Selecting the right press brake tools is essential for achieving precise results in sheet metal bending operations. Press brakes are a cornerstone in modern metal fabrication, and their widespread use has led to a variety of tooling options designed to accommodate different lengths and shapes of bends.
This article will delve into the specifics of selecting press brake tools. The insights provided will benefit both novice operators and seasoned professionals in the field. You will gain an understanding of the materials used for press brake tools, the various styles available, different types, and key factors to consider when choosing the right tools for your press brake.
What Are Press Brake Tools?
Press brake tools are the equipment like dies and punches used in the press brake to create the bend in a sheet metal. Press brake tooling is not built into the machine. It is rather a swappable part of the machine that is used based on the particular type of job. Press brake tooling is the accessory that actually comes in contact with the workpiece.
What is the Main Purpose of Press Brake Tools?
The main purpose of press brake tools is to make the machine suitable for varying metal bending jobs. Without press brake tooling, one press brake machine will be very limited in the type, shape, and size of the bend it can perform.
However, press brake tooling expands the applications of the machine. Different bend angles and radii can be formed by simply changing the tooling. Therefore, press brake machines can quickly adapt to changing jobs.
What are the Key Elements of Press Brake Tools?
There are many different elements that work together for a press brake machine to work. These different elements are:
Top Tooling Types (Punches)
A punch is the tooling present on the top of the workpiece. It exerts the force on the workpiece that is necessary for the bend. It is extremely important to use good-quality punches since they are the central part responsible for exerting the force necessary in the metal bending process.
There are many types of punches available for different jobs. The punch selection should be made only after knowing the basics of each type of press brake punches. These different punches are:
Standard Punch
Standard punch is the most widely used press brake tooling. Its thicker body and narrow punch tip exert a higher tonnage that is useful for bending thickest material. The inward side has a slight concave curve with flat outsides. This provides the ability to fold a shorter flange.
Acute Angle Punch
Acute angle punch is used to bend very short angles. Acute angle punches are commonly shortened as acute punches. Usually, these punches are applied when the bend angle required is 30° or less. These punches can also easily bend larger angles such as 60°. These punches have a sharp tip with a generally bulky body.
Narrow Punch
A narrow punch is uniform throughout its length with a low thickness. These punches are used where there is a little clearance available and other punches might not fit easily. It is also known as a sword punch. A common application of a narrow punch is when closing off a square or box type profile.
Sash Punch
A sash punch is a type of tooling with a very narrow body and an angled tip that is bent towards the inside of a press brake. The angled tip provides the ability to work around corners and create bends. A common application of a sash punch is for making door jambs and sashes.
Swan Neck Punch
A swan neck punch is used for marking applications. They are used to create niche U profiles in the workpiece. The shape of the swan neck punch is specially created so the legs of the bent workpiece do not collide with the tooling. A variation of this style is the gooseneck punch, also used for U profiling. The niche shape of the swan neck and gooseneck punch creates an unsupported line of force. Therefore, these punches are weaker compared to other alternatives. They can handle a lower tonnage.
Joggle Punch
Joggle punch is a press brake special tool used for making bends around the corner. Joggle punch has a thinner profile, making it extremely useful for creating S-shape bends. These are not very common punches, often used for niche punch selection jobs.
Radius Top Punch
Radius top punch has a rounded tip instead of the sharp tips that other punches have. This creates a U-shape bend instead of a sharp V-shape bend. This punch is usually combined with a U-shape die for a properly-rounded corner.
Bottom Tooling Types (Dies)
A die is a hollowed tooling placed under a workpiece to provide support and precision for the bending process. Dies absorb all the force exerted by the punch. Therefore, these are also made of high-strength materials. Many different shapes and sizes of dies are available to suit various operations. Common die shapes are:
Single V Die
A single V die has a ‘V’ shaped cavity hollowed into the tooling. They are also stylized as single ‘Vee’ die. They are the most used press brake die due to their wide versatility. Single V die selection is done on the basis of rule of 8. It states that the length of the V die opening should be 8 times the material thickness.
