Week 3:- BiW Fixture Design Methodologies Challenges

1.What is Design Methodology?

DESIGN METHODOLOGIES:

In this methodology we learn about three design processes, we're going to study how do we proceed while doing a design. And one of the things that we take care of structuring or design tree so we'll be learning how to structure the design tree, and how to name the particular component or particular assembly, or the part of an assembly, which is very easy to read and very easy to understand.

Design methodologies are nothing but the steps followed during the concept designing stages of fixture design. The various stages of design methodologies are,

• Purchase order.
• Inputs from customer.
• Percentage of completion criteria.
• Design outputs.

1. Purchase Order:

A purchase order (PO) is a commercial document and first official offer issued by a buyer to a seller indicating types, quantities, and agreed prices for products or services. It is used to control the purchasing of products and services from external suppliers. Purchase orders can be an essential part of enterprise resource planning system orders. Purchase order is a order from customer for start of the work. After offer has been finalized customer will be releasing the LOI/PO(Purchase Order).

Once PO is released we have to start the work.

After PO from the customer we have to prepare the schedule.

Purchase order is the confirmation document from customer to proceed the committed work for them.

2. Inputs from customer:

The inputs from the customers are as below,

Functional Requirements:

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

Preferred standards:

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

Car products:

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

Layout:

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

Ergo Data:

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

Weld study:

Weld study is the important inputs given by the customer. It gives details about the study of particulars gun that we use for welding. Also the dates like no/ of weld, position of weld in the components will be given. In short, weld study includes weld gun details, weld matrix & weld points.

Standard detailing templates:

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

3. Percentage of 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 criteria like a probability to when we can complete the entire fixture design.

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

Inputs & concept design – 0 to 25%

Concept approval & simulation check – 25 to 40%

Design freezing & detailing – 40 to 85%

Check & final dispatch – 85 to 100%.

The above mentioned percentage are the percentages of stage wise completion criteria of the projects.

4. 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 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.

 

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

The inputs required from the customer to start designing a fixture:

• Fundamental requirements.
• Preferred standard components.
• Car products.
• Ergo – data.
• Weld study.
• Standard detailing templates.

1. Functional Requirements:

The purpose or the function of the fixture will be given as inputs from the customers like what are the process the fixture is going to do i.e welding(spot or seam weld), gluing, riveting, hemming or whether it is a checking fixture or a storage racks etc.

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

2. Preferred standards:

As we know different companies follow different standards, we will be following the standards, we will be following the standards followed by the customers. By following standards the time of designing and manufacturing of parts will be saved, which will be automatically minimizing the time of the projects.

As for the standards parts, it can be easily replaced from the used fixture to the new fixture which reduce the cost.

Some of the preferred standard components used in BIW fixtures are given below,

Standard like ABB, NAAMS, DESTACO, ZYTRAN, TUNKERS are used in design & manufacturing of fixtures.

Standard parts like Risers, L-blocks, retainers, pins, NC blocks, Shims, etc.

Components like clamps, cylinders, slides, switches, sensors, etc.

Weld guns, Tip dressers, Tool changers, etc. tip dressers are to sharpen the tip of the tools whereas tool changes are used in robots to do various process. As robots are too costly, tool changers are used.

ABB – It is a Robots manufacturing company.

Some example of description of standard robots are, Robust IRB 7600 robots, which can, hold the panels securely and accurately in place while IRB 6640 robots perform the welding.

The below picture shows the welding line is installed at great wall motors (GWM) recently opened and internationally acclaimed automotive plant in Tianjin, china. One of the factory’s most highly publicized and productive manufacturing lines is the ABB welding line, which comprises among other things a fleet of ABB robots and patented ABB framing and hemming technologies.

3. Car Products:

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

GD&T: It provides information of locating pins, rest, clamp, damp & slide unit informationof each station. Also includes the information of sequence of openings of clamps, dumps & slide stroke information.

Part lists: It gives the lists of parts which are going to assembled in the fixture. The list contains the information of part number, part name, revision of fixture, part thickness, etc.

Clamp plan: Clamp plan provides the information of location of pins, Rest units, clamp unit, dump etc. It is the important input from customer. The clamp plan/position should not be changed without the knowledge of customer.

3D cad file: The 3D model of the car part will be given from customer. From that 3D model we will be developing our fixture design process. The 3D cad file will be in the format of step file (stp) or IGES file (igs).

