U.S. patent application number 11/414573 was filed with the patent office on 2007-03-15 for process for producing a three dimensional object from particles, as well as product produced thereby.
This patent application is currently assigned to DaimlerChrysler AG. Invention is credited to Jialin Shen, Zheng Xu.
Application Number | 20070057398 11/414573 |
Document ID | / |
Family ID | 37545278 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070057398 |
Kind Code |
A1 |
Shen; Jialin ; et
al. |
March 15, 2007 |
Process for producing a three dimensional object from particles, as
well as product produced thereby
Abstract
Generative processes for production of a three dimensional
object comprised of particles are increasingly employed in the
manufacture of casting molds and casting cores. Therein the casting
mold is constituted of sand particles, which are joined using a
binder material. The task of the present invention is comprised
therein, of providing an alternative layer building-up process for
production of a three dimensional object, which achieves sufficient
casting stability, without suffering intolerable quality
degradation due to evolution of off-gases from binder material
during casting. This task is solved by a process employing
particles, which are comprised of a mono- or polyvalent, water
and/or alcohol soluble metals salt.
Inventors: |
Shen; Jialin; (Bernstadt,
DE) ; Xu; Zheng; (Gelsenkirchen, DE) |
Correspondence
Address: |
AKERMAN SENTERFITT
P.O. BOX 3188
WEST PALM BEACH
FL
33402-3188
US
|
Assignee: |
DaimlerChrysler AG
|
Family ID: |
37545278 |
Appl. No.: |
11/414573 |
Filed: |
April 28, 2006 |
Current U.S.
Class: |
264/113 |
Current CPC
Class: |
Y02P 10/25 20151101;
B29C 64/165 20170801; B22C 9/105 20130101; Y02P 10/292
20151101 |
Class at
Publication: |
264/113 |
International
Class: |
D04H 1/16 20060101
D04H001/16 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2005 |
DE |
102005019699.3-24 |
Claims
1-6. (canceled)
7. A process for producing a three dimensional object comprising
the following steps: a. applying a layer of particles comprised of
at least a mono- or polyvalent water and/or alcohol soluble metal
salt upon a target surface, b. spraying a select part of the layer,
corresponding to a cross section of the object, with a liquid
stream containing water and/or alcohol, so that the particles are
joined in the selected part, c. repeating steps a and b so that the
joined parts of the adjacent layers combine to form the object.
8. A process according to claim 7, wherein at least one metal salt
having crystal water and/or at least one metal salt having
condensable anions is employed in step a.
9. A three dimensional object produced by a process comprising the
following steps: a. applying a layer of particles comprised of at
least a mono- or polyvalent water and/or alcohol soluble metal salt
upon a target surface, b. spraying a select part of the layer,
corresponding to a cross section of the object, with a liquid
stream containing water and/or alcohol, so that the particles are
joined in the selected part, c. repeating steps a and b so that the
joined parts of the adjacent layers combine to form the object.
10. The three dimensional object according to claim 9, wherein the
object is a casting mold or casting core.
11. The three dimensional object according to claim 9, wherein the
object is a tool or an insert for a plastic or ceramic mold.
12. A process for casting metal, comprising a. forming a casting
mold by a process comprising (i) applying a layer of particles
comprised of at least a mono- or polyvalent water and/or alcohol
soluble metal salt upon a target surface, (ii) spraying a select
part of the layer, corresponding to a cross section of the object,
with a liquid stream containing water and/or alcohol, so that the
particles are joined in the selected part, and (iii) repeating
steps a and b so that the joined parts of the adjacent layers
combine to form a green casting mold, b. heating the casting mold
to form a brown casting mold, and c. casting a molten metal into
said casting mold.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority under 35 U.S.C. .sctn.
119 of German patent application DE 10 2005 019 699.3, filed on
Apr. 28, 2005.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention concerns a process for producing a three
dimensional object from particles, as well as a object produced
thereby. A generic process of this type is known for example from
WO 2004/112988A2.
[0004] 2. Description of Related Art
[0005] Generally, the known processes for producing a three
dimensional object from particles are increasingly employed for
manufacture of casting molds and casting cores. Therein the casting
shape is built up of sand particles, which are joined by means of
binder materials. Conventionally, organic binders are employed.
These however decompose during casting due to the heat, whereby the
quality of the produced component can be deteriorated. Thus, it is
proposed in WO 2004/112988A2 to join the sand particles with a salt
crystal binder material and/or protein binder material.
SUMMARY OF THE INVENTION
[0006] The task of the present invention is comprised in providing
an alternative layer-building type process for producing a
three-dimensional object, as well as a therewith produced object,
which achieves sufficient cast strength, without causing
unacceptable deterioration in quality due to off-gassing of binder
material during casting.
[0007] This task is solved by the use of particles, which are
comprised of a mono- or polyvalent, water and/or alcohol soluble
metal salt.
[0008] Therein the inventive process for production of a three
dimensional object includes the following steps:
[0009] application of a layer of particles upon a target
surface,
[0010] spraying a selected part of the layer, corresponding to a
cross section of the object, with a stream of liquid, which
contains water and/or alcohol, so that the particles are joined in
the selected part,
[0011] repeating the steps of application and radiation for a
number of layers, such that the adjacent layers join in order to
form the object,
[0012] wherein particles are employed, which are comprised of at
least one mono- or polyvalent, water and/or alcohol soluble metal
salt.
[0013] The term "liquid spray" herein includes not only one or more
continuous or interrupted streams, but rather also individual
droplets.
