Week 3:- BiW Fixture Design Methodologies Challenges

Master's Certification in BIW Fixture & Plastic Design

(Automotive BIW Fixture Design)

REPORT

Assignment-3

By Ravi Ahuja

Q1.

Design methodology:

Design methodology is nothing but the steps followed during the concept designing stages of fixture design.

Fig.:Design methodology

1. Purchase order:

A purchase order (PO) is a commercial document and the first official offer issued by a buyer to a seller indicating the type, quantity and agreed prices for products or services. It is used to control the purchase of products and services from external suppliers. Purchase orders can be an essential part of enterprise resource planning system orders.

Purchase order process flow

Let us look at the complete purchase order process flow.

Fig.:Purchase order process flow

The illustrated purchase order process flow is explained below:

• The process begins with recording purchase order basic details and preparing requisitions for internal approval.
• The demand should be approved by the manager or finance department or any other necessary authority before the PO is generated and sent to the supplier.
• The seller or supplier is automatically notified and invited to review the purchase order.
• The supplier either accepts the order or rejects it, in which case a reason must be provided and sent back to the buyer.
• If the seller accepts the order and the delivery date is confirmed, the final details are sent to the receiving department.
• The next steps include receiving the goods, physical verification of the goods, receiving the invoice and making payment to the seller within agreed terms.
• As mentioned, the order process followed by the business differs from each other. It is possible that you may choose not to have illustrated steps based on the needs of the business.

Fig.:An example of purchase order

2. Inputs from customer: Customer Input means suggestions, enhancement requests, recommendations or other feedback provided by Customer or authorized users relating to the operation or functionality of the Service. Following are the inputs which we receive from the customer.
3. Functional requirement
4. Preferred standard components
5. Car products
6. Layout
7. Ergo Data
8. Weld study
9. Standard detailing tempelates

Fig.: Customer input illustrated

3. Percentage completion criteria: The percentage of completion method is an accounting method in which the revenue and expenses of long-term contracts are recognized as a percentage of work completed during the period. This is in contrast to the full contract method, which defers reporting of income and expenses until the completion of a project. The percentage-completion method of accounting is common for the construction industry, but companies in other sectors also use this method.

• The Percentage of Completion method reports revenue and expenses in terms of work completed so far.
• This method can only be used if the payment is assured and the completion estimate is relatively simple.
• The percentage of completion method has been misused by some companies to promote short-term results.

Understanding the Percentage of Completion Method

The percentage of completion method of accounting requires reporting of revenue and expenses on a period-by-period basis, as determined by the percentage of the contract that has been fulfilled. Current income and expenses are compared with the total estimated cost to determine the tax liability for the year. For example, a project that is 20% complete in one year and 35% complete in the second year will only increase revenue by 15% in the second year. The recognition of income and expenses on this work-in-progress basis is applied to the income statement, but the balance sheet is handled in the same manner as the full contract method.

There are two main conditions for the use of the percentage of completion method. First, the collection must be reasonably assured by the company; Second, the company must be able to reasonably estimate costs and project completion rates.

Fig.: Percentage completion method

4. Design output: It is usually 3D models, 2D drawings of tools which are to be given to the customers.

Key sheets: An index of units and their placement on the tool base.

Layout sheets: A detailed drawing of individual units to include all of their components.

Fig.: Output Design sheets

Q2.

The inputs required from the customer to start designing a fixture are as follows,

• Functional requirements.
• Preferred standard components.
• Car products.
• Ergo - data.
• Weld study.
• Standard detailing templates.

Functional requirements: This gives us direct idea about how we should proceed with our design as it tells us about the desired function which is required from the end product. It can be as follows:

1. Welding fixture
2. Hemming fixture
3. Checking fixture
4. Storage racks

Preferred standards: The customer provides us with certain standards which we should maintain at all time while designing. Also we should make use to standard components as much as and wherever we can so that it will save a lot of time and money in designing a new component from scratch and detailing it. Following can be the standards given by customer:

1. Standards like ABB, NAAMS, DESTACO, XYTRAN
2. Standard parts like risers, L- block, retainers, Pins
3. Components like Clamps, Cylinder, Slides, Switches, Sensors
4. Weld guns, Tip dressers, Tool changers

Fig.:NAAMS Codes for clevis assembly

Fig.: ABB Catalog for switches

Car Products: Car products include

1. GD&T
2. Part list
3. CAD files of car parts
4. Clamp plan
5. Product assembly process sheet

Layout sheet: This exactly shows the entire layout or assembly plan with installed robots in it. The plan shows the working are of the robot that is the swept area of robot. This is for understanding of the process.

