Week 8:- 3D Finishing Challenge 2
Week 8:- 3D Finishing Challenge 2
AIM:
Perform 3D finish for all units of Assembly design.
Create Roug
3D-FINISHING:
3d Finish is a process where the design is finished and to be ready for final simulation and 2d detailing.
While finishing the design the nominality is checked which ensures the easy assembly of all the units.
The hole concentricity and hole sizes are checked which ensures the assembly of different parts.
The gaps between the different units are checked to ensure the proper individual working of other units.
Design the rough locators, which help to load a panel in correction orientation.
Design the pneumatic lay outing for pneumatic connection.
The gun study is a major and most important part of 3d finishing.
Selection of sensors, Solenoid valves as per the requirement and implementation in design.
Fasteners are implemented as per the hole size and the standard color codes as per the customer requirement are applied to differentiate the type of hole whether it's a dowel hole, Threaded hole, or clearance hole.
Renaming of the assembly and the part is done to give every part a different identity so everyone can identify in which assembly this part is going to fit.
After doing all these things the model is sent for simulation and 2d detailing.
Points Need to Be Taken Care of While Finishing the Design:
The following are the points taken into consideration while finishing the design.
Hole Concentricity and Hole Sizes:
All part holes' concentricity and hole sizes are checked for easy assembly while finishing the parts.
Machining Area:
The machining area in every part should be defined and the machining area should be highlighted by using a standard color code. Machining is to be done on parts to properly Mount with mating parts. Machining only on desired faces reduces cost and saves time. And also Machining increases the accuracy of dimension. So before going to simulation or detailing machining area should be defined.
Nominality:
All unit dimensions should be maintained nominal to facilitate easy assembly of the unit.
Holes Colouring Standard:
In a 3D finish hole coloring should be done because it helps to identify what type of hole it is. It depends on customer standards. Customer-specific colors like:
The Dowel hole should be given blue color.
The threaded hole should be colored yellow.
Counterbore, the open hole should be given cyan blue color.
Pneumatic Lay outing:
The pneumatic lay outing is a collection of different pneumatic pipes which work as an inlet to the pneumatic cylinder. It should be done properly for the proper functioning of the units.
Gaps Checking:
The gaps between the different units are checked to ensure the proper individual working of other units.
Fasteners Implementation:
Fast should be implemented in all the units as per the requirement and load on the part.
Avoiding Clash Between Different Parts:
The proper gap should be maintained between units to avoid clashes between the different units.
Mylar Splitting as Per Panel Profile:
Mylar splitting for the panel profile should be confirmed while finishing the design.
Proper Renaming of Parts or Assemblies as Per the Standards:
Proper renaming of parts and assembly should be done while finishing the design and hence we can identify every part easily with Unique Identification.
ROUGH LOCATORS:
A rough locator is a part designed to guide the panel and to locate the car panel onto the pins accordingly. A rough locator can be of standard part or a make part.
Rough locators also work as Poka-yoke. Poka-yoke is a Japanese concept used for mistake-proofing.
Rough locators are also used to help to locate the workpieces in the automation process. Locating refers to the desired location where you want the workpiece to be when it is getting worked on by a person, team, or robot.
The accuracy of the locating components directly affects the consistency and how the final product will come out. This is why these components are essential to our setup.
It can also be called a foolproofing method. Because without a rough locator, the part cannot be loaded in the correct position.
The rough locators are set accordingly to the angle of the respective panel and hence the part can be loaded in a defined direction and orientation only.
FIG: rough locator
Points Needed to Consider While Designing A Rough Locator:
The following are the points needed to be considered while designing the rough locator.
A rough locator should be placed at the edges of the car panel, which it has to guide.
Applicator has to be placed at the same angle as the car part edge with a minimum distance of 2-5 mm from the edge of the car part.
Prof locator should guide the panel in pin arresting direction.
The rough locator should start guiding the panel 10 to 15mm to the start of the pin engagement.
The applicator should be designed with an entry angle for the car panel. Generally, it ranges between 30-45 degrees.
A rough locator should be designed with two slots to mount the easy adjustment.
The slot should be in the direction of the car part guiding.
