Week 8:- 3D Finishing Challenge 2

AIM:

• Perform 3D finish for all units of Assembly design.
• Create Rough locators for Assembly.

3D-FINISHING:

3d Finish is a process where the design is being completely 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 different units.
• Design the rough locators, which help to load a panel in correction orientation.
• Design the pneumatic lay-outing for pneumatic connection.
• Gun study is the 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 its 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 be 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.

1. Hole Concentricity and Hole Sizes:

• All part holes concentricity and hole sizes are checked for easy assembly while finishing the parts.

2. Machining Area:

• The machining area in every part should be defined and the machining area should be highlighted by using 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.

3 Nominality:

• All unit dimensions should be maintained nominal to facilitate easy assembly of the unit.

4. 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 color like:
• The dowel hole should be given blue color.
• The threaded hole should be colored yellow.
• Counterbore, open hole should be given cyan blue color.

5. 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.

6. Gaps Checking:

• The gaps between the different units are checked to ensure the proper individual working of different units.

7. Fasteners Implementation:

• Fast should be implemented in all the units as per the requirement and load on the part.

8.Avoiding Clash Between Different Parts:

• A proper gap should be maintained between units to avoid clashes between the different units.

9. Mylar Splitting as Per Panel Profile:

• Mylar splitting as for panel profile should be confirmed while finishing the design.

10. 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 each and every part easily with Unique Identification.

ROUGH LOCATORS:

• A rough locator is a part designed to guide the panel, 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 either by a person or a team or a 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 be also called fool proofing method. Because without a rough locator the part cannot be loaded incorrect 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.

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 of 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 the pin arresting direction.
• The rough locator should start guiding the panel before 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.
  
  

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 are assembled by means of 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 Side bracket assembly are located as shown in Table 1 with respect to 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 in 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 Gun. The Gun may differ depending upon 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 clearances with the Fixture. After adjusting the Fixtures, the coordinates of the welds be taken for further operations of 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.

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 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 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 their name.

BASE UNIT:

A base unit is a unit designed to mount all the other units of the tool, also other parts necessary for a tool like a pneumatic valve box, trunking cable path will also be mounted onto a base unit.

Below are some parts of a base unit in general.

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

Typical Parts of a base unit:

The typical Parts of a base unit are:

Base Unit:

• Base Plate is a machined plate of 25 to 40mm thickness made of steel and aluminum on to which the holes are drilled to mount the individual's units like clamp units. pin units etc of a tool.

There are three key benefits to a Baseplate:

• They can help to quickly and accurately tram in fixtures and vises.
• They can hold large, complicated, or odd-shaped parts.
• They protect the cast iron machine table.

Pedestal:

• A pedestal is a part that connects the base plate to the floor plate. A pedestal is a standard part in general, and in some cases, it can be a welded frame integrated with the base plate.
• A standard pedestal can be of different heights and different sizes.
• Depending on the size of the base plate, the number of pedestals varies for load distribution.
• A pedestal is of different types with different inclinations.

Trunking Channel:

• The Trunking channel is a standard part that will accommodate all the pneumatic and electrical hoses and wires for the units. The trunking channels include all the pressure inlet cables going to the pneumatic parts of the fixture and protects them from damage while the operation is in process.

Valve Box:

• Valve Box is a standard part that will contain all the valves for the pneumatic units. The valve box is the box that includes different solenoid valves. The pneumatic fixtures work on air pressure provided to it. So the arrangement of air pressure inlet and outlet is done within this valve box. The trunking channel includes all the pressure inlet cables going to the pneumatic parts of the fixture and protects them from damage while the operation is in process.

Eye Bolt:

• An eye bolt is a bolt with a loop at one end. They are used to firmly attach a securing eye to a structure, so that ropes or cables may then be tied to it.
• Machinery eye bolts are fully threaded and may have a collar, making them suitable for use with angular loads up to 450. Eyebolts without a shoulder should not be used for angular loads. Heavy forged eye bolts with a continuous eye may be forged with an integral shoulder, allowing their use for heavy off-axis loads.
• These are used for the transporting of the tool by inserting hooks into them. Some, hooks or forklift holes are also provided in some cases for transporting purposes.

Floor Plate:

• Floor plates are grouted to the floor with fixed bolts on the ground.
• These are also called foundation plates. There will be a clearance of 10mm maintained between the pedestal base plate and the floor plate.
• This clearance will be used by the leveling screws, for leveling the entire tool.
• Weld bars are to be used to weld the positions permanently after leveling is done.
• A weld bar is a plate along the sides of the base plate of the pedestal.

