Week 3:- BiW Fixture Design Methodologies Challenges

1. What is Design Methodology?

Design methodology is nothing but steps followed during the concept of designing stages of fixture design is basically, when we do a conceptualization of our design, there are a few millimeters that we have to consider, and then we start moving towards the design.

PURCHASE ORDER: 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.

Designer needs following basic information to start the BIW fixture,

• First understand scope of the work. Means what is expected by customer. Every customer has its specific requirements and it may have own raw material, electric, pneumatic, cad, design standards. Every customer also gives different inputs and expects output e.g. 2d drawing, process sheet in .xls, pdfs, CAD format of design, layout format, OLP.
• Bill of material (BOM) of the components to be welded-spot welding.
• CAD panel data or at least 2D drawing of assembly and individual panel data.
• Sheet metal panel thickness plays major role to decide 2 metal or 3 metal weld.
• Spot Detail information like total no of spots and spacing between the spots.
• Weld information clarity from drawing like 2 metal or 3 metal welding.
• PLP (Principle location scheme) of the individual panel and total assembly.
• Cycle time if calculated or can be found out as per manual or robotic welding process.
• Process sheet if Process engineering is done - where loading sequence, no of clamp data and gun data is mentioned.
• All clamping cylinder and fixtures standards.
• CAD -Software guidelines.
• Raw material standards.
• Design guidelines Bought out item (Purchased parts) standards like pneumatic items, toggle clamp, bearing, screw, dowel etc. company information.

PERCENTAGE COMPLETION CRITERIA:

• It consists planning of completion of total project. How much days the project will take to complete.
• It is followed in designing stages & dispatch stages of the welding fixture.
• It ensures that how much task that we have decided to complete within the stipulated time is complete or not & how much of it is rest to complete & whether it is going to be complete or not in given time.

DESIGN OUTPUT:

• Output consist 3D models, 2D drawing which is the detailing part, BOM & other related documents.
• There are some tools which are multiple units on common base are called unitized tools for e.g. fixture which includes no. of units on the same base.
• They required two types of drawing sheet as follows,
  • Key sheet- It shows the index of the unit & their placement on tool base.
  • Layout sheet- It is the detailed drawing individual unit to include all their components.
• Non unitized tools which can be completely detailed on layout sheet.

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

The following are the inputs we required from the customer to start the fixture design work.

FUCTIONAL REQUIRMENTS: This basically what kinds of function that fixture design have e.g. welding, gluing, fastening, riveting. The kind of information will be given to us in functional requirement i.e. it serve basic or main purpose like it is used for welding gluing or checking fixture so from that design concept generate.

PREFERRED STANDARD:

Every industry has its own standard & they follow that standard. In this requirement, preferred standard component is basically what kind of standard component customer already has. An input actually saves lots of time, cost & effort Because don’t need to design that component. It is purchased from outside from that make.

• Standard like ABB, NAAMS, FAUNC, FESTO, TUNKERS, ZYTRAN, DESTACO, Siemens etc. are used for robot, pneumatic parts, motor & gearbox, electric parts.
• Standard parts like riser, L-block, retainer, pins many other company actually manufacture this. Some component like clamp, cylinder, slides, switches, sensors.

CAR PRODUCT: Car product includes

GD&T:

• GD&T provides information of locating pins, rest clamp, dumps & slide information of each station.
• Sequence of opening of clamps, dumps & slide stroke information.

PART LIST: Part list is nothing but listing down all parts of assembly. It includes information about the part name, Part number Tooling revision, Part thickness etc. Assembly is broken down into each & every single part. First assembly has gone between hood inner panel & latch which going to attach next hinge going to attach. So there are different list of assembly we are going to perform. So every assembly will have different fixture unit.

CAD FILE: 3D file of that car product require from customer.

CLAMP PLAN: It provide information about position of clamp unit, pin unit, rest unit etc. this is major input from customer & should be never be changed without permission of customer.

PRODUCT ASSEMBLY PROCESS SHEET: It gives detail process of the completion of the part from scratch to the finished product assembly. It will give detailed plan of component how they welded as well how product is moving from one assembly to other.

LAYOUT: Layout provides information about Flow of parts, Station pitch, Robot stations, and accessories like tool changers, Tip dressers, Platform height, Sub assembly links & loading/Unloading sequence.

ERGO DATA: This data given when any manual operation involves. Ergonomics refers to study of human behavior & movement during the assembly work. It provides data regarding loading height, working safety zone of the operator etc. as per standard the company follow.