Fig.:Layout sheets

Ergo Data: When the worker himself will be working on a certain station with the fixture this data helps a designer a lot. This data provides a designer with information like height, reach, working, safety zones, etc. Of the worker so that it will be comfortable for the worker to work on the machine.

1. Ergonomics is the process of designing or arranging workplaces, products and systems so that they fit the people who use them.
2. So from the definition is clear that this data is required where a manual work or a worker will be working on the machine.

Weld study: It consists of information of the weld gun to be used in the operations according to the size and thickness of the part. It also tells about the weld matrix and the number of the welded points.

Standard detailing templates: Detailing is 2D representation of 3D part. Every customer has standard detailing templates which are used for drafting.

Q3.

Car products includes:

1. GD&T
2. Parts lists
3. 3D CAD file
4. Clamp plan
5. Product assembly process sheet
6. GD&T: GD&T, short for Geometric Dimensioning and Tolerance, is a system for defining and communicating design intent and engineering tolerances to help engineers and manufacturers better control variations in manufacturing processes.With functional assemblies, multi-part products, or parts with complex functionality, it is important that all components work well together. All relevant fits and features need to be specified in a way that minimizes impact to the manufacturing process and related investment, while still guaranteeing functionality. High reject rates and tooling changes can increase tolerances by a factor of two by two times or even more. GD&T is the system that allows developers and inspectors to customize functionality without increasing costs.

The most important advantage of GD&T is that the system describes the design intent rather than the resulting geometry. Like a vector or formula, it is not a real object but a representation of it.

For example, a feature standing at 90 degrees from a base surface can be tolerated when it is perpendicular to that surface. This would define two planes, at different distances, that the center plane of the feature should fall within. Or, when a hole is drilled, it makes the most sense to bear it in terms of the alignment of the other features.

Describing the product geometry related to its intended functionality and manufacturing approach is ultimately simpler than describing everything in linear dimensions. It also provides a communication tool with manufacturing vendors, customers as well as quality inspectors.

When performed well, GD&T allows statistical process control (SPC), reducing product reject rates, assembly failures, and the effort required for quality control, saving organizations substantial resources. As a result, multiple departments are able to do more work in parallel because they have a shared vision and language of what they want to achieve.

Fig.:GD&T example

How GD&T works

Engineering drawings are required to show the dimensions of all the characteristics of a part. Next to the dimensions, the tolerance value needs to be specified along with a minimum and maximum allowable range. Tolerance is the difference between the minimum and maximum limits. For example, if we have a table that we will accept with a height between 750 mm and 780 mm, the tolerance will be 30 mm.

However, the tolerance for the table means that we will accept a table that is 750 mm high on one side and 780 mm on the other, or a wavy surface with a 30 mm variation. So in order for the product to be properly tolerated, we need a symbol communicating the design intent of a flat top surface. So we have to include additional flatness tolerances in addition to the overall height tolerance.

Parts with unexpected variations and complex shapes require GD&T practices beyond simple plus-minus tolerance.

Parts with unexpected variations and complex shapes require GD&T practices beyond simple plus-minus tolerance.

Similarly, a cylinder with a tolerable diameter may not necessarily fit into its hole if the cylinder is slightly bent during the manufacturing process. So it also needs straightness control, which would be difficult to communicate with traditional plus-minus tolerance. Or a tube that basically has to match a complex surface that needs surface profile control.

GD&T establishes a library of symbols to express design intentions, which we discuss in the following section.

Dynamic assemblies such as this prosthetic arm require precise tolerances.

Dynamic assemblies such as this prosthetic arm require precise tolerances.

The art of tolerance means specifying only the correct variations for all specific design features so as to maximize product approval rates within the limits of production processes and based on the visual and functional purpose of the part.

In the metric system, there are International Tolerance (IT) grades that can also be used to specify tolerances through symbols. For example, the symbol 40H11 means a 40 mm diameter hole with a loose running fit. The manufacturer only needs to look at the base table for hole features to get an accurate tolerance value.

