3D Printer for the Production of Spatial Plastic Molded Parts

Abstract

3D printing of moldings takes place by an extruder in which solid plastic is melted, the melt being discharged through a die which can be closed completely or partially or opened completely or partially and the melt which is not discharged through the die is returned into the extruder.

Claims

1.-36. (canceled)

37. A method for 3D printing, comprising: producing a melt of liquid plastic by liquefaction of a plastic that is mixed with additives, additions and fillers in an extruder; applying the liquid plastic through a die that can be closed; effecting a backflow or leakage of the melt in the extruder when the die is closed; and creating a melt tape or a melt thread or a melt strand or a melt point by extruding the melt through the die.

38. The method according to claim 37, wherein the extruder is a single-screw extruder or a twin-screw extruder or a planetary roller extruder.

39. The method according to claim 38, wherein the extruder comprises a screw or a central spindle with a tip at an extruder outlet, and wherein an outlet opening is followed by a closeable die in a flow direction of the melt.

40. The method according to claim 39, wherein the die is closed or opened by one or more of a displacement of the screw or central spindle, a movement of the die, and by a slide or a hollow shell section.

41. The method according to claim 39, wherein the die can be moved in an axial direction of the screw or the central spindle against the tip of the screw in order to completely or partially close the die and wherein the die can be moved away from the tip of the screw or central spindle in order to completely or partially open the die.

42. The method according to claim 39, wherein the die can be moved in an axial direction of the extruder to open and close.

43. The method according to claim 37, wherein the melt escaping from the die is placed on a movable base or worktable, with which all other movements for printing a workpiece take place.

44. The method according to claim 37, wherein the melt escaping from the die is deposited on a stationary building area and the extruder together with the die can be moved over the building area to produce a structure work.

45. The method according to claim 37, wherein the die is exchangeable at least at an outlet opening in order to give the melt tape or the melt thread or the melt strand or the melt point a different cross section.

46. The method according to claim 45, further comprising exchanging the die during production of a molded part.

47. The method according to claim 45, further comprising providing a linearly movable slide with at least one die opening at the outlet opening or providing a rotatable or swiveling cover with at least one die opening at the outlet opening or providing a displaceable hollow shell section with at least one die opening at the outlet opening.

48. The method according to claim 37, wherein the die includes a plurality of dies which are at least swiveling on an outlet side.

49. The method according to claim 37, wherein the die is a swiveling die, a slewability of which is provided by a spherical joint in the die.

50. The method according to claim 37, wherein a compound is used which at least partially contains a desired mixture proportion for the melt.

51. The method according to claim 37, further comprising adding a flame retardant to the plastic for producing the melt when used on building products or building structure, which are exposed to a fire load in event of a fire.

52. The method according to claim 39, wherein the extruder is arranged with the screw or the spindle being vertical.

53. The method according to claim 37, further comprising measuring a melt consumption and re-filling feed material depending on the measure melt consumption.

54. The method according to claim 37, further comprising one or more of: measuring a filling degree in the extruder; measuring a weight of an accruing molded part; measuring a distance between the accruing molded part and the die; and measuring a filling level in the extruder.

55. The method according to claim 40, wherein the screw or the central spindle has a tapering tip which extends into the die at least in the closed position of the die.

56. The method according to claim 55, wherein the die has a tapered opening.

57. The method according to claim 37, wherein the extruder is a planetary roller extruder with fewer than a full set of planetary spindles revolving around a central spindle and/or a reduced teeth trimming.

58. The method according to claim 57, wherein a number of planetary spindles amounts at least to 3.

59. The method according to claim 58, further comprising evenly re-distributing the planetary spindles between the central spindle and the surrounding housing after each change in the number of planetary spindles.

60. The method according to claim 57, further comprising reducing the teeth trimming on the planetary spindles by totally or partially removing teeth or by totally or partially interrupting teeth.

61. The method according to claim 37, further comprising re-feeding melt quantities which are not taken off for printing through a bypass.

