Want more information on automotive parts rapid prototype factories? Feel free to contact us.

Abstract

The word rapid prototyping (RP) was first used in mechanical engineering field in the early 1980s to describe the act of producing a prototype, a unique product, the first product, or a reference model. In the past, prototypes were handmade by sculpting or casting, and their fabrication demanded a long time. Any and every prototype should undergo evaluation, correction of defects, and approval before the beginning of its mass or large scale production. Prototypes may also be used for specific or restricted purposes, in which case they are usually called a preseries model. With the development of information technology, three-dimensional models can be devised and built based on virtual prototypes. Computers can now be used to create accurately detailed projects that can be assessed from different perspectives in a process known as computer aided design (CAD). To materialize virtual objects using CAD, a computer aided manufacture (CAM) process has been developed. To transform a virtual file into a real object, CAM operates using a machine connected to a computer, similar to a printer or peripheral device. In 1987, Brix and Lambrecht used, for the first time, a prototype in health care. It was a three-dimensional model manufactured using a computer numerical control device, a type of machine that was the predecessor of RP. In 1991, human anatomy models produced with a technology called stereolithography were first used in a maxillofacial surgery clinic in Viena.

KEY WORDS:

Computed tomography, computer-aided designing, medical resonance imaging, prototypes, rapid prototyping, stereolithography

The term rapid prototyping (RP) designates a set of technologies that allow the realization of automatic physical models based on design data, all through the aid of a computer. These “three-dimensional printers” allow designers to quickly generate defined prototypes of their designs, rather than the simple two-dimensional images. These Prototypes of such achievements provide valuable visual aids. The shift from the visual to the visual-tactile representation of physical objects introduced a new kind of interaction called “touch to comprehend”. In the early days of RP, automotive and aerospace industries dominated the RP application. But this is no longer the case as RP has spread into many other industries.

It has revolutionized the engineering and science, by integrating itself into many aspects of the modern life from entertainment through medicine. It all started in the 70s, when it spreads a new method of medical information based X-ray, that is, the tomographic examination or computerized tomography (CT). RP technologies are a new approach for surgical planning and simulation. They reproduced anatomical objects as three-dimensional physical models, which give the surgeon a realistic impression of complex structures before a surgical intervention.

The need of facing the geometrical complexity has introduced RP into the dental field. It has the potential to become the next generation in fabrication methods in dentistry. Beyond its known contribution related with the diagnosis, education, and surgical planning. This technology is being used in wide areas of dentistry including prosthodontics.

The emergence of the RP technology into prosthodontics has innovated the clinical and laboratory procedures by eliminating or abolishing some intermediate stages and independing the quality of the outcomes from the practitioners skills. This indicates the potential of the new method, which is capable of replacing the traditional “impression-taking and waxing” procedure. RP methods are used to substantially shorten the time for developing patterns, molds, and prototypes. There are many different RP technologies available.

However, the field of RP is still new with much effort to be expanded on improving the speed, accuracy and reliability of the system and widen the range of materials for prototype construction. So the clinician should be aware of potential areas for inaccuracies within models and review the source image in cases where models integrity is in doubt. Another area of improvement will be the cost efficiency as most RP systems are currently too expensive to be affordable.

Basic Principle

The key idea of this new RP technology is based on the decomposition of three-dimensional computer models in the layers section transverse thin, followed physically forming layers and piling layer by layer. The generation of three-dimensional objects in this manner is an idea almost as old as human civilization. The developments since the Egyptian pyramids were probably block developed layer by layer [ ].[1]

Classification of Rapid Prototyping Method

Rapid prototyping technologies may be divided broadly into those involving the addition of material and those involving its removal. According to Kurth, the materials accretion technologies may be divided by the state-of the prototype material before part formation. The liquid based technologies may entail the solidification of the resin on contact with a laser, the solidification of an electrosetting fluid, or the melting and subsequent solidification of prototyping material. The processes using powders compound them either with a laser or by the selective application of binding agent. Those processes that use solid sheets may be classified according to whether the sheets are bonded with a laser or with an adhesive [ ].[1]

