DE19851224C1 - Process for producing defined free form surfaces in molding material comprises applying the molding material and forming free form surfaces using a rolling device - Google Patents

Abstract

Process for producing defined free form surfaces in molding material made of pasty material or bulk material comprises applying the molding material and forming free form surfaces using a rolling device. An Independent claim is also included for an apparatus for producing defined free form surfaces in molding material made of pasty material or bulk material comprising a device (12) for applying the molding material on a base (10) and a rolling device for molding the molding material.

Description

The invention relates to a method for producing defined free-form surfaces in molded material made of pasty material or bulk material and a device for carrying out the Procedure. The production of such defined surfaces is required in many areas, e.g. B. for the Production of molds for metal, concrete, plaster, wax, Plastic, etc., but also for the direct production of Elements from the aforementioned materials. Furthermore, it is necessary, defined areas for the production of To be able to design terrain models. Another Rapid prototyping is one possible application.  

It is state of the art for the production of casting molds known to produce a model, which is then in a suitable Molding material is shown. The making of one Model is expensive and time consuming. Furthermore large quantities of environmentally harmful molding material consumed.

Furthermore, in rapid prototyping with molding z. B. for Manufacture of casting cores known as laser sintering. At In this process, thin layers are successively thermal curable molding material just applied and with a Laser beam hardened. The beam travels along paths, which describe the surface of the molding material to be hardened. This method has the disadvantage that the focal spot of the Laser is small and therefore it takes a comparatively long time until the surface of a layer to be hardened has traversed. Furthermore, this procedure is necessary several times, since each Layer must be cured individually. For example, a structure with a volume of approx. 3 liters a manufacturing time of five to ten hours necessary. Finally, the uncured molding material has to be a layer can be removed after curing.

WO 90/03893 describes the production of a three-dimensional body from successive layers by cutting, fusing, etc. using a  high-energy beam, with that surrounding the body Material is removed later.

For the production of, for example, terrain models is still the hand modeling is known, in which the molding material is manually is formed. This procedure offers the greatest possible Degree of freedom in the design of surfaces. However the manual effort is very high and the shape accuracy low. The geometry of the modeled shape is not defined reproducible. After all, there is multiple toxic mold materials a health hazard for the modeling person.

It is therefore the object of the invention a method for Manufacture of defined surfaces from molding material as well to provide a device for its execution that the Avoids disadvantages of the prior art.

The invention solves this problem by providing it a method for producing defined Freeform surfaces in molded material made of pasty material or Bulk material, the molding material via an application device is applied to an order reason and whereby then the defined free-form surface in the molding material is formed by means of a rolling device. Such a thing Process offers compared to the known processes for machine controlled manufacture of lost molds for the  Casting technology the advantage that it is no longer necessary first create a model for each desired mold, then as a template for the production of the molds is used. Especially for castings that as The manufacture of individual pieces is the production of stencils uneconomical because it is time and cost intensive. So far these molds are made manually, as is the case with the Production of terrain models is common that offers Process the advantage that the former is no longer in It comes into contact with the molding materials, which are often harmful to health. However, the freedom of design remains intact, the accuracy and reproducibility of the Surface design is improved.

Also compared to the well-known laser sintering and other methods the successive curing, such as B. in WO 90/03893 described, there are advantages because the modeling by means of the method according to the invention takes place faster than the gradual curing required for laser sintering. The Formation is also during the To observe modeling and it is not necessary apply excess molding material after the Burning process must be removed again.

The molding material used can be a material with high Be solid.  

The invention further relates to a device for Manufacture of defined free-form surfaces in molding material pasty material or bulk material according to the above Method with an application device for applying the Molding material on an order base and a rolling device, wherein the rolling device is used to shape the molding material, ie for modeling the free-form surface.

