Nine Steps to A Good Metal Stamping Die

Analyze the stamping processability of the co - manufactured parts based on relevant information, and conduct process audits and standardization audits on the workpieces.

1. Obtain the product part drawing with specific technical requirements marked. Understand the shape, size, and precision requirements of the workpiece. Analyze the dimensions (size and position) of key holes, key surfaces, and determine the datum plane of the workpiece.
   In fact, the various processability requirements of stamping parts are not absolute. Especially in the current situation where stamping technology is developing rapidly, according to the needs and possibilities of actual production, comprehensively apply various stamping technologies, reasonably select stamping methods, and correctly formulate stamping processes and select mold structures to meet both the technical requirements of the product and the conditions of the stamping process.
2. Collect the process route cards for the machining of the workpiece. From this, the interrelationships between the preceding and following processes and the machining process requirements and assembly relationships that must be mutually guaranteed among each process can be studied.
3. Understand the production batch of the workpiece. The production of parts plays a decisive role in the economy of stamping processing. For this reason, based on the production batch and quality requirements of the parts, matters such as the type, structure, and material of the mold must be determined. From this, analyze the economy of the mold machining process and the rationality of the production of the proposed project, and outline the stamping steps.
4. Determine the specifications of the raw materials of the workpiece and the situation of the blank (such as sheet metal, strip material, coil material, scrap, etc.), understand the properties and thickness of the material, and determine whether to adopt the less - or no - scrap blanking method according to the processability of the part, and initially determine the specifications and precision grades of the material.
   Under the premise of meeting the requirements of service performance and stamping performance, inexpensive materials should be used as much as possible.
5. Analyze the requirements for the fiber direction of the material and the direction of burrs in design and process.
6. Analyze the technical capabilities and equipment conditions of the die (mold) workshop for manufacturing molds and the situation of available standard mold parts.
7. Familiarize yourself with the equipment information or situation of the stamping workshop.
8. Study and digest the above information, and initially conceive the structural scheme of the mold. If necessary, put forward modification opinions on the established product design and process process, so that the product design, process process, and mold design and manufacturing can be better integrated to achieve a more perfect effect.

II. Determine the Process Plan and Mold Structure Type
The determination of the process plan is the most important link after the processability analysis of the stamping part. It includes:

1. According to the shape characteristics, size precision, and surface quality requirements of the workpiece, conduct a process analysis, determine its main attributes, and determine the nature of the basic processes. That is, the basic processes such as blanking, punching, bending, deep drawing, flanging, and bulging. List all the single processes required for stamping. Generally, they can be directly determined from the requirements of the product part drawing.
2. According to the process calculation, determine the number of processes. For deep - drawn parts, the number of deep - drawing operations should also be calculated. For bending parts and blanking parts, the number of processing operations (one time or several times) should also be determined according to their shape, size, and precision requirements.
3. According to the deformation characteristics, size precision requirements, and convenience of operation of each processing step, determine the sequence of process arrangement. For example, whether to punch first and then bend or bend first and then punch.
4. According to factors such as production batch, size, precision requirements, mold manufacturing level, and equipment capacity, combine the initially arranged single processes as much as possible. For example, combined stamping processes and continuous stamping processes. Usually, thick - material, low - precision, small - batch, and large - size stampings are suitable for single - process production and simple dies; thin - material, small - size, and large - batch stampings are suitable for continuous production with progressive dies; and stampings with high positional precision are suitable for stamping with compound dies.
   After determining the nature, sequence, and combination of processes, the stamping process plan is determined. That is, the structural types of molds for each process are also determined.

III. Conduct Necessary Process Calculations

1. Design the layout of materials and calculate the blank size.
2. Calculate the stamping force (including blanking force, bending force, deep - drawing force, flanging force, bulging force, as well as unloading force, ejecting force, blank - holding force, etc.). If necessary, also calculate the stamping work and power.
3. Calculate the pressure center of the mold.
4. Calculate or estimate the thickness of the main parts of the mold, such as the thickness of the die, punch holder, backing plate, and the free height of the unloading rubber or spring.
5. Determine the clearance between the punch and die, and calculate the dimensions of the working parts of the punch and die.
6. For deep - drawing processes, it is necessary to determine the deep - drawing method (with or without blank - holding), calculate the number of deep - drawing operations and the semi - finished product sizes of intermediate processes. For some processes, such as continuous deep - drawing of strip materials, special process calculations are required.