The most popular among currently available RP technologies is perhaps stereolithography and is the first commercially available rapid prototype. Stereolithography apparatus was invented by Charle Hull of 3D Systems Inc. This relies on a photosensitive monomer resin which from a polymer and solidifies when exposed to ultraviolet (UV) light. Due to the absorption and scattering of the beam this reaction only takes place near the surface. This produces parabolically cylindrical voxels which are characterized by horizontal line width and vertical cure depth. An stereolithography machine consists of a build platform (substrate) which is mounted in a vat of resin and a UV helium-cadmium or argon ion laser.[2] The first layer of the part is imaged on the resin surface by the using information obtained from the three-dimensional solid CAD model. Once the contour of the layer has been scanned, and the interior either hatched or solidly filled, the platform is next lowered to the base of the vat in order to coat the part thoroughly. It is then raised such that the top of the solidified part is level with the surface and a blade wipes the resin leaving exactly one layer of resin above the part. The part is then lowered to one layer below the surface and left until the liquid has settled. This is done to ensure a flat, even surface and to inhibit bubbles formation. The next layer may then be scanned.[3]

Medical Applications of Rapid Prototyping

Medical rapid prototyping is defined as the manufacture of dimensionally accurate physical models of human anatomy derived from medical image data using a variety of RP technologies.[4] Some RP machines had already been in experimental use in the 1970s, and CT was invented in the 1960s by Godfrey N Hounsfield, an electronics engineer, in collaboration with Allan McLeod Cormack, a physicist. However, it was only in the 1990s that an actual three-dimensional model was built to reproduce the anatomy of a patient based on CT images obtained during that patient's examination, thanks to advances in CT scanner quality and the development of specific software for this purpose. RP has been applied to a range of medical specialties, including oral and maxillofacial surgery, dental implantology, neurosurgery, and orthopedics.

Complex diseases in medicine often demand time-consuming surgery. Surgical planning tries to minimize the duration of surgery to reduce the risk of complications. In addition to the normally used imaging modalities, three-dimensional visualization techniques can be applied for supporting the planning process. Such visual representation of medical objects allows simulation of surgical procedures before surgery. The greatest advantage of RP technologies is the precise reproduction of objects from a three-dimensional medical image data set as a physical model which can be looked at and touched by the surgeon.[5]

Medical rapid prototyping is also being developed for use in dental implants. Greater accuracy was achieved with the use of rapid prototyped surgical guides for creating osteotomies in the jaw, and a computer-assisted design/computer-assisted manufacture (CAD/CAM) approach to the fabrication of partial dental frameworks has been developed.[4]

Dental Application of Rapid Prototyping

Orthodontics

Using state-of-the-art CAD/CAM technology, the two normally separate processes of bracket production and bracket positioning are fused into one unit. In this process, the demand for maximum individuality with simultaneously minimized space requirements is put consistently into practice.[6] Another innovative use of the CAD/CAM technology was to create an overcrown able to open the bite through clinical crown lengthening of the mandibular second premolars. Some technology provides clear plastic orthodontic treatment devices. Every one to 2 weeks, the patient receives a new set of splint-like aligners that are intended to continue moving their teeth.[7] This technology utilizes several stereolithography machines to fabricate models upon which plastic sheets are molded. Data sets are obtained by digitizing an impression taken of the patient's teeth. The resulting point sets are separated into individual tooth geometries, which are then positioned according to the orthodontist's treatment plan.

Oral Surgery

Anatomic medical models built with RP technologies represent a new approach for surgical planning and simulation. These techniques allow one to reproduce anatomical objects such as three-dimensional physical models of the skull or other structures, which give the surgeon a realistic impression of complex structures before surgical intervention. The shift from the visual to the visual-tactile representation of anatomical objects introduces a new kind of interaction called “touch to comprehend”.[2] Clinical data indicate that computer-aided RP may be of value in minimizing the extra-oral time and possible injury to transplanted teeth during the process of autotransplantation.[12]

Implantology

Since the advent of osseointegration, the use of dental implants has evolved rapidly over the last decade. Research in the field of oral implantology has led to refinements resulting in highly successful and predictable restorative options for partially as well as completely edentulous patients; however, improper implant placement can have a profound and often detrimental effect on the long-term predictability and success of the implant-supported prosthesis.[8]