According to one embodiment, it can be provided that as Order module a cylinder with a towards the Order opening and serves in the Cylinder a piston to eject the molding material is slidably guided, which can be driven by a motor. The use of such an order module for funding and dosage of the molding material offers compared to conventional Conveyor devices, namely belt conveyors, Tube chain conveyors have the advantage that they can also be used for Dosing molding material is suitable for what these devices not because of the large amount of material transported with it can be used. The well-known screw conveyors, which can also take on a dosing function compared to the order module the disadvantage that it is multiple not for the promotion of molding material with a high Solids content are suitable, as in the manufacture of Surfaces and greeting forms are used. Beyond that the design of a screw conveyor, especially if varying dosing quantities must be provided,  complex in contrast to the simple constructive Design of the order module. The order module can therefore in an embodiment of a cylinder and one therein displaceably guided pistons, with cylinders and Piston either circular or rectangular Can have cross-section. The shifting movement of the Piston is connected to the piston with the help of a Piston rod or push chain carried out with a motor is coupled. The piston is used to apply the molding material first move to its upper end position, the furthest is removed from the order opening of the cylinder. The The order can be opened during the filling process by Example a slider can be closed. The cylinder will then via a flap that can be pivoted, for example trained filling opening filled. The flap serves when filling as a slide for the molding material and can Completion of filling can be closed to prevent leakage of the molding material while being pushed out by the piston prevent. Then to push out the molding material Slider removed the cylinder's job opening, the points towards a molding box or order reason, closes. The piston is then driven by the engine moved towards the order opening, the Mold material emerges from the order opening. In the Order opening is a rigid graduation grid, which Lumps of the molding material that are formed in the cylinder  can have divided and so an even order of the Ensures molding material on the order reason.

To reduce the friction between the piston and the cylinder wall, can be provided to the piston in the cylinder with play to lead. This game can be designed to be approximately corresponds to the diameter of the solid particles in the molding material. As a result, particulate matter enters the gap can get between piston and cylinder. Now the Piston moves in the cylinder, this leads translational Movement to a rotation of the solid particles in the gap. The Solid particles thus serve as rollers between the cylinder wall and pistons. The now only existing rolling friction between the order module parts cylinder and piston is considerable less than the usual static friction.

To reduce the wall friction between the piston and cylinder a belt guide of the piston can also be provided.

The piston is moved by means of an in the cylinder wall are arranged over at least one Part of the cylinder length extending tape guide one or more circumferential, closed in a ring Tapes. The band (the bands) run parallel to the Cylinder wall in the direction of the piston movement. The The belt guide is connected to the motor and is removed from it driven. For example, four tapes on one  Cylinders with a rectangular cross section can be provided. Each the ligaments can be closed in a ring and over two Rolls run. So each band extends along the inner cylinder wall from the upper end position of the piston to to the lower end position of the same. The axes of the rollers are in one plane with the cylinder wall and are rotatable in the same stored. The tapes lie flat on the inner wall. The piston is connected to the belts in the direction of flow. The movement of the belts, that is, their revolving takes place synchronously, by the movement of the piston. Depending on the direction of movement of the The belts are guided towards the job opening by piston or in the opposite direction.

According to a further exemplary embodiment, that the application module and / or the rolling device with a Manipulator arm connected to an industrial robot and by this is led. The control of such Industrial robots, for example, are done using direct Transfer of the CAD data of the target surface to a computer, control via an offline programming interface of the industrial robot. Is one in the molding box Coarse shape has been introduced, so is the volume of the order to be calculated from the preset rough shape and the Target surface. If the surface is unknown, it can be used Calculation of the required molding material volume by a sensor, for example a laser scanner before the actual application be scanned. The order of the calculated amount of molding material  can then already take into account the required Quantity on a specific section of the order reason respectively. In other words, a larger one later Material thickness should be more from the outset Molded material applied. So later unnecessary rolling work can be done be avoided.

The rolling device can comprise at least one roller, by means of shaping the applied molding material he follows. To do this, the roller is pressed with a certain amount of pressure about the molding material applied in the appropriate thickness led and distributed the molding material in the desired manner to create a defined surface structure.

