Custom metal stamping is, by definition, designed exclusively for a specific part and its functions. Unlike mass-produced stampings, custom metal stamping is chosen when precision and complex dimensions are required to produce a unique part. This process requires the upfront development of a custom metal stamping tool that cuts and forms the part as the metal goes through the stamping press. Custom metal stampings can range from large components for automobiles and custom assemblies to micro-miniature parts for medical devices or electronics.
Stamping includes a variety of sheet metal forming processes consisting of either a single station operation where every stroke of the press produces the desired form of the metal part or could occur through a series of stages. The following techniques are used to achieve the desired shape in the press.
Bending creates a formed feature by angular displacement of a sheet metal workpiece. In some processes, one edge of the workpiece is clamped in a stationary position while the other edge is clamped by a metal tool and bent over a form to create a precise bend or shape. Alternatively, the metal piece may be pushed into or against a form.
The blanking process removes a metal piece from the primary metal strip or sheet when it is punched through the strip/sheet. The material that is removed becomes the new metal workpiece or blank.
Coining is a forming process that uses an extreme amount of pressure to push the workpiece into a die. The die then forms the metal into a precise shape and creates permanent forms in the workpiece. Coining also smooths the edges of metal parts by striking them with a high degree of force. This removes existing burrs and hardens the metal. Coining may reduce the need for deburring, grinding, and other secondary processes at the end of the project, which saves both time and money.
This process deforms the metal using only a punch and cavity. These dies do not control metal flow and cannot prevent the metal from wrinkling or buckling. They are used to form simple parts, such as brackets and braces, made from thick, stiff metals that are more wrinkle-resistant than thinner metals.
One of the most common stamping operations, cutting trims the metal into a part by the use of extremely high force in the stamping press. Cutting operations include trimming, notching, piercing, blanking, lancing, and shearing.
A complex drawing die is used to create large metal parts, such as automotive components. The process involves controlling the flow of metal into a cavity via a pressure-loaded draw pad to prevent wrinkling as the material flows over a forming punch.
Embossing is a cold-forming process used for creating specific formations or designs on metal pieces. Male and female embossing components press a workpiece between them with sufficient force to form the three-dimensional feature.
Extrusion forms the metal inside the diameter of a pierced hole, which may be used for applications such as holding fasteners during part assemblies.
The flanging operation bends metal along a curved axis, which may be used to form a projection or the rim of a part as it relates to part assembly and stiffness requirements.
Metal stamping involves a variety of forming operations. The stamping press forms the metal material by applying tension, compression, or both. The specific type of forming operation selected depends on the material’s properties and the part’s critical dimensions, balancing formability and strength.
Similar to the coining process, ironing employs compression to form the part by squeezing the metal along a vertical wall to achieve exact thickness and length dimensions.
In order to free up metal without separating it from the metal strip, lancing slices or slits the metal, which may be used in progressive dies as a part carrier.
This metal cutting operation, also called perforating, produces a hole in a formed part or sheet metal, which may be round, square or a custom shape. The slug is then discarded.
Pinch trimming is a special method in which the vertical walls of a drawn or stretched vessel are cut by pinching the metal.
This forming process uses a punch press to force a tool, called a punch, through the workpiece/material to create a hole and produces a scrap slug that is deposited into the die below the sheet metal.
Used primarily after major forming operations are complete, restriking employs an additional station in the die to finish precision details such as small embossing and sharp radii.
An operation used to eliminate or minimize die-break, while maximizing the amount of sheared edge. The general concept with shaving is to pre-punch the hole slightly smaller, then post-punch the hole to size, using a very tight die clearance. This can also be done on a straight or outside edge.
Cutting force is applied perpendicular to the material, causing the material to yield and break.
The trimming process achieves the specified profile of a stamped part by forming its perimeter or cutting away excess metal, with precision trimming designed to minimize scrap.
The method chosen for metal stamping production takes into account the complexity of the part and how metal stamping can best form that part. For precision parts with tight tolerances, the method may include the use of in-die sensors to continually monitor part quality, along with other inspection methods. The method also takes into account secondary operations, such as plating, heat treating, welding, and cleaning or sterilization.
Progressive metal stamping is a stamping process that advances a metal strip from station to station performing different operations on the same part in the die until the part is complete. Conical-shaped pilots are inserted into pre-pierced holes in the strip to ensure the precision of the alignment as the part advances to guarantee the accuracy of the finished product. Since the part is attached to a metal strip throughout its formation, the entire process and parts will be out of tolerance if the strip is off by even a tiny fraction of an inch.
