Design of backdoor

Design of Backdoor

 

Aim:

       To design a backdoor of the car on sheet metal using the appropriate design and provided class A surface data by considering design parameters and make (Hinge, Gas stay, wiper mounting, latch & sticker) reinforcements and embosses.

 Back Door:

        The back door is a hinged door at the rear of the vehicle. It may be used for loading and unloading car, to get passengers in and out, in case there are seats present at the rear. The back door comprises of certain components which form the back door assembly together. These doors can be operated manually or electric powered automatic operating process. In most of the luxury car’s door is electrically operated.

 

Types of Back Door:

• Top Mounted Door
• Side Mounted Door
• Bottom Mounted Door

 Top Mounted Door:

                    Most model automobiles today have the back door connected to the top mounting door. For instance, Maruti Vehicles, Hyundai VERNA, Kia Salto, etc. Hinge connections are made between the roof top and the back door. One side's hinges will be attached to the roof, while the other side's hinges will be attached to the backdoor.

Side Mounted Door:         

Bottom Mounted Door:

            Estate cars and pickup trucks use bottom-type backdoor systems. These are the most convenient types of backdoors, in which the bottom door is supported by the gas stay or supporting clip. Hinge connections are made between the sill bottom and the back door. One side's hinges will be attached to the sill, while the other side's hinges will be attached to the backdoor.

Components of Back Door:

• Inner panel
• Outer panel
• Hinge reinforcement
• Gas stay reinforcement
• Wiper motor reinforcement
• Latch/striker reinforcement

Door parts thickness is given below,

• Outer Panel - 0.75 mm
• Inner Panel - 0.75 mm
• Reinforcements - 1.5 mm

Sheet metal processes used for manufacturing the back door

 Deep Drawing:

              Deep drawing is a sheet metal forming process in which a sheet metal blank is radially drawn into a forming die by the mechanical action of a punch. It is thus a shape-transformation process with material retention. The process is considered "deep" drawing when the depth of the drawn part exceeds its diameter. This is achieved by redrawing the part through a series of dies.

The sequence of deep drawn components is referred to as a "deep draw line". The numbers of components that form the deep draw line is given by the quantity of "stations" available in the press. In the case of mechanical presses this is determined by the number of cams on the top shaft. For high precision mass productions, it is always advisable to use a transfer press also known as eyelet press. The advantage of this type of press, in respect to conventional progressive presses, is that the parts are transferred from one die to the next by means of so-called "fingers". Not only do the fingers transfer the parts but they also guide the component during the process. This allows parts to be drawn to the deepest depths with the tightest tolerances.

Presses types:

Die-Set Transfer Press:

              Part is transferred via transfer fingers as the part progresses through the forming process. Tooling components attached to die plates enable the die to be installed in the press as one unit.

ICOP (Individually Cam Operated Press):

                The part is transferred via transfer fingers as the part progresses through the forming process. Die components are installed in the press one station at a time.

Progressive Die Press:

                   The part is carried on the steel webbing as it progresses through the forming process.

Tool materials:

                   Punches and dies are typically made of tool steel, however cheaper (but softer) carbon steel is sometimes used in less severe applications. It is also common to see cemented carbides used where high wear and abrasive resistance is present. Alloy steels are normally used for the ejector system to kick the part out and in durable and heat resistant blank holders.

Embossing:

          Embossing machines are a great example of a modern take on classic manufacturing methods. Typically, creating an embossed tag uses a die set to press a full design into metal. In comparison, a metal tag embossing machine uses a set of striking heads to add each character into the material individually. Metal sheet is drawn through the male and female roller dies producing a pattern or design on the metal sheet. Depending on the roller dies used, different patterns can be produced on the metal sheet. Embossing is a metal forming process for producing raised or sunken designs or relief in sheet materials by means of matched male and female roller dies, theoretically with no change in metal thickness or by-passing sheet or a strip of metal between rolls of the desired pattern.

Hemming:

             Hemming is a forming operation in which the edges of the sheet are folded over other part or simply folded in order to achieve a tight fit. In car part production, hemming is used in assembly as a secondary operation after deep drawing, trimming and flanging operations to join two sheet metal parts (outer and inner) together.

