Double-fill additive manufacturing process

Abstract

Method for additive manufacturing of a part by a device comprising a first deposition head and a second deposition head, said method comprising the steps of: searching (ED) for the largest sub-polygon symmetrical with respect to the longitudinal axis and inscribed in a polygon, dividing (EE) along the longitudinal axis the sub-polygon into a first portion and a second portion, said first portion and said second portion having substantially equal areas, adding (EF) a filling trajectory of the first portion and a filling trajectory of the second portion to a list of filling trajectories of the first deposition head and a list of filling trajectories of the second deposition head respectively and performing (EJ) an additive filling of a part. Abstract figure: Figure 3.

Description

Title of the invention: Additive manufacturing process by double filling Technical field

[0001] This document relates to the field of additive manufacturing processes and devices. Prior art

[0002] Additive manufacturing brings together processes that enable parts to be manufactured in volume by adding successive layers of material on top of each other.

[0003] Among them, we find the printing by fused deposition of filament which consists of heating a plastic filament and depositing the molten filament on the plate following a printing path layer by layer. The layers thus created are fused together by the material which solidifies quickly and forms the final part.

[0004] Typically, a slicing step of the 3D model of the part is carried out via software. During this slicing step, the 3D model of the part to be manufactured is broken down into layers along the vertical axis of the machine (i.e. the axis orthogonal to the layers).

[0005] Each layer is then produced in two main phases:

[0006] - the contour which is the operation consisting of printing the external contour(s) (the envelope) of the part. It can be produced in several ways, notably by juxtaposing several beads of material successively in the manufacturing plan; and

[0007] - filling which is the operation consisting of manufacturing the interior of the part and allows you to control its density.

[0008] Filling is the longest operation, because the quantity of material to be deposited is generally greater than for the contour phase and the distance to be covered by a deposition head is also greater.

[0009] As an illustration, the filling time for a cube with a side equal to 100 mm is of the order of ten hours for an additive manufacturing process with a deposition head.

[0010] The objective of this document is to reduce the execution time of the filling phase. Summary

[0011] To this end, the present document relates to a method for three-dimensional additive manufacturing of at least a portion of a part by an additive manufacturing device comprising a first deposition head and a second deposition head, said first deposition head and said second deposition head being capable of additive manufacturing symmetrically with respect to a longitudinal axis, said method comprising the steps of:

[0012] (a) obtaining a 3D model of said at least one part of a part;

[0013] (b) performing a slicing of the 3D model of said at least one part of a part to divide said 3D model into a plurality of layers, each layer having an external contour;

[0014] (c) for at least one layer, determine a polygon inscribed in the external contour

[0015] (d) for said layer, search for the largest symmetrical subpolygon by relative to the longitudinal axis and inscribed in the polygon;

[0016] (e) for said layer, divide along the longitudinal axis the sub-polygon into a first portion and a second portion, said first portion and said second portion being of substantially equal areas;

[0017] (f) for said layer, adding a filling trajectory of the first portion and a fill trajectory of the second portion to a list of fill trajectories of the first deposition head and a list of fill trajectories of the second deposition head respectively; and

[0018] (j) performing an additive filling of said at least a portion of the part according to the filling trajectory list of the first deposition head and the filling trajectory list of the second deposition head simultaneously.

[0019] In other words, step (j) consists of carrying out a double filling in an additive manner of said at least one part of the part according to the list of filling trajectories of the first deposition head and the list of filling trajectories of the second deposition head.

[0020] In the case of a polygon with at least one hole, the external contour means the edges defining the shape of the polygon, and not the shape of said at least one hole delimited by at least one internal contour.

[0021] In the case of a polygon with at least one hole, an element inscribed in said polygon is understood to mean an element included in the external contour of the polygon excluding the surface of said at least one hole (i.e. the surface of the polygon inscribed in said at least one internal contour).

[0022] The coupling of the filling trajectories of the sub-polygons symmetrical with respect to the longitudinal axis and of the two deposition heads of the device extending along this longitudinal axis makes it possible to carry out filling of the layers with a reduced execution time.

