Week 3:- BiW Fixture Design Methodologies Challenges

1.What is Design Methodology ?

1.Design Methodology

Design methodology is the study of the principles, practices and procedures of designing. It is a process of analysis, synthesis and evaluation.

Types of design methodologies

Top Down Design or Stepwise Refinement

In this the end solution is known and works is carried out backwards, refining each step along the way.

Bottom Up Design

This methodology starts with a foundation and works up towards a solution.

Structured Design

This is an industry standard. The technique starts by identifying inputs and desired outputs to create a graphical representation.

Structured Analysis and Design Technique

This approach utilizes a diagram to describe the hierarchy of a system's functions.

Data Structured Systems Development

Data structure determines the system structure in this methodology.

Object Oriented Design

This methodology is based on a system of interacting objects.

Design methodology used for a BIW fixture design

It is the pre-design process carried out during the concept development phases in fixture design

Step:1 Purchase order(PO)

A purchase order is a contract between the buyer and the seller and it gives specific information like product or services to be delivered, delivery date, and any other terms and conditions

including the price. The purchase order is also called as ‘PO’.

Stages involved in PO

Stage 1- Purchaser creates purchase requisition.

Stage 2- Purchaser issues purchase order.

Stage 3-Vendor approves rejects, or submits PO for discussion.

Stage 4- Purchaser records purchase order planner.

Details mentioned in PO

• Description of the products that are ordered
• Quantities of the parts(kg, meters, numbers etc.,)
• Price at the time of order
• Name of the vendor to whom the purchase order is being sent
• Shipment address.
• Billing address of the company
• Terms and conditions of payment.
• Due date of delivery/consignment.

Step:2 Input from the customer

The input given by the customer serves as the starting point for the design team. The customer gives all the specifications and standards that has to be considered while designing the

fixture. From the customer input the scope of the work is evaluated and the necessary processes like design, analysis, testing, GD&T etc. are carried out.

The common input given by the customer includes

• Functional requirement of the fixture(Hemming/checking/storage fixture)
• Preferred standard components.(Eg. ABB, NAAMS, ZYTRAn etc.)
• Ergo data for the operator (safety zone, loading unloading height etc)
• Layout of the assembly line.
• Car products(3D, 2D CAD files, PLP points, clamp plan, risers etc.)
• Weld study (Type and number of welds, type of gun etc.)
• Standard detailing templates.

Step:3 Percentage Completion Criteria

It is the criteria used in design and dispatch phases of the BIW fixture.It is used to check the progress of the project based on the percentage of work completed.

For example

Input and concept design - 0-25%

Concept approval and simulation - 25-40%

Design finalization and detailing - 40-85%

Testing and dispatch - 85-100%

Step:4 Design Output

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

There are two types of tools

Unitized tools

They have multiple units on a common base. They are represented in two kinds of sheets.

Layout sheet- It is a detailed drawing of individual units including all the components.

Key sheet- it is an index of units and their placement on the tool base.

Non-unitized tools

These are stand alone units and are detailed completely on a layout sheet.

2. What are the inputs required from the customer to start designing a Fixture?

INPUTES FROM CUSTOMER:

Customer opinion at this stage serves to define what is a winning product from the customer's perspective.The objestive is to gather a compelete set of customer wants and needs.The customer inputs are:

• Functional requirements.
• preferred standard components.
• car products.
• layout.
• Ergo data.
• weld study.
• standard detailing templetes.

Functional requirement

It defines the usage of the fixture. It could be used for welding, Hemming or Checking fixture. Depending on this the design considerations are taken in to account while designing the

fixture.

Preffered Standards

The standard pre-available parts are frequently used in fixture design. These standard parts saves our project time and money. These are the standard for fixture design parts ABB,

NAAMS, TUNKERS, ZYTRAN, DESTACO.The standard parts like riser. L-Blocks Retainers,Clamps, Cylinders, Switches, Sensors etc. can be used if they meet the requirements

Car Products

• GD & T

Geometric dimensioning & Tolerance of the part for which the fixture have to be designed. GD & T provides information about Locating pins, Rest, Clamp, Dumps and slides information of

each station and Sequence & opening of clamps, Dumps and slide stroke information.

