Week 3:- BiW Fixture Design Methodologies Challenges

1) What is Design Methodology?

DESIGN METHODOLOGY

Design Methodology is the step which is followed during the concept designing stages of fixture design.

Design methodology is divided into four sub categories:

• Purchase Order
• Inputs from Customer
• Percentage Completion Criteria
• Design Output

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.
• A Purchase order is the order from the customer end for the starting of the work.
• 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.
• Indent is a purchase order often placed through an agent (indent agent) under specified conditions of sale.
• The issue of a purchase order does not itself form a contract. If no prior contract exists, then it is the acceptance of the order by the seller that forms a contract between the buyer and seller.
• Purchase orders allow buyers to clearly and explicitly communicate their intentions to sellers.
• They may also help a purchasing agent to manage incoming orders and pending orders.
• Sellers are also protected by Pos in case of buyer’s refusal to pay for goods or services.
• Purchase orders provide benefits in that they streamline the purchasing process to a standard procedure.
• Commercial lenders or a financial institutions may provide financial assistance on the basis of purchase orders.

INPUTS FROM CUSTOMER

• Inputs from customer basically are the data given by the customer like requirements, standards, layouts, etc.
• We study those input to what kind of information get out of it.

Designer needs following basic information to start the BIW fixture.

Functional requirements

• The purpose of the function of the fixture will be given as input from the customers like what are the function the fixture is going to do (i.e.) Welding, riveting, gluing or whether it is a checking fixture, etc.

1) Preferred Standards.

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

A) Car Products

• The inputs we get from car products are GD & T, parts list, CAD files of car part, Clamp plan, Produce assembly process sheet.

B) Layout

• Layout shows the entire assembly plan to understand the process.
• Layout provides information of flow of parts, station pitch, robot station, accessories like tool changes and tip dressers, sub assembly links, platform height, loading and unloading sequence heights.

C) Ergo Data

• As same as preferred standards, different companies for the different standards or ego data.
• We have to follow the customary standards of ergo data. The inputs of the Ergo data will be given by the customer mostly in case of manually operated fixtures.
• Ergo data is mainly used to make the operator comfortable which may lead to improve the efficiency in cycle time and 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 the datas like No. of weld, position of weld in the components will be given and informations like loading height, working safety zone of operator, etc.

D) Weld Study

• Weld study is the important inputs given to the customer.
• It gives details about the study of particular gun that we use for wedding.
• Also like the number of weld, weld position of the components will be given.
• In short weld study includes welding gun details, weld matrix and weld points

E) Standard detailing template

• These 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.

PERCENTAGE COMPLETION CRITERIA

• It is followed in designing stages and dispatch stages of welding fixtures.
• It helps to track or identify how much task is completed and how much to go further for completing a fixture.
• Input send concept design -0 to 25%
• Concept approval and simulation check – 25 to 40%
• Design Freezing and detailing – 40 to 85%
• Check and final dispatch – 85 to 100%

The above-mentioned percentage of the percentage of state wise completion criteria of the projects.

DESIGN OUTPUT

The output is a 3D models and 2D drawings of the tools.

• Unitized tools- Mutiple units on a comman base. It requires two types of drawing as given below.

1. Key sheet: It is an index of units and their placements on the tool base.
2. Layout Sheets: A detailing drawing of individual units to include all of their components.

• Non-Unitized tools – It is the tool that can stand alone and can be detailed completely on a layout sheet.

2) What are the inputs required from the customer to start designing a fixture?

INPUTS REQUIRED FROM THE CUSTOMER

To start designing a fixture the following are the inputs required for designing a fixture.

• Functional requirements
• Preferred standard components
• Car Products
• Layout
• Ergo data
• Weld study
• Standard detailing templates.

Functional requirements

• The purpose of the function of the fixture will be given as input from the customers like what are the function the fixture is going to do (i.e.) Welding, riveting, gluing or whether it is a checking fixture, etc.
• It is one of the basic requirements to get from the customer to start designing a fixture

Preferred Standards

• As we know different companies follow different standards, we will be following the standards, followed by the customers.
• By following the standards in the time of designing and manufacturing of parts we will be saving the time and cost which will be automatically minimizing the time of the projects.
• As per the standard parts, it can be easily replaced from the used fixture to the new fixture which reduces cost.
• Some of the preferred standard components used in BIW as stated below.
• Standards like ABB, NAAMS (North American Association for Mechanical Standards), DESTACO, ZYTRAN, TUNKERS.
• Standard parts like Risers, L-Blocks, Retainers, Pins.
• Components like Clamps, Cylinders, Slides, Switches, Sensors.
• Weld guns, Tip dressers, Tool Changers, Tip dressers are used to sharpen the tip of the tools which are used in robots in various processes.

