Week 3:- BiW Fixture Design Methodologies Challenges

1. What is design methodology?

Answer:

DESIGN METHODOLOGY

• Design methodology describes the steps followed during the concept desiging stages of fixture design.

• It includes:

1. Purchase order
2. Inputs from customer
3. Percentage completion criteria
4. Design Output

Purchase order(PO):

• It is the order from the customer end for the starting of the work.
• A purchase order (PO) is a commercial document and first official offer issued by a buyer to a seller indicating types, quantities, and agreed prices for products or services.
• It is used to control the purchasing of products and services from external suppliers.
• It is an essential part of enterprise resource planning system.
• Purchase orders allow buyers to clearly and explicitly communicate their intentions with sellers.

Inputs from customers:

• Inputs from customers are the collection of data given by the customer to the seller that includes standards, recquirements, layouts, etc.,

• Functional requirements - The purpose of functions of the fixture will be given as input from the customer like what are the function the fixture is going to do such as welding,riveting,gluing,etc.,
• Preferred standard components - All companies follow their own standards. Employing standards during the design and manufacturing as per the company norms will reduce the time and cost of manufacturing the product. Standard parts from the used fixture can be used in the new fixture which reduces the cost and time.
• Car products - Inputs that we can get from the car products are the GD&T, part list, CAD files of car parts,clamp plan.etc.,
• Layout - It provides an overall idea about the assembly process and its path.It provides information of flow of parts, pitch robot stations, tool changers, tip dressers, sub-assembly links,etc.,
• Ergo data - It provides information where manual operating is required like the position of the worker and the distance between the worker and the machine. It is given for providing better ergonomics during fixture design.
• Weld study - It gives details about the weld study for the gun that we are going to use for the welding in the fixture. It provides the no of weld and their positions i.e. it includes weld gun details, weld matrix and weld points.
• Standard detailing templates - It provides the detailing templates for 2D cad drawings as per the customer standard.

Percentage completion criteria:

• It is followed in the designing and dispatch stages of the welding fixtures. It gives the current status of the project and the upcoming steps.

Input and concept design - 0 to 25%

Concept approval and simulation check - 25 to 40%

Design freezing and detailing - 40 to 85%

Check and final dispatch - 85 to 100%

Design output:

• The output is the 3D models and 2D drawings of the tools.
• Unitized tools: It has multiple units on a common base which requires 2 types of drawing,

1. Key sheet - an index of units and their placements on the tool base.
2. Layout sheets - a detailed drawing of individual units with all components.

• Non-unitized tools: Tools that can stand alone and can be detailed completely with the layout sheet itself.

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

Answer:

INPUTS REQUIRED FROM CUSTOMER:

• Inputs from customers are the collection of data given by the customer to the seller that includes standards, recquirements, layouts, etc.,
• The various inputs required are given below,

• Inputs required are given as:

1. Functional requirements
2. preferred standard components
3. car products
4. Layout
5. Ergo data
6. Weld study
7. Standard detailing templates

1. Functional requirements:

• It is one of the basic requirement neede from the customer end to start the design process.
• The purpose of functions of the fixture will be given as input from the customer like what are the function the fixture is going to do such as welding,riveting,gluing,etc.,

2. Preferred standard components:

• All companies follow their own standards. Standards are basically the most common parts or product that are frequently used and can fixed in many fixture as well. This reduces the need to manufacture the part again and again.
• Employing standards during the design and manufacturing as per the company norms will reduce the time and cost of manufacturing the product.
• Standard parts from the used fixture can be used in the new fixture which reduces the cost and time.
• Some of the standard components used in BIW are:

-Standards like ABB, NAAMS (North American Association for Mechanical Standards), DESTACO, ZYTRAN, TUNKERS.

-Standard parts like risers, L-blocks, retainers,pins,etc.,

-Components such as clamps, stands, switches,etc.,

-Weld guns, tip dresser, tool changers,etc., Tip dressers are used to sharpen the tip of various gun used in the fixture

3. Car products:

• Inputs that we can get from the car products are the GD&T, part list, CAD files of car parts,clamp plan.etc.,
• GD&T- Provides information of locating pins,clamps,rest, damp and slide units.
• Part list - gives the list of parts that are going to be assembled in the fixture. It gives information of part number, part name, revision of parts,part thickness,etc.,
• Clamp plan- provides information of location of pins, clamp units, rest units,damp units. The clamp plan/ position should not be changed without the knowledge of the customer.
• 3D CAD file- The 3D car model file will be given by the customer which is used as the reference for designing the fixture. It is provide in the format of step file(stp) or IGES file.
• Product asssembly process sheet- It gives the information of stage wise assembly process like how parts move from one station to another in order to complete the assembly.