• Part List

This is the list of part which are going to assembled in the fixture. It includes information about the part name, Part number,Tooling revision, Part thickness etc.

• Cad files of part

The 3D model file of the car part designe by using modelling software is given from the customer.

• Clamp plan

This is the clamping plan of the part whicle doing the operation. We can not change th eclamp plan without the permission of the customer. Itis very important input from the customer. It

provides location of pins, Rest, Clamps, Dumps etc.

• Product assembly process sheet

It gives detail process of the completion of the part from scratch to the finished product assembly.

• Layout

Layout gives information about Flow of parts, Station pitch, Robot stations, Tool changers, Tip dressers, Platform height, Sub asselmbly links & loading/Unloading sequence.

• Ergo Data

It is the study of human behaviour & movements during the assembly work. It provides data regarding loading and unloading height, working safety zone of the operator etc.

• Weld study

This gives the information of the type of weld gun required which also depends on the size and thickness of the part etc. It also gives details of the weld matrix and the weld point

positions. The geo weld point ensures the geometry of the assembly and the Re-spot weld points adds strength to the already welded point.

• Standard detailing templates

Every customer have their standard of detailing & the templates which are used for 2D drawing & detailing.

3. What is the input we get from "Car Products"?

GD&T

GD&T provides information and also help to calculate the clearances for locating pins, rest, clamp, damp & slide unit information of each station Also includes the information of sequence

of openings of clamps, dumps & slide stroke information. GD&T is also essential for stack up analysis.

Parts list

It gives the lists of parts which are needed the fixture assembly. The list contains the information of part number, part name, quantity, revision of fixture, part thickness, etc. It helps the

operator to indentify and assemble the parts correctly.

CAD files

The 3D model of the car parts is provided by the customer. This helps the designers to start fixture design process and do the further developments. The 3D cad files could be in the format

of step file (stp) or IGES file based on the requirement. The CAD files are used in the fixture assembly.

Clamp plan

Clamp plan provides the information of location of pins, Rest units, clamp unit, dump etc. It is the important input from customer. Any changes in the clamp plan must be done with proper

communication and consent of the customer.

Product assembly process sheet

It gives the details about the stages wise assembly process like how the parts move from one assembly process to other after the completion of joining process.

4. What is the Clamp plan?

A clamp is a device which is used to hold or secure objects tightly together to prevent movement during the fixture operation.

Functions of a clamp

• A clamp must hold the workpiece rigidly at the desired position.
• The clamp must be fast acting and clamp the workpiece in minimum time.
• The clamp must be able to resist forces and vibration.
• No scratch marks should be left on the workpiece.

Clamp plan

The clamp plan provides the information of location of pins, rest, clamp units, Dump etc. The customer gives the location where the clamps can be located based on the design intent of the

part so the position of the clamp should not be changed without commmunicating to the customer. This plan gives the exact position of the camping units by mentioning a co-ordinates the

particular position.

This is the clamping plan of the part while doing the operation.We cannot change the clamplan without permission of the customer.It is the very important input from the customer.It provides location of pins,rest,clamps,dumps,etc.

A clamp is a force actuating mechanism of a fixture.The force exterted by the clamps hold a part securly in the fixture against all other external forces.Clamping surfaces are subjected to clamping forces for obtaining invariant location.Clamp plan is the clamping plan of the part while doing the operation.

The clamping plan of a part is the plan which defines the location of the clam while doing the operation to ensure the geometry of the assembly.It provides information regarding to the location of pins,rest,clamps ,dumps,etc.The coordiante is also mentioned in the clamp planso the design team can take the coordinates directly & start the designing of the fixture.

5. What is the purpose of a Layout?

It is defined as plan for the effective arrangement of facilities and resources for optimum utilization of machines, processing equipment and maintenance departments. The layout is laid

inorder to achieve the proper usage of Men, Materials, Machines in a plant.

