Week 3:- BiW Fixture Design Methodologies Challenges

Q1.

Design Methodology:

Design Methodology is nothing but the steps followed during the concept designing stages of fixture design.

Design Methodology is divided into four Sub categories:

• Purchase Order
• Inputs from Customer
• Percentage Completion Criteria
• Design Output

Purchase Order:

A purchase order 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.Purchase orders can be an essential part of enterprise resource planning system orders. Companies use purchase orders for several reasons. Purchase orders allow buyers to clearly and explicitly communicate their intentions to sellers. They may also help a purchasing agent to manage incoming orders and pending orders. Sellers are also protected by pos in case of a buyer's refusal to pay for goods or services.

Purchase orders provide benefits in that they streamline the purchasing process to a standard procedure. Commercial lenders or financial institutions may provide financial assistance on the basis of purchase orders.

Inputs from Customer:

Inputs from customer basically are the data given by the customer like requirements , standards , layouts etc.

• Functional requirements:The purpose of the function of the fixture will be given as input from the customers like what are the function the fixture is going to do i.e. Welding, riveting, gluing, or whether it is a checking fixture,etc.
• Preferred standards:As we know different companies follow different standards .we will be following the standards, followed by the customers. By following the standards in the time of designing and manufacturing of parts we will be saving the time and cost which will be automatically minimizing the time of the projects. As per the standard parts, it can be easily replaced from the used fixture to the new fixture which reduces cost.
• Car products:The inputs we get from car products are GD&T, parts list, CAD files of car part, Clamp plan ,Produce assembly process sheet.
• Layout:Lay out shows the entire assembly plan to understand the process. Layout provides information of flow of parts, station pitch, robot stations, accessories like tool changes and tip dressers, sub assembly links, platform height, loading and unloading sequence heights.
• Ergo data:As same as preferred standards, different companies for the different standards of ergo data. We have to follow the customary standards of ergo data. The inputs of Ergo data will be given by the customer mostly in case of manually operated fixtures. The Ergo data is mainly used to make the operator comfortable which may lead to improve the efficiency in cycle time and production. Data provides inputs like platform height, maximum and minimum treat from operator to fixture, maximum and minimum height of the fixture, whether the child parts or assemblies are visible while clamping for loading and unloading. Also provides information like loading height, working safety zone of operator,etc.
• Weld study:Weld Study is the important inputs given by the customer. It gives details about the study of particular gun that we use for welding. Also like the number of weld, weld position of the components will be given. In short weld study includes welding gun details, weld Matrix and weld points.
• Standard detailing templates: These inputs include the detailing templates of 2D cad drawing as per the customer standards.So, we have to follow the detailing templates as per the customer standards

Percentage Completion Criteria:

It is followed in designing stages and dispatch stages of welding fixtures. It helps to track or identify how much task is completed and how much to go further for completing a fixture.

Input send 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%.

The above-mentioned percentage of the percentages of state wise completion criteria of the projects.

Design Output:

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

• Unitized tools: multiple units on a common base. It requires two types of drawing:
  • Key sheet: an index of units and their placements on the tool base.
  • Layout sheets: 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.

Hence, The design methodologies are explained in detail.

Q.2

Inputs required from the customer:

To start designing a fixture the following are the inputs required for designing a fixture.

• Functional requirements
• Preferred Standard Components
• Car Prodcts
• Layout
• Ergo Data
• Weld Study
• Standard detailing Templates.

Functional requirements:

The purpose of the function of the fixture will be given as input from the customers like what are the function the fixture is going to do i.e. Welding, riveting, gluing, or whether it is a checking fixture,etc.

It is one of the basic requirements to get from the customer to start designing a fixture.

Preferred standards:

As we know different companies follow different standards .we will be following the standards, followed by the customers. By following the standards in the time of designing and manufacturing of parts we will be saving the time and cost which will be automatically minimizing the time of the projects. As per the standard parts, it can be easily replaced from the used fixture to the new fixture which reduces cost.

