EP3094431B1 - Method for producing three-dimensional sculptures - Google Patents

Description

The invention relates to a method for producing three-dimensional sculptures after a living model.

It has long been known to make models of living or deceased humans, but also of animals or other three-dimensional designs in order to preserve them permanently, to collect them or to enjoy them by remembrance.

The choice of materials for the production of such models are virtually unlimited. Depending on the material, the production of corresponding sculptures, however, sometimes quite elaborate, especially with correspondingly large role models, as made according to such an original sculptures on a scale of 1: 1 or possibly corresponding enlargements must be made from a variety of individual sub-forms. Individual necessary processing steps, such as the scanning and from such scans calculating virtual images or 3D objects have long been known. The problem here, however, that a variety of different steps is necessary, all of which require a wide variety of know-how in a variety of technical fields. It is the complete manufacturing process from the idea to the final finished sculpture therefore requires a variety of different expertise and a corresponding number of involved people and processing locations.

It is already known to produce smaller objects by the so-called "Lost Wax Method" by casting. This process comes from India and is still practiced there for a long time ( B. RAVI, GL DATTA: "Metal Cating: Back to Future," PROCEEDINGS OF THE 52ND INDIAN FOUNDRY CONGRESS, February 2004 ).

Also, so-called "Rapid Product Development" has long been known ( A. BERNARD, A. FISCHER: "New Trends in Rapid Product Development", CIRP ANNALS - MANUFACTURING TECHNOLOGY, Vol. 51, No. 2, 2002 ). There is already described the generation of a 3D data set of objects by means of computer scanned templates. However, the objects described there are not living examples, but technical objects or even a human skull, which can be scanned by computer tomography.

Also, a method for producing a 3D replica of a human face is already known ( US 2001/0044668 A1 ). There, the human face is first scanned by means of 3D laser scanning, and then a 3D data record is generated from the data obtained. Such data records can then be used by free-form milling to a positive model of the face or to produce a negative model for a subsequent casting process. A human's face can be kept quiet for a while when scanning during the scanning process. However, this is not readily transferable to the scanning of living objects, such as live animals, where the scanning process can be performed almost exclusively on moving objects.

The invention has therefore set itself the task of demonstrating a manufacturing method for producing three-dimensional sculptures, which includes a perfect coordination of the individual processing steps to achieve a manageable effort an optimal result. Such a procedure should to a certain extent be carried out "from a single source".

• Scanning, d. h. das Scannen und/oder Fotografieren oder Filmen aller Dimensionen des Objekts zur Erstellung eines virtuellen dreidimensionalen Bildes,
• Modelling, d.h. Aufarbeitung bzw. Bearbeitung der einzelnen Scans und Fotos oder Filme zu einer realistischen virtuellen Kopie des originalen Objekts,
• Herstellen eines verkleinerten 3D-Modells durch Freiformflächenfräsen,
• Herstellen einer Modelbüste oder charakteristischer Teile der Skulptur im Maßstab 1:1,
• Auslegen und Herstellen des Gussmodells bzw. der Gussmodelle,
• Herstellen der Form bzw. der Formen unter Verwendung der Gussmodelle,
• Gießen der Form/en,
• Nachbehandeln des Gussteiles bzw. der Gussteile
• ggf. form- und stoffschlüssiges Verschweißen der einzelnen Formteile.

This task is initially solved by the following steps:

• Scanning, ie scanning and / or photographing or filming all dimensions of the object to create a virtual three-dimensional image,
• Modeling, ie processing or processing the individual scans and photos or films into a realistic virtual copy of the original object,
• Producing a reduced 3D model by free-form surface milling,
• Making a model bust or characteristic parts of the sculpture in scale 1: 1,
• Laying out and producing the casting model or casting models,
• Making the molds using the casting models,
• Casting the mold (s),
• After treatment of the casting or castings
• if necessary, positive and cohesive welding of the individual molded parts.

According to the invention, it is provided that a miniaturized 3D model is produced after the modeling. This is - especially in larger sculptures - expedient to exclude "unpleasant surprises" in the finished product as possible. Faulty and / or incomplete scans can be detected in this way in good time. The position and expression of the sculpture can thus be defined and optimized in advance.