So to prevent the roller from not turning, so not rolls, but is blocked and only pushed and piles the molding material in front of it or pushes it together or even throws over itself, can be provided to use driven roller. This can slip over the surface to be guided. The drive can, for example via a drive belt that is coupled to a motor, respectively. It can continue to prevent this problem be provided, several rolls to form a roll assembly to couple with each other or to arrange one behind the other. Furthermore, the roller or the roller body can be profiled to improve the distribution of the molding material. Such grooves or coils in the roller body,  that run from the center of the roll to the ends of the roll to the fact that the molding material from the middle of the roll to the Roll ends is transported away laterally.

Finally, with regard to roller design, there is Problem that simple cylindrical rollers do not allow round, curved surface in the rolling direction shape. A concave surface is therefore set when using cylindrical shaped rollers in Rolling direction from a series of straight surfaces with different Inclines together, always creating edges or kinks when moving from one surface to the next. To do this can avoid rolls with a curved surface, such as Example rollers with barrel-like or hyperboloidally curved Shell surface can be used. With these rollers you can easily form "valleys" and "mountains". However, in order to Exchange or exchange of rollers for different ones Surface geometries, especially on a track can avoid using rollers according to one embodiment flexibly changeable shape can be used. This means, the roller shape can be during the shaping of the surface of the Target surface shape to be adjusted. This can be done through a Force take place that acts on the inside of the roller and the The outer surface of the roller is deformed in a defined manner. The Apply force centrally or off-center, so that one symmetrical or asymmetrical roll deformation is achieved. The roll can be deformed mechanically, by pressure,  Thermal expansion, condenser effect, magnetic effect, induction etc. done. The deformation by pressure is done by in the hollow roller inside to create a barrel shape Pressure medium introduced from a pressure accumulator and so the The roller is "pumped up" until its outer surface reaches the desired one has reached convex curvature. The reverse occurs a roller with a concavely curved outer surface Evacuate the inside of the roller. The roller jacket has to be like this be designed so that it allows deformation and after Relief reshaped back into its cylindrical shape. Gases, liquids and pastes can be used as the pumping medium. For the maximum deformation in such hollow rollers Setting inside can be provided inside the roller To attach shaped sheets that correspond to the maximum Curvature can be pre-bent and when the Serve inside the roller as a stop for the roller shell. This Shaped sheets have holes for direct action of the pressure medium to the wall of the cylinder jacket allow.

The deformation can also be by means of a mechanical Setup inside the roller can be achieved using a Guide rod is movable from the outside.

To enable an asymmetrical deformation of the roller, can, for example, several pressure chambers in a pump roller be provided, which are separated from each other by partitions  are and do not equalize each other. Each The pressure chamber is then separate from the pressure supply line and the Pressure vessel connected. There are rigid, inextensible walls however, in each chamber to a symmetrical deformation lead, which in turn leads to abrupt transitions of the mantle surface can result from one chamber to the next be to provide stored or elastically stretchable partition walls, so that a uniform asymmetrical deformation of the Roll jacket is achieved.

In order to save molding material, a preformed rough shape. Such rough forms consist, for example, of rod-shaped pins that are in be clamped together, the end faces of the differently clamped bars a stair curve Forming surface with adjustable geometry. Such Shapes are, for example, in DE 41 12 736 C2, the DE 196 27 930 A1 and DE 197 34 286 C1.

It can also be provided that the device with a Storage facility and / or a conveyor for automatic or semi-automatic filling of the Order module to provide, since the order module only up to Handling weight of the manipulator can be filled. A a single filling is therefore usually not sufficient, one sufficient amount of molding material for a to be designed Provide surface. Finally, the device  have a mixing device for mixing the molding material. Both conveyor and Screw conveyor into consideration. The mixer serves the Molding material before application with binders, water etc. mix.

Further features of the invention result from the Claims and other application documents.

Exemplary embodiments of the invention are shown in the drawing shown. Here shows - in a schematic representation:

FIG. 1 shows a device according to the invention;

Fig. 2: a roller with variable configuration at various positions of a curved surface;

FIGS. 3A-B: a symmetrical or an asymmetrical roller pump; and

4A-B. Partial views of the feeder in two different configurations.

