1.6 FUSED DEPOSITION MODELLING (FDM)

 

• Developed by Scott Crump, and Stratasys has been selling the machine since 1991.

 

• The concept is that material is heated and then in controlled quantities deposited directly on previous layers. Eventually layers are built up to complete the entire part.

 

• The materials are available on spools of 1/2 mile in length, at costs from $175(US) to $260(US). The filaments are 0.05”

 

• As usual the .STL file is sliced into layers, and the slices are used to drive the machine.

 

• The key to this method is an extrusion head,

- the material is fed into the head

- the material is heated until melting

- the material is then extruded from the tip in controlled quantities

- the material is wiped on the previous layer

 

• The extrusion head is moved about the table with an x-y positioning system to deposit material on each layer

 

• The platform the part is on drops when a layer is complete to allow the addition of a new layer.

 

 

 

• materials include

investment casting wax

ABS

polyester

elastomer

 

• slice thickness is 0.002” to 0.03”

 

• material changeover requires a few minutes of “flushing-out’

 

• Advantages,

- a good variety of materials available

- easy material change

- low maintenance costs

- thin parts produced fast

- tolerance of +/- 0.005” overall

- no supervision required

- no toxic materials

- very compact size

- low temperature operation.

 

• Disadvantages,

- seam line between layers

- the extrusion head must continue moving, or else material bumps up

- supports may be required

- part strength is weak perpendicular to build axis.

- more area in slices requires longer build times

- temperature fluctuations during production could lead to delamination

 

• selected specifications for the FDM1000 are,

 

 

• Approximate costs are,