• Scanning, d. h. das Scannen und/oder Fotografieren oder Filmen aller Dimensionen des Objekts zur Erstellung eines virtuellen dreidimensionalen Bildes,
• Modelling, d.h. Aufarbeitung bzw. Bearbeitung der einzelnen Scans und Fotos oder Filme zu einer realistischen virtuellen Kopie des originalen Objekts,
• Herstellen eines verkleinerten 3D-Modells durch Freiformflächenfräsen,
• Herstellen der Form bzw. der Formen mittels Rapid Prototyping durch Verwendung der 3D-Daten aus dem Modelling und rechnerischen Simulationsprozess,
• Gießen der Form/en,
• Nachbehandeln des Gussteiles bzw. der Gussteile,
• ggf. form- und stoffschlüssiges Verschweißen der einzelnen Formteile.

An alternative solution to the problem is described in the following steps:

• Scanning, ie scanning and / or photographing or filming all dimensions of the object to create a virtual three-dimensional image,
• Modeling, ie processing or processing the individual scans and photos or films into a realistic virtual copy of the original object,
• Producing a reduced 3D model by free-form surface milling,
• Producing the mold or molds by means of rapid prototyping by using the 3D data from the modeling and computational simulation process,
• Casting the mold (s),
• After-treatment of the casting or castings,
• if necessary, positive and cohesive welding of the individual molded parts.

In particular, the alternative method is characterized by an extreme time and cost savings, since all steps from the first scan to the manufacture of the molds can run fully automated. Through rapid prototyping, the data obtained during modeling can be used to directly produce a negative mold made of sand on appropriate devices, into which the casting can then take place. Of course, it is also possible with this method, after modeling first to produce a 3D model, especially in more complicated forms or sculptural judgments.

The production of the reduced model takes place in both alternatives by freeform surface milling.

A further embodiment of the invention provides that the production of the model takes place by rapid prototyping. The model can preferably be made of plastic, for example by means of a 3D printer. However, it is also a production of metal or wood possible. The model bust or characteristic parts or the miniaturized models can be provided with a special plastic / metal coating, especially if the finished sculpture is to be made of stainless steel and / or mirror polished. In this way, a realistic impression of the finished sculpture can already be achieved.

According to a further embodiment of the invention, it is provided that for the design of the casting model mathematical Formfüllungs- and solidification simulations are performed to determine the optimal casting technique.

With the help of the casting model (s), the casting mold (s) are / are molded or directly from the 3D data of the modeling and the computational simulation by means of rapid prototyping, a process known per se, in which the molding base material is applied in layers with a suitable binder system , printed directly without a model. Subsequently, the mold (s) are (are) sized. Prefers the finished mold (s) is / are heated to a predetermined temperature for a defined period of time so that the respectively optimum mold temperature and a minimum of residual moisture in the mold are set immediately prior to casting in the mold.

A further teaching of the invention provides that a quality assurance takes place after the casting aftertreatment. This can take place, for example, in a surface inspection according to the ink penetration method, so that a corresponding post-processing of the defects can take place.

According to a further embodiment of the invention, the sculpture is made of stainless steel in order to achieve a high quality and a long life.

As already mentioned, a special embodiment of the present invention provides that the finished sculpture is mirror-polished. In addition, then the sculpture can be coated in a known manner that the polish gloss remains intact.

The exact sequence of production is described in detail below:
Preference is given to the production of cast in stainless steel and mirror-polished sculptures for living (or a deceased) role model. The size of the finished sculpture is variable. Depending on the actual size of the prototype, a scale of 1: 9 to 3: 1 is possible.

First, a virtual three-dimensional image of the (usually) living model is created (so-called "scanning"). The scanning is done either by scanning and / or photographing or by filming. For deceased critters, existing photo and footage can be used to model and create the 3D data.

Photography / Scanner: For this, the living object is photographed / scanned from all perspectives, so that all dimensions of the object are captured. In addition, lighting effects must be exploited so that the surface contours become visible.

Film / Scanner: For this, the living object is filmed / scanned from all perspectives, so that all dimensions and surface contours of the object can be captured.

For example, scanning can be done simultaneously with multiple (typically 8 to 12 cameras) scan cameras. These cameras are evenly adjusted to the object to be scanned around the object so that all areas can be scanned optimally. At the same time, photos are also created with these cameras. Undercuts are additionally photographed with a high-resolution camera, as they can not be detected by the positioned scanners. Advantage of this system is that even moving objects, such as animals, can be scanned and the 3D model can be processed directly in the computer. Modeling now processes and merges the edited scanner data with the additional photographs. The virtual lifelike, real image of the captured object can only be created from the combination of data (scanner, photography and film) and modeling.

