The press brake is an indispensable machine tool used in the metal processing industry, and the tooling is the "heart" of the machine. Select toolings for press brake correctly can make all the difference between a flawless bend.
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The tooling of a standard press brake is divided into two parts. The tooling installed at the top of the ram is called the upper punch, and the tooling installed at the bottom of the worktable is called the bottom die. The upper punch and bottom die, two parts, work together on the metal sheet to complete the bending of the workpiece.
The process of the upper punch of the press brake applying force to the metal sheet on the bottom die is the bending process. The top tool drives the ram to bend the metal sheet through different power sources. The driving sources include mechanical, hydraulic, servo motors, etc.
Choosing the right press brake tooling for the job can not only improve processing accuracy and efficiency but also extend the service life of the die and equipment, reducing production costs. In some situations, the wrong tooling can even damage the machine itself.
This article will start with the importance of choosing press brake tooling, and analyze the key factors affecting the selection, as well as subsequent maintenance and care, to assist in easily press brake tool selection.
There are different types of high-quality press brake punches and dies. Understanding the anatomy of press brake tools is fundamental for manufacturers aiming for precision and efficiency.
Standard tooling is also convenient to replace, as the design of tooling parts with standard dimensions is consistent. This eliminates the need to make too many adjustments when replacing the punches and dies, as these toolings are kept in the same position for easy replacement.
The upper parts of the ram of the bending machine require a clamping device for fixing the punches. Clamping fixes the punches in the required position, allowing them to bend the metal plate with the motion of the ram.
Die segmentation can facilitate the bending process of various-sized workpieces. Press brake toolings require very high accuracy, particularly the accuracy of punch tips and die shoulders, as these parts will directly contact the sheet metal during bending.
Punches and dies with high precision can reduce adjustments in the installation process. Incorrect tooling results in more set-up time, additional processes needed to get accurate bends.
Press brake dies include V-die, U-die, and Z-die, with V-die being the most common. The minimum flange length should be at least 4 times the material thickness; otherwise, the exact bending angle cannot be obtained.
V-die sets with different opening widths match the corresponding punches, allowing the press brake to bend at different angles and materials. In this way, the press brake can bend at different angles and with different materials.
Press brake tooling is classified into 2 types: punch and die.
Dies also come in a wide range of types. Which you choose will depend on your fabrication needs but you also need to consider the parameters of your press brake.
American Precision Style Tooling, featuring a 0.500-inch wide tang, is one of the most traditional and widely used types in North America. This style is known for its straightforward design and ease of use.
European Style Tooling, with a 13mm wide tang and a rectangular section groove on the side of the punch facing the operator, ensures high precision and secure locking, making it ideal for CNC press brake operations.
Wila Trumpf Style Tooling features a 20mm wide tang with grooves on the front and back of the tang. Known for its high-speed changeover mechanisms and precision, it offers several benefits.
Bevel Tang Style Tooling is designed for newer Amada Style press brakes, featuring a punch tang with an angle to fit properly with the receiving clamp.
Secure Fit and Versatility: The beveled tang ensures a reliable and precise fit, reducing the risk of tool slippage. It is also compatible with a wide range of dies, offering flexibility in tooling options.
Choosing the right tool starts with considering the material type and thickness of the material being bent. Thicker materials need dies with wider openings, while thinner materials require more precise dies for accuracy.
The right press brake die can be chosen by calculating the right die opening (ideally, 8 times the material thickness and never less than 6). It's crucial to know the tensile and yield strength of the material. For example, stainless steel needs stronger tooling than aluminum.
Accurate calculation of the bending angle and required force is essential for successful operations. Different methods like air bending, bottom bending, and coining each have unique force and angle requirements. Ensure the required bending force is within the press brake's capacity to avoid damage.
Matching tooling with the press brake's tonnage capacity is vital for efficiency and tool longevity. Ensure the press brake can handle the required tonnage to avoid overloading. Choose tooling that can withstand the maximum tonnage to prevent wear or breakage.
The tooling profile must suit the job, and both the tool and press brake load limits must be considered. Some profiles are stronger and better suited for specific applications, like V-dies for various angles. Ensure the tooling can handle the maximum load to avoid deformation.
