, but at both ends of the recessed groove with a key or wedge positioning and screw fixing, as shown in Fig. 1-6.

Fig. 1-6 Straight Slot Fixed Type
Fig. 1-6 Straight Slot Fixed Type
  • Frame hole fixed

There are two types of frame hole fixation: integral frame hole and combined hole, as shown in Fig. 1-7. Fig. 1-7 (a) is the integral frame hole, and Fig. 1-7 (b) is the composite frame hole. When the whole frame hole is fixed concave die block, the maintenance, assembly, and disassembly of the die are more convenient. When the bulging force of the block is large, the stiffness and strength of the combo frame connection should be considered.

Fig. 1-7 Frame Hole Fixed Type
 (a)                              (b)
Fig. 1-7 Frame Hole Fixed Type

Inlay Block Type Concave Die

The inlay block die is shown in Fig. 1-8. The feature of the inlay block type die is that the inlay block cover is made into a round shape. And can choose standard inlay block, machining hole. Spare parts can be replaced quickly after the inlay block is damaged. The jig boring machine and the jig grinder are often used to process the mounting holes of the block fixing plate. When the working hole of the inlay block is non-circular, because the fixed part is round, the anti-rotation must be considered.

Fig. 1-8 Inlay Block Die
Fig. 1-8 Inlay Block Die

Fig. 1-9 shows the commonly used concave die inlay block structure. Fig. 1-9 (a) is a monolithic inlay block. Fig. 1-9 (b) is a special-shaped hole, which is divided into two parts (the direction of division depends on the shape of the hole) because it cannot grind the mold hole and the leakage hole. Considering that its joint should be favorable for cutting and convenient for grinding, it is positioned by keys after insert into the fixing plate. This method is also applicable to the guide sleeve of the special-shaped hole.

Fig. 1-9 Concave Die Inlay Block
 (a)                        (b)
Fig. 1-9 Concave Die Inlay Block

Positioning Mechanism Design for Multi-station Progressive Die

The positioning of process parts in multi-station progressive die includes distance setting, material guide, and floating roof.

Distance Fixing Mechanism Design

The main purpose of distance determination is to ensure that each working position can be equally spaced forward according to the design requirements. The commonly used distance determination mechanism includes the retaining pin, the side edge, the guiding pin, and the automatic feeding device.

The retaining pin is mainly used for the manual feeding progressive die with low precision requirements. The structure and use method of the retaining pin is exactly the same as that of the common stamping die, which will not be described here.

In the precision progressive die, the stopper pin is not used for positioning. The design often uses the method of locating with the leading pin and the side edge. The side edge is used for the initial positioning, and the leading pin is used for the fine positioning.

Side Blade

The basic form of the side blade is divided into two types according to whether the side blade enters the die hole or not. Non-guided direct-in side edges and guided side edges, as shown in Fig. 1-10 (a), (b), direct-in side edges are generally suitable for stamping thin materials with a thickness of less than 1.2mm; Guided side edges are often used in dies with complex punching shapes and side edges are also used to remove waste materials. The cross-section shape of each side blade has four forms as shown in Fig. 1-10.

Fig. 1-10 Basic Form of Side Blade (a)
(a) Unguided side edges
Fig. 1-10 Basic Form of Side Blade (b)
(b) Guided side edges
Fig. 1-10 Basic Form of Side Blade

Guide Pin

The guide pin is the most widely used distance setting method in a progressive die.

When the guide pin is introduced into the material, the positioning accuracy of the material must be guaranteed, and the guide pin can be smoothly inserted into the guide hole. The clearance is too large, the positioning accuracy is low; If the fit clearance is too small, the wear of the leading pin will be aggravated and the irregular shape will be formed, which will also affect the positioning accuracy. The diameter of the leading pin is shown in Table 1-2.

tDiameter of guide pinNote
≤ 0.5D = dp − 0.125tThere are strict requirements for the accuracy of the step
> 0.5D = dp − 0.0.5tThere is no strict requirement for the accuracy of step
≥ 0.7D = dp − 0.02tThere are strict requirements for the accuracy of the step
Note: dp ― Diameter of punch for punch hole of punch guide.
Table 1-2 Guide Pin Hole Diameter               Unit: mm

The front end of the lead pin should be protruded on the lower plane of the discharge plate, as shown in Fig. 1-11. The value range of outburst x is 0.8t < x <1.5t. A larger value is taken for thin material and a smaller value is taken for thick material. When t=2mm or more, x=0.6t.