 

Blanking:

       During blanking, a metal workpiece is removed from the metal strip or sheet through punching. A metal punch is forced into a die, shearing the steel blank from the larger metal piece. This is typically a high-speed, continuous process that creates defects on trimmed surfaces. Blanking is a metal fabrication process where the final product is removed out of the larger metal sheet, and the remaining material is discarded as scrap. Blanking or cutting relatively thin and soft material hard material for example rubber, sponge, plastic container, function film such as PET, polarized/shield/reflection/light diffusion film, plywood and cardboard by means of fix-figured Die tools. Blanking machine is used for the above operation. Blanking is a metal production process, during which a metal workpiece is removed from the primary metal strip or sheet when it is punched. The material that is removed is the new metal workpiece or blank.

Punching:

          Punch tooling (punch and die) is often made of hardened steel or tungsten carbide. A die is located on the opposite side of the workpiece and supports the material around the perimeter of the hole and helps to localize the shearing forces for a cleaner edge. There is a small amount of clearance between the punch and the die to prevent the punch from sticking in the die and so less force is needed to make the hole. The amount of clearance needed depends on the thickness, with thicker materials requiring more clearance, but the clearance is always less than the thickness of the workpiece. The clearance is also dependent on the hardness of the workpiece. The punch press forces the punch through a workpiece, producing a hole that has a diameter equivalent to the punch, or slightly smaller after the punch is removed. All ductile materials stretch to some extent during punching which often causes the punch to stick in the workpiece. In this case, the punch must be physically pulled back out of the hole while the work is supported from the punch side, and this process is known as stripping.

Compare Blanking and Punching

Spot Welding:

                 Spot welding (or resistance spot welding) is a type of electric resistance welding used to weld various sheet metal products, through a process in which contacting metal surface points are joined by the heat obtained from resistance to electric current. The process uses two shaped copper alloy electrodes to concentrate welding current into a small "spot" and to simultaneously clamp the sheets together. Work-pieces are held together under pressure exerted by electrodes. The amount of heat (energy) delivered to the spot is determined by the resistance between the electrodes and the magnitude and duration of the current. The amount of energy is chosen to match the sheet's material properties, its thickness, and type of electrodes. Applying too little energy will not melt the metal or will make a poor weld. Applying too much energy will melt too much metal, eject molten material, and make a hole rather than a weld.

 

Received data:

              I received the top surface of the back door outer panel (top and bottom) to be repaired according to its smoothness. After repairing the surfaces to combine the surface sew, the door is divided into two parts: the outer upper panel and the lower panel.

Separate the top outer panel and the bottom outer panel from the back door. 

Top Outer Panel:

Bottom Outer Panel:

Tooling Axis:

           Create a point on the class A surface to move the main tool for component creation on the base surface. Mask an axis over the point created with the same directions as the main axis. Using Intersect command from Generative Shape design select the YZ plane as the first element and the class A surface as the second element After creating the intersecting lines select the Line command and join the vertices which show the most possible draft angle manufacturable.

 Create a point on the class A surface to move the main tool for component creation on the base surface. Mask an axis over the point created with the same directions as the main axis. Using Intersect command from Generative Shape design select the YZ plane as the first element and the class A surface as the second element. After creating the intersecting lines select the Line command and join the vertices which show the most possible draft angle manufacturable.

Inner Panel:

            The inner door panel is a component that is used for strengthening the door assembly, and it is one of the most important components on which all accessories are mounted, like hinges, glass guide channels, moulding trim, latches, etc. The possible method is the integration method. In the integration method, the part is stamped out of a single blank. This reduces the number of tools needed, the assembly cost, and any fit ability problems.

Sealing Flange:

Half Inner Back Door Panel:

Then, to improve the strength of the inner panel and to reduce the weight, a ‘V’ or ‘Y’ type embosses and other cut-outs are created. Also, for latch and staple mounting, a cut-out is created. This cut-out is also done on the other side of the inner panel to maintain the centre of gravity of the back door. Metal sheet is drawn through the male and female roller dies producing a pattern or design on the metal sheet. Depending on the roller dies used, different patterns can be produced on the metal sheet.