[0023] Indeed, the coupling of the symmetry with respect to the longitudinal axis of the process and the additive manufacturing device makes it possible to limit the movements of the deposition heads. In other words, this reduces the distance traveled by the deposition heads.

[0024] This symmetry also offers the advantage of using the two deposition heads simultaneously and continuously for most of the process.

[0025] In other words, when one of the two deposit heads fills a portion of the sub-polygon assigned to it, the other deposit head also fills the other portion of the sub-polygon.

[0026] There is therefore no inactivity time for one deposition head when the other deposition head is in operation.

[0027] By substantially equal surfaces is meant surfaces having surfaces equal to plus or minus 5%.

[0028] Furthermore, the step of searching for the largest sub-polygon inscribed in a polygon and symmetrical with respect to an axis is an algorithm with low complexity and offers coverage of a large part of the polygon. Thus, the use of this algorithm also contributes to reducing the execution time.

[0029] As an illustration, the filling time for a cube with a side length equal to 100 mm is of the order of 5 hours for an additive manufacturing process according to this document.

[0030] The document Daniels, K., Milenkovic, VJ, & Roth, D. (1995) "Finding the largest rectangle in several classes of polygons", Harvard Computer Science Group Technical Report TR-22-95 discusses the complexity of algorithms for finding the largest rectangle which is typically of the order of n*log2(n).

[0031] By largest polygon, sub-polygon or rectangle is meant the polygon, sub-polygon or rectangle having the largest surface area (largest area).

[0032] The filling can be carried out according to at least one of the following patterns: - straight; - zig-zag; - concentric; - grids; - lines; - connected lines; - triangle; - gyroid; - cubic; - cubic quarter; - octahedral; - flash ; - trihexagonal; - cubic subdivision; - crisscrossed; - 3D crisscross.

[0033] The subpolygon may be a rectangle whose width or length is parallel to the longitudinal axis.

[0034] Finding the largest rectangle whose width or length is parallel to the longitudinal axis is a simple algorithm with low complexity.

[0035] Furthermore, the choice of a rectangle whose width or length is parallel to the longitudinal axis allows alignment with at least one translation axis of the deposition heads of the device.

[0036] In this way, the efficiency of the filling phase is improved by searching for the largest rectangle inscribed in the polygon defining the layer to be manufactured.

[0037] The method may further comprise, between steps (f) and (j), the steps of:

[0038] (g) for said layer, subtract from the polygon the sub-polygon to form at minus one updated polygon; and

[0039] (h) for said layer, repeating steps (d) to (g) for said at least one polygon updated until said at least one updated polygon has a dimension along a head translation axis less than a threshold value, said head translation axis forming a non-zero angle with the longitudinal axis.

[0040] The translation axis of the heads may be orthogonal to the longitudinal axis. In other words, the translation axis of the heads may form a right angle with the longitudinal axis.

[0041] Optionally, in the case where said at least one updated polygon comprises at least two updated polygons, step (h) may further comprise an ordering of said at least two updated polygons according to their distance to the first or second deposition head, so that steps (d) to (g) are then carried out for said at least two updated polygons according to an increasing distance between the first or second deposition head.

[0042] In other words, the repetition of steps (d) to (g) is prioritized for said at least two updated polygons closest to the first or second deposition head. In this way, the execution time is further optimized, the first deposition head and the second deposition head traveling a reduced distance.

[0043] In other words, step (h) makes it possible to repeat a loop, i.e. steps (d) to (g), until a condition is met, here the fact that the updated polygon has a dimension along the translation axis of the heads less than a threshold value.

[0044] This condition allows you to stop the subtraction of the updated polygon to avoid creating polygons that are too small. The threshold value therefore controls the resolution of the filling (i.e. the double filling carried out by the two deposition heads).

[0045] In this way, the polygon is filled recursively: by splitting it into a plurality of sub-polygons symmetrical with respect to the longitudinal axis.

[0046] An updated polygon is understood to mean a polygon whose surface has been cropped by the surface of the sub-polygon.

