Rapid Prototyping & Manufacturing Technologies

Rapid Prototyping & Manufacturing Technologies

In many fields, there is great uncertainty as to whether a new design will actually do what is desired. New designs often have unexpected problems. A prototype is often used as part of the product design process to allow engineers and designers the ability to explore design alternatives, test theories and confirm performance prior to starting production of a new product. Engineers use their experience to tailor the prototype according to the specific unknowns still present in the intended design.

Introduction

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Rapid Prototyping technology employs various engineering e.g. computer control and software techniques including laser, optical scanning, photosensitive polymers, material extrusion and deposition, powder metallurgy etc. to directly produce a physical model layer by layer (Layer Manufacturing) in accordance with the geometrical data delivered from a 3D CAD model.Definition

Differences between conventional machining and rapid prototyping

Prototyping can improve the quality of requirements and specifications provided to developers.

Reduced time and costs:

Users are actively involved in the development.

Quicker user feedback is available leading to better solutions.

Errors can be detected much earlier.

Missing functionality can be identified easily.

WHY Rapid prototyping?

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High precision RP machines are still expensive.

RP systems are difficult to build parts with accuracy under +/- 0.02mm and wall thickness under 0.5mm.

The physical properties of the RP parts are normally inferior to those samples that made in proper materials and by the traditional tooling.

The RP parts are not comparable to (CNC) prototype parts in the surface finishing, strength, elasticity, reflective index and other material physical properties.Limitations of Rapid prototyping

All RP techniques employ the basic five-steps processes:

Create a CAD model of the design.

Convert the CAD model to STL format.

Slice the STL file into thin cross-sectional layers.

Construct the model one layer atop another.

Clean and finish the model.

Workflow of RP processes

Surface/Solid modelGenerate STL fileBuild supports if neededSlicingBuild prototypeRemove supportsClean the surfacePost curePart completedCAD modelPre processRP processPost processWorkflow of RP processes

First, the object to be built is modeled using a Computer-Aided Design (CAD) software package.

Solid modelers, such as Pro/ENGINEER, tend to represent 3-D objects more accurately than wire-frame modelers such as AutoCAD, and will therefore yield better results.

This process is identical for all of the RP build techniques.

1. CAD Model Creation

To establish consistency, the STL format has been adopted as the standard of the rapid prototyping industry.

The second step, therefore, is to convert the CAD file into STL format. This format represents a three-dimensional surface as an assembly of planar triangles

STL files use planar elements, they cannot represent curved surfaces exactly. Increasing the number of triangles improves the approximation

2. Conversion to STL Format

Example of STL modelThis figure shows a typical example of STL model which is composed of triangles and each triangle is described by a unit normal vector direction and three points representing the vertices of the triangle.

In the third step, a pre-processing program prepares the STL file to be built.

The pre-processing software slices the STL model into a number of layers from 0.01 mm to 0.7 mm thick, depending on the build technique.

The program may also generate an auxiliary structure to support the model during the build. Supports are useful for delicate features such as overhangs, internal cavities, and thin-walled sections.

3. Slice the STL File

Desired part or model geometry

Without supports, overhanging areas of part may peel away and damage the whole model

The fourth step is the actual construction of the part.

RP machines build one layer at a time from polymers, paper, or powdered metal.

Most machines are fairly autonomous, needing little human intervention.

4. Layer by Layer Construction

The final step is post-processing. This involves removing the prototype from the machine and detaching any supports.

Some photosensitive materials need to be fully cured before use

Prototypes may also require minor cleaning and surface treatment.

Sanding, sealing, and/or painting the model will improve its appearance and durability.

5. Clean and Finish

Types of Rapid Prototyping TechnologiesSLA --- Stereolithography

SLS --- Selective Laser Sintering

LOM --- Laminated Object Manufacturing

FDM --- Fused Deposition Modeling

3DP --- Three Dimensional Printing

Patented in 1986, Stereolithography started the rapid prototyping revolution. The technique builds three-dimensional models from liquid photosensitive polymers that solidify when exposed to ultraviolet light.

