Exploring the Possibilities of Rapid Prototyping

INTRODUCTION

 Rapid Prototyping (RP) can be defined as a group of techniques used to quickly fabricate a scale model of a part or assembly using three-dimensional computer aided design (CAD) data. Rapid Prototyping is also known as 3D printing or additive manufacturing (AM). 3D printing is a process for making a 3D object of any shape from a 3D model or other electronic data sources through additive processes in which successive layers of material are laid down under computer controls. The first RP technique, Stereolithography, was developed by 3D Systems of Valencia, CA, USA. The company was founded in 1986, and since then, a number of different RP techniques have become available. Nowadays, rapid prototyping has a wide range of applications in various fields of human activity: research, engineering, medical industry, military, construction, architecture, fashion, education, the computer industry and many others. In 1990, the plastic extrusion technology most widely associated with the term "3D printing" was invented by Stratasys by name fused deposition modeling (FDM). After the start of the 21st century, there has been a large growth in the sales of 3D printing machines and their price has been dropped gradually. Rapid Prototyping has also been referred to as solid free-form manufacturing, computer automated manufacturing, and layered manufacturing. RP has obvious use as a vehicle for visualization. In addition, RP models can be used for testing, such as when an airfoil shape is put into a wind tunnel. RP models can be used to create male models for tooling, such as silicone rubber molds and investment casts. In some cases, the RP part can be the final part, but typically the RP material is not strong or accurate enough. When the RP material is suitable, highly convoluted shapes (including parts nested within parts) can be produced because of the nature of RP. By the early 2010s, the terms 3D printing and additive manufacturing evolved senses in which they were alternate umbrella terms for AM technologies, one being used in popular vernacular by consumer - maker communities and the media, and the other used officially by industrial AM end use part producers, AM machine manufacturers, and global technical standards organizations.

Rapid prototyping

WHAT IS RAPID PROTOTYPING?

 Rapid Prototyping is the "process of quickly building and evaluating a series of prototypes" early and often throughout the design process. Prototypes are usually incomplete examples of what a final product may look like. Each time a prototype is used, a formative evaluation gathers information for the next, revised prototype. This cycle continues to refine the product until the final needs and objectives are met. The following diagram demonstrates the non-linear nature of Rapid Prototyping.  

Rapid Prototyping model

WHY RAPID PROTOTYPING?

 The reasons of Rapid Prototyping are 

• To increase effective communication. 
• To decrease development time. 
• To decrease costly mistakes. 
• To minimize sustaining engineering changes.
• To extend product lifetime by adding necessary features and eliminating redundant features early in the design. 

 Rapid Prototyping decreases development time by allowing corrections to a product to be made early in the process. By giving engineering, manufacturing, marketing, and purchasing a look at the product early in the design process, mistakes can be corrected and changes can be made while they are still inexpensive. The trends in manufacturing industries continue to emphasize the following: 

•  Increasing number of variants of products. 
•  Increasing product complexity. 
•  Decreasing product lifetime before obsolescence. 
•  Decreasing delivery time. 

 Rapid Prototyping improves product development by enabling better communication in a concurrent engineering environment. 

BASIC PROCESS

 Although several rapid prototyping techniques exist, all employ the same basic five-step process. The steps are: 

1. Create a CAD model of the design. 
2. Convert the CAD model to STL format. 
3. Slice the STL file into thin cross-sectional layers. 
4. Construct the model one layer atop another. 
5. Clean and finish the model.

