BIW Fixture Design Methodologies Challenges

1. What is design methodology?

Answer:

Design methodology design methodology is nothing but the steps followed during the concept designing stage of fixture design. Below are the steps followed during design methodology.

1. Purchase order: Purchase order is basically confirmation from customer side that we are ready to start work. A purchase order (PO) is a commercialdocument and first official offer issued by a buyer to a seller indicating types, quantities, and agreed prices for products or services. It is used to control the purchasing of products and services from external suppliers. Purchase orders can be an essential part of enterprise resource planning system orders. 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.
2. Input from customer: Inputs from customer are major input that we get from customer. We study those input to what kind of information get out of it.

Designer needs following basic information to start the BIW fixture.

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

c. Percentage completion Criteria.

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

d. Design Output

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

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

Answer:

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

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

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

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

• Some component like clamp, cylinder, slides, switches, sensors.

Car product: car product include

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

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

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

d) Clamp plan: It provide information about position of clamp unit, pin unit, rest unit etc. this is major input from customer & it should be never be changed without permission of customer.

e) Product assembly process sheet: It gives detail process of the completion of the part from scratch to the finished product assembly. It will give detailed plan of component how they welded as well how product is moving from one assembly to other?

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

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

Weld study: It include information of weld gun detail, weld matrix & weld points. There are two types of weld points geo weld point & respot weld point. Geo weld points defines the geometry of part & respot do all other remaining weld points also add strength to geo weld points.

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

3. What is the input we get from “Car products”?

Answer: Following input we get from car product.

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

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

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

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

e) Product assembly process sheet: Product assembly process sheet is sheet that gives following detail.

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

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

4. What is clamp plan?

Answer: A clamp is a force-actuating mechanism of a fixture. The forces exerted by the clamps hold a part securely in the fixture against all other external forces. Clamping surfaces are subjected to the clamping forces for obtaining invariant location. To fix a part at a particular position, we use 3-2-1 principle in all types of fixtures to restrict degrees of freedom. Each Panel is fixed keeping 3-2-1 principle in mind. This principle requires us to use minimum 3 rests, 2 pins and 1 clamp to fix a panel. While we receive the panel, the customer also gives us the coordinates of panel where he wants us to rest, clamp and locate the panel. We can directly input these coordinates and start designing rests clamps and pins. Clamp Plan document serves this purpose.

Clamp plan provide location of pins, rest, clamp, dump etc. It is in more detail. Clamp Plan is a document that contains the panel drawing mentioning all the places where clamps and rests are to be given. It gives exact location in X, Y, Z co-ordinate values to start designing. We should never change clamp position without permission of customer.

Below fig shows clamp plan.

5. What is the purpose of a layout?

Answer:

Plant layout is plan of an optimum arrangement of facilities including personnel, operating equipment, storage space material handling equipment and all other supporting services along with the design of best structure to contain all these facilities. An overall objective of plant layout is to design a physical arrangement that meets the required output quality & quantity most economically.

It shows all the objects of manufacturing line like robots, Fixtures, Racks etc. & also shows the reach ability of the robot to the fixtures also called the swept area of the robot (indicated by circle around robot). It also shows the constraint of space or the space available for the fixture that we are designing.

Layout provides information about flow of parts, station pitch, robot station, accessories like tool changer & tip dresser, sub assembly links, platform height, loading & unloading sequence.

6. What is ergo data?

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

The final assembly of an automobile involves tasks of complex nature. These processes are on the least priority for automation. Manual labor is best suited for assembly operations with the aid of minimal level of automation. All the processes have to be improved continuously in order to reduce the costs and increase productivity.

The workers attain various postures; exert force and works continuously in cycle time to accomplish the assembly task. Working along automobile assembly lines is characterized by repetitiveness.

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

Below fig show ergo data provided by customer.

7. What do you understand by weld study?

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

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

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

The weld spot locations with respect to the body line of car are as shown in Table 2.

