rp = rapid prototyping
There are three main rapid prototype rp model machines available suitable for jewelry, toy, medical and other applications requiring the best rapid prototype model detail. rpwax.com has made direct rapid prototype rp machine comparison using identical cad files and has the following rp model conclusion:
Click Here to view rp model direct casting
3D Systems makes the Invision HR machine which is an attractively cased rapid prototype (rp) machine, simple to set up and use. The invision hr delivers fair quality and has excellent build speed. However the invision hr system has two major problems, the machine dependability is very low and the models will not direct cast. A liquid mold must be made of each model. Not only does the liquid mold process take a full day to cure but you loose a generation of quality. You then must cut the mold open and make a casting wax copy using jewelers wax. This duplicate wax model (from the mold) is what is used for the actual casting process.
The Envision Perfactory rp model machine uses an upgradeable dlp platform that is small, sleek and quite. The rapid prototype model quality is good but as with the invision hr there are two major problems. The perfactory requires models to have supports and rapid prototype rp model areas without sufficient support structures are subject to warping and distortion. Equally, if not more disturbing, is the inability to cast the model directly. As with the invision hr rp machine a liquid mold must be made and as mentioned above the mold process is both time consuming and will cost the loss of detail.

Solidscape makes the Patternmaster, t66, benchtop, t612 and modelmaker rapid prototype rp model machines. The build times are much slower than the above rp machines and the models are more fragile. But the Solidscape machines delivers the best rapid prototype rp model detail. The Solidscape series of machines are the only rp machines that will direct cast. You can see actual models and castings by clicking here. The rp jewelry models are at the highest detail level. There is no need for any mold prior to casting because the model material will direct cast. If you are like me and want to take a job and deliver the finished product. The Solidscape series of rp model machines does this best.
Click Here to view rp models
Click Here to view the showcase Click Here to view jewelry designs
Solidscape Precision:
Adjustable Z-axis build layer: from 0.0005 inches (0.013 mm) to 0.0030 inches (0.076 mm)
Achievable accuracy: ± 0.001 inches (0.025 mm) per inch across the X, Y and Z dimensions
Surface finish: 32-63 micro-inches (RMS)
Minimum Feature Size: 0.010 inches (0.254 mm)
Calibrated Configurations for 0.0005, 0.0010, 0.0015, 0.0020, and 0.0030 inches build layer thickness
Maximum build envelope: 12 x 6 x 8.5 inches (30.48 x 15.24 x 21.59 cm)
Uses a non-toxic thermoplastic build material featuring excellent casting qualities (fast melt out, no ash or residue, negligible thermal expansion); highly suitable for direct investment casting and works with a variety of mold-making processes.
Advantages:
It is the most accurate, highest resolution rp machine currently available which can be within +/-0.05mm.
Ideal for parts with very fine feature such as jewelry, toys, medical implements, eye wear, etc.
Super fine layer thickness (0.013mm) is achievable.
No hand finishing or mold making is required when used for direct casting.