DIFFERENT TYPES OF 3D PRINTING TECHNOLOGIES 

 

1. Fused Deposition Modeling (FDM) 

        Fused deposition modeling (FDM) method was developed by S. Scott Crump in the late 1980s and was designed in 1990 by Stratasys. After the patent on this technology expired, a large open source development community developed and commercial variants utilizing this type of 3D printer appeared. As a result, the price of FDM technology has dropped by two orders of magnitude since its creation. FDM also known as Fused Filament Fabrication (FFF) is a 3D printing technology that uses a process called Material Extrusion. Material Extrusion devices are the most widely available - and inexpensive - of the types of 3D printing technology in the world today. They work by a process where a spool of filament of solid thermoplastic material (PLA, ABS, PET) is loaded into the 3D printer. It is then pushed by a motor through a heated nozzle, where it melts. The printer’s extrusion head then moves along specific coordinates, depositing the 3D printing material on a build platform where the printer filament cools and solidifies, forming a solid object. Once the layer is complete, the printer lays down another layer, repeating the process until the object is fully formed. Depending on the object’s complexity and geometry, support structures are sometimes added, for example, if the object has steep overhanging parts. Common applications for FDM include electrical housings, form and fit testing’s, jigs and fixtures, and investment casting patterns. Strengths of FDM are that it offers the best surface finish plus full color along with the fact there are multiple materials available for its use. It is limited by being brittle, therefore unsuitable for mechanical parts. In this technique, the model is produced by extruding small beads of material which harden to form layers. A thermoplastic filament or wire that is wound into a coil is unwinding to supply material to an extrusion nozzle head. The nozzle head heats the material up to the certain temperature and turns the flow on and off. Typically, the stepper motors are employed to move the extrusion head in the z-direction and adjust the flow according to the requirements. The head can be moved in both horizontal and vertical directions, and control of the mechanism is done by a computer-aided manufacturing (CAM) software package running on a microcontroller.

Fused Deposition Modeling (FDM) 

2. Stereolithography (SLA) 

        Stereolithography is an early and widely used 3D printing technology. 3D printing was invented with the intent of allowing engineers to create prototypes of their own designs in a more time and in an effective manner. The technology first appeared as early as 1970. Dr. Hideo Kodama Japanese researcher first invented the modern layered approach to stereolithography by using UV light to cure photosensitive polymers. On July 1984, before Chuck Hull filed his own patent and Alain Le Mehaute filed a patent for the stereolithography process. The French inventor’s patent application was neglected by the French General Electric Company and by CILAS (The Laser Consortium). Le Mehaute believes that abandonment reflects a problem with innovation in France. Stereolithography is a form of 3-D printing technology used for creating models, prototypes, patterns in a layer by layer fashion using photo polymerization, a process by which light causes chains of molecules to link together, forming polymers. Those polymers then make up the body of a three-dimensional solid. Research in the area had been conducted during the 1970s, but the term was coined by Charles (Chuck) W. Hull in 1986 when he patented the process. He then set up 3D Systems Inc. to commercialize his patent. It works by a 3D printing method called Vat Polymerization where a material called a photopolymer resin (Standard, Castable, Transparent, High Temperature) in a vat is selectively cured by a light source. Specifically, an SLA printer uses mirrors, called galvanometers or galvos, where one is positioned on the X-axis, the other on the Y-axis. These galvos aim the point of a laser beam across the vat of resin, selectively curing and solidifying a cross-section of the object in the build area, building it up layer by layer.

Stereolithography (SLA) 

3. Selective Laser Sintering (SLS)

 

        Selective laser sintering (SLS) was developed and patented by Dr. Carl Deckard and academic adviser, Dr. Joe Beaman at the University of Texas in the mid-1980, under the sponsorship of DARPA. Deckard was involved in the resulting start-up company DTM, established to design and build the selective laser sintering machines. In the year 2001, 3D Systems the biggest competitor of DTM acquired DTM. The most recent patent regarding Deckard's selective laser sintering technology was issued on January 1997 and expired on Jan 2014. Selective laser sintering is a 3D-printing technique that uses a laser as the power source to sinter powdered material (mostly metal), aiming the laser at points in space defined by a 3D model, binding the material to create a solid structure. Selective laser melting uses a comparable concept, but in SLM the material is fully melted than sintered, allowing different properties (crystal structure, porosity). SLS is a relatively new technology that so far has mainly been used for additive manufacturing and for low-volume production of parts. Production roles are expanding as the commercialization of additive manufacturing technology improves.

