BIW Fixture Design Methodologies Challenges

Question No.1 – What are Design methodologies?

Answer:

DESIGN METHODOLOGIES:

In this methodology we learn about three design processes, we're going to study how we proceed while doing a design. And one of the things that we take care of is 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,

1. Purchase order.
2. Inputs from customers.
3. Percentage of completion criteria.
4. Design outputs.

1. Purchase Order:

A purchase order (PO) is a commercial document and the 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. A purchase order is an order from a customer for the start of the work. After an 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.

A purchase order is the confirmation document from the customer to proceed with the committed work for them.

2. Inputs from customers:

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 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 standard parts, they can be easily replaced from the used fixture the new fixtures, reducing the cost.

Car products:

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

Layout:

The layout shows the entire assembly plan to understand the process. The layout provides information on the flow of parts, station pitch, robot stations, accessories like tool changers & tip dressers, sub-assembly links, plate form height, and 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 be given by the customer mostly in the case of manually operated fixtures/manual fixtures. The ergo data is mainly used to make the operator comfortable which may lead to improved efficiency in cycle time& production. Ergo data provide inputs like platform height, maximum & minimum reach from operator to fixture, maximum & minimum height of the fixture, and whether the child parts/assemblies are visible while clamping or loading & unloading. Also provides information like loading height, working safety zone of the operator, etc.

Weld study:

Weld study is the important input 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, and the position of weld in the components will be given. In short, weld study includes weld gun details, weld matrix & weld points.

Standard detailing templates:

These inputs include the detailing templates of 2D cad drawings as per the customer standards. So, we have to follow the detailing templates as per the customer's standards.

3. Percentage of completion criteria:

Percentage completion criteria are scheduled. What time we can complete the entire process again this is more detailed. So when we are going to complete the entire design, 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 many tasks are 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.

Question No.2 – What are the inputs required from the customer to start designing a fixture?

Answer:

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 standard parts, they can be easily replaced from the used fixture the new fixtures, reducing the cost.

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

Standards like ABB, NAAMS, DESTACO, ZYTRAN, and TUNKERS are used in the 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 to sharpen the tip of the tools whereas tool changes are used in robots to do various processes. As robots are too costly, tool changers are used.

ABB – It is a robot manufacturing company.

Some examples 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 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 parts, Clamp plan, and product assembly process sheet.

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

Part lists: These give the lists of parts that are going to be assembled in the fixture. The list contains information on part number, part name, revision of fixture, part thickness, etc.

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

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

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

4. Layouts:

The layout shows the entire assembly plan to understand the process.

The layout provides information on the flow of parts, station pitch, robot stations, accessories like tool changers & tip dressers, sub-assembly links, plan form height, and 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 be given by the customer mostly in the case of manually operated fixtures/manual fixtures.

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

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

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

6. Weld Study:

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

Also, the data like No. of weld, and the position of the 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 drawings as per the customer standards.

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

Question No. 3 – What are the inputs we get from car products?

Answer:

Inputs we get from car products include;

GD&T.

Part lists.

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 for each station. Also includes information on the 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 the 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 designs.

When standard interpretation or tolerance is not already implied.

When it allows a better choice of machining processes to be made for the production of a part.

Datum in GD&T:

A datum is a 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 that are going to be assembled in the fixture. The list contains information on part number, part name, revision of fixture, part thickness, etc.

3. 3D cad files:

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

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

4. Clamp plan:

The clamp plan provides information on the location of pins, rest units, clamp units, dumps, etc.

It is important to input from customers. 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 information on stage wise assembly process like how the parts move from one assembly to another after the completion of the joining process

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

Also, what are the parts to be joined with the panel that will show in sequence?

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

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

Question No.4 – What is the clamp plan?

Answer:

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 workpiece 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 workpiece.

Clamp Plan:

Clamp Plam is a very important input that we get in the car products is where exactly we can place those clamping units in 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 a clamp unit, and 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, the whole diameter, and everything is already given to design the entire future design phase, it is sometimes ministry as well. It happens that another thought position, is also given very close to the clamp, or the clamp location. So always ask whether you have changed the clamp position.

we should never change the vent position or the clamp position without asking for it So always be vary about these situations the tool might get damaged or the department gets damaged so for that itself need to clarify once again before doing any changes in the clamp.

Question No.5 – What is the purpose of the layout?

Answer:

THE PURPOSE OF THE LAYOUT:

The purpose of the layout is to understand the information about where the fixture & robots are been placed, the working area covered by the robot, what 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 robot particularly with the confined circle.

The layout provides information on the flow of parts, station pitch, robot stations, accessories like tool changers & tip dressers, subassembly links, plate form height, and loading/unloading sequence/height.