Different tooling styles offer various features and benefits, so choose one that matches the press brake machine and tasks.
Ensure the tooling system is compatible with the press brake machine. Check that the tool mounting options fit the press brake machine. Determine if any modifications or adapters are needed for proper installation.
Safety and durability are crucial in punch and die selection to minimize risks. Invest in high-quality, durable tooling materials. Ensure correct tool fitting to prevent accidents and ensure consistent performance.
High accuracy and precision in tooling are essential for consistent results. Look for precision-ground tools and self-centering capabilities for better accuracy.
Choose tooling that is easy to set up and use to improve productivity. Quick-change tooling options and user-friendly adjustments reduce downtime.
Balance the cost and value of the tooling for long-term investment. Consider the initial cost, but prioritize value and performance. Include maintenance expenses in the long-term value assessment.
Choose a reputable supplier that offers excellent support and service. Ensure the supplier provides technical assistance, training, and prompt support.
The type of metal you want to bend is an important factor. The thickness of the metal determines the die opening, bending radius, and bending angle.
For example, some steels have greater strength and resistance than others, and this resistance is called the tensile strength (UTS) of the metal. The tensile strength of metals is different, which requires different strength molds.
In addition, the length of the metal plate determines how many toolings are required. Another factor is the thickness of the metal. Tools designed for sheet metal may not be suitable for thicker materials and may cause premature wear or damage to tools and press brakes.
When bending sheet metal, if the thickness and metal type are the same, there is not only one V-die opening size. The sheet metal must not be lost during bending.
If the internal radius is less than the thickness of the metal plate, the plate will be stretched, leading to workpiece deformation.
A radius greater than the thickness of the sheet will not cause deformation. When choosing the perfect V-die opening, we should not only avoid radius deformation but also choose a smaller radius.
There is a rule of thumb applicable to the V-opening of press brake dies, known as the rule of 8. The rule of 8 is based on 60,000 PSI tensile cold-rolled steel and stipulates that the V-opening die shall be eight times the thickness of the bending material.
The rule of 8 applies to most bending processes. Within the specified tonnage range, an internal radius approximately equal to the thickness of the material can be produced.
However, this is not a perfect law, because the factor will increase or decrease with the variation of the material thickness. As a result, the width of some V-die openings is 6 times, 10 times, or even 12 times the thickness of the material.
Thicker plates usually require a V-opening of 10 times the thickness to distribute the force over a larger area and avoid cracks in the plate due to its reduced ductility.
Before determining the press brake dies, first determine the thickest and thinnest metal sheet to be bent, and use the rule of 8 to determine the correct size of the V dies.
Select the smallest V die and double its size to determine the next V die until the maximum mold is reached. If an exact match cannot be found, the dimensions should be rounded to the nearest available mold.
The V opening of the press brake dies affects the radius of the bending material. In general, it is ideal for the internal radius of the material to be equal to its thickness.
If the inner radius is less than 1 thickness, it means that the material extracted from the radius disappears. In plate bending, if the inner radius is less than 1 thickness, a "side bulge" can appear at the bend.
The larger the V-die opening, the larger the radius of the metal plate. However, the tensile strength of the material will also affect the radius. On a given V-die opening, the stronger the material, the greater the radius.
On mild steel, the bending radius (R) is usually 1/8 of the V-die opening, resulting in the following formula: R = V/8. However, this rule will vary for different metal types.
When selecting V-shaped dies, it's important to pay attention to the flange length or leg required by the workpiece. During bending, the sheet metal must always be in direct contact with the shoulder of the die.
If the flange length is less than the specified amount, it will fall into the V-shaped opening, leading to inaccurate bending results. Therefore, the larger the V-shaped opening, the larger the minimum flange or leg required on the metal plate.
The minimum flange formed by a V-die is about 70% of the opening of the standard V-die, while an acute angle die can reach 110% or more of the V-die opening.
Before determining the minimum flange length, the sheet metal should be placed on the die, so that the material contacts the die shoulder at a point equal to 20% of the V-die opening.
