Bending Made Easy: Advancing the CNC Press Brake Control

An increased use of lasers that can cut almost any type of material, along with increasingly complex parts that require greater accuracy, demand a user-friendly interface that makes bending complex parts easy, as well as a powerful CNC controller to assist the operator in calculating the blank size and bending sequence.

In addition to simplifying the bending process, advanced press brake controls help minimize machine setup. Set-up time continues to increase because of reduced lot sizes and newer manufacturing methods that minimize levels of raw material inventory and work-in-process. Setup time also impacts the flow of components for downstream operations such as welding, painting and assembly.

Today's controls develop the part program with limited operator input, as well as complete and automatic positioning of ram, bed crowning and backgauge axis for each bend, thus reducing setup time. On-line text files that travel with the program aid in directing the operator for tooling set-up, initial part positioning, and other specific instructions.

Even the simplest of tasks are enhanced. For instance, "tool filters" are used to remove from the menu the forming tools that cannot be used for the current part. The operator or programmer can only choose from a "pre-selected" list of tools for that thickness of material.

The current market demand is for shorter lead times and fewer quantities. Processes that were "hard-tooled" are no longer practical. Radius forming, for example, generally was done with a matched radius tools. The cost of the tool and the additional setup time was amortized over the entire batch.

Today, fabricators use flexible means such as "step or bump forming" to achieve the required radius. The programmer simply enters the angle, radius and resolution and the control calculates the angles and lengths of each form. Standard tooling is used, which can save thousands of dollars and weeks of lead-time.

As more complex parts are processed, machine setups become more complex too. It is not unusual to have three or four different sets of tooling in one machine at the same time. The locations of the tools down the length of the bed and ram is critical. Ram tilt, bed crowning and part interference man date exact locations. Some machine controllers have graphical display along with dimensions to aid the machine operator in correct tool placement. Advanced systems even have the means to project laser lines as a pointer to show the operator where the tools are positioned down the length of the ram and bed.

Because of machine and tooling deflection coupled with part thickness and hardness variations, it is typical for the machine operator to be required to apply corrections to the process. In the past, the operator would measure the part errors and manually assess and apply offsets. Most modern press brake rams are tilted in ten thousands of an inch increment. Some systems may use a percentage value to drive the bed crowning device. Because of the advanced mathematics required to convert angular errors to inches and even to percents, the operator would simply make an educated guess and make a tryout part.

Today's press brakes feature powerful controllers that will make these corrections. Some can even assess the corrections based on the location of the part down the length of the machine. The operator simply enters the angles of the part at the left, center and right. The controller recalculates a new tilting, crowning, spring back correction and automatically applies them to the program. Some advanced systems have automatic angle measuring devices, which completely automate this process.

Artificial intelligence coupled with a database is one method to produce an exact 3D-unfolded blank.

Some controls are able to create and store interactive databases for bend allowance. The user-generated data, created by actual bending results, are searched and applied each time a new part program is generated. This automatic optimization of the part program eliminates trial bending, and reduces the time required to produce a quality part.

The database resident in the control serves the same function as an experienced operator. Without this powerful feature, machine operators would need to learn the errors and imperfections in bending metal and would compensate for them. Today, these powerful databases identify errors and apply them to a new program, serving as an artificial intelligence built into the machine.

A broader array of features further simplifies the bending process. For instance, improvements in import utilities allow users to easily import 3D CAD drawings. Once imported, the software applies the technology from the resident database to automatically apply or calculate factors such as tools to be used, length of tools, etc. The information is calculated by the model and the technology is then applied to every bend automatically.

Ten years ago, most systems could only provide a bend solution which would tell the user which bend to perform first. Advanced systems provide not only the bend solution ? which bend to perform first ? they apply all the technology to all the bends so the user knows what bend to make first, what tools to use, what offsets to use, and all other machine features are also known when the model is imported.

By contrast, today's systems also provide for the bending of less complex parts. A quick bend feature permits quick production of simple or infrequently produced parts at the press brake. This feature simplifies the programming process by requiring a limited input of data.

In this operating mode, the operator follows the control's prompts to input material type, thickness, length, tooling requirements and number of bend sequences. The system determines the optimal angle and the position of the back gauge for each bend. Minimum and maximum values for the bend angle and the back gauge position are provided. All other items of the program are automatically calculated or obtained from the database files.

When input of part data is completed, the operator simply presses the function key to start the production mode using the created program. A sequential program name is applied for storage and future retrieval. The quick bend mode circumvents high powered programming features to speed programming of particularly simple parts, such as an angle bracket with a 90 deg bend.

Closer integration of the control and offline programming system by press brake manufacturers has enabled more flexibility and greater capability in the bending process.

A critical factor in simplifying press brake operations is the ability of the machine control and part programming system to integrate the special functions needed to improve the bending process. As the machine control has become easier to use, software to power the control has become more capable and now includes more automated features designed to address the trend of simplification.

Continual advancements in computer, operating system and networking technologies make sharing of database expertise more and more common, especially to networkable PC-based CNC machines. Advancements in computer technology are making it possible to network very powerful programming and database computers to fabricating machines without great expense. Also, modern, user-friendly operating systems make it much easier for programmers and operators to leverage this information and expertise to produce better parts, faster.

The effort to simplify the man-machine interface has yielded machine controls with graphically-based input screens introduced in the mid-1980s, quickly followed by the advent of PC-based controls. The most recent control advancement is the touch screen format. Touch screen controls use the latest in infrared touch screen technology coupled with a PC based control unit, thus combining the power of the CNC control with the speed and simplicity of touch screen programming.

The touch screen control offers an easy to use, intuitive interface to minimize input to the control, allowing the user to move from drawing to completed part in fewer steps. IR touch screen technology is a robust industrial design that can withstand the shop environment yet newer touch screen controls are so responsive they can be operated while wearing work gloves.

Unlike early touch screen controllers, the latest touch screen control is truly designed for the touch format which means control and software are written specifically for touch. New touch screen control hardware is more compact, less expensive and even more powerful than that of a few years ago.

Paul LeTang is a senior applications engineer for forming at LVD Strippit, Inc., 12975 Clarence Center Road, Akron, NY 14001-9902, 716-542-4511, Fax: 716-542-5232; www.lvdgroup.com; info@strippit.com.