WELD STUDY: It includes information of weld gun detail, weld matrix & weld points. There are two types of weld points geo weld point & re-spot weld point. Geo weld points defines the geometry of part & re-spot do all other remaining weld points also ad strength to geo weld points.

STANDARD DETAILING TEMPLATE:

Detailing is 2D representation of 3D part. Customer has standard detailing template. These detailing formats are used for drafting of part.

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

GD&T:

Geometric dimensioning & Tolerance of the part for which the fixture have to be designed. GD&T provide information about Locating pins, Rest, Clamp, Dumps & slides information of each station & Sequence & opening of clamp Dumps & slide stroke information.

PART LIST:

Part list is nothing but listing down all parts of assembly. It includes information about the part name, Part number Tooling revision, Part thickness etc. Suppose first assembly has gone between hood inner panels & latch which going to attach next hinge going to attach. So there are different list of assembly we are going to perform. So every assembly will have different fixture unit.

CAD FILE:

3D file of that car product require from customer. The 3D model file of the car part is given from the customer to study on it. The car part is designed by using 3D modeling software. From this we can get some conceptual idea of the design in of fixture. The model is going to be the base of the fixture design. Below figure illustrate.

CLAMP PLAN:

It provides information about position of clamp unit, pin unit, rest unit, dump unit etc. This is major input from customer & it should be never being changed without permission of customer. Clamp plan provide exact location of pins, rest, clam etc. It is in more detail. It gives exact location in X, Y & Z co-ordinates value to start designing.

PRODUCT ASSEMBLY PROCESS SHEET:

Product assembly process sheet is sheet that gives following detail.

• Part assembly sequence
• Sequence of operation
• Cycle time.

It gives detail process of the completion of the part from scratch to the finished product assembly. It will give detailed plan o component how they welded as well how product is moving from one assembly to other? & this process plan should not be changed without permission of customer. below figure shows.

4. What is the Clamp plan

CLAMP PLAN:

• Clamp Plan is very important input that we get in the car products is where exactly we can place those clamping units are 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.
• In the Clamp plan there is clamp unit, pin unit and it is more detailed. 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.
• If the three coordinates, whole diameter and everything is already given to design the entire future design phase and it sometimes ministry as well. It happen that another thought position, also given very close to the clamp, or the clamp location. So always ask to whether you have changed the clamp position.
• You should never change the vent position or the clamp position without asking it so always be varying about these situations So the tool might get damaged or department get damaged so for that itself need to clarify once again before doing any changes in the clamp.

5. What is the purpose of a Layout?

• Layout is basically an layout of the 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 particular robot.
• So this is basically the reachability of that robot and which is confined to the particular circle.
• For example, Robot is going to work on the fixture, Details also mentioned the geo 250 and then number is given 250, and a you can see, 250 02 so this is dueling to one or two it's going to use there. So, this robot is going to work on the site first. Then after finishing the site. This fixture is going to rotate. And then it will come to T 01, and these two robots are going to work on the other side of the fixture. Similarly this robot is also going to work on the particular component as well.
• Entire sheet will give you in that plan of the layout of what are the constraints that is there from the customer side itself.
• If you want to do any changes for example, you're changing the geo fixture design and it's going to exceed a little bit bigger or smaller inside you have to inform the customer and you have to get the customers permission to do that so that he will also be able to change the design if we present him with anything.

6. What is Ergo data?

Productivity is a powerful tool to improve the standards of living of people & to enhance the quality of work life (QWL) Ergonomics is concerned with man & his working conditions. Ergonomics aims at providing comfort & improved working conditions so as to channelize energy, skills of workers into consecutive work. This account for increased productivity, safety reduces fatigue. Ergo data is given when manual operator involved to do operation, so this input is given regards how the standard of ergo data is. Ergo data provides information of loading height, working safety, zone of operator etc.

The final assembly of an automobile involves tasks of complex nature. These processes are on the least priority for automation Manual labor is best suited for assembly operations with the aid of minimal level of automation. All the processes have to be improved continuously in order to reduce the costs and increase productivity. The workers attain various postures, exert force and works continuously in cycle time to accomplish the assembly task. Working along automobile assembly lines is characterized by repetitiveness.

Ergo data is studied to identify and quantify ergonomics working postures that contributed to the serious development of muscle skeleton injuries and thus investigated possible contributory their related causes. Below figure show ergonomically correct seating position while working.