Car Products

The inputs we get from car products are GD & T, parts list, CAD files of car part, Clamp plan, Produce assembly process sheet.

GD & T

• It provides information of 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.

Part Lists

• It gives the lists of parts which are going to be 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 or position should not be changed without the knowledge of customer.

3D Cad File

• 3D model of the car part will be given the 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.

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 process to the other after completion of joining process.

Layout

• Layout shows the entire assembly plan to understand the process.
• Layout provides information of flow of parts, station pitch, robot station, accessories like tool changes and tip dressers, sub assembly links, platform height, loading and unloading sequence heights.

Ergo Data

• As same as preferred standards, different companies for the different standards or ego data.
• We have to follow the customary standards of ergo data. The inputs of the Ergo data will be given by the customer mostly in case of manually operated fixtures.
• Ergo data is mainly used to make the operator comfortable which may lead to improve the efficiency in cycle time and 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 the datas like No. of weld, position of weld in the components will be given and informations like loading height, working safety zone of operator, etc.

Weld Study

• Weld study is the important inputs given to the customer.
• It gives details about the study of particular gun that we use for wedding.
• Also like the number of weld, weld position of the components will be given.
• In short weld study includes welding gun details, weld matrix and weld points

Standard detailing template

• These 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) What is the input we get from “Car Products”?

Inputs we get from car products include

• GD & T.
• Parts lists.
• 3D Cad file.
• Clamp plan.
• Product assembly process sheet.

GEOMETRIC DIMENSIONING AND TOLERANCING

• It provides information of 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.

PART LIST

• Par list gives the information of parts in a unit.
• It consists of number, part name, which helps to identify the part easily. It also consists of number of parts which is required and its thickness, etc.
• This list helps to check all the parts and its dimensions and required number of quantities.

CAD FILES OF THE CAR PART

• CAD files of car parts gives the simulations of those 3D models and their analysis.
• It is also used throughout the engineering process form conceptual design and layout of the products through strength and dynamic analysis of assemblies to definition of manufacturing methods of components.

CLAMP PLAN

• This is the clamping plan while doing the operation.
• We cannot complain without permission of the customer. It is very important input from the customer.
• It provides location of pins, rest clamps, dumps, etc.
• If the clamp is nearer to the weld spot, one should not change the clamp position without consulting it even it appears to damage the tool.
• Design should not change without consulting with superior.

PRODUCT ASSEMBLY PROCESS SHEET

• It gives the details of the process for the completion of the part from scratch to the finished products of the assembly.
• Product assembly process sheet gives complete assembly of a unit.
• Different parts in a unit are assembled by geo weld first. Then the weld parts are assembled by re-spot welding.
• Similarly, every small parts of a product or unit is assembled first and these small parts are welded together to get a final product.

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 a clamps

• All clamps must fulfill four essential requirements. They are as follows.
• The work piece must be held rigid while undergoing operations.
• The time required for loading or 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 plan provides the information of location of pins, test units, unit clamp, etc.
• It is the important input from the customer.
• The clamp plan or position should not be changed with out the knowledge of customer.
• It is an important input from the customer.
• The clamp plan/ position should not be changed without the knowledge of the customer.
• It gives the detail of the exact position of the clamping units by mentioning a coordinates of the particular position.
• 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.
• Design can be changed but we should not change the input design data about the clamp position or the pin position.
• In Clamp plan, there is a clamp unit, pin unit and it also gives the exact location of Y and Z coordinates designing as well you can just input these coordinates and can start designing from there.
• Always ask for the change in the clamp position as the requirements might change later by the customer.
• The vent position or the clamp position should not be changed without asking to the superior as the tool might get damaged or department get damaged.

5) What is the purpose of a Layout?

LAYOUT

• Layout is basically the layout of the entire assembly line to understand the process and the flow of work.
• Layout sheet will give the 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 that particular circle.
• For example: robot is going to work on the fixture details also mentioned the geo station 250 and then number is given 250 and as you can see 250 02 so this is dueling to one or two its is going to use there so, this robot is going to work on the site first.
• After finishing that site, the fixture is going to rotate and then it will come to t01 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 components 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.
• In case of any changes, it should be informed prior to the customer regarding the changes and to get the approval from them.

