Process and installation for the manufacture of parts by phototr

Plastic and nonmetallic article shaping or treating: processes – Stereolithographic shaping from liquid precursor

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Details

264308, 264497, 4251744, 425404, 425445, B29C 3508, B29C 4102

Patent

active

058242597

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a process and an installation for the manufacture of three-dimensional objects by phototransformation of a material which is initially in the liquid or quasi-liquid state or in the state of a powder which can be considered as having some properties of a liquid. In this case the material is assumed to be in the quasi-liquid state.
These processes are increasingly used for manufacturing models of industrial parts and are particularly well-suited to the use of information which is already available in computer-aided design (C.A.D.) computer systems.
More precisely, the process which the invention concerns can be defined as follows:
the starting material is a material in the liquid or quasi-liquid state capable of solidifying under the effect of light, for example by polymerization and/or cross-linking (in the case of a monomer or an oligomer) or else by sintering (for example in the case of ceramics);
a quantity of this material is arranged in a tank and a support, consisting of a plate or a platform, intended to support the object to be manufactured is provided in this tank, means being provided for altering and adjusting the level of the material relative to the support, for example by altering the relative position in terms of height of the tank and the support or by feeding material to be solidified to the tank;
means designed for selectively illumminating predetermined regions of the surface of the material contained in the tank are provided;
means designed for successively depositing a layer of liquid or quasi-liquid material on the surface of each previously solidified layer are also provided;
and at least one object or part is thus produced in successive layers.
As regards both processes and installations, many variants have been conceived and used. However, regardless of the means used and the processes employed, one difficulty has been encountered, which relates to the placement of the layer of liquid or quasi-liquid material on the previously solidified layer, and this has the overall effect of lengthening the elementary manufacturing cycle, and therefore lengthening the time required for producing each object.
This difficulty is due to the fact that, regardless of the means used for positioning a new layer of liquid (scraper, pouring device, etc.), a high quality of planarity of the layer put in place cannot be obtained in a very short time. This results from problems of wetting the solid portions, edge effects which occur at the discontinuities between the liquid and solid material, the formation of menisci, phenomena associated with the relaxation of viscous liquids, etc.
These problems are illustrated in FIGS. 1 to 5, appended to the present description, FIG. 1 of which schematically represents a plan view of a tank C combined with a scraper R to which a translational movement along the arrows F1 and F2 can be imparted, and in which a part P1 is arranged during manufacture, this part having a simple parallelepipedal shape in the example chosen.
FIGS. 2 and 3 respectively represent a sectional view along lines 2--2 and 3--3 in FIG. 1 of the residual defects which may be encountered, and FIGS. 4 and 5 represent similar views to FIG. 2, in the case of a part which has a recessed central portion.
According to one known process, when a layer of material has been solidified by illuminating a predetermined region, the support plate is moved relative to the tank, so as to bring this plate closer to the bottom of the tank, by a height corresponding substantially to the thickness of the new layer which it is desired to solidify on the part being manufactured.
Once this movement has been carried out, a scraper such as R, the lower edge of which is in contact with the liquid material, is moved in such a way as to form a wave of material and to spread a layer of this material over the layer already solidified.
FIGS. 2 and 3 show the type of residual defect which is encountered after passage of the scraper, these defects D1 being particularly sens

REFERENCES:
patent: 5238614 (1993-08-01), Uchinono et al.
patent: 5252264 (1993-10-01), Forderhase et al.

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