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  1. 1. Referent · 16.01.2016 1 von xx Seiten Manufacturing report on Car Bonnet Anuj Kamble (S0555276) AM-2,MBA&E WS2015
  2. 2. Referent · 16.01.2016 2 von xx Seiten  Specification: Bonnet is a part of subsystem of a car “closures”, which also contains doors and tail gate. It is fundamentally a reinforced skin panel with many safety and quality requirements. Bonnet usually do not directly open onto the passenger cell which greatly reduces the importance of certain functional requirements normally associated with closures such as passenger safety, air tightness, low cycle fatigue strength.  Application: Bonnet is hinged to the cowl part. It is surrounded by weather strips along its periphery resting on fender. Bonnet is an access panel to the engine compartment to enable maintenance of power train, drive belts, battery, fluid levels and lamp units.  Features:  Pedestrian Safety  Aerodynamic improvement  Styling  Noise reduction Product Definition
  3. 3. Referent · 16.01.2016 3 von xx Seiten Bonnet Assembly and child parts: 1. Inner Panel 2. Outer Skin panel 3. Hinge reinforcement –LH 4. Hinge reinforcement-RH 5. Lock reinforcement 6. Acoustic padding 7. Gas spring Product Specification 1 2 4 3 5
  4. 4. Referent · 16.01.2016 4 von xx Seiten Functions of child parts of Bonnet assembly:  Inner Panel: Provides stiffness to bonnet acts as a supporting frame to bonnet assembly.  Outer Skin panel: Provides covering to inner panel assembly, improves visual quality  Hinge reinforcement –LH/RH: Support hinges for bonnet lifting mechanisms  Lock reinforcement: Support locking mechanism  Acoustic padding: Provides noise reduction  Gas spring: Provides ease in lifting of bonnet
  5. 5. Referent · 16.01.2016 5 von xx Seiten Design Aspects : Following aspects must be considered while designing of the bonnet.  Pedestrian Safety: It is a non technical requirement but now a days it is one of the most important legal requirement in many countries. According to vehicle safety norms while considering Pedestrian Safety following points must be considered:  Child Head & hip impact Criterion  Adult Head & hip impact Criterion  Bonnet leading edge geometry  Space must be created between the bonnet and engine components underneath in order to create a safe bonnet that will absorb some of the energy in a controlled manner to prevent injury. Technical & Non Technical Requirements Source:‘The Aluminium automotive manual- The Design case study on bonnet & boot lid ’Version 2011 © European Aluminium Association (
  6. 6. Referent · 16.01.2016 6 von xx Seiten  Vehicle Quality:  Torsional Stiffness  Flutter/ Bending Resistant  Dent Resistant  Corrosion Resistant  Low mass ( For easy opening , Low mass contribution in total Vehicle mass)  Engine Noise Reduction  Low maintenance  Aerodynamic outside panel  Effective inside engine cooling. Technical & Non Technical Requirements Source:‘The Aluminium automotive manual- The Design case study on bonnet & boot lid ’Version 2011 © European Aluminium Association (
  7. 7. Referent · 16.01.2016 7 von xx Seiten  Styling:  Tight radii on hemmed panel edges  Excellent painted surface quality  Stretch flanges  Good Shape ( Low strain doubly curved surfaces)  Manufacturing:  Inner Panel: Excellent Weldability , Galling Resistant , Paint drain feature  Outer Panel:  Dent resistance during assembly  Clean Sheared edges  No visual defects resulting from stretch forming. Technical & Non Technical Requirements Source:‘The Aluminium automotive manual- The Design case study on bonnet & boot lid ’Version 2011 © European Aluminium Association (