Two-Way Self-Centring V Dies
Two way self centring V dies have two V-shaped cavities placed in parallel. This provides a faster workflow as compared to a single V die. There is no requirement for retooling in case another bend angle is required.
Multi V Die
Multi V die configurations have a number of V cavities arranged around the die. The number of V-cavities can range anywhere from 3 upwards. A multi V die adds the variety of bending options available in a single tooling. Changes in bend angle or material thickness can be accomplished by a simple rotation of the die.
Corrugating Dies
Corrugating dies have a corrugated pattern at the bottom. These dies are used in niche requirements where the bent sheet metal requires the same pattern on the outer surface.
Flattening & Hemming Dies
A flattening and hemming die is used to fold the entire flange length in an acute angle bend and flatten it completely. The bottom tool comes in two variations, namely sprung loaded and U-section bottom tool.
Channel Forming Dies
A channel forming die creates a ‘U’ shaped channel on a flat sheet metal. Creating a U-shape channel requires two passes of traditional V dies. However, a channel forming die can accomplish the job in a single pass.
Tool Holder
A press brake tool holder is a very useful accessory for mounting the tooling on the press brake. Modern tool holders come with productive features such as quick tool changes. A good quality tool holder also increases the precision of the bending process by minimizing tool vibration.
Backgauge
The backgauge of a press brake is used to precisely align the workpiece for an accurate bend. The backgauge is movable in the X-axis. The backgauge has multiple pieces of finger stops and blocks. These backstops will cease the bending process once the required bending length is achieved. A correct backgauge setup improves the repeatability and consistency of the press brake bending process.
Crowning System
A crowning system is a type of press brake tools that compensate for the deflection caused during the deformation of the ram and the workbench during the bending process. A crowning system is especially indispensable when it comes to large sheet metal bending due to the high deflection involved.
Efficiently using the crowning system requires an understanding of press brake deformation and deflection. There are two different types of crowning systems available: hydraulic crowning system and mechanical crowning system.
Press Brake Safety Devices
Press brake safety devices are secondary tools installed on the press brake for ensuring the safety of the operator, the workpiece, and the machine itself. Different press brake models come with different safety devices. Common press brake safety systems are:
- Laser Sentry: Laser sentry places multiple laser beams around the die. When any presence interrupts the laser beams, the laser sentry causes an immediate halt of machine operation and retracts the die. This provides a high level of safety to the operator and ensures that operator limbs aren’t harmed in the press brake work flow.
- Light Curtains: Light curtains are a common presence sensing device that provide automatic safety to the operator without any required setup. These work similar to the laser sentry system. When the flow of light curtains is interrupted, the safety system stops the machine operation at once without any delay.
- Guards: Press brake guards are present on the side and the rear end of the machine. Side guards prohibit the entry of operator arms or any foreign object between the die and the punch. Rear guards prohibit interference with the backgauge and other components behind the press brake.
- Two-Hand Control: Two-hand control requires the operator to use both hands to start the press brake cycle. This ensures that the operator does not accidentally start the machine when one of their hands is in between the die opening and the punch. Two-hand control is cheaper than laser sentry and light curtains. However, it slows the speed of the whole operation slightly.
Structure of the Press Brake Tools
Press brake tooling are divided into the punch and die, which are used for sheet metal stamping forming and separating molds. The mold used for forming has a cavity, and the mold used for separation has a cutting edge.
Material selection:
Generally use T8 or T10, T10A, and the better 42CrMo material, it mainly requires high strength, high toughness, and good wear resistance. Cold work dies steel Cr12MoV is a good material. The use performance can be satisfied, and the process performance is good, the price will be higher 42CrMo is a high-strength alloy quenched and tempered steel with high strength and toughness and can work below 500 degrees.
Terms of use:
1.Turn on the power of the bending machine, turn the key switch, press the oil pump to start, and the bending machine oil pump starts to rotate. At this time, the machine has not yet started to work.
