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In 2014, two primary sheet metal and plate bending machines are the press brake and the panel bender. There are other metal bending machines, including folding machines, wing benders, and others, but these two represent some overlapping capabilities that make them appropriate subjects for a comparison. Given a particular class of work, it may be that you could use either one.
Press brakes have been around for more than 100 years, while panel benders, invented by Mr. Guido Salvagnini, have been around only since about 1977. Each of the two types of machines has a solid place in manufacturing technology, each offering unique advantages, but there are large differences in capability and productivity between the two.
This is a comparison of those capabilities. To make a point-by-point comparison, we have to list some facts that you certainly know. Our hope is that seeing the basic facts for both machine types in the same place will provide a head-to-head perspective and be worth your indulgence. We’re drawing from Salvagnini’s data; they make both types of machines, so they have no axe to grind in comparing the two types.
The basic differences
Most people reading this are familiar with press brakes, so the primary thrust of this article will be panel benders, how they compare to press brakes, and why and when you should consider them.
Press brakes, high end or low end, cost significantly less than panel benders. On the other hand, panel benders produce significantly more parts per hour.
Each press brake requires at least one operator. Manual load/unload panel benders also require an operator, while panel benders with automation require a fraction of a person.
Also, a panel bender can use an untrained operator to run the machine, as all the “operator” does is put the panel in and take the finished part out.
Press Brakes can be used to bend thin gauge sheet metal up to very thick plate. They are rated in tonnage and are primarily in the 40 ton to 350 ton range, but are also available in tonnages that range to the thousands of tons.
Press brakes range from simple, all-manual machines, to high end machines that automate limited aspects of operation — automatic tool changing, angle correction, and some other elements. Most press brakes sold today do not include automation.
Based on current data, typical press brakes realistically produce 6-10 parts per worker hour. Some world-class companies can produce more parts per hour by controlling the entire bending process to the highest degree possible. For comparison, manual load/unload panel benders can produce up to 60 parts per worker hour, each part with eight bends.
Panel benders are used to bend gauge-thickness sheet metal and are not usually rated in tonnage, but in thickness of material that can be bent. Depending upon the machine — different machines handle different thicknesses, depths, lengths and bend height — a panel bender can;
* bend parts up to approximately 11 gauge (0.120 in.) in CRS
* have a bend height of up to 10 in.
* have a maximum bend length of 156 in., plus or minus
These specifications are the maximums for different machine models. They can’t all be met on a single machine.
Panel benders, by design, take advantage of CNC’s ability to control operating functions. They began with this advantage over press brakes. Today, they’re available in manual load/unload versions, or with full automation. They also can be employed as part of a production line or cell that can include punches, punch/laser combinations, punch/shear combinations, or laser cutters that can feed the panel bender.
As of 2014, most panel benders that have been installed have some level of automation. Although they’re an excellent fit with automated loading and unloading, manual load/unload panel benders have been growing in popularity over the past four years and may actually pass the numbers of panel benders with automation. Automation is not their only virtue; they’re highly productive with or without it.
A sheet follower adds some degree of automation to a press brake, but not to the degree of a panel bender.
Current technology, brakes
From when brakes and panel benders were introduced, there has been an ongoing quest to:
-Increase total value added time/hour and/or increased the percentage of value added time
-Produce more parts in a given amount of time
-Reduce setups and setup time
-Reduce setup scrap and “make it right the first time”
-Have the machine automatically adjust for the correct bend angle
-Reduce tooling setup time (Automatic tool load and unload)
-Offer robot load/unload for brakes
Virtually every press brake manufacturer has introduced a “high end” brake that incorporates much or all of the following capabilities. There may be more features from some machine builders:
-Decreased cost of operation
-High accuracy ram positioning (Electric brakes, scales, electric over hydraulic hybrids, etc.)
-Automatic crowning (Several technologies that all seem to work pretty well)
-Faster tool changeover (hydraulic/electric tool clamping still requires an operator)
-Automatic tool changer (Several methods, which eliminate operator tool changing)
-Automatic angle check and rebend for correct angle the “first time” (Several methods that all seem to work pretty well)
-Thousands of programs held in the machine CNC
-Continually increasing the number of back gauge axes that are CNC controlled
-CNC controlled front gauge axes
-Ability to maintain accuracy within a wide range of temperatures
Brakes are not the universal panacea but they are powerful performers when used within their capabilities.