In addition to individual tolerances, engineers must take system-level effects into account. For example, when a part comes with all dimensions at its maximum permissible price, does it still meet the overall requirements such as product weight and wall thickness? This is called maximum material condition (MMC), while its equivalent is minimum material condition (LMC).

Tolerance also piles up. If we build a chain link where each hole has a 0.1mm plus tolerance and each shaft has a 0.1mm negative tolerance, that means we'll still accept a 20mm length difference on 100 links. When setting up repeating elements such as a punched hole pattern, position the pattern first and then specify interrelated distances rather than having the elements refer to a fixed edge or plane of the part.

Standards not only pertain to designers and engineers, but also tell quality inspectors how to measure dimensions and tolerances. It is important to use specialized equipment such as digital micrometers and calipers, height gauges, surface plates, dial indicators, and a coordinate measuring machine (CMM) for endurance exercises.

When measuring and defining a part, the geometry exists in a conceptual space called a datum reference frame (DRF). It is equivalent to the coordinate system at the origin of a space in 3D modeling programs. A datum is a point, line, or plane that exists in a DRF and is used as a starting place to measure it. Be sure to define the relevant data features for the functionality of your part. Unless you are combining the characteristics of one part with others in the assembly, you can often use the same datum. Always ensure that the primary data has a reliable place to obtain other measurements.

Fig.: GD&T symbols

2. Parts lists: This is a list which contains detailed data of each part which will be used in the assembly. The information may vary but generally consists of:
3. Part number.
4. Part name
5. Revision of cast and pattern, fixture and tools
6. Part thickness

Fig.: Fixture design with parts

Fig.: Fixture design with parts

3. Product assembly process sheet:A process sheet is a set of manufacturing instructions for a specific batch, lot or run.

It describes the operating parameters and settings for the equipment and facilities used and the associated tooling or supply.

The process sheet contains part information, routing information, and operation detail information.

We all know what a blueprint is and how it works, so trust me when I say a process sheet works like a blueprint. This article finds out about all the process sheets and how they are done.

A process sheet is a set of instructions that can be followed to achieve a desired goal. This is a manual which contains the detailed procedure of the works.

This manual focuses on getting the job done systematically, converting raw materials into the final finished product.

Fig.: Product assembly process sheet

Importance of Process Sheet

It not only outlines the detailed mechanism but also describes each event in a step-by-step manner. This is where the importance of manufacturing process sheets lies.

Firms with low output, a complex production pattern, or elaborate and irregular steps must follow a process chart efficiently.

In fact, the process sheet is developed before a firm actually starts operations. It helps in keeping control of operations from day one.

Components mentioned in a process sheet

A process sheet for machining consists of two units, a route sheet

A route sheet is like a map indicating the route to be followed and exactly how the production and management activities were to proceed.

an operation sheet

An operations sheet outlines the step-by-step schedules to be followed, outlines all the materials needed for each job, and maintains a logbook of the items that are or are to come.

It is an irreplaceable tool. It monitors the entire work process for which it is designed.

It keeps a count on the quantity of raw materials required, total processing time, number of workers, specifications of machines working, etc. for each individual component involved in production.

For example, a process sheet document designed to prepare a food item would include each ingredient described in the recipe and the quantity required.

This will include cooking times with a detailed description of each task, the number of workers required in each task, and any comments to follow up on past experiences.

• Structure of the process sheet for manufacturing
• Outline of work sequence.
• This includes locating the assemblies and sub-assemblies involved and creating a map to find where each one fits.
• Determining the number of units to be produced.
• The details of machines, tools and other equipment required along with other details like their efficiency, capacity and running time should be mentioned.
• The sequence of these operations, drawn in detail on a map, develops a clear concept of how raw materials are converted into finished products.
• A certain quality is required during the whole process; That's why quality control instructions are also important.
• Instructions are also mentioned during the movement of products during packing and handling or during processing.

4. CAD files for car parts: Customer provides with the CAD data of the part for which fixture is to be made. After studying the part we get an idea about our fixture design. Basically, the CAD file is base for designing for the fixture.

Fig.: CAD files

Fig.: CAD files

5. Clamp Plan: It provides the location of the pins, rests, clamp, dumps etc. It provides the exact coordinates of the clamps and pins etc. As this is critical input it must not be changed without the permission of the customer.

Fig.:Clamp plan

Q4.