The use of computer-aided design/computer-aided manufacturing (CAD/CAM) technology has gained popularity in implant dentistry. The applications pertain to three-dimensional imaging, 3D software (Delcan India, Maharashtra) for treatment planning, fabrication of computer-generated surgical guides using additive RP, as well as fabrication of all-ceramic restorations using subtractive RP.[13] RP technology allows for industrial fabrication of customized three-dimensional objects from computer-aided design (CAD) data.[9]

Maxillofacial Prosthesis

Absence of all or part of the external ear may be either acquired or congenital. When attempting to restore this part with prosthesis, the prosthesis should ideally be customized to restore the anatomy as closely as possible. In so doing, it may be helpful to have a priori knowledge of average values for each index and use these values to help construct prosthesis of the appropriate size and shape. However, individual proportion indices vary from the average, so where the defect is unilateral it is more practical to compare and duplicate proportions from the nondefect side.[10] This process can be difficult and time consuming and demands a high level of artistic skill to form a mirror image and achieve a good esthetic match. Similarly, patients with existing prostheses may need frequent replacements because of color changes, loss of fit, tearing, aging, contamination of the material and general wear. Conventional duplication procedures are often unreliable and inaccurate, as errors may occur at any one of many stages during production.[11]

The advent of CT and magnetic resonance imaging with three-dimensional representation of human anatomy has opened up new perspectives for design and production in the medical field computer manipulation of the data allows for mirroring or modifications to establish the exact dimensions needed, and a computer numeric controlled (CNC) milling machine can be used to manufacture a template for the final prosthesis. CNC milling, however, is limited by difficulties encountered when trying to replicate the complex anatomy of internal features.

The development of RP systems has led to the creation of customized three-dimensional anatomic models that exhibit a level of complexity unknown with CNC-based equipment, primarily because RP methodologies use an additive process of building an object in layers defined by a computer model that has been virtually sliced.[3] This allows for the production of complex shapes with internal detail and undercut areas. One such method is stereolithography, which produces three-dimensional objects by curing a liquid resin under a computer-guided laser. A newer system is the Thermojet Printer (3D Systems): Shenzhen Towell Model Technology Co., Ltd., Shenzhen, China, which operates as a network printer and uses wax as the building material. The advantage of such a system is the ability to cast directly from a wax model.

Applications in maxillofacial prosthodontics

• Production of auricular and nasal prosthesis

• Obturators

• Duplication of existing maxillary/mandibular prosthesis especially crucial when an accurate fit to natural teeth or an osseointegrated implant is needed

• Manufacturing of surgical stents for patients with large tumors scheduled for excision

• Manufacturing of lead shields to protect healthy tissue during radiotherapy treatment

  If you are looking for more details, kindly visit low-pressure overmoulding injection molding process.

  Recommended article:
  Pour Strips and Constructability
• 
  Well Testing Surface Safety Valve (SSV)

  Fabrications of burn stents, where burned area can be scanned rather than subjecting delicate, sensitive burn tissue to impression-taking procedures.

Footnotes

Source of Support: Nil

Conflict of Interest: None declared.

Rapid Prototyping: the Evolution of 3D Printing

Shares

Rapid prototyping has, since its inception, been one of the main advantages of additive manufacturing. While prototypes could take days, weeks or even months using earlier technologies, with additive manufacturing, prototypes can be produced virtually overnight, speeding up the product design and development stage significantly.
 
The ability to create concept or durable, functional prototypes in a fraction of the time makes 3D printing the ideal solution to go from ideation to production much more quickly. Today, we’ll take a look at the evolution of rapid prototyping and AM, and their value for the product development stage. 
 

What is Rapid Prototyping?

Rapid prototyping refers to the rapid production of models and prototypes using CAD data. Such models are visually and/or functionally tested and validated during the product development stage.
 
There are multiple benefits of rapid prototyping, not least because it provides a cost-effective way to evaluate and test performance before producing the final product. While other methods such as injection moulding can be used for prototyping, this may not always be the right option, due to the high tooling costs involved, and the inability to make quick design changes.
 
