Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001

65.6 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,

  1. - the material is fed into the head
  2. - the material is heated until melting
  3. - the material is then extruded from the tip in controlled quantities
  4. - 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

  1. investment casting wax
  2. ABS
  3. polyester
  4. elastomer

 

· slice thickness is 0.002" to 0.03"

 

· material changeover requires a few minutes of "flushing-out'

 

· Advantages,

  1. - a good variety of materials available
  2. - easy material change
  3. - low maintenance costs
  4. - thin parts produced fast
  5. - tolerance of +/- 0.005" overall
  6. - no supervision required
  7. - no toxic materials
  8. - very compact size
  9. - low temperature operation.

 

· Disadvantages,

  1. - seam line between layers
  2. - the extrusion head must continue moving, or else material bumps up
  3. - supports may be required
  4. - part strength is weak perpendicular to build axis.
  5. - more area in slices requires longer build times
  6. - temperature fluctuations during production could lead to delamination

 

· selected specifications for the FDM1000 are,

 

 

· Approximate costs are,