7. What do you understand by Weld study?

It includes information of weld gun detail, weld matrix & weld points. There are two types of weld points geo weld point re-spot weld point. Geo weld points defines the geometry of part & re-spot do all other remaining weld points also add strength the geo weld points. Weld study consists of spots in case of spot welding fixture that gives us the position of spot in the form of coordinates. It is most important input that we get from customer. These are the points where the panel is welded. The spots can be geo spots or re-spots shown in figure

The front door inner panel and side bracket of GM sedan car are to be spot welded as shown in Figure 1. The previously spot welded inner panel assembly is then welded with the cross bracket as shown in Figure 2. The work cell and modular fixture designed must be compatible for both the assemblies to be spot welded.

Weld spots for each weld assembly are highlighted in Figure 1 and 2 as WP1, WP2, WP3 and so on. Weld points are the location on which spot welding will be carried out on the automobile sheet metal components. The Weld points forms the base for fixture design, the clamping plan & locating plan are done based on the weld spot distribution. The weld spots for Front door inner panel - side bracket assembly are located as shown in Table 1 with respect to the body line of car.

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

Percentage completion criteria are followed in the designing stage & dispatch stage of welding fixture. The percentage completion criteria contain the current status of a task, expressed as the percentage of the task's duration that has been completed. You can enter percent complete, or you can have Project calculate it for you based on actual duration. It is followed in designing stages & dispatch stages of the welding fixture. It ensures that how much task that we have decided to complete within the stipulated time is complete or not & how much of it is rest to complete & whether it is going to be complete or not in given time.

0-25%- INPUT & CONCEPT DESIGN: This is initial stage of project. Input data provided by customer like functional requirement, customer standard etc. & after studying those inputs the concept of fixture design is created. After completion of these task about 25% of work completed.

25-40%- CONCEPT APPROVAL & SIMULATION CHECK: As concept of fixture design is created & simulation checked it is sending for customer approval. Customer will study simulations & gives his approval. If there are any changes required, then it has to do accordingly & again submit for approval. The concept design approval from the customer after study of simulation contributes only 15% of total design work. But with completion of this task 25-40% works completed.

DESIGN FREEZING & DETAILING- 40 TO 85%: This phase involve design freezing after approval of concept design. Freezing means finalizing concept design. Then next step detailing as per customer standard template with completion of this stage, almost 85% of work is completed in designing stage.

CHECK & FINAL DISPATCH- 85 TO 100%: After detailing the quality checking team starts inspection of all the data & it will dispatch to the customer if it is ok as per customer standard. If there is in error in drafting it will create issue or mistake in manufacturing stage.

Thus, a percent completion criterion helps us to know where we are in design process.

9. Brief about "Output" in design?

• It includes data to be given to customer after completion of design stage. The output is 3D models & 2D drawings of the tool.
• In the fixture element design output contains detailed design of locators, detailed design of clamps, detailed design of supports, positions of locators, positions of clamp, positions of supports if any, type of locators, types of clamp, types of supports, clamping forces & supports.
• There are two types of tools in fixture design unitized tool & non unitized tool In unitized tool there are multiple units on common base for e.g. geo fixture, re-spot fixture, checking fixture, hemming station etc. Unitized tools require two types of sheet key sheet & layout sheet. Non- unitized tools that can stand alone can be detailed completely on a layout sheet. e.g. Rack, take out trolleys, turn tables, grippers etc.
• Key sheet: an index of units & their placement on the tool base. Key sheet shows placement & location of that particular unit on tool base where exactly & exact position of tool base. Key sheet is showing orthogonal or isometric view of that entire component.

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

STRUCTURING A DESIGN TREE:

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

• Every company, every customer has different standards of their own structure design tree.
• So they will be giving a template on how the structuring and detailing of the design is done. And you have to follow that particular designing or structuring of the tree.
• In the design tree itself if we mentioned that particular name, wherever that part is we can easily know that this part belong to this zone or This station or this assembly on particular unit. So this helps us to avoid errors during the design study, manufacturing assembly and inspections.
• Structuring a design tree is actually to avoid all the errors, which might come during manufacturing assembly, or either in house inspections as well.
• If the part, or assembly are not named properly, or design tree is not structured properly, it will create confusion to understand the design and may create major possibilities of making an error.
• Every part, every component should be named according to their procedures.
• If we did a mistake or renamed the entire standard parts from the customer as a design part, now the customer is going to manufacture the entire part again from the scratch, but he already have that product in his itinerary. But extra cost, extra time and not feasible. This is also known as an error which is actually going to increase the cost of the entire assembly as well.
• Naming a fixture or a unit or a part gives the information as to which project zone or assembly do they belong.
• If we name the part properly or name the fixture properly it'll actually tell which unit or which assembly or which zone or in which station it actually belongs.