Product assembly process sheet: It gives the information of stage wise assembly process like how the parts move from one assembly process like how the parts move from one assembly station to other after the completion of joining process.

4. Layouts:

Layout shows the entire assembly plan to understand the process.

Layout provides the information of flow of parts, station pitch, robot stations, accessories like tool changers & tip dressers, sub assembly links, plan form height, loading/unloading sequence/height.

5. Ergo Data:

As same as preferred standards, different companies follow different standards of ergo data. We have to follow the customer standards of ergo data.

The inputs of ergo data will given by the customer mostly in case of manually operated fixtures/manual fixtures.

The ergo data is mainly used to make the operator comfortable which may leads to improve the efficiency in cycle time & production.

Rivaa-Global - Manufacturing Engineering Services, Digital Manufacturing

Ergo data provides inputs like platform height, maximum & minimum reach from operator to fixture, maximum & minimum height of the fixture, whether the child parts/assemblies are visible while clamping or loading & unloading.

Also provides information’s like loading height, working safety zone of operator, etc.

6. Weld Study:

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

Also the data’s like No. of weld, position of weld in the components will be given. In short, weld study includes weld gun details, weld matrix & weld points. Generally weld points will be given in spheres.

7. Standard detailing templates:

These inputs include the detailing of 2D cad drawing as per the customer standards.

So we have to follow the detailing templates as per the customer standards.

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

Inputs we get from car products include;

• GD&T.
• Part list.
• 3D cad file.
• Clamp plan.
• Product assembly process sheet.

1. GD&T:

GD&T – Geometric Dimensioning & Tolerance.

It provides information on locating pins, rest, clamp, damp & slide unit information of each station. Also includes the information of sequence of openings of clamps, dumps & slide stroke information.

Tolerance important:

Assemblies – Parts will often fit together if their dimensions do not fall within a certain range of values.

Interchangeability – If a replacement part is used, it must be a duplicate of the original part within certain limits of deviation.

The relationship b/w functionality and size or shape of an object varies from part to part.

When to use GD&T:

• When part features are critical to a function or interchangeability.
• When functional gaging is desirable.
• When datum references are desirable to ensure consistency between design.
• When standard interpretation or tolerance is not already implied.
• When it allows a better choice of machining processes to be made for production of a part.

Datum in GD&T:

A datum is theoretical exact plane, axis or point location that GD&T or dimensional tolerances are referenced to you can think of them as an anchor for the entire part, where the other features are referenced from A DATUM feature is usually an important functional feature that needs to be controlled during measurement as well.

2.  Part lists:

It gives the lists of parts which are going to assembled in the fixture. The list contains the information of part number, part name, revision of fixture, part thickness, etc.

3. 3D cad files:

The 3D model of the car part will be given from customer. From that 3D model we will be developing our fixture design process.

The 3D cad file will be in the format of step file (stp.) or IGES file (igs.) or sometimes it may be in part file (prt.).

4. Clamp plan:

Clamp plan provides the information of location of pins, rest units, clamp unit, dump, etc.

It is the important input from customer. The clamp plan/position should not be changed without the knowledge of customers.

It gives the detail of the exact position of the clamping units.

5.  Product assembly process sheet:

It gives the information of stage wise assembly process like how the parts move from one assembly to other after the completion of joining process

It shows the sequence of operations/process to be done in a part or a panel.

Also what are the parts to be joined with the panel will shown in sequence.

From this sheet we can trace out the pending process which has to further go on for completion of part.

From this product assembly process sheet designer can understand the sequence for designing the fixtures.

4.What is the Clamp plan?

Clamp:

• A clamp is a fastening device used to hold or secure objects tightly together to prevent movement or separation through the application of inward pressure.
• Essential requirements of clamps:
• All clamps must fulfill four essential requirements. They are,
• The work piece must be held rigid while undergoing operations.
• The time required for loading / unloading the tool must be as short as possible, which means the clamping device must be quick acting.
• when subjected to vibration, chattered, heavy pressure the clamping must be positive.
• The clamp must not damage the work piece.

Clamp Plan:

• Clamp Plam 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 we 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 happens 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.
• we should never change the vent position or the clamp position without asking it So always be vary 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?