Some of the preferred standard components used in BIW ar Stated below:

• Standards like ABB,NAAMS(North American Association for Mechanical Standards),DESTACO,ZYTRAN,TUNKERS.
• Standard Parts like Risers,L-Blocks,Retainers,Pins.
• Components like Clamps,Cylinders,Slides,Switches,Sensors.
• Weld guns,Tip Dressers,Tool changers.Tip Dressers are used to sharpen the tip of the tools which are used in robots in various process.

Car Products:

The inputs we get from car products are: GD&T part list, Cad files of car part, Clamp plan, product assembly process sheet.

• GD&T: It provides information of 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.
• Part Lists: It gives the lists of parts which are going to be assembled inthe fixture. The list contains the information of part number, part name, revision of fixture, part thickness, etc
• Clamp plan: Clamp plan provides the information of location of pins, Rest units, clamp unit, dump etc. It is the important input from customer. The clamp plan/position should not be changed without the knowledge of customer
• 3D cad file: The 3D model of the car part will be given the customer. From that 3D model we will be developing our fixture design process. The 3D cad file will be in the format of step file (stp) or IGES file igs).
• Product assembly process sheet: It gives the information of stage wise assembly process like how the parts move from one assembly process to other after the completion of joining process.

Layout:

Lay out shows the entire assembly plan to understand the process. Layout provides information of

• Flow of parts,
• Station pitch,
• Robot stations,
• Accessories like tool changes and tip dressers,
• Sub assembly links,
• Platform height,
• Loading and unloading sequence heights.

Ergo data:

As same as preferred standards, different companies for the different standards of ergo data. We have to follow the customary standards of ergo data. The inputs of Ergo data will be given by the customer mostly in case of manually operated fixtures. The Ergo data is mainly used to make the operator comfortable which may lead to improve the efficiency in cycle time and production. Data provides inputs like platform height, maximum and minimum treat from operator to fixture, maximum and minimum height of the fixture, whether the child parts or assemblies are visible while clamping for loading and unloading. Also provides information like loading height, working safety zone of operator,etc.

Weld study:

Weld Study is the important inputs given by the customer. It gives details about the study of particular gun that we use for welding.

Also like the number of weld, weld position of the components will be given. In short weld study includes welding gun details, weld Matrix and weld points.

Standard detailing templates:

These inputs include the detailing templates of 2D cad drawing as per the customer standards.So, we have to follow the detailing templates as per the customer standards.

Hence, the inputs from the customer to start the designing of the fixture are explained in detail.

Q.3

Inputs we get from car products include:

• GD&T
• Parts lists.
• 3D cad file.
• Clamp plan.
• Product assembly process sheet.

Geometry Dimension and Tolerancing:

It provides information of locating pins,rest,clamp,damp & Slide unit information of each sttation.

Also includes the information of sequence of openings of Clamps,dumps & slide stroke information.

Part List:

Part list gives thee information of parts in a unit.it consists of part number,part name which helps to ientify the part easily,number of parts required and its thickness.this list helps to check all the parts and its dimensions and required number of quantities.

CAD files of the car part:

CAD files of car parts gives the simulations of those 3D models and their analysis.It is also used throughout the engineering process from concptual design and layout of products through strength and dynamic analysis of assemblies to definition of manufacturing methods of components.

Clamp plan:

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

Q.4

Clamp :

A clamp is a fastening device used to hold objects tightly to together to prevent movement through the application of inward pressure.

Essential requirements of clamp :

1. The workpiece must be held rigid while undergoing operations.

2. Time required for loading & unloading the tool must be less.

3. when subjected to vibration, the clamping must be possitive.

4. the clamp must not damage the workpiece.

Clamp Plan :

• It provides the information of location of pins, test units etc.
• It is the important input from the customer.
• It gives the detail of exact position of camping units by mensioning co-ordinates

• In this, there is clamp unit, pin unit and it also gives exact location of Y and Z coordinates.

