Week 3:- BiW Fixture Design Methodologies Challenges

1. Design methodologies is nothing but the steps followed during designing stages of fixture design

Design methodologies are :

• Purchase Order
• Inputs from customer
• Percentage completion criteria
• Design output

2. Inputs required from customers in fixture designing are:

• Functional requirements
• Preferred Standard components
• Car products
• Layout
• Ergo Data
• Weld Study
• Standard Detailing Templates

3. Car Products inputs are

• GD & T
• Part lists
• Cad Files of Car part
• Clamp Plan
• Product assembly process sheet

4. Clamp Plan: Clamp plan provides the location of pins, rest, clamp, Dumps, etc.

5. Purpose of Layout:

Layout provide information of

• Flow of parts
• Station pitch
• Robot Stations
• Accessories like Tool Changer and Tip Dresser
• Sub assembly links
• Platform height
• Loading/Unloading sequences/heights

6. ERGO DATA:

It is given for manually operation as an human operator is required. It is given so that an operator can do the operation efficiently and without fatigue.

Ergonomics refers to the study of human behaviour

Ergo data provides information of loading height, working safety zone of operator, etc.

7. WELD STUDY:

Weld study is a study that includes:

• Weld gun details
• Weld matrix and weld points:
  Weld points are the points at which welding is suppose to happen. They are of two types:
  • Geo weld points
  • Re-spot points

8. PERCENTAGE COMPLETION CRITERIA:

Percentage completion criteria is followed in the designing stages and dispatch stages of the welding fixtures.

0-25 %	- Input and Concept design
25-40 %	- Concept approval and Simulaiton check
40-85 %	- Design freezing and Detailing
85-100 %	- Check and Final Disptach

9. DESIGN OUTPUT:

The output is 3D models and 2D drawings of the tools.

• Unitized tools: (multiple units on a common base) requires two type of drawing sheets
  • Key sheet: An index of units and their placements on the tool base
  • Layout sheet: A detailed drawing of individual units to include all of their components.

• Non- unitized tools: Tools that can stand alone and can be detailed completely on a layout sheet.

10. STRUCTURING A DESIGN TREE:

Structuring a design tree implies to a process where all the assemblies and parts are named in a specific standard. Different customer have different set of standards to structure a design tree.

It helps in reducing error by:

• Identifying a specific part or assembly. as to which project, tool or unit, it belongs to.
• Avoiding the errors during design study, manufacturing, assembly, inspection, etc.
• Naming of a fixture or a unit or a part, that gives the information as to which project or zone or assembly do they belong.
• Identifying the quantity of items of same type or different types that are being used in an assembly.

11. UNITS:

These are unitized tools that form parts of a fixture assembly.

Types of units are:

1. Rest unit
2. Fixed pin unit
3. Retract pin unit
4. Base unit
5. Sensor unit

12. FIXED PIN UNITS:

An assembly of standard and manufacturing parts consisting location pin is called Pin unit. A pin unit in which pin’s position is fix, is called Fixed Pin Unit. Pin unit is used to lock the rotational position of panel. Round Pin is used to control panel in two directions while Diamond Pin is used to control panel in one direction.

13. PARTS OF FIXED UNIT:

• RISER
• BLADE
• SHIM
• L-BLOCK
• PIN
• PIN RETAINER

14. REST UNIT:

A rest unit is designed to rest/support the car panel using NC blocks/mylars/rest

PARTS OF REST UNIT:

• BLADE: The plate which connects Riser to the Clamp cylinder is named Blade.
• RISER: The part which is mounted on the base plate and holds a clamp or pin cylinder on it, is called Riser.
• L BLOCK: A plate shaped as L is called an L block. This part is used as a connection between mylar and Blade.
• SHIM: Shim is a set of thin plates (2 mm, 1mm, 0.5 mm, 0.25mm) that are used to adjust the gap or used for a better fit.
• SUPPORT MYLAR: Mylar which is used as a support is called Support Mylar. One support unit can consist of one to multiple numbers of Support mylars.

15. SENSOR UNIT:

It is a unit designed to sense the car panel by using electrical sensors. This signal from sensor will be fed to the PLC and so the next process will be executed by this signal.

Fundamentals of SENSOR UNIT:

• Every single loose panel which are being welded in a tool should be sensed.
• Each panel should be sensed by 1 to 2 sensors depend ont the size of the panel. Preferred to be in diagonal opposite ends of panel.
• Every sensor should be mounted in a 3 direction adjustable way in general.

16. ROUGH LOCATOR UNIT:

A RLU is a part designed to guide the operator, to locate the car panel on to the pins accordingly. A rough locator can be of standard part or make part.

Fundamental of Rough locator (RL) design:

• RL should be placed at the edges of the car panel, which it has to guide.
• RL has to be placed in the same angle of the car part edge with a minimum distance of 2-5mm from the edge of the car part.
• RL should guide the panel in pin arresting direction (in general)
• RL should start guiding the panel before 10 to 15 mm to start of pin engagement
• RL should be designed with entry angle for the car part entry.
• It should be designed with two slots to mount for easy adjustments (in general)
• The slots should be in the direction of car part guiding.

17. BASE UNIT:

A BU (Base unit) is the unit designed to mount all the other units (Clamp unit, pin unit, rest unit,etc) of the tool, also other parts necessary for a tool like pneumatic valve box, trunking cable path will also be mounted to a base unit

Parts of Base unit:

• Floor plate: Medium through which the BU is mounted to the floor
  
  
• Weld bar: Weld bar is structure of BU which mounts to floor plates and is connected to base plate through pedestal
  
  
• Pedestal: Smalls columns like structure for giving height to the BU
  
  
• Eye bolt: It is use to raise the base unit and relocate it if needed.
  
  
• Measuring hole cover: The measuring holes are used to define placements of various units (clamp unit, pin unit.etc). These holes are used as reference tools for panel placement also and are usuallt covered with a plate so that foreign particles, dust cannot enter into it.
  
  
• Valve box: It is a standard part that supply air to the pneumatic cylinders through solenoid valves.
  
  
• Base plate: structure on which various units are mounted.
  
  
• Trunking channel: It is a duct which channels the air supplied by the valve box to different cylinders by means of pipes.

18. DUMP UNIT: The panel that cannot be constrained by simple units are fixed using dump unit.

A dump unit is a very complex unit that consist of a dump cylinder, a clamp cylinder unit.

19. SLIDE UNIT: Slide unit consist of a slide cylinder which helps slide the panel onto a guide rail.

Stopper blocks are provided on other side of slide cylinder to restrict the movement of the unit.

Slide unit is used where space constraints are present.