Rapid Prototyping

Rapid prototyping machine

Shaft holder made by rapid prototyping

Medical device made by rapid prototyping

Rapid prototyping covers a variety of processes that, typically, produce low quantities of parts without tooling so that fast turnaround is possible. eMachineShop offers FDM Fused Deposition Modeling which uses a heated nozzle to extrude plastic having a 0.01" diameter onto a work piece. In this type of rapid prototyping, fused plastic is deposited layer by layer according to the 3D model.

Rapid prototyping developed as an outgrowth of liquid photopolymer research, a class of plastics that solidify under high intensity ultraviolet laser light. Early rapid prototyping, RP for short, was created in units called SLA's or stereolithography apparatus. Fused Deposition Modeling is a newer approach that opened up a wider range of materials including polycarbonates, ABS plastics, and others.

Rapid prototyping offers low cost for short runs since no tooling is required. Rapid prototyping allows engineers, designers, managers and end users to check designs for usability, appearance, manufacturability, fit, function, etc., prior to committing to conventional manufacturing. RP speeds the design cycle.

Rapid prototyping can produce almost any 2D or 3D shape including shapes that cannot be made using conventional machining. Examples of a few applications include:

• Enclosures
• Brackets
• Toy Parts
• Mechanisms
• Shape models
• etc.
  

No physical tooling is needed for rapid prototyping.

• Reducing the weight of the final part
• Using proper part orientation. For example building a cup oriented in the normal way is more economical that building a cup oriented upside down.

Rapid Prototyping Design Considerations

• Since the extrusion is .010", it is best to keep dimensions in multiples of this value - especially smaller dimensions, walls and air gaps.
  
• Tolerance: X, Y: .005" + 0.1%; Z: .010 + 0.1%.
  
• Min wall: .030" for horizontal walls (e.g. bottom of box); .040" for vertical walls with no holes or cutouts; .1" for vertical walls with holes and slots in sides; .020" for very low walls that form letters/logos.
  
• Min acute angle: 30 deg.
  
• Min diameter of holes in side of part: 0.25".
  
• Min height of horizontal slots in side of part: 0.25".
  
• Min material between hole and edge or between holes: .04" ideally, .02" absolute min and can create problems.
  
• Max size: 8" x 8" x 12".
  
• Long thin objects (max dim / min dim > 10) can't be longer than 8".
  
• Since parts are formed via a ~0.01" diameter plastic extrusion, the material will be slightly porous and therefore is not appropriate for containers of gases or liquids; the surface will be rougher than a machined part; and there are often small gaps, usually at intricate or curved features.
  
• Intricate features, such as small lettering are not recommended due to the .01" extrusion quantization.
• To thread holes, use Line | Machine | Thread.