In the ensuing "modeling", the photos / scans and / or the film / scan of the living (or decaying) prototype (living beings) are processed, modeled and networked on the computer in such a way that a realistic virtual copy of the living (or decaying) model emerges. Together with the customer, the position, posture and position of the future sculpture during computer modeling are determined and the characteristic features are worked out.

The computer modeling and virtually realistic replication is done by iterative optimizations and comparison with the photo, scan and film material.

Especially for larger models, after the final virtual computer modeling a model on a reduced scale is produced by freeform surface milling. The production can also be done by 'rapid prototyping'. For this, the computer data is converted into corresponding processing data. By free-form surface milling or by rapid prototyping preferably a plastic model of the virtual model is made. This model can be coated with a special metal coating so that the visual effect of the later sculpture can be simulated.

After the model has been manufactured and released, in the first alternative of the method of the present invention, a 1: 1 bust or characteristic cut is made and coated with a special metal / plastic coating to ensure that the essential details of the living prototype are accurately formed and the character traits that are essential to the client are clearly identifiable also in the later execution, and correspond to the client's ideas.

After adjusting the model and the bust with the photos and / or films as well as with the computer models, the final production release for the stainless steel casting takes place.

Before the casting model production, mathematical mold filling and solidification simulations are carried out in order to optimize the mold filling during casting and thus avoid defects in the casting.

1. a. Kunststoff- oder Holzmodell: Die Maßhaltigkeit muss bei der Abformung des Modells sichergestellt werden.
2. b. Modellteilung: Das Gussmodell muss so geteilt werden, dass die Modellteilungen entlang der natürlichen Konturen (Falten, Halsansatz, Beinansatz etc.) verlaufen.
3. c. Das Gussmodell muss so entwickelt werden, dass die Gussform steigend gegossen werden kann.

In casting model production, the following conditions must be taken into account:

1. a. Plastic or wood model: Dimensional accuracy must be ensured when taking the model.
2. b. Model division: The casting model must be divided so that the model divisions run along the natural contours (folds, neckline, leg approach, etc.).
3. c. The casting model has to be developed so that the casting mold can be poured rising.

Based on the results of the computational simulation, the casting models are now produced. In the second alternative of the method according to the invention, the 3D data of the modeling are processed together with those of the computational simulation so that records arise with which molds can be prepared by rapid prototyping by layering printen mold base and binder. If the molds are produced by means of casting models, a plurality of casting models and core boxes may be needed, depending on the complexity and size of the model / living being. Depending on your size, the sculpture must be cast in individual segments.

The mold is made in such a way that the cast half forms a shell and does not warp when it solidifies because the sculpture is hollow after completion.

The molds are made manually or using a 3D printer (rapid prototyping method). As molding material, various natural as well as synthetic sands are used (quartz sand, chrome ore sand, zircon sand, etc.). As a binder system, a special known cold resin method is used, which is characterized in particular in steel and stainless steel casting by high surface qualities. The binder system envelops the mold base material and gives the necessary dimensional stability after curing of the mold. The surface quality of the casting is significantly influenced by the molding material in combination with the subsequently applied size. When the molds are finished, fan heaters with a prescribed temperature are connected to the molds for a defined period of time. These fan heaters extract moisture from the molds. In this way, the gas pore formation (so-called. Pinholes') is avoided in the later casting. A defined time before casting the heaters are removed from the molds and the casting takes place immediately.

All molds are designed so that the molds are poured downwards and thus impurities, which are on the surfaces of the melt or in the melt, can flow into the feeders or into overflows. All process steps are designed for maximum purity and process reliability with regard to maximum casting quality.

1. a. Der Werkstoff darf keine Ausscheidungen bei der Erstarrung bilden
2. b. Der Werkstoff muss ein geringes Seigerungsverhalten aufweisen.
3. c. Der Werkstoff muss sich durch eine sehr geringe Gasaufnahme auszeichnen
4. d. Der Werkstoff muss spiegelpolierbar sein und darf nach dem Polieren keine Schattierungen/ Ungänzen durch Gefügeunterschiede oder sichtbare Korngrenzen, Ausscheidungen, Seigerungsphänome oder ähnliches aufweisen.

