The invention refers to a method for producing three-dimensiona objects by using a converting machine controlled by compute instructions, at which the material comprises a number of sheet or disc - shaped sections defind in size, which are treated i accordance with given computer instructions, so that parts o material are permanently removed, and the sections treated i this way are connected to each other layer by layer in programmed sequence forming said three-dimensional object.

Background of the invention

In construction work it is desired to visualize and sometime also physically present the three-dimensional geometry of th constructive element. This applies especially to work wit computer aided design (CAD) where the data bases often directl without human intervention are used for manufacturing purpose (CAM). The costs for errors in connection with treatment i numerically controlled converting machines and other automati manufacturing machines due to misconstructions, are high.

In complex three-dimensional geometries, e.g. cylinder heads o internal combustion engines, and mounting of several cooperatin components which are difficult to survey, e.g. in lay-out work in engine houses for private cars, the access of physical model early in the construction process is often a condition for th performance of the actual construction work.

Big companies, e.g. car industries, which are often confronte with this need, generally have pattern shops of their own wher details are produced at the demand of the constructor i materials that are relatively simple to work or shape. Certai industries also use CAD-data bases for model production in e.g. NC-cutters. Small companies engage external pattern shops or i certain cases completely eliminate this step in the produc development work, resulting in high cassation costs at the finis manufacture.

It however applies to all pattern manufacturing methods used a present that the recording - and manufacturing work is time consuming and causes discontinuity in the actual working task o the constructor, i.e. to finish and approve the manufacturin basis for the final product or component.

Thus it is desired that if possible offer the constructor a mor direct apprehension of his or her object, so that an interactiv process can be provided between the creativity of the constructo and his or her result' without time - consuming delivery periods.

One way of providing a certain sense of the three-dimensiona geometry of the object is used by some CAD-suppliers, at whic the system allows the constructor to look at the object from a optional visual angle on the viewing screen and by that ex perience a photo-like perspective picture of the object. Grea efforts have been made by the supplier aiming at increasing t realism in this type of presentation, e.g. by means of choice colour scheme and shading. In practice it has however proved th this type of appliance are of greater use at sales and aesthet cal presentations than actively contributing to a decreased ne of real physical models in the construction work.

A method of making physical models by means of CAD-data bases direct connection of the work place of the constructor described in US-A-4,575,330 (C.W. Hull). This so called stere lithographic method is based on the principle that a UV-radiati focused light beam cross links and by that cures the point impact on the surface layer of a liquid photo polymer. The lig source, which is controllable in two dimensions above the ba with the UV-curing plastic liquid, can then cure a cross-secti from the desired model. The section made in this way is deposit on a table which is movable in the vertical direction of t bath. By gradually lower the table after each finished cro section each layer can be bound to each other and a complet model of the ob ect be produced.

This method, which by time reasons only should produce scal models, has up to now been tested successfully only in smal machines having a capacity of some cubic decimeters. The dimen sional accuracy has been said to be a problem due to shrinkin and interior tension which cause deformity in the finished model The high cost price of the equipment and the relatively time consuming process for model manufacturing of a number of hour per model, are factors which limit the utility of the method.

The US-A-4,752,352 discloses an apparatus and a method fo forming an integral three-dimensional object from laminations. sheet - shaped material is cut into the required shapes in a wor station and the individually shaped laminations are assembled i a pre-selected sequence in an assembly station into the form o the three-dimensional object. This apparatus leaves quantities o waste material from the cutting operation, which is a drawback.

As a summary it can be stated that effective and practica appliances in the product development work for interactive mode manufacture in immediate connection to the work place of th constructor are still missing.

The purpose and most important features of the invention

The object of the present invention is to provide a method whic enables an interactive manufacture of three-dimensional models which in all essentials are in agreement with the CAD-data bas which the operator intends to reproduce. The method shall in thi way provide a quick manufacture of the object in question withou human intervention after the operator, via his or her workin terminal, has ordered manufacture of one or more models, and a apparatus for performing the method.

By that is meant a method which provides an apparatus which ca be placed in offices and which apparatus can produce comple three-dimensional models, which digitally can reproduce th object defined in the data base.

Thus the method should admit manufacture models with hollo spaces, which not necessarily need to have a draught fo imaginary cores or other tool parts at shaping, e.g. injectio moulding. The method should further allow manufacture i different materials such as stiff homogeneous or foaming plasti materials, elastic rubber - like materials and certain metals an other materials with low melting temperature. The method shoul further not leave quantities of waste material after the manu facture of the object.

