Bending parts, punching parts, drawing parts stamping process introduction
Forming principle of stamping parts: Stamping is the forming process of workpieces (stamping parts) of the required shape and size by applying external force to sheets, strips, pipes and profiles, etc. by means of presses and dies to cause them to plastically deform or separate. method.
Process classification: Stamping is mainly classified by process, which can be divided into two categories: separation process and forming process.
Separation process (blanking process): The purpose is to separate the stamping parts from the sheet along a certain contour line, while ensuring the quality requirements of the separated section. Separation process: blanking (blanking, punching), shearing, notching, trimming, sectioning.
The deformation process of the sheet during blanking
When the die gap is normal, the blanking process of metal materials can be divided into three stages:
1) Elastic deformation stage
The sheet is deformed by elastic compression, bending and stretching. When the material is subjected to external force, it deforms or changes in size, and the deformation that can be recovered is called elastic deformation.
2) Plastic deformation stage
The stress of the sheet reaches the yield limit, and the sheet begins to undergo plastic shear deformation. It refers to the part of the deformation of the material that is produced under the action of external force and cannot be recovered after the external force is removed.
3) Fracture separation stage
The formed crack extends into the material in the direction of the maximum strain rate and develops in a wedge shape
After punching, the section of the sheet is divided into four parts
Forming process: It is to plastically deform the sheet without damage to make a workpiece of the required shape and size.
Forming process: bending, rolling, twisting, deep drawing, thinning and deep drawing, flanging (hole flanging, outer edge flanging), shrinking, flaring, undulating, crimping, expanding, spinning, shaping , leveling, embossing, extrusion (forward extrusion, reverse extrusion, compound extrusion).
Stamping Design Considerations
Stamping manufacturability of blanking stamping parts
1). Shape and angle of blanking parts: The shape design of blanking parts should be as simple and symmetrical as possible, so as to minimize waste during layout. The corners of the blanking parts should avoid sharp corners, and should have appropriate rounded corners
2). The minimum hole diameter of the punching hole (the hole diameter should not be too small when punching) The minimum size is as shown in the table below
The structural dimensions of the blanking parts (such as hole diameter, hole spacing, etc.) must consider the thickness of the material.
3). Minimum hole spacing and hole margin
The distance between the holes and the edges of the blanking parts should not be too small.
4). Minimum width of protruding cantilever and groove
Stamping manufacturability of bent parts
Bending is a stamping process that uses a material to produce plastic deformation to form an angular shape. Bending can be done on Outon presses with dies, or it can be done on dedicated bending machines or bending equipment.
According to the different processing materials, bending can be divided into sheet bending, tube bending, profile bending, bar bending, etc.; according to the different equipment used for bending, it can be divided into bending, roll bending, stretch bending, roll bending, etc. .
The accuracy of the bending part processing is related to many factors, such as the mechanical properties and material thickness of the bending part material, the mold structure and mold accuracy, the number of processes and the sequence of the processes, and the shape and size of the bending part itself. Bending parts with high precision requirements must strictly control the material thickness tolerance. Generally, the dimensional economic tolerance level of bending parts is preferably below IT13 level, and adding shaping and other processes can reach IT11 level.
The bending process is to use the V-shaped bending die to press the mold structure diagram of the V-shaped part. The punch 1 and the punch 2 are basically the same as the inner and outer contours of the curved workpiece. When the punch is pushed down by an external force (if the force machine slider moves), the sheet placed between the punch and the punch is bent into a shape. required artifact.
Bending can be divided into free bending and correction bending. The difference is that free bending means that when the punch, sheet and die are completely fitted, they will no longer be pressed down; while correction bending is smearing on the basis of free bending. Press down to make the workpiece undergo a one-step plastic deformation to reduce the springback of the bending part.
- When the material is bent, when the bending fillet exceeds the ultimate strength of the material, cracks and breaks will occur, and too small bending fillet radius should be avoided
- The setting of the R angle should preferably not be greater than 1.5 times the thickness of the material itself. Because the R angle is too large, the rebound is also very large after bending.
- The bending height of the bending part should not be too long, and H should not be too small, especially when the material t>2mm is too small (remember), it will make it difficult to bend, and it is difficult to obtain parts with accurate shapes.When the bending angle of the bending part is 90°, in order to facilitate the forming, the height of the straight side of the bending part should be h>2t. When h=1.3t-2t, R≈0 or a bending method such as pressing groove should be used, as shown in the figure below.
- Try not to design the bending line of the bending part in the place where the width suddenly changes (as shown in the figure below) to avoid tearing.If it has to be designed at the sudden change of width, the process hole or process slot can be pre-punched at the sudden change of width.
- For bending parts with holes, if the hole is located near the bend, it will deform the hole when it is bent.Solution: Distribute the holes outside the deformed area.As shown in the figure below, for the bending part, the distance from the hole edge to the center of the bending radius R is taken as: when t<2mm, l≥t; when t≥2mm, l≥2t.
- When the bending part is composed of wide and narrow parts, the transition distance L≥R, see the figure below.
- For the bending of symmetrical parts, the left and right bending radii should be the same, so as to ensure the force balance during the bending process and prevent slippage during the bending process, see the figure below.
- When designing the bending parts, due to the irregular shape of the bending and the shape of the overall stamping parts, it is necessary to design the datum holes or datum edges and some benchmarks for marking the tolerances on the stamping parts.Such as: faces, edges, holes, etc., but try not to set the benchmark in places that are difficult to measure, such as: the center of the space, elements that are difficult to determine, etc., see the figure below.
- When designing bending parts, it is necessary to consider whether there is enough space for the unfolding length (direction) of the material before bending (distance between two pieces> t)
Stamping manufacturability of drawing parts
1) Deep drawing concept
A stamping method for stamping flat blanks into hollow parts with various openings by using a die, or pressing the open hollow parts that have been made into hollow parts of other shapes and sizes.
Deep drawing process classification
1) According to the change of wall thickness:
- ① General deep drawing (the wall thickness of the workpiece remains unchanged)
- ② Thinning and deep drawing (thinning of the wall thickness of the workpiece)
2) According to the shape of the blank used:
- ① The first deep drawing (using a flat blank)
- ② Each subsequent deep drawing (taking the open hollow part as the blank)
3) Deep drawing deformation process:
4) Changes in each part of the blank during the drawing process:
- ① Plane flange part (main deformation area)
- ② Die fillet (transition area)
- ③Cylinder wall part (deformation area)
- ④ Punch fillet (transition area)
- ⑤ Bottom part of the cylinder (small deformation area)
Forming introduction of shrinkage, flanging and expansion
Stamping parts structure design points
- Avoid right angles and arc transitions
- There is sufficient distance between holes and holes, holes and edges, and holes and bends
- The bending radius cannot be too small, and the bending height is suitable
- The stiffness and strength of the thin plate can be improved by reinforcing ribs
- Pay attention to the fiber direction of the sheet
Balford has passed ISO9001 in 2017. We has over ten years experience on manufacturing motor housing, solenoid valve housing and sensor housing, focused on auto parts.Now Balford enter into solenoid valve housings and sensor housings industry that are mainly based on difficult deep drawing process.
We employ documented procedures for every step in the manufacturing process from initial program launch through steady-state production in order to ensure consistent performance. We engineer our processes to produce the desired results, monitor those results, and use what we learn to regularly refine our processes as part of our commitment to continuous process and efficiency improvement.
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