[0047] In the case of a translation axis of the heads orthogonal to the longitudinal axis, by dimension along the translation axis of the heads of a polygon, we mean the length or width parallel to the translation axis of the heads of the smallest rectangle in which the polygon is inscribed.

[0048] The threshold value may be a function of the dimensions along the translation axis of the heads of the first deposition head and the second deposition head of the device.

[0049] The deposition heads may comprise a body and a nozzle arranged at one end of the body opposite the layer to be manufactured, the material used by the additive manufacturing emerging from the nozzle.

[0050] In this way, the creation of polygons that cannot be manufactured by the two deposition heads is avoided, i.e. polygons having a dimension along the translation axis of the heads that is too small for the two deposition heads to be able to operate without collision between their bodies.

[0051] In a particular embodiment, the threshold value may be at least equal to the sum of the halves of the dimensions along the translation axis of the heads of the bodies of the deposition heads.

[0052] In other words, the threshold value may be at least equal to the sum of half the dimension along the translation axis of the body of the first deposition head and half the dimension along the translation axis of the body of the second deposition head.

[0053] In this way, all the polygons are covered with a layer having a sufficient size to allow them to be manufactured simultaneously by the first and second deposition heads.

[0054] The dimensions along the longitudinal axis of the deposition heads can be between 60 mm and 120 mm.

[0055] The method may further comprise, between steps (h) and (j), the step of:

[0056] (i) add a fill trajectory of the updated polygon to the tra list filling paths of the first deposition head or the list of filling trajectories of the second deposition head.

[0057] This additional step makes it possible to complete the filling of an updated polygon, the filling of which was first carried out simultaneously by the two deposition heads, by carrying out the remaining filling of the updated polygon with a single deposition head among the first or the second deposition head.

[0058] In the case where the threshold value is at least equal to the sum of the halves of the di dimensions, along the translation axis of the heads, of the bodies of each deposition head, this additional step allows to complete the remaining filling of the updated polygon, because the two deposition heads cannot complete the remaining filling due to the dimensions of their bodies.

[0059] Steps (c) to (i), called processing steps, may be carried out for one layer among said at least one layer, and repeated for the remaining layers of said at least one layer. Step (j) then consists of carrying out a filling additively after having carried out the processing steps for all the layers of said at least one layer.

[0060] According to one aspect, step (j) may be performed for said layer and steps (d) to (j) may be repeated for the layers of said at least one layer. In other words, the method may comprise performing the processing steps (c) to (i) for one layer, then performing the filling step (j) of said layer, and repeating steps (c) to (j) for the remaining layers of said at least one layer.

[0061] The steps between step (b) and step (j) can be carried out simultaneously for at least two layers of the 3D model of said at least one part of the part.

[0062] By the steps between step (b) and step (j) is meant the steps between step (b) and step (j), steps (b) and (j) being excluded.

[0063] In other words, by the steps between step (b) and step (j), we mean the steps carried out after step (b) and before step (j).

[0064] In the case where the method comprises steps (a), (b), (c), (d), (e), (f), (g), (h), (i), (j), the steps between step (b) and step (j) are understood to mean steps (c), (d), (e), (f), (g), (h), (i).

[0065] In other words, the steps between step (b) and step (j) can be carried out in parallel for at least two layers of the 3D model of said at least one part of the part.

[0066] Given the low complexity of the algorithms used, this parallelism requires little computing power.

[0067] This makes it possible to save execution time on filling the 3D model of said at least one part of the part and to optimize the computing resources.

[0068] The method may be a metal additive manufacturing method (for example by bonding by deposition of metal material, by deposition of metal wire or deposition of metal powder).

[0069] The method may be an additive manufacturing method by filament or granule deposition.

[0070] Additive manufacturing by filament deposition (or “Fusion Deposition Modeling” in English) allows manufacturing to be carried out with a very wide choice of materials, among which: them thermoplastics.

