Challenge

Base Unit Design Challenges

NNaveen Theja Aluru8 Jul 2020

https://drive.google.com/file/d/1WEejrs_xTf1YS2cSlUYbufzVyvOgG8BN/view?usp=sharing

AIM/OBJECTIVE

1. Design a Base Unit for the units designed for the above challenges with all weldments for the given Car Panel.

2. Design all the other remaining Units required for this Fixture assembly

1.BASE UNIT DESIGN

BASE UNIT

A base unit is the unit designed to mount all the other units like 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.

FUNDAMENTALS OF BASE PLATE DESIGN

A base plate size should cover all the units with its outer periphery inclusding opening.

A base plate is preferred to be designed with respect to BCS coordinates.

A base plate should be drilled with datum holes/measuring holes in line with a pitch of 1000mm in general.

Number of datum holes is depend on the size of the base plate.

Datum holes should be drilled at nominal values of coordinates,and in terms of 50 and 100 in general.

Example - X=100,Y=-600,Z=250

Datum holes should be drilled with dia 100 mm away from outer units.

Datum holes should be covered with cover plates.

Below are the some parts of abase unit in general.

Trunking channel

Base Plate

Valve box

measuring Hole Cover

Eye Bolt

Pedestal

Weld Bars

Floor plate

PEDESTAL

A pedestal is a part which connects the base plate to the floor plate.A pedestal is a standard part in general and in some cased it can be a welded frame integrated with the base plate.

A standard pedestal can be of different height and different sizes.

Depends on the sizes of the base plate,The number of pedestal varies for load distribution.

A pedestal are of different types with different inclinations.

Trunking Channel

Trunking channel is a duct which accommodates all the pneumatic and electrical hoses and wires for the units of the tool.

(or)

Trunking channel is a duct that carries all the electrical and pneumatic connections like wires and pipes for units of the tool.

It has a thickness of few millimetres.

VALVE BOX

Valve box is a standard part which contains all the valves for the pneumatic units.

A valve box is basically a box which supplies air to all the other pneumatic cylinders. it's it's a device which includes a lot of other solenoid valves, so it will have one inlet and one outlet and from that one inlet, all the other solenoid valves will be attached to it. And each solenoid valves will have the input, and then again supplied to the separate cylinder, then again the output will be collected, while this solenoid valves, and again given back to the valve box.

MEASURING HOLE COVERS

Measuring Hole covers is on the base unit which is for measuring purpose.

Measuring hole is drilled over the base plate which having exact coordinates so that all other holes can take reference from it.

The measuring hole number depends on the size of base plate and these holes are covered by using some plates to protect against from dust damage etc.

EYEBOLTS

Eye bolts are used for the transporting of the tool using lift hooks,Fork Lift holes will also be provided in some cases for transporting purpose.

It is to drag the entire unit and relocated.

(or)

Eye bolts are the bolts that are used to lift the fixture for transportation by inserting hooks into them.

For Example we usally use M20 Bolts that are bolted on the base plate.Used for transportation purpose and sometimes forklift holes will be provided.

WELD BARS

Weld bars are to mount it to the floor.

FLOOR PLATE

They are also known as foundation plate.They are grounded by using a fixed bolt 10mm clearance should be given between pedestal base plate and floor plate.

Weld bars need to use after the levelling is done by levelling screw.

Weld bars are steel plates along the sides of the base plate of a pedestal.

Weld bars are used to position the positions permanently.

POINTS SHOULD BE TAKEN WHILE DESIGNING A BASE UNIT

A base plate size should cover all the units with its outer periphery inclusding opening.

A base plate is preferred to be designed with respect to BCS coordinates.

Working height depends on the nature of the manual or robotic welding fixture and for manual fixture we need to consider the working height be 850 - 1100mm and its depending upon the working height of the worker or its about ergonomics.It differs by countries.

A base plate should be drilled with datum holes/measuring holes in line with a pitch of 1000mm in general.

Number of datum holes is depend on the size of the base plate.

Depending upon the Weight of the fixture design unit we need to select the eyebolt size for lifting the base plate.While shifting the fixture units from one place to another they will not damage or damaging any other units.

Datum holes should be drilled at nominal values of coordinates,and in terms of 50 and 100 in general.

Example - X=100,Y=-600,Z=250

Depending upon the component size and weight of the total units you can decide whether you need a fabricated base or a plate.Mostly fabricated bases are used and made of square or a rectangle tube with the plate.

Datum holes should be drilled with dia 100 mm away from outer units.

Datum holes should be covered with cover plates.

The base Unit of the fixture must be strong enough so that deflection of the fixture is as mimum as possible during welding,This Deflection is caused by the forces of welding and while clamping of the panel.

The base unit of the fixture should prevent vibrations and chatter.

DESIGN TREE OF A BASE UNIT

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 structure design tree.

So they will be giving a template on how the structuring and detailing of the design is done. And you have to follow that particular designing or structuring of the tree.

In the design tree itself if we mentioned that particular name, wherever that part is we can easily know that this part belongs to this zone or This station or this assembly on particular unit. So this helps us to avoid errors during the design study,manufacturing assembly and inspections.

Structuring a design tree is actually to avoid all the errors, which might come during manufacturing assembly, or either in house inspections as well.

If the part, or assembly are not named properly, or design tree is not structured properly, it will create confusion to understand the design and may create major possibilities of making an error.

Every part, every component should be named according to their precedures.

If we did a mistake or renamed the entire standard parts from the customer as a design part.Now the customer is going to manufacture the entire part again from the scratch, but he already have that product in his itinerary.but extra cost,extra time and not feasible.this is also known as an error which is actually going to increase the cost of the entire assembly as well.

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

If we name the part properly or name the fixture properly it'll actually tell which unit or which assembly or which zone or in which station it actually belongs.