Q.5

Layout :

• It is layout of entire assembly line to understand the process and the flow of work
• Layout sheet will give you information about all the fixtures are placed the robots are going to work on it.
• In layout sheet, the circle around the robot is called trapped area of that perticular robot. This is basically reachability of the robot.

Layout provides information about

1. flow of parts.

2. Station pitch

3. robot stations

4. accessaries like tool changer and tip dressor

5. sub assembly link

Q.6

Ergo Data

It is the data which gives human factor engineering data beween the operator and his working environment.

Benifits of Ergonomics

• Improved working condition.
• Reduce physical workload
• Improved work postures
• Reduced efforts of certain movements
• Better reading instrument display
• Reduced unnecessary information recall efforts.

Ergonomics Guidelines

• Flexibility and adjustibility for viewing angle, access .
• Physical access for hands or tools
• prevent blind assembly
• eliminate obstructions in front of working area
• Standardised light colour
• locate lights as close to hand location as possible
• Design should not rely on operator for positioning
• ensure operations do not cause change in positioning of part
• avoid having to hold with second hand while loading

Q.7

Weld Study

A study of the welding technique that we are going to use,its temperature, type of current, type of gases used etc.

Weld study includes,

• Weld gun details
• Weld matrix and weld point
• Geo weld points

Weld gun details

It involves the study of gun like,

• Type of weld it does
• Number of spot it can weld
• temperature of the weld
• type of current
• approach of gun

Weld matrix and weld point

• Weld points are basically where the welding is going at which point at which co-ordinates is going to happen.

Q.8

the criteria for percentage completion in the designing stage

• It is followed in the designing stages and dispatch stages of welding fixture.
• It is also followed to trace the project whether it matches the committed date given to the customer
• It also helps to identify he stages in the projects like how much the project is completed and what are the further stages are pending.

It is divided into 4 stages

1. Input & concept design :-

This is initial stage of project. Input data provided by customer like functional requirement etc & after studying those inputs the concept of fixture design is created.

2. Concept approval & simulation check :-

As concept of fixture design is created & simulation checked it is sending for customer approval . Customer will study all simulations & give his approval.

3. Design freezing & detailing :-

This phase involves design freezing after approval of concept design freezing means finalizing concept design.

4. Check & final dispatch :-

After detailing the quality checking team starts inspection of all the date it will dispatch to the customer. If there is an error in drafting, it will create issue in manufacturing stage.

Q.9

Design output

It includes data to be given to customer after completion of design stage. the output is 3D models and 2D drawings of the tool.

There are two types of tools in fixture design

1. Unitized tool

In this, there are multiple units on common base , it require two types of sheets

• Key sheet - An index of units & their placement on the tool base. It allows placement and location of perticular unit on tool base.

• Layout sheet - A detailed drawing of individual unit to include all their units . It is detailed drawing of perticular tool where we are going detail of components.

2. Non unitised tool

These can stand alone & can be detailed on layout sheet.

The output should compile following points

• Approved standard parts should be used wherever possible
• Design should be as simple & economical as possible.
• Design must comply with all current safety & ergonomic standard.
• Design must provide for controlled & damage free handling of product.
• The weight of moving part must be kept minimum while maintaining maximum strength.
• Frames & structures are to be simple.
• Design clearances & accessibility for routine maintenance & service.
• Motion control must be considered on any moving component
• Designer is responsible to validate all clamps & welding guns. So that all clamps & guns should perform its function without fail.

Q.10

Structuring a design tree :-

A process where all the assemblies and parts are named in a specific standard. Different customers have different sets of standards and structure of design tree.

Every company, every customer has different standard of therir own structural design tree.

So they will be giving template on how the structuring and detailing of design done. And you have to follow that perticular designing or structuring of the tree.

Structuring a design tree is actually to avoid the errors, which might come during manufacturing assembly, or either in house inspection as well

Every part, every component should be named according to procedures

Naming a fixture or a unit or a part gives the information as to which project zone or assembly do they belong.