THE PURPOSE OF THE LAYOUT:

The purpose of the layout is to understand the information about where the fixture & robots are been placed, working area covered by the robot, what are the fixtures assigned for the robots to do the process, etc. layout shows the entire assembly plan to understand the process.

• The circle around the robot is the swept area of the particular robot which shows the reachability of the robots particularly with the confine circle.
• Layout provides the information of flow of parts, station pitch, robot stations, accessories like tool changers & tip dressers, sub assembly links, plat form height, loading/unloading sequence/height.
• 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 reachebility of the robot which is confined to the particular circle.

Flow of parts: It shows the flow of the parts/panel in the assembly line or shop floor like how component move from one station to other station after the completion of process.

Station pitch: The distance between two stations is known as station pitch. It shows the space constraints between the two stations, which shows in layout.

Robot stations: It shows the position where the robots & their accessories placed, which is shown in the layout.

Sub assembly link: Sub assembly link is nothing but the link 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.
• The layout providing the above information like flow of parts, station pitch, robot stations, etc used to understand the working process of robots, what are the fixtures assigned for the robots, space constraint, etc.
• By considering the layout, the designers can develop the concept sketches of fixtures without any clash in the assembly lines.
• One of the main purpose is to get the information about the space constraint which helps to develop the robotic cell without any clash during working.

6.What is Ergo data?

ERGO DATA:

Ergo data is nothing but the data or inputs which give the human factors engineering data, between the operator & his working environment. Before detailing about ergo data we should know about ergonomics in detail.

ERGONOMICS:

Ergonomics also known as human engineering & human factors engineering is the scientific study of the relationship between man and his working environments.

OBJECTIVES OF ERGONOMICS:

• The fundamental objective of the study of ergonomics is to optimize the integration of man & machine so as to improve the productivity & accuracy.
• In short, the objective of ergonomics is designing for human use & optimize working & living condition.
• Two main objectives of ergonomics are:
• To enhance the efficiency and effectiveness with which the work is carried out so as to increase the convenience of use, reduced errors & increase in productivity.
• To enhance certain desirable human values including safety, reduced stress & fatigue and improved quality of life.

Ergonomics involves the design:

• A work place suitable for the worker.
• Machinery & controls, so as to minimize physical strain on the worker to enable the improvement in the efficiency.
• An environment for performing a task most effectively and conducive.
• A conducive task & work organization.
• Benefits of Ergonomics:
• Improved working condition.
• Reduce physical workload.
• Improved work postures.
• Reduced efforts of certain movements.
• Better reading instrument displays, handling of machine levers & Controls.
• Reduced unnecessary information recall efforts.
• Below, I have given a basic example of ergonomics in the workstation.

ERGO DATA:

• Ergo data is nothing but the data or inputs which gives the human factors engineering data, between the operator & his working environment.
• Ergo data is mostly needed while there is a need of manual operator/operation.
• Ergo data will be given from customer as per their standard. Every customers follow different ergo data standards.
• As per customer standards, we have to consider the ergonomics in the fixture while designing.
• From ergo data we get the details or inputs related between the operator and his working fixture.
• The ergo data is mainly used to make the operator comfortable which may leads to improve the
• efficiency in cycle time & production.

7.What do you understand by Weld study?

WELD STUDY:

• Weld study is the important inputs from the customer.
• It gives the study of particular gun that we use for weld, No. of spots to be welded, sequence of weld, position of weld in the components.
• In short, weld study includes weld gun details, weld matrix & weld points.
• Generally the weld points will be given in spheres.
• Red sphere represents the Geo spot weld points whereas Green sphere represents the Respot weld points.

The weld points are classified as,

Geo weld points:

• The Geo weld points are which is planned in the Geo fixture.
• These weld will determine the position of the panels as per the given data in drawing.
• The geo weld points are represents in red sphere in the weld study inputs given by the customers.
• Respot weld points:
• The respot weld points are planned in the respot tool.
• These weld will determine the strength/stiffness of the panel/components.
• The Respot weld points are represent in green spheres in the weld study inputs given by the customers.

 

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

 

It is used in the design and dispatch stages of the welding fixture. It shows the number of tasks completed in the project and we can make sure whether the work is being done as per the planned schedule.