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

3-2-1 PRINCIPLE

The 3-2-1 principle of location (six point location principle) is used to constrain the movement of workpiece along the three axes XX, YY, and ZZ. This is achieved by providing six locating points, 3 pins in base plate, 2 pins in vertical plane and 1 pin in a plane which is perpendicular to first two planes.

DEGREE OF FREEDOM CONTROLLED BY 3-2-1 PRINCIPLE

3-2-1 PRINCIPLE is the heart of the fixture design and world holding devices.
In BIW FIXTURE design the panels are always fixed with the help of 3-2-1 .because it always minimizes the usage of unwanted components to hold the panels with the help of 3-2-1 principle we can arrest the six degrees of freedom which means six degrees of rotational and six degrees of translational axes .

FIRST PLANE

This is the "3" in 3-2-1. So, three specific points are used to define the first plane.
Fewer than three points cannot define a plane, and in the real world dimensional tolerances mean that four or more points will not be coplanar. A real-world, less than ideally perfect part placed on four or more reference points will, in fact, rest on only three of the points due to its less than perfect surface. Different parts may rest on different combinations of three points, resulting in variation between finished parts.
A stool can be used to illustrate this concept. A two-legged stool would certainly be unstable. A three-legged stool sits rock-solid. A four-legged stool is often found to rock.
In the illustration, a three dimensional part, represented by a cube, is placed on a datum plane defined by three support points. The part’s six degrees of freedom have now been reduced to three. It can still move along the X or Y axes, and it can still be rotated about the Z axis. (The part cannot move along the Z axis because it is held against the plane by clamping force.

TIPS

Use the largest surface of the part for the first ("primary") reference plane.
Position the three support points as far apart as possible.
If more than three support points are required to prevent deflection, make the additional points adjustable.

SECOND PLANE

A second plane, if it is perpendicular to the first, can be defined by two points, the "2" in 3-2-1. The part is now constrained to one degree of freedom: movement along the Y axis. (The part cannot move along the X or Z axes because it is held against the planes by clamping force.

TIPS

Use the largest surface of the part for the first ("primary") reference plane.
Position the three support points as far apart as possible.
If more than three support points are required to prevent deflection, make the additional points adjustable.

THIRD PLANE

A third plane, if it is perpendicular to both of the first two planes, can be defined by one point, the "1" in
3-2-1. The part is now entirely constrained. It cannot move along or rotate about the X, Y, or Z axes. (Remember that the part is held against each of the three planes by clamping force.

WHY

What is the working height?

It depends on the nature of the manual or robotic welding fixture.

For manual fixture you need to consider the working height 850-1100 mm , depending upon the working height of the worker standard of specific country will apply( In few countries human height is higher or lower e.g. US , Japan).

If base structure is made with base plate having tubular structure welded below it you can reach to height 100 mm to ~250 mm.

In this case to reach the working welding height you need to provide additional some leg structure which may have top and plate plate welded to tube.

HOW MANY EYE BOLTS NEEDED?

Depending upon the weight eye bolt size are selected for lifting holes on the base plate.

Generally 4 eye bolt provision is made. we need to select the location of eye bolt considering the rope/ belts used while shifting the structure or complete fixture are not damaging any units(rest,clamp or location units) .

How base plate or base structure handeled during fabrication, machining or during final installation?

As designer its is important to know how big base plate or bigger base welded structure will be handeled during the fabrication and handling process.

2. Design all the other remaining Units required for this Fixture assembly

In this fixture design they are five panels,For each panel a pin unit and one clamp unit is for holding the panel and fix the panel or to restict 6 degree of freedom by using 3-2-1 principle.

Fixture Design Fundamentals

Fixture design consists of a number of distinct activities: fixture planning, fixture layout design, fixture element design, tool body design, etc. They are listed in their natural sequence, although they may be developed in parallel and not necessarily as a series of isolated activities in actual execution.

Fixture design deals with the establishment of the basic fixture concepts:

Fixture layout is an embodiment of the concepts in the form of a spatial configuration of the fixture.
Fixture element design is concerned with the concrete details of the locators,clamps and supports.
Tool body design produces a structure combining the fixture elements in the desired spatial relationship with the machine tool.

FUNCTIONS OF FIXTURE DESIGN

The function of fixture is a holding device of work piece in proper aligns during manufacturing of product. Fixture is supporting, clamping the work piece, its checking, positioning, individual marking and non-uniform quality in manufacturing of product is eliminated by fixture. This increase productivity and reduce operation time. Fixture is basically uses in the industry to increasing production because of feature and advantages.
To locate and immobilize workpieces for machining, inspection, assembly and other operations fixtures are used. The tool is uses in during of inspection of panel assemble.
Fixture is not guide, but is always fixed to production line, various type of machining operation of product is suite on fixture.
The car body is made up of more than of hundreds of stamped sheet metal components which are joined together by spot welding process, accurate production of the car body is essential if the automated assembly line is to fit within the required tolerance, therefore we use the welding fixture.
We can use a different type of units and they have different function in welding fixture design, based on clamping plan, location plan, and simulation.

PIN UNIT DESIGN

The purpose of pin unit design is necessary to have 2 pins to locate a car panel & here one pin must arrest 4 way(4 translational)and other arrest 2 way(i.e. 2 rotational) of a car panel by using 3-2-1 principle.

