Week 3:- BiW Fixture Design Methodologies Challenges

What is a design methodology?

design methodology is nothing but the steps followed during the concept designing stage of fixture design. Below are the steps followed during design methodology.

a.Purchase Order

It is basically a confirmation from the customer side, that we are ready to start the designing or, go ahead.

b.Inputs From Customer

Input From customers are the major inputs that we get from the customers, how do we study those inputs, what kind of information and get out of those inputs, These are the criteria that we mentioned in this particular input from the customer.

a)Functional Requirements:

Functional requirements may involve calculations, technical details, data manipulation and processing, and other specific functionality that define what a system is supposed to accomplish.The purpose or the function of Fixture will be given as inputs from the customers like what are the processes that the fixture is going to do...i.e .,welding, glueing, riveting or whether it is a checking fixture.

b)Preferred standards:

The customers requires to follow some standards.These standard parts which we can use as it is in our design which saves our project time and money as well.By following the standards the time of designing and manufacturing of parts will be saved,which will be automatically minimize the time of projects.As for the standard parts,it can be easily replaced from the used fixture to the new fixture,which may reduce the cost.

c)Car products:

It includes the following input from the customer

1)GD&T:Geometric Dimensioning and Tolerences of the part for which the fixture has to be designed.GD&T provides information about Locating pins,Rest,clamp,Dumps,and slides information of each station,sequence and opening of clamps,Dumps and slide stroke information.
2)Part List:This is the list of part which are going to assemble in the fixture.It includes information about the Part name,Part number, Tooling revision,Part thickness etc.
3)CAD Files of Part:The 3D model file of the CAD part design by using modelling software is given from the customer.
4)Clamp plan:Clamp plan of the part while doing the operation is given from the customer,we cannot change the clamp plan without permission from the customer.
5)Product aseembly process sheet:It gives detail process of the completion of the part from scratch to the finished product assembly.

d)Layout:Layout shows the entire assembly plan to understand the process.Layout provides the information of flow of parts,station pitch,robot stations.Accesories like Tool changers and tip dressers,sub assembly links,plat form heights,loading/unloading sequence.

e)Ergo data:As same as the preferred standards,different companies follow different standards of Ergo data.We have to follow the customer standards of ergo data.th inputs of the Ergo data will be given by the customer mostly in case of manually operated fixtures/manual fixtures.The ergo data is mainly used to make the operator comforatable which maylead to the efficiency in cycle time and Production.Ergo data provides input like Platform height,Maximum and Minimum reach from operator to the fixture,Maximum and Minimum height of the fixture.Also provides information like Loading height,working safety zone of operator,etc

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f)Weld study:Weld study is the important input given by the customer.It gives details about the study of particular gun that we use for welding.Also the data like no. of welds,position of weld in the components will be given.In short weld study includes weld gun details,weld matrix and weld points.

g)Standard Detailing Templates:The inputs including the detailing templates of the 2D drawing as per the customer standards.So we have to follow the detailing templates as per the customer standards.

c.Percentage Completion Criteria

Percentage completion criteria is basically schedule. What time that we can complete the entire process again this is more detailed. So when we are going to complete the in entire designing, then we're going to move on to simulation on all these subcategories would be considered in percentage completion cateria like a probability to when we can complete the entire fixture design.

d.Design Output

In BIW fixture design or any industry. We don't only just design a particular component and just give the CAD file to the customer, you have to give a lot of documents like 3d documents,2d documents, which is the detailing part, and as well as other factors as well like bom, bom bill of material and other documents as well about this particular component and their standards, all has to be submitted to the customer.

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

a)Functional Requirements:

Functional requirements may involve calculations, technical details, data manipulation and processing, and other specific functionality that define what a system is supposed to accomplish.The purpose or the function of Fixture will be given as inputs from the customers like what are the processes that the fixture is going to do...i.e .,welding, glueing, riveting or whether it is a checking fixture.

b)Preferred standards:

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The customers requires to follow some standards.These standard parts which we can use as it is in our design which saves our project time and money as well.By following the standards the time of designing and manufacturing of parts will be saved,which will be automatically minimize the time of projects.As for the standard parts,it can be easily replaced from the used fixture to the new fixture,which may reduce the cost.

c)Car products:

It includes the following input from the customer

GD & T

The geometric dimensioning and tolerencing which is an important part of designing is provided for the part for which fixture must be designed. It provides the information of location of the pins, rest, clamp, dump & slide of each station. The clamp opening sequences dumps & slide stroke information also provided in GD & T.

