Week 8:- 3D Finishing - Challenges 1

1. What do you understand by the 3D finish process?

Answer:

3D finish:

• It is the process where the design is being completely finished and further moved to the simulation and 2D detailing.
• To ease the assembly of all the units, nominality of the designed parts are checked. The hole concentricity and the hole sizes are also checked which ensures the assembly of the various parts.
• The gaps between the different units are also checked to ensure the proper working of individual units. The rough locators are to be designed for guiding the proper orientation of the panel onto the fixture.
• Gun study is the major and the most important part of the 3D finishing. Design the pneumatic lay-out for pneumatic connection.
• Selection of sensors and solenoid valves as per the requirement and implementation in design.
• Fasteners are implemented as per the hole size and standard colour codes are applied as per the customer requirement to differentiate the type of the hole whether it is dowel hole or threaded hole or clearance hole.
• Renaming of the assembly and part is done to differentiate each part from the others so that everyone can identify in which assembly the part is going to be fit.
• After all these are done the model is sent for simulation and 2D detailing.

2. What are the points need to be taken care of while finishing the design?

Answer:

The points are need to be taken care while finishing the design are:

1. Hole concentricity and Hole sizes:

To provide ease of assembly all part hole concentricities and hole sizes are checked.

2. Machining area:

The machining area in every part should be defined and it should be highlighted by using a standard colour code. Machining is to be done on parts to properly mount with mating parts. Machinig 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:

It is done in 3D finishing to help identify the type of hole. It depends on customer standards of specific colour like,

• The dowel hole is given blue colour
• The threaded hole is given yellow colour
• Counterbore, open hole are given cyan blue colour

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.

3. What are Rough locators & what are their uses?

Answer:

Rough locators:

Fig shows: Rough locators(NAAMS)

• A rough locator is a part designed to guide the panel positioning, 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.
• They are also used to help 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 in 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 shows: Rough locators

4. What are the points you need to consider while designing a rough locator?

Answer:

The following are the points needed to be taken into consideration while designing the rough locator:

• A rough locator should be placed at the edges of the car panel, which it has to guide.
• A locator has to be placed at the same angle of the car panel edge with a minimum distance of 2-5 mm from the edge of the car.
• Rough locator should guide the panel in pin arresting.
• The rough locator should start guiding the panel before 10 to 15 mm 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 the 2 slots to mount the locator and easy adjustment.
• The slot should be in the direction of the car part guiding.

5. What is the Gun study process?

Answer:

Gun study process:

• 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 come up with the spot weld locations.
• The location and orientation of the 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 with respect to the body line of the car.
• It includes information on weld gun detail, weld matrix & weld points.

Weld matrix and weld points:

• Weld points are basically where the welding is going to happen at which point and at what coordinate it is welded.

Geo weld points & Re-spot weld points:

• Welding is predominantly used in automobile industries requirements for fixtures that ease the welding process is a continuous development task in any industry.
• A typical BIW has more than 500 weld spots on it.
• The data of weld matrix and weld point is given in the form of spheres.i.e.red and green spheres. where the welding is going to happen.
• Geo spots are red in colour and re-spots are green in colour.
• All the red spheres are going to done in geo stationary
• In the re-spot station where the green welding is going to be happen. So this happens when one component is going to be attached with this particular component and in other station, the other component get attached.
• The front door inner panel and side bracket of the Gm sedan car are to be spot welded as shown in the below figure.

Fig shows: Weld points of 2 assemblies

• Weld spots for each weld assembly are highlighted in figures as WP1, WP2, WP3 and so on.
• The weld points form the base for fixture design, the clamping plan & locating plan are done on the weld spot distribution.
• The weld spots for the front door inner panel - side bracket asssembly are located as shown in the table with respect to the body line of the car.

