Rapid Prototyping

Direct Metal Laser Sintering (DMLS) does for metals what other RP processes have done for
plastics, but takes it further with generally better tolerances and truly production worthy
end-materials.

DMLS builds parts from powdered metal in thin layers (20 microns/.0008 inches) with walls as thin as 0.2 mm (.008 Inches) and typical tolerances of ±.001 inch/inch. 

A broad range of materials are available to meet a variety of real-world application requirements.

Materials include: 17-4 Stainless Steel, Direct Metal 20 (bronze alloy), Direct Steel H20 (tool
steel), Cobalt Chrome, Maraging Steel.

DMLS is best suited for small complex parts (including internal passages typical of aero investment castings). The maximum build envelope is 250 mm x 250 mm x 215 mm (9.85
in. x 9.85 in. x 8.5 in.)

The combination of materials, tolerances and feature definition available with DMLS combined
with the ability to build parts with internal passages and other geometric complexities open
up a wide variety of applications for DMLS including:

• Prototypes, short-run production, individualized products, spare parts
• Parts requiring high corrosion resistance such as medical instruments or prototype implants
• Parts requiring high toughness or ductility
• Parts requiring hardness including tooling and fixtures.
• Injection mold and casting die inserts, including conformal cooling.
• Prototypes of metal cast parts, particularly those that will require ceramic core dies for
internal passages (typical of blades and vanes, and fuel system components)

www.vaupell.com

::Design World::

Source: :: Make Parts Fast ::

San Mateo, Calif. – Luxology® LLC announces the immediate availability of “MP3 Player: Rapid Visualization and Prototyping,” a new video album that demonstrates how modo® 302’s robust toolset can be used to complement and enhance the product design process. Created by Luxology’s Training Division Director, Andy Brown, this training series offers step-by-step instruction on rapidly giving form to design concepts using Subdivision surfaces in modo. The video album also covers the process of preparing a model for 3D printing and creation of final presentation images. For more information or to purchase, please visit http://www.luxology.com/store/training_series12.aspx.

Product visualization and design requires continuous revision and Brown’s latest tutorial series demonstrates how modo can be used effectively at the ideation phase of the design process. With a portable MP3 player as the subject matter, this three-part video series covers the following topics: Sketching in 3D, Subdivision Surface Modeling for Rapid Prototyping, and Adding Colors and Context. A physical prototype of the MP3 player was produced using a Z Corp 3D printer during the development of this video album.

Luxology’s Training Division was formed over a year ago in an effort to answer the growing demand for high-quality learning materials for both novice and experienced 3D modo artists. Since its formation, there has been a continual flow of professional quality training materials on a variety of real-world topics. A typical video album from Luxology is priced at USD $25 and provides approximately 90 minutes of instruction and sample content. Each video is downloadable for immediate viewing and is formatted for playback on Mac and PC systems.

www.luxology.com

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Building a wall out of bricks and creating a plastic part out of plastic layers are both additive processes. As such, they share several advantages. Both are relatively simple, inexpensive, and repetitive—brick is piled on brick; plastic layer is laid upon plastic layer to form the finished product. But additive processes have limitations as well. One of the most significant is weakness at the joints.

Drive a truck into a brick wall. While the bricks may survive, the wall will give way at the mortar joints. Similarly, if you stress a layered plastic prototype it will tend to fracture along its layers. Brick walls are rarely struck by trucks, but plastic prototypes represent production parts that will almost certainly be subjected to a variety of stresses. If the prototype cannot withstand the same stresses as the production part (which will almost certainly come out of an injection mold as a solid resin) the prototype cannot be used for meaningful functional testing. 

An alternative is to replace the additive process with one of two subtractive processes. The first of these is a primary subtractive process: machining a prototype out of a solid block of resin, which will have similar characteristics to solid molded resin. The other is a secondary subtractive process: milling an aluminum mold and injecting resin to produce a prototype with characteristics very similar to those of a production part coming from a steel mold. If these subtractive processes can be made as fast and economical as additive processes like Stereolithography and Fused Deposition Modeling, they will be competitive with the additive processes.