The factory needs to process the 304 stainless steel plates with a thickness of 2 mm, a bending angle of 90°, and a bending length of mm. Considering the high solidity of stainless steel, spring back occurs (parts of materials return to their original shapes after bending because of elastic deformation).
Thus, the R4 v-shaped mouth dies (the contact surface between the upper punch and bottom tool shows v-shaped, and the radius of the v-shaped mouth is 4 mm).
At the same time, SKD11 material (a high-quality, high carbon high chromium tool steel) is chosen to improve the abrasiveness and lifespan of the press brake. After trial processing, the size accuracy and surface quality of the press brake have achieved the requirements.
Automative equipment factory needs to process -T6 aluminum alloy plate with a bending angle of 120° and plate thickness of 3 mm. Due to the softness of aluminum alloy material, there will be indentation and peeling ( Partial bulges on the surface of the material).
After testing, the R8 U-shaped mouth die (the contact surface between the upper punch and bottom die shows U shaped, U-shaped mouth radius is 8 mm) is chosen, and the surface of the die is carried out with nitriding treatment (a surface heat treatment process that can improve the surface hardness of the die).
Meanwhile, the bending force is decreased properly during bending, and the die surface is painted with lubricating oil. The final surface of the aluminum alloy plate is smooth and clean, with no obvious deflection.
The material of the tooling is an important factor in improving the quality of the workpiece and extending the service life of the tooling. The material cost of toolings varies depending on factors such as workpiece material and bending accuracy.
Selecting the right steel grade for press brake tooling is crucial for ensuring optimal performance, durability, and compatibility with specific bending tasks. Below are some commonly used steel grades along with their properties and applications.
Chromium molybdenum steel, often referred to as Chromoly, is highly regarded in the industry for its exceptional strength, corrosion resistance, and long service life. These properties make it suitable for a wide range of press brake applications, including heavy-duty bending operations.
T8, T10, 42CrMo, and Cr12MoV steels are known for their high strength and hardness. They are especially effective for heavy-duty bending operations where precision and durability are critical.
Alloy materials enhance certain properties like hardness, wear resistance, and toughness in press brake tooling. Commonly used alloys include:
Low alloy tool steel often contains elements like tungsten carbide and cobalt, making it hard and wear-resistant. This combination results in a material that is ideal for high-frequency and high-precision bending tasks.
This material combines the hardness and abrasiveness of carbide with the toughness and workability of steel. It offers a balance between these properties, making it suitable for applications where both wear resistance and toughness are required.
For demanding applications, high-performance materials are preferred. These include:
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High-speed steel (HSS) and cemented carbide are known for their high hardness levels, making them ideal for high-precision and high-wear applications. Though more expensive, they provide longer die life and better overall performance.
Tungsten carbide is valued for its high wear resistance and durability. It is often chosen for its cost-effectiveness relative to its performance, making it suitable for demanding bending operations.
When selecting the right material for press brake tooling, consider several key properties:
Hardness is crucial for maintaining sharp edges and resisting wear. Materials like HSS and cemented carbide are preferred for their high hardness levels, essential for high-precision applications.
Toughness is vital to prevent die cracking and deformation under high stress. Materials such as low alloy tool steels and Chromoly are known for their excellent toughness.
Materials with high wear resistance, such as carbide and high-speed steels, are essential for high-volume operations to ensure the tooling lasts longer and maintains its performance over time.
Choosing the right material for press brake tooling involves evaluating several criteria:
The choice of tooling material should be tailored to the type of metal being bent. For example:
For high-volume operations, materials like carbide or high-speed steels are preferable due to their superior wear resistance and durability. For projects requiring tight tolerances, precision tooling is essential to meet the design specifications of the end product.
The selection process must balance performance needs with cost constraints. Carbon tool steels are affordable and durable, making them suitable for standard bending tasks, while high-performance materials like HSS and cemented carbide are more expensive but offer longer die life and better performance.
The tooling must be compatible with the specific press brake machine being used, considering factors such as clamping style, maximum tonnage, and working length to ensure secure fitting and optimal performance.
