BIW FIXTURES-DESIGN OF BASE UNIT

Aim:To Design a Base Unit for the Pin Units and Clamp units including Swivel clamp unit with all weldments for the given Car Panel.

Software Used:CATIA-V5

Car Panel:

Introduction:

1.Base Unit:
A 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 on to a base unit. Base unit also mounts the components like Valve Bank, Junction Box, Eye Bolts, trunking cable path etc.

Typical Parts of Base Unit:

• Base Plate:A flat supporting plate or frame at the base of a column, designed to distribute the column's weight over a greater area and provide increased stability.The base plate has no of holes drilled on it which will act as mounting points for clamp unit, pin unit and so on. Base Plate is a machined plate made of steel or Aluminium of thickness 25mm to 40mm on which the holes are drilled to mount diffrent units like rest units, clamp units, pin units etc.
• Pedestal:Pedestal is a part or an assembly (welded structure) that joins the base plate to the oor plate. Pedestal can be a standard part or a make part, depending on size and height of fixture. Standard pedestals are available in different heights. Pedestals are also available in different inclinations.Depending on the size of base plate,the number of pedestal for a fixture can vary for load distribution.
• Trucking Channel:Trunking Channel is a duct that carries all the electrical and pneumatic connections(wires and pipes) for units of the tool. It has a thickness of few millimetres.
• Valve Box:Valve Box is a standard part which contains all the valves for the pneumatic units. The valve box is the box which includes different solenoid valves. The pneumatic fixtures work on air pressure provided to it. So the arrangement of air pressure inlet & outlet is done within this valve box. The trunking channel includes all the pressure inlet cables going to the pneumatic parts of the fixture & protects them from damaging while operation is in process.
• Eye Bolt:Eye Bolts are the bolts that are used to lift the fixture for transportation by inserting hooks into them.
• Floor Plate:Floor Plates is grouted to the floor with xed bolt on the ground. Floor plates are also called foundation plates. There is a clearance of 10mm between pedestal base plate and oor plate. This gap is used to level the entire tool using leveling bolts. Weld bars are used to position the positions permanently. Weldbars are steel plates along the sides of base plate of pedestal.

2.Designing of Base Unit:

• Working Height:It depends on the nature of the manual or robotic welding fixture.For manual fixture we need to consider the working height 500-1100 mm , depending upon the working height of the worker standard of specific country will apply( In few countries human height is higher or lower e.g. US , Japan).If base structure is made with base plate having tubular structure welded below it you can reach to height 100 mm to ~250 mm.In this case to reach the working welding height you need to provide additional some leg structure which may have top and plate plate welded to tube.Study the gun ergonomic properly then design the unit height and then base top height.
• Eyebolt Size:It is important to know how big base plate or bigger base welded structure will be handeled during the fabrication and handling process.Depending upon the weight eye bolt size are selected for lifting holes on the base plate.Generally 4 eye bolt provision is made.It also need to select the location of eye bolt considering the rope/ belts used while shifting the structure or complete fixture are not damaging any units(rest,clamp or location units).
• Plate Thickness:Few OEM's recommend thick base plate 40mm or 50mm for the child part assemblies (e.g BMW). 40/50mm plate makes a very heavy structure but some OEM's follow methodology.
• Depending upon the component size and weight of the total units you can decide whether you need fabricated base or just plate.
• The base unit of the fixture must be strong enough so that deflection of the fixture is as minimum as possible. This deflection of a fixture is caused because of forces of welding, clamping of the workpiece.
• The Base unit of the fixture should have the mass to prevent vibration and chatter.
• The base unit may be built from simple sections so that other units may be fastened with screws or welded whenever necessary. Those parts of the fixture that remain permanently with the fixture may be welded. Those parts that need frequent changing may be held with the screws.
• The base unit should cover all the units with its outer periphery including the opening.
• The base unit should be parallel to the floor, To adjust this there should be the provision of the height adjusting mechanism.

Design of Base Unit:

Clamp Plan of panel:

Panel without Base Unit:

Base Plate Area:

Base Unit Design:

Conclusion:Hence,Base unit is Designed for the Pin Units and Clamp units including Swivel clamp unit with all weldments for the given Car Panel.