3D printing is any of various processes in which material is joined or solidified under computer control to create a three-dimensional object, with material being added together (such as liquid molecules or powder grains being fused together, typically layer by layer. In the 1990s, 3D printing techniques were considered suitable only for the production of functional or aesthetical prototypes and a more appropriate term was rapid prototyping. Today, the precision, repeatability and material range have increased to the point that 3D printing is considered as an industrial production technology, with the name of additive manufacturing. 3D printed objects can have a very complex shape or geometry and are always produced starting from a digital 3D model or a CAD file. There are many different 3D printing processes, that can be grouped into seven categories:

The most commonly used 3D Printing process is a material extrusion technique called fused deposition modeling

(FDM). Metal Powder bed fusionis gaining prominence lately during the immense applications of metal parts in the industry. In 3D Printing, a three-dimensional object is built from computer-aided design (CAD) model, usually by successively adding material layer by layer, unlike the conventional machining process, where material is removed from a stock item, or the casting and forging processes which date to antiquity.

The term "3D printing" originally referred to a process that deposits a binder material onto a powder bed with inkjet printer heads layer by layer. More recently, the term is being used in popular vernacular to encompass a wider variety of additive manufacturing techniques. United States and global technical standards use the official term additive manufacturing for this broader sense.

The 3D printers available at our lab are

ULTIMAKER 2

DIMENSION sst 1200es

ULTIMAKER 2 : Driven by two motors, the nozzle can moves in the X & Y directions along the guide rails. A third motor moves the build plate in the Z direction making it possible to print 3D objects. Another motor near the filament spool at the rear side pushes the material into the nozzle. The melting temperature for each material is different and is to be set accordingly in the machine by setting the temperature of nozzle. The temperature of build plate have to be set accordingly to avoid cooling of the material during the printing. There are cooling fans around the nozzle which cools down the thermoplastic as soon as it is fused and deposited. The supports for the object is also printed using the same material and have to be manually removed.

 

The ultimaker 2 can print three different materials, namely the

- ABS(Acrylonitrile butadiene styrene),

- PLA (Polylactic Acid), and

- CPE (Copolyester).

 

DIMENSION sst 1200es : is a professional quality printer which can print only ABS (Acrylonitrile Butadiene Styrene). It uses separate support material for the object which can be removed by immersing the printed object in a heated solution for 24 hours.

 

Design Considerations

3D software file - STL file - G-Code

The object has to be designed in a 3D software and has to be exported as an STL file. The STL file has to be then

imported into the bundled software of the 3D printer (Cura in case of Ultimaker 2) for generating the G-Code. The printer will print the object in accordance with the G-Code. There are several parameters to be considered during the design and also during the generation of G-Code.

 

1. Material PLA is made from organic material and is biodegradable at controlled environments. In terms of overall strength, ABS slightly outperforms the PLA. ABS is non biodegradable and is used for professional applications like electronic housings etc for its high ductility and machinability after printing. PLA has a lower printing temperature when compared to ABS and is less likely to warp when compared with ABS. The material filament comes in spools.

 

2. Size & Orientation of the Final Object The size of the final object has to be kept well within the build volume of the 3D printer. The object has to be scaled down, if the design file is greater than the build volume of the printer. The bundled software while generating the G-Code, considers the supports needed for making the object stable during the printing operation. The orientation of the design is to be selected such that only the least support is generated during the printing operation. The same can be verified by selecting "Layer" view in the Cura software.

 

3. Layer Height The height of each layer deposited can be defined in the bundled software before generating the

G-Code. Lesser the layer height, more is the quality and finish of the print and also the time taken to print.

 

4. Shell Thickness Even if the object designed in the 3D software is a solid one, the density inside the object can be reduced, while keeping full density for the outer shell of the object. The thickness of the outer shell can be adjusted in the software according to the structural purpose of the object. The shell thickness specified during the generation of G-Code will be uniformly applied to every part/projection of the object.

 

5. Retraction This parameter defines the flow of the material through the nozzle while the nozzle moves between

discontinuous points in the object. When retraction is enabled, the material will be pulled inside the nozzle while the nozzle moves between two points. If not enabled, the nozzle will continuously eject the molten material out, leaving a fine line of material along the path travelled. Enabling retraction can compromise the quality of the print for the material will experience a delay while coming out through the nozzle leaving small pits and peaks in the deposited layers.

