Week 3:- BiW Fixture Design Methodologies Challenges

What is Design Methodology?

Design methodology is the steps followed during the concept designing stages of fixture design.

Purchase Order: Purchase order is the order from customer for start of work. It is basically a confirmation from the customer side, that we are ready to start the designing or, go ahead.

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.

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

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, we have to give a lot of documents like 3d documents, 2d documents, which is the detailing part, and as well as other factors like bill of material and other documents as well about this particular component and their standards, all has to be submitted to the customer.

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

Functional Requirements: Functional requirements is basically what kind of function that a particular fixture design is going to have, for example welding, gluing, riveting fastening this kind of information will be given to us from design department.

Preferred Standard Component: Preferred standard component is basically what kind of standard components that the customer already have. And we have to design, according to the standard component itself. And this inputs actually saves a lot of time, as it saves a lot of efforts from our side as well as the company side as well. So if they have any component that we already have their standards, then we don’t have to design those particular components. And also then they don’t have to purchase it from the outside as well.

Car Products: Car products like 3D files, 2D files, as well as to learn and to study what kind of geometrical tolerances and what kind of PLP points (Principle Locating Points) where we can fix those pin units or the clamp units at that particular position.

Layout: Layout is basically an layout of the entire assembly line to understand the process and the flow of work and the space constraint that we have.

Ergo Data: Ergo data is basically involved where manual operators are involved and every company has different standard for ergo data, so we will be getting that particular input from the customer so these are the standards that we follow. So, this kind of Ergo data we get from the customer.

Weld Study: Weld Study is the study of the particular gun that we are going to use for welding and where we are going to weld. So if you’re doing a spot welding what kind of spot welding we are going to do number of welding, exact coordinates on the particular component.

Standard Detailing Templates: Every company has different types of standards, so they will give us detailing templates about how to detail the particular component and dimensions.These are called standard detailing templates.

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

Car Products Include:

• GD & T
• Part List
• Cad files of car part
• Clamp plan
• Product assembly process sheet

GD&T: GD&T (Geometrical Dimensioning & Tolerance) provides information of locating pins,rest,clamps,dumps & slide information of each station. Sequence of opening of clamps, dumps and Slide stroke information. In GD & T we will learn about locating pins so where we can actually locate our pin units and rest clamp.

Part List: Part list means what kind of assembly, those parts are going to be. In the part list there are part numbers,part names mentioned.Every part having different name.

Cad Files Of Car Parts: CAD files of car products the 3d component that we require from all the car parts.

Clamp Plan: Clamp Plan is very important input data that we get in the car products is where exactly we can place those clamp units and the particular pin units. We should never change the position of the particular clamp or the pin, which is given in these data. We can change our design a little bit here or there, but we should never change the input design data about the clamp position or the pin position.

Product Assembly Process Sheet: In the product assembly process sheet we get to learn what kind of products we are going to assemble in that particular component or the particular Unit.

What is the Clamp plan?

• Clamp Plan is very important input that we get in the car products
• Clamp Plan provides the location of pins,rest,clamp,dumps,etc
• It gives information about where exactly we can place those clamping units and the particular pin units.
• We should never change the position of the particular clamp or the pin, which is given in these data.
• We can change our design a little bit here or there, but we should not change the input design data about the clamp position or the pin position.
• It also gives the exact location of y and z coordinates designing as well you can just input these coordinates and you can start designing from there.

What is the purpose of a Layout?

The Layout sheet will give us information about all the fixtures that are placed the robots that are going to work on it.

In layout sheet the circle around the robot is called swepped area of that particular robot this is basically the reachability of that robot which is confined to the particular circle.

The entire sheet will give you the plan of the layout, what are the constraints that is there from the customer side itself.

Layout provides information of:

• Flow of Parts
• Station Pitch
• Robot Stations
• Accessories like tool changer and tip dresser
• Sub assembly links
• Platform height
• Loading/Unloading Sequence/Heights

Flow Of Parts: Flow of parts define how the particular component is going to move from one unit to another or one station to another station.

Station Pitch: Station pitch is distance between two stations, what is the space constraint that they have between two stations.

Robot Stations: Robot station is position where robots are placed.

Accessories like tool changer and tip dresser: Accessories like tool changers and tip dresser are used when a robot wants to change the particular tool, which it has to go to the particular location and change it or sharpen the tip at the tip dresser.

Sub Assembly Links: Sub assembly links are basically how the particular fixtures how the assembly fixtures are linked to the main assembly line.

What is Ergo data?

• Ergonomics refers to the study of human behaviour and movements
• Ergo data provides information of loading height, working safety zone of operator, etc
• So, this is very important as it images to the study of human behaviour and moments and your data provides information of loading height, working safety zone and operation. So it also gives you the safety zone of a particular man operator. So, how much distance is supposed to be from the weld gun.
• The heights are mentioned because of the operator itself, he should not bend while doing the operation. It is going to be a strain on his back, the height should not be way too much so that he can’t even see what the other particles are because it’s going to be uncomfortable for him and his shoulders are going to get sprained.
• So this is basically to make the operator as comfortable as possible so that he will be more efficient in doing work and he will not take a lot of time while doing the particular assembly.

What do you understand by Weld study?

Weld study involves the study of gun in an assembly and also the location of weld, type of weld and the number of welds that we need to perform on that particular component.

Weld study includes:

• Weld gun details
• Weld matrix & weld point
• Geo weld points & Re-spot weld points

Weld gun details: This involves the study of gun which is used in assembly.

