BIW FIXTURES 3RD WEEK

1. DESIGN METHODOLOGIES

A design methodology provides the detailed information of the sequence of operations involved in the designing of BIW fixtures. It also helps to discuss about the documents needed from the customer side and the documents to be submitted form the supplier side also.

Purchase Order:

Purchase order (PO) is the legal order released for the purchase of the product. By the confirmation of the purchase order the design team can proceed further planning.

Input from the customer:

There are set of information that has to be getting from the customer side in order to plan for the fixture design process. This includes:

• Functional requirements
• Preferred standard components
• Car product
• Layout
• Ergo data
• Weld study
• Standard detailed templates

Percentage completion criteria:

The percentage completion criterion includes clear information of the time period of design process at each stage. The schedule for the fixture design completion with analysis will be provided here.

Design output:

In design output the engineers will submit the 3D design, 2D detailed drawings of fixture design, Bill of materials and other related documents for the customer verification.

1. REQUIRED INPUTS FROM THE CUSTOMER

The design process depends on the information provided by the customer. The type of information that customers provide will makes a design engineer work easy because customers will have their own standards and plans for the assembly sequence. Here are some of the important inputs that has to be collected from the customers.

• Functional requirements

It provides the type of the fixture that has to be designed based on its function such as hemming fixture, welding fixture, checking fixture, storage racks, etc.

• Preferred standard components

Most of the times customers will provide the set of standards that has to be maintained, as each customers will have their own company standards. They also recommend the standard bought outs used in the fixture such as Risers, L-Blocks, Retainers, Pins, Clamps, Slides, Switches, Sensors, Weld guns, Tip dressers, Tool changers, etc.,

• Car product

Car product deals with the information about the BIW parts which requires the fixture design. The information contains GD&T of the parts, Part list with specification, Cad files of the part provided, Clamp plan, Product assembly process sheet.

• Layout

Layout provides the detailed information about the plan of various fixtures and robots positioned in the plant. The layout also shows the work path and maximum reach ability of the robot. The plan must be strictly maintained as in the layout. The flow of parts, Station pitch, Robot stations, Sub assembly links, Loading/unloading height and platform height.

• Ergo data

Ergo data provides the comfort zone maintained for the operator who works on the fixture. Informations such as loading height, working safety zone of operator. The Design engineer should consider the maximum accessible distance of the operator for his safety.

• Weld study

Weld study provides the weld gun details, weld matrix & weld points. The weld points include the geo spot and re-spots these are diffentiated by colours.

• Standard detailed templates

The standard detailing templates are provided by the customer since the parts must be dimensioned according to their own standards.

1. CAR PRODUCTS

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.

1. 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.

1. PURPOSE OF LAYOUT

Layout of fixtures and robot is an important process planning task which describes the entire thing that will be involved in the product manufacturing. The layout includes robots and their swept area, number of BIW fixtures used, and tools used. The main purpose of layout is to describe the work area of the robot and the positions of fixtures according to the work sequences.

The layout provides the information about the

• Flow of parts: The sequence of the part moved through various assembly lines
• Station pitch: The distance between two stations so that any interference can be checked and the reachability of the robot can be known.
• Robot stations: Describes the position of each robots
• Accessories: Accessories like tool changer and tip dresser required for the robot to improve their work flow are provided within the accessible limit of the robot. So that a robot can make use of these equipments quickly.
• Sub assembly link: The sequence of the sub component moving through its assembly process and joining to the main assembly is shown in sub assembly link.
• Platform height: Shows the accessible height of each individual fixtures
• Loading/unloading sequence: The loading and unloading sequence along the loading/unloading position of each component. The loading is done manually but the unloading is done by robots.

1. ERGO DATA

Ergo data ensures the comfort and safety zone of each worker and operator while performing his/her work. Each customer has their own standards for the safety of the operator. As a result the efficiency is maintained and productivity is increased since the operator feels comfortable with one’s work.

Ergo data is considered where the manual operation is required. The main motive is to maintain the safety zone of the operator. The actions such as bending, twisting, pulling should be avoided for maintaining the health factor of the operator. So these should be considered while designing the fixtures.

While designing the fixture the maximum distance should be maintained so that the operator can be comfortable with operating the fixture. The safety zone ensures operators safety that one can load and unload the component on a fixture without any interference with the fixture.

1. WELD STUDY

Weld study includes the types of welds used at each station. The joining of component requires different types of welding based on the components usage in the automobile. The informations included are.

• Weld gun specification
• Weld matrix & weld points

Weld gun specification describes the specification of the different weld guns used

Weld matrix & weld points shows the positions of the spot welds of the geo spots and the re-spot welding. The geo spots and re spots are mentioned in the different colours of spheres.

1. PERCENTAGE COMPLETION CRITERIA IN DESIGN STAGE

Percentage completion criteria are the estimated time for completing the project. In BIW fixture the percentage completion criteria are followed in design stage and dispatch stages. There are four stages in the percentage completion criteria.