 

6. Bottom/Top thickness of the Fill This parameter defines the thickness of the bottom and top most part of the object. Similar to the shell thickness, it can affect the strength of the printed object. In between the top and bottom layer, the density of the object can be reduced.

 

7. Fill Density This defines the density of the print inside the object. By varying this parameter, the density of print can be adjusted. This will not affect the density of the outer layer. By reducing the fill density, considerable savings in the consumption of material can be attained, however it compromises the overall strength of the final object. The fill density has to be selected keeping in mind of the structural application of the object.

 

8. Print Speed This defines the speed of the horizontal movement of the nozzle from one point to the other. Lesser print speed will increase the quality of the print but will take more time.

 

9. Support Type Almost of the designed object which are to be 3D printed will need supports at some places or the other. The nozzle will deposit the material in layers, and in the absence of a proper support, the material coming out from the nozzle will fall down due to gravity, making the entire job useless. In order to keep the molten material at the intended place, supports are to be provided. The supports will be printed along with the object and has to be removed after the printing operation is finished. The support can be given "everywhere" or just from the "build plate". If the support selected is "everywhere", the software will generate the supports at all the necessary points. In this case, the supports will be provided from the build plate and also from the object itself. If the support type selected is "build plate", supports will be generated only from the build plate. The supports are to be removed from the

object after the printing job is completed.

 

10. Platform adhesion type During the printing operation, the object has to be held firmly to the build plate. For achieving the same, the software will generate a foundation like structure for the object. The machine will begin by first printing this foundation upon which the printing of the object will be carried out. This foundation has to be removed from the object after the completion of the printing operation. There are two types of support namely "brim" and "raft". If the option selected is "Brim", the machine will create a thin layer of material to act as the adhesion platform. This type of platform adhesion is the generally used one. If the option selected is "Raft", a thick layer of material will be deposited by the machine atop which the object will be printed. This type of platform adhesion is required for tall objects and for objects which has comparatively less cross sectional area at the bottom most part.

 

11. Support Material & Removal of supports The support is printed along with the model and is to be removed after the printing operation is finished. The Ultimaker 2 uses a single material to print the object and the supports and hence the supports are to be manually removed from the object.

 

DIMENSION sst 1200es uses a different support material which is soluble and can be easily removed by immersing the printed object in a chemical solution.

 

A test design files was downloaded from https://www.thingiverse.com/thing:1363023 and printed with a Nozzle Diameter of 0.4mm,"Brim" type platform Adhesion and with no supports. Layer Height of 0.08mm, Shell Thickness of 0.8mm, Bottom/Top Thickness of 0.8mm, 35% Fill Density and 50mm/s print Speed was set in Cura software which showed 1Hr and 54 Min to print. The nozzle temperature was set to 240 degree celsius and base plate temperature was set as 80 degree celcius. Below image shows the printed object.

I decided to 3d print a mobius strip with voronoi pattern on it. I used Rhinoceros and Grasshopper to do the design.

The scanning device available in our lab is Microsoft Kinect sensor to scan 3D objects. It consists of an infrared sensor, a RGB VGA video camera which finds the distance from the sensor to the 3D point in the surface of the 3D material.

We have to rotate the object and simultaneously take photo in a series.

The camera detects the red, green, and blue color components as well as body-type and facial features. It has a pixel resolution of 640x480 and a frame rate of 30 fps. This helps in facial recognition and body recognition. The depth sensor contains a monochrome CMOS sensor and infrared projector that help create the 3D imagery throughout the room. It also measures the distance of each point of the player’s body by transmitting invisible near-infrared light and measuring its “time of flight” after it reflects off the objects.

I used Kscan 3D software to scan myself. There are two methods you can use in order to capture scans:

Single scan method

Batch scanning method.

 

Both methods feature a number of adjustable parameters to suit your preferred way of scanning an object. Finally the scanned images are combined in the software to prepared and exported as stl.

I sat on a Revolving chair and provided proper light source. I took my lab mate's help to click the photo in Kscan 3D software. These images are stitched together to get the required 3D projection file.

 

I exported the file in STL format and opened in Cura softawsre and it was comparatively a bigger image and managed to scale it down. After that the STL was sliced and turned into a Gcode.