The term die stamp casting combines two different metalworking terminologies.
In fact, dies used for sheet metal stamping are called stamping dies, and they are not produced using casting methods.
There is a specific process used to make dies for metal stamping, and another is used to make dies for casting.
In this article, we take a deep dive into the different types of dies used in sheet metal stamping, discuss how dies are specific to the parts they produce and explain several stamping processes.
Metal casting is often considered an alternative to stamped parts, so we also explain the three most common casting methods and how casting compares to stamping.
What is a stamp die?
Stamping dies are unique precision tools that form and cut sheet metal into a specific shape. These specialty dies are usually made from tool steel but can also be made of carbide or other wear-resistant materials.
A die set assembly will have a male and female component that works in opposition to form or cut the workpiece. The upper half of a die set is mounted on a press ram and delivers the stroke action. The lower half is secured to a bolster plate and press bed.
Stamping dies come in all sizes. Some can fit in the palm of your hand and are used to make micro-electronics. Others are ten feet thick and are used to make car bodies.
Types of Metal Stamping Dies
Stamping dies come in various shapes and sizes, but most perform three basic operations: cutting, punching, or forming.
Cutting is considered the most common operation performed by stamping dies. Sheet metal is fed into the press, and two tool sections bypass each other to cut the workpiece. These sections will have a small gap between them, which is called cutting clearance.
A die set will have different clearances based on the desired edge condition of a workpiece, the sheet metal’s properties, or the specific cutting operation. The most common cutting clearance is ten percent, and it is usually expressed as a percentage of the metal’s thickness. The resulting cut edge is a shiny section referred to as the cut band or shear, and another portion called the break line.
Punching Tool and Die
Punching is often confused with stamping. It is a process that forces a tool, appropriately called a punch, through a workpiece to create a hole. During the punching process, the punch tool will pass through a workpiece into a die. This creates a hole in the workpiece and a slug by-product.
Depending on the material, the slug can either be reused, recycled, or discarded as wasted material.
Punching is the most affordable way to rapidly create holes in sheet metal. Variations of punching include blanking and slugging.
Forming dies are mounted onto a press and used to form sheet metal parts. One part of the die performs the stretching or bending operation while the die block clamps the workpiece and performs a similar stretching or bending operation.
A steel-rule die gets its name from the cutting portion of the die that has steel strips called steel rule. They are also called cookie-cutter dies and are used to cut sheet metals as well as other materials like plastics, cork, paperboard, and wood. The die’s counterpart will have the workpiece’s profile or will have matching grooves for the rule to nest into.
An advantage of using steel-rule dies is their relatively low cost to produce. These dies have a shorter life span than other die types, so they are best used for shorter production runs.
Stamp Die Summary
Die making combines both design and science. Die makers must consider the final part design and sometimes use multiple iterations of a pattern before the final tool and die are finished.
Often, computer applications and design software are used to create die patterns and perform calculations of a design’s effectiveness. These applications can also assure that die designs will be effective and minimize final part design flaws.
To build a successful die, it is also necessary to understand the behavioral characteristics of the metal used to create the workpiece. For example, if you are deep drawing steel, and you used that same process to create a die to work with aluminum, the operation will fail. This is because each metal has different characteristics, so the metal type used for a part will often dictate the tool steel required for the die.
Additionally, different types of sheet metal will require different press speeds, lubricants, and machine capabilities.
Cast vs. Stamped
Cast vs. stamped metals come from extremely different processes. Cast metal parts are made from molten metal that is poured into a premade mold or die that is then allowed to cool. Stamped parts begin as sheet metal that is passed through a tool and die and then pressed, cut, or punched into the desired shape.
What is Metal Stamping?
Metal stamping is a type of cold-forming process. This means heat is not introduced into the die tool or sheet metal. There is a catch, though.
A massive amount of force is required for certain stamping processes, and this generates friction, which, in turn, generates heat. Often, workpieces exit the dies hot.
As mentioned earlier in this article, different types of stamping dies are used in the high volume production of metal parts and components.
Sheet metal used for workpieces is typically 0.020” to 0.080” thick, but some machinery can work with metals as thin as 0.001” or even plates that are almost one inch thick.
Formability of different sheet metals will help determine what material will work best for a specific part as well as the overall die stamp design.
Formability is a metal’s capacity to be bent, drawn, or stretched. When working with metals, this is also known as ductility.
In other words, the metal’s ability to elongate and deform without fracturing.
Factors that influence ductility are:
- The press speed
- Die design
- The press
- Sheet metal feeding mechanisms
- If lubrication is used and type of lubrication
Stamping can be used for both long and short production runs and can be combined with other forming processes. The entire operation is highly automated, which ensures precision and consistency of workpieces.
In many stamping production runs, a series of dies are arranged so multiple operations can be performed with each press stroke. Two dies used in these operations are transfer dies and progressive dies.
For transfer die operations, stock blanks are transferred to each die station with a single die set. Larger stampings are created with tandem press machines where the workpiece is moved from press to press, where different operations are performed.
Progressive dies connect coil stock stampings with carrier strips. These pieces go through different operations and are separated before they leave the press.
Fine blanking creates smooth edges and is highly accurate. This process avoids fractures that result from conventional tooling, and it also creates surface flatness that exceeds other stamping methods. It can be performed on a mechanical press, hydraulic press, or a combination of both. This method operates under higher pressures than conventional stamping.
