Ⅰ. Get the information you need
Perform a joint construction stamping technology analysis based on relevant data and perform a process audit and part standardization.
(1) Acquire drawings of product parts with specific technical specifications.
Gain an understanding of workpiece shape, size and accuracy requirements. Determine the critical hole size and location, as well as the critical surface, and perform an analysis to identify the part reference point.
It is important to note that the requirements for stamping parts are not set in stone.
With rapid advances in stamping technology, it is essential to take a comprehensive approach and apply various stamping technologies as needed in production. This can be achieved through rational selection of stamping methods, appropriate formulation of the stamping process and selection of an appropriate mold structure. This approach will not only meet the technical specifications of the product, but also meet the requirements of the stamping process.
(2) Gather process cards for workpiece processing.
By doing so, it becomes possible to examine the interconnection between front and back processes, understand the process requirements and the assembly relationships that must be guaranteed between the processes, etc.
(3) Determine the production batch of the part.
Part production has a significant impact on the efficiency of the stamping process. To do this, it is necessary to identify the type of mold, structure, material and other relevant details based on the production batch of parts and the quality specifications of the parts. Analyze the economics of the tooling process and the feasibility of producing public buildings and outline the profile of the stamping stage.
(4) Specify the conditions and specifications of the raw materials used for the workpiece (such as sheets, strips, coils, scrap, etc.), understand the nature and thickness of the material, determine whether to minimize waste by using less material for sampling, according to the manufacturing capacity of the parts, and initially identify the material specifications and the degree of precision.
Whenever possible, economical materials should be used, as long as they meet the functionality and stamping performance requirements.
(5) Analyze and design the fiber direction and burr direction requirements in the process.
(6) Assess the technical capabilities and condition of mold manufacturing equipment in the mold workshop and the availability of standard mold parts.
(7) Familiarize yourself with the equipment information or status of the stamping shop.
(8) After thoroughly studying and understanding the above information, formulate an initial design for the mold structure.
If necessary, make modifications to the established product design and process to better integrate product design, process, mold design, and manufacturing, resulting in more optimal results.
Ⅱ . Determine the process plan and mold structure type
Determining the process solution is a crucial step after analyzing the stamped parts process.
It involves:
(1) Carry out a process analysis based on the shape characteristics, dimensional accuracy and surface quality requirements of the workpiece to determine its main properties and the nature of basic processes such as material removal, punching, bending, deep drawing , flanging, and expansion.
The list of individual processes required for stamping can typically be derived directly from the product part drawing specifications.
(2) Establish the number of cases based on case calculations.
For stretched parts, calculate the number of deep undercuts. The number of times a bent or cut part must be processed will depend on its shape, size and accuracy requirements.
(3) Based on the deformation characteristics, dimensional accuracy and ease of operation of each process, determine the order of the processes.
For example, decide whether to pierce first and then fold or fold first and then pierce.
(4) Based on factors such as production batch size, precision requirements, mold manufacturing level, equipment capacity and others, determine the optimal combination of unique processes that have been organized.
For example, a compound stamping process or a continuous stamping process. Generally, thick, low-precision, small-volume, and large-sized punches are suitable for single-process production using simple dies.
Thin materials, small size and large number of punched parts are ideal for continuous production using a step-in die.
To stamp parts with high positional accuracy, it is advisable to use composite stamping dies.
After determining the nature, sequence and combination of processes, finalize the stamping process and the structure of the dies for each process.
Ⅲ. Perform the necessary process calculations
(1) Design the materials and determine the approximate dimensions.
(2) Calculate the punching pressure, including the force required for punching and cutting, bending, deep drawing, rotating, expanding, unloading, pushing and crimping. If necessary, also calculate the work and punching power.
(3) Determine the center of pressure of the mold.
(4) Calculate or estimate the thickness of each main part of the mold, such as the concave die, die retaining plate, pad, and the free height of the rubber or discharge spring.
(5) Specify the clearance of convex and concave molds and calculate the dimensions of the workpieces of convex and concave molds.
(6) For the deep drawing process, determine the deep drawing method (cutting or no cutting), calculate the number of deep drawing operations and the size of the semi-finished product in intermediate processes.
Special calculations may be required for certain processes, such as continuous strip deep drawing.
