Stereolithography Advances With Desktop System, Performance Resins

Autostrade Co., Oita, Japan, has released a low-cost tabletop stereolithography (sla) system. The E-Darts unit measures only 430 by 500 by 515 mm, but is able to produce models 200 by 200 by 200 mm. It sells for ¥2.91 million ($24,250) in Japan with a ¥90,000 ($750) annual service contract. High-end sla systems can cost up to $800,000.

The unit’s compactness is achieved through a non-conventional approach to part production. In conventional sla equipment, a laser irradiates a vat of liquid photosensitive resin from the top, and the part under construction moves downward into the bath by layer thickness (typically 0.1 mm). The vat must therefore be at least as deep as the product height plus the height required for the vertically moving platform.

In the E-Darts system, irradiation is conducted through the transparent bottom of the vat, and the part is pulled out of the vat layer by layer, thus enabling a more compact machine structure. John Nishikori, managing director of Saeilo Singapore Pte Ltd., says this also means that parts can be formed from as little as 50 mL of photosensitive resin, whereas conventional systems may need up to 200 L of material.

“As resin can cost $200/L and only lasts three months in the vat, this represents significant inventory and cost,” says Nishikori. Autostrade sells its acrylic photosensitive resin in 1-L cannisters. Saeilo Singapore is Autostrade’s agent in Southeast Asia.

Nishikori says that while part buildup takes longer than in large sla units, the E-Darts’ target market is design bureaus, where slower speeds may not be as critical an issue. For instance, an 8-cm-high model of the Statue of Liberty takes 4 h to produce.

Similar low-cost rp technologies exist. The Thermojet 3D printer from 3D Systems, Valencia, ca, sells for $49,995, and can fabricate 250 by 190 by 200 mm models, but its dimensions are 1.58 by 1.02 by 1.60 m. It builds models from molten thermoplastic build material deposited through a 96-element printhead, using a process resembling inkjet printing.

Meanwhile, DSM Somos, New Castle, de, next month will introduce the first of a range of sla materials that have flexural moduli far higher than those of most other sla materials. ProtoTool 20L, which the company sees as a superior alternative to glass-reinforced nylon, eventually will be joined by other grades in the ProtoComposites line.

The materials are based on a technology coined act-sl (Advanced Composite Technology - Stereolithography). Perform-ance is achieved through incorporation of a high level of filler — ProtoTool 20L uses ceramic filler. The company does not provide details on how it solved the problem of keeping the filler in suspension and enabling good surface properties.

ProtoTool 20L, which is based on a liquid epoxy, has a flexural modulus of 9000 MPa, close to three times higher than top commercial sla resins from rival suppliers such as Vantico, East Lansing, mi, and 3D Systems. Deflection temperature under 0.46 MPa load is 269°C, versus 160°C for the next best material. There is, reportedly, virtually zero shrinkage, compared to 2 or 3% for other systems. Elongation at break is 1.2 to 1.3%, and unnotched Izod impact strength is also modest, at 0.145 J/cm.

The material, which costs 25% more than existing systems, can be used on conventional sla machines. Photopoly-merization is said to be fast.

Key customers have been testing ProtoTool 20L for several months. Parts made with the system include components for pumps, office equipment, auto hvac systems, and reflectors, among others.

Speaking at the Eurostampi moldmaking exhibition in Parma, Italy, in April, DSM Somos executives said that ProtoTool 20L also can be used to make molds. They pointed out that it was recently used for producing a limited series of cell phone covers. A total of 250 were made, a run which technical support specialist Philippe Barcet noted was not the mold limit.

Stephen Moore [email protected]

Peter Mapleston [email protected]