These object have been solved by the fact that on each fat sid of the respective section there is placed at least one electrode and that an electric voltage, sufficient for causing spark - ove between the electrodes is impressed upon these, so that parts o praticles of material located substantially opposed to the elec trodes are removed from or connected to the respective section.

An apparatus for performing this method solves the problem by th fact that on each flat side of the respective section there i placeable or placed at least one electrode and that the elec trodes in accordance with given computer instructions ar connectable to an electric voltage source, which is sufficie for providing a spark - over between the electrodes, so th prats or particles of material are removed from or connected wit the respective section.

Description of the drawings

Figure 1 shows a typical user situation where an apparat according to the invention enables interactive manufacture models at terminal work.

Figure 2 shows the device according to fig. 1 in perspective a partial in cross - section, so that the interior of the inventi is shown. Figure 3 shows a contact frame in perspective view havi internal contact teeth and on a larger scale a portion of t frame where the contact teeth are shown.

Figure 4 shows a work piece in perspective view where three

the outermost material discs have been separated from the wor piece and from each other, in order to show the direction of th grid threads.

Figure 5 shows a portion of a material disc with surroundin electrode layers in perspective. A voltage source is symbolicall connected between a grid thread on the upper side od the disc an a grid thread adjacent to the underside of the disc, at which spark discharge through the crossing area of the grid threads ha also been illustrated. Figure 6 shows a spark discharge between two grid threads in th outermost disc of a piece of material. The crossing area is als shown on an enlarged scale in order to illustrate how the spar can cut undesired rests of grid threads.

Figure 7 a shows an alternative apparatus according to th invention in which the grid threads continuously can be remove from the piece of material through extraction after complete material treatment in every cross - section. The figure als shows both end portions of the grid threads on an enlarged scale

Figure 7b shows a section through the enlarged, right end portio of fig. 7a, as seen in the direction of the arrow in fig. 7a.

Figure 8 shows how a cross - section S - S in an object is shape in a material disc with its surrounding electrodes.

Figure 9 shows in perspective an apparatus with moveabl treatment tool according to the invention. Figure 10 is a side view of the device in fig. 9. The workin station of the treatment tool is enlarged in order to show th details more clearly.

Figure 11 is a side view of a further apparatus with fixe electrode disc. The working station of the treatment tool i enlarged in order to show the details more clearly.

Figure 12 shows how a flatbed plotter can be provided wit accessories which can treat discs according to the method of th invention.

Figure 13 is a side view of an apparatus according to th invention where a single - row spark electrode cam can be brough close to an untreated material disc with very high speed.

Figure 14 shows the apparatus according to fig. 13 from above.

Description of embodiments

On the drawings, which show embodiments of apparatuses fo performing the method, the numerals denote: 1. A complete apparatus for manufacturing models according to th invention.

2. A terminal or working station connected to a CAD-computer o the like.

3. A model manufactured according to the invention. 4. A feed screw for propulsing the work piece through a contac frame.

5. A drive means for the feed screw.

6. A work piece material.

7. A control unit connected to a CAD-computer or the like. 8. A connection member, e.g. a cable, between control unit an contact teeth.

9. A frame with internal contact means for electric connection t grid threads, called contact frame.

11. A table for finished models. 13. A contact member called contact tooth.

16. A sheet -, path- or disc shaped section of material call material .disc.

17. A grid thread.

18. A spark or arc. 19. A voltage- / current source.

20. An imaginary geometry in a material disc which is intend to be left after completed spark treatment .

21. A symbolically illustrated circuit breaker or other memb which can form the intended circuit and which can be controll by the control unit.

22. A thermal barrier layer.

23. A contact block for grid threads.

24. An insulating layer, e.g. a lacquer layer, surrounding a gr thread. 25. A hollow space caused by treatment where material has be removed, e.g. melted or evaporated from the material disc. 26. A connection means, e.g. a conical hole, for grid threads the connection means of the control unit.

27. A segment of a material disc corresponding to the cros section in question of the object of which a model is intended t be manufactured.

28. A store of untreated disc - shaped material, e.g. a roll. 29. A servo- steered movable device for displacing the treatmen tool in two independent directions parallel with the materia disc and called X - Y servo.

30. A guide, e.g. a gear rack, for guiding and driving the X - servo. 31. A model, manufactured according to the invention, durin manufacture.