[0071] In addition, it optimizes the material used compared to other additive manufacturing technologies such as laser fusion. In addition, laser fusion has a higher cost than additive manufacturing by filament deposition.

[0072] It also offers a short production time compared to other additive manufacturing technologies such as powder deposition.

[0073] The additive manufacturing method may further comprise a contouring phase.

[0074] The contouring phase may precede, follow, or be performed during the steps of the aforementioned method. In other words, the contouring phase may precede, follow, or be performed during the filling phase.

[0075] This document may also relate to an additive manufacturing device comprising:

[0076] - at least one first rail extending along the longitudinal axis;

[0077] - at least one second rail extending along the translation axis of the heads,

[0078] - a bridge mounted to slide on said at least one first rail and capable of translating according to the longitudinal axis, said at least one second rail being mounted on said bridge;

[0079] - a first deposition head and a second independent deposition head, the first deposition head and the second deposition head being slidably mounted on said at least one second rail and being capable of translating along the translation axis of the heads;

[0080] - a memory for storing at least the steps of the method according to the aforementioned type; and

[0081] - a computer having access to the memory to read the steps stored in the memory and perform the steps of the method according to the aforementioned type.

[0082] The computer may be a single-core or multi-core processor (such as a central processing unit (CPU)), a graphics processing unit (GPU), a microcontroller, a programmable logic circuit (such as an application-specific integrated circuit (ASIC)), a field-programmable gate array (FPGA), a programmable logic device (PLD), a state machine, or a logic gate or discrete hardware components.

[0083] In this way, the coupling of the device to the process allows optimized filling: on the one hand, the deposition heads can manufacture additively by translating along the translation axis of the heads and, on the other hand, the deposition heads mounted on the second rail which is mounted on the bridge can manufacture additively by translating along the longitudinal axis.

[0084] The first deposition head and the second deposition head may be of different dimensions.

[0085] The first deposition head and the second deposition head may comprise a circular section along a cutting plane parallel to the longitudinal and transverse axes.

[0086] The first deposition head and the second deposition head may comprise a section rectangular or square following a section plane parallel to the longitudinal and transverse axes

[0087] The features set forth in this document may, optionally, be implemented independently of one another or in combination with one another. Brief description of the drawings

[0088] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

[0089] - [Fig.l] is a schematic top view of an additive manufacturing device according to one embodiment;

[0090] - [Fig.2] is a schematic front view of a part of the manufacturing device additive of [Fig.l];

[0091] - [Fig.3] is a diagram illustrating the different successive stages of a process additive manufacturing of at least a portion of a part according to one embodiment; and

[0092] - [Fig.4], [Fig.5], [Fig.6] and [Fig.7] are schematic top views of a same layer of a 3D model of said at least one part of a part during different successive stages of additive manufacturing according to the method of [Fig.3]; Description of the embodiments

[0093] Figures 1 and 2 illustrate an embodiment of the additive manufacturing device along a horizontal plane which comprises a longitudinal axis Y and a transverse axis X orthogonal to the longitudinal axis Y (top view) and a vertical plane orthogonal to the horizontal plane (front view) respectively.

[0094] In this particular example, the additive manufacturing device 1 is a filament deposition additive manufacturing device.

[0095] This comprises two first rails 2 parallel to each other and extending along the longitudinal axis Y, a bridge 6 mounted to slide on the two first rails 2 and extending along the transverse axis X.

[0096] The bridge 6 comprises a second rail 4 extending along the transverse axis X.

[0097] The bridge 6 further comprises a first and a second independent deposition heads pendants 8, 10 each mounted sliding on the second rail 4.

[0098] As shown in [Fig.2], the deposition heads 8, 10 each comprise a body 8a, 10a, a nozzle 8b, 10b mounted on the body 8a, 10a and a heating block (not shown). Each deposition head 8, 10 is intended to be traversed by a plastic filament intended to be heated by the corresponding heating block, the molten plastic material flowing through an orifice 8c, 10c of the nozzle 8b, 10b.

[0099] The bodies 8a, 10a are respectively of dimensions Lxl, Lx2 along the axis transverse X.