IV. Overall Design of the Mold
On the basis of the above analysis and calculation, conduct the overall design of the mold structure (at this time, a sketch is generally sufficient), and initially calculate the closed height of the mold and roughly determine the external dimensions of the mold.

V. Structural Design of Main Mold Components

1. Workpiece - related parts. Design the structural types of parts such as punches, dies, and punch - dies, and select their fixing forms.
2. Locating parts. There are many types of commonly used locating devices in molds, such as adjustable locating plates, fixed stop pins, movable stop pins, and distance - controlling side blades. They need to be selected and designed according to the specific situation.
   In continuous dies, it is also necessary to consider whether to use initial stop pins.
3. Unloading and ejecting devices. Select whether to use rigid or elastic ones, and select and calculate springs and rubbers.
4. Guiding parts. Select whether to use guide posts and guide bushes for guidance, guide plates for guidance, central guide posts, side - rear guide posts, or diagonal guide posts, and select sliding guide bushes or ball - bearing guide bushes.
5. Supporting and clamping parts, fastening parts. Select the structural types of mold handles, upper and lower mold bases, etc.

VI. Select Stamping Equipment
The selection of stamping equipment is an important part of process design and mold design. Reasonably selecting equipment has a significant impact on ensuring the quality of workpieces, improving productivity, and ensuring operational safety, and also brings convenience to mold design.
The selection of the stamping type mainly depends on the process requirements and production batch.
The determination of the specifications of stamping equipment mainly depends on the process parameters and mold structure dimensions. For crank presses, the following requirements must be met:

1. The nominal pressure of the press must be greater than the stamping process force. More precisely, the load curve of the stamping process must be below the allowable load curve of the press.
   For deep - drawn parts, the deep - drawing work must also be calculated.
2. The die - setting height of the press must meet the requirements of the mold closed height.
3. The stroke of the press must meet the requirements of workpiece forming. For the press used in the deep - drawing process, its stroke must be 2 - 2.5 times greater than the height of the workpiece in this process so as to facilitate the placement of the blank and the removal of the workpiece.
4. The table size of the press must be larger than the external dimensions of the lower mold base of the mold, and there must be a space for fixing the mold. Generally, it is more than 50 - 70 mm larger on each side. The size of the leak hole on the table of the press must be larger than the size of the workpiece (or scrap).

VII. Draw the General Assembly Drawing of the Mold
The general assembly drawing of the mold (including part - working drawings) shall be drawn in strict accordance with the drawing standards (GB/T4457 - GB/T4460 and GB/T131 - 1993). At the same time, in actual production, combined with the working characteristics of the mold and the needs of installation and adjustment, the layout of its drawing surface has formed certain habits.
The general assembly drawing of the mold includes:

1. Front view. Draw a sectional view of the mold in the working position. Generally, one half shows the situation when the blank is placed in before stamping starts (when the slider of the punching machine is at the upper dead center); the other half shows the state after stamping is completed, the workpiece has been formed (or separated), and the slider of the punching machine is at the lower dead center.
2. Top view. Usually, draw the lower - half top view, and sometimes draw the upper - half top view as well. According to needs, sometimes only the lower - half top view is drawn.
3. Side view, bottom view, and local sectional view, etc. If necessary, draw a side view of the mold in the working position. Sometimes, the top view of the upper half of the mold and local sectional views are drawn in the upper right corner of the drawing.
4. Workpiece drawing. Generally, the workpiece drawing is drawn in the upper right corner. For work completed by several sets of molds, in addition to drawing the workpiece drawing of this process, the workpiece drawing of the previous process also needs to be drawn.
5. Layout diagram. For progressive dies, it is necessary to draw the layout method, the sequence of process arrangements, and the stamping contents completed by each step; mark the step pitch, trim allowance, and strip material size. The layout diagram of blanking dies needs to mark the layout method, strip material size, and trim allowance.
6. List the part detail list, indicating the material and quantity. For standard parts, the specifications must be selected.
7. Technical requirements and instructions. Technical requirements include stamping force, the model of the selected equipment, the overall positional tolerance of the mold and assembly, installation and debugging, mold closed height, mold clearance, and other requirements.

VIII. Draw Part Drawings of Non - Standard Parts
All dimensions, tolerances and fits, geometric tolerances, surface roughness, materials used, and their heat treatment requirements, as well as other technical requirements should be marked on the part drawings.

IX. Fill in the Mold Record Card and Write Stamping Process Documents
For small - batch production, a process route detail sheet should be filled out; while for large - batch production, a process card and an operation card need to be formulated for each part.