  8. 8. Referent · 16.01.2016 8 von xx Seiten Desired characteristics and manufacturing techniques: Material Characteristics: Corrosion resistant Elastic Limit Total Elongation Surface Hardness Stretch-Strain defects N-Value R-Value Surface Quality pot forming Surface roughness Pint bake response Hem flange capabilities Fatigue Resistance Low density Lubrication Coefficient Shape Characteristics: Swages Section Collapse initiation Feature Stretched outer skin panel Drawn inner panel Flanged holes Flat hem flanged front edged skin panel Rope hem flanged upper edged skin panel Flanged panel edges. Manufacturing: Tooling cost Stamping Blanking & Punching Spot welding Self pierce rivets Adhesive bonding Finishing Anti corrosion coating Painting Cycle time Source:‘The Aluminium automotive manual- The Design case study on bonnet & boot lid ’Version 2011 © European Aluminium Association (
  9. 9. Referent · 16.01.2016 9 von xx Seiten Material Selection criteria for Bonnet Components:  Stiffness of Bonnet due to inner panel: • E and Yield strength requirements for global vehicle stiffness. Global vehicle torsional and bending stiffness is decoupled from the bonnet system. • Bonnet stiffness is obtained through section properties and material thickness. Vibration stiffness is obtained from careful design of bonnet inner panel and anti flutter mastic connecting it to the outer surface. Mastic properties and bead size are chosen so as to avoid print through or witness marks on the visible painted surface. The resulting stiffness is designed to be high enough to avoid visible flutter resulting from aerodynamic effects. Materials Selection: Source:‘The Aluminium automotive manual- The Design case study on bonnet & boot lid ’Version 2011 © European Aluminium Association (
  10. 10. Referent · 16.01.2016 10 von xx Seiten  Dent Resistance for Outer skin Panel of Bonnet :  Dent resistance is split into two categories; quasi-static and dynamic.  Quasi-static (very low speed) dent resistance is necessary to avoid plastic deformation from handling operations in the assembly plant and from palm or finger tip pressure during normal opening and closing operations.  Dynamic dent resistance is necessary to limit or eliminate local dents from high speed impacts of free road surface stone chips and other flying objects. • Quasi-static (QS) dent resistance is the more important of the two because it directly influences manufacturing costs and scrap rates of skin panels. Source:‘The Aluminium automotive manual- The Design case study on bonnet & boot lid ’Version 2011 © European Aluminium Association (
  11. 11. Referent · 16.01.2016 11 von xx Seiten Source:‘The Aluminium automotive manual- The Design case study on bonnet & boot lid ’Version 2011 © European Aluminium Association (
  12. 12. Referent · 16.01.2016 12 von xx Seiten  From the Prioritization matrix there are following materials which can be selected for the bonnet.  For inner panel: AL 6XXX , Laminated 5/6/7XXX Sheet steel, High performance Plastics/composites  For outer panel: AL 6XXX , Laminated 6/7XXX Sheet steel  For my bonnet , I am selecting AL 6000 material.  For inner panel; sheet thickness should be 0.7-0.8 mm  For outer panel; sheet thickness should be 0.5-0.6 mm
  13. 13. Referent · 16.01.2016 13 von xx Seiten  To make 100,000 car bonnets per year; I have to adapt automation process. Automation in Bonnet manufacturing can be achieved by using Industrial robots for process like Spot welding, Roller Hemming Process and bonnet painting process.  For Bonnet assembly manufacturing following process will be automated:  Spot welding  Hemming  Painting  Following processes will be manual:  Bonnet fitment to car body  Acoustic padding & Lock fitment to bonnet  BIW quality checks, Welding quality tests , Paint quality test, Corrosion tests  Final product Inspection Manufacturing process for Bonnet:
  14. 14. Referent · 16.01.2016 14 von xx Seiten Assembly plan /Manufacturing diagram for Bonnet: Inner panel assembly of bonnet Robotic Spot Welding Outer skin panel of bonnet O/P from press shop with stretch drawing Stamping, Flanging processes Robotic Roller Hemming Bonnet assembly Bonnet Fitment to BIW Robotic spray Painting of whole car body. Anti Corrosion coating (KTL) Assembly shop Acoustic padding for noise reduction+ Lock fitment Final Bonnet Assembly Welding Quality check Gap & Flushness test Paint quality check. Pedestrian Head/Hip impact test.