Clamp Plan:

It provides the location of the pins, rests, clamp, dumps etc. It provides the exact coordinates of the clamps and pins etc. As this is critical input it must not be changed without the permission of the customer.

Workpiece Clamping Principle

This is the principle of clamping widely used.

1) 3 pins are used on the bottom

This will restrict 4 rotational motion (X,Y axis) and 1 translation

speed (-Z direction)

2) 2 pins

This will restrict 2 rotational motion (Z axis) and 1 translation

speed in (+X direction)

3) 1 pin

This will restrict 1 translation speed (+Y)

and pin 3-2-1 joint 9 will restrict motion

and the remaining 3 motions are used to set the work-piece to the desired

Can be restricted by location and clamp.

Fig.: 3-2-1 principle

(* Marking given i.e. +X, -X. Varies according to considerations)

need to follow some basic principles or rules

When planning to locate spaces in fixtures, such as

• One or more surfaces (preferably machined) and/or Drilled/Bore hole to be taken for reference
• The reference surface should be critical and important characteristics on the basis of which most Dimensions are set
• Detection should be easy, quick and accurate In case of detection by pins, pins and their mountings and the contact points must be strong, rigid and rigid
• At least three points should be used to detect horizontal flat surface
• The locating pin should be as far away as possible V blocks and cones should be used to perform solid and hollow cylindrical works by themselves Sight space first - applied to the operation producing spaces with irregular surfaces by casting, forging etc when bracket is first located on two sides to machine down
• surface that will be used for detection later.
• Adjustable locating pin(s) to be used accommodate limited portion size variation.

Fig.: Locating by VEE block

General methods of locating

Locating blanks for machining in lathes

In lathes, where the job rotates, the blanks are located

by

• ü fitting into self centering chuck
• ü fitting into 4 – independent jaw chuck and dead centre
• ü in self – centering collects
• ü in between live and dead centres
• ü by using mandrel fitted into the head stock – spindle
• ü fitting in a separate fixture which is properly clamped on a driving plate which is co-axially fitted into the lathe spindle.

Fig.: Pivot arm with two points

Fig.: Job bracket

Q5.

Purpose of layout:

The fixture layout shows the arrangement of the locator and clamp around the workpiece. The position of the locator and clamp is one of the major factors that cause elastic deformation of the workpiece during machining. Identifying optimal fixture layout designs is a viable solution to ensure the final quality of the workpiece by minimizing elastic deformation.

Fig.: Layout plan of a fixture table

Fig.: Complete layout plan

The main function of the machining fixture is to locate, constrain and adequately support the workpiece during machining. These functions are achieved by strategically placing locator pins, clamps, and supports around the workpiece and applying appropriate clamping forces. A poor choice of position of fixture elements and clamping force(s) may be undesirable

Workpiece deformation and low dimensional/form accuracy of the workpiece. Consequently, an important consideration in fixture design is to optimize the fixture layout, i.e. locator and clamp position, so that workpiece deformation due to clamping and machining forces is minimized.

Fixture layout optimization is a procedure to optimize position of locators and clamps in order to minimize specified objectives. Deformation of workpiece is a serious problem of concern while designing a fixture. Proper positioning of fixture elements is indispensable to achieve desired machining accuracy, better surface finish and high productivity. In this work, a novel methodology is proposed that incorporates full factorial design of experiments and statistical analysis. Furthermore, the stability of the workpiece is ensured prior to the prediction of objective function. The result of the proposed technique is compared with the results of the genetic algorithm–based optimization technique. A case study has been considered to evaluate the proposed methodology. The objective function determines maximum elastic deformation of the workpiece during the entire machining process. Finite element method is used to formulate the objective functions. The constraints are natural frequency of the workpiece–fixture system and reaction forces. Besides, artificial neural network–based model is developed to predict the elastic deformation of the workpiece–fixture system within the range of design parameters.

Fig.: Layout design

Q6.

Ergonomics data:

The study of people and their relationships with their surroundings.

When anthropometric data (measurement/statistics) is applied to a product, eg. The hand measurement used to design the shape and size of a handle is ergonomics.

Fig.: Process flow of ergonomics data

Ergonomics involves the study of people and their relationships with their surroundings. This often involves research into the way people interact with products and the environment. Anthropometrical data is used to determine the size, shape and/or form of a product, making it easy to use and easy to use for humans. The ergonomics of a product is usually displayed as the diagram below.