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

UNITS: In units they are two types one is unitized tools and non-unitized tools.

UNITIZED TOOLS: Unitize tools are basically tools which are a part of multiple units or multiple tools inside of it these are the tools which have to be represented by two formats key sheet and layout sheets. Unitized tools are basically two types, Simple units and Complex units.

NON UNITIZED TOOLS: Non unitized tools are basically one unit itself, which is basically don't have any process functionality to it is just to keep component on it as a stable, like grippers turntable stands, etc.

SIMPLE UNITS: Simple unit will have a very simple design to it, then the approach of the designing and manufacturing is also will be very simplistic like rest unit.

REST UNIT: Rest unit is basically a unit where the component is tested, there is no upper clamp to it, there's no force applied to it. There is no cylinder attached to it, it's just, usually it will have a riser a blade and few rest mylers.

FIXED PIN UNIT: Fixed pin unit are basically units which has a pin which is already fixed it cannot be moved.

RETRACT PIN UNIT: Retract pin unit are the opposite of the fixture which can be moved up and down, so it can be retracted till a certain distance.

ROUGH LOCATOR UNIT: Rough locators are usually used in loading and unloading of that particular panel.

SENSOR UNIT: Sensor units are used in actually sensing whether the panel or a particular component is there or not for example If we are assembling component of nine parts or 10 parts or eight parts, they'll have that many sensors, so that every component will have different its own sensor attached to it.

BASE UNIT: Basic unit where all the units have to be mounted.

COMPLEX UNITS: Complex unit, like slide unit as an example of a complex units that design in itself a little complex in design.

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 juiced up right as for storage kind.

12. Describe Fixed Pin units & their purpose?

Fixed Pin Unit is a unit designed to locate the car panel using pins and below are the different parts of a fixed pin in general.

• In the Fixed unit consists of pin, pin retainer, shims, block blade or adaptor plate and riser.
• The totally different standards so same, a pin, pin retainer blade, or a block, so here they have replaced the block with just a single blade. And this is also.
• Usually in the industry they tend to use the shims which are of smaller size. That’s where they're manufactured like this always preferred as much as less material as possible. That's why we design it as small with these kinds of shapes.
• Retractable pin is a unit design and it is located in the car panel using pins, which has same function as the fixed pin unit, but the entire pin package part will be mounted on the retractable pneumatic cylinders.
• So this is the pneumatic cylinder which is responsible for retracting the pin. So it has also same parts up in Shims or spacers again with the both sides pneumatics single rod retractable cylinder and the riser.
• Usually in the industry they tend to use the shims which are of smaller size. That’s where they're manufactured like this always preferred as much as less material as possible. That's why we design it as small with these kinds of shapes.

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

SHIMS: A shim is a thin and often tapered or wedged piece of material, used to fill small gaps or spaces between objects. Shims are typically used in order to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gap between parts subject to wear.

RISERS: Riser is a structure generally used to mount the toggle clamp and rest, clamp mylar and location pin.

• It is not necessary to have one riser where all the parts of clamp or rest or location units are mounted.
• Generally risers are either made of plate fabrication or plate and tube welding together or from single gas cut plate.

BLOCKS: Blocks (red for representation) are versatile blocks that can be machined to any desired fixture component. Because they come are a blank block, the possibilities are endless. Adding new tap holes or grinding down to your specifications is quick and simple

SENSOR UNIT: Sensor unit is a unit designed to sense the car panel by using electrical sensors, the signal from the sensor will fed to a PLC which is our programmable logic controller and sort of the next process will be executed by this signal.

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

REST UNIT: Rest Unit is a unit designed to rest /Support the car panel using NC blocks/Mylar/Rest and below are the different parts of a res unit in general.

• Simple unit which has a raiser and a normal blade a spacer, which is the shims and the rest mylar.
• You can just manufacture the restaurants there and you can use the same blade as the same razor.

NC BLOCK: NC blocks (red for representation) are versatile blocks that can be machined to any desired fixture component. Because the come as a blank block, the possibilities are endless. Adding new tap holes or grinding down to your specifications are quick and simple.