The quest for more innovative design solutions and faster speed-to-market has therefore led to the development of more efficient processes particularly suited to the speedy creation of prototypes – which is how 3D printing first emerged.
 

Taking Prototyping to a New Level

 
With the advent of 3D printing, product designers and engineers have a way to take prototyping to the next level. The technology is toolless (eliminating the need for expensive tooling), well-suited to low-volume production and can produce parts in a much shorter amount of time. This means that prototypes can be produced much faster and more cost-effectively – and since all 3D printed parts originate from digital CAD files, designs can also be updated and tweaked much more easily.
 
Rapid prototyping can also help engineers decide on the final design before going to production, reducing the likelihood of costly mistakes. For example, product designers at Wöhler, a German manufacturer of metrology and inspection technology, recently 3D printed a functional prototype of a Wood Moisture Meter device, with aesthetics close to the final product. The prototype of the device comprised of rigid and flexible components, and had to be made from different materials. For this, the company used Stereolithography (SLA) engineering grade resins to create a durable prototype capable of withstanding functional tests without any damage.
 
Functional prototypes are particularly crucial at the product development stage, providing an opportunity to test the mechanical properties of a final part.

Rapid Prototyping: the 3D Printing Technologies

 
The emergence of 3D printing technologies has taken the notion of prototyping to new heights. Functional prototypes can now be produced in a matter of hours and in a range of plastics and metals, thanks to developments in AM technology.
 
Stereolithography

The emergence of Stereolithography (SLA) in the 1980s marked the start of the rapid prototyping era. The technology uses an ultraviolet laser to cure and solidify ultrathin layers of photopolymer resin, and is a choice for prototypes that require accuracy or smooth surface finish. The first SLA printers were large and unreliable machines, producing models with rough surfaces. Three decades later, however, SLA has evolved into a well-established and cost-effective tool for producing parts with high dimensional accuracy and a smooth surface finish. There are now many offerings of SLA machines on the market, from desktop printers to larger, industrial machines. SLA also offers great material variety, with a wide range of resin materials on offer.
 
While SLA is considered to be one of the fastest 3D printing technologies available, recent advancements in vat polymerisation technologies (to which SLA belongs) have led to the development of potentially quicker processes. One example is Carbon’s Continuous Liquid Interface Production (CLIP) technology. Introduced in 2015, CLIP can be used to create functional prototypes and final parts with mechanical properties, resolution, and surface finishes that are very similar to injection-moulded parts.
 
Selective Laser Sintering
 
Selective Laser Sintering (SLS) is another early 3D printing technology, having emerged in the late 1980s. The process involves the fusing plastic powdered material using a powerful laser. It is most often used in industries like aerospace and medicine, where the material properties of the prototype are critical.
 
Over time, SLS has evolved into a mature manufacturing technology offering a combination of high accuracy, speed, durability and lack of support structures required – which is why it is typically chosen for more complex, functional prototypes. Although the technology could only produce small objects initially, today SLS systems can produce prototypes in a variety of sizes, with some of the larger machines printing parts one metre long or more. A wide range of materials, from nylon and ceramics to various metals, can also be used with SLS, making it a great prototyping option for commercial applications
 

Want to learn more? Download our in-depth white paper on SLS 3D printing here.

SLS systems have historically been more expensive for companies to acquire (costing into the hundreds of thousands of dollars). However, in 2014, the patent for the technology expired, giving rise to more affordable alternatives, such as the Formlabs Fuse 1 benchtop 3D printer.
 
Fused Deposition Modelling
 
Since its emergence on the market by Stratasys in the 1990s, Fused Deposition Modelling (FDM) has become the most commonly used 3D printing technology. This is in part explained by the expiration of several FDM patents in 2009, which has since given rise to a wave of FDM desktop 3D printers at a significantly lower price point – making the technology a great entry point for hobbyists and companies alike. 
 
With FDM, thermoplastic filaments are extruded through onto the printing platform one layer at a time. The range of materials suitable for FDM has also increased significantly: today, manufacturers can choose between thermoplastics with various properties, from elastic TPU to durable and reinforced ABS, to high-performance materials like PEEK, enabling more flexibility in the production of functional prototypes.
 