[0100] In [Fig.2], Lxl < Lx2. It is understood that other embodiments may have Lxl > Lx2 or Lxl = Lx2.

[0101] Each nozzle 8b, 10b is of generally conical shape.

[0102] In operation, the deposition heads 8a, 8b can translate along the transverse axis X on the second rail 4 and along the longitudinal axis Y by sliding the bridge 6 on the first two rails 2.

[0103] The transverse axis X forms the translation axis of the heads.

[0104] A diagram of a method for additive manufacturing at least a portion of a part according to one embodiment is described below with reference to [Fig.3].

[0105] During a step (a) of the method, a 3D model of said at least one part of a part to be manufactured is obtained EA by the additive manufacturing device 1.

[0106] A step (b) of the method then consists of carrying out EB a slicing of the 3D model of said at least one part of the part to divide said 3D model into a plurality of layers, each layer 30 being delimited by an external contour 32.

[0107] During a step (c) of the method, a polygon 34 inscribed in the external contour 32 is determined EC for at least one layer 30.

[0108] Reference is now made to [Fig.4] which illustrates a step (d) of the method consisting of searching ED for the largest rectangle 40 whose length 40a or width 40b is parallel to the longitudinal axis Y and inscribed in the polygon 34. Here, the length 40a is parallel to the axis Y.

[0109] In particular, this larger rectangle 40 is symmetrical with respect to the Y axis.

[0110] During a step (e) of the method, this larger rectangle 40 is divided EE according to a axis 40c parallel to the Y axis into a first and a second sub-rectangles 42a, 42b of substantially equal areas, as illustrated in [Fig.5].

[0111] In other words, the largest rectangle 40 is divided into two sub-rectangles 42a, 42b along its axis of symmetry 40c (the median 40c of its width 40b) along the longitudinal axis Y.

[0112] A step (f) of the method consists in adding EF a filling trajectory of the first and second sub-rectangles 42a, 42b to a list of filling trajectories of the first deposition head 8 and a list of filling trajectories of the second deposition head 10 respectively.

[0113] In operation, the filling of each sub-rectangle 42a, 42b is thus distributed to each of the deposition heads 8, 10.

[0114] In operation, the deposition heads 8, 10 respectively produce a width 42a-1, 42b-1 of each sub-rectangle 42a, 42b by translation along the transverse axis X.

[0115] The bridge 6 then translates along the longitudinal axis Y, so that the heads of deposit 8, 10 can be manufactured again by translation along the transverse axis X, and so on until the sub-rectangles 42a, 42b are completely filled.

[0116] In other words, each sub-rectangle 42a, 42b can be imagined as a matrix: the deposition heads 8, 10 fill a line and move on to a next line to be filled until the matrix is ​​completely filled.

[0117] In this way, the symmetry of the filling trajectories coupled with the symmetry of the manufacturing device, more particularly of the possible translations of the deposition heads, offers optimized filling.

[0118] During a step (g) of the method, the largest rectangle 40 is subtracted EG from the polygon 34 to form a plurality of sub-polygons 34a, 34b, 34c, 34d.

[0119] [Fig.7] illustrates a step (h) of the method during which steps (d) to (g) are repeated for each of the sub-polygons 34a, 34b, 34c, 34d of the plurality of sub-polygons.

[0120] Here, we start by searching for the largest rectangle 70 inscribed in the sub-polygon 34a.

[0121] This step (h) is carried out until a width or a length of the sub-rectangles obtained are less than a threshold value.

[0122] For example, this threshold value can be the sum of the dimensions Lxl and Lx2 of the deposition heads 8, 10. In this case, the filling of the sub-rectangles is stopped as soon as it is no longer possible to carry it out with the two deposition heads 8, 10 simultaneously.

[0123] During a step (i) of the method, a filling trajectory of a sub-polygon obtained at the end of step (h) is added E1 to the list of filling trajectories of the first deposition head or the list of filling trajectories of the second deposition head associated with the first or second deposition head 8, 10 respectively. This makes it possible to complete the filling of the remaining sub-polygons with a single deposition head 8, 10.

