Research Document
Rapid Prototyping
Introduction
Rapid Prototyping –also known as solid freeform fabrication– is a technology that takes a virtual design (3D CAD models) transforms the object into cross sections (layers). The RP software then creates each cross section laying down successive layers of liquid or other type of powdered material that will fuse together and solidify to create the final shape which represents an almost identical model.
Solid freeform fabrication compiles a set of manufacturing processes capable of producing complex solid objects directly from a computer model object without specifying tooling or any manufacturing processes. Most of the RP processes are additive processes. Rapid prototyping can represent a miniature manufacturing plant which comes with everything from material handling, information and materials processing that will reduce the costs and time of product development.
History of RP Technology
Topography
Topography is the study of earth’s surface features and it has been developed as early as in 1860Topography specifically involves the recording of relief or terrain, the three-dimensional aspect of the surface, and the identification of specific landforms. In contemporary practice, this involves generation of elevation data in electronic form. It is often includes the graphic representation of the landform on a map by a variety of techniques, including contour lines, hypsometric tints, and relief shading.
Photosculpture
Photosculpture arose in the 19th Century attempting to create accurate three-dimensional replicas of any object. Frenchman Francois Willeme in 1860 had sort of a successful development of this technology. Identifying several prints of different angles of the objects they could carve a sculpture that resembles the original.
These technologies, as they evolved, gave the initiative concepts for the development of rapid prototyping systems.
The first techniques for rapid prototyping became available in the 1980s and were used to produce models and prototype parts. Today, they are used for a much wider range of applications and are even used to manufacture production quality parts in relatively small numbers.
Rapid prototyping technologies have grown in importance and acceptance in the
Manufacturing companies face competitive pressures which have led to a wide development of tools and procedures that are designed to considerably reduce time-to-market cycles. Some of these tools include: computer-aided design (CAD), computer-aided manufacturing (
These tools can be called Time-compression technologies, which are all based on the concept of rapid prototyping.
Types of Rapid Prototyping
This RP system is one of the most used and it is considered to provide high accuracy and excellent surface finishes. Stereolithography is an additive fabrication process utilizing a vat of UV-sensitive photopolymer and a laser to build parts a layer at a time.
Stereolithography builds plastic parts or objects a layer at a time by tracing a laser beam on the surface of a vat of liquid photopolymer. This class of materials originally developed for the printing and packaging industries, quickly solidifies wherever the laser beam strikes the surface of the liquid. Once one layer is completely traced, it's lowered a small distance into the vat and a second layer is traced right on top of the first. The self-adhesive property of the material causes the layers to bond to one another and eventually form a complete, three-dimensional object after many such layers are formed.
Stereolithography requires the use of support structures to attach the part to the movable elevator and to prevent certain geometry from deflecting due to gravity. Supports are generated automatically during the preparation of 3D CAD models for use on the stereolithography machine, although they may be manipulated manually. Supports must be removed from the finished product manually.
Fused Deposition Modeling
FDM is the second most widely used rapid prototyping technology, after stereolithography. The technology was developed by S. Scott Crump in the late 1980s and was commercialized in 1990. The FDM technology is marketed exclusively by Stratasys Inc.
In FDM a plastic filament is unwound from a coil and supplies material to an extrusion nozzle. The nozzle is heated to melt the plastic and has a mechanism which allows the flow of the melted plastic to be turned on and off. The nozzle is mounted to a mechanical stage which can be moved in both horizontal and vertical directions. FDM prototypes essentially consist of partially bonded polymer filaments and voids. The bonding quality among filaments in FDM parts is an important factor in determining the integrity and mechanical properties of the resultant prototypes. The bonding quality, in this work, is assessed by the degree of Wetting or the size of the neck formed between adjacent filaments.
FDM is office-friendly, quiet and fairly fast for small parts on the order of a few cubic inches, or those that have tall, thin form-factors. The production of wide cross sections can become very slow. The finish of parts produced with FDM has been greatly improved over the years, but are not yet up to the level with stereolithography. The closest competitor to the FDM process is probably three dimensional printing. However, FDM offers greater strength and a wider range of materials.
Three-Dimensional Printing
Three dimensional printing is now a mature technology and it has widespread application in the fields of product marking. Direct ink-jet printing is a very attractive route for the free form fabrication of ceramics as fabrication of an object by droplet deposition.
The process starts by depositing a layer of powder object material at the top of a fabrication chamber. To accomplish this, a measured quantity of powder is first dispensed from a similar supply chamber by moving a piston upward incrementally. The roller then distributes and compresses the powder at the top of the fabrication chamber. The multi-channel jetting head subsequently deposits a liquid adhesive in a two dimensional pattern onto the layer of the powder which becomes bonded in the areas where the adhesive is deposited, to form a layer of the object. Once a layer is completed, the fabrication piston moves down by the thickness of a layer, and the process is repeated until the entire object is formed within the powder bed
Generally, 3D printing technologies remain the fastest and most cost-effective additive systems available. Subsequent developments of the technologies have seen them being adapted to produce multi-colored models, and various polymer resins have been introduced to enhance the mechanical properties of 3D printed parts.
Unlike "traditional" additive systems such as stereolithography and fused deposition modeling, 3D printing is optimized primarily for speed and low-cost, making it suitable for visualizing during the conceptual stages of engineering design when dimensional accuracy and mechanical strength of prototypes are not important.
Impacts
In order for industry to maintain its competitive edge in the global market, it is essential to improve the time required to develop new products. Improving the "time-to-market" concept can now be realized with the implementation of rapid prototyping. This process enables manufacturers to significantly reduce the development cycle, and considerably improve the design quality of a product.
Rapid prototyping technology can produce three-dimensional objects very quickly, without companies having to invest in expensive tooling techniques during the product development stage. These are computer-based design and manufacture processes, which are capable of producing high-precision parts from computer-generated data, rapidly and automatically.
The industries which will benefit from this technology are those involved in the design and production of various products that require a combination of electronic, plastic and metal components. Most of the major industries in
· Saving of money by automatically creating prototypes instead of by hand
· Improving product quality by testing and improving the design in an early stage of the design process, long before production tooling
· Improving communication within the design team and with third parties
· Unprecedented way to quickly make simple or complex parts directly from a CAD model, without tooling
· Instant feedback to engineering design allows for early error correction
· Flexibility and speed of operation allows for rapid response to design changes - optimize the design prior to full-scale production
· Provides a model for use in pre-production planning and tooling design
· Models can be finished and painted to resemble finished products
Reducing the time during the design process and improving the communication within the design team will dramatically impact the R & D process for companies. This means that the research and design teams are able to develop their works at different locations in the world without compromising quality and design in early stages of the process. RP has allowed customers and companies to share STL files (common RP software file) in order to finalize a prototype of a product that is intended to hit the global market.
References
Pique, A., Holmes, A., Dimes, D. (2003) Rapid Prototyping Technologies. ( Pgs. 23, 73, 113)
Beaman, J., Barlow, J., Bourell, D., Crawford, R. (1997) A new direction in Manufacturing. Thermal Laser Processing. Norwell, MA. Kluwer Academic Publisher.
Sriraman, V., DeLeon, J., Winek, G.(2002) Selecting the appropriate rapid prototyping system for an engineering technology program. Journal of Engineering Technology. Retrieved
Three Dimensional Printing System suits office environments. Product News Network, (
Fused Deposition Modeling (
Rapid Prototyping (
Stereolithography (