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

Answer:

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

0-25%- Input & concept design:

This is initial stage of project. Input data provided by customer like functional requirement, customer standard etc. & after studying those inputs the concept of fixture design is created. After completion of this tasks about 25% of work completed.

25-40%- Concept approval & simulation check:

As concept of fixture design is created & simulation checked it is sending for customer approval. Customer will study 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 of simulation contributes only 15% of total design work. But with completion of this task 25-40% works completed.

Design freezing & detailing- 40 to 85%:

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

Check & final dispatch- 85 to 100%:

After detailing the quality checking team starts inspection of all the data & it will dispatch to the customer if it is ok as per customer standard. If there is in error in drafting it will create issue or mistake in manufacturing stage.

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

9. Brief about “output” in design?

Answer:

• It includes data to be given to customer after completion of design stage. The output is 3D models & 2D drawings of the tool.
• In the fixture element design output contains detailed design of locators, detailed design of clamps, detailed design of supports, positions of locators, positions of clamp, positions of supports if any, type of locators, types of clamp, types of supports, clamping forces & supports.

• There are two types of tools in fixture design unitized tool & non unitized tool

  In unitized tool there are multiple units on common base for e.g. geo fixture, respot fixture, checking fixture, hemming station etc. Unitized tools require two types of sheet key sheet & layout sheet. Non- unitized tools that can stand alone & can be detailed completely on a layout sheet. E.g. Rack, take out trolleys, turn tables, grippers etc.

• Key sheet: an index of units & their placement on the tool base. Key sheet shows placement & location of that particular unit on tool base where exactly & exact position of tool base. Key sheet is showing orthogonal or isometric view of that entire component.

• Layout sheet: A detailed drawing of individuals units to include all of their units. Layout sheet is detail drawing of that particular tool where we are going detail of component. Grid view in below figure tells that where exactly component is located in geometry. This is also helpful in CMM inspection of fixture.

• The output should compile following point-

a). Approved standard parts should be used wherever possible. This saves lots of time, effort & economical.

b). Design should be as simple & economical as possible. Geometry is complex then fixture designis complex but approach is trying to design as simple as possible.

c). Design must comply with all current safety & ergonomics standard.

d). Design must provide for controlled & damage free handling of product. It should not damage other part.

e). 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. Rough locators work as pokayoke to guide entire panel orientation.

f). 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. There is balance between these two things.

g). Frames & structures are to be simple & sturdy.

h). Design clearance & accessibility for routine maintenance & service. Fixture need to maintain after certain period of time so it is easily accessible for maintenance.

i) Motion control must be considered on any moving component. Adequate to control the motion of component like slider, clamp arm so that it does not give any vibration & stays on particular limit by use of hard stopper, shock absorber.

j). Designer is responsible to validate all clamps & weld guns. So that all clams & gun should perform its function without fail.

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

Answer: Structuring a design tree implies process where all the assemblies & parts are named in specific manner. Different customers have different set of standard like how to structure a design tree? So they will be give standard template based on that design tree structured, which helps us to identify specific part of assembly. It specifies the Project number, station number, unit number; part number of each component so that it is easy to identify the parts.

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

This helps us to avoid error during design study, manufacturing, assembly, inspection etc.

If parts or assemblies are not named properly or the design tree is not structured properly, it will create confusion to understand & create major possibilities of making an error.

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

It can help us to identify quantity of items of same type or different types that are being used in assembly for e.g. bolt. It actually tells you how many bolts are particularly required in that assembly or unit. Below figure shows design tree structure properly & component shown in key sheet. Each unit has a separate name.

Structuring the tree is important as it is easier to differentiate the manufacturing parts from standards, bought outs and hardware’s. Order of tree from top to bottom is: designed or manufacturing parts, after those standards parts from customer, bought outs parts are at bottom as shown in below figure. Every design tree base unit is first unit.

As shown in above figure naming is done as

H1L-T9A: Project name.

RRFRA: Panel name rear panel.

JG3-: Jig no.3

00-00: Unit no, part no respectively.

0R: Right side panel.