2.The stroke adjustment requires a trial run when the bending work with the bending machine mold is officially started. When the upper die of the bending machine descends to the bottom, there must be a gap of plate thickness. Otherwise it will cause damage to the mold and the machine. The stroke adjustment also has electric quick adjustment and manual fine adjustment.
3.For the selection of the notch of the bending machine die, a notch of 8 times the width of the plate thickness is generally selected. If you bend a 4mm sheet, you need to choose a slot of about 32.
4.Check the overlap and firmness of the upper and lower molds of the bending machine; check whether each positioning device meets the requirements of being processed. Frequently check the overlap of the upper and lower molds; whether the instructions of the pressure gauge meet the regulations.
5.When the sheet is bent, it must be compacted to prevent the sheet from lifting and hurting the operator during the bending.
6.The power supply must be cut off when adjusting the sheet metal die, and the operation should be stopped.
7.When changing the opening of the lower die of the variable bending machine, no material is allowed to contact the lower die.
8.It is forbidden to use bending machine dies to bend over-thick iron plates or hardened steel plates, high-grade alloy steels, square steels, and sheets that exceed the performance of the sheet metal bending machine to avoid damage to the machine tool.
9.Turn off the bending machine, and place wooden blocks on the lower molds under the cylinders on both sides to lower the upper slide plate onto the wooden blocks. Exit the control system program first, then cut off the power supply.
Installation adjustment:
When installing the press brake tooling, be sure to check the status of the equipment, and then install and debug according to the steps, and pay attention to personal safety when debugging.
Machine adjustment: When installing the press brake tooling, you must first understand the performance of the machine, turn on the bending machine, adjust and check patiently, and see if the machine has previously used dust and iron chips. Prevent unnecessary trouble for later use.
Slider stroke adjustment: First check whether the ratio between the thickness of the bending machine mold and the upper and lower modules is normal. The general slider needs to be controlled at the switch point of the stroke line. This must be paid attention to, otherwise, the mold will not be used normally, but some people still make such mistakes often.
Stroke module adjustment: After adjusting the slider stroke standard, the next step is to adjust the upper limit point of the module. Generally speaking, when the module is up to the highest point, the module and switch must be set. In this way, the staying position of the module can be flowed out, and through some of the above operations, the production efficiency can be greatly increased. In this process, the module also needs to be slowed down. Because the module must be decelerated when it is down to the bottom dead center, which protects the machine and the mold.
Adjustment of the gap: Finally, the gap between the molds of the bending machine is adjusted. The gap between the upper module and the lower module is measured first, and the reasonable gap needs to be determined according to the folded plate.
Angle adjustment: Adjusting the bending angle is also the most important link. The angle selection must be related to the product requirements. Generally speaking, when bending a 90° mold, the angle must be set to be greater than the angle between the two sides. Sometimes it may be tight. It can be handled by adjusting the screws on the machine. After the adjustment, if the product does not change the demand, do not modify it again. Then, when bending, use the pressure gauge to calculate the accurate pressure number and adjust the pressure. So as not to cause mold chipping.
Press Brake Tooling Operating Procedures
Press brake tooling is divided into manual bending machine molds, hydraulic bending machines, and CNC press brake tooling. Hydraulic press brake toolings can be divided into torsion axis synchronization, machine-hydraulic synchronization, and electro-hydraulic synchronization according to the synchronization method. Hydraulic press brake toolings can be divided into the up-moving type and down-moving type according to the movement mode. Including bracket, workbench, and clamping plate. The workbench is placed on the bracket.
The workbench is composed of a base and a pressing plate. The base is connected with the clamping plate through a hinge. The base is composed of a housing, a coil, and a cover, and the coil is placed on the housing. Inside the recess, the top of the recess is covered with a cover plate. Pay attention to the following points during operation:
1. Strictly abide by the safe operating procedures of machine tool workers, and wear labor protection equipment as required.
2. Before starting, you must carefully check whether the motor, switch, circuit and grounding are normal and firm, and check that the control parts and buttons of the equipment are stuck in the correct position.