1. Stereolithography (SLA)

Schematic diagram of Stereolithography process

Laser concentrative UV beam to transom liquid into solid state.Elevator control the movement of platform upward and downward Platform a steel plate with plenty of holes as the basement for part buildingResin vat contain raw material to form SLA modelMirrors control the path of movement of the laser beam at X and Y axisSensor locate the coordinate and instant power of the laser beam and feedback to the control unit for fine adjustment

Mirrors sensorBasic components of SLA system

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2. Selective Laser Sintering (SLS)

AdvantagesFlexibility of materials usedPVC, Nylon, Sand for building sand casting cores, metal and investment casting wax.No need to create a structure to support the partParts do not require any post curing except when ceramic is used.

DisadvantagesDuring solidification, additional powder may be hardened at the border line.The roughness is most visible when parts contain sloping (stepped) surfaces.

Application Range

Visual Representation modelsFunctional and tough prototypescast metal parts

As the name implies the process laminates thin sheets of film (paper or plastic).

The laser has only to cut/scan the periphery of each layer.

3. Laminated Object Manufacture (LOM)

The process

The build material (paper with a thermo-setting resin glue on its under side) is stretched from a supply roller across an anvil or platform to a take- up roller on the other side.

A heated roller passes over the paper bonding it to the platform or previous layer.

A laser, focused to penetrate through one thickness of paper cuts the profile of that layer. The excess paper around and inside the model is etched into small squares to facilitate its removal.

The process continued:The process of gluing and cutting continuous layer by layer until the model is complete.

To reduce the build time, double or even triple layers are cut at one time which increases the size of the steps on curved surfaces and the post processing necessary to smooth those surfaces.

Advantages

Wide range of materialsFast Build timeHigh accuracyLOM objects are durable, multilayered structures which can be machined, sanded, polished, coated and painted

Application Range

Used as precise patterns for secondary tooling processes such as rubber molding, sand casting and direct investment casting. Medical sector for making instruments.

4. Fused Deposition Modeling (FDM)

FDM 2000 Specifications

Prodigy Specifications Build Volume: 10" x 10" x 10" Materials: ABS, Casting Wax Build Step Size: 0.005" to 0.030"

Build Volume: 8" x 8" x 10" Materials: ABS, Casting Wax Build Step Size: 0.007", 0.010", 0.013" Up to 4x faster than the FDM 2000

(FDM) is a solid-based rapid prototyping method that extrudes material, layer-by-layer, to build a model.

A thread of plastic is fed into an extrusion head, where it is heated into a semi-liquid state and extruded through a very small hole onto the previous layer of material.

Support material is also laid down in a similar manner.

Advantages

Easy fabrication Minimal wastageEase of removalEasy handling

Application Range

DesigningEngineering analysis and planningTooling and manufacturing

How Rapid Prototyping Technologies Compare?

What is 3DP?3DP is the process of creating an object using a machine that puts down material layer by layer in three dimensions until the desired object is formed. A 3D printer extrudes melted plastic filament or other material, building objects based on specifications that come from modeling software or from a scan of an existing object. 5. Three Dimensional Printing (3DP)

To create something with a 3D printer, a user begins either by scanning an existing object with a 3D scanner to obtain the needed specifications or by generating the specs in a 3D modeling application. The specifications are then sent to an extrusion printer, where plastic filament or other material is used to create the three-dimensional model one layer at a time.

As the material is extruded from the nozzle of the printer, the software controlling the machine moves either the platform or the nozzle itself such that the material is deposited in a succession of layers to create the object. Often, the completed object is a single color, but printers are now available with two nozzles for dual-color prints. Printing can take a few minutes for a small object the size of a keychain or several hours for larger, more complicated objects.

How does 3D printing work?

3D Printed technology is being used by some of the most modern manufacturers to develop prototypes and products going through testing phase. This has increased the efficiency of product development. These 3D printing innovations are saving; time, money and resulting in higher profit margins.