The material used for the melt and alloy are special stainless steel alloys characterized by the following "decisive" properties, so that the polishing of the sculpture surface results in a uniform, defect-free mirror surface:

1. a. The material must not form precipitates during solidification
2. b. The material must have a low segregation behavior.
3. c. The material must be characterized by a very low gas absorption
4. d. The material must be mirror-polishable and, after polishing, must not show any shades / discontinuities due to structural differences or visible grain boundaries, precipitations, segregation phenomena or the like.

The melt guide is the quality-critical process step. So that no impurities and gases adversely affect the quality during the solidification of the casting, the melt must be subjected to a vacuum treatment. In addition to the carbon (according to the Boudouard equilibrium), the vacuum treatment reduces the gases such as nitrogen, hydrogen and oxygen below the required standard values. These otherwise dissolved in the melt gases would be excrete during solidification and form non-tolerable pores, oxides or carbides on the surface.

Following the melting process, the actual casting takes place. For this purpose, a pan, in which the melt is transported to the mold, flooded with a protective gas, so that even when tilting the melt from the furnace into the pan almost no gas absorption can take place. The pan is a stopper pan, allowing the melt to flow directly into the mold via a bottom outlet. The distance between the mold and the floor outlet is max. 10 cm to also minimize gas uptake of the pouring stream during casting.

The demolding of the castings takes place exactly after 24 hours, in this way reproducible and uniform structural properties of all cast halves are formed. This is further supported by the fact that the castings are shell halves with a uniform wall thickness. This is the only way to avoid metallurgical inhomogeneities. The wall thickness of the sculptures is calculated and adjusted on the basis of the sculpture size, the material properties and the necessary static sculptural properties.

For cast aftertreatment (casting cleaning), the casting halves or castings are carefully sanded after removal from the mold. Blasting with blasting grain or the like is avoided because hardening of the surface by blasting results and the polishing ability decreases. Subsequently, the casting and feeder system is removed by sawing or cutting, so that a heat input into the component, which can lead to a structural change, is avoided. Carefully, the casting skin is removed by grinding with permanent temperature measurement. A previously defined component temperature must not be exceeded in order to avoid microstructural changes.

Following the casting post-treatment, quality assurance takes place. This begins with the surface inspection. Here, the dye penetration test is called Test method selected. Defects that are invisible to the human eye become visible and must then be sanded out with fine special sanding heads. Subsequently, with an electrode / welding wire approved for the selected casting material, the defects are welded, grounded and inspected with the least possible heat input.

Afterwards, the segments are measured and welded to each other accurately fitting and checked again by means of dye penetration test.

The mirror polishing must be expertly carried out, and in this case all casting halves are welded in a form-fitting and cohesive manner in an operation specialized in mirror polishing. It is essential when welding that the welds are no longer visible after polishing. The microstructure of the welds must match that of the casting and together form a homogeneous, uniformly polishable surface. In this way, a finished sculpture can be formed from any number of individual pieces of sculpture.

After complete assembly of the sculpture it is preferably mirror polished by a special grinding and polishing process. This process takes place in several steps: rough grinding, fine grinding, polishing and mirror polishing. It is essential that the removal of the surface at all points of the sculpture is uniform, so that the dimensional proportions and tolerances do not change.

After polishing, finally, a sculpture surface is created, which achieves the mirror effect and on the sculpture surface with the human eye does not show any discontinuities.

The sculpture can also be coated with coatings, paints or powder coatings such that the gloss of the polish is maintained.

The method according to the invention will be explained in more detail below with reference to a drawing which merely illustrates preferred embodiments.

Fig. 1

die Abfolge der einzelnen Abfolgeschritte,

Fig. 2A

die Darstellung eines für das Scanning verwendeten zylindrischen Koordinatensystems,

Fig. 2B

die Darstellung eines für das Scanning verwendeten halbsphärischen Koordinatensystems,

Fig. 3A bis 3F

verschiedene Ansichten des Modells bzw. der Skulptur und

Fig. 4

eine noch nachzubehandelnde Skulptur in dreidimensionaler Ansicht.

In the drawing show

Fig. 1

the sequence of the individual sequential steps,

Fig. 2A

the representation of a cylindrical coordinate system used for the scanning,

Fig. 2B

the representation of a semispherical coordinate system used for the scanning,

Figs. 3A to 3F

different views of the model or the sculpture and

Fig. 4

a still nachzubehandelnde sculpture in three-dimensional view.

In Fig. 1 the sequence of steps of the method according to the invention is shown, wherein the step of mirror polishing is characterized as an optional step. Fig. 2A now shows that the model to be imaged, indicated in the example as cuboid 0, must be scanned and / or photographed and / or filmed by a plurality of camera positions K in order to obtain a sufficient data density over its surface density.