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

Answer: Welding line fixtures support, clamp & locate two or more panels of a car body in welding process so that they will get welded accurately at the desired position.

A Fixture may comprise a single or more units where the product will be placed for holding or clamping or locating in order to perform operations like welding or clinching.

A unit, which may has NC block (Mylar), Locating pin, Shim sets, Blade (Dolly Plate), Power clamp, Air cylinder, Riser, Rough locator, Weld gun, Frame etc. to hold or clamp or locate or weld the product at the specified location. According to the 3-2-1 principle of fixture design the units are designed to locate & clamp the car panel to its specified position in fixture while operation is going on.

Ex. Clamping unit, Locator unit, Locating pin unit, Rest unit, Weld gun unit, Base frame unit.

A typical unit is shown below.

Units are categorized as belows.

Unitized tool- Unitized tool are basically tool which is 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.

Non unitized tools: Non unitized tools are basically one unit. It doesn’t have any process functionality in it. It have 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.

Below shortly described unitized tool types.

• 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. It is unit pin is already fixed it cannot 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. Now day’s pneumatic cylinder come with locking mechanism in forward motion. Below are parts in general.

• Clamp unit: Clamp unit is unit designed to clamp / hold the car panel with NC blocks/ mylar/ rest by using a pneumatic clamp cylinder & below are different parts of a clamp unit in general. Usually clamp open position is 90°. 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 knows 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 other units.

12. Describe fixed pin units & their purpose?

Answer:

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

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 & 0.5 mm.

Purpose of fixed pin unit: 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 0.2 mm from its original positional then entire assembly will not happen or get rejected.

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

Answer: Fixed pin unit consist of riser, blade, block, shims or spacer, pin retainer & pin. All parts are described below.

a). Riser: Risers can be of L-type, welded or square tube or frame type. These are basically manufactured parts are used to give height to assembly.

b) Blade: Blades are plates attached to riser. Other part likes cylinder, arms etc are mounted on the blade. Chamfer is given here to strengthen the blade. Two Dowel Four Hole arrangement is used to butt blade to the riser.

c). L-Blocks: L Block is used just to provide the necessary shimming for adjustment. In case of mounting an L block, we should check bolting access as there is already a bolt to tight the pin. Hence, clear hole should be given from L block.

d). Shims/spacer: In fixture, we are providing tolerance to each part mostly manufactured. Those tolerances tend to stack up & reflect together. In order to avoid that we use shims so we can easily adjust after assembly so whatever stack up there we will rectify it through shims. Shims come in thickness of 0.1, 0.2, 0.5 etc.

e). Pin: It is used for the location purpose of the panel. Standard Pins should be used as far as possible and the lengths of pins should be reduced to maximum possible. Generally, pin diameter should be cylindrical grinded to maintain its dimension accurate. 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. We will explain the structure and show an example of how each style can be applied. The different types of Standard Pins are as follows:

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

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

f). Pin retainer: Pin retainer support that pin. 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.

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

Answer:

Rest unit: Rest unit is unit designed to support car panel using Mylar/ NC block/ rest. Component is rested only, no upper clamp or force applied there. It is the simplest unit to design because it has fewer parts to design & the purpose is only resting of the car panel.

Because of this simplicity the rest unit is combined with other unit to reduce the cost of the overall project.

It can be combined with clamp unit to clamp as well as to rest the car panel. It can be combined with locating unit to locate as well as to rest the car panel. Also locating, clamping & rest unit can be combined together in one unit to reduce cost.

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

a). Mylar/ NC blocks/ Fingers: These are parts are used to hold panel. They are globally called as Mylar. Top side Mylar is called as clamping Mylar & bottom side is called resting Mylar. Every clamping Mylar should have resting Mylar. It is jaw type. It prevent panel from deforming while welding. It is hardened to increase its wear strength.

b). Riser: Risers can be of L-type, welded or square tube or frame type. These are basically manufactured parts are used to give height to assembly. It is machined at mounted ends only to save cost.

c). Blade: These are plates mounted on the riser. Other parts like cylinder, arms etc are mounted on the blade.

d). Shims/spacer: In fixture, we are providing tolerance to each part mostly manufactured. Those tolerances tend to stack up & reflect together. In order to avoid that we use shims so we can easily adjust after assembly so whatever stack up there we will rectify it through shims. Shims come in thickness of 0.1, 0.2, 0.5 etc.