Layout provides information such as

Flow of parts

In the flow of parts how the particular component is going to move from one unit to another of one station to another station

Station Pitch

In station pitch a distance between two stations. It shows the space concept that they have between two stations.

Robot stations

Robot stations and positions where the robot placed stations.

Accessories like tool changer and tip dresser

Accessories like tool changes and tip dresser where those are placed. If the robot wants to change the particular tool, it has to go to the particular location and change it.

Sub assembly links

Sub assembly links are basically how the particular fixtures in the assembly fixtures are linked to the assembly line.

6) What is Ergo data?

ERGO DATA

• Ergo data is nothing but the data or inputs which gives 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 know as human engineering & human involved in 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 as follows.

• 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.

DESIGN OF ERGONOMIC

• 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.

BENEFITS OF ERGONOMICS

• Improved working condition.
• Reduce physical workload.
• Improved work postures.
• Reduced efforts of certain movements.
• Better reading instruments displays, handling of machine levels and controls.
• Reduced unnecessary information recall efforts.

The twelve ergonomic guidelines resulting from the workshop with the engineers were incorporated into the design requirements.

• Flexibility and adjustability for viewing angle, access and hardness.
• Physical access for hands or tools and clear visual viewing angle.
• Prevent blind assembly.
• Eliminate obstructions in front of working area for ease of access. E.g. knob position.
• Standardized light colors. E.g. Yellow- in process, Green- completed, Red- Fault.
• Locate lights as close to hand location as possible.
• Design should not rely on operator for positioning.
• Ensure operations do not cause change in positioning of part. i.e. that it needs stabilization by person.
• Avoid having to hold with 2^nd hand while loading.

7) What do you understand by Weld study?

WELD STUDY

• Weld study means a study of the welding technique that we are going to use, its temperature, type of current, type of gases used, type of gun used for welding and where are we going to weld, etc.
• If we use a spot welding, which type of electrode is used for welding, number of spots, etc. that comes under the weld study of that particular component.

Weld study includes

• Weld gun details
• Weld material and weld points.
• Geo weld points and re-spot weld points.

Weld gun details

This involves the study of the gun like

• Type of weld
• Number of spots it can weld
• Temperature of weld
• Type of current used
• Approach of the gun.

WELD MATRIX AND WELD POINTS

• Weld points are basically where the welding is going to happen and at which point, at which coordinates the weld is to be done.

GEO WELD POINTS AND RESPOT WELD POINTS

• The data of weld matrix and weld points will be given in the form of spheres. i.e. red and green spears and at that point the welding will be done.
• Geo spots are red in color and Re spots are Green in color.
• All the red spheres are going to happen in geostationary.
• In the re-spot station where the green welding is going to happen. So, this happens where one component is going to attach to this particular component and in the other station, the other components get attach.

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

CRITERIA FOR PERCENTAGE COMPLETION IN THE DESIGNING STAGE

• The percentage completion criteria is followed in the designing stages and dispatch stages of welding fixtures.
• This percentage completion criteria 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 is 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
• Input & Concept design
• This is initial stage of project. Input data provided by customers like functional requirements, customer standard, etc. & after studying those inputs the concept of fixture design is created.
• After completion of this tasks about 25% of work is completed.
• Concept approval & simulation check
• As concept of fixture design is created & simulation checked it is sending for the customer approval.
• Customer will study all simulations & gives his approval.
• If there are any changes required, then it has to do accordingly & again submit for approval.
• This concept design approval from the customer after study or simulation contributes only 15% of total design work. But with completion of this task 75-40% works completed.

Design Freezing & detailing

• This phase involve design freezing after approval of concept design.
• Freezing means finalizing concept design.
• Next step is detailing as per customer standard template.
• With completion of this stage almost 85% of work is completed in designing stage.

Check & Final dispatch

• After detailing the quality checking team starts inspection of all the date it will dispatch to the customer as per customer standard.
• If there is any error in drafting it will create issue or mistake in manufacturing stage.
• Thus, the percent completion criteria help us to know where we are in design process.

9) Brief about output in design

DESIGN OUTPUT

• It included data to be given to customer after completion of design stages.
• The output is a 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, position of locators, positions of clamp, positions of supports.
• If any type of locators, types of clamps, types of supports, forces & supports.
• There are two types of tools in a fixture design such as Unitized tool, Non-Unitized tool

Unitized Tool

• In unitized tool there are multiple units on common base. For example, geo fixture, robot fixture, checking fixture, hemming station, etc.
• Unitized tools require two types of sheets.