FUNDAMENTAL OF PIN UNIT

It is necessary to have 2 pins to locate a car panel & here one pin must arrest 4 way(4 translational)and other arrest 2 way(i.e. 2 rotational) of a car panel.
The axis of the car panel hole and the axis of the pin should be same.
Pin tolerance for a geopin will be of closer tolerance i.e. -0.15mm & for the re-spot pin is -0.28mm.
The pin should engage 3 to 5mm from the car part entry surface.
All pin should be accommodated with 2way adjustable shims irrespective of the direction of arresting.
Round pin should be used in case of 4way arresting of car panel if the hole is round.
Round pin can be used for 2way arresting of car panel only if the hole is a slot.
Diamond pin should be used in case of 2way arresting of car panel if the hole is round.
Diamond pin should be used in case of 4way arresting of car part if the hole is slotted
The axis of the car panel hole & the axis of the pin should be the same.

ASSEMBLY OF FIXTURE DESIGN

In this process to different type units are mounting at base plate of fixture, such as clamp unit, locating unit , sliding unit, dump unit they have different mechanism in fixture.
The orientation units of the fixture depend on shape of product also decided based on the weld spot points.
The spots point at panel - Roof, floor panel assembly is located with respect to the body line of car.

TYPES OF PIN UNITS

Fixed Pin Unit
Retractable pin unit

1.Fixed Pin Unit

In the Fixed unit consists of pin,pin retainer,shims,blockblade or adaptor plate and riser.

The totally different standards so same, a pin, pin retainer blade, or a block, so here they have replaced the block with just a single blade. And this is also

Usually in the industry they tend to use the shims which are of smaller size.that's where they're manufactured like this always preferred as much as less material as possible. That's why we design it as small with these kind of shapes.

FUNDAMENTAL OF A FIXED PIN UNIT

It is necessary to have 2 pins to locate a car panel & here one pin must arrest 4 way(4 translational)and other arrest 2 way(i.e. 2 rotational) of a car panel.
The axis of the car panel hole and the axis of the pin should be same.
Pin tolerance for a geopin will be of closer tolerance i.e. -0.15mm & for the re-spot pin is -0.28mm.

The pin should engage 3 to 5mm from the car part entry surface.
All pin should be accommodated with 2way adjustable shims irrespective of the direction of arresting.
Round pin should be used in case of 4way arresting of car panel if the hole is round.
Round pin can be used for 2way arresting of car panel only if the hole is a slot.
Diamond pin should be used in case of 2way arresting of car panel if the hole is round.
Diamond pin should be used in case of 4way arresting of car part if the hole is slotted
The axis of the car panel hole & the axis of the pin should be the same.

REQUIREMENTS NEED TO TAKEN WHILE DESIGNING THE PARTS

Pin is the part which locates the car panel. It can be a make part or standard part.
Pin should be grinding surface on a shaft with fits on to which the pin retainer will be fitted.
Pin must have a provision like tapped hole from the bottom or V GROOVED
A pin must be hardened and black oxide finished.
The mounting surface of the pin should be a finely machined surface.
The pin should have a step machine surface to lock the rotation, which matches with the pin retainer.

FORMULA AND CALCULATION

Formula to calculate The length of the screw be

Length of the screw = [1.5 x (standard Hole Size ) + (stance between the surface of the part to the closest surface of another part)]

DESIGN TREE OF FIXED PIN UNIT

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 structure design tree.
So they will be giving a template on how the structuring and detailing of the design is done. And you have to follow that particular designing or structuring of the tree
In the design tree itself if we mentioned that particular name, wherever that part is we can easily know that this part belongs to this zone or This station or this assembly on particular unit. So this helps us to avoid errors during the design study,manufacturing assembly and inspections.
Structuring a design tree is actually to avoid all the errors, which might come during manufacturing assembly, or either in house inspections as well.
If the part, or assembly are not named properly, or design tree is not structured properly, it will create confusion to understand the design and may create major possibilities of making an error.
Every part, every component should be named according to their precedures.
If we did a mistake or renamed the entire standard parts from the customer as a design part.Now the customer is going to manufacture the entire part again from the scratch, but he already have that product in his itinerary.but extra cost,extra time and not feasible.this is also known as an error which is actually going to increase the cost of the entire assembly as well.
Naming a fixture or a unit or a part gives the information as to which project zone or assembly do they belong.
If we name the part properly or name the fixture properly it'll actually tell which unit or which assembly or which zone or in which station it actually belongs.
It can help us to identify the quantity of items of same types or different types that are being used in an assembly.

DIFFERENT TYPES OF PARTS IN POWER CLAMP UNIT

1.Blocks

Blocks (red for representation) 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.

2.Pin Retainer

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

3.RAISER

The geometrical shape of riser block is according to flame cut and maintain the height of unit to the clamp point on panel.

The cylinder is mounted on machining face of riser through the screw.
The riser is a standard part,Which provide height to the pin unit,Clamp Unit as per requirements,The riser should have adequate strength so it can sustain under a load of car panel,clamping Cylinder,Blades.

4.SHIMS

A shim is a thin and often tapered or WEDGED piece of material, used to fill small gaps or spaces between objects.

Shims are typically used in order to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gaps between parts subject to wear
The function of shim is adjustable in any direction such as X, Y, Z direction through the locator on units.

MATERIALS USED

Mylars
UHMW, Nylon66, PP, Teflon (polytetrafluoroethylene (PTFE)). Materials of clamp block and rest block to be decided as per the A class panel or B class.
Most of the exterior panel holding Teflon material is used. Otherwise, steel is used with heat treatment.Sometimes Aluminium blocks are also used.

Clamp arm
SAE 4140 or SAE 1045.

Shims/spacer
S.A.E. 1010 CRS FULL HARD, COLD ROLLED STRIP STEEL S.A.E. 1010 FULL HARD, S.A.E. 1020 HRS, etc.

Shim block
STEEL ASTM A-36, NM Stainless, STEEL ASTM A-36, SS type 303 or 304, etc.

Blade
STEEL ASTM A-36, etc.

Riser
STEEL ASTM A-36, etc.

2.RETRACTABLE PIN UNIT

In this type,There is the provision of moving of pin in the up abd down direction.