In most machines, the upper roll blocks are stationary, while the bottom roll blocks are movable. The pressure with which the bottom roll is raised is referred to as the tonnage capacity. This figure also depends on the aforementioned parameters. Emboss should be in a 7-to-25-degree incline in angle, and it should not be in a 90-degree angle.

The inner panel has a thickness of 0.75 mm. With reference to the coordinated right-side plane, move on the geometry mirror to complete the first half of the inner panel. The bottom of the latch fastening profile is created using the same procedure as the embosses and holes created in the centre viper motor for fixing viper motors. Created with embosses, the little cut-out on the corner makes it simple to assemble the interior components of the light, viper motor, and wiring harness. The embossing process can produce a variety of patterns. Some of the most common patterns include stucco, leather grain, wood grain, weather grain, and rough sawn cedar. Most embossers will tool to form any needed pattern, depending on the cost parameters involved.

I provided single mounting flanges for mounting the inner panel to the outer stylish panel. Single flanges provide enough strength to hold the outer and inner panels together with the help of sealants. In between the inner panel and the outer panel, we provide sealants.

Outer Panel:

        The outer panel of the back door is similar to the other Body in White components in that it is an aesthetic part of the vehicle. The coating provided is multi-stage and has the properties of scratch resistance, rust prevention, and smooth and attractive finishes. The outer panel also includes provisions for a tail lamp, a rear fog light, and licence plate mountings. Most hatchback cars have the provision for a wiper motor.

        Hemming reliefs, which are cut-outs on the hemmed corner of the panel assembly, assist prevent some hemming flaws including wave-like or wrinkle-formed surfaces. Hemming is a shaping process in which the sheet's edges are folded over or simply tucked under other components to create a snug fit. After deep drawing, trimming, and flanging procedures, hemming is used as a secondary operation in the assembly process of automotive parts to connect two sheet metal sections.

Corner Relief:

             A bend relief is just two tiny slits cut into a sheet of metal to release the metal between them. It divides the component's rest from the material you wish to be able to fold. Only when there is material on either side of a curve do you need it. The relief width to sheet thickness ratio must be more than 1.5, and the relief depth must deformation of the hole towards the bend- If a hole is made close to the bend line, it can wind up becoming an unexpected bend relief. If the hole is close to the bend line, distortion might occur.

Mastic Sealant:

             Mastic sealant helps to locally improve strength of the hood. It is generally a hard rubber part, which is introduced as a paste in between inner and outer panel of the hood, which will get hardened inside the furnace. Every mastic sealant point will have a tendency to improve the local strength in around 80 mm diameter. Considering this, the mastic points are positioned such that most of the hood region is covered. Surfaces do not have to be primed when using this type of sealant, and although applied thick, it adheres smoothly to any surface. It is important that the area to be joined or sealed be clean and dry, just like any other sealant on the market.

REINFORCEMENT:

                 The reinforcement provided consists of four numbers, which consist of hinge reinforcement, gas stay reinforcement, wiper motor reinforcement, and latch and striker reinforcement. In order to maintain the rigidity of the panel assembly, reinforcements are typically placed to increase the strength of the panel in specific localised areas that are relatively small compared to sheet metal parts. These reinforcements help the panel absorb loads placed on them and disperse them throughout the

panel assembly. In contrast to the 0.75 mm thick panel utilised in this section, reinforcements are typically 1-1.5 mm thick.

 Hinge reinforcement:

              For a motor vehicle door hinge, the hinge reinforcement can be attached to the hinge bracket and has a form that matches the shape of the hinge bracket. In order to be placed against the hinge pin from below the bracket onto the hinge pin between the bearing arms of the bracket, the reinforcement is designed with a fork-like feature on its first end facing the hinge pin. On the reinforcement's side facing the bracket, a cam engages a recess of the hinge bracket to prevent the hinge reinforcement from falling out. A fastening component connects the second end of the reinforcement to the hinge bracket.

Gas stay reinforcement:

                           Vehicle doors often include brakes, or 'stays', that slow the door down just before it closes, and also prevent the door from opening further than its design specification. The current trend is to have a three-stage door brake.  Door brakes exist because the doors on the first vehicles were heavy, so they had to be pushed hard to make them close. Soon after, automotive manufacturers managed to construct lighter doors, but users were used to closing doors with significant force; therefore, doors could become damaged. Door brakes were then introduced to slow down the door just before the door closed to prevent damage; these soon became standard.