Besides eliminating the layering of additive processes, subtractive processes have several other advantages. They support a range of resins, which allows prototype models to be matched for strength, flexibility, chemical resistance, dielectric properties, and other critical characteristics. Most additive processes focus on a couple of resins.

Subtractive processes also offer a variety of surface finishes, doing away with the “stepped” surfaces often found in many additive processes. This can be functionally important if parts must slide and cosmetically important if the prototypes are to be used in market testing.

Automation is the key to making subtractive prototyping competitive with the additive methods. But while additive automation was a simple matter of “slicing” a CAD model into layers that could be laid one-on-another, subtractive processes faced the more complex chore of turning a CAD model into tool paths for milling machinery. At Proto Labs, a large-scale compute cluster and proprietary software allow CNC machining equipment and mold milling machinery to do just that. As a result they can compete with additive processes for both speed and economy.

www.protolabs.com

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Every manufactured product is the sum of its parts, whether off-the-shelf or
custom made. Custom parts developed with Rapid Prototyping and
Internet-based technologies
actually contribute more value to a complete manufactured product.

Custom parts play a huge, yet
rarely discussed role in the manufacturing industry. Whether
custom-made, purpose designed, or off-the-shelf, parts for manufactured
products create a ripple that affects almost everyone around the world.
Parts generate revenue to sustain business, business sustains
employees, employees sustain communities, communities sustain
governments, and governments sustain other governments that, we hope,
sustain a workable world in which we are all
interdependent.

This brings us back to the
perspective that parts are the center of the universe. Harnessing the
“power of the part” provides a smarter approach to develop and control
the costs associated with designing and manufacturing parts. Rapid
prototyping is the emerging technology that brings manufacturing into
this twenty-first century.

There are a number of rapid
prototyping (RP) technologies available today that let manufacturers
save time and money before they ever consider mass manufacturing.
Stereolithography (SLA), Selective Laser Sintering (SLS) and Fused
Deposition Modeling (FDM) are the most popular.

Prototyping parts quickly
achieves cost savings in both lead-time and quality.
Every day that a part is not ready for installation is a day that money
is not made. Prototypes can be done in as little as 2 days. Plus, you
can run tests on the parts depending on their material properties.

Manufacturers are able to test for fit, form and function to ensure
that quality
parts go into the finished product. Testing also eliminates the risk
that a large order arrives only to be found out of spec, of inferior
quality, or that they simply don’t fit the application. With
prototyping technologies, product developers ensure that the parts they
need will be correct the first time and on time. Savings are generated
immediately!

In addition, Web-Based
Instant Online Quoting eliminates days or weeks of waiting on quotes
for critical parts. This new technology revolutionizes the world of
product development, accelerating the quote, assuring product managers
that critical parts will arrive in the time required and that they will
meet and exceed quality
standards. Since time equals money, imagine the money saved simply by
getting your quotes online, instantly!

With the latest Rapid
Prototyping processes and Instant Online Quoting, product development
communities will shorten the lifecycle of the manufacturing process,
delivering top-quality products to the market faster, better and easier
than ever before.

www.quickparts.com

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Rapid Prototyping (RP) or rapid manufacturing is the automatic construction of physical objects using solid freeform fabrication.
The first techniques for rapid prototyping became available about 20
years ago 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 takes virtual designs from CAD software,
transforms them into thin, virtual, horizontal cross-sections and then
creates each cross section in physical space, one after the other,
until the model is finished.

Additive Fabrication (AF) is
the technique of building a part by laying down successive thin layers
of material. With additive fabrication, the machine reads in data from
a CAD model and lays down successive layers of liquid, powder, or sheet
material, and in this way
builds up the model from a series of cross sections.

Desktop manufacturing or personal fabrication
is the use of a personal computer to drive a printer that deposits (or
catalyses) material in layers to form three-dimensional objects. It can
be used for making prototypes or objects that have limited public
demand.