Retractable pin is a unit design and it is located in the car panel using pins,which has same function as the fixed pin unit, but the entire pin package part will be mounted on the retractable pneumatic cylinders.

So this is the pneumatic cylinder which is responsible for retracting the pin. So it has also same parts up in Shims or spacers. Again with the both sides pneumatics single rod retractable cylinder and the riser.
Usually in the industry they tend to use the shims which are of smaller size.that's where they're manufactured like this always preferred as much as less material as possible. That's why we design it as small with these kind of shapes.

FUNDAMENTAL OF Retractable PIN UNIT

It is necessary to have 2 pins to locate a car panel & here one pin must arrest 4 way(4 translational)and other arrest 2 way(i.e. 2 rotational) of a car panel.
The axis of the car panel hole and the axis of the pin should be same.
Pin tolerance for a geopin will be of closer tolerance i.e. -0.15mm & for the re-spot pin is -0.28mm.
The pin should engage 3 to 5mm from the car part entry surface.
All pin should be accommodated with 2way adjustable shims irrespective of the direction of arresting.
Round pin should be used in case of 4way arresting of car panel if the hole is round.
Round pin can be used for 2way arresting of car panel only if the hole is a slot.
Diamond pin should be used in case of 2way arresting of car panel if the hole is round.
Diamond pin should be used in case of 4way arresting of car part if the hole is slotted
The axis of the car panel hole & the axis of the pin should be the same.

REQUIREMENTS NEED TO TAKEN WHILE DESIGNING THE PARTS

Pin is the part which locates the car panel. It can be a make part or standard part.
Pin should be grinding surface on a shaft with fits on to which the pin retainer will be fitted.
Pin must have a provision like tapped hole from the bottom or V GROOVED
A pin must be hardened and black oxide finished.
The mounting surface of the pin should be a finely machined surface.
The pin should have a step machine surface to lock the rotation, which matches with the pin retainer.

DESIGN TREE OF Retractable PIN UNIT

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 structure design tree.
So they will be giving a template on how the structuring and detailing of the design is done. And you have to follow that particular designing or structuring of the tree
In the design tree itself if we mentioned that particular name, wherever that part is we can easily know that this part belongs to this zone or This station or this assembly on particular unit. So this helps us to avoid errors during the design study,manufacturing assembly and inspections.
Structuring a design tree is actually to avoid all the errors, which might come during manufacturing assembly, or either in house inspections as well.
If the part, or assembly are not named properly, or design tree is not structured properly, it will create confusion to understand the design and may create major possibilities of making an error.
Every part, every component should be named according to their precedures.
If we did a mistake or renamed the entire standard parts from the customer as a design part.Now the customer is going to manufacture the entire part again from the scratch, but he already have that product in his itinerary.but extra cost,extra time and not feasible.this is also known as an error which is actually going to increase the cost of the entire assembly as well.
Naming a fixture or a unit or a part gives the information as to which project zone or assembly do they belong.
If we name the part properly or name the fixture properly it'll actually tell which unit or which assembly or which zone or in which station it actually belongs.
It can help us to identify the quantity of items of same types or different types that are being used in an assembly.

DIFFERENT TYPES OF PARTS IN POWER CLAMP UNIT

1.Blocks

2.Pin Retainer

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

3.RAISER

The geometrical shape of riser block is according to flame cut and maintain the height of unit to the clamp point on panel.

The cylinder is mounted on machining face of riser through the screw.
The riser is a standard part,Which provide height to the pin unit,Clamp Unit as per requirements,The riser should have adequate strength so it can sustain under a load of car panel,clamping Cylinder,Blades.

4.SHIMS

A shim is a thin and often tapered or WEDGED piece of material, used to fill small gaps or spaces between objects.

Shims are typically used in order to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gaps between parts subject to wear
The function of shim is adjustable in any direction such as X, Y, Z direction through the locator on units.

5.CYLINDER SELECTION

Pneumatic system-

System operated with Air.
Open loop system
Generally used for low pressure
Generally deliver es less force compared to hydraulic system
Cheaper compared to hydraulic for basic cost. But compressor running cost is more

Hydraulic system-

System operated with fluid- oil.
Closed loop system
High pressure system
Generally used for heavy force delivery
Initial cost is high
More expensive

3.CLAMP UNIT DESIGN

The clamps are hold the panel through clamp arm and manufacturing part and prevent the part from distortion while carrying out the welding on panel.

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

They are two types of clamp units different by choosing the cylinders type.

CLAMPING PRINCIPLE

In every machining operation, clamping of workpieces is an essential requirement.A clamp can be defined as a device for providing an invariant location with respect to an external loading system.

In other words, the process of clamping induces a locking effect which, through frictional or some other forms of mechanism,provides a stability of location which cannot be changed until and unless external loading is able to overcome the locking effect.

Hence, when a cutting force is producing a load or moment on the workpiece, it is necessary that a sufficient clamping force must be exerted to withstand such actions. The creation and retention of locking effect against external loads are the principal objectives of any locking devices.

To provide a suitable locking for achieving the stability of location.
To produce sufficient frictional effects for the above purpose but without causing any undesirable effects to the workpiece such as distortion or surface damage.
The clamping devices must be easy to manipulate manually or otherwise,These devices must be quick-acting so as to reduce time for setting the clamping and simultaneous locating.
They must be low-cost so that their application in small lot sizes iseconomical.

TYPES OF CLAMP UNIT

They are two types of clamp units different by choosing the cylinders type.

1.POWER CLAMP UNIT

2.SWIVEL CLAMP UNIT

1.POWER CLAMP UNIT

A clamp unit is a unit designed to clamp or hold the car panel with NC blocks/mylars/rest by using a pneumatic cylinder. Clamp arm, finger, Rest or backup,L-Block,shims,Riser,Pneumatic cylinders are the typical parts of clamp unit.Clamping force should be considered while designing a clamp unit.

