發布日期：2022-04-18 點擊率：107
3D printing, as practiced today, originated in the 1970s and 1980s from research into photopolymer materials that harden on exposure to light, and the development of additive processes such as Stereo Lithography (SLA) and Fused Deposition Modeling (FDM). SLA uses a laser to etch shapes in liquid-phase photopolymers, whereas FDM uses extrusion techniques to deposit layers of plastic on a print bed. More recently, Selective Laser Sintering (SLS) has been developed, which uses similar techniques to SLA but with powders instead of photopolymer.
In low volumes, 3D printing is a relatively fast and cost-effective means of producing parts to high quality standards, avoiding the high tooling costs associated with traditional molding, die casting or stamping processes. As an additive manufacturing process, 3D printing also contrasts with subtractive processes such as machining. Printing generates significantly less waste material, and it is possible to produce complex shapes that are difficult to achieve using conventional techniques.
In addition to supporting printing with plastics, ongoing development of the major 3D printing processes and others such as electron beam melting and laminated object manufacturing, allows the use of metals such as aluminum, stainless steel or titanium, as well as ceramic materials. Moreover, assemblies can now be produced using dissimilar materials in a single, efficient, seamless process. This enables the production of parts with built-in electrical traces, for example, making it possible to envision processes that embed electronic devices directly into the printed part as it is being produced.
Commercially available desktop 3D printers are popular for rapid prototyping and development work. Whether the printing is outsourced to a specialist contractor, or done in-house, the fact that development engineers can generate a CAD model, and from it derive a file that can be sent to the printer, shared, replicated, and stored for future use, or discarded with minimal loss of investment, gives great flexibility, allows more production-like mechanical samples and prototypes, and saves tooling costs.
As the variety of materials that can be processed has expanded, 3D printing is becoming increasingly relevant as a means of making parts for use in end products. Although unlikely to replace traditional molding or casting techniques for making simple parts in high volumes, low volume complex or high value components can be produced quickly and cost effectively.
3D printing also simplifies lifetime product support and maintenance. OEMs no longer need to manufacture and stock spare parts in advance as they can simply use their stored files to produce parts on demand. Perhaps one of the most extreme examples is the 3D printer on-board the International Space Station (ISS). Using this printer, teams aboard the ISS can make replacement parts as required from a small stock of raw materials, eliminating carrying a large inventory of parts on board, or having to wait for replacements. The ISS printer is also being used for research into manufacturing engineered products in zero gravity conditions.
As the cost of basic desktop printers continues to fall, and process and materials knowhow advances, the appeal of 3D printing continues to grow throughout the “makerverse” and professional engineering communities. According to Allied Market Research, which has forecast a Compound Annual Growth Rate (CAGR) of 21% from 2015-2020, 3D printing will turn into an $8.6 billion industry. The consumer and aerospace sectors will be the largest adopters, followed by defense, education, automotive and industrial. In the consumer sector, 3D printing can be used for anything from small figurines and toys to enclosures and more complex parts, taking advantage of the tool-free nature of additive manufacturing to reduce costs and accelerate new product introduction.
In aerospace, component manufacturers and builders of planes and satellites are interested not only in the potential for cost savings at relatively low volumes, but also in the potential for saving weight while at the same time producing stronger parts. In commercial airliners, saving weight translates into fuel savings for aircraft operators. By studying the design of parts made using traditional methods, new, lighter weight versions of components ranging from simple cabin brackets and handles to more complex load bearing parts can be created. Performing stress analysis on existing designs has shown the locations where parts need to be as strong or stronger than their predecessors, and can also identify areas where excess material is not needed.
Using traditional production methods, excess material must usually be removed using a machining process which creates waste. Airbus has previously commented that it can reduce the weight of some parts by as much as 55% using 3D printing, while reducing raw material usage by 90%. The company recently released images of a new prototype air nozzle for use with a new cabin climate control system that allows larger overhead lockers (Figure 1). 3D printing enabled the project to be completed more quickly and cost-effectively than using conventional techniques.
Figure 1: Airbus’ application of innovative 3D printing technology led to creation of a prototype air nozzle for the A330neo. (Photo credit: Airbus)
Besides the ISS 3D printing project, NASA has completed several additive manufacturing projects on earth, including the production of rocket engine nozzles using selective laser melting with over 8000 layers of copper alloy powder (Figure 2). This is part of a program aimed at manufacturing engine parts up to ten times faster than other techniques, and at less than half the price.
Figure 2: NASA’s 3D-printed rocket-engine nozzle features intricate channels in the upper rim for circulating liquid hydrogen coolant.
As OEMs continue to grapple with challenges such as shorter product lifecycles, demands for faster time to market, lower unit cost, more product variants and customization options, 3D printing may offer an efficient and affordable solution. In factories of the future, 3D printing could move inline, ready to produce individual parts in real-time. This can bring several benefits such as independence from external suppliers, thereby giving greater control over deliveries and less potential for delays. Designs can also be changed quickly without financial penalties or waste of any investment in inventory or tooling. With a 3D printer in the line, small variations in a common design can be accommodated easily, simply by changing the printing file.
Scalability is another advantage for companies that have built 3D printing into their production flow. If production capacity needs to be expanded, extra 3D printers can be sourced. Outsourcing a 3D printing job to a third-party producer is another option, which can be easily accomplished by electronically sharing the appropriate CAD data or ready-to-use printer file.
To take advantage of these opportunities, companies need the expertise to design suitable components for 3D printing that optimally utilize the available processes. One way for engineers to familiarize themselves with 3D printing and start making usable components is to invest in an affordable desktop 3D printer such as the DFRobot Dream Maker Overlord Classic BL.
Working from a 3D CAD model of the part to be printed in a standard file format such as .stl or .obj, the 3D model is effectively reduced to layers for the Overlord Classic BL to build up one at a time. The printer comes with open source slicing software called Cura, along with some printing examples loaded on an SD card.
Figure 3: An optimal orientation for printing minimizes overhanging material.
The Cura software generates a .gcode file containing the layer-by-layer coordinates for printing the part. The user has to set the correct size for the component, and some engineering judgment is needed to determine the optimum orientation for producing the part (Figure 3). Cura then guides the user to choose the preferred settings for producing the part (Figure 4). These choices include the print quality, the material to be used, and the infill density.
Figure 4: Cura guides the user through basic and advanced settings governing the printing process.
Some parts may require supports to be provided to prevent overhanging structures from distorting while the plastic is hardening. Since supports add to the cost and time to generate the part, optimum component design for 3D printing and a judicious choice of build orientation can help minimize their use.
3D printing has developed quickly in recent years to present an accessible and agile means of producing prototype parts quickly and cost effectively. Compared with subtractive manufacturing techniques, waste material can be greatly reduced. 3D printing can create shapes that are difficult or expensive to produce using conventional methods, and lightweight parts can be produced that are capable of withstanding high stresses.
In the future, 3D printers could be used in high-speed inline manufacturing, presenting an efficient means of producing parts just in time to satisfy demands, or to simplify supply chain management when building products in small batches. Production can also be scaled or transferred to another line easily by distributing the appropriate CAD or .gcode file. The latest desktop printers enable engineers to acquire experience with this fast-growing technology with minimal investment.
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