Part list

Part list consist of all the information such as part name, part identification numbers of the parts that has to be assembled. It also provides the number of revisions that the part, tool and fixture has undergone. The material specification like thickness also available in the part list

Cad files

Cad files are the 3d models of provided part. The customers provide the cad files in any of the shareable formats like .igs, .stp which can be opened in most of the design softwares available.

Clamp plan

Clamp plan is provided by the customers, which shows the position where the clamps can be provided. These positions are provided in the coordinates so that the clamps and pins can be placed exactly at the required position. The diameter and tolerances of the holes are also provided. The clam plan and the welding spots plan can never be changed without the knowledge of the customers until the change in position is required.

Product assembly process sheet

The product assembly process sheet describes in detail about the assembly sequence of the sub components and main component. It also describes the type of joint the assembly undergoes. The assembly sequence followed in the process sheet should be followed while designing the fixture plan. The plan cannot be changed by the designing team. If required it should be made with proper knowledge of customer.

d)Layout:

Layout shows the entire assembly plan to understand the process.Layout provides the information of flow of parts,station pitch,robot stations.Accesories like Tool changers and tip dressers,sub assembly links,plat form heights,loading/unloading sequence.

e)Ergo data:As same as the preferred standards,different companies follow different standards of Ergo data.We have to follow the customer standards of ergo data.th inputs of the Ergo data will be given by the customer mostly in case of manually operated fixtures/manual fixtures.The ergo data is mainly used to make the operator comforatable which maylead to the efficiency in cycle time and Production.Ergo data provides input like Platform height,Maximum and Minimum reach from operator to the fixture,Maximum and Minimum height of the fixture.Also provides information like Loading height,working safety zone of operator,etc

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f)Weld study:Weld study is the important input given by the customer.It gives details about the study of particular gun that we use for welding.Also the data like no. of welds,position of weld in the components will be given.In short weld study includes weld gun details,weld matrix and weld points.

g)Standard Detailing Templates:The inputs including the detailing templates of the 2D drawing as per the customer standards.So we have to follow the detailing templates as per the customer standards.

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

Following are the inputs required from car products for designing a fixture:

GD & T

The geometric dimensioning and tolerencing which is an important part of designing is provided for the part for which fixture must be designed. It provides the information of location of the pins, rest, clamp, dump & slide of each station. The clamp opening sequences dumps & slide stroke information also provided in GD & T.

Part list

Part list consist of all the information such as part name, part identification numbers of the parts that has to be assembled. It also provides the number of revisions that the part, tool and fixture has undergone. The material specification like thickness also available in the part list

Cad files

Cad files are the 3d models of provided part. The customers provide the cad files in any of the shareable formats like .igs, .stp which can be opened in most of the design softwares available.

Clamp plan

Clamp plan is provided by the customers, which shows the position where the clamps can be provided. These positions are provided in the coordinates so that the clamps and pins can be placed exactly at the required position. The diameter and tolerances of the holes are also provided. The clam plan and the welding spots plan can never be changed without the knowledge of the customers until the change in position is required.

Product assembly process sheet

The product assembly process sheet describes in detail about the assembly sequence of the sub components and main component. It also describes the type of joint the assembly undergoes. The assembly sequence followed in the process sheet should be followed while designing the fixture plan. The plan cannot be changed by the designing team. If required it should be made with proper knowledge of customer.

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What is a clamp plan?

A clamp is a force-actuating mechanism of a fixture. The forces exerted by the clamps hold a part securely in the fixture against all other external forces. Clamping surfaces are subjected to the clamping forces for obtaining invariant location. To fix a part at a particular position, we use 3-2-1 principle in all types of fixtures to restrict degrees of freedom. Each Panel is fixed keeping 3-2-1 principle in mind. This principle requires us to use minimum 3 rests, 2 pins and 1 clamp to fix a panel. While we receive the panel, the customer also gives us the coordinates of panel where he wants us to rest, clamp and locate the panel. We can directly input these coordinates and start designing rests clamps and pins. Clamp Plan document serves this purpose.

Clamp plan provide location of pins, rest, clamp, dump etc. It is in more detail. Clamp Plan is a document that contains the panel drawing mentioning all the places where clamps and rests are to be given. It gives exact location in X, Y, Z co-ordinate values to start designing. We should never change clamp position without permission of customer.

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What is a purpose of a process layout?

