Rapid advancements in the technology used to bend metal panels in the fabrication sector sometimes cause a dilemma while choosing between press brake technology and fully automated panel benders, according to Maxitec .
Sheet metal automation specialist in Australia and New Zealand, Maxitec explains that a multi axis robot can be integrated with the CNC press brake to eliminate operator handling, but this does not officially address the tooling set up from one part to the next.
Panel benders have their advantages as the bending process can be fully automated right from automatic tool set up, automatic part loading and complete part manipulation to unloading. The panel bender produces positive and negative bends quickly and accurately without a requirement for blank flipping.
The part stays flat in the machine table as only the flange is bent. Now, like the blanking machine, the bending machine controls parts quality and, on some jobs, forms in seconds what would take a press brake a few minutes to do.
However, panel benders can only work with some parts and cannot handle everything a standalone or robotised press brake can, but then again it can do many profiles that are either very difficult or impossible to do in a press brake.
Selecting the most appropriate bending technology involves balancing maximum throughput with expected return on investment. The business needs to know the setup times required by the parts, the downtime between jobs, percentage of time operators are handling the parts, the scrap rate including scrap produced during setup and rejected pieces produced during the run as well as the average daily output of each machine.
Press brakes are more common because they are inexpensive and versatile but they also have their drawbacks. Press brakes work by applying pressure to the blank in three places: the two die shoulders on the bottom and the punch tip on the top.
In panel benders, the material is not bent with pressure applied on both sides of the metal. Instead, the sheet is positioned under a hold-down tool and a flange is bent in the positive or negative direction. A bottom blade moves up to bend positively while a top blade moves down to bend negatively.
The upper hold-down tool segments and stationery bottom hold-down tool clamp the blank in place, but they don't directly form the metal. The only forming pressure applied comes from those upper or lower blades. The sheet metal is formed with just one pressure point from the blade on one side of the sheet, which is a lot less complicated than the press brake’s three points of pressure.
Automated panel benders are suitable for working on large work pieces with both positive and negative flanges that are difficult to handle in the press brake. Material variation and springback can be less significant on a panel bender because the bending method generally puts less stress on the work piece.
Also, the angle in a panel bender is determined not by the tooling but by the motion of the top and bottom bending blades. It is the hold-down tool segments that must be changed out to various part widths. Many panel benders change out these upper tools automatically, often within a few seconds.
But panel bending has its limits, which is why press brakes are still in use. There are optimum applications for each technology and it just requires an experienced professional to identify the right one for each application.
While the panel bender is more expensive than the press brake, it is also more productive in some applications. Most panel benders work best with stock thickness up to 11-gauge mild steel while press brakes are more suitable beyond this gauge.
Also, automated panel benders work with parts that are generally a little more than 150mm wide, but a press brake becomes more applicable at greater dimensions.
Panel benders are best at forming flanges about 200mm and less. Measurements above this are normally more suited for flange forming in a press brake. Also, press brakes are often better at handling production of interior flanges, regardless of their height.
Ideally, an experienced supplier dealing in both technologies can provide objective analysis on what solutions can deliver the most profitable and timely outcomes for specific applications in a fabrication shop.