The layout sheet will give you information about all the fixtures that are placed, the robots are going to work on them.

In the layout sheet, the circle around the robot is called the Trapped Area of that particular robot.

So, this is the reachability of the robot which is confined to a particular circle.

The flow of parts: It shows the flow of the parts/panel in the assembly line or shop floor like how components move from one station to another station after the completion of the 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 the layout.

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

Sub-assembly link: The subassembly link is nothing but the link between the assembly fixtures & the main assembly line. It shows how the subassembly 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 provides the above information like the 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 constraints, 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 purposes is to get information about the space constraint which helps to develop the robotic cell without any clash during working.

Question No.6 – What is Ergo data?

Answer:

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 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 to improve productivity & accuracy.

In short, the objective of ergonomics is designing for human use & optimize working & living conditions.

Two main objectives of ergonomics are:

To enhance the efficiency and effectiveness with which the work is carried out to increase the convenience of use, reduced errors & increase productivity.

To enhance certain desirable human values including safety, reduced stress & fatigue, and improved quality of life.

Ergonomics involves the design:

A workplace is suitable for the worker.

Machinery & controls, to minimize physical strain on the worker to enable the improvement in efficiency.

An environment for performing a task most effectively and conducive.

A conducive task & work organization.

Benefits of Ergonomics:

Improved working conditions.

Reduce physical workload.

Improved work postures.

Reduced efforts of certain movements.

Better reading instrument displays, and 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 give the human factors engineering data, between the operator & his working environment.

Ergo data is most needed while there is a need for manual operator/operation.

Ergo data will be given from customers as per their standards. Every customer follows different ergo data standards.

As per customer standards, we have to consider the ergonomics of 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 lead to improved efficiency in cycle time & production.

Question No.7 – What do you understand by welding study?

Answer:

WELD STUDY:

Weld study is the important input from the customer.

It gives the study of a particular gun that we use for welding, No. of spots to be welded, sequence of weld, and 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.

The red sphere represents the Geo spot weld points whereas the 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.

This weld will determine the position of the panels as per the given data in the drawing.

The geo weld points are represented in the red sphere in the weld study inputs given by the customers.

Respot weld points:

The respot weld points are planned in the respot tool.

This weld will determine the strength/stiffness of the panel/components.

The Respot weld points are represented in green spheres in the weld study inputs given by the customers.

Question No.8 – What are the criteria for percentage completion in the designing stage? Explain in detail.

Answer:

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 and whether it matches the committed date given to the customer for handing 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 the further stages are 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 the 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 the 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 to check & final dispatch which is the fourth & last stage in the percentage completion criteria.

4. Check and final dispatch:

If the project is 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.

Question No.9 – Brief about output in design?

Answer:

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-Unitised Tools

1. Unitized Tools:

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

So Examples of unitized tools are fixtures, tools So 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 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 Nonunitized tool no need for key sheets. As they can stand alone, the drawing can be detailed completely on layout sheets.

So, it is 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.

Nonunitized tools are basic tools like Stands and tool changers is also an example of nonunitized tools where you don't need a key sheet, you can use it to lay out the sheet and complete the entire documentation of the particular component. So this is as known nonunitized tools.

The Design Output Should Compile the Following Points:

Approved standard components are to be used wherever possible.

Design must be as simple & economical as possible.

The design must comply with all current safety & ergonomic requirements.

Design must provide for controlled & damage-free handling of the 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.

The designer is responsible to validate clamps & welding guns.

Question No.10 – What do you understand by structuring a design tree? How does it reduce errors during the design process?

Answer:

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 sets of standards to structure a design tree.

It is an important process that helps us to identify a specific part or assembly as to which project, tool/unit, it belongs to.

This helps us to avoid 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.

The naming of a fixture or a unit or a part gives the information as to which project or zone, or assembly they belong.

It can help us to identify the number of items of the same types or different types that are being used in the assembly.

When start designing a fixture, the first unit will be the base unit.

In the structure tree, all the manufacturing parts should be first and the standard parts should be last.

A structure tree helps to study or understand the parts in the assemblies easily.

Steps to structuring a design tree:

Step 1: Create a new à Product à click OK (by clicking ok now you will enter into a product window)

Step 2: Then right-click a product in a structure tree à go to properties à rename the 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 has certain standard procedures, which I have clearly explained below.

The product name is the title of the fixture. The renamed title should be à P001_Z03_ST09_00_00_R

P001 – represents the project name.

Z03 – Zone name.

Panel names will also be mentioned in some cases.

ST 09 – Station name / J03 – Jig name will be mentioned 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 the video is

H1L_19A_RRFRA_JG3_00_00_R.

H1L_19A – Project name.

RRFRA – Panel name.