Purpose of Clamp Unit

The purpose of clamping tools is to securely hold the workpiece in position without obstructing the production process and High clamping forces.

Factors should be Consider While Designing A Clamp Unit

There should be adequate space between the Cylinder and another part like riser,Car panel,Cylinder because Cylinder moves Or swings while loading and unloading or opening and closing.
Pin Clamp Unit is Used where two panels or components are located and Clamp for welding.
Clamp make in such a way that it clamps two car panel ar once.
Every Clamp Mylar or Nc Block Should have Rest Mylar For Holding the car panel.
Clamp Unit has shims in only one direction and Pin clamp unit have shims in both directions.
All parts should snap and butt properly each other.
Make sure that all the parts of the clamping unit are minimum of 10 to 12 mm away from the car panel,So that they do not damage the car panel.
Design tree should be structured properly with easy identification or it should be structured in a way that makes a part on the top and followed the standard part.
In this design 63D bore and 100mm Stroke Size Clevis Clamp Cylinder are Used.
Avoid any clash,It will not rise issue at assembly.
The Product should design in such a way that it will easy to make,assemble and wuality check.
We should preferably use quick clamps and the clamping method should not damage the worlpiece.The clamp should open in such a way that clamp arm moves away from the operator.
Avoid sharp edges and corner,They can harm the operator and causes to the serious injury,In that case provide chamfer or fillet at the corners of designed parts.
Must possess sufficient rigidity and robustness.It should not vibrate or any movement of the workpiece and tools.
Pin should be 3 to 5 mm above the car panel.remaining all parts should be 12mm away from the panel.
Must ensure total security in the operation.

DESIGN OF POWER CLAMP UNIT

1.PLP (Principle Location Points) is given by customer.

Shimming is depending on the angle between of cross section of panel and locator General rule if the section is inclined more than 15deg or clamping surface is 3D profile then 2 direction shimming are provided otherwise one direction shimming.

Process engineer have decided to gun shape stick to X, C type of gun. Do the proper study of gun and weld point.

Panel section is passing through the PLP either in opening condition or closing condition .Panel section through X, Y or Z direction passing through PLP. Section will help in finalizing the shape of clamp and rest locator. The panel touch to face of locator is machining and Harding face.

Finalization of a base plate plane – consider following things before deciding the base plate. Height of maximum and minimum weld spot from the floor. No gun arm should touch the base plate. Operator ergonomic while accessing all the spots.

Construction of Rest and Clamp Locator: If standard Mylar has to be used (Few companies make standard height and length of steel blank with few holes and dowels for clamping) then select the proper blank size as per the requirement; consider 5 mm above the panel.

Select the clamping cylinder as per the pivot point distance from the PLP. You may choose various cylinder 45 ∘, 60∘, 90 ∘, 30 degree opening as per the requirement (distance of clamp arm from the PLP and no of clamping mounted on each cylinder).

DESIGN TREE OF POWER CLAMP UNIT

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 structure design tree.
So they will be giving a template on how the structuring and detailing of the design is done. And you have to follow that particular designing or structuring of the tree
In the design tree itself if we mentioned that particular name, wherever that part is we can easily know that this part belongs to this zone or This station or this assembly on particular unit. So this helps us to avoid errors during the design study,manufacturing assembly and inspections.
Structuring a design tree is actually to avoid all the errors, which might come during manufacturing assembly, or either in house inspections as well.
If the part, or assembly are not named properly, or design tree is not structured properly, it will create confusion to understand the design and may create major possibilities of making an error.
Every part, every component should be named according to their precedures.
If we did a mistake or renamed the entire standard parts from the customer as a design part.Now the customer is going to manufacture the entire part again from the scratch, but he already have that product in his itinerary.but extra cost,extra time and not feasible.this is also known as an error which is actually going to increase the cost of the entire assembly as well.
Naming a fixture or a unit or a part gives the information as to which project zone or assembly do they belong.
If we name the part properly or name the fixture properly it'll actually tell which unit or which assembly or which zone or in which station it actually belongs.
It can help us to identify the quantity of items of same types or different types that are being used in an assembly.

DIFFERENT TYPES OF PARTS IN POWER CLAMP UNIT

CLAMP CYLINDER

In this project i used APH_50_BR5_A40_T12_TUENKERS

A compact clamp with curve-driven lever mechanism for constant clamping force and tension reverse,
Enclosed mono-block housing of aluminium material with integrated mechanics and flat cylinder Sizes be 50/63/80.
Forked clamping arm with standard hole pattern for adapting contour blocks, continuously adjustable opening angle 15°-135°, Pneumatic cushioning for an open position.

Clamp cylinders are bought out parts. Some of the manufacturers are Tunkers, Zytran, Destaco, Festo, Steel smith.

Clamp cylinders are generally 50, 63 & 80 bore capacity.
Open up to 135 degrees for horizontal clamp mounting.
Open up to 105 degrees for vertical clamp mounting.

CYLINDER SELECTION

Pneumatic system-

System operated with Air.
Open loop system
Generally used for low pressure
Generally deliver es less force compared to hydraulic system
Cheaper compared to hydraulic for basic cost. But compressor running cost is more

Hydraulic system-

System operated with fluid- oil.
Closed loop system
High pressure system
Generally used for heavy force delivery
Initial cost is high
More expensive

Pneumatic system is mostly preferred over hydraulic system in BIW welding fixture.

All toggle clamp , pin cylinder, slides are operated via pneumatic.