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 position of the tool base.
• Key sheet is showing orthogonal or isometric view of that entire component.

Layout sheet

• A detailed drawing of individual units to include all of their units.
• Layout sheet detailed drawing of that particular tool where we are going detail of components.
• This also helps in CMM inspection of fixture.

Non Unitized Tool

Non unitized tools that can stand alone and can be detailed on a layout sheet. E.g. Rack, take out trolleys, tum tables, grippers, etc.

The output should complete the following points.

• Approved standard parts should be used wherever possible. This saves lot of time, effort & economical.
• Design should be as simple & economical as possible. Geometry is complex then fixture design is complex but approach is trying to design as simple as possible.
• Design must comply with all current safety & ergonomics standard.
• Design must provide for controlled & damage free handling of product.
• Adequate error proofing provision must be incorporated in each design by providing proximity switches, rough locators, etc.
• Proximity switches are basically sensors which tells part is present or not in fixture.
• The weight of moving part must be kept to minimum while maintaining maximum strength weight of moving component kept as minimum as possible but it shouldn’t compromise on strength.
• Frames and structures are to be simple & sturdy.
• Design clearance and accessibility for routine maintenance and service. Fixture needs maintenance after certain period of time so it is easily accessible for maintenance.
• Motion control must be considered or any moving component.
• Adequate to control the motion of component like slider, clamp alarm so that it does not give any vibration & stays on particular by use of hard stopper shock absorber.
• Designers are responsible to validate all clamps & welding guns. So that all clamps & gun should perform its function without fail.

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 standards and the structure of design tree.
• Every company, every customer has different standards of their own structural design tree.
• They will be giving a template on how the structuring and detailing of the design is done.
• In the design tree itself, if we mentioned that particular name, wherever the part is we can easily know that this part belongs to that particular station or assembly or unit.
• This helps to prevent errors during the design study, manufacturing assembly and inspections.
• If the part or assembly are not named properly or design tree is not structured properly, it will be difficult to understand the design and may create major possibilities of making errors.
• Naming a fixture or a unit or a part gives the information as to which project zone or assembly where they belong.
• It can help us to identify the quantity of items of same types of different types that are being used in assembly.

In design tree in which designed parts are at top & all standard parts are at bottom.

The blue highlighted number is HIL-T9A-RRFRA-JG3-00-00-00

• HIL-T9A- The Project name
• RRFRA- Panel name
• JG3- Jig no. 3
• 00-unit no
• 00-part no
• 00-component no.

Under the product, there are main assemblies, sub assemblies, child parts, standard parts, etc. which are provided with specific number, zone, etc. to identify easily.

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

UNITS

• A unit is a device that has specified function, especially one forming art of a complex mechanism.
• Multiple units are joined together in order to form a fixture and are attached to a common base, which serves as a common support to the units where they are fixed.
• A welding fixture is assembly of different types of units.
• As name refers, the different units each serves with different functions and different purposes.
• Units are classified into two types.

A) Unitized tools

B)Non unitized tools.

A)Unitized tools

• Unitized tools are basically tools which is a part of multiple units or multiple part inside it.
• These are represented by key sheet. Unitized tools have two types as simple unit & complex unit.
• Simple unit has simple design & approach for manufacturing is also simple, whereas complex unit has complex design.

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.

Fixed pin unit

• It is unit designed to locate car panel using pins. Unit pin already fixed cannot be moved.

Retractable pin unit

• It is opposite of fixed pin unit which can be moved up & down, It can be retracted to certain distance.
• A retractable pin unit is designed to locate the car panel using pins, but the entire pin package parts will be mounted on the retractable pneumatic cylinder.
• Each pneumatic cylinder will receive air through valve. When air is given to cylinder it is extended in forward motion & if air is given out it is retracted.
• Nowadays pneumatic cylinder come with locking mechanism in forward motion.

Clamp unit

• Clamp unit is unit designed to clamp/ hold the car panel with NC blocks/ Mylar/ rest by using pneumatic clamp cylinder & below are different parts of a clamp unit in general.
• Usually clamp one position is 90 degree.
• Fingers are attached to clamp mylar. In clamp unit shim to one side is more enough because it will restrict translation motion in upward & downward direction only.
• There is another type of clamp unit known as swivel type.
• There is pivot pin around which clamp arm rotate.

