Additive Manufacturing Processes

There are many techniques for layer by layer addition of materials such as Fused Filament Fabrication (FFF), Stereo Lithography (SL), and Laser Sintering (LS) etc. which will be explained below but common to all of them, the first step is to design the model using CAD tools. The CAD model is then converted to suitable machine understandable format like STL, VRML, AMF or G Code. The converted file is then input to the 3D printer. The software installed in the 3D printer reads the file and slices the model into different layers. The thickness of the layer can be adjusted. As the thickness decreases the quality increases but processing time also increases. The head of the 3D printer moves according to the cross section of the model and depending upon the process, one layer gets made. This process repeats so that the entire 3D model is manufactured. The support structures if any can be removed by using different techniques such as immersing in a special liquid after the production stage. The different steps are shown in the Fig.1.2.

Fig.1.2 3D Printing Steps (Medfab, 2018)

Stereolithography:

Stereolithography (SL) is the first commercialized 3D printing process. SL is a laser-based process that works with photopolymer resins. As illustrated in Fig.1.3, when the laser hit on the resin, it cures to form a solid in a very precise way. The photopolymer resin is held in a vat with a movable platform inside. A laser beam is directed in the X-Y axes across the surface of the resin according to the 3D data supplied to the machine (the .stl file). The resin hardens precisely where the laser hits the surface. Once the layer is completed, the platform within the vat drops down by a fraction (in the Z axis) and the subsequent layer is traced out by the laser. This continues until the entire object is completed and the platform can be raised out of the vat for removal (Think3d.in, 2018).

Fig.1.3 Stereolithography Process (Reddy and Upputuri, 2018a)

Because of the nature of the SL process, it requires support structures for some parts, specifically those with overhangs or undercuts. These structures need to be manually removed. In terms of other post processing steps, many objects 3D printed using SL need to be cleaned and cured. Curing involves subjecting the part to intense light in an oven-like machine to fully harden the resin. It is one of the most accurate 3D printing processes with excellent surface finish. However limiting factors include the post-processing steps required and the stability of the materials over time which can become more brittle (Ngo et al., 2018).

Laser Sintering:

Laser sintering is also a laser based 3D printing process but works with powdered materials. As shown in Fig.1.4, according to the 3D data fed to the machine, the laser is traced across a powder bed of tightly compacted powdered material. As the laser interacts with the surface of the powdered material, it sinters or fuses the particles to each other forming a solid. As each layer is completed, the powder bed drops incrementally and a roller smoothens the powder over the surface of the bed prior to the next pass of the laser for the subsequent layer to be formed and fused with the previous layer (Srinivas and Babu, 2017).

Fig.1.4 Laser Sintering Process (Reddy and Upputuri, 2018b)

The build chamber is completely sealed as it is necessary to maintain a precise temperature during the process specific to the melting point of the powdered material of choice. Once finished, the entire powder bed is removed from the machine and the excess powder can be removed to leave the printed parts.

One of the key advantages of this process is that the powder bed serves as an in-process support structure for overhangs and undercuts therefore complex shapes that could not be manufactured in any other way are possible with this process. However on the downside, because of the high temperatures required for laser sintering, cooling times can be considerable (Think3d.in, 2018).

Free Form Fabrication:

3D printing utilizing the extrusion of thermoplastic material is the most common and recognizable 3DP process. Fused Filament Fabrication (FFF) is one of such process. It works by melting plastic filament that is deposited via a heated extruder a layer at a time, onto a build platform according to the 3D data supplied to the printer. Each layer hardens as it is deposited and bonds to the previous layer (See Fig.1.5).

Fig.1.5 Fused Filament Fabrication Process (Atta, 2018)

The most common materials used by are ABS and PLA (Think3d.in, 2018). The FFF processes require support structures for any applications with overhanging geometries. It is one of the limitations of the FFF 3D printers. However as the systems have evolved and improved to incorporate dual extrusion heads, it has become less of an issue. In terms of models produced, the FFF process produces much less accurate models but things are constantly improving. The process can be slow for some part geometries and layer-to-layer adhesion can be a problem, resulting in parts that are not watertight. Again, post-processing using Acetone can resolve these issues (En.wikipedia.org, 2018a).