Generally cylinder are designed to operate max pressure 12-13 bar. As it expensive and difficult to maintain 10-12 bar in shop floor it is preferred to do design pneumatic systems at 6 bar pressure

2.FINGERS/MYLERS

A finger is an NC Block or mylars,Which is mounted on clamp arm of the cylinder and It is used to hold car panel by pressing the car panel towards the rest and In between these fingers we are placing car panel.

In this one rest myler and one clamp myler or finger need to hold the car panel.

In this design i used two fingered mylers because of two fingered clamp it is to hold the car panel without any vibrations and the stability is high.

Mylars are also called as NC blocks
In German language,They calling mylar as COUNTER STEIN.
Mylars plays a major important role in BIW fixture design.
Mylars are Made of Steel or In plastic material.
Rest is an NC blcok,Which is fixed to the unit to support the car panel.
It resists the clamping forces of the Finger.

3.CLAMP ARM/LOCATOR

A clamp arm is taking part,It is made as per the position of the clamp cylinder,Stopper and shim,Clamp arm made from hard steel.

Locator is a movable part through the mechanism of cylinder which is used to hold the panel from top against the Back-up and they are usually mounted on the clamp arm.

4.PLATE

Any Shaped Plate used to mount the locator to clamp arm, besides allowing adjustment for locator in two directions shimming.

5.RAISER

The geometrical shape of riser block is according to flame cut and maintain the height of unit to the clamp point on panel.

The cylinder is mounted on machining face of riser through the screw.
The riser is a standard part,Which provide height to the pin unit,Clamp Unit as per requirements,The riser should have adequate strength so it can sustain under a load of car panel,clamping Cylinder,Blades.

Important things which you need to keep in mind while designing riser

1) It should be firmly mounted on base plate. Should have enough no of bolts with proper grade for fixations and dowel for position location.

2) Height should not be too small or too high. Maintain the height to resting width ratio.

3) Ensure that riser mounted considering surrounding space around other units.

Ensure that there is enough space for spanner to unscrew riser.

4) It is recommended to avoid decimal coordinate of riser mounting on base plate.

5) Select proper bolt and dowel sizes for mountings of riser on base plate.

6) Select colour or powder coating as per the company requirement. Do not forgot to apply red oxide before paintings.

7) Do not paint machined faces? Take proper care while paintings.

8) Ensure proper dowel tolerances on the riser. (refer the Tolerances for Risers and Mylars in the “Tolerance for Riser and Mylar” blog topic )

6.SHIMS

A shim is a thin and often tapered or WEDGED piece of material, used to fill small gaps or spaces between objects.

Shims are typically used in order to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gaps between parts subject to wear
The function of shim is adjustable in any direction such as X, Y, Z direction through the locator on units.

MATERIALS USED

Clamp arm
SAE 4140 or SAE 1045.

Shims/spacer
S.A.E. 1010 CRS FULL HARD, COLD ROLLED STRIP STEEL S.A.E. 1010 FULL HARD, S.A.E. 1020 HRS, etc.

Shim block
STEEL ASTM A-36, NM Stainless, STEEL ASTM A-36, SS type 303 or 304, etc.

Blade
STEEL ASTM A-36, etc.

Riser
STEEL ASTM A-36, etc.

WHY

Why 40mm or 50mm thick base plate?

If we go for higher thickness it will not bend after machining and will have good flatness.

Few OEM's recommend thick base plate 40mm or 50mm for the child part assemblies for example BMW). 40/50mm plate makes a very heavy structure but some OEM's follow methodology.

WHY Dowel Holes Used For Biw Fixture Design

In automobiles, dowels are used when precise mating alignment is required, such as in differential gear casings, engines, and transmissions. Bolts in a bolted joint often have an important function as a dowel, resisting shear forces. For this reason, many bolts have a plain unthreaded section to their shank.

How many dowel holes (measuring holes) required for base plate or base structure?

Most of the OEM makes 4 dowel holes at 4 corners and put small aluminum plate marking X,Y &Z coordinates of dowel holes.

Why minimum Shim size 0.5 needed?

A product designer who has designed all these sheet metal components. Normally the sheet metal profile tolerance is of 0.5mm in automotive components.

2.SWIVEL CLAMP UNIT

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

Clamp arm, finger, Rest or backup,L-Block,shims,Riser,Swivel cylinders are the typical parts of Swivel clamp unit.
Most of the Indian OEM's using Swivel Type clamp units in there fixtures.

Purpose of swivel Clamp Unit

The purpose of clamping tools is to securely hold the workpiece in position without obstructing the production process and High clamping forces.

Factors should be Consider While Designing A SWIVEL Clamp Unit

There should be adequate space between the Cylinder and another part like riser,Car panel,Cylinder because Cylinder moves Or swings while loading and unloading or opening and closing.
Pin Clamp Unit is Used where two panels or components are located and Clamp for welding.
Clamp make in such a way that it clamps two car panel ar once.
Every Clamp Mylar or Nc Block Should have Rest Mylar For Holding the car panel.
Clamp Unit has shims in only one direction and Pin clamp unit have shims in both directions.
All parts should snap and butt properly each other.
Make sure that all the parts of the clamping unit are minimum of 10 to 12 mm away from the car panel,So that they do not damage the car panel.
Design tree should be structured properly with easy identification or it should be structured in a way that makes a part on the top and followed the standard part.
In this design 63D bore and 100mm Stroke Size Clevis Clamp Cylinder are Used.
Avoid any clash,It will not rise issue at assembly.
The Product should design in such a way that it will easy to make,assemble and wuality check.
We should preferably use quick clamps and the clamping method should not damage the worlpiece.The clamp should open in such a way that clamp arm moves away from the operator.
Avoid sharp edges and corner,They can harm the operator and causes to the serious injury,In that case provide chamfer or fillet at the corners of designed parts.
Must possess sufficient rigidity and robustness.It should not vibrate or any movement of the workpiece and tools.
Pin should be 3 to 5 mm above the car panel.remaining all parts should be 12mm away from the panel.
Must ensure total security in the operation.