32. An assembly plate for fixing, e.g. through vacuum, the firs finished disc section of a model.

33. A drive - and guide means for translating movement of th uncompleted model, called stamp.

34. A base plate which is fixed with respect to the holding - o plate.

35. A cable for energy supply.

36. A treatment tool, e.g. a spark electrode or laser gun, calle tool.

37. A plate called holding - on plate which does not actuate th treatment process.

38. A hollow space made in the material disc by the treatment process. 39. A store for collecting material disc rests after finishe treatment , e.g. a roll.

40. A cable for connecting the sliding contact and the curren supply of the apparatus.

41. A sliding contact for galvanic contact to the foil layer o the material disc.

42. A spark electrode.

43. An electrical conductive layer, e.g. graphite or metal foil called foil layer substantially covering one side of the whol material disc. 44. A logic and/or power supply unit, called drive circuit, whic distributes the necessary voltages to the spark electrode i question, according to control data from the control unit. 45. A cable for serial communication and energy supply betwee

drive circuits and control unit and/or current supply unit.

46. A flatbed plotter.

47. A unit which supplies the treatment tool with the required energy. 48. A spring device which prestresses the store of unconnected material discs against gussets.

49. A store guiding untreated material discs.

50. A staple of untreated and unconnected material discs.

51. A servo- steered moveable device for displacing a single ro spark electrode cam and e.g. a infra - red tube in i directio parallel with the material disc.

52. A gusset which positions an untreated material disc.

53. A heat radiating element, e.g. an infrared tube.

54. A .wastage material surrounding a finished material disc. 55. A layer of thermally effectable joining agent, e.g. a meltin glue.

56. A single - row spark electrode cam.

57. A means for treatment material.

58. A unit for joining treated material discs.

The method according to which the invention is applied enable different principles for the design and the function of the wor piece material and the apparatus. According to one principle good three-dimensional steerability of the treatment is enable with a considerably smaller number of grid threads per materia disc than the case would be if every single spark discharge spo was connected to separate conductors. Figs. 2,3,4,5, and 6 sho apparatuses according to this principle.

The workpiece material, e.g. a block with bigger dimensions tha the finished model 3, consists of a great number of sections 1 physically connected to the block or consisting of loose disc 16a and 16b, between which a great number of electricall conductive, thread - shaped and in their longitudinal directio parallel eletrodes 17, called grid threads, are electricall insulated from each other and applied in a grid - like patter along the entire surface formed in the cross - section betwee each material disc 16. Each such electrode layer is beside

arranged transverse to adjacent electrode layers. The workpiec material 6 can thus in its longitudinal direction (according t fig. 4) be composed of electrode layers 17 with horizontal ne threads 17, a material disc 16a, a electrode layer with vertica grid threads 17, a material disc 16b, a electrode layer wit horizontal net threads 17, a material disc 16a etc. etc. workpiece material 6 composed in this way shall be uniforml joined together and externally have flat limiting surfaces wit dimensional accuracy. Each separate net thread 17 should at on end be terminated with, or in connection with, one of the oute limiting surfaces of the workpiece material.

Net threads 17, which encloses a separate material disc 16 i two crossing layers, form a bar pattern with a large number o crossing spots, defined by the crossing point of two transvers grid threads, as seen in the longitudinal direction of th workpiece material, and the material located therebetween, a seen in the cross direction of the workpiece material, see fig 4.

By connecting a net thread 17 in each electrode layer on bot sides of a material disc 16 in the workpiece material, to a appropriate voltage 19 short - circuits can cause a spar discharge with adherent arc 18 in the crossing area, between th connected electrodes. By adapting the current and the duration o this arc through the material disc 16, the material in th crossing area can be caused either to melt or evaporate. A hol through the material disc 16, in the crossing area, can in thi way be provided, at which the supplied energy and its duratio determines the size of the hole and its surface quality. Mor than one net thread 17 can simultaneously be connected, at whic several spark discharges 18 can be provided at the same time.

By supplying electric energy sequentially in certain chosen ne threads 17, desired patterns of holes can in this way be provide in the material discs 16. If the graduation of the net thread 17 are adapted to the size of the holes, the holes can overla each other, at which spark discharges in adjacent crossing area

form street - shaped hollow spaces. The conductivity of th material can also be adapted to cause the spark discharge t initially occur through an earlier created ad acent hole, a which the arc takes the shortest way through the material throug the crossing area. The arc 18 can in this way "draw" a hole pat between two adjacent crossing points.

