In cold stamping processing, special process equipment for processing materials (metal or non-metal) into parts (or semi-finished products) is called cold stamping mold (commonly known as a cold punching mold).
Advantages of a stamping molds
As a very important processing method in modern industry, stamping molds are used to produce various sheet metal parts, which have the unique advantages of lightweight, high rigidity, high strength, good interchangeability, low cost, easy to achieve mechanical automation, and high production efficiency.
Principles for the selection of stamping molds materials
In stamping molds, various metal and non-metal materials are used, mainly carbon steel, alloy steel, cast iron, cast steel, hard alloy, low melting point alloy, zinc-based alloy, aluminum bronze, synthetic resin, polyurethane rubber, plastic, laminated birch board, etc. The materials used to make the molds require high hardness, high strength, high wear resistance, proper toughness, high hardenability, and heat treatment without deformation (or less deformation) and are not easy to crack during quenching.
Introduction of the structure of stamping molds
The structure of stamping mold, the structure of punching molds, mold structure is more or less the same, according to different product characteristics and demand design corresponding molds, different mold structure, its function is also different, the production out of the product is also different, in general, there are simple, there are complex. But no matter how complicated the structure is, its basic structure is the same, just several templates into the block and standard parts.
Generally speaking, a mold is assembled from several templates, parts (blocks or sub-blocks), and standard parts.
In the general structure of stamping molds, the specific templates from top to bottom (including code numbers) are
The templates for the upper mold are.
Upper pallet, upper cushion foot, upper mold holder (UPU), upper cushion plate (UBU), upper clamp plate (PHU), stop plate (PPS), and stripper plate (PSU).
The templates for the lower mold are.
Lower mold plate (mold), lower pad plate (LBD), lower mold holder (LPD), lower pad foot, and lower pallet.
Other less commonly used templates.
Upper cover plate (CVU), strike plate, upper template, lower striker plate, lower stop plate, lower clamping plate, male mold, female mold, etc…
Some of the mold parts are.
Entry subs, entry blocks for the upper mold: clamping plate entry block, stripper plate entry block, punch, etc.
The inlet of the lower mold, the inlet block: the inlet block of the lower mold, the cutter of the lower molds, etc.
Standard parts: spring, hexagonal screw, stop screw, wire spring, contour bushing, guide pillar, guide bushing, contour bushing spacer, dual-use pin, ejector pin, etc.
Non-standard parts: external positioning, internal positioning, pitch positioning, external limit post, internal limit post, etc.
Classification of stamping molds
Classification according to the nature of the process
The classification of process nature is divided into punching mold, bending mold, stretching mold, forming mold, and riveting mold.
1）、punching mold: along the closed or open contour line to make the material to produce the separation of the mold. Such as drop mold, punching mold, cutting mold, notching molds, cutting edge mold, cutting mold, etc.
2）、Bending mold: make the slab blank or other blanks along the straight line (bending line) to produce bending deformation to obtain a certain angle and shape of the workpiece of the mold.
3）、Drawing mold: It is the mold to make the sheet blank into open hollow parts or make the hollow parts change their shape and size.
4）、Forming mold: It is a mold that makes a direct copy of the blank or semi-finished workpiece according to the shape of the convex and concave mold, and the material itself only produces local plastic deformation. Such as expansion mold, indentation molds, flaring mold, undulation forming mold, flanging mold, shaping mold, etc.
5）、 riveting mold: is borrowed from external force to make the parts involved by a certain order and way to connect or lap together and then form a whole.
According to the processing method of the product classification
According to the different processing methods of products, mold can be divided into five categories: punching and shearing mold, bending mold, drawing mold, forming mold, and compression mold.
1）、 punching and shearing mold: is to shear role to complete the work, the common form of shear punching mold, under the material punching mold, punching mold, trimming mold, whole edge punching mold, pulling hole punching mold, and punching and cutting molds.