Plant layout is a floor plan showing the arrangement and the design of machinery and equipment of a plant. A good plant layout enables the quickest flow of material, at the lowest cost

and with the minimum handling to the complete processing of the product, from the receipt of raw material to the shipment of finished product

It the position of objects like robots, Fixtures, Racks etc. It shows the zone of reacheability for the robot used for the fixtures it is also called as the swept area of the robot. It is decided

based on the space available for the fixture.

Layout marks the area required for flow of parts, Station pitch, Robot stations, Tool changers, Tip dressers, Platform height. It also provides details on the Sub assembly links, loading and

Unloading sequence for the various operations.

Purpose of a layout

• Show the flow of parts in the assembly line

• To show the Station arrangement and distance between them.

• Highlight the position of Robot stations

• Give details on accessories like tool changer and tip dresser and their changing location.

• Sub assembly links

• Loading and unloading sequence of the parts

• To show the Platform height and operator ergonomics.

Layout is the most effective physical arangement,either exsisting or in plans of industrial facilities i.e. arrangement of machines,processing equipments and service departments to achive greatest coordination and eficiency of 4m's(Men,Materials,Machines,and Methods) in a plant.

Plant layout is a floor plan for determining and arranging the designed machinary and equipment of plant wheather established or contemplated,in the best place,to permit the quickest flow of materials at the lowest cost and with the minimum handlingin processing the product,from the recipt of raw material to the shipment of finished product.

It shows all the objects of the manufacturing line like robots,fixtures,racks,etc. and also shows the reachablity of the robot to the fixture also called the swept area of the robot.It also shows the constraint of space or the space available for the fixture that we are designing.

Layout provides information about flow of parts,station pitch,robot stations,tool changers,tip dresser,platform height,sub assembly links & loading/unloading sequence.

6. What is Ergo data?

Ergo data is helpfull for where mannual operators work.This data gives the height of machine so that the operator is easy to work without bending.If the height is too short he has to bend and operate the machine which leads to back pain of the worker.

1.Ergonomics refer to study of human behaviour and movements.

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

Human factros and ergonomics is the application of pysological and pysological principles to the engineering design of products,processes, and systems.The goal of human factors is to reduce human error,increase productivity and enhance safety and comfort with aspecific focuson the intraction between the human and the things of intrest.

The final assembly of an automobile involves tasks of complex nature. These processes are on the least periority for automation.manual labour is best suited for assembly operations with the aid of minimal level of automation.All the processes have to be improved contineously in order to reduce the costs and increase productivity.

The workers attain various postures,exerts force and workds continouslyin cycle time to accomplish the assembly task.Working along automobile assembly linesis characterized by represntatives.

Ergo data is studied to identify and quantify ergonomics working postures that contributed to the serious developement of muscle skeletal injuries and thus investigated possible contributary their related causes.

7. What do you understand by Weld study?

It is study that gives the information on the type of weld gun required for welding a part and it depends on the size and thickness of the part etc. It also gives details of the weld matrix

and the weld point positions. The automatic or semi-automatic weld guns are used. MIG welding is usually applied for joining of structural aluminium components, extrusions, castings and

sheet upto 2 mm thick.

Selection of weld gun

It is based on the following factors

• Type of weld required.
• Number of spots to be done.
• Type of current(AC/DC) required.
• Patch of gun travel.

Weld study includes;

• weld gun detailes.
• weld matrix and weld points.

1.Geo weld points. ( ensures geometry of the assembly)

2.Re-spot weld points. ( adds strength to the already welded patrs)

weld gun detials gives which type of weld gun is used like tig welding,mig welding,plasma welding or mannual metal arc welding etc.,

Selection of weld gun

It is based on the following factors

• Type of weld required.
• Number of spots to be done.
• Type of current(AC/DC) required.
• Patch of gun travel.

weld points gives data of where the weld to be takes place .

Welding is predominantly used in automobile industries and requirements for fixtures that ease the welding process is a continous developement task in any industry.