Thus it is possible to melt or evaporate desired parts of th workpiece material 6 by supplying energy sequentially t appropriately chosen net threads 17. This is shown in fig. 8. B simultaneously connecting all net threads 17 which surrounds separate material disc 16 and letting a control unit 7 connecte to a CAD-system 2, sequentially convert all crossing area representing hollow spaces or outer limiting surfaces, for corresponding cross section S-S, in the detail constructed on t CAD system, to hollow spaces 25a in the material disc 16 i question, the invention can display the geometries of t physical detail in the cross section S-S in question. This meth can be repeated sequentially by connecting all net threads, th surround the adjacent material disc, and via the control unit make them to produce the next corresponding cross - section the CAD-constructed detail. Undersired portions of the secti can in this way be removed for each material disc, so that complete three-dimensional model 3 of the detail can be manufa tured. The control unit of the apparatus should also burn o material 25b in the workpiece material, so that the operator c separate rests of the workpiece material and expose the model.

The ability of the model 3 to reproduce the geometries of the C data base depends on the thickness of the material discs 16 a the relative graduation of the eletrodes 17. The workpie material 6 can be compared with a three-dimensional grid die which material can be evaporated or melted through a controll spark discharge. The resolution of the net die thus gives t digital surface structure of the model.

An apparatus for performing this method could thus consist of frame 9 in which thin pointed contact teeth 13 are internal arranged with the same graduation as the net threads. The fra

9 should with high accuracy surround the outer limiting surfaces of the workpiece material 6, at which the contact teeth 13 projecting from the frame are caused to penetrate into the workpiece material 6 to some degree. The contact teeth 13 are in this way brougth to galvanic contact with the grid threads 17 or sufficiently close, so that energy can be transferred with a controlled spark discharge. That means that the graduation of the net threads 17 at the outer limiting surfaces of the workpiece material 6 and the thickness of the contact teeth 13 must be adapted, so that all possible tolerance results of the position of the net threads 17 with respect to the contact teeth 13 guarantee an unambiguous coupling even if the teeth 13 are not in galvanic contact with the net threads 17.

The frame should further be provided with a feeding device 4 and 5 which with high accuracy can feed the workpiece materal 6 through the frame 9, so that the contact teeth are in unambiguous contact with the net threads 17 surrounding the material disc 16 in question. The feeding device 4 and 5 should, upon actuation by the control unit 7, press the workpiece material 6 through the frame 9 so that the connections of the contact teeth 13 shift to one electrode layer at a time. The workpiece material 6 can preferably be made with such a length in the longitudinal direction, so that several models can be manufactured from one and the same workpiece.

The apparatus 1 finally should include a way of removing or in some other way eliminate remaining net threads 17 from the model 3. This can be provided by evaporating or melting the net threads 17 concurrently with that they are consumed and no longer needed in the process. Fig. 3 illustrates a way of performing this. In this embodiment the net threads 17 should have essentially the same thermal properties as the rest of the workpiece material 6. The net threads 17 can in this case preferably consist of strings 17 with low resistivity in the material disc 16. This can be provided by injecting conductive particles, e.g. powdered carbon, in thin nozzles during the manufacture of the material disc, e.g. at extrusion. Another way is to join the material

discs 16 with a conductive glue with substantially the sa thermal properties as the material discs.

It may be desired that the net threads 17 have a somewhat high melting temperature than the surrounding workpiece material, order to ensure that the conductivity of the net threads maintained during the melting of the material disc 16 in t crossing area. Fig. 6 shows the sequence, according to the arr P, at which suitable net threads 17b must be connected via t symbolically denoted circuit breakers 21a-21n in order consume, i.e. burn away, the net threads 17 in a correct way.

If the temperature conducting properties of the untreat workpiece material 6 are not sufficient for cooling the gr threads 17a, so that these remain intact after completed burni of the net threads 17b, a thermal blocking layer 22, e.g. crystalline glue with high melting point, can be applied in t dividing plane between each material disc 16. The blocking lay 22 ensures that the net threads only can be burnt from one side

This connection direction P and this blocking layer 22 ensur that the net threads 17a remains uneffected until it is longer needed in the process. Rests of the thermal blocking lay 22 will however remain, which preferably can have a very britt mechanical strength. The layer 22 will therefore not alone able to form a self-supporting structure in the areas of t workpiece material which have been evaporated or melted off, i. the layer 22 transforms to some kind of dust or powder, sin this is not supported by material discs 16.