62. The method according to claim 37, further comprising building a molded part by laying the melt tape or the melt thread or the melt strand in layers and wherein the laying the melt tape or the melt thread or the melt strand within a layer is interrupted when the melt tape or the melt thread or the melt strand adjoins a melt strand/thread/tape that has already been laid or is continued at a point where no melt strand/thread/tape has yet been laid.

63. The method according to claim 62, further comprising a line by line laying within the layers, whereat a reversal takes place when an edge of the molded part is reached.

64. The method according to claim 62, wherein the laying the melt tape or the melt thread or the melt strand takes place at transition to an adjacent line of a layer without interruption and there is a meandering course of the melt tape or the melt thread or the melt strand.

65. The method according to claim 62, wherein the melt tape or the melt thread or the melt strand is laid at junctions with other melt strands/threads/tapes in a bracing.

66. The method according to claim 62, wherein the melt tape or the melt thread or the melt strand has an offset to adjacent melt strands/melt tapes/threads of at least 1 mm.

67. The method according to claim 62, wherein during construction of a wall a direction of laying the melt tape or the melt thread or the melt strand is adapted to a course of the walls.

68. The method according to claim 37, further comprising producing buildings or structural parts and creating hollow spaces in outer walls.

69. The method according to claim 68, further comprising: producing an outer layer and an inner layer at the hollow spaces and producing hollow chambers between the outer layer and the inner layer, the hollow chambers being shaped like honeycombs.

70. The method according to claim 67, further comprising: providing larger building parts with expansion joints to compensate expansion, the expansion joints being closed with joint tapes, wherein the joint tapes are welded with the building.

71. The method according to claim 67, further comprising: providing plastic windows; and welding or gluing the plastic windows to the building.

72. The method according to claim 71, further comprising: solvent welding the plastic windows.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0205] FIG. 1 shows an extrusion line.

[0206] FIG. 2 shows a feed hopper detail of FIG. 1.

[0207] FIG. 3 show an actual hopper of FIG. 1.

[0208] FIG. 4 shows a lower end of a housing.

[0209] FIG. 5 shows a cover slidably arranged in a housing of an extruder.

[0210] FIG. 6 shows a cover and an outlet opening with a tip of a central spindle.

[0211] FIG. 7 shows a cover and an outlet opening in combination with a differently shaped tip of a central spindle.

[0212] FIG. 8 shows a cover and an outlet opening in combination with a further tip of a central spindle.

DETAILED DESCRIPTION

[0213] Referring to FIG. 1, on a column 1, a swivel arm 7 is swiveling attached. The swivel arm 7 carries the motor and gear for a planetary roller part 2. The planetary roller part 2 is provided with a feed hopper 4 which has a lateral feed opening 6 in the form of a mouth. 3 denotes the inflows and outflows for heating and cooling media.

[0214] The planetary roller part 2 has a lockable outlet which will be explained below. The planetary roller part 2 has in usual design a housing, a central spindle and planetary spindles which mesh due to suitable toothing both with the central spindle and with an internally toothed liner arranged in the housing. In the execution example, the pitch diameter of the internal toothing is 30 mm. The pitch diameter of the internal toothing also identifies the construction size, here construction size 30. In other execution examples, the construction size can be larger, for example 50, or smaller.

[0215] In the execution example, the number of planetary spindles is 3. The planetary spindles are evenly distributed around the circumference of the central spindle. At a usual number of 5 planetary spindles, this includes a reduction of the planetary spindle trimming by 40%. In other execution examples, the reduction can be more or less.

[0216] There is so much distance between the planetary spindles that the extruder can keep running when the die is closed or only partially opened and the excess melt conveyed against the die flows back as a leakage flow between the planetary spindles until the planetary spindles seize the melt that has flowed back and feed it again in the direction of the die. If the die is not yet open, the backflow/leakage flow is repeated.

[0217] The backflow/leakage flow is advantageously used in order to achieve a perfect melt mixture when starting the extruder and at closed die before the die will be opened. Then it can be operated without start-up losses. The start-up loss is easier to absorb with other extrusion processes than when producing a 3D print on a base/worktable. In the case of start-up losses, insufficiently prepared melt would be deposited on the base/worktable. Or the worktable would have to be moved out of the working direction of the die and the melt loss resulting from the start-up would have to be disposed of without contamination. Contamination-free means that the system should not be contaminated by the unusable melt that occurred during starting-up.