Car body in white(BIW) is a complicated steel structure including 300-500 sheets with complex shape and are assembled by means of welding in a high rhytham through 55-77 robotic work stations.

The foremost step taken before starting the design of welding fixture is to arrive at the spot weld locations.The location and orientation of other critical units of the fixture including clamps,locators,etc.are decided based onthe weld spot distribution.The weld spot for front door inner pannel-side bracket assembly are located with respect to the body line of car

It includes the study of the weld gun( A portable device for semiautomatic welding of parts of various articles)which is going to be used for the operation depending on the size of the part,thickness of the part etc.

8. What are the criteria for percentage completion in the designing stage? Explain it in detail

The percentage complete criteria contain the current status of a task,expressed as the percentage of the task's duration that has been completed.you can enter percent complete or you can have project calculate it for you based on actual duration.

It consists planning of completionof total project how much days the project to complete.It is followed in desigining stages & despatch stages of the welding fixture.

It is followed in design stages & dispatch stages of the welding fixture.It ensures that how much task that we have decided to complete within the stipilated time is completeor not& how much of it is rest to complete & weather it is going to be complete or no in given time.

When a task is first created,the percent work complete is zero percent.If you enter actual value of th task,projet calculates percent workcomplete as follows;

percent work complete=(actual work/work)*100

In a typical biw fixture design we can consider the following criteria of percentage completion.

• Input of concept design - 0 to 25%

The design inputs from the customer & after studying those inputs the concept fixture designs are created.

• Concept approval & simulation check - 25 to 40%

The concept approval design from the customer after study of simulation.

• Design freezing & detailing - 40 to 85%

After the simulation result if no any changes are required then the design is freezed.After freezing the 2D drawing which is the detailing part is started.

• Check and final dispatch - 85 to 100%

After detailing the quality checking team start inspection of all the dat & it will dispatch to the customer if everything is okay.

9. Brief about "Output" in design?

Each manufacture shall establish and maintain procedures for defining and documenting design output in terms that allow an adequate evaloution of conformance to design input requirements. Design output procedures shall contain or make reference to acceptance criteria and shall ensure that those design outputs that are essential for the proper functioning of the device are identified. Design output shall be documented ,reviewed, and approved before release.The aproval including the date and signature of individuals approving the output,shall be documented.

The outputs of design and development shall be provided in a form that enables verification against the design and development input and shall be approved prior to release.

Design and development output shall

1. Meet the input requirements for design and development.
2. Provide approprate information for purchasing, production and for service provision.
3. Contain or reference product acceptance criteria
4. Specify the characteristics of the product that are essential for its safe and proper use.

A design output is a drawing or specification or manufacturing instruction.Design outputs describe all the components ,parts and pieces that go into your medical device.Design output describe all assemblies and sub assemblies for your product.

If you are tasked with assembling a fixture from scratch,all these documents that you would need -design outputs.

There are some tools which are multiple units on common base are called inutized tools .eg. Fixture consists of number of same base.

The design output is 3D models or 2D drawing of the tools.The tools are of two types:

• Utilized tools:(multiple units on a common plane) Require two types of drawing sheets.

1.keysheet-It shows the index of the unit & their placement on tool base.

2.layout sheet-It is the detailed drawing individual unit to include all their components.

• Non-utilized tools: Tools that can stand alone and can be detailed compeletly ona layout sheet.

The output should compile following point:

1.Approved standard part should be used wherever possible.

2.Design should be simple and economical as possible.

3.Design must comply with all safety and economic standard.

4.Design must provide for controlled and damage free handling of product.

5.Adequate error profing provision must be incorporated on each design by providing proximity switches,rough locators etc.

6.The weight of moving part must be kept ,minimum while maintaining maximum strength.

7.Frames and structures are to be simple and sturdy.

8.Design clearance and accesibility for rotine maintance & service.

9.Motion control must be considered on any moving component.

10.Design is responsible to validate all clamps and weld guns

10.What do you understand by structuring a design tree? How does it reduce errors during the design process?