[0124] During a step (j) of the method, an additive filling of at least a portion of the part is carried out EJ according to the list of filling trajectories of the first deposition head 8 and the list of filling trajectories of the second deposition head 10 of the device 1.

Claims

Claims

1. A method for three-dimensional additive manufacturing of at least one part of a part by an additive manufacturing device (1) comprising a first deposition head (8) and a second deposition head (10), said first deposition head (8) and said second deposition head (10) being capable of additive manufacturing symmetrically with respect to a longitudinal axis (Y), said method comprising the steps of: (a) obtaining (EA) a 3D model of said at least one part of a part (b) performing (EB) a slicing of the 3D model of said at least one part of a part to divide said 3D model into a plurality of layers, each layer (30) comprising an external contour (32); (c) for at least one layer, determining (EC) a polygon (34) inscribed in the external contour (32); (d) for said layer (30), searching (ED) for the largest sub-polygon (40) symmetrical with respect to the longitudinal axis (Y) and inscribed in the polygon (34);(e) for said layer (30), dividing (EE) along the longitudinal axis (Y) the sub-polygon (40) into a first portion (42a) and a second portion (42b), said first portion (42a) and said second portion (42b) being of substantially equal areas; (f) for said layer (30), adding (EF) a filling trajectory of the first portion (42a) and a filling trajectory of the second portion (42b) to a list of filling trajectories of the first deposition head (8) and a list of filling trajectories of the second deposition head (10) respectively; and (j) performing (EJ) an additive filling of said at least one part of the part according to simultaneously the list of filling trajectories of the first deposition head (8) and the list of filling trajectories of the second deposition head (10).;

2. Method according to the preceding claim, in which the sub-polygon (40) is a rectangle of which a width (40b) or a length (40a) is parallel to the longitudinal axis (Y).

3. A method according to any one of the preceding claims, further comprising, between steps (f) and (j), the steps of: (g) for said layer (30), subtracting (EG) from the polygon (34) the sub- polygon (40) to form at least one updated polygon; and (h) for said layer (30), repeating (EH) steps (d) to (g) for said at least one updated polygon until said at least one updated polygon has a dimension along a head translation axis (X) less than a threshold value, said head translation axis (X) forming a non-zero angle with the longitudinal axis (Y).

4. Method according to the preceding claim, in which the translation axis of the heads (X) is orthogonal to the longitudinal axis (Y).

5. Method according to one of claims 3 and 4, in which the threshold value is a function of the dimensions along the translation axis of the heads (X) of the first deposition head (8) and of the second deposition head (10) of the device (1).

6. Method according to the preceding claim, in which the threshold value is at least equal to the sum of the halves of the dimensions along the translation axis of the heads (X) of the bodies (8a, 10a) of the deposition heads (8, 10).

7. Method according to one of claims 3 to 6, further comprising, between steps (h) and (j), the step of: (i) adding (El) a filling trajectory of the updated polygon to the list of filling trajectories of the first deposition head (8) or the list of filling trajectories of the second deposition head (10).

8. A method according to any preceding claim, wherein the steps between step (b) and step (j) are performed simultaneously for at least two layers of the 3D model of the part.

9. Additive manufacturing method by filament deposition according to any one of the preceding claims.

10. Additive manufacturing device (1) comprising: - at least one first rail (2) extending along the longitudinal axis (Y); - at least one second rail (4) extending along the translation axis of the heads (X), - a bridge (6) slidably mounted on said at least one first rail (2) and capable of translating along the longitudinal axis (Y), said at least one second rail (4) being mounted on said bridge (6); - a first deposition head (8) and a second deposition head (10) independent, the first deposition head (8) and the second deposition head (10) being slidably mounted on said at least one second rail (4) and being capable of translating along the translation axis of the heads (X); - a memory for storing at least the steps of the method according to any one of the preceding claims; and - a computer having access to the memory to read the steps stored in the memory and execute the steps of the method according to any one of the preceding claims.

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