2）、 bending mold: is the flat embryo bent into an angle shape, depending on the shape of the parts, precision, and production volume; there are a variety of different forms of mold, such as ordinary bending mold, cam bending mold, rolled edge mold, arc bending mold, bending punching mold and twist punching mold.
3）、Drawing mold: Draw mold is to make the flat embryo into a seamless container with the bottom.
4）、Forming mold: It is used to change the embryo’s shape by various local deformation methods, such as convex forming mold, rolled edge forming mold, neck shrink forming mold, hole flange forming mold, and round edge forming mold.
5）、Compression mold: It uses strong pressure to make the metal embryo flow and deform into the desired shape, the types of which are extrusion mold, embossing mold, embossing mold, and end pressure mold.
Classification according to the degree of process combination
According to the classification of process combination degree, the mold can be divided into four categories: single process mold, compound mold, progressive mold, and transfer mold.
1）、Single process mold A mold that completes only one stamping process in one stroke of the press.
2）、Compound mold A with only one workstation and complete two or more stamping processes at the same workstation in one press stroke.
3）、Progressive mold (also called a continuous mold): A mold with two or more stations in the feeding direction of the blank, which completes two or more stamping processes at different stations one by one in one stroke of the press.
4）、Transfer mold: It combines the characteristics of a single process mold and progressive mold and uses a robotic transfer system to achieve rapid in-mold transfer of products, which can greatly improve the production efficiency of products, reduce the production cost of products, save material cost, and have stable and reliable quality.
The working process of stamping molds
The working principle of the drop punching mold is as follows: The upper mold, which is directly or indirectly fixed on the upper mold, is connected to the punching slider through the mold handle. The lower mold is fixed to the lower mold and the press table using a press plate. Guides guide the upper and lower molds. When the upper mold is lowered with the ram, the unloading material is first pressed against the plate material, and then the convex punch falls on the concave material to obtain the workpiece. The workpiece is stuck between the convex mold and the top block, and the scrap is tightly clamped to the convex mold. When the top mold is raised, the workpiece is ejected from the hole of the concave mold by the spring force of the top plate; at the same time, the scrap on the convex mold is removed by the spring force of the unloading plate, and the workpiece is taken away. The workpiece is removed by the spring force of the unloading plate and then taken away.
Problems and solutions that may occur during the production process of stamping molds
Scrap jumping hole
1) If The punch length is not enough, replace the punch according to the cutting edge of the punch into the concave mold plus 1mm of material thickness.
2） If the mold clearance is too large, cut into the sub to reduce the clearance or reduce the clearance with a phi machine
3）Punch or template is not demagnetized; demagnetize the punch or template with a demagnetizer.
Waste material blocking hole
1）Small drop hole or deviated drop hole, increase the drop hole, make the drop material smoothly
2）Chamfer in the drop hole; increase the drop hole to remove the chamfer
3) the knife mouth is not put taper, line cutting taper, or reverse the expansion of the hole to reduce the length of the straight wall position
4) If the straight wall of the cutter is too long, reverse drilling so that the straight wall of the cutter is shortened
5) The edge collapse, resulting in a large phi, blocking material from regrind the edge
Poor cutting edge
1）The edge collapses, causing the phi edge is too large to regrind the edge
2） If The gap between punch and concave mold is too large, line cutting into the block, re-match the gap
3) Poor finish of concave mold; polish the straight wall of the mold
4）The clearance between punch and concave mold is too small, save the mold again and match the clearance
5) If the top material force is too large, reverse pull out the phi front to change the spring, reduce the top material force
The cutting edge is not flush
1）Adjust the positioning of positioning offset
2) There is a single-sided molding; pull the material to increase the pressure force, adjust the positioning
3) design errors, resulting in uneven joint knife re-linear cutting edge knife edge inlay
4）Inaccurate feeding adjust the feeder
5）Mistake in the calculation of the feeding step, recalculate the step, and reposition the jointing knife
Punch easy to break
1）Closing height is too low, and the punch cut into the knife mouth is too long. Adjust the closing height
2）Improper positioning of the material, causing the punch to cut a single side, adjust the positioning or feeding device due to uneven force fracture
3) The lower mold waste blocks the cutter, causing the punch to break and re-drill the big drop hole to make the drop material smoothly.