Direct Digital Manufacturing is
a manufacturing process that produces physical parts directly from 3D
CAD files or data using additive fabrication techniques, also called 3D printing or rapid prototyping. The 3D printed parts are intended to be used as the final product itself with minimal post-processing.

Electron Beam Melting (EBM) is
a type of rapid prototyping for metal parts. It is often classified as
a rapid manufacturing method. The technology manufactures parts by
melting metal powder, layer per layer, with an electron beam in a high
vacuum. Unlike some metal-sintering techniques, the parts are fully
solid, void-free and extremely
strong.

Fused Deposition Modeling (FDM) is
a type of rapid prototyping or rapid manufacturing technology marketed
commercially by Stratasys Inc. Like most other RP processes, FDMworks
on an “additive” principle by laying down material in layers.

Laminated Object Manufacturing (LOMTM) is
a rapid prototyping system developed by Helisys Inc. In it, layers of
adhesive-coated paper are successively glued together and cut to shape
with a laser cutter.

Low-Volume Injection Molding creates
functional parts from thermoplastics in short runs of up to 50,000
parts. Offers similar quality and accuracy to parts produced by normal
production tooling, but often faster and at lower cost.

Low-Volume Layered Manufacturing
describes additive fabrication in which the object constructed is the
actual end-use part for manufacturing, rather than a prototype or
model. Sometimes viewed as another term for direct digital manufacturing.

Photopolymer is a polymer that is cured by exposure to light, often in the ultraviolet spectrum.

Selective Laser Sintering(SLS) is
a process by which 3D SLS prototypes are formed by fusing or sintering
powdered thermoplastic materials or metals to form functional
prototypes. A claimed advantage to SLS is the range of materials that
can be used, including nylon, elastomers, metals (steel, titanium,
alloy mixtures, and composites) and green sand.

Solid Freeform Fabrication (SFF) is
a group of related techniques for manufacturing solid objects by the
sequential delivery of energy and/or material to specified points in
space to produce that solid.

Stereolithography (SL) is
an additive process using a vat of liquid UV-curable photopolymer
“resin” and a UV laser to build parts a layer at a time. On each layer,
the laser beam traces a part cross-section pattern on the surface of
the liquid resin. Exposure to the UV
laser light cures (solidifies) the pattern traced on the resin and
adheres it to the layer below.

STL File is the
standard data interface between CAD software and a prototyping machine.
An STL file approximates the shape of a part or assembly using
triangular facets. Tiny facets produce a higher quality surface.

Subtractive Fabrication is
akin to conventional manufacturing techniques like machining, in which
a part is shaped by removing or subtracting material from a piece of
stock. The term
“subtractive fabrication” is intended to differentiate those processes
from those of additive manufacturing so widely used in rapid
prototyping.

3D Printing is the practice of making a solid (3D) part using an automated additive process.

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Rapid prototyping (RP) is a critical link in today’s fast-paced design cycle and is a cost-effective way to shorten product development from concept to production. The RP process builds concept models to verify new designs for form, fit, and function, which often includes aggressive testing. Such prototype model testing considerably shortens time to market and eliminates costly design errors. Both the manufacturers of RP equipment and the materials suppliers are constantly upgrading the capabilities of their products to give engineers more robust models and new ways to deliver products on time and on budget.

Of the two major ingredients of the RP process—machines and materials—the materials have been perhaps the most challenging area for engineers and chemists to develop. A major material limitation lies in the strength of the prototype parts to withstand real-world loads, as it would in actual service. Clearly, this is an area that requires constant research and improvement.

The Machines

Stereolithography (SLA), Selective Laser Sintering (SLS), Fused Deposition Modeling (FDM), and 3D Printing currently are the four major rapid prototyping technologies. SLA, the most widely used process, employs a laser beam to solidify layers of liquid resin. The SLS process also uses a laser to sinter layers of powdered material. In contrast, FDM machines build models by extruding layers of production-type material on top of one another. The 3D printers “print” a water-based adhesive delivered by the print head on layers of mixed plaster and resin, which bonds them in accordance with the CAD cross-section pattern. All four technologies are considered additive, since the prototype is built by adding material, as opposed to subtractive processes, such as machining where the material is removed.