3. Check the coincidence and firmness of the upper and lower molds; check whether each positioning device meets the requirements of being processed.
4. When the upper slide plate and each positioning axis are not at the origin, run the return-to-origin program.
5. After the equipment is started, run dry for 1-2 minutes, and move on the slide full stroke 2-3 times. If there is any abnormal sound or malfunction, stop it immediately, remove the malfunction, and stop working until it is normal.
6. When working, there should be one person–command, so that the operators and the feeding and suppressing personnel cooperate closely to ensure that the cooperating personnel is in a safe position before issuing the bending signal.
7. When the sheet is bent, it must be compacted to prevent the sheet from lifting and hurting people during the bending.
8. The power supply must be cut off when adjusting the sheet metal press mold, and proceed after stopping the operation.
9. When changing the opening of the variable lower mold, do not allow any material to contact the lower mold.
10. When the machine tool is working, no one is allowed to stand behind the machine tool.
11. It is strictly forbidden to fold the sheet at one end alone.
12. If the workpiece or mold is found to be incorrect during operation, stop and correct it. It is strictly forbidden to correct it by hand to prevent hand injury.
13. It is forbidden to fold over-thick iron plates or quenched steel plates, high-grade alloy steels, square steels, and sheets that exceed the performance of the sheet metal bending machine to avoid damage to the machine tool.
14. Frequently check the overlap of the upper and lower molds; whether the instructions of the pressure gauge meet the regulations.
15. Immediately stop the machine if an abnormality occurs, check the cause, and eliminate it in time.
16. Before shutting down, place wooden blocks on the lower molds under the cylinders on both sides to lower the upper slide plate onto the wooden blocks.
17. Exit the control system program first, then cut off the power supply.
The Right Tool for the Job
The time-honored adage that your dad taught you about selecting “the right tool for the job” doesn’t just apply to your toolbox. Any tool that contacts a workpiece—whether it be a hammer, a drill bit, or a shear blade—should be chosen wisely. For all the massive tonnage that a press brake brings to bear in your fabrication projects, your machine is only as good as the press brake tooling you attach to it.
Selection of the wrong punch or die for a press brake doesn’t just run the risk of causing a poor bend, it can lead to the very real danger of cracked—or exploding—tooling. For the sake of the job and the personnel alike, always choose the right press brake tooling for both your shop and the job at hand.
Basic Principles of Tooling Selection
The basic rules of press brake tooling selection are simple:
- Buy a variety of high-quality punches and dies to stock your shop with.
- Use the correct type of punch and die for the bending job you are working on.
- Recognize that the above two principles are just that—principles. Keep them in mind as you now set yourself to the task of really learning about press brake tooling and applying what you learn to doing both properly.
It behooves a press brake owner or operator to take a course and buy a book or two about press brake tooling to really get a grasp on the subject. Buying the first piece of tooling you see, especially if you can get it for a “good price,” may wind up costing you quite a bit in the end. When you buy tires for your vehicle you likely do some research. The same applies to purchasing tooling for your brake (or other metalworking machines).
Knowing enough to buy the best tires usually ends there—maybe with buying snow tires you trade out twice a year—but press brake tooling gets changed to different configurations very frequently. It’s like buying a set of tires for each road condition: hot pavement, cold cement, gravel, mud, rain, slush, powder snow, ice, hail, and so on.
The best brand of tooling in the world won’t do you much good if you select the wrong punch or die for a job, so get to know each type and learn what they are used for and when.
Choosing Press Brake Tooling for a Shop
Some guidelines that may help start the process of buying good tooling for a shop:
- Purchase ground and hardened high precision tooling manufactured to tolerances within the 0.0004-inch range. European Style tooling are precision-ground to a tolerance near ±0.0005″ and are extremely hardened. New Standard Style tooling is also precision-ground for accuracy.
- All tooling should be of the same height to eliminate the need for constant adjustments of the machine and its support devices between projects. It will also allow new tooling to match the old pieces.
- Buy tooling in segmented sections of different lengths. Not only are they easy to handle, but like a child’s building blocks they allow you to arrange the pieces in a row to create tooling of whatever length you need for the job.