Fig.: Computer workstation and ergonomics in it

For example: When designing a chair, one of the most important factors is comfort. This is closely linked to seating height. Usually the seating height is calculated by measuring the most comfortable height for the person who is going to use the chair. If the chair is to be used by multiple people (such as in a doctor's waiting room), it is important to measure the comfortable seating height for multiple people and then work out the average height. Average seating height is then applied to the chair.

Fig.: Example of a chair

How to Layout an Ergonomics Research Paper

Ergonomics is an important part of research. Everything you design should be suitable for the person who has to use it. For example, if you want to design a door handle you may need to collect statistics about the size of the hands. If you are designing a chair then you need to determine the average comfortable seating height. In the example below, statistics are worked out for the average size of an adult hand. The measurements would then aid in the development of a design for arranging a desk as the overall arm size will determine the overall size of the desk and its compartments.

1. Carefully consider the measurements that need to be collected for your project. An adult's average reach height will need to be determined when designing a book shelf. The average circumference of the wrist will need to be calculated while designing the watch strap.
2. At the top of the page, clearly explain the measurements you want to collect.
3. Draw simple diagrams to show the measurements you want to collect and label the dimensions - A, B, C etc... (see examples)
4. Collect the measurements of at least ten people and complete the table of statistics.
5. Work out the average (average average). This is obtained by counting the total and dividing by the number of people participating. Column 'A' in our example adds up to 1752. This total is divided by 12 as the number of people participating. The answer is the average measurement.
6. Don't collect too many measurements. In the opposite example there is room for four columns of figures, although only two are used.
7. Add notes and labels to the diagrams if you think clarification is necessary.
8. At the bottom of the ergonomics page, clearly state how you want to use the data you collect.
9. The same guidance applies to collecting data about animals. For example, if you are designing an automatic animal feeder, it may be necessary to collect statistics about hamsters or gerbils. Whichever animal you choose, set up an ergonomics research sheet in the same way as seen in the opposite example.

Fig.: Ergonomics research sheet

Q7.

Weld Study:

It consists of information of the weld gun to be used in the operations according to the size and thickness of the part. It also tells about the weld matrix and the number of the welded points.

Type of weld gun used for the operation depends on the size and the thickness of the part. As the customer has already decided these things so it is easy for him to do this study and provide us with the data so that we can make use of this for designing purposes.

Weld locations and weld matrix has data of geo spot and weld spots. This data tells us exactly where and which type of weld will be applied. It shows the geo spots and re- spots with spheres with different colors.

Fig.:Weld study

Fig.: Weld study

Q8.

The criteria for percentage completion in designing stage:

The percentage of completion method is a method of judging construction revenue based on the amount of completed work on longer contracts. It recognizes project income as the progress of the project, usually on a monthly basis.

To calculate the percentage of completion of a project, contractors can use three indicators. By far the most common is cost, but they can also use full units or labor hours. We will go into more detail about this calculation later.

Once the contractor has determined the completion percentage for a project, the percentage is multiplied by the total expected revenue. The answer is the amount of income that can be recognized on the project to date. This income is recognized on the income statement through a work progress report.

Fig.: Percentage of completion method

Using the Percentage of Completion Formula

Fig.Formula

There are three ways to determine the completion percentage of a project. You can find out the POC using:

• Cost,
• units, or
• work hours.

Costs are most commonly used, but some contractors may find that units completed or hours of labor more accurately reflect the completion of their projects. The important thing to remember is that you have to be consistent in how you calculate the absolute percentage.

The percentage of completion formula used to calculate how much revenue can be recognized in a period compares the total cost on the project with the total estimated cost. The total percentage of the cost incurred is the percentage of completion of the project.

Total cost so far Total estimated cost = Percentage completed

For example, a project that has an estimated cost of $100,000 has already incurred $50,000 in costs. Dividing the cost ($50,000) by the total estimated cost ($100,000), gives a 50% completion percentage.

$50,000 $100,000 = 0.5 (50%)

This means that half of the total revenue for the project can be recognized. If the contract is for $120,000, $60,000 can be included in the income statement.

The above calculation seems very simple. But when orders of change are included and estimates change as the project progresses, the calculations can become quite complex.