The Materials

Compared to the SLS and FDM processes, the SLA has the fastest turn-around time and produces parts with highest accuracy and the smoothest surface finish. On the other hand, when a prototype needs to have production-part-like structural durability, the SLS and FDM processes have an advantage since they use materials with about 80% the strength of actual production parts.

Because stereolithography is an extremely accurate, stable, and repeatable technology SLA parts are well suited for form and fit verification. However, engineers often were hesitant to conduct high impact functional tests since SLA parts were rather fragile. But this limitation is becoming much less of a factor.

The advancements in modern chemistry and formulation processes allow the development of new resins known in the industry as mimics. These SLA materials closely mimic the properties of various engineering plastics. For example, if the production part will be made of ABS or polypropylene, engineers can choose prototypes made from the ABS-like or polypropylene-like SLA resins. The prototype will have mechanical properties closely matching the properties of the production injection-molded parts and can be used for functional tests, including high pressure and high temperature. So, the complete form, fit, and function verification can be done using one SLA prototype.

Modern SLA machines can process a complete portfolio of stereolithography materials to address various needs of engineers. Service bureaus greatly increase their efficiency from the use of newer machines that come with rapid delivery modules, which allow quick changeover of materials. The shortened set-up time reduces the cost and overall turn-around time.

The Prototype Model

The type of the stereolithography machine mostly determines the feature resolution and the maximum size of the part. The selection of the SLA resin however is the deciding factor when reviewing options based on how the prototype will be finished, used, handled, and tested. SLA resins available today imitate the physical properties of engineering thermoplastics such as Acrylonitrile Butadiene Styrene (ABS), polycarbonate, and polypropylene. For example, an ABS-like resin will produce as close a match to the production ABS part as possible within the SLA technology.

Often translucent or clear parts are highly desirable during the concept development, functional verification, and approval phases of the project. Previously, machining and polishing were traditional methods of fabricating optically clear prototypes from polycarbonate and acrylic. Later, translucent resins became available for rapid prototyping. But early parts were formed semi-clear or became cloudy quickly. They had a greenish or bluish tint. The completely clear SLA resins became available only in the last three years.

If exposed to light for a long time, parts made from clear SLA resins experience slight clarity degradation. For the majority of parts this degradation poses no problem, because the parts are usually discarded after design verification or concept presentation. The loss of clarity can be minimized by coating or sealing parts if the optical property has to remain constant for longer periods of time.

Optically clear parts open new possibilities for designers. Some parts, such as lenses, see-through shields, retail packaging, and medical devices are made of clear plastic in production, and clear SLA parts allow building prototypes that look exactly like the real product. They can be used for marketing presentations, focus groups, shows, and concept reviews.

Building architectural models of clear materials greatly simplifies the architect’s job. Until the transparent enclosures let machine designers see how parts of various mechanisms moved inside an enclosure, they had to make holes in order to peek inside.

Abe Reichental, the President and CEO of 3D Systems, gives an example of one company that had a transmission housing made of clear SLA resin. They populated it with the gear train and gaskets, filled it with transmission fluid, and ran the prototype to study the fluid dynamics in various modes. Another 3D customer uses clear rapid prototypes to test engine blocks. They ran the crank shaft with an electric motor and conducted various tests to study the motion and fluid dynamics inside the case. Now engineers had a full view of the entire engine.

Another example of flow analysis where clear SLA parts allows visual study is in pumps. A common pump design problem is called cavitation, the generation of a void or the formation of bubbles in the liquid. Pump housings made of clear material gives engineers an unobstructed view inside the pump so that even the smallest areas of cavitation can be spotted.