[0218] A further advantage of the backflow/leakage is obtained when the leakage flow extends as far as possible to the feed hopper through which feed material is fed into the extruder. There is still a high friction of the solid particles. This friction is drastically reduced by the melt flowing back. The backflow/leakage acts like a lubricant between the solid particles. In addition, the mixture improves.

[0219] The printing can advantageously be carried out not only with the extruder standing vertically, but also with the extruder standing horizontally or with the extruder standing inclined. Printing with an upright/vertical extruder has the advantage that the die can be brought close to the surface on which the melt is to be deposited. This facilitates accurate printing and simplifies construction for the device. The same applies to an inclined arrangement of the base/worktable. The horizontal arrangement and movement of the base/worktable also has considerable advantages.

[0220] FIGS. 2 to 4 show not to scale details of the extrusion line according to FIG. 1.

[0221] FIG. 2 shows the feed hopper with a housing 10 which is fastened to the swivel arm 7 with an upper flange. The swivel arm carries a drive 5. A driving shaft 12 leads from the drive to the central spindle of the planetary roller part 2. The contour of the opening 6 in FIG. 2 is referred to as 11.

[0222] The FIG. 3 shows the actual hopper 15 of the material feed 4. The central spindle is labeled 16, the planetary spindles 17 and 18. The planetary spindles 17 and 18 have different lengths, so that they project into the hopper 15 at different heights. This gives the planetary spindles an advantageous feed behavior in relation to the material supplied into the hopper.

[0223] In operation, the rotating planetary spindles slide on a stop ring. The housing 22 of the planetary roller part 2 is detachably attached to the lower edge of the feed hopper 4 by means of swiveling screws. The swiveling screws make it easier to loosen and fasten by swiveling them in or swiveling them out of engagement.

[0224] FIG. 4 shows at the lower end of the housing 22 a flange 23 which supports the stop ring 25 for the planetary spindles. The central spindle ends in a tip 26, which defines the outlet opening 28 of the extruder in a screwed-on cover 24. The cover 24 forms a die with the discharge opening and a closure 29. The swivel screws 28 in turn serve as screwing for the cover. There is a rotatable closure 29 on the cover. The closure 29 can completely or partially open or completely or partially close the outlet opening 28 of the extruder. In the execution example, the closure is brought into the desired position by hand with a lever 30. There the closure can be locked with another lever 31. The arrest is locked by a screwing.

[0225] When using the above described system for 3D printing of molded parts with plastic melt, the need of melt for covering a melt thread on a base/work table or for laying on a molded part that is being manufactured is estimated by the service personnel and the outlet opening is adapted manually to the need. This can be quite accurate, because excessive amounts of melt or insufficient quantities of melt become immediately visible during printing on the construction progress of the construction part.

[0226] The base/worktable can be moved horizontally in all directions. For the horizontal movement, the base/worktable in the execution example is held in two linear guides, one of which is held in the machine frame and carries the other linear guide. In addition, in the execution example, the extruder is also held in a height-adjustable manner with the swivel arm 7 on the column 1. For this purpose, the swivel arm 7 is guided on the column 1 and provided with a not shown lift drive.

[0227] For tests, the base/worktable can be moved by hand in order to find out the optimal laying for the melt tape for each molded part. Once this optimal laying of the melt tape has been determined, the movement can be programmed into a control system for a movement drive of the base/worktable and the lift drive of the swivel arm. In another execution example, the control system is designed in such a way that it saves the data of the manual movement and retraces it upon request/at the push of a button. The movement drive for the horizontal movement can be uncoupled from the base/worktable for manual movement or can be coupled with the base/worktable for automatic movement. In the execution example, the lift drive remains coupled to the swivel arm during manual tests.

[0228] In the execution example, the drive for the horizontal movement consists of two servomotors. A servomotor is assigned to each linear guide. The servomotors are standard step-servomotors. The control system acts on both motors, and also on the lifting motor.