For assembly-I For assembly-II

• It includes the study of weld gun ( A portable device for semi-automatic welding of parts of various articles) which is going to be used for the operation depending on the size of the part, the thickness of the part,etc.,

Fig shows : Weld guns

Fig shows: weld gun study

• In weld gun study the gun which is going to be used while spot welding is checked over the panel by using the 3D software.
• The fixture is designed for the car panel to hide it in the position, the weld gun position is checked over the predefined spot weld points, whether the gun falls into the fixture unit or not.
• If the weld gun intersects with the fixture unit then redesigning of that unit or the repositioning of that unit is done & again confirmed whether the gun is falling or not.
• Fixtures are redesigned if the gun falls to the fixture unit, the weld spot positions remain the same.
• The weld spots are defined on the prescribed locations as shown in the figure. The axis of the weld spot along the welding direction must be normal to the weld surface. To ensure this, the weld spot coordinates are created using the "SURFACE" option under tags in the layout menu.
• In the IGRIP layout, the motion destination position of a device model is represented by a tag in a Cartesian coordinate frame with N, O & A (or X, Y & Z) axes.

6. What are the points need to consider during the gun study?

Answer:

The points need to be considered 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 behaviour 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. Base 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 the "collision check" ON & made sure that the welding operation is collision-free.

Fig shows: Collision between the weld gun and the part

7. What is pneumatic routing?

Answer:

Pneumatic routing:

• Pneumatic systems should be efficient & leak-free. Sometimes, they are not because of improper tube line routing due to the result of either lack of knowledge, or corners cut on planning time, or both.
• If routing is not done properly, all kinds of things such as from not being able to access fitting for efficient maintenance all the way to leak connections, inefficient or poor tube routing can create an unintended issue that needs to be addressed. An ounce of planning is worth a pound of troubleshooting.
• Planning tube line routing is a time investment but can have a big ROI, especially for complex systems. During system design, routing should be developed as the next step after sizing the tube lines & selecting the appropriate fittings.

Some guidelines for planning appropriate tube line routing:

• Leave fitting joints as accessible as possible. Inaccessible joints are difficult and time-consuming to assemble, tighten and service.
• Use software tools to make labor-intensive calculations such as pressure drop.
• Employ U-bends to allow for line contraction and expansion.
• Include offsetting bends to allow for motion under load, regardless of how 'rigid' the system seems.
• Favor bends rather than straight tube lines, because a straight- line tube assembly with no bends can cause joint strain which may lead to leaking.
• Make sure routing design allows room for assembly of any connections required.
• Minimize pressure drop by getting around obstructions with as few 90 degree bends as possible. One 90 degree bend has more pressure loss than two 45 degree bends.
• Route lines around rather than over the areas that require regular access or maintenance.
• Design routing with clamping in mind. Appropriate design leads logically to proper clamping.
• Keep troubleshooting and maintenance in mind. Focus on logical design and avoid crossed lines.
• Design the tube line routing to reduce the likelihood of users standing or climbing on plumbing.

8. What is the solenoid valve?

Answer:

Solenoid valve:

• Solenoid valve differ in the characteristics of teh electric current they use, the strength of the magnetic field they generate, the mechanism they use to regulate the fluid, and the type and characteristics of fluid they control.
• The mechanism varies from linear action, plunger-type actuators to pivoted-armature actuators and rocker actuators. The valve can use a two- port design to regulate a flow or use a 3 ore more port design to switch flows between ports. Multiple solenoid valves can be placed together on a manifold.
• Solenoid valves are the most frequently used control elements in fluids. Their tasks are to shut off, release, dose, distribute or mix fluids. They are found in many application areas. Solenoids offer fast and safe switching, high reliability, long service life, good medium compatibility of the materials used, low control power and compact design.
• Functions of a solenoid valve:

1. Solenoid valve function involves either opening or closing an orifice in a valve body, which either allows or prevents flow through the valve. A plunger opens or closes the orifice by raising or lowering within a sleeve tube by energizing the coil.
2. Solenoid valves consist of a coil, plunger and sleeve assembly. In normal closed valves, a plunger return spring holds the plunger against teh orifice and prevents flow. Once the solenoid coil is energized, the resultant magnetic field raises the plunger, enabling flow. When the solenoid coil is energized in a normally open valve, the plunger seals off the orifice, which in turn prevents flow..

Parts of the solenoid valve:

1) Valve body: This is the body of the valve to which the solenoid valve is connected. The valve is usually connected in the process flow pipeline to control the flow of certain fluid like liquid or air. Ordinarily the flow from the valve is controlled by the handle, but in case of the automatic valve the solenoid valve is connected to the valve.