Structuring a design tree implies to a process where all the assemblies & parts are named ina specific standard.Diffferent customers have their different set of standards to structure a design tree.

It is an important process which helps us to identify a specific part or assembly as to which project ,unit or tool it belong to.

This helps us to avoid the errors druing design sturdy,manufacturing,assembly,inspection,etc.

If the parts or assemblies are not properly or the design tree is not structures properly,It will create confusion to understand the design and may create major posssibilites of making an error.

Naming of a fixture or a u it or a part gives the information as which project or assembly or zone do they belong.

It helps us to indentify the quantity of items of same type or different types are bing used in assembly.

11. What are Units? Mention 5 types of units.

A unit is a device that has a specified function ,especially one forming a complex mechanism.The BIW fixture is the assembly of different units which are designed to fullfill different purpose.

The unit have the specified functions like resting the panel clamping the part locating the part etc.

Accroding to the 3-2-1 principle of fixture design the units are designed to locate and clamp the car panel to its specified podition un fixture while operation is going on.

TYPES OF UNITS USED IN BIW FIXTURE DESIGN:

1.FIXED PIN UNIT: It is non movable locating unit used for proper location of the part.

2.RETRACT PIN UNIT: It is movable locating unit.

3.ROUGH LOCATOR UNIT: It roughly guides the operator for locating the part.

4.REST UNIT: The panel is rest on this unit.

5.BASE UNIT: It is the unit on which all other units are mounted.

Rest unit

Rest unit is basically a unit where the component is tested,there is no upper clamp to it.theere is no force applied to it.There is no cylinder attached to 'usually it will have a riser, a blade

and few rest mylers.

Fixed pin unit

It is a non-movable locating unit. It is used to locate the part quickly and correctly.

Retract pin unit

It is a movable pin unit and it can be up and down by using a retracable pneumatic cylinders which can be retraced to a certain distance.

Rough Locators

Rough locators are used to help the operator to locate the workpieces in the automated process.

Base unit

A base unit is a unit where all the other units are assembled.

12.Describe Fixed Pin units & their purpose?

Fixed pin unit consits of risers, blade,block,shims or spacer,pin retainer & pin.

Raiser is a standard part which is used to rise up the height of the whole unit.Blades are plates mounted on the raiser.Other parts like cylinder,arms,etc. mounted on the blade.

Shims are the small part which comes with the thickness of 0.1mm,0.2mm,0.5mm etc.This will compensate the stackup tolerance which reflects at the planel holder part called Mylars.In fixed pin shims are used to adjust to translational motion.

Pin retainer will support the pin & locating pin which restricts movement of the car panel.

PURPOSE OF FIXED PIN UNIT:

Fixed pin unit is a unit designed to locate the car panel using pin.

Fixed pin unit is the part of the 3-2-1 principle .It restricts 6 degrees of freedom of the car panel.

It is necessary to have 2 pins to locate car panel.one pin must arrest 4 way( 4 translational) &and other must arrest 2 way ( 2 rotational)of a car panel.

13. What are the different parts of a fixed unit?

DIFFERENT PARTS OF FIXED UNIT:

Fixed pin unit consists of riser,blade,blocks ,shims or spacer,pin retainer & pin.

1.RISER: Riser is the standard part which is used to rise up the height of the whole unit.

2.BLADES: These plates mounted on the riser.Other parts like cylinder,arms,etc are mounted on the blade.

3.SHIMS: These are the small parts which comes with the thickness of 0.1mm.0.2mm,0.5mm etc.These will compensate the stackup tolerance which reflects at the panel holding part called mylars.We give tolerance to all the parts of the fixture.Due to this tolerance the mylars will either lift up or goes down from its defined position.If the mylars goes down from its defined position it willmake impression or dent on the panel.If mylars liftup then there will be a distotion due to welding stress.To adjust the mylars at its defined position we use shims so the panel won't deformed & also do not get any impression on it.

4.PIN RETAINER:It will support the pin.