Different stages in a project have a different percentage as follows

1. Input and concept design 0-25%
2. Concept approval and Simulation check 25-40%
3. Design Freezing and detailing 40-80%
4. Check and Final Dispatch 80-100%

 

• Input and concept design 0-25%

 It is the initial stage of the project where we get all the design inputs from the customer and based on those inputs a design concept of the project will be created.

• Concept approval and Simulation check 25-40%

Once the concept is designed it is sent to the customer for approval and the simulation checks are done for the given design and looked for the feasibility of the design.

• Design Freezing and detailing 40-80%

The changes are done to the design if the results of the simulation checks force us to do or if there any changes suggested by the customer. After all these changes are done the design is fixed and the detailing to the design starts

• Check and Final Dispatch 80-100%

After the detailing, it is sent for the quality inspection and finally dispatched to the customer.

9.Explain it in detail Brief about "Output" in design?

• The percentage completion criteria are followed in the designing stages & dispatch stages of welding fixtures.
• This percentage completion criterion is followed to trace the project whether it matches the committed date given to the customer for hand over the projects to them.
• Also it helps us to identify the stages in the projects like how much the project is completed and what are the further stages are in pending, to complete which helps us to complete the projects on the committed time and date.
• The percentage completion criteria are divided into four stages to identify the percentage of the completion of work.

The four stages of percentage completion criteria are as follows,

• Input & concept design.
• Concept approval & simulation check.
• Design freezing & detailing.
• Check & final dispatch.

1. Input & concept design:

• If the project is in the stage of Input & concept design then the percentage completion criteria of the project will be between 0 – 25%.
• After the completion of input & concept design then the project will be moved to concept approval & simulation check which is the second stage in percentage completion criteria.

2. Concept approval & simulation check:

• If the project is in the stage of concept approval & simulation check then the percentage completion criteria of the project will be between 25% - 40%.
• After the completion of concept approval & simulation check then the project will be moved to design freezing & detailing which is the third stage in percentage completion criteria.

3. Design freezing & Detailing:

• If the project is in the stage of Design freezing & detailing then the percentage completion criteria of the project will be between 40% - 85%.
• After the completion of design freezing & detailing then the project will be moved tp check & final dispatch which the fourth & the last stage in percentage completion criteria.

4. Check and final dispatch:

• If the projects are in the stage of check & final dispatch then the percentage completion criteria of the project will be between 85% - 100%.
• After the check the project will be finally dispatched successfully to the customer.

Output in Design:

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.

The output is 3D models and the 2D drawing of the tools

1. Unitized Tools
2. Non-Unitized Tools
3. 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 - An index of units and their placements on the tool base. It will have an orthogonal view of the fixtures including a numbered balloon drawing mentioning the units.

Layout sheet - A detailed drawing of individual units to include all of their components.For the Non unitized tool no need of key sheets. As they can stand alone, the drawing can be detailed completely on a layout sheets.

So, it is basically an index of units and placements on the tool base, so the key sheet going to show you the placement and the location of that particular tool on the tool base where exactly the tool is placed. And what is his exact position in a particular place.

2. Non-Unitized Tools:

• Tools that can stand alone and can be detailed completely on a layout 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 use to layout sheet and complete the entire documentation of the particular component. So this is as known non unitized tools

The Design Output Should Compile Following Points:

• Approved standard components are to be used wherever possible.
• Design must be as simple & economics as possible.
• Design must be comply with all current safety & ergonomic requirements.
• Design must provide for controlled & damage free handling of product.
• Adequate error proofing provision must be incorporated into each design by proving proximity switches, rough locators, etc.
• The weight of the moving parts must be kept to a minimum while maintaining maximum strength.
• Frames & structures are to be simple & study.
• Design clearance & accessibility for routine maintenance & service.
• Motion control must be considered on any moving equipment’s.
• Designer is responsible to validate clamps & weld guns.