2) Inlet port of the valve: This is the port through which the fluid enters inside the automatic valve and from here it can enter into the final process.

3) Outlet port: The fluid that is allowed to pass through the automatic valve leaves the valve through the outlet port. The solenoid valve controls the flow of the fluid from inlet port to the outlet port. The outlet port is eventually connected to the process where the fluid is required.

4) Coil/ Solenoid: This is body of the solenoid coil. The body of the solenoid coil is cylindrical in shape, and it is hollow from inside. The body is covered with steel covering and it has metallic finish. Inside the solenoid valve there is solenoid coil.

5) Coil windings: The solenoid consists of several turns of the enameled wire wound around the ferromagnetic material like steel or iron. The coil forms the shape of the hollow cylinder. Externally this coil is covered with the steel covering and inside the hollow part there is a plunger or the piston, whose motion inside the hollow space is controlled by the spring.

6) Lead wires: These are external connections of the solenoid valve that are connected to the electrical supply. The current is supplied to the solenoid valve from these wires. When the solenoid valve is energized, the current flows through these wires to the solenoid valve and when the solenoid valve is de-energized the flow of current stops.

7) Plunger or piston: This is the solid round metallic part cylindrical in shape and placed in the hollow portion the solenoid valve. When the electrical current is passed through the solenoid valve, the magnetic field is generated inside the hollow space. Due to this the plunger tends to move vertically in the hollow space. When the electrical current is stopped to the solenoid valve, the magnetic field is stopped and the plunger is remains the existing place due to the force of the spring.

8) Spring: The plunger moves inside the hollow space due to the action of the magnetic field against the action of the spring. The magnetic field generated inside the solenoid valve tends to move the plunger, but the spring tends to stop the motion of the plunger in which ever the position it is. This action of the spring against the magnetic field helps keeping the plunger in the position where the flow of current to the solenoid valve is stopped. The spring performs very crucial action inside the hollow space. For one, the plunger is in the vertical position, so the spring helps keeping it at the desired position instead of allowing the plunger to fall to the bottom due to gravity when the current to the solenoid valve is stopped. Secondly, the spring also prevents the movement of the plunger due to force of the fluid flowing through the valve body. If the spring was not there the plunger would have moved up when the fluid is present and moved down when the fluid is not there. Thus the spring actually forces the plunger to carry out the control of the fluid. It allows the movement of the plunger only to the extent when the electric current is flowing through the solenoid valve.

9) Orifice: The orifice is an important part of the valve though which the fluid is flowing. It is the connection between the inlet and the outlet port. The flow of fluid from the inlet port to the outlet port takes place from this port. In the ordinary valves, this port is covered with the valve disc at the bottom of the stem of the valve to which the handle is connected. Thus in ordinary valves, the opening of the orifice are controlled by the handle, but in case of the solenoid valves, the opening of the orifice is controlled by the plunger. The movement of the plunger is in turn controlled by the spring and the current flowing through the solenoid valve.

Working of the solenoid valve:

Fig shows: Cross section - detailed view of solenoid valve

Fig shows: Demonstrate the working of solenoid valve

• Initially the sensor senses the process towards the outlet side of the solenoid valve. When it senses that certain quantity of the flow of the fluid is required, it allows the current to pass through the solenoid valve.
• Due to this the valve gets energized and the magnetic field is generated which triggers the movement of the plunger against the action of the spring. Due to this the plunger moves in upwards direction, which allows the opening of the orifice. At this instant the flow of the fluid is allowed from the inlet port to the outlet port.
• If the current passing through the solenoid valve is constant, the position of the plunger and hence opening of the orifice remains constant. If the sensor senses that more flow of the fluid is required, it allows the increase in current passing through the solenoid valve, which creates more magnetic field and more upwards motion of the plunger.
• This leads to further opening of the orifice and more flow of the fluid from the inlet port to the outlet. If the required flow of fluid is less, the sensor allows passage of the lesser current to the solenoid valve.
• When the sensor senses that the fluid is no more required in the process, it stops the flow of the current to the solenoid valve completely. Due to this the solenoid valve gets de-energized and the plunger reaches the bottom most position and closes the orifice completely thus stopping the flow of fluid from the inlet port to the outlet port.
• In this way the solenoid coil operates the valve as if it is being operated by the human being.
• When the flow of certain quantity of fluid is required it opens the valve to required extent and when the flow is not required it shuts the valve entirely