Generally speaking, high-quality tool materials include hardened steel, high-speed steel (HSS), and tungsten carbide. Hardened steel is durable, wear-resistant, and can withstand large weights. High-speed steel is wear-resistant, has a long service life, and has a higher cost than hardened steel. And tungsten carbide is the highest in quality and cost.
The toolings of the press brake need correct maintenance and storage to extend its service life and ensure bending quality.
Proper handling and cleaning of press brake tooling are crucial for maintaining its performance and extending its lifespan. Press brake operators should always wear gloves to prevent oils and residues from their hands from causing damage.
After each use, thoroughly wipe down the tooling with a cleaner or isopropyl alcohol to remove any residues, resins, or metal particles that might cause wear and tear. Wipe them with a soft cloth, and use an anti-rust spray regularly. An abrasive pad can help remove any flakes or coatings left behind by materials like mild steel or aluminum.
Effective storage practices are essential for protecting press brake tooling from damage and corrosion, ensuring tools are securely placed in cabinets made of metal or semi-solid materials. Fix and isolate each punch and die with foam or plastic.
Avoid wooden cabinets, as they can introduce moisture and cause corrosion. For convenience, store the cabinet near the press brake. If tools are used across multiple machines, consider using a mobile cabinet.
Vertical storage systems can save floor space and enhance storage capacity, featuring configurable shelves, adjustable separators, and safety mechanisms to prevent multiple shelves from opening at once.
Regular maintenance is crucial for ensuring the longevity and performance of press brake tooling. Regular inspections help identify signs of wear, damage, or deformity early on, preventing significant problems that could affect performance and damage the workpiece.
Cleaning tools after each use to remove residues and prevent contamination and rust is essential. This ensures the tools are ready for the next job and maintains their condition. Regular grinding may be necessary to keep the tooling edges sharp and precise.
After cleaning, lightly rub down the tools with a lubricant before storing them to protect against corrosion and ensure they remain in good condition, ready for their next use.
Ensure the tooling is compatible with the press brake machine's parameters, such as clamping style, maximum tonnage, and working length. This compatibility prevents damage and ensures efficient operation.
To preserve tooling and ensure safety, park the press brake ram in the bottom position when not in use, resting its weight on blocks rather than the tooling. At the end of each workday, wipe down back gauges, guides, and other surfaces with a dry cloth.
Use safety features like locking enclosures and lock-out mechanisms to prevent loss and ensure operator safety during tool access and storage.
When selecting press brake tooling, several key factors must be considered to ensure optimal performance, safety, and efficiency.
Chromium Molybdenum Steel (Chromoly) is the best material for press brake tooling, offering superior strength and corrosion resistance. High-quality tool steels like T8, T10, and 42CrMo are also excellent choices for their hardness and wear resistance.
The toolings of the press brake impact the shape and quality of the bending workpiece. Select suitable toolings for the material before bending. Determine the die's shape, angle, and opening size based on the workpiece. Correct tooling and material use enhance bending accuracy.
They affect the bending angle, internal radius, flange length, and workpiece appearance. Correct tooling improves efficiency, reduces cost, prevents deformation, and ensures operator safety.
Tooling manufactured by reliable brands addresses denting and deformation issues. Branded tools offer better honing and longer life. If unsure about press brake or tooling choice, contact ADH Machine Tool.
As a 40-year-experienced press brake manufacturer, we provide high-quality bending machines and comprehensive bending solutions. Visit our product page to learn about our press brake series and toolings. Our team is ready for technical support.
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What follows is just a sampling of questions I receive regularly. Keep the questions coming! There&#;s always more to learn, and the more you know, the more there is to know. It&#;s a lifelong adventure. Keep learning, my friends; it makes life much more productive.
Question: Usually we will form the bend radius so that it equals or is greater than the material thickness, but it also can be less than the material thickness. My doubt is why the inside bend radius should be considered equivalent or greater, and how does the K-factor and the neutral axis play a role in all this?
Answer: Many types of sheet metal have minimum bend radii assigned by the producer of the material. They include some aluminum alloys for which Alcoa and others list recommended and minimum inside bend radii by the specific makeup and characteristics of a given material.