FIG: slot was given to the rough locator to adjust the position
Positioning of rough Locators on the Base Plate:
GUN STUDY:
Welding is predominantly used in automobile industries and requirements for fixtures that ease the welding process is a continuous development task in any industry. Car Body-In-White (BIW) is a complicated steel structure including 300~500 sheets with complex shapes and is assembled using welding in a high rhythm through 55~75 robotic work-stations. The foremost step taken before starting the design of the welding fixture is to arrive at the spot weld locations. The location and orientation of other critical units of the fixture including clamps, locators, etc., are decided based on the weld spot distribution. The weld spots for the Front door inner panel and Side bracket assembly are located as shown in Table 1 concerning the body line of the car. It includes the study of the weld gun (A portable device for semiautomatic welding of parts of various articles) which is going to be used for the operation depending on the size of the part, Thickness of the part, etc. It includes the study of the weld matrix & the weld point positions. There are two types of weld point one is geo weld points which ensures the geometry of the assembly & second is the Re spot weld points which adds strength to the already welded part.
The device used to make spot welding on the panel is called a Gun. The Gun may differ depending on the application. Fixtures will be designed by considering the weld spots on the panel. After designing the Fixture, the CAD file of the gun is placed on the weld spots to check whether the Gun is clear with the Fixture. After adjusting the Fixtures, the coordinates of the welds be taken for further operations of the Weld Gun.
Points needed to consider during the gun study:
Weld gun study is a very time-consuming process, the entire welding cycle time study depends on the no. of spots & weld gun study.
The following are the points that need to consider during the gun study.
The axis of the weld spot along the welding direction must be normal to the weld surface.
The no. of weld spots for the panel, the time required to spot each weld & the total time required to complete all weld spots.
If we have one or more device models & we want to program, the behavior of each model in the work cell can be simulated over time. Instructions for each device are coded by giving sequences. The sequence defines the motion, manipulation & action of the devices. Based on the distance of each tag point from the home position, motion type, speed & acceleration one can obtain cycle time for each device assigned with sequences. This way robot cycle time is precisely calculated.
After sequencing all the devices, a simulation is run with “collision check” ON & made sure that the welding operation is collision-free.
FIXTURE ASSEMBLY:
Renaming and structuring of the design tree:
Renaming of the design tree is done. and structuring the design tree in a way that is simple to identify the units. some units use multiple times those are easy to identify by its name.
BASE UNIT:
INTRODUCTION & THEORY -
A base unit is a unit on which all other units of the tool and other necessary parts of the tools like trunking channel, valve box, eyebolt, etc are assembled.
Holes will be drilled on the base plate to mount all the necessary units of the tool on it.
A base unit is important in fixture assembly as it mounts all the units on it, so the base unit should be designed such that it can take up the load and absorb all the vibrations during the welding operation.
Parts of base unit -
- a) Base plate -
A base plate is a machined plate with a thickness of 20 - 40 mm thickness.
A base plate has holes drilled into it so that all the units can be mounted on it.
- b) Pedestal -
The pedestal is a part that connects the base plate to the floor plate.
It is a standard part in general and in some cases, it can be welded frame integrated with a base plate.
A standard pedestal can be of different heights and sizes.
Depending on the size of the base plate, the number of pedestals varies for load distribution.
- c) Trunking channel -
It is a duct that accommodates all the electrical and pneumatic hoses and wires for the unit of the tool.
The trunking channel is available in different thicknesses and different sizes.
- d) Valve box -
It is a standard part that contains all the valves for the units.
It supplies air to the pneumatic cylinders in the assembly.
The valve box consists of a solenoid valve which is used for air supply.
- e) Eye bolt -
Eyebolt is a part that is attached to the base unit, it is used for transportation purposes of tools.
Lifting hooks will be used to lift the base unit or the entire tool.
Forklift holes will also be provided in case for transportation purposes.
- f) Floor plate -
The floor plate also known as the foundation plate is grounded to the floor with fixed bolts on the ground.
A clearance of 10mm is provided between the pedestal and the floor plate.
weld bars are used to weld position permanently after leveling is done.
Points that are needed to be taken into consideration while designing base unit -
- a) Working height - the working height of the base unit is an important consideration. the working height depends upon the type of welding operation like manual welding or robotic welding. for manual welding, the overall height of the total tool should be 850-1100 mm in general. the working height also varies from country to country.
- b) The dimension and the specification of the base plate are also important to factor .below are the fundamentals given for the base plate.
Fundamentals Of a Base Plate Design:
The fundamentals of a base plate design are:
As a designer, it is important to know how big a base plate or bigger base welded structure will be handled during the fabrication & handling process. Special care needs to take care of flatness if the base size is very long.
A base plate size should cover all the units with its outer periphery including the opening.
A base plate is preferred to be designed concerning BCS coordinates.
