The MTC has two rapid prototyping
machines which output models for all kinds of applications. The two
machines available at the MTC are the FDM (Fuse Deposition Modeler)
which outputs plastic prototypes and the LOM (Laminated Object Manufacturing)
machine which outputs paper-based prototypes. The following pictures
are examples of some of the successful uses of Rapid Protoyping at Memorial.
They demonstrate the capabilities of these modelers (click on thumbnail
for brief description). Also, see below for additional information about
Rapid Prototyping Technology.
began with Artists/Craftspeople creating hand-made models. Next was the
evolution of CAD software. This lead to CAD databases being used to generate
CNC programs. Following subtractive processes was the development of additive
processes ... generally called “Rapid Prototyping”.
Goals of Rapid Prototyping
Rapid prototyping allows for the creation of models at greater speeds and with more precision. With rapid prototyping the design process is improved as designers can experiment with variations of a product until the best results are obtained.
Rapid prototyping can:
First of all to proceed with rapid prototyping a geometric model is required which must include surface information. The model is usually created in a solid modeling system such as CATIA, I-DEAS, Pro/Engineer, Unigraphics II. Surface models require completely bound volume and internal detail.
3D geometric models are mathematically sectioned into parallel cross-sections. Each cross-section creates a 2D binding or curing path for model construction. Models are constructed one layer at a time until complete. Supports may also be required.
There are two
stages to rapid prototyping:
(1) Data Preparation:
The CAD data must be converted to .STL format. This format was designed for 3D Systems Inc. Stereolithography Apparatus (SLA). It is characterized by triangular facets that are used to describe the shape of a closed 3D model. Faceted surfaces must be completely bound. In addition, curved surfaces are approximated.
The .STL Format was developed by Albert Consulting Group. It consists of x, y & z coordinates of triangles. All adjacent triangles must share two vertices.
Translation software is either included in the CAD packages or via third party. The translator should provide the ability to adjust chordal deviation (ie. trade-off accuracy vs file size and processing time).
Virtual Reality Modeling Language (VRML) versus .STL should also be taken into consideration at this point. VRML was developed through Silicon Graphics using their Open Inventor (.iv) standard. This lead to “Tele-Manufacturing” as proposed by Michael Bailey, U. of C., San Diego. It takes advantage of greater development effort and utilizes other features (e.g.. colour, colour gradient,texture).
(2) Model production:
Rapid prototyping production technologies include the Stereolithography Apparatus presented at Autofact show in November, 1987. There are currently upwards of twenty different technologies being developed/marketed. There are major differences in materials used and build techniques within these technologies.
Here are a list of various RP technologies:
- Component is built in vat of liquid resin.
- Vat size limits prototype
- SLA-190 (7.9 x 7.9 x 9.8”) US$105,000
SLA-250 (10 x 10 x 10”) US$210,000
SLA-250 (20 x 20 x 24”) US$420,000
- There are five materials currently available for the SLA. All are acrylates (non-reusable thermosets).
- Accuracy - ranges from 0.1% to 0.5% of overall dimension from small to large parts.
- Currently the most accurate RP technology.
- Curing stability and support structures remain challenges.
- Solider 5600 (20 x 14 x 20”) US$550,000
- machine dimensions 13.5’ x 5.5’ x 5’
- layer thicknesses of .004-.006”
- dimensional accuracy of 0.02”, building up to 100 layers/hour.
- Full cure as built minimizes shrinkage and eliminates post-curing.
- Wax eliminates need for supports.
- Fly cutter provides for “undo” operation.
- System produces a lot of waste; Can’t reuse material picked up during milling; and uncured resin is a hazardous material.
- Utilizes powder, rather that liquid polymer.
- Potential exists for different materials including polycarbonate, PVC, ABS, nylon, polyester, polyurethane and casting wax.
- Sinterstation 2000 (12” dia. x 15” dp) US$425,000. Builds .4 - 2” per hour.
- Layers from .003 - .02” thick. Accuracy from .005 to .015” depending on size.
- Components can be recycled by crushing and converting back to powder.
- Research is going into materials such as powdered metals, ceramics and composites.
- LOM-1015 (14 x 15 x 10”) US$95,000 LOM-2030 (30 x 20 x 20”) US$180,000
- Sheets of .002 - .02” thick.
- Accuracy of +/- 0.005” achievable.
- Support provided by remainder of sheet.
- Prototypes less fragile than polymers.
- No internal stresses or curing shrinkage.
- Paper waste is non-hazardous.
- Machine can be operated in an office environment.
- Cannot build hollow cavities as single part.
- Adhesive is applied in droplets through a device similar to an inkjet printer head.
- Limited quantitative data available on accuracy.
- 3DP licensed to Soligen Inc. for Direct Shell Production Casting process.
- Internal supports not required.
- May require post processing, depending on material and binder.
- Work continues on limiting impact of binder drops, reducing jagged “print” edges and flow control for the binder.
- Consortium includes Boeing, Hasbro, Johnson & Johnson, 3M & United Tech.
- Ballistic Particle Manufacturing - BPM
- Electrosetting - U.S. Navy.
- Masking & Depositing - Carnegie Mellon
- Shape Melting - Babcock & Wilcox
Research and Development in Rapid Prototyping
Areas of R&D dealing with Part Accuracy Improvement:
Areas of R&D dealing with Materials:
Improvements to current materials:
Areas of R&D dealing with Systems:
Improvements to current technologies:
Examples of RP in Research
Selected Product Development / Prototyping Bookmarks