JG3 – Jig name/number.

00 – unit name

00 – Part number.

R – Indicates right side.

Question No. 11 – What are units? Mention 5 types of units.

Answer:

Units:

A unit is a device that has a specified function, especially one forming part of a complex mechanism.

A welding fixture is an assembly of different types of units.

As the name refers, the different units will be only seen in the unitized tool.

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 to some of the simple units these complex units will also be seen

Slide unit.

Dump unit.

Five Types Of Units:

Base unit:

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

Fixed pin unit:

A fixed pin unit is a unit designed to locate the car panel using pins. table

Pin, pin retainer, shims, blocks, blade, and riser are part of fixed pin units.

A 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 pins so total constraint by locating pins should be fully constrained at all times to prevent any movement.

Retractable pin unit:

A retractable pin unit is a 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.

A retractable pin unit is the opposite of a fixed pin unit which can be moved up & down also which can be retracted till a certain distance.

It is mainly used for unloading the complex panel after welding.

Clamping unit:

A clamp unit is a unit designed to clamp or hold the car panel with NC block / Mylars by using a pneumatic clamp cylinder.

A clamping unit is used to clamp the part which is to be welded after location using a pin unit.

Clamping is achieved with the help of pneumatic cylinders and clamp arms.

The clamping arm, finger, rest, shims, standard riser, and pneumatic cylinder are the parts of a clamping unit in general.

Slide unit:

The slide unit is found mostly in the complex fixture, where the sliding mechanism will be involved.

This type of unit is used when there are some space constraints.

The guide block, guide rail, position lock unit, stopper block, and sensors are the parts of the slide unit in general.

Guide block & guide rail helps to guide the slide unit. The rail should always be covered to protect against weld spatter & dust by a bellow or a sheet metal cover.

The position lock unit helps the slide to be locked/clamped in the working position.

The stopper block helps to stop/control the entire movement of a slide unit from a certain distance, which is placed at the end of the guide rail.

Sensors – The two end limits are to be sensed externally by a proximity sensor.

Question no. 12 –Describe fixed pin unit & their purpose.

Answer:

Fixed pin unit:

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

Pin, pin retainer, shims, blocks, blade, and riser are part of fixed pin units in general.

A pin retainer is used to hold the pin firmly.

PURPOSE OF FIXED PIN UNIT:

As by the 3-2-1 locating principle, the introduction of two pins helps to arrest the 6 degrees of freedom (4 axial & 2 radial movements) whereas the other 6 degrees of freedom are arrested by introducing a minimum of three supports.

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 pins so total constraint by locating pins should be fully constrained at all times to prevent any movement.

Question No.13 – What are the different parts of the fixed pin unit?

Answer:

DIFFERENT PARTS OF THE FIXED PIN UNIT:

The different parts of the fixed pin units are as follows,

Pin.

Pin retainer.

Shims.

Blade.

Riser.

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 pins so total constraint by locating pins 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 a small or large head.

Round Pins:

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

2. Pin Retainer:

A pin retainer is used to hold the locating pins firmly. A pin retainer is designed to hold the pin in its place and is also used as a rest for the pin. A counter hole is 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 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 that come with a thickness of 0.1mm, 0.2mm, 0.5mm, 1.0mm, etc.

These will compensate for the stack-up tolerance which reflects in the mylars.

We give tolerances to all parts of the fixture. Due to this tolerance, the mylars will either lift or move down from their 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:

Types of shims are,

Wood shim.

Stone shim.

Plastic shim.

Metal shim.

Paper shim.

4. Riser:

The riser is a manufacturing part used to raise / height the assemblies of fixtures.

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

Raisers can be of two types. They are,

‘L’ type risers.

Square tube risers.

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

Square tube risers: Square tube risers are of frame type.

5. Blade:

Blades are the plates that are attached to the raiser.

The blade is also attached or mounted with cylinders, arms, etc.

Question No.14 – What is the purpose of making a rest unit? And describe its parts?

Answer:

PURPOSE OF MAKING A REST UNIT:

A rest unit is a unit designed to support the car panel using Mylar/ NC block/ rest. The component is rested only, no upper clamp or force is 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 another unit to reduce the cost of the overall project.

It can be combined with a 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 units can be combined into one unit to reduce cost.

There is no cylinder attached to it. It has a rest Mylar, blade & riser & below is different parts of the rest unit. The rest unit is also divided into simple support units, multiple support units & retractable support units.

PARTS OF REST UNIT:

The parts of the rest unit are as follows,

NC block/mylars.

Risers.

Blades.

Shims

1. NC blocks/mylars:

Mylars are the part which is holding the panel from top & bottom.

It is a jaw type, during welding it won't deforms from its position.