4) The fixed part of the punch (clamping plate) and the guiding part is repaired or re-cut into the block to make the punch go up and down smoothly (playing board) offset
5) The punching plate is not well oriented, causing the punch to be re-matched to the gap of the punching plate due to unilateral force.
6) The punch cutter is too short, interfering with the beating board, change the punch and increase the length of the cutter part
7) The punch is not fixed well and moves up and down. Re-fix the punch so that it cannot move up and down.
8) The edge of the punch is not sharp, regrind the edge
9) The punch surface is strained, and the force is uneven when taking off the material.
10) The punch is too thin, too long, and not strong enough to change the punch type.
11) If The punch hardness is too high and the punch material is incorrect, change the punch material and adjust the heat treatment hardness.
1) misalignment of the pressure bar recalculate the position of the pressure bar or bending position
2) bending gap is too small, extrusion of iron chips to readjust the gap, or grinding forming block, or grinding forming punch
3) bending convex mold is too sharp to repair the R angle
4) too little material to connect the knife mouth to re-connect the knife mouth
5) pressure bar is a too narrow regrinding pressure ba
1) The center of the bottom hole of the sprouting and the center of the sprouting punch do not overlap to determine the correct center position, or move the position of the sprouting punch, or move into the sprouting – side high – side low or even rupture the position of the pre-punching hole, or adjust the positioning
2) Uneven gap of concave mold, resulting in budging – side high – side repair with a low budging gap or even rupture
3) The bottom hole of the pumping bud does not meet the requirements, resulting in the height of the pumping bud and recalculation of the bottom hole diameter, increasing or reducing the diameter deviation of the pre-punched hole, or even rupture
1) Forming mold convex mold is too sharp, resulting in material pulling and cracking forming convex mold repair R angle, appropriate repair R angle at the knife mouth
2) The forming punch length is not enough, failing to form the correct length of the calculated punch to adjust the actual length of the punch to achieve the requirements of the shape
3) The forming punch is too long, and the material at the forming area is deformed.
4) Insufficient material at the forming place causes pulling and cracking of the material, repairing the R angle, or reducing the forming height.
5) Poor positioning, resulting in poor forming, adjust the positioning or feeding device
6) forming gap is too small to cause pulling or deformation deployment gap
1) the mold is not adjusted in place to cause angular error resulting in size bias adjustment of the closing height is bad or poor angle difference
2) the elasticity is not enough to cause a bad angle resulting in size deviation for the spring
3) material does not meet the requirements of the angle caused by bad size for the material or readjust the gap deviation
4) material thickness deviation caused by bad angle leads to size deviation to determine the material thickness, change the material or readjust the gap difference
5）Improper positioning leads to size deviation. Adjust the positioning to make the size OK
6) design or processing errors caused by bending public block between the patch welding grinding, eliminating the gap between the block, resulting in small bending size
7) forming public without R angle, in the angle and other normal conditions forming public repair R angle under the bending height is small
8) both sides of the bending size are large, plus the pressure bar
9) single-sided bending pull material caused by the size of instability to increase the spring force, adjust the positioning
10) gap is not reasonable, causing bad angles and size deviation repair gap
11) the height of the folding knife is not enough; the bending punch into the folding knife is too short of increasing the height of the folding knife, so that the bending punch as far as possible into the folding knife force bit caused by bad angles more
12) bending speed is too fast, resulting in bending root deformation adjustment speed ratio control, choose a reasonable speed
13) unreasonable structure, the bending knife is not set into the fixed template, re-milling groove, the bending knife set into the template stamping, resulting in large gaps
14) molding male heat treatment hardness is not enough, resulting in pressure line collapse or reshaping the male pressure line flattening
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