4. Layout:

• It provides an overall idea about the assembly process and its path.
• It provides information of,

1. Flow of parts
2. Station pitch
3. Robot stations
4. Tool changers
5. Tip dressers
6. Sub-assembly links
7. Platform heights
8. Loading and unloading heights,etc.,

5. Ergo data:

• The inputs of ergo data is mostly provided incase of manually operated fixtires.
• It provides information where manual operating is required like the position of the worker and the distance between the worker and the machine.
• It is given for providing better ergonomics during fixture design.
• It is mainly used to make the operator comfortable which lead to efficiency in cycle time and production.

6. Weld study:

• It gives details about the weld study for the gun that we are going to use for the welding in the fixture.
• It provides the no of weld and their positions i.e. it includes weld gun details, weld matrix and weld points.

7. Standard detailing templates:

• It provides the detailing templates for 2D cad drawings as per the customer standard.So the manufacturer has to follow those detailing standards.

3. What is the input we get from car products?

Answer:

Inputs that we can get from the car products are:

1. GD&T
2. Parts list
3. CAD files of car parts
4. Clamp plan
5. Product assembly process sheet

1. GD&T (Geometry dimension& Tolerancing):

• Provides information of locating pins,clamps,rest, damp and slide units.
• Also includes information of sequence of openings of clamps, dumps and slide stroke information.

2. Parts list:

• Gives the list of parts that are going to be assembled in the fixture.
• It gives information of part number, part name, revision of parts,part thickness,etc.,

3. Clamp plan:

It provides information of location of pins, clamp units, rest units,damp units. The clamp plan/ position should not be changed without the knowledge of the customer.

4. 3D CAD file:

• The 3D car model file will be given by the customer which is used as the reference for designing the fixture.
• It is provide in the format of step file(stp) or IGES file.

5. Product asssembly process sheet:

• It gives detailed process of assembly from the scratch to the final finished product.
• It gives the information of stage wise assembly process like how parts move from one station to another in order to complete the assembly.
• Different parts in a unit are welded using geo weld first.
• The small products are welded first leaving some weld points to balance the assembly of further upcoming parts. Then the remaining parts are welded using Re-spot welding which finishes the product in a step by step procedure.

4. What is the clamp plan?

Answer:

CLAMP

• A clamp is a device which holds the part at its location by exerting some forces on it.
• The force exerted by the clamp hold the part securely in the fixture against all other external forces applied on the fixture.
• Clamping surfaces are subjected to clamping forces for obtaining invariant location.
• Functions of a clamp:

1. It must hold the part rigidly while undergoing operations.
2. It should not damage the workpiece when holding in the fixture.
3. The time required for loading/unloading the tool must be minimum as much as possible.i.e. clamping unit to be quick acting.
4. It must be positive when subjeted to vibration,chattered, heavy pressure,etc.,

CLAMP PLAN

• It provides information of location of pins, clamp units, rest units,damp units.
• It is the important input from the customer end.
• The clamp plan/ position should not be changed without the knowledge of the customer.
• It is allowed to change the design little bit here and there but the input design data about the clamp position or pin location must not be changed.
• In clamp plan there is clamp unit,pin unit and it is more detailed. It also gives the Y and Z coordinates from where the designing process of fixture can be started.
• The clamping plan of a part defines the location of the clamp while doing the operation to ensure the geometry of the assembly.
• The coordinates are also mentioned in the clamp plan which can be taken directly for the designing process.

5. What is the purpose of a layout?

Answer:

LAYOUT

• Layout is basically a layout of the entire assembly line to understand the process and the flow of work.
• It will give the information about the fixtures and robots that are going to work on it.
• In layout sheet the circle around the robot is called the trapped area of that particular robot.
• So this is the reachability of the robot and which is confined to the particular circle.

PURPOSE OF A LAYOUT

• Layout is the most effective physical arrangement either existing or in plans of industrial facilities i.e. arrangement of machines, processing equipments and service departments to achieve greatest coordination and efficiency 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 whether established in the best place, to permit the quickest flow of materials at the lowest cost and with minimum handling in processing product from the reciept of raw material to the shipment of finished product.

• It also shows the constraints of space or the space available for the fixture design.