A base plate should be drilled with datum holes / measuring holes in line with a pitch of 1000 mm in general.
The number of datum holes depends on the size of the base plate.
Datum holes should be drilled at nominal values of coordinates & in terms of 50 x 100. (In general) ex. X=100, Y 600, Z-250.
Datum holes should be drilled with dia 100 mm away from other units.
Datum holes should be covered with cover plates.
Depending upon the weight, eye bolt size is selected for lifting holes on the base plate Generally, 4 eye bolt provision is made You also need to select the location of the eye bolt considering the rope/ belts used while shifting the structure or complete fixture are not damaging any units (rest, clamp or location units) nearby.
Depending upon the component size & weight of the total units you can decide whether you need a fabricated base or just a plate. Mostly fabricated bases are used made of square or rectangular tubes with a plate.
Most of the OEMs make 4 dowel holes at 4 corners & put a small aluminum plate marking the X Y&Z coordinates of the dowel holes. If the base length is too long few OEMs' s follow the methodology of having holes at a 500 mm distance.
The best unit of the fixture must be strong enough so that the deflection of the fixture is as minimum as possible. This deflection of a fixture is called because of forces of welding, and clamping of the workpiece.
The base unit of the fixture should have the mass to prevent vibration & chatter.
The base unit may be built from simple sections so that other units may be fastened with screws or Welded as necessary. Those parts of the fixture that remain permanently with the fixture may be welded. Those parts that need frequent changing may be held with screws.
The base unit should be parallel to the floor to adjust this there should be provision for the height adjusting mechanism.
Renaming of parts list in the base unit:
Color Coding gave to the holes on the base plate:
Threaded holes and dowel holes make nominal and color-coding are done so easy to distinguish holes.
Threaded hole (Yellow), clearance hole (Sky blue), Dowel Hole(Blue), Machining surface(orange).
REST UNIT:
The rest unit is a unit designed to support the car panel using Mylar/ NC block/ rest component is rested only, no upper clamp or force applied there. It is the simplest unit to design because it has fewer parts to design & the purpose is only resting of the car panel.
Because of the simplicity, the rest unit is combined with another unit to reduce the cost of the overall project.
It can be combined with a clamp unit to clamp as well as to rest the car panel. It can be combined with locating unit to locate as well as to rest the car panel. Also locating, clamping & Test units can be combined into one unit to reduce cost.
There is no cylinder attached to it. It has a rest Mylar, blade, and riser & below is different parts of the rest unit. The rest unit is also divided into simple support units, multiple support units & retractable support units.
NC block/Mylar:
NC blocks or popularly also known as Mylar is the ones that hold the panel.
It prevents the panel from deforming while welding.
They always come in pairs.
Top Mylar is known as clamping Mylar and bottom Mylar is known as resting Mylar.
Few points to remember about Mylar:
Generally, Mylar clamping block clamp cross section (the area in the contact panel) is considered as 20mmx20mm.
Most of the OEMs/Tier 1 prefer Mylar to have a 5mm allowance material for machining. Most Mylar is CNC machined if it is clamping 3D profile.
Depending on the angle of the cross-section, Mylar will be having shimming either in one direction or in 2 directions. The general Thumb rule is if the section is inclined more than 15 deg or the clamping surface is a 3D profile then 2-direction shimming is provided. The reason is simple mathematics. The equation of inclined line/ plane will be having 2 parameters to control and we control with shimming in 2 directions. Less than 15 deg does not mean that there are not 2 parameters. These are there but they are neglected if the angle is less than 15 deg.
Shim:
Shims are washers or thin strips of material used to align parts, make them fit, or reduce wear.
Shims are designed to fit in between blocks and fixtures to provide support or reach a dimension required in the assembly.
Typically designed in a U shape matter so that they can fit between mounting screws. This shape helps to make them easy to install and remove or replace.
Designers will use shims individually or as packs of 5, 6, or 7 pieces. Thicknesses range from 0.25mm to 2mm.
Many assemblies require tolerance to be hit about a length or height; shims allow designers to hit these tolerances. They can be stacked between NAAMS NC blocks, L blocks, or pin retainers.
Riser:
The riser is a structure generally used to mount the toggle clamp and rest, clamp Mylar and location pin, and give height to the assembly.
It is not necessary to have one riser where all the parts of the clamp or rest or location units are mounted.
Risers can either be a standard part or take part.
Blade:
The blade is a plate that is attached to the riser and other components like a cylinder, arm, etc are mounted on it.