The main purpose of layout is to describe the work area of the robot and the positions of fixtures according to the work sequences. Layout of fixtures and robot is an important process planning task which describes the entire thing that will be involved in the product manufacturing.

1)Flow of Parts:It shows the flow of parts in the assembly line or shop floor like how component move from one station to another station after the completion of process.
2)Station Pitch:The distance between two stations is called as station pitch.It shown the space constraints netween the two stations the Layout.
3)Robot Stations:It shows the position where the robots be placed,which is shown in the Layout.
4)Sub-assembly Link:Sub-assembly link is nothing but the links between the assembly Fixtures & the main assembly line.It shows that how the sub-assembly fixtures are linked with the main-assembly line.
The main purpose of the layout is to understand the entire plan of the assembly line.

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What is Ergo data?

Ergo data deals with the ergonomics of a fixture which means it contains information about operator distance from panel, reachibility and height at which fixture should be designed so that it is easier for the opeator to load and unload the panel. Each company has differnt ergonomics requirement. Ergo data is applicable to manual Fixtures only. Ergo data ensures safety and comfort of opeartor. Only when an operator is comfortable working that he can do the work efficiently without error.

Most important aspects while designing the fixtures keeping ergonomics in mind are:

1. Physical access (space) for hands or tools and clear

visual viewing angle
2. Eliminate obstructions in front of working area for

ease of access e.g. knob position

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What do you understand by Weld study?

Weld Study includes

1.Weld Gun Details

2.Weld matrix and weld points

3.Geo weld points and Respot Weld Points

1.Weld Gun Details

This involves the study of the gun. So weld study includes weld Gun detail weld matrix and weld points. Weld un can be of several types and several variants. Dependin the the manufacturing requirement, they are chosen wisely.

2.Weld matrix and weld points

Weld points are basically where the welding is going to happen at which point at which coordinates is going to happen.

3.Geo weld points and Respot Weld Points

The data of weld metrix and weld points will be given to you in the form of spears i.e Green and red Spears.

• At that points welding is going to happen.
• Geo spots are Red in Color and Re spots are Green in color.
• All the red spheres are going to happen in geostationary.
• In the respot station where the green welding is going to happen. So this is happens where one component is going to attach to this particular component, and in the other station, the other component get attach.

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

It is followed in design stages and depart stages in the welding fixtures. Decided based on the duration provided as an input along with the concept designing and simulation check. The percentage consideration after several corresponding processes are predefined conventionally. The details are given below:

0-25% input and concept design

The 25% of the project is completed when the input from the customer finishes and followed by the concept design creation. This 25% completion must be done according to the specific duration allotted to this concept designing for the design team.

25-40% concept design approval

Once the concept design is finished by the design team. It should be sent to the customer for their approval. If there is any correction and clarification required by the customer should be cleared within a specific period of time. So at this stage if it is completed then the 40% of the project is finished.

40-85% Designing, Freezing and detailing

After the approval of the customer then the production model is designed with all the standard components required and the detailed part list is prepared with Bill of Materials. Freezing the design after the completion of entire design is done. Then the detail drawing is prepared from the final design. By finishing the detail drawing and other documents the 85% of the entire project is completed.

85-100% Check and final dispatch

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Brief about "Output" in design?

The design output is the form of 2D drawing and a 3D model it may be of IGES, STEP file formats or any other cad shareable formats. The design output also includes some of the documents related to the design which may be required by the customer for the validation. The documents and design provided are categorized by following ways..

1.Unitized Tools

In the unitized tools testing requires two types of drawing sheet,which is one key sheet and layout sheet.

So example of a unitized tools are fixtures,tools So where exactly multiple units are a placed.For example, the entire assembly welding fixtures,where a pin unit,clamp unit,rest unit and the panel, everything is included so that for those things.

• KEY SHEET:

Basically a key sheet shows the orthogonal view of 2D drawing of a finished fixtiure containing all its units. It is only provided for the unitized tools. These tools are much important that they are used in fixture which are high precision and have geometric tolerance. These unitized tools (pin units, base unit and other important units) must need a key sheet since a key sheet provides the placement and location of these tools on the tool base. The orientation of the tool is also represented by the key sheet. A key sheet is much help full in assembling the fixture.

• LAYOUT SHEET:

Layout sheet consist of description drawing of each units which representing their layouts as well. This will be useful when placing or assembling each parts so that their orientation is not changed. It shows the table of content with quantity. It also contains standard components like screws, bolts, etc,. The layout sheet is basically provided for both unitized and non unitized tools.