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

Structuring A Design Tree:

• Structuring a design tree implies to 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/unit, it belongs to.
• This helps us to avoid the errors during design, 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 types or different types that are being used in the assembly.
• While start designing a fixture, the first unit will be the base unit.
• In structure tree all the manufacturing parts should be first and the standard parts should be at the last.
• Structure tree helps to study or understand the parts in the assemblies easily.
• Steps to structuring a design tree:
• Step 1: Create new à Product à click OK (by clicking ok now you will enter into a product window)
• Step 2: Then right click product in a structure tree à go to properties à rename in part number (As we created a product we have to mention the total assembly name of the fixture) à click ok.
• The naming of the assemblies / parts / units have certain standard procedures, which I have clearly explained below.
• The product name is title of the fixture. The renamed titled should be à P001_Z03_ST09_00_00_R
• P001 – represent the project name.
• Z03 – Zone name.
• Panel name will also be mentioned in some case.
• ST 09 – Station name / J03 – Jig name will be mention sometimes.
• 00 – unit name.
• 00 – Part number.
• R/L – is representing the right hand side / left hand side of the panel.
• The other renamed title explained in video is
• H1L_19A – Project name.
• RRFRA – Panel name.
• JG3 – Jig name/number.
• 00 – unit name
• 00 – Part number.
• R – Indicates right side.

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

Units:

• A unit is a device that has a specified function, especially one forming part of a complex mechanism.
• A welding fixture is assembly of different types of units.
• As name refers, the different units will be only seen in the unitized tool.
• A units are classified into two, they are,
• Simple unit: In a simple welding fixture, the combination of these different units will be seen.
• Rest unit.
• Fixed pin units.
• Retract pin units.
• Rough locator unit.
• Sensor unit.
• Base unit.

Complex unit: In a complex welding fixture, in addition with some of the simple units these complex units will also seen

• Slide unit.
• Dump unit.

Five Types Of Units:

• Base unit:

Base unit is the unit designed to mount all other units such as clamp unit, pin unit, rest unit etc., of tool, also other parts necessary for a tool like pneumatic valve box, trunk cable path will also be mounted on to be a base unit.

12.Fixed pin unit:

• Fixed pin unit is a unit designed to locate the car panel using pins.table
• Pin, pin retainer, shims, blocks, blade, riser are the part of fixed pin units.
• Pin retainer is used to hold the pin firmly.
• Typically, the locating pins are used to locate a body part in a position sufficiently accurate to execute a welding process.
• The body part is constrained by a set of appropriately locating pin so total constraint by locating pin should be fully constrained at all times to prevent any movement.

Retractable pin unit:

• Retractable pin unit is unit designed to locate the car panel using pins, but the entire pin package parts will be mounted on the retractable pneumatic cylinder as shown in below fig 3.
• Retractable pin unit is the opposite of fixed pin unit which can be moved up & down also which can be retracted till certain distance.
• It is mainly used for unloading the complex panel after welding.

Clamping unit:

• Clamp unit is a unit designed to clamp or hold the car panel with NC block / Mylars by using a pneumatic clamp cylinder.
• Clamping unit is used to clamp the part which is to be welded after location using pin unit.
• Clamping is achieved with the help of pneumatic cylinders and clamp arms.
• Clamping arm, finger, rest, shims, standard riser, pneumatic cylinder are the parts of clamping unit in general.

Slide unit:

• Slide unit is found mostly in complex fixture, where the sliding mechanism will be involved.
• This type of unit used when there is some space constraints.
• Guide block, guide rail, position lock unit, stopper block, sensors are the parts of slide unit in general.
• Guide block & guide rail helps to the guide the slide unit. The rail should always be covered to protect against weld spatter & dust by a bellow or a sheet metal cover.
• Position lock unit helps the slide to be locked/clamped in the working position.
• Stopper block helps to stop/control the entire moving of a slide unit from certain distance, which is placed at the end of the guide rail.
• Sensors – The two end limits to be sensed externally by a proximity sensor.

PURPOSE OF FIXED PIN UNIT:

• As by 3-2-1 locating principle, the introduction of two pins helps to arrest the 6 degrees of freedom (4 axial & 2 radial movements) whereas other 6 degrees of freedom are arrested by introducing minimum three supports.
• Typically, the locating pins are used to locate a body part in a position sufficiently accurate to execute a welding process a welding process.
• The body part is constrained by a set of appropriately locating pin so total constraint by locating pin should be fully constrained at all times to prevent any movement.

13.Describe Fixed Pin units & their purpose? What are the different parts of a fixed unit?

DIFFERENT PARTS OF THE FIXED PIN UNIT:

The different parts of the fixed pin units are a

1. Pin:

• It is used for the location purpose of the panel. Typically, the locating pins are used to locate a body part in a position sufficiently accurate to execute a welding process.
• The body part is constrained by a set of appropriately locating pin so total constraint by locating pin should be fully constrained at all times to prevent any movement.
• There are dozens of styles of locating pins that can be utilized in a design. One of the most common pins is a stepped pin with either small or large head.