References:

Atta, E. (2018). Comparison Between Fused Deposition Modelling (FDM) and Selective Laser Sintering (SLS). [online] Green-mechanic.com. Available at: https://www.green-mechanic.com/2016/12/comparison-between-fused-deposition.html [Accessed 13 Jan. 2018].

En.wikipedia.org. (2018a). Fused filament fabrication. [online] Available at: https://en.wikipedia.org/wiki/Fused_filament_fabrication [Accessed 10 Jan. 2018].

Medfab. (2018). Post-Processing - medfab. [online] Available at: http://medfab.de/post-processing/ [Accessed 12 Jan. 2018].

Ngo, T., Kashani, A., Imbalzano, G., Nguyen, K. and Hui, D. (2018). Additive manufacturing (3D printing): A review of materials, methods, applications and challenges. Composites Part B: Engineering, 143, 172-196.

Reddy, P. and Upputuri, R. (2018a). Stereolithography (SLA) Technology Overview | think3D. [online] Think3D. Available at: https://www.think3d.in/stereolithography-sla-technology-overview/ [Accessed 13 Jan. 2018].

Reddy, P. and Upputuri, R. (2018b). Direct Metal Laser Sintering (DMLS) Overview | think3D. [online] Think3D. Available at: https://www.think3d.in/direct-metal-laser-sintering-dmls-technology-overview/ [Accessed 12 Jan. 2018].

Srinivas, M. and Babu, B. (2017). A Critical Review on Recent Research Methodologies in Additive Manufacturing. Materials Today: Proceedings, 4(8), 9049-9059.

Think3d.in. (2018). [online] Available at: https://www.think3d.in/landing-pages/beginners-guide-to-3d-printing.pdf [Accessed 7 Jan. 2018].

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Advantages of Additive Manufacturing

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Introduction to Additive Manufacturing

Introduction to Additive Manufacturing

Additive Manufacturing (AM) refers to a process by which digital 3D design data is used to build up a component in layers by depositing material. The term ‘3D printing’ is increasingly used as a synonym for Additive manufacturing (Srinivas and Babu, 2017). However the latter is more accurate in that it describes a professional production technique which is clearly distinguished from conventional methods of material removal. In conventional machining such as turning and milling, the material is getting removed from a solid block (Eos.info, 2018). In other words, the material is subtracted from the work piece so these processes are termed as subtractive manufacturing. Additive manufacturing is just the opposite of subtractive manufacturing (See Fig.1.1). It builds up components layer by layer using materials which are available in powder, liquid or filament forms.

Fig.1.1 Conventional Manufacturing V/S Additive Manufacturing (Bct-technology.com, 2018)

The material may be plastic, metal, concrete or one day human tissue. In the past few years, many companies have embraced AM technologies and are beginning to enjoy real business benefits from the investment. The technology is maturing and has worked its way into a number of markets. It is one of the hottest and most interesting advancements in the design and marketing world today.

References:

Bct-technology.com. (2018). NX 11.0.2 Additive Manufacturing - BCT Technology AG. [online] Available at: https://www.bct-technology.com/en/support/tips-tricks/nx-1102-additive-manufacturing.html [Accessed 12 Jan. 2018].

Eos.info. (2018). EOS Industrial 3D printing - Process, method and benefits. [online] Available at: https://www.eos.info/additive_manufacturing/for_technology_interested [Accessed 12 Jan. 2018].

Srinivas, M. and Babu, B. (2017). A Critical Review on Recent Research Methodologies in Additive Manufacturing. Materials Today: Proceedings, 4(8), 9049-9059.

Next:

Additive Manufacturing Processes

Anatomy of Arduino UNO board

Arduino which is an open source electronics platform has easy to use hardware systems and software packages. Arduino UNO board is one of them. It is the most widely used Arduino board across the globe. It is the favorite one for beginners, hobbyists and students. The major parts of a typical Arduino UNO board is shown below. Since it is an open source platform, there will be some negligible differences in the board when compared to your own board. The major parts are numbered from 1 to 17.