5.LOCATING PIN: Typically,locating pins are used for controlled,fine tolerance positioning of workpiece. for eg. a pallet that is moved along one axsis,where the drive mechanism is not accurate and stable enough to place in a position sufficiently accurate to execute a particular process ,the use of locating pins may be the best solution.

There are several styles of pin head shapes.They serve different purposes and can be utilized in avariety of applications.

14. What is the purpose of making a Rest unit & describe its parts?

The rest unit are designed to rest/support the car panel by using NC blocks/mylars/Rest.

It is the simplest unit to design because it have less parts to design &the purpose is only resting of the car panel.

Because of this simplicity the rest unit is combined with other unit to reduce the cost of the overall project.

It can be combined with clamp unit to clamp as well as to rest the car panel.It can be combined with locating unit to locate as well as to rest the car panel.also locating,clamping & rest unit can be combined together in one unit to reduce cost.The combined locating,clamping & resting unit to reduce the cost.

1. RISER: Riser is the standard part which is used to rise up the height of the while unit.

2.BLADES: These are plates mounted on the riser, other parts like cylinder,arms etc,mounted on the blade.

3.SHIMS:These are the small parts which comes with the thickness of 0.2mm,0.1mm,0.5mm etc.These will compensate the stackup tolerance which reflects at the panel holding part called mylars.

Shims are used in one direction in rest unit which is up & down because it requires adjustment in height only.

4.NC BLOCKS/MYLARS/FINGERS:Mylars is the component which holds the panel while operation.These are placed from top side and bottom side also.The top side mylars are called clamping mylars and bottom side mylars are called resting mylars.Every clamping mylars have resting mylars.It don't allow deformation of the part due to welding stresses.

15.What are the basic fundamentals to design a Sensor unit?

Sensor is a device which detacts or measures a physical properties and records,indicates otherwise respont to it.

A unit is designed to sense car panel using electrical sensors is called sensor unit.The form the sensors is send to the PLC so the next process is executed by this signal.

The sensor is very sensitive & easily damagable part so sensor cover is provided to the snsor for safety purpose.

There are different types of sensors:

1. Proximity sensor.
2. Laser sensor.
3. Photo electric sensor.
4. Infrared sensor.

FUNDAMENTALS OF SENSOR UNIT:

1.Every loose pannel which are welded by tools shoiuld be sensed.

The assembly of the car panel consists of nuber of panels.The location of every panel is fixed.There are some locating units,claming unit,rest unit,etc, are provided for proper location & coperation.The sensor is attached in this unit to sense the part is loaded or not.If the part is not loaded the sensor will send negative signal to the PLC controller and operation will not start & vice versa.Hence every single loose part should have at least 1 sensor.

2.Each panelshould be sensed by 1 to 2 sensors depends on the size of panel,preffered to be in diagonal opposite ends of panel.

Sensor is used to sense the part is loaded or not & starts the operation by sending the positive signal.But if the part is big in size then there will be 2 sensors required because the part will be loaded in correct position at one end and will be not positioned correctly at other end & due to which the assembly will not be okay part & gets rejected at QC check stage.Hence to neglate these kinds of suitations the part should be snsed by 1 or 2 sensor depending on its size for proper assembly.

3.Every sensor should be mounted in a three directional adjustable way in genral.

senseor can be adjusted to the particular distance from the panel by using the 3 directional adjustable way.If we use proximity sensor it have range 5 to 10 mm to sense part & for laser sensor the range increases.

16.What is a Rough locator unit & what are the basic fundamentals to consider while

designing it?

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

the above figure shows that the rough loxator in combined unit of clamping

and locating.

It can be called as fool proofing method also.because du to the rough locator part cannot be located in correct position.The rough locators are set accroding to the respective pannel hence part can only be loaded in defined direction and orientation.

FUNDAMENTALS OF ROUGH LOCATOR DESIGN:

1.Rough locators should be placed at the edges of the car panel,which it has to guide.

2.Rough locator has to be placed at the same angle of the car part edge with a minimum distance of 2-5mm from the edge of the car part.

3.Rough locator should guide the panel in the pin arresting direction.