[0014] In the inventive process, in contrast to WO 2004/112988A2,
sand particles, which there represent the essential structure
forming element, are completely dispensed with. Surprisingly, it
has been found that particles of mono- or poly-valent, water and/or
alcohol and soluble metal salts, subsequent to appropriate
spraying, already have a structural rigidity sufficient to meet the
requirements for a number of casting applications.
[0015] Beyond this, the water and/or alcohol solubility of the
entire particle, in contrast to the corresponding solubility of
essentially only a small binder component, offers the advantage,
that the diffusion of solvent into the surrounding particle bed is
reduced or even completely prevented, whereby a substantially
sharper border or delineation of the sprayed and unsprayed areas
result, and therewith the time and effort invested in the
subsequent follow-up processing can be substantially reduced.
[0016] Advantageous to the invention is the employment of lower
alcohols (chain length .ltoreq.4), since they are simpler to work
with, and in particular ethanol due to its better environmental
compatibility.
[0017] According to an advantageous embodiment of the inventive
process, at least one metal salt includes crystal water and/or at
least one metal salt exhibits condensable anions.
[0018] Metal salts with crystal water are characterized by good
water solubility, for example, NaCl, CuSO.sub.4, or Al.sub.2
(SO.sub.4).sub.3.
[0019] Metal salts with condensable anions (for example with OH--
or ethanol-groups) are characterized by increased brown stability,
for example, NaAl (H.sub.2PO.sub.4).sub.3, K.sub.2SiO.sub.3,
Na.sub.2SiO.sub.3, Na.sub.2(HPO.sub.4) or Na.sub.3(HPO.sub.4).
First, they absorb the solvent and show a good green stability.
Upon warming, a condensation reaction occurs, of which the reaction
products could cause severe defects or gas inclusions during
casting. Thus--just as in the case of metal salts with crystal
water--first, a removal of the solvent by heating is necessary,
from which the brown body results.
[0020] The condensation reaction can be accelerated by the presence
of oxides (for example, CuO, Cu.sub.2O, Al.sub.2O.sub.3, MgO) or
hydroxides (for example Al(OH).sub.3). Na.sub.2(HPO.sub.4) or
Na.sub.3(HPO.sub.4) are water and alcohol soluble.
[0021] It is advantageous to include additives for modifying the
surface tension of the melt of the particles, for example, calcium
phosphate salts, which increase the surface tension of an aluminum
melt and thereby ensure a smooth surface of the cast part.
[0022] An object made of particles joined together, which is
produced by means of the inventive process, is particularly suited
for employment as cast mold or cast core or also as tool or insert
for plastic or ceramic mold shaping.
[0023] In particular, due to their water and/or alcohol solubility,
cast cores or inserts can be easily disrupted and thereafter
removed by spraying with their solvent.
DETAILED DESCRIPTION OF THE INVENTION
[0024] In the following the inventive process and the therewith
produced object will be described in greater detail on the basis of
two illustrative embodiments:
[0025] According to a first illustrative embodiment, in a
conventional 3D printing process using a mixture of NaCl (65 wt. %)
and MgSO.sub.4 (35 wt. %) particles with a diameter between 30 and
100 .mu.m, a casting mold was built up by spraying with water as a
solvent in accordance with a convention 3D printing process. The
thickness of the individual print layers was approximately 125
.mu.m.
[0026] The casting mold had a green stability of approximately 0.75
MPa. It was heated for approximately two hours at 400.degree. C.
and exhibited thereafter a brown stability of 0.62 MPa. The finish
processing time and effort was minimal. A simple blowing off of
loose particle materials with weak compressed air was
sufficient.
[0027] The test of the casting mold tempered to room temperature
with an A356 aluminum alloy casting material at a casting
temperature of 730.degree. provided a good casting result with good
surface quality. The mold itself was easily removed by dissolving
in water for a short time.
[0028] According to a second illustrative embodiment, in a
conventional 3D printing process, using a mixture of Al
(H.sub.2PO.sub.4).sub.3 27 wt. % (condensable water soluble salt);
MgSO.sub.4 (15.7 wt. %) (water soluble salt with crystal water);
CuO 6.1 wt. % and Al.sub.2O3, 6.1 wt. % (oxide as accelerator for
the condensation reaction); Ca.sub.5(PO.sub.4).sub.3OH 5.9 wt. %
(surface tension modifier for Al-melt) and Na.sub.2(HPO.sub.4) 39.2
wt. %, a casting core was built up by spraying with water as
solvent according to a conventional 3D printing process. The powder
mixture had a particle diameter of approximately 300-400 .mu.m. The
thickness of the individual print layers was approximately 125
.mu.m.
[0029] The casting core had a green stability of approximately 3
MPa. It was heated for approximately two hours at 400.degree. C.
and exhibited thereafter a brown stability of 2.5 MPa. This
suffices for employment as casting core. The finishing effort was
minimal. A simple blowing off of the loose particle material with a
compressed air strain was sufficient.
[0030] The test of the casting mold tempered to room temperature,
casting with the aluminum alloy A266 at a casting temperature of
710.degree. C., provided a good cast result with a good surface.
The mold itself was easily removable by dissolving in water for a
short period of time.
[0031] The inventive process and the therewith produced casting
mold demonstrated themselves in the illustrative embodiments of the
above-described examples as particularly suited for metal casting,
in particular for aluminum precision casting, in the automobile
industry.
[0032] In particular, substantial advantages can be achieved with
regard to the quality of the internal surfaces.
[0033] The invention is not limited to only the above-described
illustrative embodiments, but rather can be broadly applied.
[0034] Thus, the surface quality could be further improved by the
addition of supplemental surface modifiers.
* * * * *