Sheet metal stamping parts

Overview of Sheet Metal Stamping

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Metal stamping is one of the world’s most cost-effective, highly efficient, precisely repeatable, and widely utilized production processes. It guarantees optimized part performance, rapid turnaround, high quality, and minimal costs in product design.

Metal stamping creates many metal components, which have contributed significantly to various industrial applications, including automobiles, machinery, electronics, home appliances, tools, etc. This article will explain this manufacturing process and how to implement it in your industry successfully.

What is Metal Stamping?

Metal stamping is the process of placing flat sheet metal in blank or coil form into a stamping press, where a tool and die surface shapes the metal into a net shape. Metal stamping includes numerous sheet-metal forming processes, such as punching with a machine or stamping press, blanking, embossing, bending, flanging, coining, and more.

Metal stamping is a cost-effective method for forming metal components with various properties, including strength, durability, wear resistance, superior conductivity, and stability. Learning metal stamping can help you acquire the highest quality components so your project operates optimally.

Manufacturing Process of Metal Stamping

Metal stamping is a cold-forming manufacturing process that includes extensive operations for changing flat metal sheets into distinctive shapes with features such as bends, holes, grooves, and slots. Determining which process is appropriate for a particular part is an essential step in the design process. Below are the most widespread metal stamping manufacturing processes.

Blanking 

Blanking is a steel manufacturing process that involves putting a coil of sheet metal into a press and die to form a flat, geometric shape (or “blank”). The blank is punched out of a metal sheet during this process. The procedure and tools used in blanking are similar to those used in piercing, except that the removed part is used as a fresh metal piece. Here is a graphic representation of the blanking process:

Blanking

Piercing 

Piercing can be used to create slots, holes, or other cutouts in part. Piercing is a shearing process that involves using a punch and die to make a hole in sheet metal or a plate. Piercing punches the required shapes out of the metal sheet, which can be performed simultaneously with blanking. In the piercing process, the unusable piece is removed from the metal and becomes scrap.

Piercing

Punching 

The punching process uses a press pushing a punch through a metal form to create a hole with a precise shape and placement. The punching tool frequently separates the extra material from the newly created form. Punching may or may not involve shear.

CNC punching is essential for producing sheet metal blanks. Punching is a speedier operation that lends itself to metal fabrications with numerous comparable features or a higher volume of parts per run.

Embossing 

Metal embossing is a process for imparting a design on metal sheets. The opposing side can produce a raised effect by pushing the metal with an embossing tool or stylus. The positive impression has a smooth surface that can shine or take pigment by laying the metal sheet on a rubber or foam pad.

Embossing is highly similar to engraving. However, engraving cuts a small portion of the metal to create a logo or a sign on a metal part. Embossing utilizes a preconfigured punch to make an indentation in the form of the desired message or image.

Embossing

Bending 

Bending is a fundamental process of shaping metal into desired shapes such as L, U, or V-shaped profiles. Metal bending produces a plastic deformation with stresses beyond the yield point but below the tensile strength. Bending often happens around a single axis.

When designing bends for stamped metal parts, it’s critical to consider enough material – make sure your part and its stock have enough material to complete the bend. Remember the following points:

  • It can get deformed if a bend is too close to the hole.
  • Every corner in your blank design should have a radius of at least half the thickness of the material. 
  • Notches, tabs, and slots should have widths at least 1.5 times the thickness of the material.
  • Avoid sharp corners and intricate cutouts whenever possible to minimize the instances and severity of burrs.

Bending

Coining

The workpiece is stamped while placed between a die and a punch or press during the coining process. This action forces the punch tip to penetrate the metal, resulting in precise and repeatable bends. The deep penetration also has no spring-back effects by relieving internal stresses in the metal workpiece.

Coining can subject a component to extreme stress and strain. This causes a plasticized material flow so that the workpiece has smoother surfaces and edges and is more closely matched to the design tolerances. Coining is frequently used to reduce metal thickness and shape the part. Using the coining process can produce coins (metal currency).

Coining

Flanging 

Flanging is the process of introducing a flare or flange onto a metal workpiece using dies, presses, or specialist flanging machinery. Tension (stretch) flanges and compression (shrink) flanges are the two fundamental types of flanges. Tension flanges are prone to splitting. Compression flanges are prone to wrinkle.

Flanging is similar to bending in that it is done along a curved line. This complicates the job slightly, necessitating the procurement of specialized flanging equipment.

Flanging

Types of Metal Stamping

There are four major types of metal stamping – progressive die stamping, four-slide stamping, deep draw stamping, and short run stamping. 

Progressive Die Stamping

Progressive die stamping consists of many stations, each with its function. The metal strip first feds through a progressive stamping press and then unrolls steadily into a die press. This is the stage at which each station performs a distinct cutting, punching, or bending function. Each subsequent station’s actions add to the work of the previous stations, resulting in a completed part.