Selective Laser Sintering (SLS)

4. Selective Laser Melting (SLM)

 

        SLM made its debut appearance back in 1995. It was part of a German research project at the Fraunhofer Institute ILT, located in the country’s most western city of Aachen. Like SLA, SLM also uses a high-powered laser beam to form 3D parts. During the printing process, the laser beam melts and fuses various metallic powders together. The simple way to look at this is to break down the basic process like thus: Powdered material + heat + precision + layered structure = a perfect 3D object. As the laser beam hits a thin layer of the material, it selectively joins or welds the particles together. After one complete print cycle, the printer adds a new layer of powered material to the previous one. The object then lowers by the precise amount of the thickness of a single layer. When the print process is complete, someone will manually remove the unused powder from the object. The main difference between SLM and SLS is that SLM completely melts the powder, whereas SLS only partly melts it (sinters). In general, SLM end products tend to be stronger as they have fewer or no voids. A common use for SLM printing is with 3D parts that have complex structures, geometries and thin walls. The aerospace industry uses SLM 3D printing in some of its pioneering projects. These are typically those which focus on precise, durable, lightweight parts. It’s a costly technology, though, and so not practical or popular with home users for that reason. SLM is quite widespread now among the aerospace and medical orthopedics industries. Those who invest in SLM 3D printers include researchers, universities, and metal powder developers. There are others too, who are keen to explore the full range and future potential of metal additive manufacturing in particular.

Selective Laser Melting (SLM) 

 

ADVANTAGES OF RAPID PROTOTYPING 

1. Time-to-Market: 

3D printing allows ideas to develop faster. Being able to print a concept on the same day it was designed shrinks a development process from what might have been months to a number of days, helping companies stay one step ahead of the other.

2. Save Money: 

Prototyping injection mold tools and production runs are expensive investments. The 3D printing process allows the creation of parts and/or tools through additive manufacturing at rates much lower than traditional machining. 

3. Mitigate Risk: 

Being able to verify a design before investing in an expensive molding tool is worth its weight in 3D printed plastic, and then some. It is far cheaper to 3D print a test prototype than to redesign or alter an existing mold. 

4. Feedback: 

With a prototype, you can test the market by unveiling it at a tradeshow, showing it to buyers or raising capital by pre-selling on Indigo or Kick-starter. Getting buyer's response to the product before it actually goes into production is a valuable way to verify the product has market potential. 

5. Get the Feel: 

One thing you can't get a picture or virtual prototype on the computer screen is the way something feels in your hand. If you want to ensure the ergonomics and fit of a product are just right, you must actually hold it, use it and test it. 

6. Personalize It: 

With standard mass-production, all parts come off the assembly line or out of the mold the same. With 3D printing, one can personalize, customize a part to uniquely fit their needs, which allows for custom fits in the medical industries and helps set people to elaborate their idea in new world. 

7. Build your Imagination: 

In the modern boom of digital art and design, the possibilities are not only accelerating but limitless. One can now 3D prints almost everything they imagine after drawing it up virtually or by other. In a relatively short time, an idea, concept, dream or invention can go from a simple thought to a produced part. 

8. Square Holes? No Problem: 

The limitations of standard machining have constrained product design for years. With the improvements in AM, now the possibilities are endless. Geometry that has been historically difficult to build; like holes that change direction, unrealistic overhangs is now possible and actually simple to construct. 

9. Fail Fast, Fail Cheap: 

3D printing allows a product developer to make breakthroughs at early stages that are relatively inexpensive leading to better products and less expensive dead-ends.

DISADVANTAGE OF RAPID PROTOTYPING 

1. Intellectual property issues: 

The ease with which replicas can be created using 3D technology raises issues over intellectual property rights. The availability of blueprints online free of cost may change with for-profit organizations wanting to generate profits from this new technology. 

2. Limitations of size: 

3D printing technology is currently limited by size constraints. Very large objects are still not feasible when built using 3D printers. 