Wiper motor reinforcement:

                      A little electric motor is strapped onto the back door to operate the wipers. To ensure good sight, the back windscreen is cleaned with it.

Latch/striker reinforcement:

                  Most vehicle doors are secured closed to the vehicle body with latches that may be locked to prevent unauthorized access from the exterior. There are a variety of car door locking systems. Door locks may be manually, or automatically operated, and may be centrally or individually operated. Also, they may be operated by remote control, with the transmitter often integrated into the main vehicle access and a key for the ignition. Additionally, rear passenger doors are frequently fitted with child safety locks to prevent children from exiting the vehicle unless the door is opened from the exterior. These are also frequently used on police cars, to prevent suspect criminals from escaping whilst in police custody. Vehicle door latches on practically all vehicles today are usually operated by use of a handle which requires the user to pull, lift, or tug - with some force towards themselves rather than push.

Latch Trajectory:

                    It is the path along which the hood rotates during opening and closing movement. The striker on the hood follows a particular path while opening or closing the hood, which is along circumference of a circle with centre at the hinge axis. This path is nothing but latch trajectory. It is a very important aspect in hood design, in order to decide hinge, latch and striker installation points.

 Draft analysis:

                    After Tooling Axis Select the Feature Draft Analysis option from the Insert Option. Next click on Use the compass to define the new current draft direction option and make it align with the tooling axis by dragging it to the axis. If the colour appears reg just click the invert option on the right side of the draft direction axis change button.

Important features used while designing:

Wave Geometry Linker: With this you can create, associative or linked copies of any entity of a part into other parts. It may be a surface, edge, curve, body, sketch etc. The changes made to the original entity will be reflected in the copy of that entity.

Extract Body: It is used to create an associative body by extracting faces, entire body or region of faces.

Bridge Curve: It helps to create a tangent blend curve between two objects. The objects may be edges or sketch curves.

Sew: It combines sheet bodies together by sewing their common edges. There shouldn’t be any gaps larger than specified tolerance.

Unsew: This command is used to separate the existing sheet body or solid body into multiple bodies.

Projected Curve: It is used to project an existing curve/curve on a selected plane or surface by selecting a direction for projection.

Trim Body: It is used to trim one or more bodies using a face or plane. You can also specify the bodies to retain and the bodies to discard.

Offset Surface: It allows you to offset one or more existing surfaces.

Offset Curve in Face: This command will allow you to offset particular edges or curves on selected faces.

Trim Sheet: It is used to trim off a portion of a sheet body using curves, faces, edges or planes.

Through Curves: It will allow you to create a body Through multiple sections, where it’s shape changes to pass through each section.

Law Extension: This command extends a curve or edge to create a sheet body at desired angle length by changing the rules under angle law and length law.

Trim and Extend: It helps you to trim and extend intersecting surfaces and make corner at their intersection.

Face Blend: It creates fillets between faces.

Edge Blend: It creates fillets on edges.

Extend Sheet: It will allow you to extend an existing surface to required distance.

Emboss: Emboss command creates an embossing by modifying a body with faces created by projecting a curve/section along a direction. You can modify the emboss using options like endcap location and draft angle.

Mirror Geometry: As name suggests, it allows you to mirror geometries about selected plane or surface.

Thicken: It is used to convert a surface to solid body by providing thickness.

Extrude: It helps you to create a feature from a sketch. You are also able to create thin feature using a sketch or curve under this command.

 Assembly back door:

                          In order to lessen impact during crashes, vehicle doors include reinforcing components. In one version, the structure will have a lower reinforcement panel that can attach to the chassis of a car and an upper reinforcement panel that is welded to the lower reinforcement panel. When the front deformable wall of the upper reinforcement panel is deflected, the lower reinforcement panel's rear deformable wall will also deflect.

 

 

 

Conclusion:

               The parts of the back door were designed from the given styling surface and all the reinforcements are designed and assembled by using the NX-cad.