2.Non-Unitized Tools

Tools that can stand alone and can be detailed completely on a layouy sheet.

Non unitized tools are basically tools like Stands and tool changers is also an example of an non unitized tools where you don't need key sheet, you can actually used to layout sheet and complete the entire documentation of the particular component. So this is as known non unitized tools.

The output should comprise of the following details:

a). Approved standard parts should be used wherever possible. This saves lots of time, effort & economical.

b). Design should be as simple & economical as possible. Geometry is complex then fixture designis complex but approach is trying to design as simple as possible.

c). Design must comply with all current safety & ergonomics standard.

d). Design must provide for controlled & damage free handling of product. It should not damage other part.

e). Adequate error proofing provision must be incorporated in each design by providing proximity switches, rough locators etc. Proximity switches are basically sensors which tells part is present or not in fixture. Rough locators work as pokayoke to guide entire panel orientation.

f). The weight of moving part must be kept to minimum while maintaining maximum strength. Weight of moving component kept as minimum as possible but it shouldn’t compromise on strength. There is balance between these two things.

g). Frames & structures are to be simple & sturdy.

h). Design clearance & accessibility for routine maintenance & service. Fixture need to maintain after certain period of time so it is easily accessible for maintenance.

1. i) Motion control must be considered on any moving component. Adequate to control the motion of component like slider, clamp arm so that it does not give any vibration & stays on particular limit by use of hard stopper, shock absorber.

j). Designer is responsible to validate all clamps & weld guns. So that all clams & gun should perform its function without fail.

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

Structuring a design tree is a most important thing in design process. When the design tree is get structured properly then the possibilities of getting errors are avoided. A proper structure tree is standard thing that every designer should follow. Some companies will have their own standards how a design tree must be structured.

There are some guides that should be considered while structuring a design tree.

• Structuring a design tree is the process where all the assemblies & parts are named in a specific standard. Each customer will have different set of standards to structure a design tree.
• A proper design tree structure will help us to identify the part name, assembly as to which project, tool or unit, it belongs to. This helps us to avoid the errors during study, manufacturing, assembly, inspection etc.
• If a part or a assembly is not named properly or the design tree is not structured properly, it will create confusion to understand the design & may create major possibilities of making an error.
• Naming of a fixture or a unit or a part, gives the information as to which project or zone or assembly do they belong.
• It also can help us to identify the quality of items of same type or different types that are being used in an assembly.
• Mirrored parts get different part names incase their orientation is changed in the assemblies and they are considered as two different parts and not as a single part.
• The design structure tree follows a sequence in which the manufactured parts are mentioned first, then followed by the standard components and at last the bought outs are listed.

One of the many naming nomenclatures followed:

P002_Z01_ST010_02_03

Here P002 is project code
Z01 is zone
ST010 is station number
02 is unit number
03 is part number

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What are Units? Mention 5 types of units.

A unit is a device that has a specified function, especially one forming part of a complex mechanism.The BIW fixtures is the assembly of different units which are designed to fulfill different purpose.The unit have the specified function like resting the panel, clamping the part, Locating the part etc.According to the 3-2-1 principle of fixture design the units are designed to locate & clamp the car panel to its specified positiion in fixture while operation is going on.

1)Sensor unit:It is non movable locating unit used for proper location of the part
2)Fixed 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.

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Describe Fixed Pin units & their purpose?

As of the name this unit contains a pin which is fixed to it, this is used to locate the car panel on to the fixture. The fixed pin unit has some parts to make it a complete unit.

Purpose of fixed pin unit-

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

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

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

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What are the different parts of a fixed unit?

a.Fixed pin unit consist of riser, blade, block, shims or spacer, pin retainer & pin.

b.Riser is the standard part which is used to rise up the height of the while unit. Blades are plates mounted on the riser. Other parts like cylinder, arms etc are mounted on the blade.

1. Shims are the small part 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. In fixed pin shims are used to adjust to traslational motions.

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

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

The rest units are designed to rest/support the car panel by using NC blocks/Mylar/Rest.It is the simplest unit to design because it has fewer parts to design & the purpose is only resting of the car panel.Because of this simplicity, the rest unit is combined with other units to reduce the cost of the overall project.It can be combined with the 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 combine together in one unit to reduce cost.