Fundamentals Of a Base Plate Design:

The fundamentals of a base plate design are:

1. As a designer, it is important to know how big 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.
2. A base plate size should cover all the units with its outer periphery including the opening.
3. A base plate is preferred to be designed with respect to BCS coordinates.
4. A base plate should be drilled with datum holes / measuring holes in line with a pitch of 1000 mm in general.
5. The number of datum holes depends on the size of the base plate.
6. 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.
7. Datum holes should be drilled with dia 100 mm away from other units.
8. Datum holes should be covered with cover plates.
9. Depending upon the weight, eye bolt size is selected for lifting holes on base plate Generally, 4 eye bolt provision is made You also 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) nearby.
10. 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 the plate.
11. Most of the OEM makes 4 dowel holes at 4 corners & put small aluminum plate marking X Y&Z coordinates of dowel holes. If the base length is too long few OEMs follow the methodology of having holes at a 500 mm distance.
12. The best unit of the fixture must be strong enough so that deflection of the fixture is as minimum as possible. This deflection of a fixture is called because of forces of welding, clamping of the workpiece.
13. The base unit of the fixture should have the mass to prevent vibration & chatter.
14. The base unit may be built from simple sections so that other units may be fastened with screw or Welded 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.
15. The base unit should be parallel to the floor to adjust this there should be the provision of the height adjusting mechanism.

Renaming of parts list in the base unit:

Colour Coding given to the holes on the base plate:

• Threaded hole and dowel holes making nominal and color-coding are done so easy to distinguish holes.
• Threaded hole (Yellow), clearance hole (Sky blue), Dowel Hole(Blue), Machining surface(orange).

Positioning of rough Locators on the Base Plate:

Holes made nominal to the Base Plate:

Checking Parameter	Action
Rename of the design tree	Done
Mark Machining Area	Done
Nominality	Done
Holes coloring standard	Done

REST UNIT:

Rest unit is a unit designed to support car panel using Mylar/ NC block/ rest component is rested only, no upper clamp or force applied there. It is the simplest unit to design because it has fewer parts to design & the purpose is only resting 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 the unit to locate as well as to rest the car panel. Also locating, clamping & Test unit can be combined together in one unit to reduce cost.

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

Marking of Machining area:

Colouring Standards:

Proper Renaming of Parts:

Checking Parameter	Action
Rename of the design tree	Done
Mark Machining Area	Done
Nominality	Done
Holes coloring standard	Done

CLAMP UNIT:

A clamp unit is a unit designed to clamp/hold the car panel with NC blocks/Mylars/rest by using a pneumatic cylinder. Clamp arm, finger, Rest/backup, L-block, shims, riser, pneumatic cylinders are the typical parts of clamp unit. Clamping force should be considered while designing a clamp unit. Usually clamp open position is 90o. Fingers are attached to clamp Mylar. In the Clamp unit shim to one side is more enough because it will restrict translation motion in an upward direction and downward direction only.

There is another type of clamp unit known as the swivel type. There is a pivot pin around which the clamp arm rotates.

Clamping Guidelines:

Locating the workpiece is the first basic function of a jig or fixture. Once located, the workpiece must also be held to prevent movement during the operational cycle. The process of holding the position of the workpiece in the jig or fixture is called clamping. The primary devices used for holding a workpiece are clamps. To perform properly, both the clamping devices and their location on the work holder must be carefully selected.

Factors in Selecting Clamps:

Clamps serve two primary functions.

1. They must hold the workpiece against its locators.
2. The clamps must prevent movement of the workpiece.

The procedure of Clamping the workpiece to the Panel:

• Place the workpiece, supply air at the clamp side without installing the clamping block, operate the clamp arm to the end of the clamp.
• Under the above conditions, adjust the shim so that the space between the workpiece and the clamping block is about 0.5 mm. Theoretically, there is no clamping force for holding a workpiece under this condition.
• In order to generate clamping force from the state described in step B, insert an additional shim. The thickness of the shim differs depending on the arm length and pressure, so please refer to the graph on front matter 3 as a guide. About 10% error may occur due to the difference intolerance of the clamp cylinder body.