9. What is the valve bank?

Answer:

Valve bank:

Fig shows: valve bank

• Valve bank is the arrangement of no.of solenoid valves.
• Valve bank will have a common inlet port, a single servo line to each of the pneumatic valves, and independent vent passages for each solenoid.
• On the solenoid bank, each of the solenoid valves separately controls the feed of high pressure servo air to a single pneumatic valve.
• The valve is actuated by selectively energizing the corresponding solenoid to allow servo air to the servo port of the valve. To return the valve to its fail-safe position, the solenoid is de-energized to vent the servo port of the valve to ambient.
• The solenoid bank is designed with an inlet port, a single servo line to each of the pneumatic valves, and independent vent passages for each solenoid.
• The solenoids are two-stage pilot valves and are normally open with the solenoid de-energized, allowing high pressure supply air to the servo ports of the downstream pneumatic valves. Energizing the solenoid blocks high pressure air supply and simultaneously vents the pneumatic valve servo chamber to atmosphere, closing the respective pneumatic valve.
• The two-stage solenoid is designed to provide fast response times. The electrical configuration is a dual-coil redundant design providing an isolated circuit topology housed in a single package. Each coil is independent and identical in function.

Fig shows: Solenoid valve bank

Common features of valve bank:

• These are designed for high vibration levels.
• It uses aluminium alloy manifolds for lightweight.
• These are designed for high-temperature environments.
• Design architecture allows easy selection of 2 to 6 solenoid valves.

10. What is a sensor & brief about its application in automation?

Answer:

Sensor:

Fig shows: Different types of sensors

• A sensor is a device that detects and responds to some type of input from the physical environment. The specific input could be light, heat, motion, moisture, pressure, or any one of a great number of other environmental phenomena. The output is generally a signal that is converted to human-readable display at the sensor location or transmitted electronically over a network for reading or further processing.
• In a mercury-based glass thermometer, the input is temperature.
• Most sensors are electronic(the data is converted into electronic data), but some are more simple such as glass thermometer, which presents visual data.
• Peope use sensors to measure temperature, gauge distance, detect smoke, regulate pressure and other uses.
• A unit is designed to sense car panel using electrical sensor is called sensor unit. The signal from the sensor is send to the PLC so the next process is executed by this signal.
• The sensor is very sensitive & easily damagable part so sensor cover is provided to the sensor for safety purpose.

Application of sensors in automation:

Fig shows: Assembly sensor

1. In the industrial automation, sensors play a vital part to make the products intellectual and exceptionally automatic. These permit one to detect, analyze, measure and process a variety of transformations like alteration in position, length, height, exterior and dislocation that occurs in the Industrial manufacture sites.
2. The various types of sensors used in the automation industry are proximity sensors, vision sensors, ultrasonic sensors, position sensors, photoelectric sensors, temperature sensors, inclination sensors,etc.,
3. These sensors also play a pivotal role in predicting and preventing numerous potential proceedings, thus, catering to the requirements of many sensing applications.

4. These MEMS industrial automation sensors convert measured mechanical signals into electrical signals.Micro-electro-mechanical system (MEMS) motion sensors use data processing algorithms designed on a motion interaction platform which integrates numerous low-cost MEMS motion sensors with ZigBee wireless technology to carry personified interactions while working together with machines. Sensor signal processing systems mainly solve noise cancellation; signal smoothing, gravity influence partition, coordinate system alteration, and position information recovery .Widely used in the automotive Industry in ABS technology.

5. Acceleration and Motion MEMS are few important sensors used in industrial automation.

6. Sensors for detecting proximity, pressure, temperature, level, flow, current and voltage; and limit switches. With discrete or analog outputs, these sensors are critical to automating any machine or process.