Progressive die stamping offers some advantages such as being a highly repeatable process and since the material is continuously fed into the stamping press, long production runs can be completed, producing more finished parts in less time resulting in lower cost per part.
Transfer die stamping uses one press to operate multiple tools. The part is removed from its metal strip so that it can be freely transferred. A part, which can be turned or rotated, is shaped by each station until it is complete. Automation of the transfer process streamlines the operation into a single press.
Transfer die stamping is typically used for large parts like frames, tube applications, draws, shells, and structural components.
Beneficial for applications requiring recessed cavities, where the depth of the drawn part exceeds its diameter, deep drawing uses blanking, swaging or sizing to deform the base material and apply recessed features.
Fine blanking is optimal for parts that require very smooth, precise edges or exceptional flatness. Fine blanking is particularly suitable for moving parts such as gears. Fine blanking is a combination of metal stamping and cold-metal extrusion techniques, requiring special presses.
Multi-slide / Four-slide stamping is best suited for fabricating complex components that have numerous bends or twists and for forming wire. The difference between multi-slide and four-slide is that four-slide metal stamping machines have four moving slides while multi-slide machines have more than four slides. The slides or rams in the machines strike the material to produce the finished parts.
Multi-slide / Four-slide equipment can manufacture complicated parts with multiple, complex, or over 90° bends and twists including clips, brackets, flat springs, terminals, retainers, and wire formed parts. Both flat and round materials can be formed.
Precision metal stamping provides the accuracy and speed needed to produce a high volume of parts quickly and to precise specifications. A variety of metals, from aluminum to titanium, can be stamped to produce precision parts requiring tight tolerances.
Precision metal stamping often is used to perform a number of operations quickly and cost effectively, including secondary operations in both the die and/or press, which eliminates extra steps and allows for high volume production.
Precision metal stamping is typically used to produce high volumes of custom, complex parts requiring tight tolerances. The list below represents a sampling of precision metal stamped parts, organized by industry.
A key factor in the success of a precision stamped part is specifying the best metal for the process and the application, ranging from lightweight aluminum to heavy-duty steel to high-cost precious metals. OEM engineers can benefit by consulting metal stamping specialists early in the part design phase to evaluate how metal stamping can work and the exact material specifications needed for the application at hand.
Material selection involves evaluating:
Some of the most commonly used materials for precision metal stamped parts include:
Carbon steel is one of the most popular materials used in metal stamping, which can take on many different forms, properties and finishes, offering optimal strength, performance and cost-effectiveness. Each year, steel production exceeds 1.3 billion tons worldwide. Basic steel is magnetic material. With the addition of chrome and nickel to make stainless steel, it loses its magnetic properties. Many different types of steel may be used including hot and cold rolled steel; stainless steel; high-tensile steel; low, medium and high carbon steel; and spring steel.
Aluminum offers many advantages for metal stamping applications. Aluminum has the highest strength-to-weight ratio of any metal. Aluminum conducts electricity better than copper and is non-magnetic. For companies seeking sustainability, aluminum is 100% recyclable without losing any of its natural characteristics. However, aluminum can be abrasive in tooling and is more expensive that steel.
Copper that is suitable for metal stamping comes in many forms, including such alloys as aluminum clad copper, brass, phosphor bronze, beryllium copper and aluminum alloys. Copper is often selected for stamped components and conductors for electronic devices, as well as electrical wiring, heating and plumbing, and other applications that require its extremely high electrical and thermal conductivity. Copper also resists corrosion while maintaining an attractive appearance. The softness of copper makes it one of the best metals for stamped parts.
With its reasonable price and flexibility, brass can work for almost any function in metal stamping. As an alloy of copper, brass can easily be soldered to copper. Brass is highly resistant to corrosion and will not rust. It is also effective in carrying electrical current while dealing with high stress very well. As a result of its unique properties, brass is one of the most-used metal materials in the world.
Titanium is known for its corrosion resistance and high-impact toughness. Titanium is very expensive to manufacture but has the highest strength to density ration of any metallic element. It is often used in aerospace structures and implantable medical devices.