This stamping type is perfect for producing metal components with complex geometrical specifications. Progressive die stamping can assist producers with lowering labor costs, accelerating turnaround time, increasing repeatability, and shorting run length.

Fourslide Stamping

As its name suggests, a fourslide contains four slides. Fourslide stamping allows up to four tools, one per slide, to be used simultaneously to accomplish numerous bends. As material enters a fourslide, each shaft equipped with a tool bends it in rapid succession.

Fourslide metal stamping has significant advantages over traditional press stamping, making it an excellent choice for many applications. For example, this stamping type has more flexibility for design changes and versatility for more complex parts.

Deep Draw Stamping

Deep drawing entails pulling a sheet metal blank into a die and forming it into a shape. When the depth of the drawn part exceeds its diameter, the process is referred to as “deep drawing.” This type of forming is appropriate for producing components that require a series of diameters. Deep draw stamping is a more cost-effective alternative to turning processes, which often consume more raw materials. Deep drawing stamping is commonly used for cookware and utensils, electronic relays, automotive components, and aircraft parts.

Short Run Stamping

Short run stamping has low upfront tooling costs and is an excellent option for prototypes or small projects. Following the creation of the blank, manufacturers bend, punch, or drill the part using a combination of bespoke tooling components and die inserts. The smaller run sizes and customizable forming operations may lead to a higher per-piece charge. However, the absence of tooling costs may make the process relatively cost-efficient for projects that require a fast turnaround.

Manufacturing Tools for Metal Stamping

The metal stamping may appear complicated, but a suitable toolset can ensure great results. Let us learn more about manufacturing tools for metal stamping.

Stock Strip Layout and Design

The initial tool is made according to the stock strip layout and design, where the designer design the strip and sets tolerances, dimensions, scrap minimization, feed orientation, etc.

Tool Steel and Die Set Machining

CNC enables greater precision and repeatability for even the most intricate dies. Wire EDM machines and 5-axis CNC mills can cut through hardened tool steels with tight tolerances.

Secondary Processing

Heat treatment is given to metal parts to increase their strength and application-specific durability. Grinding is utilized to finish parts requiring high surface quality and precise dimensions.

Wire EDM

Wire electrical discharge machining uses an electrically charged strand of brass wire to form metal materials. Wire EDM can cut the most complex shapes, including contours and small angles.

Types of Metal Stamping Die

A stamping die is a precise tool that can cut and form metal sheets into the desired profiles and shapes by pressing them between components. Metal stamping die can be categorized as either single-station or multi-station dies.

Single-station Dies

Compound and combination dies are examples of single-station dies. Compound dies conduct many cutting operations in a single press, such as the multiple cuts required to make a simple washer from steel. Combination dies integrate both cutting and non-cutting processes in a single press stroke. One example is a die that creates both a cut and a flange for a given metal blank.

Multi-station Dies

Multi-station dies include progressive dies and transfer dies in which notching, punching, and cutting operations are performed sequentially from the same die-set. In contrast to single-station dies, multi-station dies transfer through mounted traveling tracks within the press.

There is another type of multi-station die called steel rule or knife dies. These dies were used to make parts out of softer materials like paper, leather, or cardboard. However, they are utilized in shaping metals, including copper, brass, and aluminum.

Metal Stamping Parts Design Tips

Sheet metal and coiled metal wire are the most typical materials used in metal stamping. To create well-formed and accurate products in metal stamping designs, you must refer to the following considerations.

#1 Bend radius: The material should normally bend in a single orientation, and the inside bend radius should be at least equal to the sheet thickness.

#2 Grooves, holes, and slots: Maintaining groove, hole, and slot diameters equal to or larger than sheet thickness results in superior form with fewer burrs and bulges. Keeping the holes at least twice as far apart as the material’s thickness can also reduce bulging and deformation.

#3 Material needs and characteristics: Different metals and alloys have distinct properties, such as varying degrees of bending resistance, strength, formability, and weight. Designers must consider both the advantages and limits of their chosen metal.

#4 Tolerances: Determine your project’s acceptable tolerance levels. Tolerances achievable will vary depending on the metal type, design requirements, and machining tools employed.

#5 Wall thickness: Typically, uniform wall thickness throughout a product is optimal. Suppose a part has walls of varying thicknesses. In that case, it will be exposed to variable bending effects, resulting in deformation or falling beyond the tolerances of your project.

Typical Metal Stamping Defects

Some common defects in metal stamping include hole deformation, insufficient hole spacing, bending damage, and stamped edge burrs.

Hole deformation: Typically, three-dimensional metal parts with holes undergo hole punching first and subsequent bending into shape. The holes can stretch or deform if they are too close to the bent edge. Hole deformation can be resolved by raising the pressure of the ejector plate or by adding a hard spot on this plate to increase the friction between the aforementioned surfaces so that they do not slide.

