Page 33 - MetalForming May 2011

data into the machine control. 5) Machine setup—Make all of the required manual adjustments
to gauges, jigs, supports, etc.
6) Test bend—Make iterative setup adjustments to obtain the specified angle and flange
dimensional tolerances.
7) Processing—Actual part
production.
8) Inspection—Inspect parts
before and during processing.
9) Data entry—Log the job and mis- cellaneous shop document require-
ments.
Studies performed in the bending
area of many shops, including typical job shops and OEM facilities, have uncovered a poor ratio of value-added activities to nonvalue-added activities (Fig. 1). Nonproductive activities account for 72 percent of the typical press-brake operator’s time, while green-light time making parts com- prises only 28 percent of an operator’s day. With the current trend of high- mix/low-volume processing, where many shops experience more job changes than ever before, green-light time can be even further reduced. New jobs usually require more lengthy setups, since the setup person must start from scratch when determining bend sequence and tool assignments. If this information is not recorded for future repeat runs of the job, this series of events repeats itself. Even if the setup person records the elements of the setup, most times it remains in his pos- session, unavailable for use by others.
With the pool of highly skilled brake operators getting shallow, shops will continue struggling to maintain a good level of accuracy and efficiency in their bending area. Additionally, differences in setup practices among setup per- sonnel lead to inconsistencies in part specifications and quality. These inef- ficient practices all contribute to low green-light times, making press-brake bending a labor-intensive process and a bottleneck for many shops. Most fab- ricators address a bending bottleneck by adding more machines, shifts and operators, or upgrading to faster
machines—none of which improve the ratio of value- to nonvalue-added time.
The Virtual Bending Solution
A better solution exists in the form of software used to program press brakes offline. Press-brake software and con- trols have evolved to help operators crack the complex operation of press brakes in an offline, virtual environ- ment. Sophisticated 3D graphical pro- grams accurately depict the bending environment of machine, tools and part geometry. This allows an operator to virtually bend a part before he wastes time performing this process on the floor. The trial-and-error setup process for new production runs can now take place offline.
These virtual bending programs take electronic part data existing in the shop as 2D data (dxf or iges files) or as 3D models, and create bending programs guaranteed to be successful on the machine. Further, virtual bending solu- tions can be used to determine the manufacturability of a new part, or its tooling requirements, before valuable resources are wasted on jobs deter- mined to have special requirements that a shop may not offer. Then, if a shop discovers that it may need to acquire new tools for a job, it can order the tools confident that they will work.
Many parts come from customers with poorly calculated blank sizes. Since bend deduction can’t truly be determined without knowledge of the tooling used, many flat parts come to the press brake that cannot meet spec when formed. Also, many bending CAM programs allow corrected blanks, based on actual tooling, to be exported
The greatest benefit of bend- ing CAM programs: They externalize a significant per- centage of the setup pie. Bend-sequence planning, tool selection and layout, and press-brake programming are removed from the floor, increasing green-light time.
The 3D simulation generated
by a virtual bending program
displays on the machine’s
control, providing a bend-by-
bend graphical representation of part placement along the machine. This reduces cycle time and minimizes the risk of misformed parts due to incorrect part placement or sequence errors.
back to punching and laser program- ming before processing. This provides the press-brake operator with the cor- rect blanks and reduces the time spent adjusting flange lengths to keep the entire part in spec—or worse, sending out poor-quality parts and hoping for the best.
The greatest benefit of bending CAM programs: They externalize a signifi- cant percentage of the setup pie. Bend- sequence planning, tool selection and layout, and press-brake programming are removed from the floor, increasing green-light time. Yes, this process shifts the burden to the design room, but some CAM programs can batch- process large quantities of parts autonomously to minimize this bur- den. Further, the software can be trained to scan the database for revi- sions to drawings and then automati- cally reprogram parts when necessary. This eliminates the processing of parts based on outdated drawings due to engineering oversight.
Lastly, once a shop has centralized
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