Building light-transmitting parts places additional requirements on the clarity and finish of the models. Clear SLA parts are successfully used to build prototypes of automotive instrumentation displays, lenses, head lights, and tail lights. Light guides, pipes, pointers, and diffusers are just some examples where machining acrylic or polycarbonate gave way to clear SLA process.

Clear materials are typically geared toward a specific rapid prototyping technology. For example, clear resins available for use in stereolithography systems are not compatible with the SLS or FDM equipment.

Several translucent ABS-like SLA resins are currently available, and several clear resins were recently added to the engineer’s RP toolbox. Previously, clear resins usually involved durability tradeoffs. Newer, clear resins no longer have these trade-offs. Just five years ago translucent materials were rather fragile and could not be used for high impact, high pressure, or high-temperature tests. Newer, much tougher resins were developed to address this problem.

New translucent and clear SL resins such as RenShape® SL 7870 made by Huntsman, Accura® 60 made by 3D Systems, and WaterShed® XC, as well as WaterClear®Ultra produced by Somos are only a few examples.

Carl Holt, Commercial Sales Manager for NAFTA for Stereolithography of Huntsman Advanced Materials, explains that his company specializes in the formulation of ready-to-use SLA resins and offers approximately 30 SLA resins for various applications. Huntsman clear materials are high-clarity photopolymers; they are neither a polycarbonate nor an acrylic.

Huntsman’s RenShape SL7870 is a high clarity resin that also has extremely high impact strength. Another benefit of this material is that it does not age as rapidly over time as many other earlier clear resins. Huntsman also produces a UV-blocking coating (primer) to protect the clear parts from sun damage.

Clear resin manufacturers typically publish standard sets of ASTM information on their Web sites. Since new materials are constantly added to the portfolios (although not all service bureaus include them in their line), it is always a good idea to check with the resin manufacturers to find out what new materials became available recently and which service bureaus are capable of processing them.

The process for building clear parts involves the same steps as when using other SLA resins, except some additional steps are required at the end. A 3D CAD solid model is required to generate an SLA prototype. All 3D modeling software packages are capable of exporting a file known as an “.STL” file (which stands for Standard Tessellation Language). For standard clear finish the support structures are removed, while the support areas and the exterior surfaces are wet sanded. Sanding the part reduces clarity, so a clear coat is then applied to create a smooth, clear surface. The higher-grade clear finish requires deeper wet sanding to remove the build layer staircasing and create smooth surfaces. The clear coat is also applied and can take 12 hours to completely dry.

The cost of an SLA part depends on part height, volume, total part surface area, and layer resolution. The cost of resin selected for the part and required finish are also important factors. In the case of clear parts, clear resins are relatively expensive, but the largest cost factors are the extra finishing and drying required to produce clear parts without blemishes.

3D Systems
www.3dsystems.com

Huntsman

www.huntsman.com

Somos

www.dsmsomos.com

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How the RP Machine Works

In a typical process for making RP models, the CAD file is loaded into the SLA machine’s computer where a proprietary software program “slices” the 3D model into layers spaced the distance equal to the thickness of the resin that will be cured during the processing of one layer (for example 0.005” thick).

The liquid-clear material is placed into a vat at the bottom of the stereolithography machine and a platform, upon which the part will be built, is positioned just below the liquid resin surface. The platform depth equals to the thickness of the layer. The machine guides a laser along the surface of the resin to expose the liquid according to the pattern in the slice. The laser beam cures the liquid resin that it lights upon. Once the first layer is completed, the platform is lowered so the next layer can be built on top of the first layer. The process repeats until all layers are built. After that the part is taken out and placed under UV light for final curing.

A bridge-type support structure is built at the start of the SLA process to keep the bottom of the part off the platform and to support the bottom curved surfaces of the part. Without these thin columns, the initial layers, only few thousands of an inch thick, would sag and prevent the next layer from being built. The support structure is removed after the part is completed and cured.

