PRIMA POWER FAST BEND IN ACTION
Rapid advancements in the technology used to bend metal panels in the fabrication sector sometimes causes a dilemma to those wanting to identify pros and cons between press brake technology and the fully automated panel bender.
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.
In the right application, the panel bender changes all this. The bending process can be fully automated – automatic tool set up, automatic part loading, complete part manipulation, and unloading. It 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.
But bear in mind this is only with some parts. Panel benders can’t handle everything a stand-alone 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. In fact, bending automation has always been more complex. Aside from using punch form tools, blanking deals mainly with just two dimensions. In bending, you have all three dimensions to take into account.
Choosing which bending technology is ideal involves balancing maximum throughput with expected return on investment. The business needs to know the setup times the parts require; the downtime between jobs; the percentage of time operators are handling the parts; the scrap rate, including scrap produced during setup (tryout parts) and rejected pieces produced during the run; and the average daily output of each machine.
Technology basics
Press brakes are common for one reason – they are inexpensive and versatile. But the brake has drawbacks that have given headaches to many a metal manufacturer. Plus, the basic premise of brake bending has remained the same for decades. The brake applies pressure to the blank in three places: the two die shoulders on the bottom and the punch tip on the top.
A panel bender is different. 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; 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 – a lot less complicated than the press brake’s three points of pressure.
Panel bending advantages
Automated panel benders thrive on large work pieces with both positive and negative flanges that are difficult to handle in the press brake. Also, material variation and springback can be less significant on a panel bender because the bending method generally puts less stress on the work piece.
In a panel bender, the angle 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 the various part widths. Many panel bender models change out these upper tools automatically, often within a few seconds.
Panel bending limits
Some may wonder why all the press brakes in the world are not replaced by panel benders. In reality, there are optimum applications for each technology; it just requires an experienced professional to identify which needs require what technology.
Sure, the panel bender is more expensive than the press brake, but a panel bender’s productivity is so much greater in some applications. So it is not just about the price tag. It is really because a panel bender can’t handle everything a press brake can.
Most benders work best with stock thickness up to 11-gauge mild steel, whereas a press brake becomes more suitable beyond this gauge. Also, automated panel benders work with parts that are not so small, generally these need to more than 150mm wide, otherwise a press brake becomes more applicable at smaller 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.
Press brakes are often better at handling production of interior flanges, regardless of their height.
It’s really down to finding the best balance between panel bender and press brake according to the requirements of each individual fabrication shop.
Ideally, an experienced supplier dealing in both technologies can provide objective analysis on what solutions can deliver the most profitable and timely outcomes.