Another way of removing the grid threads is by burning off certain amount of material at the outer limiting surfaces of t workpiece 6, so that the net threads 17 are exposed as projec ing fringes, at which removal by means of rollers, arranged abo the outlet opening of the workpiece are facilitated.

Another way is to make the net threads 17 of a thermal resistant but mechanically weak material, e.g. thin metal foi

Thin single-fibre carbon threads have also shown appropriat properties, as they are easy to bend fatigue after complete model manufacture with e.g. ultrasonics or other excitatin frequencies.

A further way of removing net threads 17 is thermal burning, a which every net thread 17 has to be in galvanic contact at bot ends with a power supply circuit. The inner resistance of th threads will very rapidly cause a burning of the thread, whic does not necessarily effect the surrounding material due to th big difference in mass and cooling effect.

Another way according to the invention is shown in fig. 7 wher the longitudinal direction of the net threads parallel with th feeding direction of the workpiece material 6 out of th apparatus 1, and where end surfaces of the threads 17 located i the material block form electrode surfaces. This principl implies that the apparatus 1 can draw the net threads 17 out o the workpiece material in a controlled way. Each net thread 1 is electrically insulated from the environment with e.g. lacquer layer. Both end surfaces of the threads 17 are howeve uninsulated. At one free end of the grid threads 17 there is b that created a point-shaped electrode surface within th workpiece material 6, which through relative movement between th thread 17 and the workpiece material 6 can be positioned anywher in the workpiece material 6.

All grid threads 17 are at its other end attached to a contact block 23, which also allow galvanic connection of the grid threads via connection means 26 to a control unit 7. For eac position of the free net thread ends within the workpiec material 6 it will thus be possible to provide a spark discharg 18 and by that generate hollow spaces 25. The device should thus step for step draw out the net threads through a relative mσve- ment between the contact block 23 and the workpiece material 6.

The advantage of the last mentioned apparatus is that the finished models directly are free from remaining net threads 17.

The disadvantage is that the number of net threads is co siderably larger than required in the first mentioned principle

According to another embodiment of the invention shown in fig. the treatment tool 36 is movable in X - and Y - direction (arro C and D) along a holding-on plate 37, which also is an electro plate. Untreated material disc, e.g in the form of a continuo band 16 is fed stepwise from a roll 28 (arrow A) in a positi behind the holding-on plate 37, as seen from the tool 36, a holds e.g by means of vacuum, the material disc 16 against t holding-on plate 37. 'The control unit, not shown, controls t tool 36 in the X- and Y - direction by means of a servo means in a path 25 corresponding to e.g. the outlines of the cro section in question of the object, by means of data from the CA system. The tool 36 is then capable of either separating materi e.g. through melting or evaporation, or joining materi together, e.g. through thermal curing and/or sintering, to a di section, not shown in fig. 9, which in all essential detai reproduces the shape in question of the object.

After finished treatment , the stamp 32 with the unfinished mod 31, is brought to contact with the finished disc section (arr B). Thus this finished disc section will be pressed between t outermost and last mounted disc section of the model 31 and t holding-on plate 37. By e.g. supplying heat from the holding- plate 37 with built-in resistance heating, a melting glue on t latest finished disc section can join said disc section with t earlier produced staple of disc sections 31.

Thus it is possible, according to this method, to treat join together a model disc after disc, said model digital reproduces the geometries of the CAD-data base. After comple joining the finished model can be released from the appara e.g. by interrupting a vacuum suction between the model and assembly plate 32.

These different solutions of transporting the material discs rest products 39 and model 31 allow different kinds of treatme

Only a few embodiments are shown in the drawings

Fig. 10 shows treatment of the sections 16 by means of an arc 1 caused by a spark-over between a spark electrode 42 in the too 36 and an electrically conductive foil layer 43 on the backsid of the material disc 16. The holding-on plate 37 should then hav an optimated electrical and thermal resistance, so that the ar 18 is not disturbed or in any other way is effected negatively The supplied energy in the arc 18 and the movement speed of th servo means 29 will then effect the geometry of the treate hollow space 25.

A sliding contact 41 connected to e.g. electrical earth via th cable 40 enables the creation of an electrically closed syste between the foil layer 43 and the spark electrode 42.