Ⅳ. The overall design of the mold
Using the above analysis and calculations, carry out a preliminary design of the mold structure (at this stage, it is usually sufficient to produce a sketch) and estimate the mold closing height. Describe the overall dimensions of the mold.
Ⅴ. Structural design of the main parts of the mold
(1) Workpiece parts, including the design of convex mold, concave mold, convex-concave mold and the selection of a fixed shape.
(2) Positioning of parts. There are several types of positioning devices commonly used in molds, such as adjustable positioning plates, fixed stop pins, movable stop pins and fixed side blades, which need to be selected and designed based on specific conditions.
In continuous mode, it is also necessary to consider whether to use an initial stop pin.
(3) Discharge and impulse device, including the selection of stiffness or elasticity, and the selection and calculation of springs and rubbers.
(4) Guide parts such as selecting a guide column, guide sleeve guide or guide plate guide, choosing an intermediate guide column, rear side guide column or diagonal guide column, and using a sliding guide sleeve or ball guide sleeve with steel balls, etc.
(5) Supporting and fixing parts, fixing parts, such as the selection of mold handle structure and upper and lower mold base.
Ⅵ. Select stamping equipment.
The selection of stamping equipment is a crucial aspect of process and mold design. A wise choice of equipment has a significant impact on part quality, increased productivity and operational safety. It also simplifies the mold design process.
The choice of stamping type mainly depends on process requirements and production volume.
The specification of stamping equipment is mainly determined by the process parameters and the size of the die structure. For hand crank presses, it must meet the following requirements:
(1) The nominal pressure of the press must be greater than the force of the stamping process, that is:
P stamp >∑P 0
To be more precise, the load curve of the stamping process must be within the allowable load curve of the press. For stamped parts, also calculate the deep drawing work.
(2) The loading height of the press must meet the mold closing height requirements.
(3) The press stroke must meet the part forming requirements. For presses used in the drawing process, the stroke must be greater than 2 to 2.5 times the height of the part in the process to accommodate the blank and remove the part.
(4) The size of the pressing table should be larger than the shape of the mold base under the mold, allowing the mold position to be fixed. Generally, each side should be greater than 50 to 70 mm. The size of the pouring hole in the press table must be larger than the size of the workpiece (or scrap).
Ⅶ . Draw a general image of the pattern
Mold diagrams, including part and component diagrams, are drawn in strict accordance with the drafting standards (GB/T4457~GB/T4460 and GB/T131-1993). However, in actual production, the drawing layout must be adapted to the mold's working characteristics and installation and adjustment requirements.
The general mold design includes:
(1) Main view:
A cross-sectional view of the mold in its working position is drawn. Typically, half of the view shows the situation before the start of the stamping process (when the press slider is in the upper stop position and the blank is placed), and the other half shows the state after punching is completed, the part work area is formed (or separated) and the press slider is in the lower stop position.
(2) Top view:
Typically, half of the top view shows the bottom half of the mold and the other half shows the top half. In some cases, the lower half of the top view can also be drawn entirely if necessary.
(3) Side view, elevation view and partial section view:
If necessary, a side view of the mold in its working position can be drawn. In some cases, the upper right corner of the drawing can also be used to show a top view of the pattern and a partial section.
(4) Part diagram:
The general artifact diagram is located in the upper right corner. For work performed by multiple sets of molds, it is necessary to draw a part diagram for the current process in addition to the part diagram for the previous process.
(5) Sample diagram:
For a progressive die, it is necessary to outline the layout, process sequence and stamping content for each stage. Step spacing, edge value and strip size must also be indicated. The matrix layout must be marked with the layout method, strip size and overlap value size.
(6) Parts list:
A parts list must be provided, indicating material and quantity. Standard parts must be specified in the specifications.
(7) Technical Requirements and Description:
Technical requirements include punch pressure, equipment type, general tolerance and mold assembly, installation and commissioning, mold closing height, mold clearance and other requirements.
Ⅷ . Draw non-standard parts
All dimensions, tolerances and adjustments, shape and position tolerances, surface roughness, materials used and their heat treatment requirements and other technical specifications must be indicated in the part drawings.
Ⅸ. Completion of tool registration cards and preparation of stamping process documentation
For small-scale production, a detailed table of process routes must be completed, while for large-scale production, a process sheet must be created for each part.