It can either be a standard part or a made part
Marking of Machining area:
Coloring Standards:
Fasteners Implementation:
Checking the nominality of the UNIT:
Proper Renaming of Parts:
FIG: REST UNIT
FIG: REST UNIT WITH BASE UNIT AND COMPONENT
PIN UNIT:
Fundamentals of pin unit design:
It is necessary to locate a car panel with two pins. one pin to restrict 4-way motion (4 translational ) and one pin to restrict 2-way motion (2 rotational ).
The pin should engage 3-5 mm from the car panel entry surface.
All pins should be accommodated with 2-way adjustable shims irrespective of the direction of arresting.
The round pin should be used in arresting 4-way in the car panel if the hole is round.
The round pin should be used in arresting 2 way in the car panel if the hole is slot.
The diamond pin should be used in arresting 4-way in the car panel if the hole is a slot.
The diamond pin should be used in arresting 2 way the in-car panel if the hole is round.
The axis of the car panel hole and the axis of the pin should be the same (in general ).
The pin tolerance for the geo pin will be -0.15 mm and for respot pin will be -0.28 mm
MATERIALS USED:
In general, the materials used for pins, pin retainers, shims, shim blocks, blades & risers are:
Pin: C45, EN31, SAE 8620 Steel,
Pin retainer: Steel / ASTM A-36, SS type 303 or 304,
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,
Blade: STEEL ASTM A-36,
Riser: STEEL ASTM A-36.
SURFACE FINISH:
In general, the hardness of the materials for pins, pin retainers, shims, shim blocks, blades & risers are:
Pin: Chrome plating, Zinc coating, and Pins with TiN codes shall have 1 to 2 microns of nitride added to
Pin retainer: BLACK OXIDE FINISH, No black oxide finish for "SS TYPE" components (SURFACES TO BE FLAT, PARALLEL &
PERPENDICULAR TO O WITHIN 0.015 T.I.R).
Shims/spacer: BLACK OXIDE FINISH (SURFACES TO BE FLAT AND PARALLEL TO WITHIN 0.015 mm T.I.R).
Riser: SURFACES TO BE FLAT, PARALLEL & PERPENDICULAR TO WITHIN 0.015 T.I.R.
PIN TOLERANCE:
The pin tolerance for a geo pin will be of closer tolerance i.e. -0.15mm & for respot, the pin is -0.28mm.
PURPOSE OF PIN UNIT:
As by the 3-2-1 locating principle, the introduction of two pins helps to arrest the 6 degrees of freedom (4 axial & 2 radial movements) whereas the other 6 degrees of freedom are arrested by introducing a minimum of three supports.
Typically, the locating pins are used to locate a body part in a position sufficiently accurate to execute a welding process.
The body part is constrained by a set of appropriately locating pins so total constraint by locating pins should be fully constrained at all times to prevent any movement.
There are two types of pin units -
1)Fixed pin unit -
A fixed pin unit is a unit designed to locate the car panel using pins.
2)Retractable pin unit -
A retractable pin unit is designed to locate the car panel using pins, but the entire pin package is mounted in the retractable cylinder. the cylinder will move the unit up and down.
FORMULA & CALCULATION:
Formula to calculate the length of the screw,
Length of the screw = [1.5 X (std. hole size)] + {distance between the surface of the part to the first surface of the other part
Length calculation for the length of the screw.
To fix the pin retainer & the shim block using standard screws we need to find the length of the screw using the above-mentioned formula.
The highlighted surfaces shown in the figure are the {distance between the surface of the part to the first surface of the other part}
Since the given tap holes are M8 & the distance is 25mm as shown in the figure then,
Length of the screw = [1.5 X (std. hole size)] + {distance between the surface of the part to the first surface of the other part} Length of the screw = [1.5 X 8] + 25 = 37 = 40mm Allen cap screw
Then the standard size of the screw should be 40mm for connecting the pin retainer & the shim blocks for this example.
1 . Pin
It locates the car panel. it can either be a make part or a standard part.
A pin should have a grinding surface on the shaft with fits onto which the pin retainer is fixed.
The mounting surface of the pin should be finely machined.
It should have a step machine surface to lock rotation which matches with pin retainer.
The mounting surface of the pin retainer to the block should be machined.
All machined planes should be perpendicular to the axis of the shaft.
The pin must have fastening provisions like a tapped hole from the bottom or a V groove from the side.
A pin must be hardened ( heat treatment ) (55 to 60 HRC) and black oxide finished in general.