DESIGN OF SWIVEL CLAMP UNIT

1.PLP (Principle Location Points) is given by customer.

Shimming is depending on the angle between of cross section of panel and locator General rule if the section is inclined more than 15deg or clamping surface is 3D profile then 2 direction shimming are provided otherwise one direction shimming.

Process engineer have decided to gun shape stick to X, C type of gun. Do the proper study of gun and weld point.

Panel section is passing through the PLP either in opening condition or closing condition .Panel section through X, Y or Z direction passing through PLP. Section will help in finalizing the shape of clamp and rest locator. The panel touch to face of locator is machining and Harding face.

Finalization of a base plate plane – consider following things before deciding the base plate. Height of maximum and minimum weld spot from the floor. No gun arm should touch the base plate. Operator ergonomic while accessing all the spots.

Construction of Rest and Clamp Locator: If standard Mylar has to be used (Few companies make standard height and length of steel blank with few holes and dowels for clamping) then select the proper blank size as per the requirement; consider 5 mm above the panel.

Select the clamping cylinder as per the pivot point distance from the PLP. You may choose various cylinder 45 ∘, 60∘, 90 ∘, 30 degree opening as per the requirement (distance of clamp arm from the PLP and no of clamping mounted on each cylinder).

DESIGN TREE OF SWIVEL CLAMP UNIT

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 structure design tree.
So they will be giving a template on how the structuring and detailing of the design is done. And you have to follow that particular designing or structuring of the tree
In the design tree itself if we mentioned that particular name, wherever that part is we can easily know that this part belongs to this zone or This station or this assembly on particular unit. So this helps us to avoid errors during the design study,manufacturing assembly and inspections.
Structuring a design tree is actually to avoid all the errors, which might come during manufacturing assembly, or either in house inspections as well.
If the part, or assembly are not named properly, or design tree is not structured properly, it will create confusion to understand the design and may create major possibilities of making an error.
Every part, every component should be named according to their precedures.
If we did a mistake or renamed the entire standard parts from the customer as a design part.Now the customer is going to manufacture the entire part again from the scratch, but he already have that product in his itinerary.but extra cost,extra time and not feasible.this is also known as an error which is actually going to increase the cost of the entire assembly as well.
Naming a fixture or a unit or a part gives the information as to which project zone or assembly do they belong.
If we name the part properly or name the fixture properly it'll actually tell which unit or which assembly or which zone or in which station it actually belongs.
It can help us to identify the quantity of items of same types or different types that are being used in an assembly.

DIFFERENT TYPES OF PARTS IN SWIVEL CLAMP UNIT

1.CLAMP CYLINDER

Clamp cylinders are bought out parts. Some of the manufacturers are Tunkers, Zytran, Destaco, Festo, Steel smith.In the Clevis clamp Unit,we use Swivel Clamp Unit.

In this project i used CKG1_B_63_100Y Clamp Cylinder

CKG1 - Series of Cylinder

B- Clevis width =19.5

63 - Bore Size

100 - Cylinder Stroke in mm

Y - End bracket i.e Double Knukkle Joint

How the pneumatic cylinder works

Pneumatic Cylinder/Air Cylinders are mechanical devices which is used to produce a force in a reciprocating linear motion by the power of compressed gas.
Engineers prefere mostly pneumatic cylinders because these are quieter while loading and unloading,cleaner,Do not require large amount of space for fluid storage.
In the pneumatic cylinders the operating fluid is a gas,Because the operating fluid is a gas, leakage from a pneumatic cylinder will not drip out and contaminate the surroundings, making pneumatics more desirable where cleanliness is a requirement.
pneumatics are used to prevent fluid from dripping onto people below the puppets.

CYLINDER SELECTION

Pneumatic system-

System operated with Air.
Open loop system
Generally used for low pressure
Generally deliver es less force compared to hydraulic system
Cheaper compared to hydraulic for basic cost. But compressor running cost is more

Hydraulic system-

System operated with fluid- oil.
Closed loop system
High pressure system
Generally used for heavy force delivery
Initial cost is high
More expensive

2.FINGERS/MYLERS

In this one rest myler and one clamp myler or finger need to hold the car panel.

In this design i used two fingered mylers because of two fingered clamp it is to hold the car panel without any vibrations and the stability is high.

Mylars are also called as NC blocks
In German language,They calling mylar as COUNTER STEIN.
Mylars plays a major important role in BIW fixture design.
Mylars are Made of Steel or In plastic material.
Rest is an NC blcok,Which is fixed to the unit to support the car panel.
It resists the clamping forces of the Finger.

3.CLAMP ARM/LOCATOR

A clamp arm is taking part,It is made as per the position of the clamp cylinder,Stopper and shim,Clamp arm made from hard steel.

Locator is a movable part through the mechanism of cylinder which is used to hold the panel from top against the Back-up and they are usually mounted on the clamp arm.

4.PLATE

Any Shaped Plate used to mount the locator to clamp arm, besides allowing adjustment for locator in two directions shimming.

5.RAISER

The geometrical shape of riser block is according to flame cut and maintain the height of unit to the clamp point on panel.

The cylinder is mounted on machining face of riser through the screw.
The riser is a standard part,Which provide height to the pin unit,Clamp Unit as per requirements,The riser should have adequate strength so it can sustain under a load of car panel,clamping Cylinder,Blades.

6.SHIMS

A shim is a thin and often tapered or WEDGED piece of material, used to fill small gaps or spaces between objects.

Shims are typically used in order to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gaps between parts subject to wear
The function of shim is adjustable in any direction such as X, Y, Z direction through the locator on units.

