4.2. CAD Output Devices - Rapid Prototyping

4.2. CAD Output Devices-Rapid Prototyping

Assoc.Dr. Ahmet Zafer Şenalpe-mail: [email protected]

Mechanical Engineering DepartmentGebze Technical University

ME 521Computer Aided Design

mailto:[email protected]

Rapid Prototyping

It is the technology that using CAD models physical models are obtained directly. For this purpose rapid prototyping devices are used. Although rapid prototyping devices vary in its group their principles are the same. In this method physical models are formed by adding materials layer by layer. Rapid Prototyping (RP) brings solutions to the problems faced during product development period.Possible design mistakes can easily be identified. Before the mass production, prototype has to be prepared and several tests have to be conducted on these prototypes. This period may take a long time when conducted with conventional methods. With RP this period is shortened and prototypes can be tested both visually and functionally. Possible design changes can be decided on these prototypes and necessary changes can easily be made. Prototypes can be used for die manufacturing.

4.2. CAD Output DevicesRapid Prototyping

Dr. Ahmet Zafer Şenalp ME 521 2Mechanical Engineering Department,

GTU

Rapid Prototyping

Where are the parts produced by RP used?

After visual inspection possible shape mistakes can be identified. For products that contain more than one part perfect assembly conditions (ex: alignment) can be checked. Mechanism functionality can be tested.An assembly with a lot of parts can be manufactured and run at one time. Prototypes can be used for die manufacturing .Prototype models can be used of precise casting.


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Rapid Prototyping

What kind of parts can be produced by RP?

There is even no limitation to the parts that can be produced by RP. As the parts can easily be bonded to each other, the size of the part is not a problem.

Die production can also be made with RP.


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Rapid Prototyping

How much time is needed for RP?

Hours!... Time needed for RP depends on complexity and volume of the part. The delivery time is about 4-5 days after ordering. In special cases the period can be short as 1 day or long as 10 days.


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Rapid Prototyping

Is RP expensive?

RP can be seen as expensive with the additional cost . However with RP the work that could be concluded in weeks can be finished in hours.

Product defects can be detected earlier and much more expensive corrections can be avoided. With these advantages apparent cost for RP is less than the savings made by using RP.

The RP cost of products depends on factors like product size, volume and geometry.Real cost of products should be determined after conducting necessary analysis.


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Rapid Prototyping

Rapid Prototyping Technologies:

PolyjetFDM: Fused Deposition ModelingSLS: Selective Laser SinteringSLA: StereolithographyLOM: Laminated Object ManufacturingEBM: Electron Beam Melting 3-D Printing


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Polyjet

In this technique, photo-polymer material in liquid form at room temperature is sprayed from spray nozzles of eight injection heads with thousands of injection spray nozzles which cause the formation of layers (similar to plastic injection machines).

The sprayed material is freezed and solidified by using ultraviolet lamps.16 micron thickness layers are formed one by one and prototype is obtained.

As the model can not stop hanging in the air, the gaps are filled with support material with the same injection method. This support material then dissolves in water and the model is obtained.

The materials used in this technology are photo-polymer resins which are specific to this method. Physical and chemical properties differ from each other.


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Polyjet

...... STL file is opened in the software and model is placed on the system’s table and the file is send to the Polyjet from the software.

Polyjet system sprays the model and support material according to the instructions send by the software.

After each layer sprayed material is applied ultraviolet rays for solidification.

Model is constructed in 16 micron thickness layers. Then water spay is used to remove support material from the model and prototype is obtained.


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Polyjet

Polyjet Matrix


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Polyjet

Polyjet Product Examples:

FullCure 720

Tango : TangoBlack & TangoGray


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Polyjet

Polyjet Product Examples:

Tango plus

Vero : VeroBlue, VeroWhite, VeroBlack


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FDM: Fused Deposition Modeling

Fused deposition modeling (FDM) is an additive manufacturing technology commonly used for modeling, prototyping, and production applications. The technology was developed by S. Scott Crump in the late 1980s and was commercialized in 1990.

The FDM fused deposition model process is additive which extrudes material in layers. A plastic filament is melted and extruded through a heated nozzle. The nozzle moves to produce a profile of the part then moves down and the next layer is built on top until the entire prototype model is fully built. The model is complete and requires no hardening. FDM is an excellent choice for any 3D Model that needs to closely represent the final product in strength and durability. CAD Models can be produced in about 24 hours depending on the size and complexity. Online price quotes are available for FDM parts..