Rough locator unit

It roughly guides the operator for locating the part.

Sensor unit

It is designed to sense car panel using electrical sensor.

Base unit

It is the unit on which all other units are mounted. It supports all the other units.

Non unitized tools

• Non unitized tool is basically one unit. It doesn’t have any process functionality in it.
• It has function to keep component stable. Example of Non unitized tools are stands, takeout trolleys, conveyor, turntables, etc. where we don’t need key sheet for that only layout sheet is enough to tell orientation as well as position.

12) Design fixed pin units & their purpose?

FIXED PIN UNIT

• It is unit designed to locate car panel using pins.
• Its unit pin is already fixed it cannot moved & below are the different parts of unit in general.
• Fixed pin unit basically have pin, pin retainer, shims/ spacers, block, blade or adaptor plate.
• Pin retainer support the plan.

• Every pin unit will have two directional shims.
• The block is used to mount entire pin unit.
• Shims are used to avoid stack up tolerance while assembling entire component.
• Shims are come in pack of 0.1, 0.2 & 0.5mm

Purpose of fixed pin

• Pin is most important part of fixture & used to restrict rotational as well as translational degrees of freedom of that particular component.
• Purpose of fixed pin unit is to fix the panel translation motion along two axes and to prevent rotation of panel in the axis of panel.
• It supposes to have exact coordinate for it to get fix.
• Suppose it will move by 0.1 to 0.2mm from its original positional then entire assembly will not happen or get rejected.

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

The different parts of a fixed unit are.

1. Locating pin
2. Pin retainer
3. Shims
4. Blade
5. Riser

LOCATING PIN

• Locating pins are used for controlled, fine tolerance positioning of a work piece.
• Usually, two locating pins are enough to properly locate the work piece on one plane.
• There are dozens of styles of locating pins that can be utilized in a design.
• Locating pins are a great way to make sure the parts you are putting together fit the way you want them to fit.
• Drill two holes opposite each other in each part, install a cylindrical locating pin, parts are aligned exactly the way we want.
• If we are having alignment issues with using just bolts or other fasteners, a locating pin can be a great way to firm up our assembly.

PIN RETAINER

• A pin retainer is a part which holds the pin in position, the pin retainer can be either a make part or a standard part also.
• Pin retainer is used to hold the locating pins firmly.

SHIMS

• Metal shims are used to finely adjust the location of how the fixture holds the product so that it is welded together within the dimensions set for the product to work well.
• A pack of thin metal shim is placed between two components in the fixture.
• The first component is fixed in place and the second component is attached to the first component with the pack of shims in between,
• Removing one shim or adding one shim slightly adjusts the location of the second component.
• This is important to manufactures who want to have their product parts assemble easily after being welded.

BLADE

• Blade are the plates attached to the riser.
• Parts like cylinder, arms, etc. are mounted on the blade.
• Chamfer is given to straighten the blade.

RISERS

• Riser is a structure generally used to mount the toggle clamp and rest, clamp mylars and locating 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.
• These are generally manufactured to give height to the assembly.

14) What is the purpose of making a rest unit & describe its parts?

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 the 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 & test unit can be combined together in one unit to reduce cost.
• Rest unit is also divided into simple support unit, multiple support unit & retractable support unit.
• The different parts of rest unit are.

1. NC blocks/ Mylars
2. Spacers
3. Blade
4. Riser

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 won’t allow the deformation of the part due to welding stresses.
• Mylars are of two types such as Clamping mylars and Resting mylars.
• Only resting mylars are seen in resting unit.
• The panel which rests on the part is known as resting mylars.

SPACERS/SHIMS

• Metal shims are used to finely adjust the location of how the fixture holds the product so that it is welded together within the dimensions set for the product to work well.
• A pack of thin metal shim is placed between two components in the fixture.
• The first component is fixed in place and the second component is attached to the first component with the pack of shims in between,
• Removing one shim or adding one shim slightly adjusts the location of the second component.
• This is important to manufactures who want to have their product parts assemble easily after being welded.

BLADE

• Blade are the plates attached to the riser.
• Parts like cylinder, arms, etc. are mounted on the blade.
• Chamfer is given to straighten the blade.

RISERS

• Riser is a structure generally used to mount the toggle clamp and rest, clamp mylars and locating 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.
• These are generally manufactured to give height to the assembly.