Fig. 1-11 Protrusion of Leading Pin 1 ― Lead pin; 2 ― Bending punch; 3 ― Punching punch
Fig. 1-11 Protrusion of Leading Pin
1 ― Lead pin; 2 ― Bending punch; 3 ― Punching punch

The fixing method of the leading pin is shown in Fig. 1-12. Among them, Fig. 1-12 (a) shows that the leading pin is fixed on the punch. Fig. 1-12 (b) shows that the leading pin is fixed on the discharge plate, and Fig. 1-12 (c), (d),(e), (f), and (g) shows that the leading pin is fixed on the fixing plate.

Fig. 1-12 Installation Form of Guide Pin
(a)    (b)    (c)     (d)      (e)     (f)     (g)
Fig. 1-12 Installation Form of Guide Pin

When the pin is used in many places in a die, the protruding length x, diameter size, and head shape must be the same so that all the pins bear approximately the same load.

Guide and Floating Roof Device Design

Multi-station progressive stamping due to the strip material after blanking, bending, drawing, and other deformation, in the thickness direction of the strip, will have different heights of bending and protrusion, to smoothly feed into the strip material, must have been formed with the material jacked up, so that the protrusion and bending part away from the die wall and slightly higher than the die working surface. The structure that makes the belt jacking up is called the floating roof device, which is often used together with the guide parts of the belt (the guide plate) to form the guide system of the strip, as shown in Fig. 1-13.

Fig. 1-13 The Floating Roof Device and the Guide Plate Constitute the Strip Guide System
Fig. 1-13 The Floating Roof Device and the Guide Plate Constitute the Strip Guide System

Fig. 1-14 shows a common floating roof actuator, which consists of floating roof pins, springs, and plugs. As shown in Fig. 1-14 (a), the structure of the ordinary floating top device only acts as the floating top bar leaving the concave die plane, so it can be set at any position, but it should be paid attention to as far as possible in the material plane near the forming part, and the size of the floating top force should be uniform and appropriate. Fig. 1-14 (b) is the structure of the sleeve floating roof, the floating roof in addition to floating the top strip away from the concave die plane, but also plays the role of protecting the guide pin, should be set in the corresponding position of the guide pin, stamping, the guide pin into the inner hole of the sleeve floating roof pin. Fig. 1-14 (c) shows a trussed floating roof which not only floats the strip away from the die plane but also guides the strip. At this time, the guide plate should not be installed on the partial or full length of the mold, but by the groove floating top pin installed on both sides (or one side) of the working hole of the concave die parallel to the feeding direction with a guide groove.

Fig. 1-14 Structure of the Floating Roof
(a) Ordinary Floating roof pin (b) Sleeve Floating Roof Pin (c) Trough Floating Roof Pin
Fig. 1-14 Structure of the Floating Roof

The height of the lifting bar of the floating roof is determined by the maximum molding height of the product, as shown in Fig. 1-13.

Guide Plate Design

The multi-station progressive die is the same as the ordinary punching die, which also uses a guide plate to guide the strip along the feeding direction. It is installed on both sides of the upper plane of the die and parallel to the centerline of the die. The guide plate in the multi-station progressive die has two forms: one is the ordinary type guide plate, its structure, and working principle is the same as the ordinary die, mainly suitable for low speed, manual feeding, and the plane blanking continuous die; The other is a guide plate with a boss, as shown in Fig. 1-15. It is mostly used for high-speed, automatic feeding, and is mostly a three-dimensional stamping continuous die with forming and bending. The boss is designed to ensure that the strip always moves within the guide plate during the floating feeding process.

Fig. 1-15 Guide Plate with Boss
Fig. 1-15 Guide Plate with Boss

Unloading Device Design

Before the start of the role of the discharging device in addition to the stamping pressure belt material, to prevent the punch stamping or due to the different order when the stress caused by uneven pick-up channeling, and ensure the smooth discharge after stamping, it is important to stripper plate for each stage of punch (especially small punch) in the lateral force, precise guidance and effective protection. The unloading device is mainly composed of an unloading plate, elastic element, unloading screw, and auxiliary guide parts.

The Structure of the Discharge Plate

The spring pressure discharge plate of the multi-station progressive die is fixed on a matrix with larger stiffness by piecewise assembly structure to ensure the dimensional accuracy, position accuracy, and fit clearance of the mold hole because of many holes and complex shape.

