Table Of Contents
3.0 Product
3.1 Introduction Of General Press And Die Requirements3.2 Types Of Hems
3.2.1 Modified Flat3.2.2 Flat3.2.3 Rope3.2.4 Partial
3.2.5 Downstanding
3.3 Product Design Requirements (Steel)
3.3.1 Typical Flat Hem Sections for Steel Closure Panels
3.3.1.1 Flat Hem Straight Section (Steel)
3.3.1.2 Flat Hem Concave (stretch) Section (Steel)3.3.1.3 Flat Hem Convex (shrink) Section (Steel)
3.3.1.4 Flat Hem Character Line Section < 40 mm Width (Steel)3.3.1.5 Flat Hem Character Line Section >= 40 mm Width (Steel)3.3.1.6 Flat Hem Corner Section (Steel)
3.3.1.7 Flat Hem Laser Weld Joint Section (Steel)
3.3.2 Typical Rope Hem Sections for Steel Closure Panels
3.3.2.1 Rope Hem Radius Requirement3.3.2.2 Rope Hem Straight Section (Steel)
3.3.3 Decklid - Single Piece Outer (Steel)3.3.4 Door (Steel)
3.3.4.1 Door - Cargo (Steel)
3.3.4.2 Door, Front - Door-Into-Roof (Steel)3.3.4.3 Door, Rear - Door-into-Roof (Steel)3.3.4.4 Door, Front - Frame-Under-Glass (Steel)3.3.4.5 Door, Rear - Frame-Under-Glass (Steel)3.3.4.6 Door, Front - Headerless (Steel)3.3.4.7 Door, Rear - Headerless (Steel)3.3.4.8 Door - Sliding (Steel)
3.3.5 Endgate (Steel)3.3.6 Hood (Steel)
3.3.6.1 Hood (Steel)
3.3.6.2 Hood - Clamshell (Steel)
3.3.6.3 Hood - With Headlight Cutouts (Steel)
3.3.7 Liftgate (Steel)
3.3.8 Rear Access Panel (Steel)3.3.9 Roof (Steel)
3.3.9.1 Roof - 2-Sided Hem (Steel)3.3.9.2 Roof - 4-Sided Hem (Steel)
3.4 Product Design Requirements (Stamped Aluminum)
3.1.4 Typical Rope Hem Sections for Aluminum Closure Panels
3.4.1.1Rope Hem Straight Section (Aluminum)
GM North American Hemmed Panel Standard
3.0 Product
3.1 Introduction For General Press And Die Requirements
The purpose of this report is to attempt to understand, summarize, andexplain all of the hemming recommendations that have been assimilatedby General Motors. Many of these recommendations can be generalizedacross vehicle platforms. All sketches in this document are not to scaleand do not represent a specific product design. They are used toexpress concepts and ideas only.
3.1.1 Hem Press and Die Basics
Understanding basically how the hem press works may allowsignificant cost savings through design for manufacturing. Theouter panel is located up/down and fore/aft for side closures (crosscar and fore/aft for front and rear closures) by several small blades(usually 2 per side). Relief for the locator blades must be providedin the lower die, the pre hem steels, and the final hem punch.Sometimes a block will be used in the handle pocket to better
locate the outer panel. The cross car for side closures (up/down forfront and rear closures) location is controlled by the lower die. Asthe ram on the press is lowered, the inner panel is located fore/aftand up/down for side closures (cross car and fore/aft for front andrear closures) by gauge pins in the spider. The gauge pins areslightly undersized to the holes. The hole surfaces should be
perpendicular to the pins. A full periphery blade holds the inner tothe outer, while blocks locate the 'S' surfaces on the inner panel,and ck's correct for inner panel springback.ssckgage pins to locate innercklower die
The hem press generally uses a cam operation for pre hem and afull periphery anvil for final hem. Individual product design mayrequire the final hem to be a cam operation. The target maximumfor direct hemming is 60° (70° is the highest ever achieved). If theproduct design requires the panel to be tipped too far, a cam isused for the final hem.
blades to locate outer~2 per side
Release Date: November 10, 1999Revision Date:
Questions/Comments Contact: Paul Tyckoski 810-947-0419 (8-227-0419)
GM North American Hemmed Panel Standard
presspressurepadcamdirection60° max<30°direct final hem
cam final hem
3.1.2 Pressure Pad
The hem press utilizes a full periphery pressure pad. This padserves a variety of functions throughout the hemming operation. Ithelps to ensure a high quality hem by holding the inner to the outerpanel, and it prevents the panels from slipping within the die.
Panels must be designed to allow room for the full periphery pad. Itis preferred to have 6.0 or 7.0 mm to package the pressure padaround the periphery of the door.
weatherstripretainer6 ~ 7 mm1.01.0final hem punchtpressurepad± 0.7inner panelouter panelSample sections are shown for reference. The \overflanging of the outer panel should be considered when
designing these sections. It is also important to consider the detailouter panel hem flange trim line. This trim line must be controlleddue to the tight condition between the trim line and the fullperiphery presser pad.
Release Date: November 10, 1999Revision Date:
Questions/Comments Contact: Paul Tyckoski 810-947-0419 (8-227-0419)
GM North American Hemmed Panel Standard
1.01.01.0final hem punchpressurepadfinal hem puncht1.63.0pressurepadR3.0R3t0.7t0.7t0.73.02.42.5** not to scale ** not to scaleleading edge of door
1.0bottom edge (sill) of door
final hem punchpressurepadt1.6t0.7** not to scalepressurep3A~4AadAbarrier flange of door
The pressure pad is commonly relieved to allow clearance.Usually, a 1:4 ratio is used to determine the allowable relief.3.1.3 Determining the Panel Tip Angle
Ideally, the hem press centerline is aligned with the detail outerpanel die datum lines. The same up/down and cross car die datumlines should be used for both front and rear doors. This helps toreduce complexity and allows easy part transfer into and out of thehem press.
Ideally, the press direction should be perpendicular to the innerpanel surface. This allows the upper ram to accurately locate the
Release Date: November 10, 1999Revision Date:
Questions/Comments Contact: Paul Tyckoski 810-947-0419 (8-227-0419)
GM North American Hemmed Panel Standard
inner panel to the outer panel using the inner panel gauge holes.Some accuracy may be sacrificed if the inner panel is tipped. Thisshould be resolved early in the design phase.spidergage pins to locate innerHowever, the product design may require that the panel be tippedfor hemming. This issue must be studied for every specific productdesign. A list of a few general items that may force a change to thepanel tip angle includes:
1. A small wall angle (less than 3°) when measured to the bodygridlines at the beltline or at a recessed molding area.2. Over 30° of curvature at the belt.3. Over 30° of curvature at the sill.
All three of the above conditions are important. A balance betweenall three must be found and the optimum tip angle decided. Usuallythe beltline is considered most important, feature lines and
recessed molding areas secondary, and the sill area least importantfor hem quality.
A good example of a case where the tip angle had to be changed isthe '97 C car design (see next page). The angle of the beltline wasoriginally -8° from the body grid line and the angle of the door at thesill was 15°. The panel had to be tipped 11-12° to allow 3-4° forhemming at the beltline and sill.
Release Date: November 10, 1999Revision Date:
Questions/Comments Contact: Paul Tyckoski 810-947-0419 (8-227-0419)
hemproduct(门包边设计)