It is also known as fingers.

It won't allow the deformation of the part due to welding stresses.

Mylars are of two types, they are

1. Clamping mylars
2. Resting mylars

Only resting mylars can be seen in the rest unit.

The panel which rests on the part is known as the resting mylars.

2. Risers:

The riser is a manufacturing part used to raise/height the assemblies of fixtures.

One end of the raiser will be attached to the base unit while the other end will be attached to the blade.

Risers can be of two types, they are,

L-type riser.

Square tube riser.

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

Square tube risers: Square tube risers are of frame type.

3. Blade:

Blades are the plates that are attached to the raiser.

The blade is also attached or mounted with cylinders, arms, etc.

4. 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 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.

Question No. 15 – What are the fundamentals to design a sensor unit?

Answer:

SENSOR UNIT:

A sensor unit is a unit designed to sense the car panel by using electrical sensors.

These 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 is being welded in a tool should be sensed.

Each panel should be sensed by 1 or 2 sensors depending on the size of the panel, preferred to be in diagonal opposite ends of the panel.

Every sensor should be mounted in a 3-direction adjustable way in general.

We should try to minimize the size of the sensor as much as possible.

Some major sensor manufacturers are IFM, Pepperl – Fuchs, sick, OMRON, etc.

Types of sensors 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 sensor's target.

Laser sensor:

These laser distance sensors use a focused, coherent light to measure the distance to a target object. In factory automation applications, the target is usually a product or machine element. 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 the 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.

Question no. 16 – What is a rough locator unit & what are the fundamentals to consider while designing it?

Answer:

ROUGH LOCATOR UNIT:

A rough locator unit is a unit designed to guide the operator to locate the car panel on the coins accordingly.

A rough locator can be a standard part of a make part.

THE BASIC FUNDAMENTALS TO CONSIDER WHILE DESIGNING A ROUGH LOCATOR:

A rough locator should be placed at the edges of the car panel, which has to guide.

The rough locator should be placed at the same angle as the car part edge with a minimum distance of 2 – 5 mm from the edge of the car part.

Rough locators should guide the panels in a pin assembly direction in general.

Rough locators should start guiding the panel 10 to 15mm to the start of the pin engagement.

Rough locators should be designed with an 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 the car part guiding.

Question No. 17 – What is a base unit? And describe its parts?

Answer:

BASE UNIT:

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

PARTS OF BASE UNIT:

Parts of the base unit are as follows,

Valve box.

Trunking channel.

measuring hole cover.

Eye bolt.

Pedestal.

Floor plates.

1. Valve box:

A valve box is a box that supplies air to all the pneumatic cylinders assembled in the fixture.

The valve box consists of one solenoid valve that is used to collect the air from the pneumatic cylinders to the valve box.

2. Trunking channel:

A 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 mentions the coordinates gives the position & placements of the particular units.

The measuring hole helps in CMM inspection & QC inspection.

4. Eyebolt:

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 purposes.

Eyebolt is used to frag or lift the base unit while relocating.

5. Pedestal:

The pedestal is a stand-like structure where the entire unit of the base will be mounted.

6. Floor plates:

Floor plates are used to mount the entire base with the floor.

Also, it helps to achieve the flatness of the fixture.

Question No.18- What is a dump unit & what is its function?

Answer:

DUMP UNIT:

A dump unit is where you assemble components if you have certain constraints. Here you will have a clamp unit and pin unit attached & panel will be assembled. So if you have certain constraints you cannot assemble in the normal way.

Dump units are used differently. It has a dump cylinder & complex design. It consists of a dump cylinder to operate clamping & unclamping the car panel. A dump unit can have more than one cylinder to perform such an operation.

The first cylinder dumps the assembly carrying clamp mylars, and pins and then this assembly performs the required operation. In this unit, we should make sure that in the open position of the panel, we should be able to remove the panel. Below fig shows the dump unit.

Question No. 19 – What are slide units? Mention where slide units are commonly used.

Answer:

Slide units:

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

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

Hardened guideway.

LM guideway.

Slide units may further be 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.

Fundamentals of slide unit design:

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

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

The master guideway should be constrained & the subsidiary guideway to be free.

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

Shock absorber should be used for both extended & retracted conditions 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 are to be sensed externally by a proximity switch.

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

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

LM guides ways to be lubricated for long life.

SLIDE UNITS ARE COMMONLY USED IN:

The slide unit is found mostly in the complex fixture, where the sliding mechanism will be involved.

This type of unit is used when there are some space constraints in locating the panel.

Slide application will be easy for welding.

The slide unit can minimize the cost of the robot as the slide unit is provided to move the weld gun from one weld spot to another weld spot instead of the weld robot.