  15. 15. Referent · 16.01.2016 15 von xx Seiten  Robotic Spot welding cell: In this robotic welding cell inner panel of bonnet assembly will be spot welded. This robotic welding cell contains Industrial Robot, Spot welding gun, Robot controller, Welding controller, Welding fixture, Safety fences, Light curtain (sensors to sense operator presence), Child parts storage bins , Final inner panel assembly storage trolley. Output of this spot welding cell will be inner panel assembly of bonnet which will then be input to the hemming cell.  Robotic roller hemming cell: There are several automation processes for hemming are available like die-press hemming, table top hemming but for bonnet hemming I am selecting robotic roller hemming process to have flexibility in automation so that I can hem different variants of bonnet by just changing hemming bed and robot program. Hemming cell contains Industrial robot, Robot controller, Hemming bed, Safety fences, Light curtain, Child parts storage bins , Final Bonnet assembly storage trolley. Output of this hemming cell will be bonnet assembly. Which will be fitted to the car body at fitment station. Manufacturing process for Bonnet:
  16. 16. Referent · 16.01.2016 16 von xx Seiten  Bonnet fitment station: At this station Bonnet is fitted to the car body. Bonnet assembly is lifted with the help of pneumatic jigs and then fitted to the car body manually. Bonnet is hinged to the car body and gas springs are provided for easy opening of the bonnets. Once bonnet is fitted to the car body gaps and flushness are checked at all the areas with gauges.  Painting station: Anti corrosion coating is applied to bonnet by KTL process. After KTL process color of bonnet changes to whitish brown. At this station 3 layers of paint is applied to the bonnet. Robotic spray painting process is used to have uniform thickness of paint at all over the bonnet. With robotic spray painting less paint is wasted and cycle time is also optimized. Different colors of paint can be applied to bonnet with this setup. Paint quality and paint thickness are checked after painting.  Assembly station: After painting quality checks acoustic padding and lock is attached to the bonnet assembly. Manufacturing process for Bonnet:
  17. 17. Referent · 16.01.2016 17 von xx Seiten  Spot welding Process: Spot welding is a process in which contacting metal surfaces are joined by the heat obtained from resistance to electric current. Work-pieces are held together under pressure exerted by electrodes. The process uses two shaped copper alloy electrodes to concentrate welding current into a small "spot" and to simultaneously clamp the sheets together. Manufacturing process for inner panel: Source: Welding-Works.jpg
  18. 18. Referent · 16.01.2016 18 von xx Seiten Manufacturing process for Bonnet inner panel:  Bonnet inner panel assembly is mainly comprised of stamped child parts such as inner frame, Hinge reinforcement, Lock reinforcement. All these child parts are joined together by spot welding process. Welding fixtures are used where operator loads the inner panel and then all respective child parts on the fixture to their desired location.  While deciding location of spots on the panel I have considered that geometry of all the child parts are fixed on inner panel. The distance between two spots is not less than 30mm to have better spot quality.  The welding fixture is designed considering ergonomic conditions of operator, ease in accessibility for welding gun ,Fixing Geometry and satisfying all geometric and design tolerances for inner panel assembly.  While deciding spot welding sequence cycle time optimization and full robot utilization is considered. While designing layout for spot welding robotic cell operator safety is considered.
  19. 19. Referent · 16.01.2016 19 von xx Seiten Spot plan for welding of inner panel: FIXTURE 11 2 56 47 8 3 9 10
  20. 20. Referent · 16.01.2016 20 von xx Seiten Schematic Layout for robotic spot welding cell: Robot X-Gun Bonnet inner panel Welding controller Robot Controller Operator Safety Fence Welding Fixture Laser curtain Storage area for Child part bins Storageareafor finishedinner paneltrolley
  21. 21. Referent · 16.01.2016 21 von xx Seiten  Hemming process: A hem is a bent edge of a metal sheet. Hemming is a process by which that edge is bent. In an outer part (orange) is bent around an inner part (black) by hemming. It gives a neat and a compact joint.  Bonnet assembly is manufactured by hemming process. Inner Bonnet panel assembly and outer bonnet panel are hemmed together by robotic roller hemming process.  Rope hemming is done on the windshield side area of the bonnet. And all other sides are flat hemmed. (a) Rope Hemming (b) Flat Hemming Manufacturing Process Bonnet Assembly: Image Source: Jonkers, B , “Simulation of the Robot Roller Hemming process.pdf”, November 2006
  22. 22. Referent · 16.01.2016 22 von xx Seiten Robotic roller hemming process for Bonnet Assembly:  Adhesive sealant is applied on inner panel of the bonnet. This process is done manually. Operator follows the sealant plan and applies sealant on inner panel. Sealant acts as an adhesive and reduces relative motion between inner and outer panel of bonnet. Sometimes sealant also used to reduce vibrations in bonnet.  After application of sealant inner panel assembly is loaded on outer panel.  A robot guides a roller parallel along the flange of outer panel. Complete bonnet is hemmed with same roller.  In between the hemming steps the orientation (angle) of the roller is changed as shown in previous figure.  The hemming bed is designed considering ergonomic conditions of operator, ease in accessibility for roller, Fixing Geometry and satisfying all geometric and design tolerances to achieve good hemming quality.  Robot programming is done according two 3 hemming steps and robot path is optimized to achieve cycle time. While designing layout for robotic hemming cell operator safety and material storage areas are also considered.