15) What are the basic fundamentals to design a sensor unit?

SENSOR UNIT

• It is designed to sense car panel using electrical sensor.
• The signal of the sensor will be fed to the PLC & so next process will be executed.
• Sensor unit are used actually in sensing whether panel are there or not or the particular component is there or not.
• Suppose there are 9 numbers of part required for assembly then we should have that no. of sensor at least.
• Whenever operator manually assembly entire component they do the process like fastening, gluing.
• The sensor will show that particular component is there or if components is missing it will give an error.

Fundamentals of sensor unit design are as follows.

• Every signal loose panel which are being welded in tool.
• Each panel should be sensed by 1 to 2 sensor depends on size of panel, preferred to be in diagonal opposite ends of panel.
• Every sensor should be mounted in 3 directions adjustable way in general.
• Some major sensor manufacturers are IFM, Pepperi-fuchs, SICK, OMRON, etc.

TYPES OF SENSORS

Proximity Sensor

• It has sensing range 5 to 6mm. It is based on magnetic field principle.
• A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact.
• A proximity sensor often emits an electromagnetic filed or a beam of electromagnetic field or a beam of electromagnetic radiation (infrared, for instance) and looks for changes in the field or return signal.

Laser Sensor

• It has sensing range is farther away from proximity sensor.

Photo electric sensor

• A photoelectric sensor is equipment used to discover the distance, absence or presence of an object by using a light transmitter, often infrared and photoelectric receiver.
• They are largely used in industrial manufacturing.

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

ROUGH LOCATORS

• Rough locators are usually used in loading & unloading of particular part. It is also used to guide.
• Rough locator unit is a part designed to guide the operator to locate car panel on the pins accordingly.
• They have slot for adjustment. A rough locator can be of standard part or mate part. It also work as poka-yoke

FUNDAMENTALS TO BE CONSIDERED

• Rough locators should be placed at the edge of car panel, which it has to guide using locating pins one can easily restrict movement of entire car panel.
• Rough locator has to be placed in the same angle of the car part edge with minimum distance of 2.5mm from the edge of car part, so it should not damage panel.
• Rough locators should guide the panel before 10 to 15mm to start of the pin engagement.
• It should guide the panel in pin arresting direction in general.
• It should be designed with two slots to mount for easy adjustment.
• The slot should be in the direction of car panel guiding.

17) What is a Base unit and describe its parts?

BASE UNIT

• A base unit is the unit designed to mount all the units such as clamp unit, rest unit, etc. of the tool.
• Also other parts necessary for tool pneumatic valve box, cable path will also be mounted onto a base unit.

PARTS OF BASE UNIT

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

Valve box

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

Trunking Channel

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

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.

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 of cable may then be tied to it for lifting purpose.
• Eye bolt is used to frag or lifts the base unit while relocating.

Pedestal

Pedestal is a stand like structure where the entire unit of the base will be mounted.

Floor Plates

• Floor plates is used to mount the entire base with floor.
• Also, it helps to achieve the flatness of the fixture.

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

DUMP UNIT

• Dump unit is the complex unit to designdue to space constraints there is less space available & have to adjust all the parts in available space.
• It consists of dump cylinder to perform the operation of clamping & unclamping car panel.
• 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 mylar, pins and then this assembly perform 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.

FUNCTIONS OF DUMP UNIT

• If you have particular constraints and you cannot assemble in a normal way to use this in different ways.
• Again, it has same dump cylinder and it has open position, closed position and clamp cylinder unit.

19) What are slide units? Mention where slide units are commonly used?

SLIDE UNITS

• Slide units are positioning units which are used to position the car par or panel, units, weld gun, robots for further operations.
• Slide units may be classified into two types based on the types of guide ways such as Hardened guide way and LM guide way.
• Slide units may further be classified into two types based on the prime mover such as Manual slides, Hydraulic/Pneumatic slides, CNC slides.
• It may be further classified depending on the application as Horizontal slide unit, Vertical slide unit and Angular slide unit.

Basic Fundamentals of Slide unit design

• Reverse stroke 10mm to be considered in both forward and retracted condition.
• Cylinder & LM guides to be validate for load & stroke.
• Master guide way should be constrained and the subsidiary guide way to be free.
• Shock absorber should be used for both extended & retracted condition to reduce impact load.
• Slide to be locked/ clamped in the worked 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.
• LM guide ways to be lubricated for long life.