Custom Metal Stamping | A Comprehensive Guide

13 May.,2024

 

Custom Metal Stamping | A Comprehensive Guide

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.

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Techniques for Shaping Custom Metal Stampings

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

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.

Blanking

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

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.

Crash/Crush Forming

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.

Cutting

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.

Drawing

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

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.

Extruding

Extrusion forms the metal inside the diameter of a pierced hole, which may be used for applications such as holding fasteners during part assemblies.

Flanging

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.

Forming

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.

Ironing

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.

Lancing

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.

Piercing

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

Pinch trimming is a special method in which the vertical walls of a drawn or stretched vessel are cut by pinching the metal.

Punching

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.

Restriking/Sizing

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.

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Shaving

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.

Shearing

Cutting force is applied perpendicular to the material, causing the material to yield and break.

Trimming

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.

Custom Metal Stamping Production Methods

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 Die Stamping

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.

Progressive Stamping Delivers High Speed Production and Lower Costs.

Transfer die stamping

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 dies can handle many part features in one press pass, such as holes, cut-outs or threading, which can eliminate costly secondary operations.

Transfer die stamping is typically used for large parts like frames, tube applications, draws, shells, and structural components.

Is Progressive Die Stamping or Transfer Die Stamping Best for Your Next Precision Metal Stamping Project?

Deep Drawing

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

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. 

Progressive Stamping vs. Fine Blanking: Three questions OEMs Should Ask

Multi-slide / Four-slide Stamping

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.

L E A R N    M O R E 

5 Important Questions to Ask Before Purchasing a Machine Tool

How to effectively reduce the cost of purchasing molds?   For cost control, the first step is to gather information from the personnel in the marketing department about the projected order quantity for the new product. Is it substantial?   During the development review stage of a new product, if the projected order quantity is less than 500,000, it is advisable not to go for hardened molds. Instead, it is recommended to use soft molds, commonly known as trial molds. Soft molds have lower costs, and if the market response is poor, it saves unnecessary expenses involved in making hardened molds.   If the sales market for the product expands later, and there is a significant increase in demand, it is possible to develop a second set of hardened molds during the mass production process of the first set. This is known as duplicate molds. Doing so does not affect the production and delivery schedule of the product. Moreover, there is a clear advantage to this approach: during the development of the first set of molds, the mold manufacturer will accumulate design and production experience. These experiences can be applied to the production of the second set of molds, allowing for significant improvements. Even if you don't request it, the mold manufacturer will undoubtedly proactively make these improvements to avoid unnecessary detours and make the duplicate molds more refined and perfect.   Conversely, if hardened molds are initiated from the beginning of the product approval phase without knowledge of the projected order quantity, it will only increase the mold procurement cost unnecessarily by at least one-third. Additionally, during the engineering design stage, mold costs should be taken into consideration. For example, using S136 steel as the core material or choosing a fine gating system for injection molding will increase the mold cost to varying degrees. Of course, this is except for cases where the product demands high specifications or when the customer specifically requires the use of certain materials and processes.

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