• It provides information of,

1. Flow of parts
2. Station pitch
3. Robot stations
4. Tool changers
5. Tip dressers
6. Sub-assembly links
7. Platform heights
8. Loading and unloading heights,etc.,

6. What is ergo data?

Answer:

ERGO DATA & ERGONOMICS

• Ergo data is the data or input which gives the human interface engineering data, between the worker and the working environment.

ERGONOMICS

• It refers to the study of human behaviour and movements. It is also known as human engineering & human factors engineering.
• The main objective is to optimize the integration of man & machine so as to improve the productivity and accuracy.
• Ergonomics is designing for human use and optimize working & living condition.
• To enhance certain desirable human values such as safety , reduced fatigue and improved quality of life.
• Benefits of ergonomics:

1. Improved working condition
2. Reduced physical workload
3. Improved work postures
4. Reduced efforts of certain movements.
5. Better reading instrument displays, control of levers and other tools
6. Reduced unnecessary information recall efforts

ERGO DATA

• The inputs of ergo data is mostly provided incase of manually operated fixtires.
• It provides information where manual operating is required like the position of the worker and the distance between the worker and the machine.
• It is given for providing better ergonomics during fixture design.
• It gives the height of the machine which is used for the fixture design. If the height is too short the operator has to bend and work, which causes backpain. By using the given data the fixture is designed at optimum height for comfortable position of the worker.
• The main goal is to reduce human error, increase productivity and enhance safety and comfort with a specific focus on the interaction between the human and things of interest.

7. What do you understand by Weld study?

Answer:

WELD STUDY

• Weld study is the study of welding technique that is to be used. The study is icludes its temperature, weld gun used, gases used, type of current, places to be welded.
• If the spot welding is done the kind of electrodes used, number of spots,etc., come under the weld study of that particular component.
• It includes:

1. Weld gun details
2. Weld matrix and weld points
3. Geo weld points (ensures geometry of the assembly)
4. Re-spot weld points (provides strength to already welded parts)

Weld gun details:

• It gives details like type of weld gun used such as TIG welding, MIG welding, plasma welding, manual metal arc welding,etc.,
• It gives details of welding spots, temperature, weld gun approach,etc.,

Weld matrix and weld points:

• Weld points are basically where the welding is going to happen at which point and at what coordinate it is welded.

Geo weld points & Re-spot weld points:

• Welding is predominantly used in automobile industries requirements for fixtures that ease the welding process is a continuous development task in any industry.
• A typical BIW has more than 500 weld spots on it.
• The data of weld matrix and weld point is given in the form of spheres.i.e.red and green spheres. where th welding is going to happen.
• Geo spots are red in colour and re-spots are green in colour.
• All the red spheres are going to done in geo stationary
• In the re-spot station where the green welding is going to be happen. So this happens when one component is going to be attached with this particular component and in other station, the other component get attached.

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

Answer:

The criteria for percentage completion in the designing stage:

• It is followed in the designing and dispatch stages of the welding fixtures.
• It is followed to trace the project whether it matches the commited date given to the customer for handovering the project.
• It also helps us to identify at which stage the project is currently going on like how much project is completed and the further stages that are in pending to complete it. Thus it helps us to complete the project on commited date and time.
• It is divided into 4 stages to identify the percentage of completion of work.
• It gives the current status of the project and the upcoming steps

-Input and concept design

-Concept approval and simulation check

-Design freezing and detailing

-Check and final dispatch

1. Input and concept design:

• It is the initial stage of the project.
• It includes 0-25% work completed of the project.
• Input data is provided by the customer like like functional requirement, company standards,etc., After studying these data the concept design of the fixture is generated.

2. Concept approval and simulation check:

• After the concept design and simulation checking is done it is send to the customer for approval.
• The customer after analyzing those data and simulations the approval is given. Incase of any changes preferred by the customer the design has to be re-worked and again send for approval by the designer.
• It includes 25-40% work completed of the project in design.

3. Design freezing and detailing:

• Freezing means finalizing concept design.
• It involves design freezing after approval of concept design.
• In next step detailing is done as per customer standard templates.
• It includes almost 40-80% work compled in the designing stage.

4. check and final dispatch:

• After detailing, the quality checking team starts the inspection of all the dates to the dispatch of the design whether it is ok as per the customer standards or not.
• If there is any error in drafting it will create issue or mistakes in manufacturing end.
• On completion of this stage 100% is achieved and finally the outcome is dispatched.
• Thus the percentage completion criteria helps us to know where we stand in the project or where we are.