The work progress report provides a summary of the information used in the percentage of completion calculation. This includes the total revised contract amount, the total cost so far, the percentage completed on a cost basis, the amount billed to date, and the difference between the amount billed and the percentage of revenue recognized.

When the amount billed till date exceeds the revenue recognized by the percentage of completion method, it is called overbilling. Because the contractor billed more than it should, over-billing is recorded as a liability on the financial statements.

If the amount billed so far is less than the revenue recognized by the percentage of completion method, it is called underbilling. That amount is recorded as an asset, because there is more money owed than the bill.

These differences in billing amounts are recorded in the general ledger as journal entries. They increase or decrease the amount of revenue recognized on the income statement and create an asset or liability on the balance sheet.

These adjustments ensure that the income shown on the income statement reflects the percentage of the completion method.

Fig.: Example for percentage of completion method

Mistakes to Avoid When Using Percentages of Perfection

• Since income recognition is based on a percentage of the revised contract for each project, it is imperative that change orders are entered into the system as soon as they are approved.
• If work is added to a project and not recorded in accounting software, the project may be over-billed based on a percentage of the cost.
• Ensuring that contract amounts and estimates on work in progress reports are accurate, ensures that income is reported correctly and avoids penalties for over-billing.
• Overbilling a project to increase cash flow reduces the amount of income a company earns for that period. Higher billing amount will reduce income. If a company consistently over-bills, they will have trouble covering costs when projects are completed. There will not be enough in the balance of the contract to cover the costs at the end of the project. The best bet is to bill the correct percentage of completion and look at other ways to improve cash flow.
• Underbilling projects is also not a good practice. Decreasing the amount billed means you may not be able to cover expenses for that period, which can lead to cash flow problems. Best practice is to bill at the correct percentage of completion.

Q9.

Output in design:

• Approved standard components are to be used wherever possible.
• Design must be simple and economical.
• It must comply with all current safety and ergonomic requirements.
• It must provide for controlled and damage free handling of the product.
• Adequate error proofing must be provided.
• Weight must be kept minimum while maintaining maximum and service.
• Frames and structure are to be simple and study.
• Design clearance and accessibility for routine maintenance and service.
• Motion controlled must be considered on any moving equipments.
• Designer is responsible to validate clamps and all weld guns.

Fig.:Output design

Q10.

Design tree:

This palette helps the designer to locate any used design object within the design file. This is a comprehensive selection device using a folder tree similar to Windows Explorer, enabling the location of everything from hardware devices down to individual controls within control panels. The tree is organised by various categories of design object types to aid in finding items.

If an object selected in this list is within a currently visible design window then a single click will locate and highlight it. Design items can even be found in hidden windows - you don't even have to be in the same layout; in this case double click the item to locate it. London Architect will open the correct window and highlight the object.

This tree is probably the single most important tool used by programmers to build custom control panels. This allows the programmer to quickly navigate around the complete list of controls and graphics available in the default control panels and select elements to incorporate in the custom panels. This eliminates the cumbersome task of navigating around the design file and opening different processing objects to access controls, info boxes or graphics for copying.

Design Categories

This Computer:Allows the designer to assign objectives such as logging out of Architect, show docking windows, online / offline selection or even quitting the application, to control objects.

Control Panels:Shows default and custom Control Panels.

BLU-10 Set-Up Pages:This is a nested tree showing all the folders and pages for any BLU-10s in the design.

Devices:This tree starts with the selection of hardware devices and works down through their associated configurations of processing objects, parameters and settings.

CobraNet Bundles:Shows activated CobraNet bundle settings, as shown in the CobraNet edit box in the Properties for a CobraNet input or output block in the Configuration window.

System Layouts:This is a nested tree; enabling selection of both the Main design window (from any other starting window) and its associated zones. Further down the tree are the hardware devices used in the system and, within them is displayed information relating to the hardware box's settings for display, date and time and 3 wire mode operation of the logic control ports. Also shown is a list of the configurations set up for each device; these contain links to all the processing objects used and their associated control panels. Finally hardware settings for the IO cards and control ports are displayed.

Presets:Displays a list of all the parameter and venue presets in the current design.

Links:Displays a list of all the links in the current design

Key Bindings:Displays a list of all Key Bindings in the design. Key bindings are a way of using keys on your PC keyboard or any external keyboard to control any of the parameters within your HiQnet London Architect design file.