3D printing technology is gaining in popularity, becoming more competitive, and increasingly affordable. A lot of businesses and industries are benefiting. Those employing the new technology include manufacturers, print advertisers, and commercial marketing firms who are reaching out to clients with new brilliant ideas.

Why 3D printing?

Some of the most exciting global businesses are already expanding possibilities by using 3D printers. Coca-Colacreated miniature statuesof consumers to promote smaller Coke bottles. Some of the other companies experimenting with the technology areNokia,Volkswagen, andeBay. In retail, saySelfridgesandHarvey Nicholsin UK,Le Bon Marchin France, to name a few.

Biscuits and chocolatescan now be 3D printed. It will be very interesting forfood-related businessesto see what their marketers and printers are actually capable of with no holds barred. Now companies can produce any design of biscuit with extreme detailing. Since the technology is still very new and modern, many will be attracted by the amazing designs and logo printing. This makes these giveaways useful free samples at trade shows.

While initially 3D printing was primarily a technology for prototyping, this is quickly changing. Now numerous manufacturers are producing end-use components and entire products via additive manufacturing. From the aerospace industry, to medical modeling and implantation, to prototyping of all kinds, 3D printing is being used by virtually every major industry on the planet in one way or another.

3D printing applications

3D printed models of human organs have been a frequent tool for surgeons over the last two to three years, as they provide a more intricate view of the issues at hand. Instead of relying on 2D and 3D images on a computer screen or a printout, surgeons can actually touch and feel physical replicas of the patients organs, bone structures, or whatever else they are about to work on.Additionally, there is research underway by companies likeOrgan logyto 3D print partial human organs such as the liver and kidney.

Medical

Injured skull

3D bio printing, is a powerful fabrication technology, used to create three-dimensional cellular constructs which bio mimics complex biological functionalities found in native tissues and organs.

The bio printing manufacturing technology combined with smart biomaterials, stem cells, growth and differentiation factors, and biomimetic environments have created unique opportunities to fabricate tissues in the laboratory from combinations of engineered extracellular matrices (scaffolds), cells, and biologically active molecules.

Medical: 3D Bio-Printers

BeforeAfter3D printing face operation

Actually, 3D printed drugs have a lot of advantages to regularly manufactured ones. Its much easier to control density of a 3D printed drug, and design how porous it should be, which means that how quickly it dissolves is much for flexible, and therefore, designers can print a pill that can be dissolved with one sip of water. Additionally, they can add more of the active ingredient, all while making the actual pill much smaller.3D printed drugs

Another general early adopter of Rapid Prototyping technologies, the earliest incarnation of 3D printing, was the automotive sector. Many automotive companies particularly at the cutting edge of motor sport and F1 have followed a similar trajectory to the aerospace companies. First (and still) using the technologies for prototyping applications, but developing and adapting their manufacturing processes to incorporate the benefits of improved materials and end results for automotive parts.

Many automotive companies are now also looking at the potential of 3D printing to fulfill after sales functions in terms of production of spare/replacement parts, on demand, rather than holding huge inventories.Automotive

3D printed car

3D printed babies

3D printed art kids

3D printed eagle beak

3D printed guns

3D Printed jet engine

Architectural models have long been a staple application of 3D printing processes, for producing accurate demonstration models of an architects vision. 3D printing offers a relatively fast, easy and economically viable method of producing detailed models directly from 3D CAD, BIM or other digital data that architects use. Many successful architectural firms, now commonly use 3D printing (in house or as a service) as a critical part of their workflow for increased innovation and improved communication.

Architecture

Related technology development began in the 1960s, with pumped concrete and isocyanine foams.

Building printingrefers to various technology that use3D printingas a way to construct buildings. Potential advantages of this process include quicker construction, lower labor costs, and less waste produced. 3D printing at a large scale may be well suited for construction of extraterrestrial structures on theMoonor other planets where environmental conditions are less conducive to human labor-intensive building practices.Developments in additive manufacturing technologies have included attempts to make 3D printers capable of producingstructural buildings.Related technology development began in the 1960s, with pumped concrete and isocyanine foams.

Architecture: 3D printed concrete houses

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