Fig. 1 shows a device having a job base 10 or a molding box, who has already a rough mold (not shown). An application module 12 is attached above the application base 10 , which is guided by means of a manipulator arm 14 of an industrial robot and is attached to a frame 16 via this. The industrial robot is controlled in such a way that the molding material is distributed according to the subsequent surface profile. The amount is chosen so that the desired surface can be shaped later without having to move unnecessarily large amounts of molding material. Since the application module 12 , which consists of a cylinder 18 and a piston guided therein, can only be filled up to the manipulation weight of the manipulator, the entire volume that is necessary for producing a corresponding surface profile cannot be taken up by the application module 12 at the same time become. The filling can take place by means of a belt conveyor 20 which connects the application module 12 in its filling position (shown) with a screw metering device 22 which is responsible for providing an amount of molding material corresponding to the handling quantity. The molding material is stored in its dry form in a silo 24 , which is connected to a mixing chamber 28 by a belt screw conveyor 26 . In the mixing chamber 28 , water 30 is added to the dry molding material and mixed with it by means of a stirrer or mixer 32 in order to produce a pasty, homogeneous material. After the addition of water 30 , the pasty molding material then enters the screw metering device 26 via a chute 34 , which in addition to its metering and conveying task also ensures that the mixture of dry molding material and water remains homogeneous.

The molding of the molding material in the application base 10 takes place by means of a roller arrangement (not shown), which is also connected to the industrial robot or is attached to a second manipulator arm (not shown).

FIG. 2 shows the use of rollers with different surface configurations or the geometries of a flexible roller that is pressurized differently to produce different surface geometries. The molding material 40 has been applied here by the application module (not shown) with a relatively uniform thickness to a coarse mold 42 which consists of metal rods 44 fixed relative to one another. The use of a coarse mold 42 which is placed on the order base has the advantage that molding material 40 can be saved. A defined surface is formed using a roller 46 , which is shown here in various positions during surface processing. To create concave or convex shaped surface profiles in the rolling direction, it is necessary to use rollers 46 , the lateral surfaces of which are also concave or convex, since otherwise only straight surfaces can be formed, at the transitions of which kinks or edges form. In addition to the use of rigid barrel-shaped or hyperboloidal rollers, as shown, rollers 46 with a variable shape can be used, which have the advantage that there is no need to change the rollers. In the case of so-called pump rollers, the shape is changed by changing the internal pressure of the roller. However, the change in shape is completely reversible. For this purpose, the rollers 46 are connected via a tube 48 to a pressure generating device (not shown). The outer surface of the roller 46 consists of a flexible material. If the roller 46 is to have a barrel shape 46 f in order to form a concave surface, a pressure medium is introduced into the roller body via the tube 48 , which leads to a deformation of the roller 46 , the main deformation occurring in half the roller length. If the pressure is released again, the roller 46 initially changes into its cylindrical shape 46 z, but if negative pressure is applied, the roller 46 deforms into a hyperboloidal shape 46 h. The deformation of the roller 46 can vary depending on the desired surface curvature, which is regulated by the size of the pressure applied. The production of surface curvatures of the free-form surface which merge into one another is made possible in this way.