Fig.:Design tree in catia

Fig.:Design tree in catia

Q11.

Units:

A fixture used 3-2-1 principle to hold a work piece in a particular place on which various operations like welding, gluing etc. Will be carried out. This fixture is an assembly of many different type of units. A unit may consist of NC blocks, Riser, Blade, Clamp arm etc. And there are many such units in fixture which has different functions. Thus a unit is a device which has a unique function. Thus a unit is a device which has unique function and is a component of a fixture.

The unit can be classified as below:

1. Rest unit
2. Fixed pin unit
3. Retract pin unit
4. Rough locator
5. Sensory unit
6. Base unit

Fig.: Units used in industry

1. Unitised tools: They are the ones which have multiple units on a common base for example geo fixtures re-spot fixtures, hemming station etc.

Fig.: Unitised tool

2. Non unitised tools: They stand alone tools for example- rack, take out trolley, turn table etc.

Fig.: Non unitised tools

1. Rest pins units are used to rest the car panel and no other force is applied on it.
2. Fixed pin units use a fixed pin to locate a car panel.
3. Retractable pin unit is one in which the pin can be retracted up and down by certain distance.
4. Rough locator unit is used to guide the operator to locate the panel.
5. Sensor unit uses sensors to sense the panel.
6. Base unit is the unit on which every other unit will be mounted.

Q12.

Fixed units:

Fixed pin unit is a unit designed to locate the car panel using pins. Pin, pin retainer, shims, blocks, blade, riser are the part of fixed pin units in general . pin retainer is used to hold the pin firmly.

The top most part is the fixed pin which will be used to locate the part. The part will have entry hole in which the pin will enter to arrest the motion of the part. The pin is mated to the pin retained just below the pin. The fixed pin unit also makes use of shims which are small in size but very important as they help to avoid stacking up of tolerances.

Purpose of Fixed pin unit: Its main purpose is to locate the part properly using 3-2-1 principle and to arrest the degrees of freedom of the part. The pin arrest the translational motion along 2 axes and rtational motion too.

Fig.: fixed pin unit

Fig.: fixed pin unit

Q13.

Different parts of fixed pin units:

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

• Pin retainer.
• L-block/shim block.

Fig.: Different parts of Fixed pin units

Riser: Riser is a structure generally used to mount the toggle clamp and rest clamp, mylar and location pin and to give the height to the assembly. It is not necessary to have one riser where all parts of clamp or rest or location units are mounted. Generally risers are either made of plate and tube welding together from single gas or cut plate.

Fig.: Riser in fixed pin unit

Blade: Blades are plates which are attached to the riser and other components like cylinder, arm etc are mounted on it.

Fig.: Blades and their position

Shims: These are used to avoid stacking up tolerances and thus keeping the locating pin are a proper position. Generally for the mylar and locating pin adjustment solid shim pack is used. 5mm the shim pack has various options of 0.5mm x2, 1mmx2, makes shim pack.

Fig.:Shims

Pins: The pins are used to locate the part at once position. Usually we use the standard pins which are already available in market. These pins are of different types and size.

Fig.: Pins

Pin retainer: Pin retainer holds the pin in its position.

Fig.: Pin retainers

Q14.

Rest units

A rest unit is used to support the car panel, Also it resists the clamping force of the finger with the help of rest mylars & thus clamp the car panel. Rest unit consist of rest mylars, shim packs, riser. Holding force should be considered while designing a rest unit.

Fig.: Rest units

Different parts of rest units are:

• NC block
• Spacer
• Blade
• Riser

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

Fig.:NC blocks

Riser: Riser is a structure generally used to mount the toggle clamp and rest clamp, mylar and location pin and to give the height to the assembly. It is not necessary to have one riser where all parts of clamp or rest or location units are mounted. Generally risers are either made of plate and tube welding together from single gas or cut plate.

Fig.: Riser

Shim: These are used to avoid stacking up tolerances and thus keeping the locating pin are a proper position. Generally for the mylar and locating pin adjustment solid shim pack is used. 5mm the shim pack has various options of 0.5mm x2, 1mmx2, makes shim pack.

Fig.: Shims

Blade: They are the plates which are attached to the riser and the components like cylinder, arm etc. Are mounted on it.

Fig.:Blade

Q15.

Sensors:

A sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends information to other electronics, often a computer processor. Sensors are always used with other electronics.

