Dismiss
There will be a system update on Friday, May 5th, 6 PM ET. You may experience a brief service interruption.
Browse Prior Art Database

Stereolithography Resin Cooling During Part Fabrication

IP.com Disclosure Number: IPCOM000004828D
Publication Date: 2001-Jun-25
Document File: 3 page(s) / 29K

Publishing Venue

The IP.com Prior Art Database

Related People

Ralph D'Alessandro: ATTORNEY

Related Documents

4,575,330: PATENT [+3]

Abstract

Thermal distortion in build parts can be a source of part inaccuracies and failed builds in stereolithography. In some cases the distortions as a result of heat buildup can be quite severe. Consequently, significant effort has been expended to develop techniques to control thermal distortion in stereolithographic parts.

This text was extracted from a Microsoft Word 97 document.
This is the abbreviated version, containing approximately 48% of the total text.

Stereolithography Resin Cooling During Part Fabrication

Thermal distortion in build parts can be a source of part inaccuracies and failed builds in stereolithography. In some cases the distortions as a result of heat buildup can be quite severe. Consequently, significant effort has been expended to develop techniques to control thermal distortion in stereolithographic parts.

The cured part and the surface of the resin in a SLA-7000 system (manufactured and sold by 3D Systems, Inc. of Valencia, California,) heats during building due to exothermic photochemical reaction, heating by adding energy to the resin from the laser beam, and the elevated temperature of the surrounding air which reduces the effectiveness of the heat transfer from the solified body to the chamber air. The heat generated by the curing of the resin is the major contributor to the part distortion that is observed when scanning under high power and using a large spot size. This occurs due to the expansion of the liquid resin as, for example, when a .004 inch thick layer of uncured resin is deposited by the recoating blade on the heated body. The 0.004 inch layer of liquid resin can be observed absorbing heat from the underlying solidified body using an infrared camera. As the layer is cured, the heat is conducted down into the solid body faster than it is transferred by convection to the surrounding air. This accounts for the slow steady rise to high temperature of the cured body. This condition creates an environment of differential expansion and contraction throughout the part build. As the body cools, shrinkage due to temperature changes introduces stresses that result in distortion.

The bath of resin contained in the machine is often large enough to contain all of the heat; however, the resin heat capacity is so low that efficient cooling of that mass of resin is not achieved. Hot resin, sometimes partially cured, can result in many build-related problems, including wrinkling and part distortion. There is the potential for the creation of a convection current in the resin caused by heat that can lead to inaccuracies as borders move after drawing with the laser beam.

Removing the heat from the resin surface after imaging should result in more faithful and truer part replication since the solid body will maintain it's temperature in a more steady state condition. Some of the ways that resin cooling may be achieved are:

Cooled resin (resin lower in temperature than the bath) is dispensed by a recoating blade on the surface from a separate resin cooling reservoir.

The smoothing member or blade is cooled and acts as a heat sink, removing heat from the surface. This could be achieved using a thermal-electric cooler, re-circulating chilled water or similar mechanism.

Changes in exposure based on part geometry, decreasing the length of time or intensity as the part temperature goes up. This may require temperature dependent working curves.

Cool the current layer using forced convection with ...