- Learn about specialized punches and dies and know when it’s best to buy them for use with more complicated jobs.
- Be willing to invest in a new clamping system and matching tooling, if needed. The traditional American Style tooling has a smaller area for clamping. European Style has a larger surface area for clamping, making it more secure and accurate. Wila’s New Standard Style tooling has an auto-clamping system for fast tool changeovers and very accurate tool seating. Front-loading, self-seating punches are ideal for ease, accuracy, and safety.
Selecting Press Brake Tooling for a Specific Job
Some recommended tips for helping pick out the best punch and die for a job:
- Understand the differences between air bending, bottom bending, and coining, and know when to use each. Air bending—which involves leaving an air gap between the material and the bottom of the V die—is the standard process, but there will be cases where the material needs to touch the bottom of the die, either lightly (bottom bending) or heavily (coining).
- Make the air bending tonnage chart your best friend. If your brake doesn’t come with a chart mounted to it, find one on the web to print out and tape on your machine. Knowing just the material thickness and the desired inside bend radius, you will be able to calculate from the chart the necessary V die opening, the minimum bendable flange length, and the tonnage per foot of material to make the bend.
- Apply the Rule of Eight. If you don’t know what the inside bend radius will be, a guideline is to select a V opening that is six to ten times the thickness of the material to be bent, so about eight times on average (which is the formula used on most bending charts). When a match can’t be found, round up to the next closest die and you’ll be close to what you need and can experiment from there.
- Don’t try to pick out a punch until you’ve determined a die that has the proper V opening for the job.
- Pay attention to the maximum tonnage capacity of the die in question. For short flanges, the correct V opening might require more tonnage than a specific die can handle.
- Select a punch with a tip that has a radius that’s about half of the thickness of the material if you are bending mild steel or stainless. For soft aluminum, the radius of the tip may have to be identical to the inside radius of the bend.
- Know how to compensate for spring back in the material being bent. For example, because of the greater tensile strength of stainless steel, overbending by one or two degrees is usually necessary to allow for spring back to return the material to the desired angle. For a 90° bend, using an 88° punch is usually recommended for bending stainless.
- Learn the different styles of punches and what they are used for, such as acute punches, which are used for bending very small angles, and gooseneck punches with their large, concave shape, which are used in making channels and U-profiles where a flange would otherwise impact the side of a standard punch.
Specific Case Analysis of Selecting Press Brake Dies
Case 1 Tooling selection for processing stainless steel plates
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 1000 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 die 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.
Case 2 Tooling selection for processing aluminum alloy plate
Automative equipment factory needs to process 6061-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.
Tooling Materials and Quality
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.
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.
Proper Maintenance and Storage
The toolings of the press brake need correct maintenance to extend its service life and ensure bending quality. Regular lubrication, grinding, and monitoring of tooling performance are required according to the instructions for use.
Store toolings in specialized areas, such as tool cabinets with drawers or compartments. Fix and isolate each punch and dies with foam or plastic. Also, clean the toolings regularly, wipe them with a soft cloth, and use an anti-rust spray regularly.
Conclusion
The press brake tools affect the shape and quality of the bending workpiece. Before bending, it is necessary to select the toolings suitable for the material according to the metal sheet.
It is also necessary to determine the shape, angle and opening size of the die according to the bending workpiece. Correct tooling selection and material use can improve the accuracy of bending workpieces.
They will affect the bending angle, internal radius, minimum flange length, and the appearance of the whole workpiece. Using the correct tooling can improve bending efficiency, reduce cost, prevent profile deformation, and protect the safety of press brake operators.
If you are still doubts about the choice of press brake and press brake tooling, you are welcome to get in touch with my company, Krrass Machine Tool.
As a 20-year-experienced press brake manufacturer, we not only offer high-quality press brakes but are also dedicated to offering an overall bending processing solution plan.
I sincerely invite you to visit our product page and learn more about our press brake series and matching toolings. And our team is ready for technology consultant and support.