Important characteristics of a sensor.

• Accuracy
• Repeatability/Precision
• Sensitivity
• Range
• Accuracy - the degree to which the result of a measurement, calculation, or specification conforms to the correct value or a standard.
• Repeatability/Precision - The reading that varies is repeatedly measured under the same environment.
• Sensitivity/Resolution – the smallest increment detected by the sensor.
• Range – measurement limit of the sensor.

Types of sensors:

Fig.: Types of sensors

Q16.

Rough locators:

Rough locators are elements that aid the operator to guide the car panels while loading onto the fixture and ensure a fool-proof assembly. the locating pins are used to loc' 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. (Usually two locating pins are enough to properly locate the body part on one plane. one of the pins is round, and another one is diamond shaped. This configuration will allow easier loading of body part. The end of each pin has a round or conical shape or is chamfered for the purpose of maintaining work ability such as ease of loading prevention of damage. The taper lead angle is large, 60 degrees or less, for small-size body parts and manual operation. The difference between the locate hole in the panel or body part and the locating pin diameter should be -.05 mm and a tolerance for locating pin should be 0, +.05mm. The dimension from the panel to the locating pin leading end 2straight area3 should be 1 mm. Pins are available in numerous shapes and sizes in a design. There are two configurations for position of locating

pin:

1. keep two dowel pins for positioning as far apart from each other as possible
2. Set the dowel pins in symmetrical positions.

Fig.:Rough locator

Purpose of a rough locator unit

One of the principal purposes of a locating surface is to locate and support the panel surfaces for performing a welding process. This is usually done with the datum surfaces that are reference for locating surface. The dimensions of datum surface are decided by selecting a necessary cross-section from the part drawing. The shape of

locating surface is a form of cross-section of panel. Locating surface is configured to receive panel for setting in a correct position and locating a body part from any surface such as flat, curved, or have an irregular contour. In most applications, locating surface devices locate a panel by its external flat surfaces and flat area, such as% edges, flanges, steps, faces, shoulders, and slots.

Fig.:NAAMS Rough locators

Q17.

Base unit:

A base unit is the unit designed to mount all the other units(Clamp unit, Pin unit, rest unit etc.) of the tool, also other parts necessary for a tool like pneumatic valve box, trunking cable path will also be mounted on to a base unit.

There are 8 parts in base unit:

1. Trunking channel
2. Base plate
3. Valve box
4. Measuring hole cover
5. Eye bolt
6. Pedestal
7. Weld bars
8. Floor plate

Fig.:Base unit

• One could eliminate either the metre or the second by setting c to unity (or to any other fixed dimensionless number).
• One could then eliminate the kilogram by setting ħ to a dimensionless number.
• One could then further eliminate the ampere by setting either the vacuum permittivity ε0 (alternatively, the Coulomb constant ke = 1/(4πε0)) or the elementary charge e to a dimensionless number.
• One could eliminate the mole as a base unit by setting the Avogadro constant NA to 1.
• This is natural as it is a technical scaling constant.
• One could eliminate the kelvin as it can be argued that temperature simply expresses the energy per particle per degree of freedom, which can be expressed in terms of energy (or mass, length, and time). Another way of saying this is that Boltzmann's constant kB is a technical scaling constant and could be set to a fixed dimensionless number.
• Similarly, one could eliminate the candela, as that is defined in terms of other physical quantities via a technical scaling constant, Kcd.
• That leaves one base dimension and an associated base unit, but there are several fundamental constants left to eliminate that too – for instance, one could use G, the gravitational constant, me, the electron rest mass, or Λ, the cosmological constant.

Fig.:Base unit

Q18.

Dump unit:

Dump unit is the complex unit to design due to space contains there is less space available & have to adjust all the parts in available space. It consist of dump cylinder to perform the operation of clamping & un-clamping car panel.

Fig.: Dump unit

Q19.

Slide unit:

lide unit essentially consist of LM guides, Linear cylinder ,front & rear stoppers, front & rear shock absorber, two proximity switches/reed switches for sensing the two end position, bellows or protection cover for rails.

Fig.:Slide units

Slide cylinder: This helps in actuation of the platform from closed position to open position and vice versa.

Sensor unit: This unit senses if the panel has is at its position or not.

Guide rails: This helps n movement of platform between open and close position.

Position lock unit: It locks open and close positions.