FDM requires support during the Prototype Model building process and can increase the build time.

Several materials are available with different trade-offs between strength and temperature properties. As well as acrylonitrile butadiene styrene (ABS) polymer, polycarbonates, polycaprolactone, polyphenylsulfones and waxes. A "water-soluble" material can be used for making temporary supports while manufacturing is in progress, this soluble support material is quickly dissolved with specialized mechanical agitation equipment utilizing a precisely heated sodium hydroxide solution..


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http://en.wikipedia.org/wiki/S._Scott_Crump

http://en.wikipedia.org/wiki/Acrylonitrile_butadiene_styrene

http://en.wikipedia.org/wiki/Acrylonitrile_butadiene_styrene

http://en.wikipedia.org/wiki/Polycarbonate

http://en.wikipedia.org/wiki/Polycaprolactone

http://en.wikipedia.org/wiki/Polyphenylsulfone

http://en.wikipedia.org/wiki/Sodium_hydroxide



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FDM Product Examples:


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SLS: Selective Laser Sintering

Laser Sintering is also a technique by which parts are built layer by layer. The basic material consists of powder with particle sizes in the order of magnitude of 50 µm. Successive powder layers are spread on top of each other. After deposition, a computer controlled CO2 laser beam scans the surface and selectively binds together the powder particles of the corresponding cross section of the product. During laser exposure, the powder temperature rises above the glass transition point after which adjacent particles flow together. This process is called sintering.

After production of the part is completed powders that function as support material are cleaaned by a brush.

The material those are used in this technology arePolyamide,Ploystrene and several metal alloys.


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SLS Working Principle:

In sintering powder material is left under the melting temperature of the material so that powders stick to each other.

4 phases of sintering can be seen in the above figure.


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Best application areas of SLS technology Mechanical and thermal test parts Plastic parts Large complex functional parts Casting parts Functional modelsSLS Advantages Products are resistant to shape and functional tests Parts can be assembled with mechanic or chemical methods No need to use support material Parts are cleaner than other methods Heat treatment or painting can be applied on the partsThe materials used plastic, metal or ceramic powders can be used, as well as their mixtures consisting of composite powders are also available. Glass fiber reinforced plastic powders or plastic-coated metal powders are examples to this.

In the case of metal usage the method is called as Direct Metal Laser Sintering (DMLS).


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SLS Product Examples:


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SLS AdvantagesSLS polyamide (nylon) material enables full functional prototype production. Glass-filled nylon is resistant to high temperature and chemical environments in the prototype production. Rubber like parts can be manufactured directly from polymer. This is for seals and sealing elements that are exposed to high temperature.

For durable metal parts and molded parts P20 steel which is similar to St 200 can be used.

SLS Disadvantages

The surface finish of SLS parts are not good as SLA parts but additional surface finish can be applied.

High shrinkage ratios can result torsion, bending or dimensional inaccuracy.

SLS feature details are not precise as in SLA.


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SLA: Stereolithography

Stereolithography is an additive manufacturing 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, or, solidifies the pattern traced on the resin and adheres it to the layer below.

After a pattern has been traced, the SLA's elevator platform descends by a single layer thickness, typically 0.05 mm to 0.15 mm (0.002" to 0.006"). Then, a resin-filled blade sweeps across the part cross section, re-coating it with fresh material. On this new liquid surface, the subsequent layer pattern is traced, adhering to the previous layer. A complete 3-D part is formed by this process. After building, parts are cleaned of excess resin by immersion in a chemical bath and then cured in a UV oven.

Stereolithography requires the use of support structures to attach the part to the elevator platform and to prevent certain geometry from not only deflecting due to gravity, but to also accurately hold the 2-D cross sections in place such that they resist lateral pressure from the re-coater blade. Supports are generated automatically during the preparation of 3-D CAD models for use on the stereolithography machine, although they may be manipulated manually. Supports must be removed from the finished product manually; this is not true for all rapid prototyping technologies.