FIGS. 3A and 3B now show different configurations of such rolls with changeable shapes. 3A as shown in FIG. 46 a roller, the shape change takes place by means of a mechanical device 50 inside the roll 46. The solid lines represent the undeformed, cylindrical state of the roller 46. Starting from this basic position, the roller 46 can be converted both into a barrel shape and into a hyperboloidal shape, which are shown by dash-dotted lines. The deformation is caused from the outside by a guide rod 52 which extends into the roller 46 from the outside inwards. The deformation takes place by translatory displacement of the guide rod 52 in the direction of the arrows 54 , a movement in the direction of the black arrow 54 s leading to a convex deformation and a movement in the direction of the white arrow 54 w leading to a concave deformation of the roller 46 . For this purpose, the guide rod 52 is connected in the interior of the roll in the region of its free inner end 56 in an articulated manner to a plurality of transmission levers 58 , which in turn are connected in an articulated manner to adjusting levers 60 . The adjusting lever 60 engages with one end 60 w on the roller wall 46 w and is detachably connected to it. The other end 60 v of the adjusting lever 60 is articulated to an adjusting device 62 for the force application point. The linkage of the transmission lever 58 is between the two ends 60 w and 60 v. The adjusting device 62 consists of a tube which is guided through an opening 64 in the roller 46 and is mounted in the opening 64 and in the interior of which the guide rod 52 is arranged and guided. The force application or deformation application point P is adjusted by translatory displacement of the adjusting device 62 for the deformation application point P in the direction of the center of the roller or in the opposite direction, which enables an asymmetrical deformation of the roller 46 . If the roller 46 is now to be transferred from its basic position to a drum position, the adjusting device 62 remains in the basic position, the force application point being in the middle of the roller, so that a symmetrical drum shape is achieved. The guide rod 52 is then pulled out in the direction from the center of the roller (black arrow 54 s). As a result, the angle α between the transmission levers 58 and the guide rod 52 increases up to a maximum of 90 °. By this deflection of the transmission lever 58 , the adjusting lever 60 is also deflected in such a way that it is pivoted about its fixed point of application P, in which they are connected to the roller shell 46 w, the angle β, which is between the adjusting levers 60 and the roll wall 46 w is included, also enlarged. This then leads to the fact that the adjusting device 62 for the force application point is displaced translationally in the direction of the center of the roller. The concave deformation of the roller 46 is reversed accordingly.

FIG. 3B shows a roller 46 whose shape can be changed by means of an increase in pressure in the interior of the roller or an evacuation. Such a "pump roller" assumes a barrel shape when the inside of the roller is pressurized; if the interior is evacuated, it takes on a hyperboloidal shape. In the roller 46 shown, a liquid is used as the pressure medium. In order to also enable asymmetrical deformations in the case of pump rollers, the roller 46 is divided into three chambers 46 k ( 1-3 ). Since a rigid separation of the chambers 46 k, for example through walls, leads to an uneven deformation and undesirable kinks form in the outer contour of the roller 46 in the region of the walls, the chambers 46 k are not rigidly separated from one another in the roller shown, but rather by bearings to such a length adjustment of the limits to provide limits 70 which are translationally displaceable in their respective guides 72 and 70 so that a smooth transition from one chamber 46 k to the next, corresponding to the various set in the chambers 46 K1 3 pressures. The dash-dotted line represents an asymmetrically deformed roller, the first chamber 46 k1 (from the left in the drawing) being subjected to the greatest pressure from the three chambers 46 k, the second chamber 46 k2 to a lower pressure and the third chamber 46 k3 is under normal pressure. The supply of the printing medium or the evacuation takes place via a pressure supply line 73 which extends through an opening 74 in the roll interior and having an output in each of the three chambers 46 k1. 3

FIG. 4A shows a section of a section through the application module, wherein there is play between the piston 80 and the inner wall 82 of the cylinder 84 . If the piston 80 is now moved in the direction of the arrow in order to apply the molding material (not shown) into the molding box, solid particles 86 get into the gap between the piston 80 and the cylinder 84 and are set in rotation by the translatory movement of the piston 80 , so that they act like a "ball bearing". Blocking of the piston 80 is prevented by this rolling.

FIG. 4B finally shows a further system for reducing the friction between piston 80 and cylinder 84 , here in a cylinder 84 with a rectangular cross-section, the piston 80 being fixed to belts 88 , each by means of two rollers 90 , 91 , which in the Wall of the cylinder 84 lie and are rotatably supported there, are guided all around. The rollers 90 , 91 span the belts 88 between them. The annularly closed bands 88 thus run from the upper roller 90 along the inner cylinder wall against which they rest, to the lower roller 91 , around the roller 91 and along the outer cylinder wall back to the upper roller 90 .

Overall, the piston 80 is guided by four belts 88 , each of which is arranged on one of the side walls of the rectangular cylinder 84 . All four bands 88 move synchronously. Since the belts 88 are now guided and revolving over the rollers 90 , 91 , the piston 80 moves from its initial position at the level of the upper roller 90 to its end position during the ejection process of the molding material 92 at the level of the lower roller 91 . This guide system for the piston 80 also leads, like the arrangement shown in FIG. 3A, to a reduction in the wall friction between the piston 80 and the cylinder 84 .