Considerations to be taken while designing a rest unit or a clamp unit:

Considerations to be taken while designing a Rest Unit or a Clamp unit are:

1. Study of process planning document:

• Process document should contain the following information, which is necessary to design a clamp unit.
• No sheet metal panels to be welded. Total no of spots.
• Welding gun details if it is already recommended by process engineer study it in details like shape and its type.
• Study the PLP (Principle Location Points) data along with the nearby spot data.

2. CAD Software:

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

3. Height Selection:

• Take an overview of the working height if we have manual welding. For robotic welding also important to see the working height in consideration of the robotic gun, turntable height if manual loading is done.

4. Gun Placement:

• Put the proper gun at the spot location. Do the proper gun study and place the gun as per the GEO or re-spot decision and operator approach. Once the 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 the base. Panel section through X, Y, or Z direction passing through PL. The section will help in finalizing the shape of the clamp and rest block. Most importantly used for the finalization of gun shape.

6. Finalization of a base plate:

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 and Clamp Block:

• If standard Mylar has to be used then select the proper blank size as per the requirement consider 0.5 mm above the panel.

8.Clamp cylinder selection:

• Select the clamping cylinder as per the pivot point distance from the PLP. You may choose various cylinder 50 Dia, 63Dia, 80 Dia. as per the requirement.

9. Clamp and Rest block creation:

Create clamp or rest block as per the company guidelines.

• Many companies have size clamp blocks of 20x20 mm and no mounting screws and dowels. Many use 20x20 size rest or clamp block with one screw and 2 dowels or few uses with 2 screw and 2 dowels. 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. Start construction of mounting plate or fabrication structure as per the company standard to make the connection with the base plate.

10. Riser:

• As per OEM, Tier 1 standard uses the different standards mounting risers. Do not forget to add the 5 mm shim.

11.Rough Locator or position sensor mounted on clamp unit:

• If you are combining rough locator or part sensor bracket along with the clamp unit. Take necessary care means a distance of rough locator from the panel.

12. Hardware:

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

13.Clamp Open Position:

• Check all the clamp open, gun open positions and ensure that there is fouling with panels or any other surrounding units.

Fasteners Implementation:

Checking the Hole Concentricity:

Colouring Holes as per the Standards:

Indicating the Machining Area

Mylars Splitting as per the Panel Profile:

Checking the nominality of all the units:

Renaming of all the Parts of POwer Clamp Unit:

Checking Parameter	Action
Rename of the design tree	Done
Mark Machining Area	Marked
Mylars Splitting as per Panel profile	Done
Hole Concentricity	Done
Nominality	Done
Holes coloring standard	Done
Fasteners Implementation	Done

In the same manner, I have down for both Power Clamp, swivel clamp & pin clamp units

PIN UNIT:

A pin unit is a unit designed to locate the car panel using pins. There are two types of pin units. They are:

1. Fixed pin unit
2. Retractable pin unit

• Single Rod
• Dual Rod

The below are the different parts of a fixed pin unit.

1. Pin.
2. Pin retainer.
3. Shims/Spacers.
4. Blocks.
5. Blade/Adaptor plate.
6. Riser.
7. Cylinders.

Fundamentals of Pin Unit Design:

It is necessary to have 2 pins to locate a car panel & here one pin must arrest 4 ways (4 translational) & the other must arrest 2 ways i.e. 2 rotational) of a card panel.

The axis of the car panel hole & the axis of the pin should be the same. The pin tolerance for a geo pin will be of closer tolerance i.e. 0.15mm & for the re-spot pin is -0.28mm

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

FIXED PIN UNIT:

The below are the different parts of a fixed pin unit.

• Pin
• Pin retainer
• Shims/Spacers
• Blocks
• Blade/Adaptor plate
• Riser

Indicating the Machined area:

Colouring Holes as per the standards:

Fasteners Implementation:

Checking the hole concentricity:

Checking the nominality of the Parts:

Renaming of all the parts of the pin unit:

Checking Parameter	Action
Rename of the design tree	Done
Mark Machining Area	Marked
Mylars Splitting as per Panel profile	Done
Hole Concentricity	Done
Nominality	Done
Holes coloring standard	Done
Fasteners Implementation	Done

In the same manner, I have down for all other pin units.

IMAGES OF ALL THE UNITS USED IN THE ASSEMBLY AFTER 3D FINISHING:

CONCLUSION:

Hence, 3D finishing is performed on the designed Assembly of Fixtures and Rough Locators were designed for the given panel