  23. 23. Referent · 16.01.2016 23 von xx Seiten Schematic Layout for robotic roller hemming cell: Robot Hemming Roller Bonnet Assembly Robot Controller Operator Safety Fence Hemming Bed Laser curtain Storage space for inner and outer panel trollies Storagespacefor bonnetassembly trolly
  24. 24. Referent · 16.01.2016 24 von xx Seiten  Welding Quality/ Strength Test: Destructive welding quality test: ISO 14324:2003 specifies test procedures for fatigue testing spot welds, at ambient conditions, under repeated tensile loading to produce either shear or cross-tension loading of the spot weld, in steel of sheet thicknesses of 0,5 mm to 6 mm. Product inspection: Image Source: Google images
  25. 25. Referent · 16.01.2016 25 von xx Seiten  Ultra sonic testing ( Non destructive test):If the weld is improperly formed, it is possible that the two parts may not fuse completely, or that the area of the nugget may be smaller than what is required for a strong joint. With proper equipment and technique, ultrasonic spot weld inspection can quickly and nondestructively provide valuable information about weld quality.  To check spot welding quality of bonnet inner panel I will use destructive as well as ultrasonic testing because spot quality problems are seldom visible to optical inspection, and destructive pull tests are inefficient and limited to a few samples. Source: s/p01/p01.htm
  26. 26. Referent · 16.01.2016 26 von xx Seiten  Visual inspections:  After Hemming process: Visual inspections are carried out to detect hemming waviness and dimensional qualities after hemming process.  Gap & flushness test: After attaching bonnet to the car body gaps and flushness are checked all over the area. This is done by inserting standard gauges in the gaps between bonnet and car body.  Visual inspections are also carried to detect dents on bonnet surface and for other manufacturing defects .  Corrosion Tests*: Corrosion tests are carried out on bonnet to test effects of different atmospheric conditions on bonnet. This can be conducted in controlled environment. Bonnet paint quality is tested under different atmospheric conditions and then probable corrosion affected areas are determined. *Source: htm
  27. 27. Referent · 16.01.2016 27 von xx Seiten  Measuring thickness of paint: Thickness of paint is checked all over the bonnet to check uniformity of the paint. Thickness of paint is checked with a portable instrument and probe combine the magnetic induction method and phase –sensitive Eddy current method. Source: 06-measure-automotive-coating-thickness
  28. 28. Referent · 16.01.2016 28 von xx Seiten  Pedestrian Hip/head impact test: Evaluation of pedestrian safety for a bonnet must be carried out in the context of its surrounding elements:  Vehicle styling, size (wrap around distance “WAD”) and under bonnet clearance to other elements (considered as hard points).  Local bonnet stiffness is influenced by mounting point stiffness such as hinges, bump stops and latches.  This is better understood by superimposing the kinematics of a dummy onto the test conditions. Bonnet Head impact area Hip impact area Wind shield Source:‘The Aluminium automotive manual- The Design case study on bonnet & boot lid ’Version 2011 © European Aluminium Association (
  29. 29. Referent · 16.01.2016 29 von xx Seiten • Thum ,Manufacturing_Project_AM2_V1.pdf • ‘The Aluminium automotive manual- The Design case study on bonnet & boot lid ’Version 2011 © European Aluminium Association ( • A. AMBROZIAK, M. KORZENIOWSKI, ‘Using resistance spot welding for joining aluminum elements in automotive industry’ , Wrocław University of Technology, Łukasiewicza 5, 50-371 Wrocław, Poland • Rsw_of_aluminium_V4.pdf ( Developments towards high-volume resistance spot welding of aluminium automotive sheet component , International Automotive Research Centre , Warwick Manufacturing Group, the University Of Warwick, CV4 7AL UK • Jonkers, B , “Simulation of the Robot Roller Hemming process.pdf”, November 2006 • • • • • • References:
  30. 30. Referent · 16.01.2016 30 von xx Seiten Thank you!!!