Week 1:- Introduction to BiW and Fixtures Challenge

CHALLENGE 1

AIM = Answer the following questions with relevant images.

***I HAD USED IMAGES OBTAINED FROM SKILL LYNC VIDEO LECTURES AND FROM OTHER SOURCES LIKE GOOGLE, SINCE IT'S MENTIONED IN THE QUESTION TO PROVIDE RELEVANT IMAGES***

1. What is BIW & define its parts?

• In the automobile industry, It is the stage in automobile where body shell structure sheet metal components are welded together in weld shop just before painting.
• BIW design is always driven by aesthetic, aerodynamic and cost criteria

• Requirements of BIW structure:
  • Comfortable space
  • Strength & stiffness
  • Low weight material
  • Corrosion resistant
  • Aerodynamic & good appealing structure
  • Sufficient space for packaging and provisions made for inner trim and aggregates
  • Pedestrian and occupant protection during roll over accident
  • All exterior components like front bumper, rear bumper, fenders, mirrors, etc.. mounted on structure in means of mounting brackets and nuts on the BIW
  • Monocoque construction (Chassis in built in Body)
• BIW Components

2. What do you understand by BIW nomenclature?

• Nomenclature is basically choosing of names for things.BIW have no. of parts in it. All parts have differenent names.
• As the Automotive industry is spread worldwide. Every nation has its own language. So the same part of the BIW have different names in its region.
• For example, The one component of the BIW is called suspension tower in Uk & the same component is called shock tower in US.

3. What is fixture & its types?

• Fixture is a holding device which holds the workpiece to be processed. In general fixtures are designed using 3-2-1 principle. Further, fixture should firmly hold the work piece without causing vibrations, distortions, stresses in the workpiece and also fixture should not disturb or interfere the processing of the workpiece.
• Types of Fixture
  • Production fixture = These fixtures are used for mass production. Since these fixtures are used for mass production, they should be simple, rigid and hard. These fixtures should be periodically maintained in regular intervals to avoid errors and repairs. The design of the fixture should be in such a way that it should be easy to load and unload the workpiece within seconds to increase the productivity of the processing/assembly.
  • Pre production operation fixture = These fixtures are basically newly designed fixtures for the new products or parts. These may be complex, manual and heavy based on the application. These can be referred as the protype fixtures. Once the preproduction operation fixture functions properly, then modifications are made to improve and to make it simple and reliable. These fixtures are used in special cases or during initial or trail stages of processing/production
  • Checking fixture = These fixtures are used for checking and inspection purpose. No processing is done in these fixtures. These fixtures consist of gauges for checking the dimensions and tolerances and its accuracies. In some checking fixtures, fixtures are fixed and CMM devices check the geometrical accuracies.

4. What is the basic principle of fixture design?

• 3-2-1 principle is used for the design of the fixtures
  • For a fixture designer, the major portion of design time is spent deciding how to locate the workpiece in the fixture.
  • You know that any free body has a total of twelve degrees of freedom as below:
    • 6 translational DOF
      • +X
      • -X
      • +Y
      • -Y
      • +Z
      • -Z
    • 6 rotational DOF
      • Clockwise around X-axis (CROT-X)
      • Anticlockwise around X-axis (ACROT-X)
      • Clockwise around Y-axis (CROT-Y)
      • Anticlockwise around Y-axis (ACROT-Y)
      • Clockwise around Z-axis (CROT-Z)
      • Anticlockwise around Z-axis (ACROT-Z)