An inside bend radius that we would consider a sharp bend can cause the material to develop stress cracks along the outside radius. These stress cracks are the manifestation of the grains in the metal tearing apart.
The material is expanded on the outside of the bend, compressed on the inside. The area that neither expands nor compresses is the bend&#;s neutral axis. Its length remains the same, but it does change position; it moves toward the inside surface of the bend.
How much it shifts depends on the material type and the method of forming: air forming, bottom bending, or coining. Figure 1 gives you a multiplier that, when applied to the material thickness, tells you the location of the relocated neutral axis.
An average and commonly used value for the K-factor is 0.446. We multiply this factor by the material thickness to determine the distance the neutral axis shifted toward the inside radius during bending. If a material is 0.062 in. thick, we multiply this thickness by the K-factor to arrive at 0. (0.446 × 0.062). This tells us that the neutral axis moved from 0.031 in. (at half the material thickness) to 0. in., or 0. in. closer to the inside radius (0.031 &#; 0. = 0.).
It does not seem like much, but it is enough to cause the bend to elongate. This is the reason the flat part is always smaller than the total outside dimensions of the formed piece (see Figure 2).
The sharper (smaller) the inside bend radius, the greater the stress on the material becomes on the outside of the bend. This increases the odds of cracking and part failure in the field. With bend radii equal to or greater than the material thickness, the less stress you put on the outside of the bend.
Also, if the bend radius is too small and too sharp, and the tonnage to form is too high, the punch nose radius will crease the center of the bend. This amplifies angular variations that occur because of changes to the material properties, such as thickness, grain direction, and hardness.
A bend radius that&#;s close to the material thickness will give you the most stable forming results, including consistent bend angles and final dimensions. That&#;s why it&#;s considered a perfect bend.
There are sound reasons for keeping the inside bend radius more than what would be considered a sharp bend and to use a K-factor value that is consistent with industry standards and applications. For more on this, you can refer to &#;What makes an air bend sharp on the press brake?&#; from November and &#;A grand unifying theory of bending on a press brake, Part I,&#; from September , both archived at thefabricator.com.
Question: I read your article about why tonnage matters, and I have a question about the formula:
{[575 × (Material thickness)2]/ Die width}/12 = Tonnage per inch. Could you please explain where the 575 comes from and how the required angle factors into the formula? Do tonnages change if you are making an 85-degree bend versus a 125-degree bend?{[575 × (Material thickness)]/ Die width}/12 = Tonnage per inch. Could you please explain where the 575 comes from and how the required angle factors into the formula? Do tonnages change if you are making an 85-degree bend versus a 125-degree bend?
Answer: I have been unable to determine the origin of this tonnage formula. However, I do believe it dates back to the s and most likely from the construction industry.
That 575 refers to the yield strength of mild cold-rolled steel. Today we have a large number of material types, and we multiply the result of the tonnage formula by material factor to get an accurate answer.
The basic formula you mention is for air forming cold-rolled steel. If you are bottoming, the tonnage is 3 to 5 times that of air forming, and if you are coining, the tonnage is 10 times or more. (For the complete formula incorporating factors for different material, forming methods, and special tools, check out &#;The 4 pillars of press brake tonnage limits&#; from April , archived at www.thefabricator.com.)
Our baseline is cold-rolled steel with a tensile strength of 60 KSI. You can go to the web, check other materials&#; tensile strength, and adjust your program accordingly. You do this by simply dividing your material&#;s tensile strength with the baseline of 60 KSI (or 60,000 PSI). For example, if your material has a tensile strength of 120 KSI, you divide that by 60 and get a material factor of 2.0. If you are working with soft aluminum with a tensile strength of 30 KSI, you divide that by 60 KSI and get 0.5 as your material factor.
The working tonnage calculations are made at the point on the stress-strain curve where the proportional limit of the material is, followed by a small increase in load as the yield point of the metal is reached. This is the value we use to compute forming tonnage.
And, yes, the tonnage required to form will change some when you are making an 85-degree bend versus a 125-degree bend. Still, once you bend past 20 degrees complementary, you already are using most of your forming tonnage anyway. In fact, about 80 percent of total forming tonnage is achieved within the first 20 degrees of the bend angle. In other words, even with a slight angle, a bend can put immense pressure on tooling and equipment.