What are the different types of stamping presses?
Three types of presses are used in stamping operations. These include a mechanical, hydraulic, and mechanical servo.
Mechanical presses come in many sizes that range from twenty to 6,000 tons. They are ideal for creating simple and shallow parts from coils of sheet metal.
They run at speeds of twenty to 1,500 strokes per minute and can create punches from 5mm to 500mm. Mechanical presses are typically used in progressive or transfer stamping on large production runs.
Hydraulic presses provide more consistent pressure and greater control of applied pressure than mechanical presses. They also have adjustable stroke speeds and capabilities.
Presses can run twenty to 10,000 tons and offer stroke sizes ranging from 10mm to 800mm. Hydraulic presses allow for greater stroke length and controlled pressure, making them ideal for deeper and more complex parts. They are also commonly used for smaller production runs.
Mechanical servo presses are used for more complex stamped parts and work faster than hydraulic presses. These presses are powered either by a link-assisted drive system or a direct drive system. The slide position, motion, and stroke are fully controlled and programmable. Of the three machines, we listed, these are the most expensive.
What are the different types of casting methods?
Casting has been around for ages, and many industries use casting for the production of parts found in trains, cars, buildings, and even firearms. For all casting methods, metal is poured or forced into a mold of the desired final component or part.
We talk at length about those processes in our other posts (hyperlink post). These processes are:
Molten metal (non-ferrous) is forced into a die under pressure then allowed to cool into the final part or component. It is popular because of its efficiency and ability to create high quality and consistent parts.
Molten metal (ferrous and non-ferrous) is poured into a mold made of sand then allowed to cool. Parts emerge with a grainy finish, and sand can be reused for subsequent castings. This method is ideal for prototyping and smaller production runs.
Investment Casting: Molten metal (ferrous and non-ferrous) is poured into a ceramic tree then allowed to cool. The nature of the ceramic mold can create highly detailed parts with exceptional finishes.
Casting Dies, What are They?
Die casting is the only casting method that utilizes an actual die. These dies are usually two metal halves that have a void in the shape of the desired part to be cast.
Casting Versus Stamped: How do you know which to use?
Cast compared to stamped processes can both create complex, repeatable parts with close tolerances. Choosing the right process comes down to the final part’s design, material, budget, and production volume.
While stamping can create a high volume of parts at an affordable rate, increased part complexity can quickly add to the overall cost per unit because of the additional tooling and components required.
With casting, there are a number of different methods available that can create the tiniest components found in medical equipment to massive propellers. While die casting can be cost-effective for large runs, if you have a smaller run, you might be limited to sand casting, which requires substantial finishing on most cast parts.
We cover the advantages and tradeoffs of metal casting versus stamping below.
What materials can be used for die vs. stamp?
The metal choice will depend on the application and desired attributes of the final part. Most metals that go through stamping processes maintain their ductility and malleability.
Stamping can accommodate the following metals: Non-ferrous metals, ferrous metals, and non-standard alloys. This is a popular fabrication method for ferrous metals because of their low cost.
All three metal casting methods we mentioned can accommodate a wide range of metals. Die casting, however, is limited to non-ferrous metals.
Some of the most common metals used in cast parts production include aluminum, zinc, titanium, lead, copper, steel alloys, and nickel.
What end products can be created using die-cast vs. stamping?
Stamping is used in a nearly endless number of applications. Stamped products are manufactured for vehicles, telecommunications services, home appliances, aerospace, defense, electronics, and medical equipment. Specific parts range from engine bases to brackets, friction plates, and even electrical terminals.
Similarly, casting is used in many of the same industries, including marine, automotive, industrial equipment manufacturing, mining, and even the oil & gas industry. Various casting methods are used to make turbines, railway braces, powertrains, fuel systems, feeder rolls, and even military launch components.
Strengths of die-cast and stamping
- Lower material costs per pound
- Lower die production and maintenance costs
- High level of automation
- Excellent surface finishes
- Minimized contamination problems
- Produce higher volumes of complex parts
- Reduced waste
- Greater flexibility in part design
- Casting methods are available at affordable rates for both small and large production runs
- Creates parts with exceptional tolerances
Weaknesses of die-cast and stamping
- Material waste from pieces that are cut from the sheet and not used
- No flexibility in shape or thickness of sheet metal
- More complex parts may require additional components, which increases costs
- Longer pre-production process to produce custom stamping dies
- The higher cost of equipment and tooling only makes stamping affordable for larger runs
- Parts susceptible to spring back
- Chance of porosity in metal parts
- Additional inspections required to ensure quality
- Cold chamber, investment, and sand casting all have slower production speeds
- Some methods require secondary operations
It is difficult to weigh the tradeoffs of choosing one method over the other. Both casting and stamping offer manufacturers the flexibility to create nearly any part or component.
Metal stamping offers cost benefits for larger runs, automation for speedy production, and the ability to perform multiple stamping operations for design flexibility.
Casting will have cost savings for certain methods, but this heavily relies on production volume.
So how do you decide?
Redstone Manufacturing specializes in sheet metal fabrication, stamping, and die casting. Our team consultants and manufacturing experts are experienced in guiding our customers towards the right process to meet their unique production goals.
Redstone’s headquarters and sales team are located in the United States. We also have manufacturing facilities in China, India, and Vietnam which means we offer globally competitive prices with a level of customer service you can only get from a U.S.-based company.