Image source https://www.tutorialspoint.com/arduino/images/board_description.jpg

1. POWER USB:-

After writing the program code in the Arduino IDE, it is needed to transfer into the micro controller. For this purpose a connection between the board and computer is needed. This power usb port (1) is used for that purpose. There will be a USB cable provided which is having a box type end and it is needed to connect to this (1) port. When upload button in the IDE is clicked, the program will be transferred to the board. This port can also be used for giving power. Once the board is connected to the computer, it is sufficient to get power for Arduino board. A power bank can also be connected to the board by using this (1) port.

2. BARREL JACK:-

Barrel jack is mainly used to give power. By using this (2) port, it is possible to use batteries as power source. It is also possible to power directly from AC power source. Students, beginners and hobbyists often use this port to connect with batteries. In case of a wheeled robot, most of the cases the arduino board and the motors are powered separately. This port helps for increasing the compactness of the system.

3. VOLTAGE REGULATOR:-

The voltage across the Arduino board will be different. The input voltage will be different to the voltage needed by processor. The voltage needed by the processor may be different to the voltage needed by other components. To avoid these problems, a stabilizer is needed. Voltage regulator (3) will control the voltage given to the board and also stabilize the voltage needed by other components.

4. CRYSTAL OSCILLATOR:-

Just like computers, Arduino board also want to calculate time. It needs to synchronize the various operations. It needs to perform certain functions at given interval. Without adjusting and calculating time, it is nearly impossible for Arduino to function well. Even simple things will not be possible. Calculating time is the function of crystal oscillator. There will be a number printed on the crystal oscillator. Most probably it will be 16.000. It implies that the frequency is 16000000 Hertz or 16 MHz.

5 & 17. RESET:-

Sometimes, it will be necessary to reset the board. There are two parts in the Arduino program. One is 'setup' and other is 'loop'. Once the program is uploaded to the board, the board reads the code from top to bottom. It reads the 'setup' function only one time while the 'loop' function will be executed again and again. Once it is reset, then the program will start to execute from 'setup' function again. This is what happens when the board is reset. There are two ways to reset the Arduino board. One way is to use an external reset button by using the port (5) or to use the builtin reset button (17).

6. It is a 3.3 v output supply

7. It is a 5 v output supply

8. GND: It means ground pin

9. Vin: This pin can also be used to power externally.

(Most of the components that will be used with Arduino work under 3.3 v or 5.0 v. That is why two ports are dedicated to give as output supply 3.3 v and 5 v. There are totally 3 ground pins denoted as GND. It can be used to give low stage in programming {zero voltage}.)

10. ANALOG PINS:-

There are two signals viz. analog and digital. Analog signals are continuous. There are six analog pins in Arduino UNO, they are denoted as A0, A1, A2, A3, A4 and A5. Mos often these pins are used to connect analog sensors such as temperature sensor, humidity sensor etc. Once the analog signal is received it is converted to digital signal consisting zeros and ones so that the processor can process on it.

11. MICRO CONTROLLER:-

This is the main part of the Arduino board. It (11) is known as the brain of the Arduino board. It is this part which takes actions as instructed through program. Each board has its own micro controller. Generally the micro controllers are made by ATMEL company. The information about the micro controller is shown on top of it (11). It receives some input, performs some task and gives some output.

12. ICSP PIN:-

ICSP stands for In Circuit Serial Pragramming. It is very uncommon to program ICs before they are soldered onto PCB. Instead, most micro controllers have an in-system programming referred to as ISP header. Some IC manufactures such as ATMEL have a special ISP method for programming their ICs which is referred to as ICSP (In-Circuit Serial Programming).

13. POWER LED INDICATOR:-

This is a way to check the Arduino board. Once the board gets power, this LED should light up. If this (13) light doesn't turn on, then it means there is something wrong in the connection. If the connection is okay, then the problem will be of board. The color of the LED depends upon the board. It may be green, yellow, orange etc.

14. RX & TX LEDs:-

There are some serial data communication while the board is performing its tasks. At every transmission of such data, TX LED will blink. Similarly, for receiving data, RX LED will blink. This is most often visible when the program is uploaded to the Arduino board. There are also two ports provided namely RX and TX which can also act as digital i/o ports 0 and 1.