Full-colour and multi-material prototyping

 
Binder and Material Jetting
 
The emergence of colour and multi-material 3D printing at the start of the 2000s has created exciting opportunities to create prototypes that are an exact replica of the final part.  Binder and Material Jetting are two key technologies increasingly used to create models which can represent the look and feel of a final part. The multi-colour possibilities of these processes also help to streamline post-processing steps such as painting. The main difference between the two technologies is that Binder Jetting uses a binding agent to fuse plastic powders together whereas Material Jetting works by depositing droplets of photocurable resins.
 
With Material Jetting, not only can prototypes with different colours be 3D printed, but also parts that combine different material properties (e.g. flexible and rigid simultaneously). This opens up a lot of opportunities to create models that perform the fit and function of the final part. For example, the J750 3D printer from Stratasys is the latest in the company’s Material Jetting systems. The J750 relies on Stratasys’ proprietary PolyJet technology and offers multicolour and multi-material 3D printing with 6 different materials simultaneously.
 
High-quality colour 3D printing is growing at a rapid pace, particularly with the emergence of HP’s Multi Jet Fusion (MJF) technology, which operates similarly to Binder Jetting. MJF is said to add even more accuracy, colour vibrancy and surface quality to 3D printed parts, producing functional nylon prototypes in as little as a  day. Multi Jet technology can also be used to create injection moulds to produce parts for testing, virtually the same as the final part.
 

Metal prototyping

 
Certain applications, such as within the aerospace and automotive fields, require one-off, functional metal prototypes to validate the performance of a part. Fortunately, 3D printing has made prototyping economical not only with plastics, but with metal too. The combination of reduced material waste, toolless production and greater design freedom has made metal 3D printing an attractive option for prototyping.
 
And developments within metal 3D printing have had implications for the production of functional metal prototypes. Markforged, for example, has its Metal X system, capable of printing metal parts using Metal Injection Moulding (MIM) in a fraction of the time and cost of traditional metal 3D printers.
 
A caveat: using conventional technologies like CNC machining or casting may be preferable when larger quantities are needed, although 3D printing is often the more practical choice for small batches of prototypes with complex internal features.

Where is rapid prototyping used?

 
Medical, automotive, aerospace, consumer goods, you name it – almost every industry vertical is already benefiting from using 3D printing to produce prototypes.
 
Take the automotive sector, for example, where rapid prototyping remains the primary application of additive technology. Car manufacturer Ford has been able to save months in lead time by using 3D printing for prototyping. Ford engineers can use 3D printing to produce several copies of a prototype simultaneously, each with a unique feature. This allows them to perform parallel testing, accelerating and improving parts development. Recently, Ford has embarked on rapid prototyping larger automotive parts. Using Stratasys’ Infinite Build 3D printer, the company plans to develop new, lightweight parts with the goal of improving fuel efficiency.
 
Rapid prototyping through 3D printing is also increasingly used to develop electronics, particularly Printed Circuit Boards (PCB). PHYTEC, a supplier of cutting-edge solutions for the industrial embedded market, turned to Nano Dimension’s DragonFly 2020 3D printer to develop functional circuit boards.
 
The machine uses multi-material 3D printing technology, which deposits conductive inks and can 3D print a PCB in 12 to 18 hours – 10 to 15 times faster than ordering and making PCBs with traditional methods. This allows the company to receive functional prototypes earlier during the development stage, substantially reducing the development cycle time and ultimately improving the quality of the final product.
 

RP and 3D printing – still evolving

3D printing for rapid prototyping has come a long way since the 1980s – and has evolved into a robust manufacturing solution. For companies new to the technology, 3D printing offers an ideal solution for producing reliable, functional prototypes and speeding up the product design and development phase. Key questions will be how to integrate the technology into existing frameworks and processes, to ensure that companies can greater leverage the benefits of digital manufacturing technologies. 
 
Of course, while we’ve taken a look at the evolution of 3D printing for rapid prototyping, the market is also seeing a move towards 3D printing for end parts. Looking ahead, 3D printing will continue its advance towards end production, becoming a flexible manufacturing solution at all stages of development and production.
 

Shares

0

If you want to learn more, please visit our website low-pressure overmoulding advantages.