4.Rough locator should start guide the panel before 10-15mm to start of the pin engagement.

5.Rough locator should be designed with entry angle for the car panel.Generally it ranges between 30-45 degree.

6.Rough locator should be designed with two slots to mount the easy adjustments.

7.The slots should be in the direction of car part guiding.

17.What is a Base unit and describe it's parts?

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 is the fundamental component of the fixture because all other components are mounted over it.so every fixture have base unit.The base unit design is different accroding to the panel,design of clamp system,location system etc.

Parts included in the base plate are:

1. FLOOR PLATE: It is the plate which join the fixture to the floor by using some nut bolts.This plate surface is machined for maintaining the horizontal position of the fixture.
2. WELD BARS & PEDESTAL: Pedestal is the base or support on which the fixture is mounted.

EYEBOLT: An eyebolt is a bolt with a loop at one end.They are used to firmly attach a securing eye to a structure,so that ropes or cables may then be tied to it.Machinary eyebolts are fully threaded and may have a collar,making them suitable for use with angular load upto 45 degrees .Eyebolt without a shoulder should not be used for angular loads.

Heavy forged eyebolts with a continuous eye may be forged with an integral shoulder ,allowing their use for heavy off-axsis loads.

4. MEASURING HOLE COVER: The base plate have some drills to mount various units like clamp, rest, pin.etc, & every drill have some coordinates to define the exact location of the hole.Due to irregular shape of the car panel the drilled hole coordinates are not like 110.0,150.0,but it like 110.62,150.84.The measuring hole is drilled over the base plate which have exact coordinates so that all other holes can take refrerence from it.The measuring hole depends on the base plate.These holes are covered by using some plate to protect against dust,damage,etc.

5.VALVE BOX & TRUNKING CHANNEL:The valve box is the box which includes different solinoid valves.The pnumatic parts of the fixture & protects them from damaging while operation is in process.

6.BASE PLATE: Base plate is heavy plate of large thickness because it carries all the weight of the mounted parts, so it must be able to bear the load.Base plate is machined to maintain the parelleity within the tolerance .It also consists some drilled holesto mount the different units over it.

18.What is a Dump Unit and what are its functions?

When we have some geometrical constrains then we cannot mount normal units like clamp unit,pin unit etc,In this case dump unit is used.

Dump unit is the complec unit to design due to space constraint there is a less space is available & have to adjust all the parts in available space.

It consists of dump cylinder to perform the operatiomn of clamping & unclamping of car panel.

19.What is a Slide unit? Mention where Slide units are commonly used.

Slide units are positioning units whichnar used to position the fixture,weld gun,units, robots into position for futher operations.Slide units can be classified into two types on the base of the type of guide ways used as:

1.Hardened guide ways.

2.LM guide way.

Slide units classified into three types based on prime mover used:

1.Manual slides.

2.hydraulic/pnumatic slides.

3.CNC slides.

It may also be classified depending on application as

Horizontal slide

vertical slide

Angular slide

GUIDELINES TO DESIGN THE SLIDE UNIT:

1.LM guide ways are preffered over hardened guideways due to least coefficient of friction.

2.Slide unit essentially contains of LM guides,liner cylinder,front & rear shock absorber,two proximity switches for sensing the twoo end positions bellows or protection cover for rails.

3.Cengter trunion /rear clevis mounted cylinder are ideally use for slide unit application as thios allows for some float to take up misalligment.

4.Reverse stroke of 10mm to be considered in both forward and retract condition.

5.Cylinders and lm guides to be validates for load and stroke.

6.LM guide rail length should be standard and should be more than the actual stroke.

7.Mechanical hard stop to be considered for both extended &mnbubhunkhbj retracted condition.

8.Shock absorber should be use for both extended and retracted condition to reduce impact load.

9.The two end limits to be sensed externally by a proximity switch.

10.The shock absorber should be mounted such that it is perpenducular to the pivot at mid stroke or within +/-5 degree.

Slide unit is used when we have some space constraints.so we don't have space to design different special units & to assemble it.In those case we use slide unit.