In 2014, Salvagnini introduced ATA (Automatic Tool Adjust) ATA is the ability to use a single set of tools, automatically adjusted, to move tool set up time into the realm of “masked time.” This is not a tool changer but it is a technology that came out of Salvagnini’s panel bender technology. While not necessarily a cure all, it can significantly increase value-added time and increase part throughput and velocity.
Again, using technology taken from panel benders, Salvagnini introduced the ability to program part-to-part using a barcode reader, to tell the machine to use a program that already exists in the system CNC.
Salvagnini has also introduced a combination of electric/hydraulic/scale technology to improve ram positioning accuracy to +/- 2 microns (80 microinches).
Salvagnin’s “Kinetic Energy Recovery System” significantly reduces power consumption, increases ram speed, and decreases heat.
A fully automated panel bender: blanks come in from the left and finished parts exit to the right. The work handling deposits finished parts to the front of the right side.
Current technology, panel benders
Panel benders are not machines you can buy just on their specs. It is important to speak with the manufacturer to confirm that a panel bender model and capability fits your specific needs.
The best and most productive panel benders act in a similar way: A blank is put into the panel bender (manual load/unload or automatic) and a finished part exits the machine. Noe that, even with manual load/unload panel benders, the best and most productive ones have the operator locating the blank against stops, pushing the “start” button and then taking out the finished part.
When investigating manual load/unload panel benders, it is important to know how much operator intervention is needed to make a complete part.
Panel benders are inherently “single piece flow” or batch machines and can switch back and forth easily.
Press brakes are inherently batch machines and are hard pressed to achieve “single piece flow.”
The difference means that a panel bender can produce kits of parts, small batches of parts, or can be used as a batch machine. This is done quickly and easily because of the inherent design of the panel bender. So, with the panel bender, you gain more control of your manufacturing process’ you can break into a batch to make one part; and then be back producing the rest of the batch while taking only the time to make that one part.
Panel benders usually locate the part once, based on the centerline of the part, and then bend the entire part.
Press brakes usually locate the part from four sides and, when located, bend each side. A panel bender will bend to tolerances of 0.008 in while a press brake bend-to-bend accuracy is often dependent upon the accuracy of the blank. Therefore, a panel bender has an inherent advantage in producing quality parts.
Panel benders can virtually eliminate set up time. Press brakes, even with all the new technology, take more time to set up.
Manual panel benders can be set up for the next part by scanning a bar code while the machine is bending the previous part. Salvagnini has introduced this capability as part of the model B-3 press brake.
With “best practice” manual panel benders, the operator loads the blank once and unloads a finished part.
With press brakes, the operator/robot must manipulate the part at least four times, significantly increasing part throughput and reducing the opportunity for human error.
The panel bender’s high accuracy allows you to design and manufacture parts that slip together or snap together. Thus, you can design assemblies that can be more easily assembled, that have significantly less (sometimes no) fasteners, and that allow you to ship assemblies to the user that can be assembled at the point of use. This ability is currently not available for most press brakes.
Panel benders take into account ambient temperature, part thickness, and bending pressure, quickly and easily.
Press brakes can achieve much of this but only at the expense of additional production time. A panel bender therefore gives you greater accuracy, but not at the expense of significant amounts of production time. You produce a higher quality part for a lower cost.
Panel benders can, with automation, be incorporated as part of a production line that could include a punch, punch/shear, punch/laser, or laser cutter. One to three operators can operate a line that can produce kits of parts or batches of parts, and give you complete control of your production process.
Press brakes are not friendly to a production line. Unless you use a robot to load/unload, you can assume that it will take at least one operator per press brake, and more operators to run the rest of the line. With a panel bender, you can product parts more quickly, with significantly fewer people, for less cost, with higher accuracy, and when you want.
Panel benders, incorporated into a production line, allow you to take blanks and make them into finished parts, or to produce blanks to a schedule and bend parts to a need. Again, they give you more control over your production process.
Press brakes are primarily batch machines. The upside is that you can make your parts when you want, how you want, and produce “hot” parts as you need them.
In other words, despite their productivity advantages, panel benders are not the universal panacea. They are, however, powerful performers that can take your company to new heights of productivity.
When investigating bending technology that falls within the range of a panel bender, it will be necessary to see if a press brake or a panel bender would be better for your specific application. On the other hand, you might want to investigate a “Flex-Cell” where a press brake and a panel bender are connected via software, as being your best bet.
Parts per hour versus versatility is the first issue. Beyond that, labor time and consistent accuracy come into play. Talk to a machine supplier and your best answers should be clear in no time.
Salvagnini