9. Brief about "OUTPUT" in design?

Answer:

DESIGN OUTPUT:

• It is the data given to the customer after completion of the design stage.
• The output is the 3D models and 2D drawings of the tools.
• In fixture element design, the output contains detailed design of locators, design of clamps, design of supports, positions of locators, positions of clamps, positions of supports if any, types of locators, types of clamps, types of supports, claring forces and supports.
• There are 2 types of tools used:

1. Unitized tool
2. Non-unitized tool

Unitized tool:

• It has multiple units on a common base.
• For e.g. geo fixture, robot fixture, checking fixture, hemming station,etc.,
• It requires two types of drawing sheets:

a. Key sheet

b. Layout sheet

a. Key sheet:

• An index of units and their placements on the tool base.
• Key sheet shows placement and exact location of that particular unit on tool base and the exact position of tool base as well.
• It shows the orthogonal or isometric view of that entire component.

b. Layout sheet:

• It is the detailed drawing of individual units to include all of their components.
• It helps in CMM inspection of fixture.

Non-unitized tool:

• They are the tools that can stand alone and can be completely detailed on a layout sheet.
• The output should compile the following points,

1. Approved standard parts should be used wherever possible. This saves a lot of time, effort and cost.
2. Design should be as simple and economical as possible. If the geometry is complex then the fixture design is also complex but the approach is trying to design as simple as possible.
3. Design must comply with all safety and ergonomic standards as per the company.
4. Design must provide for controlled and damage free handling of product. It should not damage other parts.
5. Adequate error proofing provision must be incorporated in every design by providing proximity switches, rough locators, etc., Proximity switches are sensors that ensures the presence of all parts in the fixture whereas rough locators work as poka yoke to guide the entire panel orientation.
6. The weight of the moving part should be as minimum as possible without compromising in its strength. There should be balance in both weight and strength.
7. Frames and structures are to be simle and sturdy.
8. Design clearance and accessibility for periodic maintenance and service. It shoul be easily accessible for maintenance.
9. Motion control must be considered on any moving component. It shoul be employed in slider, clamp arm so that it would not allow any vibration and stays on its place by using hard stopper,shock absorber,etc.,
10. Designer is responsible to validate all clamps and welding guns. Hence the clamps and guns should perform their function without fail.

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

Answer:

STRUCTURING A DESIGN TREE

• It is the process of naming all the assemblies and parts in the specific standards. Different customers have 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 or assembly it belongs to.
• This helps us to avoid the errors during design study, manufacturing, assembly,inspection, etc.,
• If the parts or assemblies are not properly or the design tree is not structured properly, it will create confusion in understanding the design and assembly which may lead to errors.
• Naming of a fixture or a unit or a part gives their place in the specific project or assembly or zone.
• it helps us to identify the quantity of items of same type or different types that are being used in the assembly.

• The design tree given in the figure has the designed parts at top and the standard parts at bottom.
• The blue highlighted number is H1L-T9A-RRFRA-JG3-00-00-00

H1L-T9A - The project name

RRFRA - Panel name

JG3 - Jig no.3

00 - unit no.

00 - Part no.

00 - Component no.

• Under the product there are main assemblies, sub-assemblies, child part, standard parts,etc., these parts are provided with specific no.,zone,etc., to identify easily.

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

Answer:

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 has the specified functions like resting the panel, clamping the part, locating the part,etc.,
• According to the 3-2-1 principle of fixture design the units are dsigned to locate and clamp the car panel to its specified position in fixture while operation is going on.

Fig shows: Clamping unit

Types of units used in BIW fixture design:

1. Fixed pin unit- It is non-movable locating unit 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.

12. Describe fixed units and their purpose?

Answer:

FIXED PIN UNIT

• It is designed to locate car panel using pins.
• It is already fixed and it cannot move up and down.
• Below are the different parts of pin unit in general:

1. Pin
2. Pin retainer
3. Shims/Spacers
4. Block
5. Blade/Adoptor plate

• Every pin unit will have 2 directional shims.
• The block is used to mount the entire pin unit.
• Shims are used to avoid stackup tolerance while assembling entire component.Shims come in pack of sizes like 0.1,0.2& 0.5cm.

Fig shows: Shims

Purpose of fixed pin unit:

• Pin is most important part of fixture & used to restrict roatational as well as translational degrees of freedom of that particular component.
• Purpose of fixed pin unit is to fix the panel translation motion along two axis and to prevent rotation of panel in the axis of panel.

