Plastic and nonmetallic article shaping or treating: processes – Stereolithographic shaping from liquid precursor
Patent
1997-10-20
1999-05-18
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
Stereolithographic shaping from liquid precursor
264 401, 264308, 264497, 36446826, 36446827, 425135, 4251744, B29C35/08;41/02
Patent
active
059048905
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for producing a three-dimensional object by successive solidification of individual layers of a solidifiable material at places according to the cross-section of the object effected by a beam of electromagnetic radiation, and methods therefor.
BACKGROUND OF THE INVENTION
When producing a three-dimensional object by rapid prototyping a solidifiable substance is applied layerwise onto a support or onto a previous layer, respectively, and solidified for each layer using radiation, for example a focused light beam, at those places of the layer which correspond to the cross-section of the object. If the applied material is a powder and solidified using laser beams, the method is called laser sintering. Such a method is for example known from U.S. Pat. No. 4,863,538. If a liquid photocurable material is used, the method is called stereolithography. Such a method is for example known from U.S. Pat. No. 5,014,207.
The applicant is aware that for the laser sintering the laser beam may be passed over the layer to be solidified according to a line pattern, for example in meanders as shown in FIG. 1.
FIG. 1 shows a top view of a layer to be solidified 1 of a three-dimensional object to be formed in a coordinate system having a x-direction and a y-direction. In this method a line pattern 2 is determined which depends on the geometry of the layer. The line pattern 2 comprises parallel lines spaced from each other by a distance d. For solidifying the layer I the laser beam is passed with a constant speed v across the surface of the layer 1 to be solidified along the line pattern 2 in the direction indicated by the arrow. Owing to the irregular cross-section of the object in this layer the lines have different lengths L.
FIG. 2 shows the density of the layer to be solidified as a function of the layer geometry, i.e. indirectly as a function of the length of the lines passed by the laser beam. It turns out that the density of the layer to be solidified decreases with increasing length of the lines. In summary, this method produces an inhomogeneous density distribution in the layer to be solidified if the line pattern which is followed by the beam for solidifying the layer comprises lines having different lengths and if the beam passes over the layer with a constant speed.
The occurance of the inhomogeneous density distribution as a function of the line length of the line pattern 2, as shown in FIG. 2, can be explained as follows: Generally, rally, the spacing d of the lines of the line pattern is twice or four times smaller than the diameter of the laser beam cross-section on the surface of the layer 1 to be solidified. Thus, a section on a line can be scanned up to five times if the cross-section of the beam is passed along adjacent lines. With a smaller line length a portion of this line is therefore scanned in rapid succession. It is therefore possible to keep this section nearly continuously on a temperature which is higher than or equal to the sintering temperature. Losses by heat conduction are compensated by the rapid timely sequence of the scans. Thus, the input of energy which directly contributes to the sintering process is high in this section and the material to be sintered has a high portion of liquid phase. A high density is produced during the solidification in such a section.
However, if the beam is passed along a long line, a section along this line cools down to ist original temperature owing to heat conduction losses after the passage of the beam cross section over this section. When again scanning this section it must again be heated up to the sintering temperature. Thus, losses due to heat conduction and reheating cannot be compensated in such a section and a solidification occurs with a density which is smaller than the density of the substance in the section having the smaller line length.
Such an inhomogeneous density distribution within the layer to be solidified and therefore within a three-dimensional object to
REFERENCES:
patent: 4863538 (1989-09-01), Deckard
patent: 5014207 (1991-05-01), Lawton
patent: 5130064 (1992-07-01), Smalley et al.
patent: 5352405 (1994-10-01), Beaman et al.
Lohner Andreas
Wilkening Christian
EOS GmbH Electro Optical Systems
Neuner George W.
Tentoni Leo B.
LandOfFree
Apparatus and method for producing three-dimensional objects does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for producing three-dimensional objects, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for producing three-dimensional objects will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1758328