Tool School - Rotary Draw Bending Tooling An Engineer s Guide to Bending Tubes
Tube Form Solutions Tool School Rotary Draw Bending Tooling
Tool School Agenda: Introduction To Rotary Draw Bending Engineering Guidelines Tight Radius Bending Completing the Application Review Special Considerations & Applications Summary and Benefits
Introduction To Rotary Draw Bending
Introduction To Rotary Draw Bending Machine Axes
Introduction To Rotary Draw Bending Typical Interlock Style Tooling Wiper Die Bend Die Interlock Mandrel Clamp Die Pressure Die
Introduction To Rotary Draw Bending Interlock (Spool) Bend Die The Bend Die is used to form the tube and determines the radius of the bend
Introduction To Rotary Draw Bending Standard Bend Die Configurations Non-Interlock Interlock Non-Interlock Interlock Non-Interlock Interlock Non-Interlock Wiper Die Notch Interlock Wiper Die Notch Non-Interlock Wiper Die Notch Interlock Wiper Die Notch
Introduction To Rotary Draw Bending Pedestal & Flange Mount Bend Dies Pedestal & Flange Mount Bend Dies are required: 1. When Height Is Larger Than Width 2. For Small CLR (not enough material left for a post through hole) Features of Pedestal & Flange Mount: May or May Not Incorporate A Tool Post Incorporates Platform For Stability
Introduction To Rotary Draw Bending Clamp Die The Clamp Die is used to grip the tube against the Bend Die as the Bend Die rotates
Introduction To Rotary Draw Bending Pressure Die Assembly The Pressure Die presses the tube into the Bend Die and applies the pressure required to bend the tube
Introduction To Rotary Draw Bending Standard Pitch 4-ball Mandrel The Mandrel supports the inside of the tube to prevent collapse and wrinkling during bending. Steel / Chrome Mandrels Are Used For bending: Steel, Copper, Aluminum, Bronze Tubing Aluminum Bronze Mandrels Are Used For bending: Stainless, Titanium, Inconel Tubing
Introduction To Rotary Draw Bending Close Pitch 5 Ball Mandrel Close pitch mandrels are designed with less gap between the balls Used for thin wall tubing and tight radius bends Utilize smaller link sizes
Introduction To Rotary Draw Bending Typical Square Back Wiper Die The wiper die supports the tube on the inside of the bend to prevent wrinkles Steel Wiper Dies Are Used For: Steel, Copper, Aluminum, Bronze Tubing Aluminum Bronze Wiper Dies Are Used For: Stainless, Titanium, Inconel Tubing
Introduction To Rotary Draw Bending Typical Wiper Die Tip with Close Approach Holder
Engineering Guidelines Requirements for Tool Design
Engineering Guidelines Requirements for Tool Design Material type Bend Criteria Tube O.D. Wall thickness Bend radius Max. Bend Angle
Engineering Guidelines Bend Criteria The Bend Criteria required will determine the type of tools needed. Bend Criteria is referred to as: Ovality Wall Thinning Deformation Marking Other Customer Specifications
Engineering Guidelines Formulas Wall Factor (WF) D of Bend (D) Difficulty Factor (DF) Tube OD WF Wall CLR Radius D Tube OD DF WF D
Engineering Guidelines Mandrel And Wiper Die Selection Guide
Engineering Guidelines Clamp Length Calculations D.F. 18 or less = 2 x TOD D.F 19-28 = 2.5 x TOD D.F. 29-56 = 3.0 x TOD D.F. 57-70 = 3.5 x TOD D.F. 71 -?? = 4.0 and/or plug Length
Engineering Guidelines Difficulty Calculation Examples 2.00 OD,.065 Wall, 4.0 CLR, Stainless 2.00 OD /.065 Wall = 30.7 Wall Factor 4.00 CLR / 2.00 OD = 2.0 D Factor 30.7 WF / 2 D = 15.3 Difficulty Factor Per Guide; Requires 2 Ball Mandrel a Wiper Die and 4.00 Long Grip (2D) Aluminum Bronze Mandrel & Wiper Die
Engineering Guidelines Difficulty Calculation Example 2.00 OD,.028 Wall, 3.00 CLR, Alum. 2.00 OD /.028 Wall = 71.4 Wall Factor 3.00 CLR / 2.00 OD = 1.5 D Factor 71.4 W.F. / 1.5 D = 47.6 Difficulty Factor Per Guide; Requires 5 Ball Mandrel a Wiper Die and 6.00 Long Grip (3D) Chrome Mandrel & Steel Wiper Die
Part Shape Distance Between Bends Is Shorter Than Engineering Clamp Length Guidelines Engineering Guidelines Real World Situation
Engineering Guidelines Clamp Gripping Alternatives Surfalloy ( 6 grades available) Carbide Spray ( 6 grades available) Serrations ( Several options) Other All Grip Applications Cause Marking
Tight Radius Bending
Tight Radius Bending Material Considerations Material type Stainless, Titanium, Aluminum, Etc. Material Elongation The plastic limit that the material can stretch Elongation percentage requirement formula for conventional machine Elongation % = 0.50 X OD X 100 CLR
Tight Radius Bending Material Considerations Single Bend Vs Multi bends Single Bend allows the outside wall to be drawn into bend with out breaking (sample) Degree of Bend Required Larger bend angles require more mandrel balls (To support the clamp) Tooling clearance is an issue (Wiper Die) (Notch Bend die)