2. Round Pins:

These can be Screw secured (PNRS) or Grub Screw secured (PNRG) or Thread secured (PNRT) for Prototype build only. One of the most common pins is a stepped pin with either small or large head.

Diamond Pins:

The Diamond Shape is a critical feature that helps with machining inaccuracies and smoother locating operation. When two round head pins are installed onto one plate, the distance between two mounting holes must be extremely precise and even then, the work piece will not be placed on the base as easily as it would with the use of a diamond shape pin. These can be Screw secured (PNDS) or Grub Screw secured (PNDG) or Thread secured (PNRT) for Prototype build only.

2. Pin Retainer:

Pin retainer is used to hold the locating pins firmly. Pin retainer is designed to hold the pin in its place and is also used as a rest for the pin. A counter hole drilled on which pin is fit

3. Shims:

• In general, 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 gaps between parts subject to wear.
• Shims are the small parts which comes with the thickness of 0.1mm, 0.2mm, 0.5mm, 1.0mm etc.
• These will compensate the stack up tolerance which reflects at the mylars.
• We give tolerances to all parts of the fixture. Due to this tolerance the mylars will either lift up moves down from its defined position. To adjust the mylars for getting the defined position we use shims.
• Shims will be added above the mylar for adjusting according to tolerance.

Types of shim:

• Wood shim.
• Stone shim.
• Plastic shim.
• Metal shim.
• Paper shim.

4. Riser:

Riser is a manufacturing part used to raise / height the assemblies of fixture.

One end of the raiser will be attached to the blade.

Raiser can be of two types. They are,

‘L’ type risers.

Square tube risers.

L TYPE RISERS: L type risers are of welded type. Where the stiffner will be added at the centre for support, as shown in the below figure the wedge shaped structure is known as stiffner which is used as a support/to withstand load.

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

PURPOSE OF MAKING A REST UNIT:

• Rest unit is unit designed to support car panel using Mylar/ NC block/ rest. Component is rested only, no upper clamp or force applied there.
• 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 unit to reduce the cost of the overall project.
• It can be combined with 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 combined together in one unit to reduce cost.
• There is no cylinder attached to it. It has rest Mylar, blade & riser & below is different parts of rest unit. Rest unit is also divided into simple support unit, multiple support units & retractable support unit.

 

PARTS OF REST UNIT:

The parts of rest unit are as follows,

• NC block/mylars.
• Shims

NC blocks/mylars:

• Mylars are the part which are holding the panel from top & bottom.
• It is a jaw type, during welding it wont deforms from its position.
• It is also known as fingers.
• It wont allow the deformation of the part due to welding stresses.
• Mylars are of two types, they are
• Clamping mylars
• Resting mylars
• Only resting mylars can be seen in rest unit.
• The panel which rests on the part is known as resting mylars.

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

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 the signal.

FUNDAMENTALS TO DESIGN A SENSOR UNIT:

• Every single loose panel which are being welded in a tool should be sensed.
• Each panel should be sensed by 1 or 2 sensors depend on the size of the panel, preferred to be in diagonal opposite ends of panel.
• Every sensor should be mounted in a 3 direction adjustable way in general.
• We should try to minimize the size of sensor as much as possible.
• Some major sensor manufacturers are IFM, Pepperl – fuchs, sick, OMRON, etc.

Types of sensor used in general:

Proximity sensor:

• A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation and looks for changes in the field or return signal.
• The object being sensed is often referred to as the proximity sensors target.

Laser sensor:

• These laser distance sensors use a focused, coherent light to measure distance to a target object. In factory automation applications, the target is usually a product or a machine elements. They detect any solid object and produce an output proportional to the measured distance – independent of material, color and brightness.
• The high resolution output provided by laser distance sensors is used to provide position or displacement, usually to the input of some type of industrial controller such as PLC. The output signal is often highly accurate, and it includes temperature compensation to enhance stability.
• There are several types of laser distance sensors including diffuse, background suppression and retroreflective. These sensors use CMOS or transit time technologies providing accurate distance measurements.

Photoelectric Sensor:

• A photoelectric sensor or photo eye is an equipment used to discover the distance, absence or presence of an object by using a light transmitter often infrared and a photoelectric receiver.
• They are largely used in industrial manufacturing.
• There are three different useful types opposed, retro-reflective and proximity sensing.