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

Answer:

Sensor unit: It is designed to sense car panel using electrical sensor. This signal 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 particular component are there or not. Suppose there are 9 no’s of par require for assembly then we have that no. of sensor at least. Whenever operator manually assemble entire component they do the process like fastening, gluing. The sensor will show that particular component is there or if component is missing it will give an error.

Fundamental of sensor unit design:

• 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 manufactures are IFM, Pepperi-fuchs, SICK, OMRON etc.

Types of sensor used in general.

Proximity sensor- It has sensing range 5 to 6 mm. 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 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 a photoelectric receiver. They are largely used in industrial manufacturing. Below fig shows.

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

Answer:

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

Fundamentals of rough locator design.

• 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 2.5 mm from the edge of car part, so it should no damage panel.
• Rough locators should guide the panel before 10 to 15 mm. to the start of the pin engagement.
• Rough locators should guide the panel in pin arresting direction in general.
• Rough locators should be designed with two slots to mount for easy adjustment. (in general)
• The slot should be in the direction of car panel guiding.

17. What is a base unit & describe its parts?

Answer:

Base unit: A base unit is the unit designed to mount all other units ( clamp unit, pin unit, rest unit) of the tool, also other parts necessary.

For a tool like pneumatic valve box, trucking cable path will also be mounted on to base unit & below are the some part of base unit in general.

a). Base Plate: Base Plate is a machined plate made of steel or Aluminum of thickness 25mm to 40mm on which the holes are drilled to mount different units like rest units, clamp units, pin units etc.

b). Pedestal: Pedestal is a part or an assembly (welded structure) that joins the base plate to the floor plate. Pedestal can be a standard part or a make part, depending on size and height of fixture. Standard pedestals are available in different heights. Pedestals are also available in different inclinations. Depending on the size of base plate; the number of pedestal for a fixture can vary for load distribution

c). Valve box: Pneumatic valve box includes solenoid valve which supplies air to pneumatic cylinder & their coil. Sometimes a bunch of valve is mounted is called as valve blank.

d). Trunking channel: Trunking channel which mounted on base is used to guide all electrical cable, pneumatic pipe. Base support entire fixture unit. Trunking Channel is a duct that carries all the electrical and pneumatic connections (wires and pipes) for units of the tool. It has a thickness of few millimeters.

e). Eye bolt: They are used to lift entire base unit, pedestal to support base plate.

f). Floor plate: They are used to mount entire unit & a leveling arrangement such as leveling bolt & pad are provided to base unit to level the entire unit.

18. What is a dump unit & what are its functions?

Answer:

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

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

Answer:

Slide unit: Sliding unit consist of sliding cylinder. It slides between open & close position. At the end it has shock absorber & after that hard stopper. It has guide rail. It uses sliding mechanism. It also has position locking unit for maintenance purpose doesn’t allow to move entire unit & sensor unit to sense entire component reached at either side or not & stopper block to control moving. When cylinder opens position locking mechanism unlock the panel. Then entire panel move to open position using frictionless guide block. Guide block need to lubricated periodically.

Sliding unit are basically use in places where you have certain constraint, space constraint. Sometimes, there are too many small panels near each other and there is not enough space as each panel requires resting, location using 2 pins, clamping and sensing. This becomes even more difficult when panel is at angles. To solve this problem, a slide unit mounts rest, clamp or pin unit or all of them on a slide using guide rails, guide blocks, a cylinder, locking mechanism, stop blocks and sensors. When a particular panel is to be welded, this slide moves forward, fixes the panel and on completion of operation, slide moves back and gets locked at its position. Similarly, the same is done for other panels.