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

1. OUTPUT IN DESIGN

The design output is one of the major process in BIW fixture 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 two ways.

• 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.

• LAOUT 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.

There are some guides followed in design output

• Designer must use standard approved components wherever possible in the fixture.
• Design must be as simple and economical.
• Design must meet safety and ergonomics standards according to the customer.
• The design must meet controlled and damage free handling of parts.
• Weight of the moving parts must be kept to a minimum while maintaining maximum strength.
• Frames and structures must be as simple as possible and sturdy.
• Motion control should be provided over each and every moving equipment.
• Designer is responsible to validate clamps and all weld guns.

1. STRUCTURING A DESIGN TREE

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.

1. FIXTURE UNITS

Basically a BIW fixture has some tools which contain different units. In which each units perform different operations. Tools are generally classified into two types

Unitized tools:

These tools are process functionalities tools. It has multiple tools for the process.

Rest pin unit: used to rest the component.

Fixed pin unit: used to locate the panel by a fixed pin.

Retractable pin unit: used to locate the panel by a retractable pin.

Rough locater unit: used to guide the operator on safe locating of panel.

Sensor unit: uses some sensors to sense the panel.

Base unit: used to mount all other units.

Slide unit: uses in complex way as a sliding mechanism involved.

Dump unit: it is complex unit used to handle complex assemblies

Non Unitized tools:

The non unitized tools are non process functionalities which include stands, take out trolleys, conveyors, turntables and some grippers.

1. FIXED PIN UNIT

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.

Pin which is the main thing in this unit which is fixed. Pin retainer supports the pin. Shims and spacers add the space required by the pin location. The shims are basically provided to adjust the pin horizontally and vertically according to the position of the hole. Shims avoid the stackup tolerances while assembling entire components.

1. PARTS OF FIXED PIN UNIT

The fixed pin unit is made up of some parts assembled together. Those are

• Pin which is the main thing in this unit which is fixed it may be of round or diamond shape depends upon the hole of panel.
• Pin retainer supports and holds the pin
• Shims and spacers add the space required by the pin location. The shims are basically provided to adjust the pin horizontally and vertically according to the position of the hole. Shims avoid the stackup tolerances while assembling entire components.
• Block is a component on which the pin and pin retainers are mounted.
• Blade or adapter blade which is mounted on riser to hold the block.
• Riser is a structure generally used to mount the toggle clamp and rest.

1. REST UNIT

Rest unit is designed to only rest the component of the fixture. It doesn’t have any clamps, no force is applied or no cylinders used. The rest unit only has risers and rest mylers. The rest unit is made with rest mylers, spacers, blade, NC blocks, and risers.

1. SENSOR UNIT

A sensor unit is used to sense the car panel over the fixture using the electrical sensors. This signal from the sensors will be fed to the PLC and so the next process will be executed by this signal.

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.

1. ROUGH LOCATOR UNIT

The rough locators are used to guide the operator how to locate the car panel on to the pins accordingly. The rough locater can be a standard or make part. It guides in loading and unloading the panel.

The fundamentals followed while designing a rough locator unit

• The rough locator should be placed at the edges of the panel so that the panel is guided.
• It should be placed as the same angle of the car panel edge with minimum distance of 2 to 5 mm from the edge of the panel.
• In general it is designed to guide the panel in pin arresting direction and it also should be in angle parallel to panel edge.
• The rough locator should be guiding the panel before 10-15mm of the pin engagement.
• The entry angle for the car panel should be considered while designing the rough locator.
• In general it should have two slots to mount for easy adjustments. These slots should be in the direction of car panel guiding.

1. BASE UNIT

The base unit is the unit where the other units such as fixed pin units, rough locator unit, sensor unit and rest unit, etc., are mounted. The other parts necessary for a tool like pneumatic valve box, trunking cable path will also be mounted on to a base unit. The base unit contains base plate, valve box, trunking channels, measuring hole cover, eye bolt, pedestal, weld bars, floor plates and number plate.

The base unit is fixed rigidly on the floor with the help of floor plates, it adjustable so that the horizontal surface of base unit can be maintained parallel to the earth’s surface.

1. DUMP UNIT

Dump unit is a critical unit which is used to assemble a component which has some assembly constrains. A dump unit usually has dump cylinder, open position, clamp cylinders. The dump unit is designed to use when an assembly of a car panel cannot be assembled in a normal unit. The dump unit design will also be complex.

1. SLIDE UNIT

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.

The slider bed of the slide unit is movable through a specific distance. This slider is actuated with the help of cylinder mounted aside. The slider moves within the guide box provided. The stopper block is provided to stop the slider motion at the end. The position locker is provided to lock the slider at the required position. The senor is provided to sense the open and close position of the slide unit.