Tight Radius Bending Material Considerations Ovality Requirements Ovality % = Max OD - Min OD X 100 Nominal OD 5 Percent Ovality
Tight Radius Bending Material Considerations Wall Thinning Requirements WT % = (Nom. - Min) / Nom X 100 Thin Wall Area
Tight Radius Bending Material Considerations Tensile Strength Breaking point Yield Strength Point of permanent deformation Difficulty Factor
Tight Radius Bending Machine Considerations Sized for the bending torque required Boost (Also called pressure die assist) Clamp die Support Holder should support total length
Tight Radius Bending Machine Considerations Heated Tooling Option Required when bending pure titanium with tighter than 3 D Bends Typically the Pressure Die and mandrel are heated to increase the material elongation
Tight Radius Bending Machine Considerations Carriage Boost Less draw force needed Elongation Forces additional material into bend reducing wall thinning and possibility of tube breakage Compression
Tight Radius Bending Machine Considerations Carriage Boost Carriage Boost Assembly Carriage boost applies force to end of tube Carriage boost, and pressure die assist movement is synchronized with C-axis position
Tight Radius Bending Machine Considerations Carriage Boost Reduces clamp force requirement Allows tighter radius bends Required with materials with low elongation value and bends of 1.5 D or less Position Control Vs Pressure Control Position control electronically synchronizes the pressure die assist and/or the carriage boost to the bend arm position Push to Tangent Reduces material required (OD Collet Required)
Tight Radius Bending Hydraulic Pressures Keep Pressure die Pressure to min. Boost (Pressure die Assist) 75% Of Pressure die starting point Boost Back Pressure (non mdl) Increases amount of stretch Mechanical Pressure die setup Vs. Hydraulic Pressure setup Should use hydraulic pressure method
Tight Radius Bending Tooling Considerations Tool Tolerances Must be Close Need Adequate Clamp Length Interlocking Tooling Deflections must be minimized: Bend die, Bend Post, Wiper die, Wiper Holder, Wiper Die Post, Tie Bars, and Clamp dies are major contributors to reducing deflections. Think Rigidity Definition: a. firmly fixed or set b. inflexible
Tight Radius Bending Tooling Considerations Mandrel fit Establishes Ovality and controls wrinkling Static Pressure dies (non-mandrel) Allow stretch of outer wall Serrations or Other Gripping Application Added to Pressure Die Provides more frictional coupling
Tight Radius Bending Tooling Considerations Refer to the Basics in Tool Set Up Bend die must be torqued. (Refer to machine recommendation s) Clamp die should not touch the bend die Monitor clamp die for slippage Pressure die should not touch the bend die Pressure die should travel at the same speed as the bend die
Tight Radius Bending Tooling Considerations The mandrel shank end should be adjusted to tangent point Too many mandrel balls may cause excessive drag Monitor mandrel lubrication Depending on material, too much lubrication or too little, or none may be what makes the part run successful. Wiper die alignment is very critical Do not apply too much rake angle Recommended - Zero to 1.5 of rake angle
Tight Radius Bending Tooling Considerations Wiper die deflection must be minimum Wiper die tip should reach near tangent Wiper die radius must fit the bend die radius
Special Considerations and Applications Elliptical Groove
Special Considerations and Applications Elliptical Groove Eliminates Need For Mandrel or Wiper Die Deforms Tube To an Ellipse Typically Used on Non-Cosmetic Applications Ovality is Estimated at.7 Times Difficulty Factor
Special Considerations And Applications Elliptical Groove Can Only Be Used When Difficulty Factor Is Less Than 19 On Steel Can Only Be Used When Difficulty Factor Is Less Than 10 On Aluminum Or Copper Isn t Effective If Difficulty Factor Is Less Than 8 On Steel
Special Considerations And Applications Controlled Wrinkle Bend Die
Special Considerations And Applications Controlled Wrinkle Bend Die Used When D.F. IS More Than Elliptical Tooling Can Handle Usually Greater Than D.F. Of 20 Can Only Be Used To Approx. D.F. 27 without the addition of a mandrel Allows Material To Flow Into Cavity
Special Considerations and Applications Reach Adjusted Tools Dedicated Tooling Sets Clamp And Pressure Die Lengths Are Compensated For CLR Tools Are Made To Tighter Tolerances All Tools Are Sized To The Largest CLR Used Dramatically Reduces Set Up Time
Summary Utilize the longest clamp length possible Always revert to the basics when experiencing problems with tight radius bending Use bending Difficulty Factor calculation to determine the tooling requirements Consider tooling automation features or reach adjust tooling to reduce setup time and improve throughput.
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