Claims (22)

1. A method for producing defined free-form surfaces in molding material made of pasty material or bulk material, the molding material being applied to an application base via an application device, characterized in that the defined free-form surface is then shaped in the molding material by means of a roller device. 2. The method according to claim 1, characterized in that as a molding material, a material with a high solids content is used. 3. Device for producing defined free-form surfaces in molding material ( 40 , 92 ) from pasty material or bulk material according to the method according to one of claims 1 or 2 with an application device ( 12 ) for applying the molding material ( 40 , 92 ) to an application base ( 10 ) and a rolling device, characterized in that the rolling device is used to shape the molding material ( 40 , 92 ). 4. Apparatus according to claim 3, characterized in that a cylinder ( 18 , 84 ) with an application opening pointing in the direction of the application base ( 10 ) serves as application module ( 12 ) and in the cylinder ( 18 , 84 ) a piston ( 80 ) for sliding out the molding material ( 40 , 92 ) which is driven by a motor. 5. The device according to claim 4, characterized in that the cylinder ( 18 , 84 ) and the piston ( 80 ) have a circular or rectangular cross section. 6. The device according to claim 4 or 5, characterized in that the piston ( 80 ) in the cylinder ( 18 , 84 ) is guided with play. 7. The device according to claim 6, characterized in that the game corresponds approximately to the diameter of the solid particles ( 86 ) in the molding material ( 40 , 92 ) and the solid particles ( 40 , 92 ) serve as rollers between the cylinder wall and piston ( 80 ). 8. Device according to one of claims 4 to 7, characterized in that the piston ( 80 ) with a arranged in the cylinder wall, extending over at least a portion of the cylinder length band guide, which comprises at least one band ( 88 ), and wherein the band ( 88 ) runs along the inner cylinder wall in the direction of the piston movement and the band guide is connected to the motor or is predetermined by the movement of the piston. 9. Device according to one of claims 4 to 7, characterized in that the piston ( 80 ) is connected to a thrust chain driven by the motor and is movable. 10. Device according to one of claims 4 to 9, characterized in that a rigid dividing grid for dividing the molding material ( 40 , 92 ) is arranged at the application opening of the cylinder ( 18 , 84 ). 11. Device according to one of claims 3 to 10, characterized in that the application module ( 12 ) and / or the rolling device with a manipulator arm ( 14 ) of an industrial robot is connected and guided by this. 12. The device according to one of claims 3 to 11, characterized in that the rolling device comprises at least one roller ( 46 ). 13. The apparatus according to claim 12, characterized in that the roller ( 46 ) is a driven roller ( 46 ). 14. The apparatus according to claim 12 or 13, characterized in that the roller ( 46 ) is a profiled roller ( 46 ). 15. The device according to one of claims 3 to 14, characterized in that the rolling device consists of a plurality of rollers ( 46 ) arranged one behind the other. 16. The device according to one of claims 12 to 15, characterized in that the roller ( 46 ) is a roller ( 46 h, 46 f) with a curved surface. 17. The device according to one of claims 12 to 16, characterized in that the roller ( 46 ) is a roller ( 46 ) with a variable shape. 18. The apparatus according to claim 17, characterized in that the roll shape can be changed mechanically or by pressure is. 19. Device according to one of claims 12 to 18, characterized characterized in that the roller shape symmetrical or is asymmetrical. 20. Device according to one of claims 3 to 19, characterized in that the application base ( 10 ) includes a preformed rough shape ( 42 ). 21. Device according to one of claims 3 to 20, characterized in that a storage device ( 24 ) and / or a conveyor ( 20 , 22 , 26 , 34 ) are provided for filling the application module ( 12 ). 22. Device according to one of claims 3 to 21, characterized in that a mixing device ( 28 ) for mixing the molding material ( 40 , 92 ) is provided.