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

ROUGH LOCATOR UNIT:

• Rough locator unit is a unit designed to guide the operator to locate the car panel on the oins accordingly.
• A rough locator can be standard part or make part.

 

 

 

THE BASIC FUNTAMENTALS TO CONCIDAR WHILE DESIGING A ROUGH LOCATOR:

• Rough locator should be placed at the edges of the car panel, which has to guide.
• Rough locator should be placed in the same angle of the car part edge with a minimum distance of 2 – 5 mm from the edge of car part.
• Rough locators should guide the panels in a pin assemble direction in general.
• Rough locators should start guiding the panel before 10 t0 15mm to the start of the pin engagement.
• Rough locators should be designed with entry angle for car part entry as shown in the above figure.
• Rough locators should be designed with two slots to mount for easy adjustment in general.
• The slots should be in the direction of car part guiding.

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

BASE UNIT:

Base unit is the unit designed to mount all the other unit like clamp unit, pin unit, rest unit, etc. of the tool, also other parts like pneumatic valve box, trunk cable path will also be mounted on to a base unit.

PARTS OF BASE UNIT:

Parts of base unit are as follows,

• Valve box.
• Trunking channel.
• measuring hole cover.
• Eye bolt.
• Floor plates.

1. Valve box:

• Valve box is basically a box which supplies air to all the pneumatic cylinders assembled in the fixture.
• Valve box consist of one solenoid valve is used to collect the air from the pneumatic cylinders to valve box.

2. Trunking channel:

• Trunking channel is a kind of cable duct, which helps to guide and protect the wirings/tubes used in the fixtures.

3. Measuring hole cover:

• In the measuring hole cover the coordinates points are engraved on it.
• The hole which mention the coordinates gives the position & placements of the particular units.
• The measuring hole helps in CMM inspection & QC inspection.

4. Eye bolt:

• An eye bolt is a bolt with a loop at one end. They are used to firmly attach a securing eye to a structure, so that ropes or cables may then be tied to it for lifting purpose.
• Eyebolt is used to frag or lift the base unit while relocating.

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

DUMP UNIT:

• Dump unit is where you assemble component if you have certain constraint. Here you will have clamp unit, pin unit attached & panel will be assembled. So if you have certain constraint you cannot assemble in normal way.
• Dump unit use in different way. It has dump cylinder & complex design. It consists of dump cylinder to perform the operation of clamping & unclamping car panel. A dump unit can have more than one cylinder to perform such operation.
• The first cylinder dumps the assembly carrying clamp mylars, pins and then this assembly performs the required operation. In this unit, we should make sure that in the open position of panel, we should be able to remove the panel. Below fig show dump unit.

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

Slide units:

Slide units are positioning units, which are used to position the car part or panel, units, weld gun, robots for further operations.

Slide units may be classified into two types based on the type of guide ways. They are,

• Hardend guide way.
• LM guideway.

Slide units may further classified into three types based on the prime mover. They are,

Manual slides.

• Hydraulic/pneumatic slides.
• CNC slides.

It may be further classified depending on the application as

• horizontal slide unit.
• Vertical slide unit.
• Angular slide unit.

Basic fundamentals of slide unit design:

Reverse stroke o 10mm to be considered in both forward & retracted condition.

Cylinder & LM guides to be validate for load & stroke.

Master guideway should be constrained & the subsidiary guideway to be free.

Mechanical hard stop to be considered for both extended & retracted condition.

Shock absorber should be used for both extended & retracted condition to reduce impact load.

Slide to be locked/clamped in the working position.

Slide to be locked with a safety pin in the retracted position during transportation.

The two end limits to be sensed externally by a proximity switch.

The design should be checked for screw accessibility, ease of assembly, machinability of parts.

The LM guide & rails are integral assemblies and should not be separated at any cost.

LM guide ways to be lubricated for long life.

SLIDE UNITS ARE COMMONLY USED IN:

• Slide unit is found mostly in complex fixture, where the sliding mechanism will be involved.
• This type of unit used when there is some space constraints in locating the panel.
• Slide application will be easy for welding.
• Slide unit can be minimize the cost of robot as slide unit provided to move weld gun from one weld spot to other weld spot instead of weld robot.