Precious metals may be used as a plating or coating on stamped parts to increase conductivity or to add strength and corrosion resistance to the finished products. In metal stamping, designing a process that conserves the precious metal is critical, due to its high cost and limited availability in some cases. Manufacturers in the automotive, electronics, telecommunications and medical device industries are among the leading users of precious metals such as gold and palladium in critical parts.
Nickel alloys resist high pressure and maintain their properties under extremely high temperatures. They also offer high strength and toughness and excellent resistance to atmospheric corrosion. High nickel alloys are perhaps the most frequently used material for metal stamping production among the hundreds of specialty alloys used in the industry.
Each industry favors particular metals for their precision metal stampings, due to their unique applications and the environmental and operating conditions that the parts must withstand. For example, stamped parts for the automotive industry must be able to hold up under extreme heat and cold, as well as contact with a variety of liquids, while medical devices require high sanitation and safety standards, and electronic parts require electrical conductivity.
Production of precision metal stampings involves a complex process that begins with design collaboration between the stamper’s and the manufacturer’s engineers. Software simulations are often followed by developing a prototype tool to produce sample parts. Full production planning takes into account every step of the process from custom tool design and stamping through finishing and assembly/packaging to ensure that all critical specifications are met, with quality control from start to finish.
Metal stamping engineers can offer solutions for cost-effective part design and production upfront during the estimating process, as they review the part design, prints and material specifications. Using advanced technology, such as 3D CAD, metal stampers can test design options and recommend improvements to reduce failure risk and increase functionality, while meeting all critical specifications and quality standards.
With the development of new custom stampings, it can pay to test and analyze small quantities of stampings before investing in full production. By building a prototyping tool to run sample parts and using simulation software to evaluate how the part and material will function in the tool, the metal stamper can identify and correct potential weaknesses prior to production, which saves on development costs and time to market. The stamper may recommend specialized tool functions, such as progressive dies or in-die assembly, to improve manufacturability.
Collaboration between the manufacturer's technical staff and the metal stamper's engineers in the initial planning stage is key to ensuring efficient production and long-term functionality of the part. In-depth planning sessions allow for review of:
For manufacturers in the planning process for new products, the technical team of the precision metal stamper can add valuable guidance upfront to help speed time to market.
A designated project manager is responsible for ensuring the project is completed on time and on budget and for communicating status updates to the cross functional team.
Tool designers review technical specifications and provide critical feedback for tool design. Once designs are approved, highly complex, high-precision tools are built, often including in-die sensors to ensure tool safety and consistent quality. Tooling experts conduct preventative maintenance to ensure tools last the duration of the program with little or no downtime.
Sophisticated technology is used for high-speed, precision metal stamping, with a variety of presses that are augmented with advanced features such as electronic servo feeds, robotics, and real-time quality control. Multiple operations like in-die tapping, in-die fastener insertion and in-die assembly can be performed in the stamping press, which can eliminate the need for those secondary operations.
Secondary operations are often required to fully finish the metal stamped part for seamless integration into a product or system. Parts may need to be trimmed or welded. Finishing techniques such as coating, plating, polishing or deburring may be chosen to inhibit corrosion, improve appearance, or smooth sharp edges. Metal stampers provide many services in-house, such as cleaning and custom assembly, and also coordinate with approved suppliers for specialized metal finishing services, such as welding or electropolishing.
Metal stamping engineers evaluate assembly and packaging needs in the production planning phase to ensure finished parts are ready for further production or shipment when delivered to the manufacturer. Parts may be shipped fully assembled or as sub-assemblies and packaged based on manufacturer specifications (i.e. reel-to-reel, loose piece, on a bandolier).
Precision metal stampers apply mistake-proof processes that incorporate quality controls into every phase of a metal stamping project. Company-wide information sharing systems ensure quality commitments are understood and implemented by every project team member. Sophisticated quality control technology is leveraged throughout the process to ensure zero defects, such as in-die sensors, real-time statistical process control, and optical vision systems.
The design of a custom tool to produce each new part is critical to success. The tool design is driven by the complexity of the part, the type of stamping method to be used, the expected reaction of the metal to that process, and the anticipated volume and desired run-at rate of parts, among other factors.
Developing a metal stamping tool may require:
Tool maintenance is critical to ensure the tool is in ready-to-run condition throughout the life of the program. Proper maintenance ensures quality tooling and quality parts.