7.BLADE

The Blade IS made part,Which is designed according to the position of the riser,Clamp Cylinder,Clamp arm,Rest mylar and stopper.

Clamp arm,Raiser,Blocker,Rest mylar all these parts are connected or mounted to the blade with the help of screws.

8.BUSHES

Unequal diameters, often with internal screw threads, used to connect blade and clamp arm of different sizes by bushes.

In this we used two bushes.

MATERIALS USED

Clamp arm
SAE 4140 or SAE 1045.

Shims/spacer
S.A.E. 1010 CRS FULL HARD, COLD ROLLED STRIP STEEL S.A.E. 1010 FULL HARD, S.A.E. 1020 HRS, etc.

Shim block
STEEL ASTM A-36, NM Stainless, STEEL ASTM A-36, SS type 303 or 304, etc.

Blade
STEEL ASTM A-36, etc.

Riser
STEEL ASTM A-36, etc.

REST UNIT DESIGN

A rest unit is used to support the car panel and also it resists the clamping force of the finger with the help of rest mylars.

Rest unit consist of rest mylars, shim packs, riser.
Holding force should be considered while designing a rest unit.
Mostly to avoid excess part to reduce the weight and also to reduce the cost of the fixture the rest unit is combined with the clamp unit.

DESIGN OF REST UNIT

1. First study process planning document, if it is already available. What is process document?

If you know the answer then go ahead. If not , please refer all the process documents.

•Study the PLP (Principle Location Points) data along with the nearby spot data and check the position of surrounding location and clamp units.

2. If you are using any specific CAD software as per the customer requirement e.g. CATIA, UG, FIDES understand the customer guidelines how to create the fixture, unit, weldment and base fabrication. Once you have understanding of CAD software methodology to be followed for design of single part, Unit assembly and base then start the design by adding the panel assembly in your fixture or unit assembly.

3. Take an overview of the working height if you’re having manual welding. For robotic welding also it’s important to see the working height in consideration of the robotic gun, turn table height if manual loading is done.

4. Put the proper gun at the spot location for all the spots near the rest unit. If process engineer has gun shape stick to X, C or Y type of gun. Do the proper gun study and place the gun as per the GEO or re-spot decision and operator approach. Once basic gun is placed considering the throat depth and throat gap start building the clamp and rest block at the PLP.

5. Panel section creation: Take a section at PLP either in clamp opening direction or normal direction .Sections should be normal to base. Panel section through X, Y or Z direction passing through PLP.Section will help in finalizing the shape of clamp and rest block. Most importantly used for finalization of gun shape.

6. Finalization of a base plate plane – consider following things before deciding the base plate.

Height of maximum and minimum weld spot from the floor. No gun arm should touch the base plate. Operator ergonomic while accessing all the spots.

7. Construction of Rest Block: If standard Mylar has to be used (Few companies make standard height and length of steel blank with few holes and dowels for clamping) then select the proper blank size as per the requirement; consider 5 mm above the panel.

9 As per your company or OEM, Tier 1 standard use the different standards mounting risers. Do not forgot to add the 10 mm shim (5mm solid +5mm shim pack, In few companies 3mm shims are used. Make connection plate between rise and Mylar.

10 If you are combining rough locator or part sensor bracket along with the rest unit. Take necessary care means distance of rough locator from panel. (I will write in detail about rough locator and sensor bracket in another topic)

11 Add all the hardware screws, dowels and washer as per the size.

12 Check all the position of surrounding units.

13 Do not forgot to check the screw and dowel removal during maintenance . Check with spanner open position.

DESIGN TREE OF REST UNIT

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 structure design tree.
So they will be giving a template on how the structuring and detailing of the design is done. And you have to follow that particular designing or structuring of the tree
In the design tree itself if we mentioned that particular name, wherever that part is we can easily know that this part belongs to this zone or This station or this assembly on particular unit. So this helps us to avoid errors during the design study,manufacturing assembly and inspections.
Structuring a design tree is actually to avoid all the errors, which might come during manufacturing assembly, or either in house inspections as well.
If the part, or assembly are not named properly, or design tree is not structured properly, it will create confusion to understand the design and may create major possibilities of making an error.
Every part, every component should be named according to their precedures.
If we did a mistake or renamed the entire standard parts from the customer as a design part.Now the customer is going to manufacture the entire part again from the scratch, but he already have that product in his itinerary.but extra cost,extra time and not feasible.this is also known as an error which is actually going to increase the cost of the entire assembly as well.
Naming a fixture or a unit or a part gives the information as to which project zone or assembly do they belong.
If we name the part properly or name the fixture properly it'll actually tell which unit or which assembly or which zone or in which station it actually belongs.
It can help us to identify the quantity of items of same types or different types that are being used in an assembly.

DIFFERENT TYPES OF PARTS IN POWER CLAMP UNIT

1.Blocks

2.RAISER

The geometrical shape of riser block is according to flame cut and maintain the height of unit to the clamp point on panel.

The cylinder is mounted on machining face of riser through the screw.
The riser is a standard part,Which provide height to the pin unit,Clamp Unit as per requirements,The riser should have adequate strength so it can sustain under a load of car panel,clamping Cylinder,Blades.

3.SHIMS

A shim is a thin and often tapered or WEDGED piece of material, used to fill small gaps or spaces between objects.

Shims are typically used in order to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gaps between parts subject to wear
The function of shim is adjustable in any direction such as X, Y, Z direction through the locator on units.

OVERALL IMAGES OF FIXTURE DESIGN

SIDE VIEW

TOP VIEW

ISOMETRIC VIEW

RENDERED IMAGE

Base Unit Design Challenges

Ship work like this
in your own course.

Talk to a career counsellor

Ship work like thisin your own course.

Talk to a career counsellor

Ship work like this
in your own course.