PressBrakeTool (1)

of 4
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Document Description
Tooling Technology Press-Brake Tool Selection Start from the bottom and work your way up— spec the V opening, find a compatible punch, then fine-tune to avoid marking and cracking, and optimize throughput. BY KEVIN COYLE hen trying to solve a challenging metal-fabrication problem, it’s good advice to start at the beginning to find a solution. But when it comes to selecting press-brake tooling, the beginning isn’t always easy to find. A rule of thumb: Start from the bottom and work your way to
Document Share
Document Tags
Document Transcript
  W hen trying to solve a chal-lenging metal-fabricationproblem,it’s good advice tostart at the beginning to find asolution.But when it comes toselecting press-brake tooling,thebeginning isn’t always easy to find.A rule ofthumb:Start from thebottom and work your way tothe top.To select press-brake tooling for abending application,start with the prop-er bottom-die opening,and then spec thetop punch.For air-bending operations,several parameters must be consideredwhen specifying the V opening.Theseinclude base-material thickness,flangelength ofthe part and the desired insidebend radius.When consideringmaterial thickness,the V open-ing should be six to 10 times the materialthickness—the multiplying factor dependson the actual thickness ofthe material.When a specific inside radius is required,use a bending-force chart (next page) todetermine the optimum V openings forthe application.Bending-force charts, ToolingTechnology Tool SelectionPress-Brake Start from the bottom andwork your way up—spec the V opening,find a compatible punch,then fine-tuneto avoid markingand cracking, andoptimize throughput. BY KEVIN COYLE Tooling that mounts on a press brakewithout the use of wrenches or othertools will minimize setup time. Thesequick-change tools use a punch- anddie-mounting system that eliminatesthe need for tool centering before eachproduction run, eliminating a time-consuming setup step. Kevin Coyle is tooling product manager, Amada America,Inc.,Buena Park,CA;714/739-2111. 136 METALFORMING / MARCH 2004 METALFORMING / MARCH 2004 137  ToolingTechnology The high tonnages involved in formingsheetmetal can leave impressions fromthe tooling on the material (top). Reduceor eliminate this marking (bottom) byusing a bottom die with increased shoulderradii, or laying a polyurethanesheet or sim-ilarprotectivematerial over the bottom die. Die mark published by press-brake machine andtooling manufacturers,provide data suchas inside radius produced,required ton-nage,smallest bendable flange and theV opening ofthe die. Charting Flange Lengthand Bend Radius When forming a part with a rela-tively short flange length,a bending-force chart assists in determining theV opening.This chart lists the smallestflange each V opening can form.By comparing this to the required flangelength,a proper V opening can be deter-mined.Ifthe flange is extremely short,the necessary V opening may cause therequired tonnage to exceed the capaci-ty ofthe tool selected.You must notoverlook the maximum allowable ton-nage ofthe die selected,to avoid anunsafe situation at the press brake.Ifthe part being formed requires aspecific inside bend radius,the bending-force chart can provide the V opening aswell.For air bending,the inside radiustypically equals the material thickness.By locating the desired radius on thechart,a corresponding V opening can beidentified that will produce that insideradius.Again,verify that the requiredtonnage,for the V opening selected andthe material thickness being formed,does not exceed the allowable tonnageofthe tool being used,and that the pressbrake can produce the tonnage neces-sary to form the desired part length. Time to Select a Punch With the V opening specified based onthe desired part parameters,the engineerthen can select a compatible punch,starting with specifying punch-tip radius. Press-Brake Tool Selection Most European-style punches comewith a variety oftip radii.To form mildand stainless steels,select a punch-tipradius roughly halfthe material thick-ness being formed.Since the V openingwill determine the formed inside bendradius,punch-tip radius should notexceed the material thickness,or else theinside bend radius will increase.When 138 METALFORMING / MARCH 2004  bending soft aluminum,it may be nec-essary to use a punch-tip radius equal tothe desired inside radius,as the materi-al will tend to form to the punch tip.The angle ofthe punch tip also willaffect formed-part dimensions.MostEuropean-style punches come with88- and 90-deg.punch-tip angles.The88-deg.punch tip can be used to over-come springback,which most com-monly occurs when forming in stainlesssteel.Generally,forming stainless steelto 90 deg.,the bend will spring open 1or 2 deg.because ofthe material’s hard-ness.Overbending 1 to 2 deg.will over-come this springback and allow the partto spring open to the desired 90 deg.This flexibility in the punch-tip angleallows for lower-tonnage air bendingwhile producing the desired bend design. Eliminate Cracking andUnsightly Die Marks Common tooling-related defectsrelated to press-brake forming includeselected,the style ofthe tooling canhelp increase overall production.Lookfor press-brake tooling that can bemounted on the press brake without theuse ofwrenches or other tools,to min-imize setup time.These quick-changetools allow an operator to change thepress brake over for the next job quick-ly,preserving time for part production.Such tools use a punch- and die-mount-ing system that eliminates the need fortool centering before each productionrun.The mounting system maintains aconsistent tooling centerline,eliminat-ing a time-consuming setup step.Production also can be improvedwith the use ofspecialty toolingdesigned to form complicated bendswith fewer hits.This type oftoolingfinds use with relatively large produc-tion quantities,where a shop can justi-fy the added tooling cost.Commonbends produced with this type oftool-ing include offsets or joggles,hemmedflanges and narrow channels. MF Tooling   Technology die marks on the material,part crackingand inconsistent bend angles.Thesedefects can be eliminated through someaspect oftool selection.Customers often demand parts withno marking.But,due to the high ton-nages involved in forming sheetmetal,impressions from the tooling on thematerial are inevitable.These can be very noticeable when forming aluminum orprepainted materials.One way to reducethis marking:Use a bottom die withincreased shoulder radii.This allows thematerial to roll over the shoulders ofthedie,with less chance for the die to diginto the material and leave a mark.Foradditional protection from die marks,lay a polyurethane sheet or similar pro-tective material over the bottom die,between it and the base material.When base-material cracking occurs,increasing the V opening ofthe die gen-erally eliminates the problem.Ifcrackingpersists,try increasing the punch-tip radius.With the proper V die and punch 140 METALFORMING
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks

We need your sign to support Project to invent "SMART AND CONTROLLABLE REFLECTIVE BALLOONS" to cover the Sun and Save Our Earth.

More details...

Sign Now!

We are very appreciated for your Prompt Action!