5. Elaborate types of BIW Stations?

BIW Station is the part of BIW assembly line. The BIW assembly line is divided into zones & these zones are again divided into stations. The BIW stations are further divided into following:
Tool stations	Geo Fixtures In BIW we consider Tack / Geo In Geo fixture tack welding done for all the parts to be assembled in that fixture. The geo fixture defines the geometry of the part.All the parts must be located with two locating pins ( Pin can be common for two or more )with tight accuracy standard. In the case of the Geo fixture, all the machine parts individually should be made with max tolerance of ± 0.02 mm. Whereas positional accuracy of the pin should be within -0.15 mm. In Geo fixture spots/ MIG welding done in such sequence that after taking out from the fixture it achieve the desired accuracy and doesn’t get disturbed during transportation from Geo fixture to re-spot Geo fixture control the sub assy accuracy in all the 3 axis.
	Re-Spot Fixture In BIW we consider Re-spot In Re-spot fixture remaining tacks are completed. Suppose in an assembly we need 50 welds On one station we cannot complete all these operations because it will take more time & another station relative to the assembly will be in ideal condition. In this type of case, we carefully choose some weld tack points which will define the geometry of the part & also the assembly will not get deformed after opening the clamping or in transportation due to the welding The remaining weld tacks will be completed in a Re-spot fixture as per By performing this kind of operation no station will be ideal Hence we use Re-spot fixtures. Re-spot fixtures also have very tight positional Re-spot jig pin tolerance will be -0.28 mm.
	Marriage / Hemming Fixture As the name suggests the marriage of different assemblies is carried out in this In different zones of the assembly line, different assemblies are completed like underbody, Side body, Front body, Rear body, etc. After this, all the parts come to the station where all parts are gets assembled by using various joining techniques like welding, Gluing, Riveting This station is called a marriage tool.
	Framer fixture Framer fixture is next station after the marriage. In framer fixture, the roof is attached to the output of the marriage fixture & it forms like a frame hence it is called a framer
	Checking Fixture These are used to check the assembly of parts, Tolerance, Dimensions & It can be of gauge type, Fixed type of automated checking. A checking gauge is a tool where the workpiece is held & different measuring gauges are introduced to ensure dimensions & repeatability. A fixed type checking fixture is used where the workpiece is fixed with clamps & pins & CMM is used which measures the coordinates of the different points of the panel or Then is compares with the CAD data & gives a report.
Gripper stations	A gripper is a device that enables the holding of an object to be manipulated. The easier way to describe a gripper is to think of the human hand. Just like a hand, a gripper enables the holding, tightening, handling, and releasing of an object. A gripper is just one component of an automated system. A gripper can be attached to a robot or it can be part of a fixed automation system.
	Material Handling Gripper These grippers can pick assembly from one station & will drop the assembly at another
	Process Grippers These grippers are used to carry out some specific processes like gluing, welding, riveting in addition to material handling. The gripper will go under gluing stand in case of gluing process & will goes under the pedestal weld stand in case of the welding process.
	Combo Gripper Combo grippers are the ones which can carry out multiple tasks like it can do material handling & also it can carry out some specific process like gluing, welding as well. Weld gun + Gripper
	Dual Gripper These are two-sided In case when we want one LH & one RH part, these grippers are used. It can handle the material from one station to another station Gripper + Gripper
Stand station	Stands are used to hold the part when not in use or also it is used to mount some parts or bodies on it. Pedestal Stands = Weld gun is mounted on the fixed stand which is mounted to the floor The gripper can carry the panel under the stand to do the operation. Gluing or Sealer Stand = Gluing gun or sealer gun is fixed to a welded or a standard stand which is grouted to the floor Docking Stand = The robots have some limitations such as the payload capacity of the robot.When we select the robot for multitasking it can't do both the task simultaneously. In this kind of case, we add a docking stand to put some equipment that is not in use for the current operation but will be required for next terms. Hence the robot can drop a gripper or gun & pick the next operation equipment to complete the task from the docking. Date Stamp Stand = Every manufactured product has some data to stamped or to be embossed on it like serial no, batch no, Date for some future reference, or for data collection.The required data is stamped or embossed by using the mounted stamping device.
Miscellaneous stations	Curing = After gluing it needs some time to cool down, so we put the assembly on some belts & it will take the panel to another station & meanwhile gluing will cool down.
	Buffer Stand = After some operation, we can put the no. of assemblies in this stand which is buffer stock & it can be transported to another station in easy They are also used to store the inventory while the machine is undergoing some maintenance.
	Take out Trolleys = It used to take out some panels for inspection to rectify the process is going in the right or not between the cycle.
	Conveyor = The conveyor is the rotating path that transports the parts to the next station which are kept over it.

6. What are the basic terminologies used in the BIW fixture?

• NC/Mylars/Fingers = Mylars is the component which holds the panel while operation. These are placed from top side & from bottom side also. The top side Mylars called as Clamping Mylars & the bottom side Mylars called as Resting Mylars. Every clamping Mylars have resting Mylars. It dont allow deformation of the part due to welding stresses.

• Principle Locating Points (PLP) = These are the points that are used for the accurate location of the part to maintain the geometry of the There is lots of holes on the panel which are not accurate due to stamping operation. The PLP are defined in the drawing. The positional dimensions or relative dimensions are very precise in stamping & in fixtures also.

• Risers = Risers are of different types like L-typer rises, Square tube riser Riser is the manufacturing part which gives height to the assemblies.

• Blade = Blades are plates mounted on the Other parts like cylinder, arms, etc are mounted on the blade.
• Shims = Shims are the small part that comes with the thickness of 0.1mm, 0.2mm, 0.5mm, etc. These will compensate for the stackup tolerance which reflects at the panel holding part called We give tolerance to all the parts of the fixture. Due to this tolerance, the Mylars will either lift up or goes down from their defined position.
  • If the Mylars go down from the defined height it will make an impression or dent on the panel. If the Mylars lift up then there will be a distorsion due to welding stress. To adjust the Mylars At its defined position we use shims so the panel won't be deformed & also don't get any impression on it.

• Rough locators = The operator can place the part in the wrong orientation The rough locator will work as a guide while placing the part in the fixture & the part will be loaded in the desired orientation. It is a part of foolproofing.
• Hardware = Hardware is like the Hex head bolts, Allen Bolts, Hex nuts, Spring washers, Self-locking nuts.
• CMM = CMM stands for coordinate measuring It is a device that measures the geometry of physical objects by sensing discrete points on the surface of the object with a probe. It generates a report by comparing the data with the CAD file data.

• Unit = The fixture is the assembly of different types of units to form a There are different units like pin unit, base unit, clamping unit, etc.
• Number plates = The number plate is the aluminum embossed plate placed on each unit for easily recognizing the
• Nameplate = The data like manufacturing company name, fixture type, Fixture weight is embossed on the plate & joined to the fixture.
• Clamp Arm = The clamp arm is the part of the clamp unit which moves an Over clamp arm the Mylars are mounted.
• Pivot = It is an axis about which the clamp arm will rotate.
• Class A Surface/Skin surface = The outer panels of the car like a hood, door, backdoor, fender, roof are visible to the customer. The outer panels should be aesthetically very good. No scratches or dent is acceptable over it. While designing the fixture to the skin surface the clamping material should be soft, so that it could not able to left any impression or dent over the skin. generally, nylon or PU material is used for clamping purposes.
• Reed switches & sensors = These are the electric components used in automated The reed switch is an electrical switch operated by an applied magnetic field. The detects the panel is loaded or not is done by sensors.