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

Answer:

DIFFERENT PARTS OF A FIXED UNIT

The different parts of a fixed unit are:

1. Locating pin
2. Pin retainer
3. Shims
4. Blade
5. Riser

Locating pins:

• Locating pins are used for controlled, fine tolerance positioning of a work piece.
• Usually two locating pins are enough to properly locate the workpiece on one plane.
• There are dozens of styles of locating pins that can be utilized in a design.
• Locating pins are a great way to make sure the parts that are putting together fit the way we want them to fit.
• Drill two holes opposite each other in each part, install a cylindrical locating pin, parts are aligned exactly the way we want.

Risers:

• Riser is a structure generally used to mount the toggle clamp and rest, clamp mylars and location pin.
• It is not necessary to have one riser where all the parts of clamp or rest or location units are mounted.
• Generally risers are either made of plate fabrication or plate and tube welding together or from single gas cut plate.
• These are generally manufactured to give height to the assembly.

Blade:

• Blades are the plates attached to the riser. Parts like cylinders, arms,etc., are mounted on the blade.
• Chamfer is done to straighten the blade.

Shims:

• Metal shims are used to finely adjust the location of how the fixture holds the part so that it is welded together within the dimensions set for the product to work well.
• A pack of thin metal shim is placed between two components in the fixture.

Fig shows: Shims

Pin retainers:

• A pin retainer is a part which holds the pin in position, the pin retainer can be either a make part or a standard part also.
• Pin retainer is used to hold the l;ocating pins firmly.

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

Answer:

REST UNIT

• Rest unit is designed to support car panel using Myler/NC block/rest component is rested only, no upper clamp or force applied there.
• The rest unit are designed to rest/ support the car panel by using NC blcoks/Mylars/rest.
• It is the simplest unit to design because it have less parts to design & the purpose is only resting of the panel.
• Because of this simplicity the rest unit is combined with other unit to reduce the cost of overall project.
• It can be combined with clamp unit as well 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.

Simple support unit Combined locating,clamping & resting unit

Parts of the rest unit:

1. Riser :

• Riser is a structure generally used to mount the toggle clamp and rest, clamp mylars and location pin.
• It is not necessary to have one riser where all the parts of clamp or rest or location units are mounted.
• Generally risers are either made of plate fabrication or plate and tube welding together or from single gas cut plate.
• These are generally manufactured to give height to the assembly.

2. Blades:

• Blades are the plates attached to the riser. Parts like cylinders, arms,etc., are mounted on the blade.
• Chamfer is done to straighten the blade.

3. NC blocks/Mylars:

• Mylars are the part which are holding the panel from the top & bottom. It is a jaw type, during welding it wont deform from its position.
• It is also known as fingers. It wont allow deformation of the part due to welding stresses.
• Mylars are of 2 types,

1. Clamping mylars
2. Resting mylars

• Only resting mylars are seen in resting unit.The panel which rests on the part is known as resting mylars.

4. Shims/Spacers:

• Metal shims are used to finely adjust the location of how the fixture holds the part so that it is welded together within the dimensions set for the product to work well.
• A pack of thin metal shim is placed between two components in the fixture.

Fig shows: Shims

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

Answer:

SENSOR UNIT

• A sensor is a device that measures physical input from its environment and converts it into data that can be interpreted by either a human or a machine.
• Most sensors are electronic(the data is converted into electronic data), but some are more simple such as glass thermometer, which presents visual data.
• Peope use sensors to measure temperature, gauge distance, detect smoke, regulate pressure and other uses.
• A unit is designed to sense car panel using electrical sensor is called sensor unit. The signal from the sensor 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 sensor for safety purpose.
• There are different types of sensors like:

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

Fig shows: Welding and assembly sensors

Fundamentals of sensor unit:

1. Every Loose panel which are being welded by tools should be sensed.

2.The assembly of the car panel consists of nmber of panels. The location of every panel is fixed.There are some locating units, clamping unit, rest unit,etc., are provided for proper location and operation. To conform the presence of the part sensors are attached to the units.

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

4. Sensor is used to sense the part is loaded or not & starts the operation by sending the positive signal. But if the is big in size then there will be 2 sensors required to prevent mistakes in positioning the part.