Tool maintenance teams typically:
Advancements in tooling technology include:
Precision metal stampings may require one or more secondary operations in order for the stamping to meet all critical specifications prior to shipment to the OEM. Metal stamping firms may offer a number of these operations in-house, such as cleaning, assembly, and packaging. However, some secondary operations, such as e-coating, electropolishing, heat treating, and plating, require technical expertise and equipment available only through specialized suppliers.
The metal stamper’s engineering team can provide guidance upfront on the best processes for the stamping and its application and will include those secondary operations in its estimate. In addition, the stamper will oversee the secondary operations provided by approved suppliers in order to finish, inspect, package, and ship the stamped part to the manufacturer’s exact specifications.
A precision metal stamper’s quality control system must reach every step of development and production of a stamped part – from the part’s design and prototyping through material selection, custom tool development, production, inspection, secondary operations, and shipment.
Delivering consistent quality requires a robust system to prevent problems and detect variances in real time. The components of a quality control system include:
The following processes are critical to ensuring metal stamping quality.
A metal stamper dedicated to delivering consistent quality will employ a variety of advanced quality control systems and inspection devices, which are used to detect potential problems throughout production in real time.
A valuable tool to ensure quality is a company-wide information system that tracks and documents every step of the process from design to production quality measurements to inventory and shipping. Important documentation and databases should be readily available to employees at the point of use and to provide timely quality reports to customers as required.
IT documentation and databases may include:
The International Organization for Standardization (ISO) certifications ensure that a metal stamper meets the quality management standards required in the global marketplace as well as in specific industries.
Widely used, general standard that requires companies to establish, document, implement, and maintain a quality management system and to continually improve its effectiveness.
Defines requirements for the design, development, production, installation, and service of automotive-related products. The standard is also accepted by other industries such as aerospace and electronics.
Specific to the medical industry, emphasizing the design, process, quality, and manufacturing reliability of medical device products.
Manufacturers of products that are particularly complex or that must meet stringent safety and performance requirements have developed their own quality standards and processes, in such industries as automotive, medical devices, insert molding, and electronics.
Employs Quality Core Tools for metal stampings and other components, including:
Uses a variety of methods to ensure quality, including:
Quality guru Philip B. Crosby, in his book “Quality is Free,” puts forth the ideal of zero defects. He asserts that the quality and inspection department does not ensure quality by itself. Instead, it takes a complete commitment to delivering zero defects from all employees – with a company culture that expects nothing less than perfection.
Ensuring quality, of course, is not free. Management at all levels must demonstrate a commitment to quality by investing in the processes and procedures that deliver quality stampings, time after time.
Best practices for quality metal stampings include:
Manufacturers looking to add or replace a metal stamping supplier face a daunting task of evaluation and selection. While an RFQ is an important step, it’s not enough in itself to evaluate the stamper’s qualifications. When it comes to what drives their decisions, the top ten demands of metal stampers are almost universal among manufacturers – particularly the first three.
Manufacturers routinely demand the following from their metal stamping suppliers:
With price, quality and on-time delivery so critical, it pays to research the company’s track record and to understand the many factors that influence the all-in price of custom metal stampings.
An evaluation of the stamper's qualifications on paper may not be enough to make a final decision. To effectively evaluate whether the metal stamping firm meets their long-term performance standards, OEMs should schedule site visits to one or more metal stamping companies. Technology plays a major role today in the metal stamping industry. It can pay to see the latest technology in action, as well as to assess the team of engineers, technicians, and top management that make the operation run smoothly.
Manufacturers may consider transferring metal stamping tools to a new stamper for any number of reasons. These may include:
However, the transfer can present challenges, especially if it’s a rush request. Understanding the transfer process and allowing sufficient time for evaluation will result in the best outcome.
In order to provide an accurate estimate, the manufacturer will need to supply as much information upfront to the stampers as possible, including:
The stamper’s initial quote will include the cost of running the tool and producing the parts, based on the existing tool and information provided.
The stamper’s engineering team will evaluate whether the tool can be used as is or if a repair or redesign may be required to bring it up to company tool standards. In some cases, developing a new tool may be the best option. In any case, the stamper will provide cost estimates for various scenarios. If it isn’t possible to ship the tool in advance, the stamper can inspect the tool at the customer's location.
With any tool transfer, cost, quality and time factors must be considered. In many cases, the existing tool can be used. However, the tool may be damaged beyond repair, exhibit too much wear, or can no longer meet print specifications. In that case, the stamper may need to build a new tool, which may take advantage of the latest metal stamping technology and operate more cost efficiently.