15. DIGITAL PORTS:-

These are digital multi purpose ports. They can be utilized as input as well as outputs. If it is defined as input in the program, it will act as input or if it is defined as output in the program, it will act as output. More often, the digital sensors are connected to these ports and define them as input and when the motors are connected, those ports will be defined as output ports. Some ports may be labelled as '~', it indicates that these ports can be used to generate PWM (Pulse With Modulation).

16. AREF:-

AREF stands for the Analog Reference. It can be used to set the upper limit for the analog pins and serves as an external reference voltage to them.

Arduino code for obstacle avoiding robot using ultrasonic sensor

//connect trig pin of ultrasonic sensor to port 5

const int trig = 5;

 //connect echo pin of ultrasonic sensor to port 7

const int echo = 7;

 //giving motor connections as follows

const int m1a = 8;

const int m1b = 9;

const int m2a = 12;

const int m2b = 13;

void setup() 

{

  // activate serial monitor

 Serial.begin(9600);

 // defining trig pin as output since it produces sound waves

 pinMode(trig, OUTPUT);

 // defining echo pin as input since it receives sound waves

 pinMode(echo, INPUT);

 // defining motor pins as outputs

 pinMode(m1a, OUTPUT);

 pinMode(m1b, OUTPUT);

 pinMode(m2a, OUTPUT);

 pinMode(m2b, OUTPUT);

}

void loop() 

{

  // define two variables to store time and distance

 long duration, distance;

 // code for producing sound waves from transmitter part of sensor

 digitalWrite(trig, LOW);

 delayMicroseconds(2);

 digitalWrite(trig, HIGH);

 delayMicroseconds(10);

 digitalWrite(trig, LOW);

 // finding time using pulseIn function and assign it into the variable duration

 duration = pulseIn(echo, HIGH); // in microsecond

 // calculating distance by multiplying time and velocity (0.034 cm per microsecond)

 // it is then divided by 2 since the wave has traveled twice the distance between the sensor and the obstacle 

 distance = duration * 0.034/2; //in cm

// print distance on serial monitor 

Serial.println(distance);

// checking whether the distance is less than 20 cm (may be varied)

 if (distance < 20)

    {

      // give command to take turn (left or right). Below code may vary according to the connection

      digitalWrite(m1a, HIGH);

      digitalWrite(m1b, LOW);

      digitalWrite(m2a, LOW);

      digitalWrite(m2b, HIGH);

    }

// checking whether the distance is greater than or equal to 20 cm   

else if (distance >= 20)

   {

      // give command to go straight. Below code may vary according to the connection

      digitalWrite(m1a, HIGH);

      digitalWrite(m1b, LOW);

      digitalWrite(m2a, HIGH);

      digitalWrite(m2b, LOW);

   }

// giving a delay of one second   

delay(1000);

}
// recommended to visit Arduino website and Instructables website 

Additive Manufacturing

What is additive manufacturing? Before explaining additive manufacturing, let’s try to know what subtractive manufacturing is. Consider turning process in lathe machine as an example. There will be a blank of metal say mild steel and probably in cylindrical shape. We want to make something out of mild steel blank so what we do is we remove some material from it. That is we remove unwanted material from the work piece in other words we subtract material from the work piece so it is an example for subtractive manufacturing. Let’s take another example; we want to make a wooden door with creative designs on it. How would it be made? There will be a wooden material. After taking proper measurement, the unwanted materials are removed so that the remaining will result in the required shape and size. Here also we subtract material from the work piece so it is also an example for subtractive manufacturing. Then what will be additive manufacturing? It is nothing but adding something out of something to make something. In simple terms Additive Manufacturing (AM) is an umbrella term used to describe the technologies that builds 3D objects by adding layer upon layer of materials. That is we design the object and model it using CAD techniques. We input the CAD file into the machine and material will be supplied to the machine via filament like forms. The machine will read and understand the CAD file and produce the 3D object by adding layer upon layer fashion by accurately relating to the cross section of the object in the CAD file. 

The term 3D printing is commonly used in place of AM and the term 3D printer is used for a machine which works on AM techniques. Even though there are some differences between those but for understanding, those differences don’t matter for the time being. Then what is the principle of operation? There are many techniques or processes to produce 3D objects by adding layer upon layer; those will be explained in a different article. For the sake of understanding I mention some names. Stereo Lithography (SLA), Digital Light Processing (DLP), Free Form Fabrication (FFF), Electron Beam Machining (EBM), Selective Laser Sintering (SLS), Selective Deposition Lamination (SDL) etc.