Insufficient hole spacing: If the hole is not the correct distance (at least twice the thickness of the part) from the edge of the workpiece, the strip of material between the hole and the edge will bulge outward.

Bending damage: Parts with extreme bends are more prone to cracking, especially if manufactured from stiff metals with little plasticity. Long cracks may develop along the bend if the bend is parallel to the metal’s grain direction.

Stamped edge burrs: Cutting and stamping tools can shear metal edges, forming sharp burrs along the edge’s base. This might cause the piece to be abrasive to the touch, resulting in an imperfect finish or even detrimental to the end product’s dimensionality.

Metal Stamping Advantages and Disadvantages

Sheet metal stamping provides various advantages over other processes, including lower die costs, lower secondary costs, and a high level of automation. Metal stamping dies are less expensive to manufacture and maintain than dies used in other common operations. Stamping machines are typically easy to automate and may use complex computer-control systems to provide faster output,  more precision, and shorter turnaround times.

The higher cost of presses is one of the disadvantages of stamping. Producing custom metal stamping dies requires a longer pre-production process because dies must also be purchased or manufactured. Changing the dies might also be challenging if you want to modify the design during manufacturing.

Sheet Metal Stamping Applications

Stamping parts are utilized in many applications, particularly those that involve three-dimensional designs, lettering, or other surface engraving characteristics. These stamping goods are typically manufactured for home appliances, telecommunications services, automobile firms, the lighting industry, military and defense, medical equipment, aerospace industries, and electronics.

Electronic stampings are electronic components created by the metal stamping process. They can be used in numerous industries, from consumer electronics and home appliances to telecommunications and aerospace. Electronic stampings have various metals, including copper, copper alloys, aluminum, steel, platinum, and gold.

Electronic components manufactured using metal stamping include terminals, contacts, lead frames, springs, and pins. They can be made from either ferrous or nonferrous materials. Metal stampings are widely used in computers, electronic equipment, and medical systems. Because stamping may create unique shapes, this cold forming process finds wide use in many electronics.

How to Save the Cost of Metal Stamping?

To save cost on the stamping process, you must pay close attention to three primary factors:

  • When selecting the material for your application, you can consider an alternative metal with similar properties. 
  • The more parts you can manufacture at once, the less it will cost you overall.
  • Secondary processes are accomplished by partnering with a manufacturer providing transportation, extra fabrication, coating, finishing, treatment, and packaging.

How to Assemble Metal Stamping Parts?

After fabricating the necessary sheet metal parts, you can efficiently complete the product using various assembling techniques. There are two ways to help assemble metal stamping parts: riveting and welding.

Riveting 

Sheet metal riveting can create complicated stamped metal assemblies without additional heat distortion in the aerospace industry. Before assembly, it is necessary to drill holes for the rivets. The rivet is a bolt pressed into the hole and then distorted to secure the pieces.

Welding 

Another way is to use metal welding parts. Two welding options will be pretty handy if you choose this process for joining.

Pinpoint welding is a rapid, simple, and high-quality welding procedure. The two sheets are positioned between two cylinder-shaped electrodes. The electrodes grip the sheets and heat the area where the parts come into contact until they melt and fuse.

Arc welding is the most frequent welding procedure, and its main advantage is the ability to create watertight joints readily. Therefore, arc welding will come in handy for making a tank.

Conclusions

Sheet metal stamping is a manufacturing process that neither subtracts nor adds material to the final parts. This process involves forming to create the desired shape from straight metal sheets. Metal sheets are bent on specialized equipment utilizing specific dies and punches. In most cases, sheet metal stamping does not require heating the sheet. Hence there is no heat distortion in the die surface. Metal stamping is both a cost-effective and environmentally benign process.

LEADRP can provide a quick and cost-effective precision stamping solution for sheet metal parts, from small, easy-to-working pieces to large, complicated parts. Don’t hesitate to contact us to learn more about LEADRP’s metal stamping services, you design it, we make it.

Reference

Stamping (metalworking) – From Wikipedia

Metal Stamping – The Complete Guide – From Sourcing Allies

The complete guide of perfect metal stamping design – From Fortuna

Metal Stamping Design Guidelines – From Keats Manufacturing Company

FAQ

Steel and steel alloys are some of the most cost-effective material options for stamped parts because they are accessible to source and highly compatible with most metal forming processes.

Blanking. When required, blanking is the first step of the stamping process. Blanking is the process of cutting larger sheets or coils of metal into smaller, more manageable pieces. Blanking is usually performed when a stamped metal piece is drawn or formed.

The process of turning metal sheets into a useful part or component is called sheet metal stamping. The metal is fed into a press, where the stamping tool, or a die, creates the desired shape. The die is pressed into or through the metal with tremendous force.

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