Fig. 1-16 shows a discharge board composed of five pieces. The matrix is opened through the groove according to the mating relationship of the base hole system, and the two blocks at both ends are pressed into the matrix through the groove according to the requirements of the position accuracy and fixed with screws and pins respectively. The middle three blocks are directly pressed into the channeling after grinding and connected with the matrix only by screws. The size of the installation position is adjusted by grinding the joint surface of each section, to control the size accuracy and position accuracy of each hole.

Fig. 1-16 Composite Ejector Plate
Fig. 1-16 Composite Ejector Plate

Guide Form of Discharge Plate

Because the unloading plate has the role of protecting the small punch, the unloading plate is required to have high motion accuracy, so the auxiliary guide parts small guideposts, and small guide sleeves should be added between the unloading plate and the upper die seat, as shown in Fig. 1-17. When the stamping material is thin, and the precision of the die is high, and the number of stations is more, the ball-type guide post guide sleeve should be selected.

Fig. 1-17 Small Guide Pins and Guide Bushes
Fig. 1-17 Small Guide Pins and Guide Bushes

The Installation Form of Discharge Plate

The mounting form of the discharge plate shown in Fig. 1-18 is a common structure in the multi-station progressive die. Unloading plate pressure force, unloading force is installed by unloading the plate above the uniform distribution of spring compression. Because the unloading plate and the punch with the gap are only 0.005mm, so the installation of the unloading plate is more troublesome, when unnecessary, as far as possible not to unload the unloading plate from the punch. Considering that the discharge plate is not removed from the punch when grinding, and the discharge plate is lower than the punch edge end face for grinding, the spring can be fixed in the upper die and the screw plug limit structure.

When grinding, as long as the screw plug is rotated, the spring can be taken out. If the casing combined type is adopted for the unloading screw, the position of the unloading plate relative to the punch can be adjusted by repairing the casing size, and the unloading plate can be adjusted by repairing the gasket to achieve the ideal dynamic parallelism (relative to the upper and lower die) requirements. As shown in Fig. 1-18 (b), an internally threaded discharge screw is used. The spring pressure is transmitted to the discharge plate through the discharge screw.

Fig. 1-18 Installing a Discharge Plate
Fig. 1-18 Installing a Discharge Plate
1 – Upper die seat; 2 – Screw; 3 – Gasket; 4 – Pipe sleeve; 5 – Discharge plate; 6 – Unloading board block; 7 – Screw; 8 – Spring; 9 – Fixed plate; 10 – Unloading pin

To press the head and the end of the material, so that the unloading plate smooth movement, pressure balance, can be installed in the appropriate position of the unloading plate, to ensure the balance of the unloading plate movement.

Unloading Screw

The discharge plate is mounted on the upper die with discharge screws. The discharge screw should be symmetrical distribution, the working length should be strictly consistent. Fig. 1-19 shows the discharge screws for the multi-position progressive die. Male thread type: the accuracy of shaft length is ± 0.1mm, often used in less working station common progressive die; Internal thread type: the accuracy of shaft length is ± 0.02mm, and the working length of a group of discharge screws can be kept consistent by grinding the end face of the shaft; Combined type: the shaft length accuracy can be controlled within ± 0.01mm by the combination of casing, bolt, and washer.

Internal thread and combined type also have a very important feature, when punching punch after a certain number of grinding and then grinding, the length of the unloading screw working section must be worn to the same value, to ensure the relative position of the unloading plate pressing surface and punching punch end face. It is difficult to grind the length of the discharge screw with an external thread.

Fig. 1-19 Types of Discharge Screws
Fig. 1-19 Types of Discharge Screws

Design of Auxiliary Devices

The Die Frame

The progressive die frame requires good rigidity and high precision, so the upper die seat is usually thickened by 5~10 mm, and the lower die seat is thickened by 10~15 mm (compared with GB/T 2851~2852-1990 standard die frame). At the same time, to meet the requirements of rigidity and guiding precision, the progressive die is often used four guide pillar die frame.

