The metal stamping process is a versatile manufacturing process used to produce high volumes of custom metal parts efficiently and cost-effectively. However, to reap the benefits of metal stamping services, the parts must be designed properly with stamping in mind. Here we will discuss the critical mechanical design principles and considerations for designing parts for metal stamping.
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The material used for metal stamping significantly impacts the part design. Ductile materials like low-carbon steel, stainless steel, aluminum, and brass are commonly stamped. Sheet thickness typically ranges from 0.5mm to 3mm for most stampings. Thicker materials up to 6mm can be stamped in some cases.
When selecting the material, consider factors like:
- Strength and hardness required
- Corrosion resistance needed
- Magnetic properties
- Weight and density
- Formability and ability to bend without fracturing
- Cost and availability
Understanding the formability, flexibility, and bending behavior of the material selected is crucial in the design stage. Consulting early with the Neway stamping engineer on material selection is recommended.
Uniform wall thickness, in part, produces the most consistent stampings. Thickness variations will increase scrap rates and make parts more prone to fracturing during stamping.
For most low-carbon steels, a wall thickness tolerance of ±0.1 mm is readily achievable for stampings. Tighter tolerances down to ±0.05mm are possible but may require additional process controls.
Springback is the elastic recovery of metal after forming and is influenced by material grade, hardness, part geometry, and grain orientation. The amount of spring back must be compensated for in die design by overbending the part.
The inside bend radius is the most critical factor for controlling spring back. Minimum bend radii ratios relative to material thickness are common:
- Aluminum alloys - 1:1
- Low carbon steel - 0.5:1
- Stainless steel - 1:1
Sufficient draft angles must be designed into the part geometry for proper die clearance and part release. Standard draft angle requirements are:
- Low carbon steel - 2-3° draft per side
- Stainless steel - 4-6° per side
- Aluminum alloys - 3-5° per side
Deeper draws need higher draft angles. A sufficient draft can lead to parts jamming in the die. Allowances should also be made for any coatings or plating that will increase part thickness.
Controlling the inside bend radius is critical for achieving quality parts. Tighter radii increase strain hardening and the risk of cracking. Standard minimum inside bend radius guidance for metal stampings is:
- Low carbon steel - Thickness x 0.5
- Stainless steel - Thickness x 1
- Aluminum alloys - Thickness x 1
Deeper drawn parts require more generous radii at the maximum depth point. Using standard die radii will simplify the die design and construction. Radii are typically specified starting from the smallest standard size above the minimum and increasing in increments of 0.5mm or 1mm.
The placement and design of any holes and slots in part must consider stamping process limitations.
For hole location accuracy, expected tolerances are:
- ±0.5mm when the hole is up to 150mm from the datum
- ±0.8mm for holes 150mm to 300mm from datum
Wide slot widths are preferred over long slot lengths to control positioning accuracy. Slot length should not exceed 3x width.
Hole and slot placement should avoid highly deformed stamping areas whenever possible. It helps maintain dimensional accuracy and reduces stress cracking around the holes. Generous fillet radii where holes meet internal angles further reduce stress.
Narrow strips of material between holes or wide spaces are prone to tearing or fracturing during stamping. Minimum web widths relative to material thickness should be:
- Low carbon steel - 8x material thickness
- Stainless steel - 10-12x thickness
- Aluminum - 14x thickness
Wider bridging should connect closed, isolated material islands to the surrounding main body areas. Using notched tabs instead of solid bridging is another strategy to improve material flow.
Protruding flanges, bosses, attachment points, and louvers must be generously rounded and smoothly blended into the base geometry. Otherwise, these areas will be prone to cracking or splitting during forming.
Minimum bend radius guidelines should be followed for small protrusions. More prominent protrusions may require heavier gusseting at the base and gradual transitions into the surrounding walls.
Stamping dies are designed to separate along parting lines to eject completed parts. Parts must be oriented to enable a single straight-line parting direction without any undercuts.
Constant and smooth surfaces should be maintained along the parting lines. Steps, gaps, and uneven surfaces will prevent proper die function. Any text or graphics on the part surface should also avoid the parting line area.
Attachments like threaded inserts, fasteners, and hinges may be added to stampings in secondary operations. Allowance should be made for hardware clearance, insertion points, and assembly access features.
Areas that will receive inserts should have sufficient local wall thickness. Holes for self-tapping screws require extra clearance diameter over thread size to account for material displacement.
Stamping requires an initial tooling investment for die manufacture. Impact on tooling cost and lead time should be considered early when designing parts.
Designs that minimize required die operations, specialized machining, and extensive polishing or texturing will simplify tooling. Standard-size radii and minimal variation across bend geometries also keep tooling costs down.
Many stampings undergo additional processing like welding, PVD, powder coating, heat treatment, or assembly. Designs should accommodate the space needed for jigs and fixtures used in subsequent operations.
Plating or coating thickness can increase part dimensions. Tight tolerances may be difficult to maintain on coated parts, so tolerance should be allocated accordingly. DRAINAGE and access points are needed for liquids applied during plating or coating.
Validation with your stamping partner should occur early in the design process to avoid extensive redesigns. Companies experienced in stamping can assess formability, analyze critical transitions, and recommend modifications before tooling starts. This collaboration is vital for designing optimized, cost-effective parts that leverage the full capabilities of metal stamping.
Well-designed stampings take full advantage of the process while minimizing manufacturing issues like cracking, spring back, and dimensional errors. Major considerations include:
- Material selection and properties
- Wall thickness uniformity
- Inside bend radii and draft angles
- Draw depths and clearances
- Hole and slot placement
- Bridging, webbing, and hardware allowances
- Parting line and surface quality
- Tooling complexity impact
- Secondary processing requirements
Incorporating these best practices and others will result in stamping designs with reduced lead times, improved quality, and lower overall costs. Effective early collaboration between designers and experienced stamping partners makes designing for stamping more straightforward. With the right design approach, metal stamping provides a fast, reliable way to produce complex and durable custom metal parts at scale.
Get It Done Right with Neway Metal Fabrication
For over 30 years, Neway has offered a full range of precision sheet metal fabrication services. Their capabilities include laser cutting, plasma cutting, stamping, bending, welding, and assembly. Neway's decades of experience and end-to-end services ensure you get high-quality custom metal parts. An added benefit is their free sample parts for design validation before your entire production run. For expert metal fabrication, you can trust, choose Neway.
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:
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.
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.
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.
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).
Flanging
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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.
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 Design Considerations
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.
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.
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.
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.
Tolerances: Determine your project's acceptable tolerance levels. Tolerances achievable will vary depending on the metal type, design requirements, and machining tools employed.
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.
Common Defects in Metal Stamping
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.
Insufficient hole spacing: If the hole is not the correct distance from the edge of the workpiece, at least twice the thickness of the part, 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 many components, from micro-miniature parts to massive, complicated pieces. Don't hesitate to contact us to learn more about LEADRP's bespoke metal stamping capabilities or if you have any queries about your upcoming related projects.
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
Q: What is the best raw material for metal stamping?
A: 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.
Q: What is the first step in the metal stamping method?
A: 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.
Q: How do you make a metal stamping process?
A: 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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