On the first day of using the new press brake, the operator plunged into a battle that would persist throughout the machine’s many years of operation. Unfortunately, many were unaware that they had committed to this struggle and would find themselves ill-prepared for it.
This relentless battle revolves around part collisions—formed parts nearly colliding with every surface on the machine, including the punch (upper beam), bed (lower beam), tools, and possibly even the back gauge.
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Some of the most common part collisions occur when bending deep U-shaped parts or parts with long return flanges, ultimately colliding with the punch. The most prevalent collision types occur when parts collide with the punch. This typically happens with parts featuring long return flanges or complex bending sequences or parts like door frames with return flanges protruding to the front and rear of the punch (see Figure 2). Figure 3 depicts another typical example: a collision between a deep box and the clamping system.
If you’ve spent a significant amount of time operating a press brake, you may have experienced all these collisions and countless others. Fortunately, you can follow some strategies to maximize bending freedom while minimizing collisions that could damage parts, especially the press brake itself.
Pay Attention to the Open Height
When purchasing a new press brake, always get a machine with as much open height as possible between the bottom of the ram and the top of the bed. The size of this work envelope will determine how much you can put into it, and it typically can’t be changed.
Use the Tallest Tools Possible
The open height of 20 inches (508 mm) for a press brake has become commonplace, and many press brake manufacturers also offer machines with open heights of 25.590 inches (650 mm) or even higher. These machines allow the use of extremely tall punches, dies, punch extensions, and die entry radii combinations, providing significant versatility when bending deep U-shaped parts, four-sided parts, and thick plates.
Always invest in the tallest tool combination allowed by the machine’s open height. The taller the punch or die, the more versatile its applications. There is nothing worse than purchasing a short tool, only to discover months or even years later that it cannot form the parts you need to produce. In such cases, you may need to purchase a taller version of the same tool, wasting money spent on the shorter tool.
Consider Using A Thinner Die Seat
If your press brake has limited open height, you may encounter difficulties forming certain parts because the required tools are too tall. If your machine has a manual die seat, consider replacing it with a thinner die seat to gain additional open height.
If the machine features a manual crowning system, you can also temporarily substitute it with a thinner die holder. Unfortunately, when doing so, you will lose the ability to compensate for the natural deflection that occurs in the press brake during the bending process. This may necessitate manually shimming the dies for precise bending.
By Brake Press Figure 1. Collision between a deep U-shaped part and the punch.
Any experienced press brake operator knows that shimming dies is a time-consuming process and requires a skill that is challenging to teach. Therefore, this option can only be used as a temporary solution to help you complete a job and then reload the crowning system for the next task.
Provide Ample Workspace
Ensure there is ample working space between the punches and the dies to facilitate easy part manipulation throughout the bending sequence and effortless part removal upon completion.
Whenever feasible, maintain a minimum of 4 inches (101 mm) of working space between the punch and die when bending small to mid-sized parts composed of light-gauge materials, and increase to 6 inches (152 mm) or more when bending boxes and four-sided parts. Naturally, parts with intricate bend sequences and those crafted from thick plates may necessitate even greater clearance.
Ensure Sufficient Stroke Length
Stroke length should be equal to at least 50% of the machine’s open-height specification. Of course, the clamping system, punches, dies, and crowning system or die holder (whichever applies) will consume a large percentage of the open height when installed.
When bending materials between 22 and 10 ga., have enough stroke length for the punch to reach the top of the die holder when all of the components except the dies are installed. This ensures sufficient stroke length to reach the bottom of the V opening on any die. It’s also good practice not to run the drive components out to the end of the stroke.
Note that this rule isn’t practical when bending thick plate over large V-die openings. But again, when working with material between 22 and 10 ga., it can be a good practice to follow.
Consider A Punch Extension for Piercing
If you are bending four-sided parts like boxes and pans, be very careful when selecting the punch. You want to prevent the sides of the parts from sweeping up toward the ram or the clamping system when you bend the third and fourth side.
Because of the extreme tooling height requirements to form these parts, you might find you don’t have a punch tall enough to bend them. In these cases, you might need a special, extremely tall punch made specifically for the job. Another, usually less expensive, option is to use a punch extender combined with a standard punch. Punch extenders can have more value as well, since they can be used to form other parts in the future.
To determine the required height of the punch (or punch and punch extender combination) to bend a four-sided part, multiply the depth of the part by 1.7. Note that this rule does not apply to press brakes equipped with a heavy-duty clamping system. Measured from front to back, such systems are much wider than standard clamping systems and, therefore, create a much wider interference zone. If you have a heavy-duty clamping system and foresee a potential collision, contact your press brake tooling supplier to find out what solutions are available.
Consider Taller Dies and Die Risers
Before initiating the bending process, always take into account the positioning of the bends on your parts. Consider whether they include tabs or offset bends located far into the sheet from the edges, resulting in an extended down-flange. In such cases, it is essential to use a tall die to prevent the down-flange from colliding with the die holder or the bed of the machine.
Most press brake tooling manufacturers offer taller dies, die risers, or standard die holders that allow you to elevate the height of your dies further above the machine’s bed. However, before purchasing these items, ensure that the backgauge on your press brake can be adjusted to accommodate the higher position of the top of the die.
Simulate Your Bends
If you program your parts offline before sending the job to the press brake, you have a very powerful tool at your disposal. Bend simulations expose parts that will cause collisions and offer alternatives before you experience collisions at the press brake.
Of course, you may be able to perform the same simulations on your press brake’s controller. Doing so, though, will tie up the machine when it could be bending parts.
Access Tooling Data Digitally
One contributing factor to part collisions is the historical focus of press brake tooling manufacturers on critical dimensions affecting bending accuracy. These dimensions encompass working height, tip radii, and tip angle for punches, as well as working height, V-opening width, V-opening angle, and V-opening shoulder radii for dies. Certain tool areas, especially those not engaging the material during bending, were, and in some cases still are, machined with more open tolerances.
While additional machining incurs costs, end users have traditionally managed minor angle corrections by hand when light-gauge parts experience slight collisions with tooling. However, driven by the growing demand for higher-quality parts and increased productivity, many tooling manufacturers have tightened tolerances in these non-engaging areas to eliminate discrepancies between different tools.
Recently, smart tooling has emerged as a new technology, featuring a DM code on each tool and its container. This enables scanning of individual tools or all tools simultaneously using a mobile phone. Upon scanning, immediate access to the precise digital twin and complete specifications of each tool becomes available.
Data files can be uploaded to the cloud and then to the press brake control. Toolholders equipped with a Bluetooth module can also directly transfer data from tools to the press brake control. This technology enhances bending simulation by basing all collision avoidance calculations on accurate tool data, eliminating assumptions. Moreover, it offers diverse applications for tooling inventory control and management.
Smart tooling presents a crucial component in the collision-avoidance puzzle. When combined with bend simulation, appropriate tooling, and accessories, it has the potential to put an end to struggles with part collisions.
By implementing these strategies, you can significantly reduce the risk of part collisions and enhance the efficiency of your press brake operations.
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