[0229] In another execution example, instead of the closure 29, a slide is provided for automation, which is moved by means of a step switching system. The step switching system is operated as required, whereat the melt requirement is being determined in previous test series.

[0230] In yet another execution example, the need of melt is calculated by measuring a sample and the step switching system of the slide is controlled with the data obtained.

[0231] In yet another further execution example, the need of melt is determined using a computerized 3D construction, and the step switching system of the slide in thus controlled.

[0232] FIG. 5 shows a further execution example. Instead of the cover firmly screwed to the extruder housing, a cover 38 is provided which is slidably arranged in the housing of the extruder. The cover 38 is guided to a not shown boring of the housing and at the same time sealed against undesired melt leakage. In the execution example, the seal is formed by a membrane made of spring steel. The resilience of the membrane is designed for the necessary adjustment way of the cover 38 to open and close the die.

[0233] The cover 38 has a computerized adjustment drive. The cover forms a die with the opening 50. The adjustment of the cover 38 serves to control the opening gap between the conical opening 50 of the cover 38 and the conical tip 35 depending on the requirement. As the demand decreases, the gap is reduced. The gap increases, as the demand increases. The requirement is determined using a computerized 3D construction. The control system of the movable cover 38 can be fed directly with the data from the calculation of requirement.

[0234] FIG. 5 also shows schematically a base/worktable 39 on which the melt escaping as a thread from the opening is laid. The base/worktable 39 can be moved horizontally in all directions and also vertically. The vertical movement is provided in order to maintain a constant distance between the melt outlet from the extruder and the surface on which the melt thread or the melt tape will be laid as the molded part grows. In the execution example, the surface is always upright/vertical under the melt outlet. When building up the molded part, this is achieved by displacing the base/worktable 39 horizontally with the growing molded part until the relevant surface lies exactly below the melt outlet.

[0235] In the execution example, the melt tape has a width of 4 mm and a thickness of 1.5 mm. The associated die is adapted to the cross section. In other execution examples, other die cross-sections are used, for example round die cross-sections. In a first layer, two melt tapes with a width of 4 mm are laid side by side to a total with of 8 mm. In the next, second layer, a die is first used, through which a melt tape with a width of 2 mm and a thickness of 1.5 mm is laid. In parallel, a melt tape with the original width of 4 mm and the same thickness is laid, aside to it another melt tape with a width of only 2 mm, so that the three melt tapes together also have a width of 8 mm. Thereby, the middle melt tape of the second layer overlaps the two melt tapes of the first layer. In the third layer, two 4 mm melt tapes are again laid aside, which overlap with the melt tapes of the second layer. The laying of 2 or 3 melt tapes is repeated in the next layers. With the overlap, the accruing wall is given a greater strength than without an overlap.

[0236] According to FIG. 5, the tip 35 of the central spindle and the outlet opening 50 have the same conicity. Thereby, the end 36 of the tip is so small that the tip 35 protrudes in closed position opposite to the cover 38 with the end 36.

[0237] However, if the end 37 of the tip 35 of the central spindle is much larger, then the end 37 of the tip lies back opposite to the cover 38 in the closed position.

[0238] FIG. 6 shows at the same cover 38 and outlet opening 50 a tip 45 of the central spindle with different conicities. At a conical shell 47 shown in dashed lines, the end 48 having a smaller area of the tip 45 can protrude through the outlet opening in the closed position, so that the lower edge touches the conical shell 47.

[0239] If, however, the tip 45 has a conical shell with the conicity 46 shown in dashed lines, the upper edge of the cover 38 contacts the conical shell 46.

[0240] In the execution example according to FIGS. 7 and 8, an identical cover 38 with the same outlet opening 50 is combined with other tips of the central spindle. FIG. 7 shows a tip 55 with a spherical end 56 which, in closed position, rests on the inner surface of the outlet opening 50. The spherical shape of the tip 55 simplifies the closing motion, as for the closing movement no plane-parallel position of the cover to the housing is no longer necessary. This also makes a swiveling movement suitable for closing the die.

[0241] FIG. 8 shows a tip 57 with a spherical end 58 which rests on the upper edge of the cover 38 due to a large diameter.