On the right side of Fig. 1 An alternative production process is described in which mold production can be carried out by rapid prototyping immediately after modeling. In this way, an even more automated sequence of process steps is possible. In this method as well, it may be expedient to first add a 3D model behind the modeling step finished, which in turn can be produced by rapid prototyping, in particular by means of a 3D printer.

In the in Fig. 2A illustrated embodiment, four concentric and equal circular arcs A, B, C and D are shown and by the reference numerals 1, 2, 3, 4 four uniformly distributed over the circumference of the arcs arranged camera lines are shown, so that in the middle of this on this Formed coordinate system object 0, which is shown in the illustrated embodiment as a cuboid, but could be any three-dimensional object such as a horse, is oriented so that the camera line 1 scanning the object from its right side, the line 2 it from the front, the line 3 allows it from its left side and the line 4 it from behind. The individual camera positions K can also be run through one after the other in a motionless or stationary model. When scanning a live animal, such as a not completely stationary horse, a variety of cameras must be set to get many pictures of a currently ingested simultaneously state of the situation.

Fig. 2B shows that also other arrangements of the camera positions K are possible, for example on concentric circles A ', B', C 'and D' within individual planes E1 and E2 of a semi-spherical arrangement with which, for example, an object 0 'can be scanned, whose top is of particular importance.

For a better explanation of the type of scanning are in the Figs. 3A to 3F the respective representations of the object 0, in the example again a horse, shown. It is the Fig. 3A from the camera perspective B2, the Fig. 3B from the camera perspective B3, the Fig. 3C from the camera perspective B4 and the Fig. 3D shown from the camera angle B1. For clarity, further camera lines 1 'and 1 "are shown between the camera lines 1 and 2 in the exemplary embodiment, each offset by 30 °, so that correspondingly the Figs. 3E and 3F from the camera positions B1 'and B1 "have been photographed.

Fig. 4 shows finally that detected in quality assurance defects on the surface of the finished sculpture 0 can be represented by appropriate methods such as the dye penetrant, so that there any reworking can be carried out very specific.

Claims (10)

1. Method for producing three-dimensional structures based on a living subject, characterised by the following steps:

   - recording, i.e. scanning and/or photographing or filming all dimensions of the object in order to create a virtual three-dimensional image,

   - modelling, i.e. treating or processing the individual scans and photographs or films to form a realistic virtual copy of the original object,

   - producing a reduced-scale 3D model by freeform surface milling,

   - producing a model bust or characteristic parts of the structure on the scale 1:1,

   - designing and producing the casting model or casting models,

   - producing the mould or the moulds by using the casting models,

   - casting the mould/s,

   - finishing the casting or the castings,

   - optionally form-fit and material-fit welding of the individual moulded parts.
2. Method for producing three-dimensional structures based on a living subject, characterised by the following steps:

   - recording, i.e. scanning and/or photographing or filming all dimensions of the object in order to create a virtual three-dimensional image,

   - modelling, i.e. treating or processing the individual scans and photographs or films to form a realistic virtual copy of the original object,

   - producing a reduced-scale 3D model by freeform surface milling,

   - producing the mould or moulds by means of rapid prototyping by using the 3D data from the modelling and a computational simulation process,

   - casting the mould/s,

   - finishing the casting or the castings,

   - optionally form-fit and material-fit welding of the individual moulded parts.
3. Method according to Claim 1,
   characterised in that
   the production of the model is carried out by rapid prototyping.
4. Method according to one of Claims 1 and 3,
   characterised in that
   computational form-filling and solidifying simulations are carried out for the calculation of the casting model.
5. Method according to any one of Claims 1 to 4,
   characterised in that
   the finished mould/s is/are heated to a predetermined temperature for a defined time.
6. Method according to any one of Claims 1 to 5,
   characterised in that
   quality assurance is carried out after the casting finishing.
7. Method according to Claim 6,
   characterised in that
   a surface inspection according to the dye penetrant method is carried out.
8. Method according to Claim 6 or 7,
   characterised in that
   reprocessing of the defects is carried out.
9. Method according to Claims 1 to 8,
   characterised in that
   the sculpture is cast from stainless steel.
10. Method according to Claims 6 to 9,
    characterised in that
    surface preparation is carried out by mirror polishing of the finished sculpture.

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