5. Every sensor should be mounted in a three directional adjustable way in general.

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

7. Sensor manufacturers are IFM, Perperl-Funchs, OMRON,etc.,

16. What is a rough locator unit & what re the basic fundamentals to consider while designing it?

Answer:

ROUGH LOCATOR

• Rough locators are elements that guide the operator while loading panels onto the fixture and ensure a fool-proof assembly.
• It is used as a fool proofing method, because the rough locator part cannot be located in correct position.
• The rough locators are set according to the respective panel.
• Hence the part can only be loaded in defined direction and orientation.

Fig shows: Combined rough locator with the clamping unit

Fundamentals of rough locators design:

1. Rough locators should be placed along the edges of the car panel which it has to guide.
2. Rough locator has to be placed at the angle as same as the angle of edges of the panel.
3. A minimum distance of 2.5 mm from the edge of car panel should be maintained.
4. It should guide the panel in the pin arresting direction.
5. It should start guiding the panel before 10-15 mm to start of the pin engagement.
6. It should be designed with entry angle for the car panel. Generally it ranges between 30-45 degree.
7. It should be designed with 2 slotsto mount the part on to the base unit and for easy adjustments.
8. The locators must be in the direction of car part guiding.

Answer:

BASE UNNIT

Fig shows: A fixed base unit

Parts of a base unit:

1. Valve box
2. Trunking channel
3. Measuring hole cover
4. Eye bolt
5. Pedestal
6. Floor plates

1. Valve box:

• Valve box is basically a box which supplies air to all pneumatic cylinders assembled in the fixture.
• It consists of one solenoid valve which is used to collect the air from the pneumatic cylinder to the valve box.

2. Trunking channel:

• Trunking channel is a kind of cable duct which helps to guide and protect the wirings/ tubes used in the fixtures.

3. Measuring hole cover:

• In the measuring hole cover, the co-ordinate points are engraved on it.
• The hole which mentions the coordinates gives the position placements of the particular unit.
• The measuring hole helps in CMM inspection & QC inspection.

4. Eye bolt:

• An eye bolt 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 cable may then be tied to it for lifting purpose.
• It is used to drag or lift the base unit while relocating.

5. Pedestal:

• Pedestal is a stand like structure where the entire unit of the base will be mounted.

6. Floor plates:

• Floor plates is used to mount the entir base with floor..
• Also, helps to achieve the flatness of the fixture.

18. What is a dump unit and what are its funstions?

Answer:

DUMP UNIT

• Dump unit is used where the component to be assembled has certain constraints. Here we have clamp unit, pin unit attached panel will be assembled. If we have certain constraint we cannot assemble in normal way.
• Dump unit is used in different ways. It has dump cylinder & complex design.
• It consists of dump cylinder to perform the operation of clamping & unclamping car panel.
• It can have more than one cylinder for such operations.
• The first cylinder dumps the assembly carrying clamp Mylars,pins and then this assembly performs required operation in this unit.
• One should make sure that in the open position, it is able to remove the panel.

Fig shows : Dump Unit

Functions of dump unit:

• Dumps units are used when we can not use normal units like clamp unit, pin unit unit,etc., Due to some space constraints. The designed parts should be small in size but can do their functions effectively.

19. What are slide units? Mention where slide units are comonly used?

Answer:

SLIDE UNITS

• Slide units are positioning units, which are used to position the car part or panel, units, weld gun, robots for further operations.

• slide units may be classified into two types based on the type of guide ways,

1. Hardened guide way
2. LM guide way

• Slide units may be further classified into 3 types based on prime mover,

1. Manual slides
2. Hydraulic/pneumatic slides
3. CNC slides

• It may be further classified depending upon the application as,

1. Horizontal slide unit
2. vertical slide unit
3. Angular slide unit

Basic fundamentals of slide unit design:

• Reverse stroke of 10 mm to be considered in both forward & retracted condition.
• Cylinder & LM guides to be validated for load & stroke.
• Master guide way should be constrained & the subsidiary guide way to be free.
• Mechanical hard stop to be considered for both extended and retracted condition.
• LM guide ways are preferred over hardened guide ways due to least co-efficient of friction.
• Slide unit essentially consists of LM guides, linear cylinder, front& rear stoppers, front & rear shock absorber, two proximity switches/reed switches for sensing the 2 end position, belows or protecton cover for rails.
• Center trunnion/rear clevis mounted cylinders are ideally used for slide unit application as this allows for some float to take up mis-alignment.
• LM guide rail length shoulld be standard and should be more than the actual stroke.
• The shock absorber should be mounted such that it is perpendicular to the pivot at mid stroke or within +/- 5 degree.