3. Limitations of raw material: 

At present, 3D printers can work with approximately 100 different raw materials. This is insignificant when compared with the enormous range of raw materials used in traditional manufacturing. More research is required to devise methods to enable 3D printed products to be more durable and robust. 

4. Cost of printers: 

The cost of buying a 3D printer still does not make its purchase by the average householder feasible. Also, different 3D printers are required in order to print different types of objects. Also, printers that can manufacture in color are costlier than those that print monochrome objects. 

5. Fewer Manufacturing Jobs: 

As with all new technologies, manufacturing jobs will decrease. This disadvantage can have a large impact to the economies of third world countries especially China, that depend on a large number of low skill jobs. 

6. Unchecked production of danger items: 

Liberator, the world’s first 3D printed functional gun, showed how easy it was to produce one’s own weapons, provided one had access to the design and a 3D printer. Governments will need to devise ways and means to check this dangerous tendency.

APPLICATIONS OF RAPID PROTOTYPING 

1. Aeronautics and Aerospace Industry 

The Aeronautics and Aerospace industries push the limits of geometric design complexity; the evolution and consistent improvement of the vehicles demand that the parts become more efficient and accurate even as the size of the vessels become smaller. This is why design optimization is essential to the progression of the industry. Optimizing a design can be challenging when using traditional manufacturing processes, and that's why most engineers have turned to 3D Printing. 

2. Medical Sector 

To support new product development for the medical and dental industries, the technologies are also utilized to make patterns for the downstream metal casting of dental crowns and in the manufacture of tools over which plastic is being vacuum formed to make dental aligners. Rapid prototyping is being used to manufacture replicas of parts of the body to enable surgeons to have accurate pre-operative planning meetings. Most of the applications so far have been involved with the manufacture of bone replicas. Obtaining scan data for bones is relatively easy. Recent use has covered the manufacture of replicas of soft tissue such as heart valves, etc. 

3. Jewellery Sector 

For the jewellery sector, 3D printing has proved to be particularly disruptive. There is a great deal of interest and uptake based on how 3D printing can, and will, contribute to the further development of this industry. From new design freedoms enabled by 3D CAD and 3D printing, through improving traditional processes for jewelry production all the way to direct 3D printed production eliminating many of the traditional steps. 

4. Architecture 

Architectural models have long been a staple application of 3D printing processes, for producing accurate demonstration models of an architect's vision. 3D printing offers a relatively fast, easy and economically viable method of producing detailed models directly from 3D CAD, BIM or other digital data that architects use. 

5. Fashion Industry 

As 3D printing processes have improved in terms of resolution and more flexible materials, one industry, renowned for experimentation and outrageous statements, has come to the fore. We are of course talking about fashion.3D printed accessories including shoes, headpieces, hats, and bags have all made their way on to global catwalks. 

6. Foundry Industry 

A major use for rapid prototyping now is in the foundry industry. Models are used as patterns for sand and plaster casting or used as sacrificial models in investment casting. Accuracy of investment castings from stereolithography is very good and often within f0.15mm. Another advantage is that the models are stronger than waxes and so can withstand handling of thin sections much better.   

CONCLUSION 

3D Printing technology could revolutionize the world. Advances in 3D printing technology can significantly change and improve the way we manufacture products and produce goods worldwide. An object is scanned or designed with Computer Aided Design software, then sliced up into thin layers, which can then be printed out to form a solid three-dimensional (3D) product. As shown, 3D printing can have an application in almost all of the categories of human needs as described by Maslow. While it may not fill an empty unloved heart, it will provide companies and individuals fast and easy manufacturing in any size or scale limited only by their imagination. 3D printing, on the other hand, can enable fast, reliable, and repeatable means of producing tailor-made products which can still be made inexpensively due to automation of processes and distribution of manufacturing needs. One can conclude that the 3D printing technology's importance and social impact increase gradually day by day and influence the human's life, the economy, and modern society.