Material - Hardened materials like C45, 16MNCR5, 20MNCR5, EN31, etc.
Surface finish - black oxide, Zinc coating, Chrome plating.
Typically, locating pins are used for controlled, fine tolerance positioning of, For example, a pallet that is moved along one axis, where the drive mechanism is not accurate and stable enough to place it in a position sufficiently accurate to execute a particular process, the use of locating pins may be the best solution.
The Diamond Shape is a critical feature that helps with machining inaccuracies and smoother locating When two round headpins are installed onto one plate, the distance between two mounting holes must be extremely precise and even then, the workpiece will not be placed on the base as easily as it would with the use of a diamond shape pin.
There are several styles of Pin Head They serve different purposes and can be utilized in a variety of applications.
2 . Pin retainer
It is a part that holds the pin in position, it can either be a make or a standard part.
It should have a hole with a fit onto which the pin is fixed.
The pin mounting surface should be finely machined.
It should have a step to lock the rotation of the pin.
The mounting surface of the pin retainer to the block should be machined.
The pin retainer will be fixed to block or an L block to the riser with 2 dowel holes (pins) and at least one screw hole to maintain tolerance.
3 . Blocks/ L blocks
These parts are used to accommodate the shimming direction as per fundamental in general, also in some cases used for other design feasibility
4 . Shims/ spacer
It is a standard part in general, which is used for adjustment of the locator ( NC block and Pin retainer ) for obtaining the desired value for the precise working of unit wrt car part.
- Blade
A blade is a part like a plate, which connects the parts on a unit to an In general, the blade can be either a make part or a standard part.
- Riser
It is a part on which all the parts of a unit are mounted & is mounted on the base plate of a tool.
- Dowel holes & machined surface-
All make parts that are to be assembled should be designed with 2 dowel holes & at least 1 to 6 threaded/ free holes (depending on size) 7 to be finely machined for the mounting surface with 3 to 5 mm step machining.
Marking of Machining area:
Coloring Standards:
Fasteners Implementation:
Checking the nominality of the UNIT:
PIN UNIT:
Proper Renaming of Parts:
FIG: PIN UNIT WITH BASE UNIT AND COMPONENT
POWER CLAMP UNIT
3-2-1 principle: Our ultimate intention for using a pin unit is to fix the workpiece so that it does not deviate from the position while the operation is being performed on it. For this reason, we use the 3-2-1 principle.
Every component we know has 6 degrees of freedom. They are listed below:
Translational motion along the x-axis.
Translational motion along the y-axis.
Translational motion along the z-axis.
Rotational motion along the x-axis.
Rotational motion along the y-axis.
Rotational motion along the y-axis.
FIG. DEGREE OF FREEDOM
Degrees of freedom can be simply understood as the direction in which any component can move. These 6 degrees become 12 if we consider translation along negative and rotation in an anti-clockwise direction too. That means every component can move in all directions when it is free. But processes like welding, stamping, or others and every other cannot be carried out on such a free-to-move body for obvious reasons. Thus the body must be constrained in all the major directions for the workman to work upon it. This constraint on motion is achieved by the 3-2-1 principle.
In the 3-2-1 principle, we make use of locating pins in the given order to fix it on a fixture:
3 pins are located on the bottom side of the component. These pins constrain the translational motion of the body in the z-direction and rotational motion along the x-axis and y-axis. Thus 3 degrees are restricted. But the body still can rotate along the z-axis and translate into the x-axis and y-axis.
2 pins are located on the back side of the component. These pins constrain the translational motion along the x-axis and rotational motion along the z-axis. Thus we have constrained 5 degrees in total. But translation along the y-axis is still possible.
1 pin located on the adjacent side of the 2 pins we can constrain the last degree that is translation along the y-axis.
FIG. LOCATING PINS
Thus we can constrain all the degrees of freedom of a body using the 3-2-1 principle which used 6 pins for the same.
When we use clamps we restrict the following motions:
Translational motion along the z-axis.
Rotational motion along the x-axis.
Rotational motion along the y-axis.
sign two Rest units and three Power Clamp units with different Risers, blades, and Clamp arms.
CLAMPING: The car panel will rest on the rest unit, Also it resists the clamping force of the finger & thus clamp the car panel.
RESTING: The car panel will rest on the rest unit, Also it resists the clamping force of the finger & thus clamp the car panel.
FORCES ACT IN CLAMP & REST UNIT:
To design a clamp unit we have considered some forces which acts in a clamp unit for clamping purpose. The forces that act in clamp units are,
Clamping force.