It can help us to identify the quantity of item of same types or different types that are being used in an assembly.

In design tree in which designed parts are at top & all standard parts are at bottom

Eg. H1L-T9A-RRFRA-JG3-00-00-00

• H1L - 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 assemblled child part standard parts, etc these all parts are provided with specific number, zone etc. to identify easily.

Q.11

Units :-

It is a device that has a specified function ,especially one forming art of complex mechanism. Multiple units are joined together in order to form a fixture and are attached to common base, which serves as a common support to the unit

Units are classified into two types

1.Unitised tools :-

These are basically tools which are art of multiple tools inside.

It is again further divided in two groups,

a. Simple Units - It include following units,

• Rest Unit - It is basically unit where the component is tested, there is no upper clamp to it.
• Fixed pin unit - It is basically unit which has a pin which is already fixed it cannot be moved
• Retract pin unit - It is opposite to fixture which csn be moved up and down by using pneumatic cylinder.
• Rough Locators - It is a part designed to guide the operator, to locate the car panel on the pins accordingly.
• Sensor unit - These are used in actually sensing whether the panel or perticular component is there or not.
• Base Unit - It is the unit designed to mount all other units

b. complex unit -

It is divided int two units

• Slide Unit - These are basically where the sliding mechanism is involved
• Dump Unit - It is basically like a conveyor where we assemble a component if we have pericular constraint.

2. Non Unitised tools :-

It is basically one unit itself, which dont have any processes functionaity just to keep component on it as a stable

Non unitised tools are:

• Stands
• Take out trolleys
• Conveyors
• Turn Tables
• Some gripper

Q.12

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.

• Pin
• Pin Retainer
• Shims/spacer
• Block
• Blade/Adopter plate.

Every pin unit have teo directional shims.the block is used to mount entire pin unit.

Shims are used to avoid stackup tolerance while assembling entire component.

Shims comes in pack of 0.1,0.2 & 0.5 cm.

Purpose of fixed pin unit :-

Pin s most important part of fixture & used to restrict rotational as well as translational degrees of freedom of that perticular component.

Purpose of fixed pin unit is to fix the panel's translational motion along two axis and to prevent rotation of panel in the axis of panel.

Q.13

Different Parts of Pin Units :-

The different parts of fixed unit are

• Locator Pin
• Pin retainer
• Shims
• Blades
• Riser

a.Locating Pins

These are used for controlled, fine tolerance positioning of workpiece. 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 utilised in design

b. Risers

It is a structure generally used to mount the toggle clamp and rest,clamp mylers and location pin.

It is not necessary to have one riser where all the parts of clamp or rest or location units are mounted.

c. Blade -

Blades are the plate attached to the riser. PArts like cylinder,arms etc are mounted on blades and champher is given to straighten the blade.

c. Shims -

Metal shims are used to finely adjust the location of how the fixture holds the product so that it is welded together within the dimensions set for the product to work well

d. Pin retainers -

It is a part which hold the pin in position, the pin retainer can be either make part or a standard part also . Pin retainers is used to hold the locating pin firmly.

Q.14

Rest Unit -

It is unit designed to support car panel using myler/NC block . It is the simplest unit to design because it has fewer parts to design & the purpose is only resting of the panel.

The different parts of rest unit are,

• NC blocks/Mylers
• Spacers
• Blade
• Risers

a. NC block/Mylers

These are the parts which are holding the panel from top to bottom.

Mylers afe of two types

1.Clamping mylers

2.Resting mylers

b. Risers

It is a structure generally used to mount the toggle clamp and rest,clamp mylers and location pin.

It is not necessary to have one riser where all the parts of clamp or rest are mounted

c. Spacer/Shims

Metal shims are used to finely adjust the location of how the fixture holds the product so that it is welded together within the dimensions set for the product to work well

d. Blade

Blades are the plate attached to riser .

Other parts like cylinder , arm etc mounted on the blade & champher is given to straighten the blade.

Q.15

Sensor Unit -

A sensor is a device that measures physical input from its environment and convert it into data that can be interpreted by either a human or a machine.

