Dec 01, 2020
An Press brake operator had to know quite a bit before he was ever allowed to run a press brake for bending metal products. He had to know things like what a bend deduction was, what punch tip radius should be used based on different metal material thickness, and what V openings to use for the material they are benidng.
Know Your Press brake Tooling
Small and medium-sized fab shops probably have plenty of press brake tools around because once they are purchased, why would you get rid of them? That becomes a problem, however, when new tooling is purchased. Inexperienced operators probably see the new and old tooling as all being similar. That’s not the case.
Press brake tooling was mostly designed to be used in coining or bottoming applications where the final form was a direct representation of the die it was being pushed into. These tools have their place for low-tolerance bends or bottom-bending applications. They also are looked upon as being an affordable, entry-level press brake tooling investment.
Because planed tooling is manufactured in long lengths and then cut to size, segments cut from the original blank are subject to substantial changes from one to the other if they are not used in the order that they were cut. If the tools are mismatched in the press brake, the operator can see as much as a 0.3mm difference between two tools. It should be noted that an experienced press brake operator can produce high-tolerance parts with this type of tooling, but in the hands of a less experienced person, a shop can’t expect the same results.
That’s why it makes sense for any company that has purchased a new press brake to consider precision-ground tooling. These tools start as tool steel blanks that are ground using precision machinery to get close to +/-0.01mm in profile accuracy. They also have consistent heights, usually 130 or 150 mm tall, and hold a consistent centerline during bending.
With this type of arrangement, a press brake operator can do a staged bending sequence because of the consistent shut height of the tools. He can have a gooseneck punch for return bends on the piece and then right next to it an acute and flattening tool setup to do heming bending. The operator doesn’t have to shim or adjust anything for the multiple operations to take place.
It is also important to select top bending punch angles that are equal to or less than the included angle of the die. For example, if the operator selects an 88-degree punch and tries to use a 60-degree die, the dissimilar tools will directly interact and could cause the die to split or worse. At the very least, the damaged tooling will lead to poor-quality bending parts.
Any sort of obvious press brake tools damage, such as a crack, needs to be discovered before the press brake tooling is loaded into the press brake.
Not so obvious things to look for include a crushed radius or a dimple on the punch tip. This can affect the accuracy of the punch. (In this instance, a shop doesn’t have to throw away the entire tool. The end can be cut off using a wire EDM, for example. Usually this should be done by the tooling manufacturer or an experienced toolmaker.)
If the operator is working with gooseneck tooling, he should check to see if it is starting to pull away from its centerline. If the tooling has been used in press brake applications with too much tonnage, the tooling will start to curl into itself. The damaged tooling leads to inaccurate bending.
Examining tooling is not limited to punches. All Pressbrake Dies also should be examined. Die shoulders that exhibit dimples or have more of a convex shape are warning signs. This damage affects the ability to consistently deliver accurate bends. An inexperienced press brake operator might be tempted to apply more tonnage during the bend to make up for the inconsistency, but this only exacerbates the situation, perhaps leading to the tool cracking or worse.
Any damaged tooling, if not thrown away or sent out for repair, should be clearly marked so that others know not to use it. That prevents wasted time and effort at the press brake as the operator tries to achieve consistent and accurate bends and keeps the press brake operators safe.
Here’s one more note: If an operator is handling the tools during inspection, they probably should be wearing gloves. The oils on hands can eventually lead to rusting on the tooling if the tools aren’t cleaned regularly.