Holding force.
Clamping force is not the same as holding force.
CLAMPING FORCE:
Clamping force signifies the force applied to the workpiece by the drive mechanism via the clamp arm during gripping or clamping operations.
Clamping force (Fs) = 48 x S3 = Force in newton
HOLDING FORCE:
Holding force, on the other hand, denotes the maximum force, after locking the knee-lever (over-center position), that can be applied by the workpiece on the gripper/clamp arm without destroying the mechanism. Therefore, particular attention must be paid to the maximum holding force when, for example during the production process (welding, bonding), there is a possibility of distortion of the component or if the clamp arm is used as a fixed stop.
If the holding force specified in the technical details is exceeded, this will inevitably destroy the mechanism, the clamp arm, or the bearing position.
CLAMP UNIT:
Clamps are versatile tools that serve to temporarily hold work securely in place.
A Clamp unit is a unit designed to clamp/ hold the car panel at a certain location.
Its purpose is to hold the panel at that place with the application of force.
TYPES OF CLAMP UNITS:
Power Clamp unit.
Swivel cylinder clamp unit.
CLAMP PLAN:
The customer provides the clamp plan which consists of the position of the clamp, pins, rests and dump, etc.
It has the exact coordination of these components and in addition, it also has the hole’s dimensions and tolerances.
As this is critical input data, it must not be modified.
In case the spot for weld and the clamp position is nearby and it may create a problem later and there is a need to change the position of the clamp, the same must be done so with the permission of the customer as it will be easy for the customer to make changes from his side also.
NC block/Mylar:
NC blocks or popularly also known as Mylar is the ones that hold the panel.
It prevents the panel from deforming while welding.
They always come in pairs.
Top Mylar is known as clamping Mylar and bottom Mylar is known as resting Mylar.
Few points to remember about Mylar:
Generally, Mylar clamping block clamp cross section (the area in the contact panel) is considered as 20mmx20mm.
Most of the OEMs/Tier 1 prefer Mylar to have a 5mm allowance material for machining. Most Mylar is CNC machined if it is clamping 3D profile.
Depending on the angle of the cross-section, Mylar will be having shimming either in one direction or in 2 directions. The general Thumb rule is if the section is inclined more than 15 deg or the clamping surface is a 3D profile then 2-direction shimming is provided. The reason is simple mathematics. The equation of inclined line/ plane will be having 2 parameters to control and we control with shimming in 2 directions. Less than 15 deg does not mean that there are not 2 parameters. These are there but they are neglected if the angle is less than 15 deg.
Shim:
Shims are washers or thin strips of material used to align parts, make them fit, or reduce wear.
Shims are designed to fit in between blocks and fixtures to provide support or reach a dimension required in the assembly.
Typically designed in a U shape matter so that they can fit between mounting screws. This shape helps to make them easy to install and remove or replace.
Designers will use shims individually or as packs of 5, 6, or 7 pieces. Thicknesses range from 0.25mm to 2mm.
Many assemblies require tolerance to be hit about a length or height; shims allow designers to hit these tolerances. They can be stacked between NAAMS NC blocks, L blocks, or pin retainers.
Riser:
The riser is a structure generally used to mount the toggle clamp and rest, clamp Mylar and location pin, and give height to the assembly.
It is not necessary to have one riser where all the parts of the clamp or rest or location units are mounted.
Risers can either be a standard part or take part.
Blade:
The blade is a plate that is attached to the riser and other components like a cylinder, arm, etc are mounted on it.
It can either be a standard part or a made part
Standard parts/Bought out parts:
Fasteners
Clamp Cylinder
Clamp arm
Fasteners: For this project, ISO 4762 Hexagonal socket head cap screws were used with varying diameters and lengths. Mostly M8 screws with varying lengths are used but to fasten the riser to the base plate M10 or M12 are used. The length varies concerning the thickness of the part that is to be fastened. This length is calculated by the formula:
Length of the screw= 1.5d+ distance between the start of surfaces to be fastened
For example in the below image, we are to fasten the riser to the L-block. The distance between their surfaces is 25mm and we are using an M8 screw.
So the length of the screw will be= 25+1.5*8 i.e. 37mm. But the standard available size is 40mm so we used that. And similar process was followed everywhere.
Clamp cylinder: A clamp is a pneumatic device that works with pressurized air. It is used to open and close the parts fixed to the clamp arm fixed to the clamp body.
They are in general of 40, 50, 63, and 80 bore capacity.