Most sensors are electronic , but some are most simple.

Types of sensors

1.Proximity sensor

2.Photo electric sensor

3.Laser sensor.

Proximity sensor -

It is a non contact sensor that detects the presence of an object when the target enters the sensor's field

Depending on the type of proximity sensor, sound, light, infrared radiation may be utilised by the sensor to detect the target.

Photoelectric Sensor

It detects the object,changes in surface condition,and other items through a variety of optical properties

It consist of an emiiter for emmiting light and reciever for recieving light .

When emmited light is intruptted by sensing object, it changes the amount of light that arrives at the reciever

Laser sensor

These uses a focused, coherent light to measure distance to target object.

In factory automation applications, the target is usually a product or a machine element.

They detect any solid object and produce an object proportional to the measured distance independent of material ,colour and brightness.

Fundamental of sensor design

• Every single loose panel, which are being welded in a tool should be sensed
• If component is really small, we need not use two or three sensors for that you can use one sensor to detect the perticular panel
• If a panel is really big, we will use two sensors in opposite direction to sense the panel.
• So every sensor should be mounted in three directonal adjustable ways in general.

Q.16

Rough locator -

Rough locators are elements that aid the operator to guide the car panel while loading onto the fixture and ensure fool proof assembly

Fundamentals of rough locator design

• Rough locators should be placed at the edge of car panel which it has to guide
• It should guide the panel in the pin arresting direction
• It should guide the panel before 10-15mm to start the pin engagement
• It should be designed with entry angle for the car panel .Generally it ranges from 30-45 degree
• It should be designes with two slots to mount the easy adjustment
• The locator should be in the direction of car part guiding

Q.17

Base Unit

Parts of base unit

a. Valve Box -

It is basically a box which suppiles air to all pneumatic cylinders assembled in fixture.

b. Truncking channel

It is kind of cable duct, which helps to guide and protect the wiring used in fixtures

c. Measuring the hole cover

In this, the coordinates points are engraved on it

The measuring hole helps in CMM inspection & QC inspection

d. Eye bolt

An eye bolt is bolt with a loop at one end. they are used to firmly attach a securing eye to a structure ,so that ropes of cable may then be tied to it for lifting purpose

e. Pedestal-

It is a stand like structure where the entire unit of the base will be mounted

f. Floor plates -

It is used to mount entire base with floor.

Also helps to achieve flatness of the fxture.

Q.18

Dump unit -

• Dump unit is where you assemble component if you have certain constraint.
• Here you will have clamp unit, pin unit attached panel will be assembled.
• so if you have crtain constraint you cannot assemble in normal way

Function of Dump Unit -

• If you have perticular constraint and you cannot assemble in normal way to use it in different way again it has same dump cylinder and it has open position
• That is why these are very complex and design
• If you have any geometrical constraint, you can use this dampner to contraint your component.

Q.19

Slide Units -

These are positioning units, which are used to potision the car part or panel,unit,weld gun,robots for further operation.

These are classified in two ways,

1.Hardened guide way

2.LM guide way

It is further classified into three types based on prime mover

1.Manual slides

2.Hydraulic/Pneumatic slide

3.CNC slide

It may further classified depending upon applications,

1. Horizontal slide unit

2. Verticle slide unit

3. Angular slide unit

Basic fundamental of slide unit design,

• Reverse stroke 10mm to be considered in both forward & retracted condition.
• Cylinder & LM guide to be validate for load & stroke
• Master guide way should be considered & the subsidiary guide way to be free.
• Mechanical hard stop to be considered for both extended & retracted condition to reduce impact load.
• Slide to be locked in the working position
• Slide to be locked with a safety pin in the retracted position during transportation,
• the two end limits to be sensed externally by a proximity switch
• The design should be checked for screw accessibility, ease of assembly, machinability part,
• The LM guides and rails are integral assemblies and should not be separated at any cost.
• LM guide ways to be lubricated for long life.