SHIM: A shim is a thin and often tapered or wedged piece of material, used to fill small gaps or spaces between objects. Shims are typically used in order to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gap between parts subject to wear.

RISERS: Riser is a structure generally used to mount the toggle clamp and rest, clamp mylars and location pin.

• It is not necessary to have one riser where all the parts of clamp or rest or location units are mounted.
• Generally risers are either made of plate fabrication or plate and tube welding together or from single gas cut plate.

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

SENSOR UNIT: Sensor unit is a unit designed to sense the car panel by using electrical sensors, the signal from the sensor will fed to a PLC which is our programmable logic controller and sort of the next process will be executed by this signal.

• So our sensors are basically used to sense the particular car panel. Now, the signal which gets from this sensor will be fed to the PLC, the PLC will decide whether the signal from the component or the assembly actually has the particular car panel or not.
• If it does not have it will not execute the next process, and it will stop the entire process that itself until the panel is loaded.

FUNDAMENTALS OF SENSOR UNIT DESIGN: Every single loose panel, which is being welded in a tool, should be sensed. So every single panel that we are going to assemble in that particular panel.

• For example, If we are using nine different panels to assemble in one panel. Every single one of those panels should have one sensor attach to it.
• Each panel should be sensed by one or two sensors depending on the size of the panel preferred to be in diagonally opposite ends of the panel.
• If a component is really small, we don't have to use two or three sensors for that you can just use one sensor, which will detect that particular panel.
• If the panel is really big, we will use two sensors towards the opposite directions of each to sense their particular panel.
• So every sensor should be mounted in three directional adjustable ways in general.
• Sensors Detect in Three Different Movements in that first one is upward and downward movement of the sensor. The second one is from left and right movement, and direction so all three directions.
• Sensor manufacturers is IFM, Pepperl-Fuchs and Omron, etc.

TYPES OF SENSORS USED IN GENERAL

PROXIMITY SENSOR: Proximity sensor is used in cell phones as well to detect a particular component. So, proximity sensors are range from 5 to 6 mm to 8 to 10 mm.

LASER SENSORS: Laser sensors are used for bigger sensing the distance, if the component cannot be near the panel. It has to be farther away from the panel, then you will be using laser sensor.

PHOTO ELECTRIC SENSOR: Photo electric sensors this is basically a proximity sensor and this can be utilized as a laser centered sensor and this is an example of a photoelectric sensor.

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

ROUGH LOCATOR: Rough locator is a part which is designed to guide the operator to locate the car panel on the pin accordingly rough locator can b of standard parts or make part. The locators are used in loading and unloading the pan. These are very handy while orienting the part properly, so it will actually guide the entire the operator to load the panel in a particular orientation.

FUNDAMENTALS OF ROUGH LOCATOR DESIGN:

• Rough Locator should be placed at the edge of the component or car panel, which has to be guided.
• So these are four carriers has to be placed at the edge. These are the edges of the entire panel, where the rough locators are the locating pins. So by these locating pins, you can either restrict the movement of the entire panel as well so placed in the same angle of the car panel edge with a minimum distance of 2 to 5 mm from the edge of the car panel.
• Rough Locators should not touch the car panel, so that it should not damage the panel by loading and unloading.
• Rough locator should be designed in such a way that the panel will come from top to bottom and then it will be guided in the same direction.
• Rough Locators cannot be in just one angle it should be at the angle where the panel edge is supposed to be.
• Rough locator should start guiding the panel before 10 to 15 mm to the start of the pin engagement is one of the important parameters to consider.
• Rough locators should start guiding the panel downwards, before even the pin unit, engage in the panel.
• 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.

17. What is a Base unit and describe it's parts?

BASE UNIT: The base unit is a unit designed to mount all the other units like time unit, pin unit , etc. of the tools and also other parts necessary of the tool of pneumatic valve box, trunking cable path will also be mounted on the base unit.

All the units are basically like clamp unit, pin unit, rest unit And the Rough locators, everything will be mounted on the base unit.

VALVE BOX: A valve box is basically a box which supplies air to all the other pneumatic cylinders. 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 I 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 holes cover 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.

18. What is a Dump Unit and what are its functions?

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

FUNCTIONS OF DUMP UNIT: If you have particular constraint and you cannot assemble in a normal way to use this use it in different ways again it has same dumb cylinder and it has open position and closed position and it has Clamp Cylinder Unit too. That is why this is very complex and design.

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

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

SLIDING UNITS: 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 only.

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.