11. What are the types of sensor?

Answer:

• Sensors are divided into active and passive sensors.
• Active sensors are those which require an external excitation signal or a power signal.
• Passive sensors on the other hand, do not require any external power signal and directly generate output response. The other type of classification is based on the means of detection used in the sensor. Some of the means of detection are Electric, Biological, Radioactive and Chemical.
• A Position sensor is any type of device which detects the movement of a chosen object in either a Linear or Rotary motion and converts the movement into output signals which are suitable for processing, transmission or control depending on the application.
• Position sensors are available in both contacting & non contacting technologies including; Potentiometric, Magneto-Restrictive, Hall Effect, Encoder and LVDT/RVDT in various sensor packages. Different types of technology ensure the most accurate measurements in different applications.
• The next classification is based on the conversion phenomenon i.e., the input and the output. Some of the common conversion phenomena are Photoelectric, thermoelectric, Electrochemical, Electromagnetic, Thermo optic, etc.,
• The final classification of the sensors is Analog and Digital Sensors.
• Analog sensors produce an analog output i.e., a continuous output signal with respect to the quantity being measured.
• Digital sensors, in contrast to Analog sensors, work with discrete or digital data. The data in digital sensors, which are used for conversion and transmission, is digital in nature.

There are different types of sensors like:

1. Proximity sensor
2. Temperature sensor
3. Accelerometer sensor
4. Pressure sensor
5. Light sensor
6. Ultrasonic sensor
7. Smoke, Gas and Alcohol sensor
8. Touch sensor
9. Tilt sensor
10. Flow and Level sensor
11. Colour sensor
12. Humidity sensor
13. Laser sensor
14. Photo electric sensor
15. Infrared sensor

Fig shows: Different types of sensors

12. What are the fundamental points that need to consider while designing or selecting the sensor?

Answer:

The following are the fundamental points that need to be considered while designing the sensor unit:

• The signal from sensors will be fed to PLC and so the next process will be executed the signal.
• It should help to avoid human error.
• BAsically sensors should be equal numbers as compared to the numbers of panels in an assembly. for e.g. If 8 panels are in an assembly then there must be atleast 8 sensors used.
• Sensor should be slot designed in such a way that they can be adjusted in 3 direction.
• Sensors should provide safety to the operator.

The accurate choice of selecting a sensor depends on the knowledge about the application type, the variable of product and the condition in the operating environment.

1. Measuring range:

While selecting a sensor (temperature sensor, proximity sensor, accelerometer sensor, etc), the range of measuring should directly correspond with the physical measuring range so that we can obtain the most precise reading and optimal sensor lifespan.

2. Environment:

We must be aware of environmental conditions while installing a product. Numerous sensors can be affected by the environmental conditions (such as temperature variation, gas, humidity, chemicals, etc.)

3.Flexibility:

While selecting a sensor, we need to check if it can provide flexibility, like features that can adapt to changing the products

4. Digital lower cost:

It is always better to use a sensor which gave gives a digital output. It is better to avoid using the analog field devices, even though they minimize the cost because while converting from analog to digital that can produce errors. A digital output equivalent sensors are more worth.

The above image in which there are two types of the accelerometer. One is analog and the other one is digital. For industrial application, it is better to use digital accelerometer instead of an analog accelerometer

5. Intelligent sensor:

It is better to adopt intelligent sensors that can be scaled, calibrated or configured remotely.

Smart sensors are those which take up data from the environment and use the predefined function to perform some actions.

6. Accuracy and Precision:

Precision and Accuracy does not mean the same thing, though they are often related. Accuracy is the quality or state of being correct or while the precision ability of the devices to notice small changes (As an example, a temperature sensor that measures the normal body as 35.999°C has high precision but low accuracy.) The Accuracy and precision and one of a given product should be appropriate. Too high precision can give a wrong indication that the value is too accurate. Similarly, a sensor with good accuracy will be expensive. The error can affect both precision and accuracy.

The above example explains us about accuracy and precision.

7. Signal conditioning:

Electrical noise is present everywhere, mainly on the production floor which can produce huge errors in reading. So, protection circuits and Signal conditioners can provide some protection.

In mobile manufacturing industry ESD safety is a must because electronic products are very sensitive to electrostatic charges so we use a wrist strap, grounded floor mat, heel strap, air ionizer, etc.

8. Sudden temperature changes:

The sensor must be in such a situation that it can overcome the sudden temperature changes and work properly without producing errors.