CAD Techniques

8/2/2019 CAD Techniques

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Equipment Name:

Fused Deposition Modelling (FDM)

Working Principle:

The Fused Deposition Modelling (FDM) process constructs three-dimensional objects directly from 3D

CAD data. A temperature-controlled head extrudes thermoplastic material layer by layer.

The FDM process starts with importing an STL file of a model into a pre-processing software. This model

is oriented and mathematically sliced into horizontal layers varying from +/- 0.127 - 0.254 mm thickness.

A support structure is created where needed, based on the part's position and geometry. After

reviewing the path data and generating the toolpaths, the data is downloaded to the FDM machine. The

system operates in X, Y and Z axes, drawing the model one layer at a time. Once the part is completed

the support columns are removed and the surface is finished.

Sketch:

Specifications: ( FDM3000 by Stratasys(R))

Specifications Value

Build Size 10”x10”x16”

Achievable Accuracy ±0.005”

Modeling Material ABS (Acrylonitrile-Butadiene-Styrene polymer), ABSi (medical

grade), Investment casting wax elastomer etc...




Layer Thickness 0.007” to 0.014”

Equipment Name:

Stereolithography (SLA)

Working Principle:

Stereolithography (SLA), the first Rapid Prototyping process, was developed by 3D Systems of Valencia,

California, USA, founded in 1986. A vat of photosensitive resin contains a vertically-moving platform.

The part under construction is supported by the platform that moves downward by a layer thickness

(typically about 0.1 mm / 0.004 inches) for each layer. A laser beam traces out the shape of each layer

and hardens the photosensitive resin.

Sketch:



Specefication: (ViperTM

SLA(R)

System by 3D Systems)


Build Size 10”x10”x10” (Larger machines can build parts up to

20”x20”x24”.)

Achievable Accuracy ±0.0001”

Modeling Material Accura SI 40, photo-sensitive resin

Layer Thickness 0.002" to 0.006"

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 powderlayers 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 crosssection 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.

Laser Sintering: Technical specifications

Standard lead time:

Minimum of 4 working days, depending on part size, number of components and finishingdegrees.

Minimum of 2 working days for smaller parts.



Standard accuracy:

± 0.3% (with lower limit on ± 0.3 mm)

Minimum wall thickness:

1 mm, but living hinges are possible at 0.3 mm

Maximum part dimensions:

Dimensions are unlimited as components may be composed of several sub-parts. The build areaof the largest machine is 700x380x580mm.

Surface structure:

The parts typically have a grainy surface but all kinds of (very) fine finishing are possible. Theycan be sandblasted, coloured (impregnated), painted, covered, coated, …



Laminated Object Manufacturing

Working Principle:

1. Layer fabrication starts with sheet being adhered to substrate with the

heated roller.2. The laser then traces out the outline of the layer.3. Non-part areas are cross-hatched to facilitate removal of waste material.4. Once the laser cutting is complete, the platform moves down and out of the

way so that fresh sheet material can be rolled into position.5. Once new material is in position, the platform moves back up to one layer

below its previous position.

6. The process can now be repeated.

Sketches



Specifications:

Machine LOM 2030E

Manufacturer Helisys (Cubic Technologies)

Material Paper

Mechanism CO2 Laser, Heated Roller

Build Volume 20" x 30" x 20"

Applications Produces large prototypes for visualization and assembly testing.

http://www.cubictechnologies.com/






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CAD Techniques