Fused Deposition Modeling3D Printing Design Guidelines

FDM produces parts up to 36 inches in a single build. Parts larger than the build volume can be printed in sections and assembled.

Fortus 450 (16" x 14" x 16"): ±0.25 mm (±0.010"), or ±0.2%, whichever is greater. Fortus 900 (36" x 24" x 36"): ±0.762 mm (±0.030"), or ±0.5%, whichever is greater.

Standard layer height is 254 microns (0.010″) unless otherwise stated. Industrial FDM machines can print parts with custom layer thickness, in the range of 127 - 330 microns thick. Thicker layers typically result in better adhesion and better mechanical properties.

Parts made with FDM will always show visible layer lines, especially on curved surfaces. However, the visibility of layer lines can be reduced with smaller layer heights at the expense of print speed.

Supported walls are connected to two or more sides and are thick enough to support the model.

Unsupported walls are connected on only one side or edge.

The minimum pin size depends on a combination of parameters such as; part orientation, nozzle diameter, and length of the pin.

Debossed details are recessed features on your model. Making these too small can result in closed gaps and loss of detail.

Embossed details are raised features on your model. These usually resolve better than engraved details. Extruded text should have a wall thickness of at least 1.5mm (0.059") when printed flat, and 2mm (0.079") when printed vertically.

Minimum suggested text size on the top or bottom build plane of a FDM model is 16 point boldface. Minimum suggested text size on vertical walls is 10 point bold.

Clearance is the distance between two moving parts on hinges, joints, mating parts, etc.

For a tight press fit, add a small offset, and chamfer the leading edge to ease entry. Always print an initial test part to dial in dimensions.

This defines the minimum allowed gap between a bush and a bolt, to avoid bonding of the hinge parts.

Depending on orientation, circular holes can resolve as ovals – if higher accuracy is required, printing the hole smaller and then drilling it out is recommended.

Gaps or slots can fuse if made too narrow, and support material may be difficult to remove. If possible, orient gaps along the xy-plane for highest accuracy.

Hollow features may be filled with soluble support material, and must be designed with drain holes so that the support can be dissolved and removed during cleaning. Larger parts or parts with complex internal features may require larger holes to allow support material to fully dissolve.

Fillets can be used to reduce stress concentrations and increase the strength of your part. When designing fillet features across inside and outside corners, it is best to have them share a common center point in order to maintain a consistent wall thickness.

Bosses and ribs are an effective way to add strength and stiffness to a part while keeping material consumption to a minimum, this can also reduce build time and use less support material.

A separate support material is used to hold the part up during building. All materials aside from ULTEM use soluble support material that is dissolved, leaving no imperfections on the surface of the part. Support for ULTEM has to be manually removed and can leave some minor scratches on parts.

Infills are used in FDM printing to save material and print time while maintaining the overall mechanical properties of the part. Parts will be printed solid unless otherwise specified. 'Sparse fill' prints large volumes with a honeycomb structure instead of solid plastic.

Very large threads can be printed, but most threads do not perform well in FDM. The use of inserts is recommended.

Design parts with holes sized for tapping, or center marks for drilling a pre-tapped hole. Tapping removes material, puts pressure on the surrounding geometry, and fastener locations are often points of stress, so make sure there is enough material surrounding the tapped hole.

Threaded inserts can be glued in, or heated and pressed in. Heat set inserts require a soldering iron with an installation tip, which softens the plastic walls, allowing the insert to be pushed into the hole or boss before the plastic hardens around the insert.

Parts too big to fit on the print tray can be split in CAD and printed in multiple parts, then glued or press fit. Use joinery features, such as tongue and groove, to ensure the sections are aligned and bond tightly.

Parts can be machined to tighter tolerances using traditional or CNC subtractive manufacturing equipment.

Parts can be sanded, primed, and painted for an excellent surface finish. Parts can also be coated with a lacquer, varnish or clear coat for various custom finishes.

Vapor smoothing uses acetone vapor to increase plasticity of the material allowing it to flow, smoothing layer lines. With enough exposure, the resulting finish can be uniform and glossy, although this comes at the expense of dimensional accuracy. This is only applicable to ABS and ASA materials.