Now let’s discuss the various application of additive manufacturing. Someone says that additive manufacturing technique is a revolution like computer and internet. We can agree or disagree with this but AM does create some revolution to the society. From the early stages to till now, medical industry is dominating the use of additive manufacturing techniques. These processes are not substitute for traditional manufacturing processes. For mass production these cost more. But the traditional manufacturing processes have many limitations. Conventional processes may not be suitable for working on new materials such as smart materials, composites and not economical if the needed parts are very less in number. There comes 3D printing. 3D printing or AM can be used to produce unique things in terms of material, shape or other design parameters. These are cost effective for unit things. They don’t look at the shape but they only consider the CAD file. They read what is there in CAD file after converting into the G-code and make the objects accordingly. This is very suitable for medical applications. The shape and size of heart, bone, tooth etc. will be different for different people and by 3D printing these can be made very easily. This is the reason why medical industry largely depends upon the AM techniques. 

Aerospace sector was also an early adopter of AM techniques. The aircraft and rocket components are made of different composite materials. Traditional manufacturing methods may not work well on these new materials. 3D printing overcomes this limitation. Secondly the rocket parts or aircraft parts have complex shapes and designs. Conventional machining methods may become expensive and face difficulty to produce such models. Even if it is possible to make these complex parts there is another big problem. That is these areas are of research interest. For research purpose or any other thing, the possibility of need of design change is higher. So the shape and size of the objects may also vary. Conventional subtractive manufacturing method becomes less use because of these factors. But AM does overcome these. There is no change needed for a 3D printer to produce an different object while there are many things from small scale to big scale is essential to be changed to meet the production of new object in traditional methods.

Automotive sector also started to use 3D printing techniques for manufacturing especially in sports cars and bikes because they can manufacture complex profiled parts without any extra cost. They can do new experiments. R&D works get simpler. Prototype development gets easier. Interestingly jewelry sector also exploits the power of additive manufacturing. They can try new designs and new models very easily. This is a huge advantage for them both in terms attracting customers and reducing cost. For the sake of demonstration, architectures also use 3D printing techniques. Astonishingly they now seek for direct construction method for building their firms. For making robotic components also 3D printing is very much useful. The application area of 3D printing or additive manufacturing is very large and actually it reduces the product life cycle time from ideation to actual product and there by now we can say that anything can be manufactured now whatever we think in our head.

There are also limitations for additive manufacturing. In most cases the problems are associated with the type of process or technique so those will be discussed in the respective article as I mentioned above. Some general cons of AM are discussed below. The time taken to produce one product is quit higher. Conventional processes make many things at little time and are suitable for mass production while additive manufacturing method is not suitable for mass production as it decreases the productivity. Even though for large firms, it is cost effective, it is expensive for small scale users. Buying a decent 3D printer itself costs high. There is also liability issue. The layered structure is also a problem. It decreases the smoothness and there by affects the quality. Even thought there are many limitations for additive manufacturing, more researches are being done and hope these problems will be vanished away. 

Unconditional love

Today, she called me many times; Morning, noon, evening and night! Because I was sick. She was very eager to know the condition of my health at each moment. In the morning, I told her that I would consult the doctor forenoon but I didn’t. In the evening, when she called and asked about the doctor’s comments, I replied that I hadn’t consulted the doctor. She became very angry and said so many things. I got very nice advises such as if you never consult, the illness would increase etc. ;) At the end of the evening, after sunset, I consulted the doctor and bought medicines and informed details to her. Then she became normal and got some satisfaction to mind. 

I thought how much she cares for me! From the birth to till now! I was a new born baby. She cared, loved and spent uncountable nights for me. Then I became a child. She cared, loved and taught what is good and what is bad. Then I started schooling. She cared, loved and enlightened me how to behave in society. Then I started to go to university away from home. She is caring, loving and praying for me every time. This is what we call it as Unconditional love and we get its purest form from our mothers. I love you my mother :)