Question: We bend alloy sheets ranging from 0. to 0. in. thick, with a radius that equals the material thickness. The punch is 88 degrees and the die 60 degrees. I can never get a 90-degree bend without having to compensate. What would be the optimal angle combination? And what would the perfect die opening be&#;8 times the material thickness?
Answer: You, sir, are doing something that is very, very dangerous, especially if you are using precision-ground tooling. However, there is a safe way to select your tooling; it is also the solution to your bending problems.
If the punch angle is the larger angle, it places heavy tonnage load along the top radii of the die&#;that is, the two top edges on either side of the opening (see Figure 3). In doing so, you create a fair amount of side thrust that will, if it hasn&#;t already, blow up the punch, the die, or both!
If you are using traditional planed-style tooling, you may hear a loud bang followed by the tooling falling to the floor&#;probably right on your foot. But if you&#;re using precision tools, watch out. Some precision tools can have Rockwell hardness ratings of 60 or even higher. If you blow a tool, it will throw shrapnel a long way!
OK, now that I&#;m done yelling at you, here&#;s what you need to do. First and foremost, your punch must have an included angle that either matches or is less than the die angle! You need clearance between the punch and die!
Finding the perfect die opening involves much more than the 8x rule&#;that is, simply using a die opening that&#;s 8 times your material thickness. Nonetheless, your material is 0. in. and the called inside radius is the same. This creates a 1-to-1 relationship between the inside bend radius and material thickness, what we call a perfect bend. It is the most stable of the radius-to-material-thickness relationships.
To find a geometrically perfect die opening, refer to the following formula:
(Outside radius of the material in inches) × 3. = Geometrically perfect die openingYou find the outside radius by adding the inside radius to the material thickness. From there you select a standard die opening that is closest to that value. You then take that number and calculate the forming tonnage, inside radius, and bend deduction. A note of caution: If you use a die width that is less than perfect, your loads will increase&#;sometimes dramatically.
In this case, I&#;m assuming you&#;re working with cold-rolled steel with 60-KSI tensile strength, which forms its radius at about 16 percent of the die opening. (For more detail as well as how to determine the floated radius for other materials, see &#;How the inside bend radius forms,&#; archived at www.thefab ricator.com.)
For your 0.-in.-thick material with a 0.-in. inside bend radius, the outside bend radius would be 0. in. Again, this is the inside bend radius plus the material thickness. Plug the outside radius into the formula and you get an optimal die opening of 0. in. In this case, I recommend air forming over a 0.275-in. die opening with a die angle that is 90, 88, or 85 degrees included. In an air form, this will result in developing a 0.04-in. inside radius in the workpiece (0.04 is 16 percent of 0.275; that is, 0.275 × 0.16 = 0.04). This radius value would then be used to calculate your bend deduction. Assuming you are air forming, the tonnage for this combination would be 0.178 U.S. tons per inch or 2.133 U.S. tons per foot.
As for the punch, I recommend a 0.-in. (1-mm) nose radius and an included angle that is 2 degrees less than the angle you chose for your die. This punch angle will give you clearance. It also will lower your forming tonnage and allow you to quickly make a 90-degree bend without you having to lie to the controller.
As for the 0.-in.-thick material, the same rules for tool angle and punch-nose radius apply. This time, you should use a 0.472-in. (12-mm) die width. This will give you around 0.285 U.S. tons per inch or 3.416 U.S. tons per foot, again assuming you are air forming. The inside radius will be 0.075 in. (again, 16 percent of your die opening), which you then use to calculate your bend deduction.
Steve Benson is a member and former chair of the Precision Sheet Metal Technology Council of the Fabricators & Manufacturers Association International®. He is the president of ASMA LLC, steve@theartofpress brake.com. Benson also conducts FMA&#;s Precision Press Brake Certificate Program, which is held at locations across the country. For more information, visit www.fmanet.org/training, or call 888-394-. The author&#;s latest book, Bending Basics, is now available at the FMA bookstore, www.fmanet.org/store.