Horizontal clamp mounting opens up to 135deg.
Vertical clamp mounting opens up to 105deg.
V 50.1, 63.1, 80.1 BR3 Vario Clamp: Vario clamp with toggle joint mechanism and continuously adjustable opening angle, Over-centre-lock, Enclosed aluminum housing, Oval-shaped cylinder in the sizes 50, 63, 80, Forked clamping arm, the standard hole pattern for adapting contour blocks, Continuously adjustable opening angle 5°-135°, optional: Weld immune inductive sensing of closed and an opened position (T12).
VU_63_BR2_A05_T12_135_GRAD_TUENKER: Vario clamp, Naams version, for clamping of medium and large body panels with stepless adjustable opening angle, integrated toggle lever mechanism, self-holding type. Enclosed aluminum housing, flat oval cylinder in sizes 50, 63, and 80. Fork-shaped clamp arm with standard hole pattern for receiving contour pieces. Opening angle variable from 5 ° -135 °. Options: - Inductive sensing, weld immune for the open and closed position (T12) - Hand-applied version.
Clamp arm: The clamp arm is a bought-out part, to which all the movable parts are fixed. In general, a clamp arm is a part of a clamp cylinder.
Clamp arms are different for the different bores of the cylinder
Clamp arms are available in different hole pitch
Clamp arms are available as:
Middle arm
FIG. STANDARD CLAMP ARM (MIDDLE)
Right arm
FIG. STANDARD CLAMP ARM (RIGHT)
Left arm
Fasteners Implementation:
Checking the Hole Concentricity:
Coloring Holes as per the Standards:
Yellow - Threaded Holes
Blue - Dowel Holes
Indicating the Machining Area:
Mylars Splitting as per the Panel Profile:
Checking the nominality of the unit:
Renaming of all the Parts of the POwer Clamp Unit:
FIG: CLAMP UNIT WITH BASE AND COMPONENT
SWIVEL CLAMP UNIT:
Swivel Clamps :
The primary components of the clevis clamp include the clamp arm, blade, cylinder, angle riser, locator block, and finger. Swivel clamps shall typically be designed with the center of the clamp cylinder, the center of the locator, and the center of the clamp arm on a common line. However, it is acceptable to offset the clamp point from the clamp cylinder to allow for improved access for welding and part load and unloading.
The clamp arm shall be welded construction including a 20.0mm thick arm with an integral pivot to accommodate a 19.50mm wide Swivel. The female portion of the clevis shall always be part of the arm. The male portion of the Swivel shall always be part of the blade.
Clamp Cylinder:
Cylinder designation: In this unit, we used a Clevis cylinder for clamping designated as CKG_1B_63_100YNomenclature of the cylinder is as below:
CKG1: Series of cylinder
B: Clevis width is 19.5 mm.
63: Bore size
100: Stroke of cylinder
Y: End bracket i.e. double knuckle joint (M6 without tap)
FIG: Clevis cylinder
Clamp arm: It is the part to which the clamp mylar is mounted & also clamp cylinder is attached to the end of the arm with the use of a clevis pin. It has two plates of 8 mm thickness welded & helps in rotating of clamp arm about pivoting point of the blade.
The below figure shows the 100 mm stroke achieved & clamp arm end in line with the cylinder rod. See Y & Z values.
NC block/Mylar:
NC blocks or popularly also known as Mylar is the ones that hold the panel.
It prevents the panel from deforming while welding.
They always come in pairs.
Top Mylar is known as clamping Mylar and bottom Mylar is known as resting Mylar.
Few points to remember about Mylar:
Generally, Mylar clamping block clamp cross section (the area in the contact panel) is considered as 20mmx20mm.
Most of the OEMs/Tier 1 prefer Mylar to have a 5mm allowance material for machining. Most Mylar is CNC machined if it is clamping 3D profile.
Depending on the angle of the cross-section, Mylar will be having shimming either in one direction or in 2 directions. The general Thumb rule is if the section is inclined more than 15 deg or the clamping surface is a 3D profile then 2-direction shimming is provided. The reason is simple mathematics. The equation of inclined line/ plane will be having 2 parameters to control and we control with shimming in 2 directions. Less than 15 deg does not mean that there are not 2 parameters. These are there but they are neglected if the angle is less than 15 deg.
FIG: CLAMP &REST MYLAR
FIG: CLAMP &REST MYLAR
1mm is the component thickness. so the distance between the clamp and the rest of the mylar is 1mm.