Several finishing levels are typically offered by SLA service bureaus. The most basic finishing level includes just removing the support structure. The next, standard level adds light sanding of support areas and exterior surfaces and sand blasting. For parts where surface flatness is important, the part is sanded smooth to remove the build layer stairstepping caused by layering. When the SLA part is intended for mold making or to be painted, the interior walls are also sanded and the part receives a coat of primer. 

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Manufacturing by the removal of material may be among the oldest of human endeavors. In fact, the Stone Age takes its name from the process of chipping away unwanted rock to yield useful tools. Obviously, that process was completely manual. Even though it has become far more sophisticated, machining has continued to be labor-intensive and therefore challenging to use in the manufacture of prototypes.

By the late 20th century, manual drafting had given way to computers and CAD software, and manual machining had evolved into computer numeric controlled (CNC) machining. But between those automated processes, there remained two very labor-intensive steps. The first of these was reviewing the design from an engineering standpoint and determining a price quote. The other was the conversion of the model from its original paper or electronic form to the machine code (toolpaths) that instruct the CNC machining equipment in the production of the finished part.

Both of these were time-consuming, painstaking processes that could cost hundreds or thousands of dollars and take days of trained professionals’ time, even with the use of high-end computer aided manufacturing (CAM) software tools. The cost and delay could be tolerated, if grudgingly, when a large number of copies were needed. But they made it difficult or impossible to justify the use of the CNC machining process to produce a small number of prototypes. That was particularly unfortunate for the plastics industry, since machined prototypes, being made from blocks of engineering grade resins, could do an excellent job of representing injection molded parts for the functional testing required during product development.

Of course, developers still had the option of using non-CNC machining, but that, too, was costly and slow. Instead, they turned to the emerging technologies of additive rapid prototyping (RP), which used software to control the process of layering plastic materials to produce a physical facsimile directly from the 3D CAD model. But while the additive rapid prototyping processes were fast and inexpensive, they could only use a small number of resins, and they produced parts with rough surfaces and reduced material properties due to the layering process. This was a distinct disadvantage compared to the solid construction and wide variety of resins available using CNC machining, but prototype parts could be obtained quickly via additive RP, so it was seen as a reasonable tradeoff.

The obvious answer was to computerize toolpath generation for CNC machining, but this required more sophisticated software and an enormous amount of processing power. First Cut Prototype, a division of Proto Labs, Inc., has developed software that runs on a high-speed 1.9 teraflop compute cluster that can generate toolpaths in minutes instead of days, all without the need for CAM programmers.

This system supports the automated preparation of FirstQuote® web-based quotations, on-line ordering, and the manufacture of CNC-machined “subtractive RP” parts in as little as one business day, essentially providing all of the advantages of additive RP processes without the associated limitations.

The end result is that, today, subtractive RP can produce “injection molding equivalent” prototypes even faster than additive RP processes can produce prototypes of lesser quality, so there is simply no reason to settle for less.

www.protolabs.com

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MEADVILLE, PA — C&J Industries now offers customers the ability to see their design and sample parts in just a few hours thanks to stereolithography, or SLA, a rapid printing process used to create three-dimensional objects from CAD drawings.

The Eden 250 ultra-thin printing system is capable of producing a prototypical plastic part using even the most precise technical specifications to produce a 3D sample of the final product. For customers, that means quicker design time, decreased cost, and the opportunity to bring their injection molding product to the market in record time.

The prototype may not be made of the same material as the final product will be, but it allows customers to see it, touch it, and experience it in 3D to be sure it’s the direction they want to go in before full production.

“What’s important is that we can turn a CAD idea into a physical object – a sample part – quickly, without going through the entire production cycle. So the prototype can then be tested for proper form and fit, and with some materials the customer can even be sure that the final piece will function as originally intended,” said C&J Industries Director of Engineering, Eric Sharman.

Because there is no need to go through the longer process of building an injection mold that would be the final piece, customers can assess where the part’s design may need adjustment to function as intended.

Sharman is quick to point out that other plastic injection molding companies may offer one or the other: either rapid prototyping or full production, but not both.

www.cjindustries.com

::Design World::

Source: :: Make Parts Fast ::