During the past years the demand for functional models and small series of production parts was constantly growing and Fused Deposition Modeling technology exceedingly matches all the present-day requirements. It is a tremendously successful technology.
History
FDM was developed by Scott Crump, and the machines are being sold since 1991
The concept
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.
Preparation Process
Fused Deposition Modeling materials 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" ABS - this is the standard modeling material and produces parts which are both stable and durable. It is the white material most associated with a FDM model. Realize that hand finishing will likely be required for many parts depending on intended use. For many, however, a part straight from the machine is entirely suitable. Please see Craig or a TA for finishing instructions. Among aditional materials that are available on the FDM machines there are investment casting wax, elastomer, polyester and others. |
- STL file of a model is imported into a pre-processing software.
- This model is being oriented and slices mathematically into horizontal layers varying from 0.1 - 0.2 millimeters 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 X, Y and Z axes are operated when drawing the model in FDM Software one layer at a time.
Fused Deposition Modeling (FDM)
In brevi, ABS (FDM material) feeds into the temperature-controlled FDM extrusion head, where it is heated to a semi-liquid state. The head extrudes and deposits the material in thin layers onto a fixtureless base. The head directs the material into place with precision, as each layer is extruded, it bonds to the previous layer and solidifies. The designed object emerges as a solid three-dimensional part without the need for tooling.
Fused Deposition Modeling technology advantages and disadvantages
During the Fused Deposition Modeling process three-dimensional objects are constructed directly from 3D CAD data. A thermoplastic material is extruded by temperature-controlled head layer by layer.
| FDM Advantages | FDM Disadvantages |
| 1. A good variety of materials available | 1. Seam line between layers |
| 2. Easy material change | 2. The extrusion head must continue moving, or else material bumps up |
| 3. Low maintenance costs | 3. Supports may be required |
| 4. Thin parts produced fast | 4. Part strength is weak perpendicular to build axis |
| 5. Tolerance of +/- 0.005" overall | 5. More area in slices requires longer build times |
| 6. No supervision required | 6. More area in slices requires longer build times |
| 7. No toxic materials | 7. Temperature fluctuations during production could lead to delamination |
| 8. Very compact size | |
| 9. Low temperature operation |
FDM Flow
The system operates in X, Y and Z axes, drawing the model one layer at a time. This process is similar to how a hot glue gun extrudes melted beads of glue. The temperature-controlled extrusion head is fed with thermoplastic modeling material that is heated to a semi-liquid state. The head extrudes and directs the material with precision in ultrathin layers onto a fixtureless base. The result of the solidified material laminating to the preceding layer is a plastic 3D model built up one strand at a time.
Concluding, the key of FDM 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
Finishing
Material changeover requires a few minutes of "flushing-out". Once the part is completed the support columns are removed and the surface is finished.