Components of rest unit:

• NC Block
• Spacer
• Blade
• Riser

a). Mylar/ NC blocks/ Fingers: These are parts are used to hold panel. They are globally called as Mylar. Top side Mylar is called as clamping Mylar & bottom side is called resting Mylar. Every clamping Mylar should have resting Mylar. It is jaw type.

b). Riser: Risers can be of L-type, welded or square tube or frame type. These are basically manufactured parts are used to give height to assembly. It is machined at mounted ends only to save cost.

c). Blade: These are plates mounted on the riser. Other parts like cylinder, arms etc are mounted on the blade.

d). Shims/spacer: In fixture, we are providing tolerance to each part mostly manufactured. Those tolerances tend to stack up & reflect together. In order to avoid that we use shims so we can easily adjust after assembly so whatever stack up there we will rectify it through shims. Shims come in thickness of 0.1, 0.2, 0.5 etc.

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What are the basic fundamentals to design a Sensor unit?

Sensor is an input device which provides an output (signal) with respect to a specific physical quantity (input).The term “input device” in the definition of a Sensor means that it is part of a bigger system which provides input to a main control system (like a Processor or a Microcontroller).

Another unique definition of a Sensor is as follows: It is a device that converts signals from one energy domain to electrical domain. The definition of the Sensor can be understood if we take an example in to consideration.

There are some basic fundamentals adapted while designing sensor unit

• Every single panel get assembled should have separate sensors.
• Small components can be sensed with help of only one senor. But for a bigger component 2 to 3 sensors should be used placing at opposite diagonals of the panel.
• Every sensor should be placed in a manner that it can be adjusted in three directions.

Types of sensors used

• Proximity sensor:it can able to detect the presence of nearby component without any physical contact (it range is between 5 to 10 mm).
• Laser sensor:this sensor uses the laser beam which travels in the straight line to detect the presence of object in its path. It is a long range sensor.
• Photo electric sensor:photoelectric sensor uses light transmitter, often infrared and a photoelectric receiver to detect the object.

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What is a Rough locator unit & what are the basic fundamentals to consider while designing it?

Rough locators are usually used in loading & unloading of particular part. It is also used to guide. Rough locator unit is apart designed to guide the operator to locate car panel on the pins accordingly. They have slot for adjustment. A rough locator can be of std. part or mate part. It is also work as pokayoke.

Fundamentals of rough locator design.

• Rough locators should be placed at the edge of car panel, which it has to guide using locating pins one can easily restrict movement of entire car panel.
• Rough locator has to be placed in the same angle of the car part edge with minimum distance of 2.5 mm from the edge of car part, so it should no damage panel.
• Rough locators should guide the panel before 10 to 15 mm. to the start of the pin engagement.
• Rough locators should guide the panel in pin arresting direction in general.
• Rough locators should be designed with two slots to mount for easy adjustment. (in general)
• The slot should be in the direction of car panel guiding.

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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.

It comprises of the following components:

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.

Valve box

A valve box is basically a box which supplies air to all the other pneumatic cylinders. it's it's a device which includes a lot of other solenoid valves, so it will have one inlet and one outlet and from that one inlet, all the other solenoid valves will be attached to it. And each solenoid valves will have the input, and then again supplied to the separate cylinder, then again the output will be collected, while this solenoid valves, and again given back to the valve box.

Measuring hole covers

Measuring Hole covers is on the base unit which is for measuring purpose.

Eye Bolt

It is to drag the entire unit and relocated.

Pedestal

By this pedestal is for standing the entire unit.

Weld Bars and floor plates

Weld bars are to mount it to the floor.

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What is a Dump Unit and what are its functions?

A dump unit is a unit where you actually assemble a component which if you have certain constraints.

Primary function of a dump unit:

When we have some geometrical constraints then we can not mount normal units like clamp unit, pin unit etc. In this case, the dump unit is used.Dump unit is the complex unit to design due to space contains there is less space available & have to adjust all the parts in available space.It consists of a dump cylinder to perform the operation of clamping & unclamping car panel.

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

A slide unit is basically used in space constrains in assembling a part. This unit is also a complex unit. It contains sliding bed, cylinder, open position, close position, guide box, position locking unit, sensor unit, stopper block.

Components of a slider unit:

Sliding cylinder

Sliding cylinder has One open position and One closed position, which has to guide rails direction to the entire panel is going to move.

position locking unit

Position locking unit which will lock the position at that particular point doesn't allow the entire plate to move.

Sensor Unit

Sensors need to sense whether this entire component has reached here or not.

Stopper blocks

Stopper blocks as I said initially to control the entire panel moving and it's a moving part.

Slide units are used when we have some space constraints. So we dont have space to design different special units & to assemble it. In those case we use sliding units.

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