3.5 Rapid Prototyping

The growth in computing power has had a major impact on modelling with computer-aided manufacture. Rapid software and hardware developments allow new opportunities and exciting new technologies to create dynamic modelling of ever-greater complexity. Models can be simulated by designers using software, tested and trialled virtually before sending to a variety of peripheral machines for prototype manufacture in an ever-increasing range of materials. The ease of sending this digital data across continents for manufacture of prototypes has major implications for data and design protection.

The increasing effectiveness of rapid prototyping techniques in terms of both cost and speed enables designers to create complex physical models for testing.

Rapid Prototyping (RP) and RP Machines
  • entails a machine that produces a complete product including internal details, at a fairly quick rate.
  • reduce product development time as prototypes are quickly made and can be tested
  • one-off products are made for different or specialised  situations
  • is an additive manufacturing technique as opossum to subtractive manufacturing (mills, lathes, etc).
    • less waste (good for environment and save money)

Explain a situation in which it would be advantageous to use subtractive or additive manufacturing when making a product.

RP Process
  • Using CAD software produce a full scale model
  • Export or convert model in STL (Standard Triangle Language and Standard Tessellation Language).
  • send to RP machine
  • manufacture the item
  • clean up the item
Stereolithography

Stereolithography (SLA) is a 3D printing process.

  • that uses a vat of photosensitive resin and a vertically moving platform.
  • It uses a laser beam, directed onto the surface of the photosensitive resin, to print the pattern of the current model layer by hardening the photosensitive resin.
  • The platform then moves down by a layer thickness so the next layer can be printed.
  • Also known as optical fabrication, photo-solidification, solid free-form fabrication and solid imaging.
  • Used for producing models & prototypes, casting patterns,  production parts and products.

Laminated object manufacturing (LOM)
  • LOM machines take the sliced CAD data from the 3D model and cut out each layer from a roll of material, using a laser or plotter cutter. These sliced layers are glued together to form the model, which is either built on a movable platform below the machine or on pins when using card. (IB TSM 2015)
  • A rapid prototyping systems that creates a 3D product by manufacture (LOM) converting it into slices, cutting the slices out and joining the slices together

Fused deposition modelling (FDM)

An FDM machine is

  • A heated extrusion nozzle (extruder) that moves through the x & y axis
  • A plastic (such as ABS, PLA), metal or composite (such as30% metal,  bamboo, etc  fill PLA) filament is fed through he extruder
  • basically a CNC robot that holds a small extrusion head. The extrusion head moves back and forth along a platform, building up a 3D model by feeding heated plastic wire through the extrusion head.
  • Either the platform or extruder move through the Z axis place a layer if build material
  • Controlled by CAM software.

Selective laser sintering (SLS)

SLS is a 3D printing process based on sintering.

  • A high powered CO2 laser is used to sinter a thin layer of heat-fusible powder that gradually builds up the 3D model.
  • Powders include, plastic, metal, ceramics and glass

Types of 3D printing (RP) techniques
  • Describe different design contexts where SLS, LOM and FDM would be applicable.- Consider quality, cost and accuracy of outcome.
Advantages and disadvantages of rapid prototyping techniques
Advantage Disadvantage
 Product design
  •  More intricate
  • many prototypes can be quickly and accurately produced
  • prototypes can be used in user trials
Time/Speed
  •  reduced design development time
  • changes to ideas can be quickly done
  • Slow process -have to build internal structure, supports and raft.
  • Slower that other CAM techniques – e.g. CNC routing, laser cutting, etc
Cost
  • reduce design development costs
  • reduce costly mistakes
  • initial capital cost can be high
Accuracy
  •  increased complexity of designs
  • parts produced with finer tolerances
  • can produce intricate designs better other CAM processes
Waste
  • No or minimal waste – it is additive manufacturing. Other CAM techniques a subtractive.
Volume production
  • not suitable as it is slow. Other cam techniques would be better suited for volume.
  • this can be due to the need to build the internal structure.
 Materials
  •  A wide range of materials can be used.
  • Advantage over other CAM processes which are limited in their material use.
Communication
  • improved with the client, designer  and the manufacturer
  • changes to ideas can be easily communicated
Size
  • limited to size of the bed or work area – may result in numerous parts (sub assemblies)
  • not suited for large scale applications
Sample Questions:
  • Explain the benefits of being able to rapid prototype a product instead of using other CAM techniques. – Consider product design, speed, time, costs, accuracy and waste.
  • Compare SLS, LOM and FDM rapid prototype processes. – Consider speed, time, costs, accuracy and surface finish.
  • Discuss the limitations of rapid prototyping for volume-produced products. – Consider the internal structure of a product, and number of components.
  • Discuss how rapid prototyping (RP) benefits trials, testing and final part manufacture. – Consider reduced development time and costs, and user trials.
International-mindedness:

The high cost of some new processes does not allow for their rapid dissemination globally.

Theory of knowledge:

Which ways of knowing do we use to interpret indirect evidence gathered through the use of technology?

Something Extra

Some 3D printing Links

Design Tech for IB students