The tool 36 could also be an energy-radiating means, e.g. a lase gun which emits a well focused beam. The energy of the beam mus then be adapted so that a suitable hollow space 25 can b provided through melting or evaporation. The holding-on plate 3 should then be made of a material which is permeable for th laser beam and which has a sufficient thermal resistance, e.g quartz glass.

Another apparatus for thermal treatment of the material discs i shown in fig. 11. In this embodiment the servo means has bee replaced with an electrode die which is fixed with respect to th material disc, or a grid of conductive rods 42, e.g. spar electrodes, which can be sequentially connected with control dat from the control unit, not shown, in the cable 45 via series/ parallel converting drive circuits 44. In this embodiment holder - on plate 37 or a foil layer 43 makes the counte electrode.

A further embodiment is shown in fig. 12 where a simpl accessories makes it possible to use a common standard flatbe plotter 46 as converting machine according to the invention. I this embodiment the pen in the holder of the plotter 46 i

replaced by a treatment tool 36. This tool can e.g. be a spa electrode from which an arc passes to a counter electrode in t form of a fixed plate or an electrically conductive foil.

The embodiment of figs. 13 and 14 are based on a linear displaceably cam of spark electrodes 56. This can with hi speed be led by the servo device 51 immediately above the surfa of an untreated material disc. 16. Every material disc 16, whi is not joined with any other material disc before its treatment is provided with a conductive layer 43 and a thermally effectab layer of e.g. a melting glue 55 on the side of the material di which faces away from the spark eletrodes 42. These layers 43 a 55 can preferably be integrated in one and the same layer, e.g. conductive layer of melting glue.

While the servo unit 51 leads the elctrode cam 56 forwards t control unit (not shown) connect the spark electrodes 42 question, according to the geometry of the cross section question, so that arcs 18 occur between the activated spa electrodes 42 and the conductive layer 42, which is connected way of a suitable earth means (not shown). It is in this w possible at a very high speed to permanently remove the materi sections 25 of the material disc 16 that is desired. The devi can in this way treat one disc per sweep of the servo devi 51.

Thes first disc treated in this way of each new model can af completed treatment and transport by the electrode cam 56 to position aside, be gripped by an oscillating assembly plate by e.g. vacuum forces. The finished material disc can then pulled loose from the store 49 out of four gussets 52. When assembly plate 32 and the material disc held thereon h returned to their initial position the servo 51 can be restar and drive the electrode cam 56 over the next material di which by the spring device 48 has been pressed in posit against the four gussets 52, when the previous disc was pul loose. The treatment can then be repeated. A heat-radiating u 53 mounted on the servo device 51 will simultaneously with

treatment or separately heat a melting glue 55 applied on th backside of the previously treated disc.

When the treatment of the disc no. 2 is completed also the glu of disc no. 1 will be melted and ready for joining with disc no. 2. This is made through the fact that the assembly plate agai performs an oscillating movement, so that disc no. 1 will b pressed long enough against the disc no. 2 for the melting glu to join the discs together. When the assembly plate returns t its initial position disc no. 2 will be pulled loose from th four gussets 52.

The device according to figs. 13 and 14 can after that at a ver high speed repeat this sequence, at which a new material disc 1 is supplied to the model 31 for each sweep with the electrode ca 56 and the assembly plate 32. When the model is completed th vacuum force between the model and the assembly plate can b discontinued, at which the finished model and the surroundin waste material 54 can be released from the device.

When using this and other embodiments described herein, where th surrounding waste material 54 comes along with the finished mode 31, the operator must manually remove the surrounding wast material 54, which preferably is lightly attached to the mode in smaller material- sections placed by the control unit of th apparatus.

The invention is not limited to the examples of treatment processes and apparatuses described here, but a plurality o variants and combinations are possible within the scope of th invention.

Thus it is possible, within the scope of the invention, to mak apparatuses with fixed needle-shaped electrodes, instead of gri thread provided workpiece material, said needle electrode penetrate into the work piece materials and by that enabl partial evaporation or melting. It is also possible to provid workpiece materials of easily fusible homogeneous or sintere metal alloys.

It is also possible to use ceramic materials in cases where th treatment can be provided through decomposition of the materia through concentrated mechanical oscillation energy, e.g. focuse ultrasonics.

This method can very rapidly and without human interventio manufacture three-dimensional models and objects with dimen sional accuracy in an apparatus or machine, which can be place in a common office environment. It should be possible to marke the equipment and the material disc to a relatively low cost an the method should therefore give the opportunity to man constructors, designers and architects to have a direct access t the invention at their work place.