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http://en.wikipedia.org/wiki/Ultraviolet

http://en.wikipedia.org/wiki/Curing_(chemistry)

http://en.wikipedia.org/wiki/Photopolymer

http://en.wikipedia.org/wiki/Resin


http://en.wikipedia.org/wiki/Laser


http://en.wikipedia.org/wiki/Laser


http://en.wikipedia.org/wiki/Three-dimensional_space



http://en.wikipedia.org/wiki/Computer_Aided_Design

http://en.wikipedia.org/wiki/Rapid_prototyping



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SLA Part Examples:


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LOM:Laminated Object Manufacturing

Laminated object manufacturing (LOM) is a rapid prototyping system developed by Helisys Inc. In it, layers of adhesive-coated paper, plastic, or metal laminates are successively glued together and cut to shape with a knife or laser cutter.

The process is performed as follows:1. Sheet is adhered to a substrate with a heated

roller.2. Laser traces desired dimensions of prototype.3. Laser cross hatches non-part area to facilitate

waste removal.4. Platform with completed layer moves down out

of the way.5. Fresh sheet of material is rolled into position.6. Platform moves up into position to receive next

layer.7. The process is repeated.


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http://en.wikipedia.org/wiki/Rapid_prototyping

http://en.wikipedia.org/wiki/Paper

http://en.wikipedia.org/wiki/Plastic

http://en.wikipedia.org/wiki/Metal

http://en.wikipedia.org/wiki/Laser_cutter


Advantages

Low cost due to readily available raw material Relatively large parts may be made, because no chemical reaction is necessary Fast as laser only traces the contour and does not trace the whole cross section. Parts can be used immediately after processing. There is no need for Additional processing. No need for additional support. It is easy to use.

Disadvantages

The most common used material is still paper. The materials on any other specified is currently underway.

As parts are easily to accommodate to humidity finishing should be applied with a special Epoxy based material (Lompoxy: generated for LOM usage).

Production of complex parts are difficult. There may be fire problem when the working zone gets too hot.


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LOM Part Examples:


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http://www.wtec.org/loyola/rp/fh11_12.jpg



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EBM:Electron Beam Melting

Electron beam melting (EBM) is a type of additive manufacturing for metal parts. 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 dense, void-free, and extremely strong.

The vacuum environment in the EBM machine maintains the chemical composition of the material and provides an excellent environment for building parts with reactive materials such as titanium alloys. The electron beam’s high power ensures a high rate of deposition and an even temperature distribution within the part, which gives a fully melted metal with excellent mechanical and physical properties. .


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http://en.wikipedia.org/wiki/Additive_manufacturing

http://en.wikipedia.org/wiki/Sintering


Part surface quality is very good compared to other RP methods. Can be applicable to metals, materials apart from metals, ceramics and composite

materials. EBM is successful in small and parts with precise regions. Can drill holes with one or two nanometer precision. More precise than metal cutting operations. The part can directly be used after the operation. No need for extra heat treatment SLS,LSM,DMLS needs heat treatment. Due to high energy and scanning method EBM is very fast. Minimum layer thickness: 0.05 mm Tolerance: +/-0,4 mm. Very successful in titanium alloys. Applied to medical implants, aerospace/automotive parts successfully. In this method parts are produced within hours.


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EBM application with Ti6AI4V material


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Advantages

Obtaining high energy with narrow beam. The quality of the vacuum melting enables high material properties. Vacuum environment avoids oxide and nitride based impurities. Enables welding of unlike metals that are hard to process. Comparison with SLS:

Due to efficient beam formation power consumption is low Maintenance and installation costs are lower It has high power and speed Bending of the beam is obtained without moving the part which results high speed and

low maintenance.

Disadvantages

Vacuum requirement means additional cost. Emits gamma rays during operation (Vacuum tanks should be designed to protect

rays) Materials should have electric conductive property.


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EBM Part Examples:


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3D Printing

Developed in MIT (Massachusetts Institute of Technology). 3D parts is produced layer by layer. 3D printers are generally fast and have low costs. One version of 3D printing includes inkjet printing system. Fine dust material (plaster, resin) is sprayed from the printer and adhesive is then used for

bonding. This technology enables the production of fully colorful prototypes.


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3-D Printing


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3-D Printing

3-D Printing Part Examples:


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Rapid Prototyping

RP Technology comrarison

(lower grade is better)


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4.2. CAD Output Devices - Rapid Prototyping

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