The die frame guide of the precision progressive die is generally guided by ball guideposts (GB/T 2861.8-1990). There is no gap between the ball (column), the guideposts, and the guide sleeve. The interference fit is often used, and the interference amount is 0.01mm ~ 0.02mm (the diameter of the guide post is 20~ 76mm). The cylindricity of the guide post guide sleeve is 0.003mm, and the perpendicularity of the axis line and the template is 0.01:100 for the guidepost. Fig. 1-20 shows a new type of guidance structure in use at home and abroad. The roller surface is composed of 3 sections of arc, the two sections of convex arc 4 near the two ends match the inner diameter of the guide sleeve (the same curvature), and the concave arc 5 in the middle matches the outer diameter of the guide pillar, and the relative motion of guide sleeve on guide pillar is achieved through the roller. This roller guide uses line contact instead of ball guide the large eccentric load but also improves the guide accuracy and life, increased rigidity, its interference is 0.003~0.006 mm.

Fig. 1-20 Roller Guide Structure
Fig. 1-20 Roller Guide Structure
1 – Guide pillar; 2 – Roller keeping ring; 3 – Guide sleeve; 4、5 – Roller surface

To facilitate grinding and assembly and disassembly, the guide pillar is often made into a removable type, that is, a fixed taper (its taper is 1:10) or a fixed press plate (the length of the matching part is 4~5 mm, according to T7/ H6, the vacating part is 0.04 mm smaller than the fixed part, as shown in Fig. 1-21. The guide column material is commonly used GGr15 to harden 60-62 HRC, and the best roughness can reach Ra value of 0.1 μm. At this time, the wear is minimum and the lubrication is optimal. For easy replacement, the guide sleeve is also pressed plate fixed, as shown in Fig. 1-21 (d) and (e).

Fig. 1-21 Pressure Plate Detachable Guide Pin Guide Sleeve (a-c)
(a) Three Pressure Plates Press the Guide Posts (b) Screw Press Plate Tension Guide Posts (c) The Press Plate Compresses the Guide Posts
Fig. 1-21 Pressure Plate Detachable Guide Pin Guide Sleeve
Fig. 1-21 Pressure Plate Detachable Guide Pin Guide Sleeve (d-e)
(d) Three Pressure Plates Press the Guide Posts (e) Three Pressure Plates Press the Guide Posts
Fig. 1-21 Pressure Plate Detachable Guide Pin Guide Sleeve

Fixing Plate

The punch fixing plate of the multi-station slow advance die should not only be installed with multiple punches but also be installed in the corresponding position of the guide pin, inclined wedge, elastic unloading device, small guide column, small guide sleeve, etc., so the fixing plate should have enough thickness and certain wear resistance. The thickness of the fixed plate can be 40% of the designed length of the punch. Generally, 45 steel can be used for continuous die fixing plate, and the quenching hardness is 43 ~ 48 HRC. For the continuous die with high precision requirements, the fixing plate should be T10A, CrWMn, etc., with a quenching hardness of 52 ~ 56 HRC. When the punch is not often disassembled at low speed, the fixing plate can be unquenched.

The other auxiliary devices in the progressive die include the backing plate, the die handle, fastening screws, pins, etc., and the standard parts should be selected as far as possible.

Automatic Feeding Device

The purpose of using the automatic feeding device in the progressive die is to send the raw material (steel strip or wire) to the working position of the die correctly according to the required step distance and complete the preset stamping process in each different stamping station. The automatic feeding device commonly used in progressive die has a hook feeding device, roller feeding device, clamping feeding device, etc. At present, the roller feeding device and the clamping feeding device have formed a standardized stamping automation peripheral equipment.

Safety Testing Device

The automatic stamping production not only has to have the automatic feeding device, but also must have a safety detection device to prevent error in the production process, to protect the die and the press from damage.

The safety testing device can be arranged inside or outside the mold. When the fault affects the normal work of the die, the various sensors (photoelectric sensors, contact sensors, etc.) can quickly signal feedback to the braking part of the press, so that the press will stop and alarm, to achieve automatic protection.

In addition, to eliminate safety risks, in the mold design, also should design some safety protection devices. Such as to prevent parts or waste back and blockage, die surface parts or waste cleaning, etc. Fig. 1-22 shows the use of punch pins or compressed air to prevent the lifting and blocking off parts or waste.

Fig. 1-22 Use Punch to Prevent Parts (or Waste) Rebound and Blockage
Fig. 1-22 Use Punch to Prevent Parts (or Waste) Rebound and Blockage

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One thought on “How to Design Multi-station Progressive Die

  1. Edmar says:

    Make it easier for me to design multi-station progressive mold.

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