Stopper:
The function of the stopper is to restrict the motion of the clamp arm. It avoids clamping the arm to rotate beyond the limit. It has two parts male & female.
Blade: The blade is the part to which all other units are attached e.g. mylar, stopper, clamp cylinder, riser. The blade is designed according to the position of all other parts.
FIG: BLADE
Bush: Bush is a friction-type bearing. It is lubricated with grease, and oil. It permits relative motion between two mating parts. It is made of hard material also its ID & OD are precisely machined or ground. It presses fitted & after worn out it is replaced with new one instead of replacing another part which saves cost. Mostly phosphor bronze or gunmetal material is used for making bush. In this unit, three bushes are used of the same internal (12 mm) & external diameter (18 mm) but different lengths.
Pin
It locates the car panel. it can either be a make part or a standard part.
A pin should have a grinding surface on the shaft with fits onto which the pin retainer is fixed.
The mounting surface of the pin should be finely machined.
It should have a step machine surface to lock rotation which matches with pin retainer.
The mounting surface of the pin retainer to the block should be machined.
All machined planes should be perpendicular to the axis of the shaft.
The pin must have fastening provisions like a tapped hole from the bottom or a V groove from the side.
A pin must be hardened ( heat treatment ) (55 to 60 HRC) and black oxide finished in general.
Material - Hardened materials like C45, 16MNCR5, 20MNCR5, EN31, etc.
Surface finish - black oxide, Zinc coating, Chrome plating.
Typically, locating pins are used for controlled, fine tolerance positioning of, For example, a pallet that is moved along one axis, where the drive mechanism is not accurate and stable enough to place it in a position sufficiently accurate to execute a particular process, the use of locating pins may be the best solution.
The Diamond Shape is a critical feature that helps with machining inaccuracies and smoother locating When two round headpins are installed onto one plate, the distance between two mounting holes must be extremely precise and even then, the workpiece will not be placed on the base as easily as it would with the use of a diamond shape pin.
There are several styles of Pin Head They serve different purposes and can be utilized in a variety of applications.
Shim:
Shims are washers or thin strips of material used to align parts, make them fit, or reduce wear.
Shims are designed to fit in between blocks and fixtures to provide support or reach a dimension required in the assembly.
Typically designed in a U shape matter so that they can fit between mounting screws. This shape helps to make them easy to install and remove or replace.
Designers will use shims individually or as packs of 5, 6, or 7 pieces. Thicknesses range from 0.25mm to 2mm.
Many assemblies require tolerance to be hit about a length or height; shims allow designers to hit these tolerances. They can be stacked between NAAMS NC blocks, L blocks, or pin retainers.
FIG: SHIMS
Riser:
The riser is a structure generally used to mount the toggle clamp and rest, clamp Mylar and location pin, and give height to the assembly.
It is not necessary to have one riser where all the parts of the clamp or rest or location units are mounted.
Risers can either be a standard part or take part.
Hardware: These are standard parts. Parts are assembled with the help of a washer and bolt. for better assembly should use two dowels and four bolts for the riser and blade. Where for bolting one part should have a tapping hole and on the other part a simple hole (1 to 2 mm larger than bolt size.)
The length of the bolt is decided by the width of part + (1.5*D)
For ex. where
L=Length of Bolt
D=diameter of the bolt to be used
Let’s, take M8 Bolt
L= 25 + (1.5 * 8)
L=25+12
L=37 mm.
Dowel pins: These are standard parts. There are various types of dowel pins like split, parallel, taper, clevis, and spring, grooved. Dowel pins are used to locate parts precisely & to restrict movements. For mylar, dia. 6 or 8 dowel pins should be used. For the blade, shimming block dia.8 dowel pin should be used & for the riser base dia. 10 or 12 pins are used.
Washer: Standard steel grade A plain normal series washer used.
FIG: S001_Z01_ST010_01_00_CLAMP_UNIT
Holes Colouring as per the Standards:
Yellow - Threaded hole
Blue - Dowel hole
Indicating the Machined area:
Checking the nominality of the UNIT:
Mylars Splitting as per the Panel profile:
Checking the Nominality of all the Parts:
Renaming of all the Parts:
PANEL:
REST UNIT:
Base Unit
Power Clamp Units:
Pin Units:
Swivel Clamp Units:
Pin Clamp Units:
Positioning of the units on the Base Plate:
FINAL IMAGE OF THE FIXTURE:
CONCLUSION:
Hence, 3D finishing is performed on the designed Assembly of Fixtures, and Rough Locators were designed for the given panel.