Weld matrix & weld point: Weld point is where the welding is going to happen the location the exact coordinates of weld

Geo weld points & Re-spot weld points: The data of weld matrix and weld points will be given to us in the form of spears i.e. green and red spears. At these 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. Re spot station is where one component is going to attach to this particular component.

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

Percentage completion criteria is followed in the designing stages and dispatch stages of the welding fixtures

• 0-25% - Input and Concept Design
• 25-40% - Concept approval and Simulation Check
• 40-85% - Design Freezing and Detailing
• 85-100% - Check and Final Dispatch

Brief about "Output" in design?

Design output includes 3D models and the 2D drawings of the tools. Apart from it, it also includes different documents like bill of material.The tools used are of two types:

1. Unitized Tools
2. Non-Unitized Tools

Unitized Tools: Unitized tools requires two types of drawing sheets

• Key sheet - An index of units and their placement on the tool base
• Layout sheet - A detailed drawing of individual units to include all of their components

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

Non-Unitized Tools: Tools that can stand alone and can be detailed completely on layout sheet. Non unitized tools are basically tools like stands, tool changers, conveyors, grippers, turn tables where you don’t need key sheet, you can actually used to layout sheet and complete the entire documentation of the particular component.

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

• Structuring a design tree implies to a process where all the assemblies & parts are named in a specific standard. 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, tool or unit, it belongs to.
• This helps us to avoid the errors during design study, manufacturing, assembly, inspection etc.
• If the parts or assemblies are 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 can help us to identify the quantity of items of same type or different types that are being used in an assembly.

What are Units? Mention 5 types of units.

Units are devices which have specified functions, especially one forming part of a complex mechanism. A fixture is a assembly of differenet types of units.

Units are classified into two types:

• Simple Units
• Complex Units

Simple Units:-

Fixed Pin Unit: Fixed pin unit are units which have a pin which is already fixed it cannot be moved.

Rough Locator Unit: Rough locators are usually used in loading and unloading of that particular panel.

Base Unit: Base unit is where all the units are to be mounted.

Complex Units:-

Slide Unit: The slide units are basically where the sliding mechanism is involved.

Dump Unit: Dump unit is basically like a conveyor where you keep all these panels stacked up right for storage.

Describe Fixed Pin units & their purpose?

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

The pin unit is used to restrict the degrees of freedom of a part while weling operation.

It is part of 3-2-1 locating principle of fixture design.

The different parts of a fixed pin unit are:

• Pin
• Pin Retainer
• Shims
• Block
• Riser
• Blade

What are the different parts of a fixed unit?

Pin: Pin is a part which helps in locating the car panel. The locating pins are used to locate a body part in a position accurate enough to execute the welding process. Pins are available in either small head or large head.

Pin Retainer: A pin retainer is a part which holds the pin in position it can either be a make part or standard part. The pin retainers will be fixed to a block.

Shims: Shims are basically spacers used to fill gaps between parts. A shim is thin tapered or wedged piece of material used to fill small gaps or spaces between objects to provide better fit and level surface.

Riser: It is a part on which all the parts of a unit are mounted and the riser itself is mounted on the base plate. It is used to raise the height of unit. Risers can be of two types i.e. 'L' type riser & square tube riser.

Blade: Blades are plates which are attached to riser.

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

A rest unit is a unit designed to rest/support the car panel using NC blocks/mylar/rest.

The different parts of a rest unit are:

• NC Block
• Spacer
• Riser
• Blade

What are the basic fundamentals to design a Sensor unit?

A sensor unit is a unit designed to sense the car panel by using Electrical sensors. This signals from the sensors will be fed to the PLC and so the next process will be executed by this signal.

The types of sensors used in general are:

• Proximity sensors
• LASER sensors
• Photo electric sensors

Fundamental of Sensor unit design:

• Every single loose panel which are being welded in a tool should be sensed.
• Each panel should be sensed by 1 to 2 sensors depend on the size of panel, Preferred to be in diagonal opposite ends of panel.
• Every sensor should be mounted in a 3 direction adjustable way in general.

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

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

Fundamentals of Rough locator design:

• Rough locators should be placed at the edges of the car panel, which it has to guide.
• Rough locators has to be placed in the same angle of the car part edge with a minimum distance of 2-5mm from the edge of the car part.
• Rough locators should guide the panel in pin arresting direction
• Rough locators should start guiding the panel before 10 to 15 mm to the start of the pin engagement.
• Rough locators should be designed with entry angle for car part entry.
• Rough locators should be designed with two slots to mount for easy adjustments.
• The slots should be in the direction of car part guiding.

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.

The parts of a base unit are:

• Trunking channel
• Valve Box - It is a box which supplies air to all other pneumatic cylinders.
• Base Plate
• Measuring hole cover
• Eye Bolt - It is used to drag the entire unit and relocate.
• Pedestal - Used to stand the entire unit.
• Weld bars
• Floor plate - Used to mount the unit to the floor.

What is a Dump Unit and what are its functions?

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

If you have particular constraint and if you cannot assemble it in a normal way so you can use this dump unit to assemble it in different ways again.

Dump unit has dumb cylinder, open position, closed position and it has clamp cylinder unit too.

If you have any geometrical constraints, you can use this dump unit to constrain your components.

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

Sliding units are basically used in places where you have a lot of constraints or space constraints, when you cannot use different types of units to design the entire assembly. So, here you will use this sliding unit.

Sliding unit consists of:

• Slide Cylinder
• Guide Rail
• Guiide Block
• 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 are used to control the entire moving and it’s a moving part.