Double-fill additive manufacturing process

Abstract

A method for additively manufacturing a part using a device comprising a first deposition head and a second deposition head, said method comprising the steps of: finding (ED) the largest subpolygon symmetrical about the longitudinal axis and inscribed in a polygon; dividing (EE) the subpolygon along the longitudinal axis into a first portion and a second portion, said first portion and said second portion having substantially equal areas; adding (EF) a filling path for the first portion and a filling path for the second portion to a list of filling paths for the first deposition head and a list of filling paths for the second deposition head respectively; and performing (EJ) additively filling a part. Abstract figure: Figure 3.

Description

Title of the invention: Double-fill additive manufacturing process technical field

[0001] This document falls within the field of additive manufacturing processes and devices. Previous technique

[0002] Additive manufacturing encompasses the processes that allow the manufacturing of three-dimensional parts by adding successive layers of material one on top of the other.

[0003] Among them is fused filament fabrication (FFF) printing, which involves heating a plastic filament and depositing the molten filament onto the build plate following a layer-by-layer printing path. The layers thus created are fused together by the rapidly solidifying material, forming the final part.

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

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

[0006] - the contour which is the operation of printing the external contour(s) (the envelope) of the part. It can be made in several ways, including by juxtaposing several layers of material successively in the manufacturing plane; and

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

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

[0009] By way of illustration, the filling time of a cube with sides of 100 mm is on the order of ten hours for an additive manufacturing process with one 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 three-dimensional additive manufacturing process for at least a part of a component by means of an additive manufacturing device comprising a first deposition head and a second deposition head, said first the deposition head and said second deposition head being capable of additive manufacturing symmetrically with respect to a longitudinal axis, said process comprising the steps of:

[0012] (a) obtain a 3D model of said at least a part of a piece;

[0013] (b) perform a slicing of the 3D model of said at least a part of a piece 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 outer contour

[0015] (d) for said layer, search for the largest symmetrical subpolygon by relative to the longitudinal axis and inscribed within 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, add a filling path for the first portion and a filling trajectory of the second portion to a list of filling trajectories of the first deposit head and a list of filling trajectories of the second deposit head respectively; and

[0018] (j) perform an additive filling of said at least a part of the part according simultaneously to the list of filling trajectories of the first deposit head and the list of filling trajectories of the second deposit head.

[0019] In other words, step (j) consists of performing a double filling in an additive manner of said at least a 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 be 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 symmetrical sub-polygons 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 a filling of the layers with a reduced execution time.

[0023] Indeed, the coupling of 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 both deposition heads simultaneously and continuously for most of the process.

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

[0026] Therefore, there is no idle time for one deposit head when the other deposit head is in operation.

[0027] By substantially equal areas, we mean areas having areas equal to plus or minus 5%.

[0028] Furthermore, the step of finding the largest sub-polygon inscribed in a polygon and symmetric with respect to an axis is an algorithm with low complexity and provides coverage of a large part of the polygon. Thus, the use of this algorithm also helps to reduce execution time.

[0029] By way of illustration, the filling time of a cube with sides of 100 mm is on 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 on the order of n*log2(n).

[0031] By largest polygon, sub-polygon or rectangle, we mean the polygon, sub-polygon or rectangle with the largest surface area.

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

[0033] The sub-polygon can be a rectangle whose width or length is parallel to the longitudinal axis.

[0034] The search for the largest rectangle whose width or length is parallel to the longitudinal axis is a simple algorithm which has low complexity.

[0035] In addition, 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 device's deposit heads.

[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 made.

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

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

[0039] (h) for said layer, repeat 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 can be orthogonal to the longitudinal axis. In other words, the translation axis of the heads can 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 include an ordering of said at least two updated polygons according to their distance to the first or second deposit head, so that steps (d) to (g) are then carried out for said at least two updated polygons according to an increasing distance between to the first or second deposit head.

[0042] In other words, priority is given to repeating steps (d) to (g) for the at least two updated polygons closest to the first or second deposit head. In this way, the execution time is further optimized, as the first and second deposit heads travel a reduced distance.

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

[0044] This condition stops the subtraction of the updated polygon to prevent the creation of excessively small polygons. The threshold value therefore controls the resolution of the fill (i.e., the double fill performed by the two depositing heads).

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

[0046] By updated polygon, we mean a polygon whose surface has been trimmed 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 can be a function of the dimensions along the translation axis of the heads of the first deposit head and the second deposit head of the device.

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

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

[0051] In a particular embodiment, the threshold value may be at least equal to the sum of 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 can be at least equal to the sum of half the dimension along the translation axis of the body of the first deposit head and half the dimension along the translation axis of the body of the second deposit head.

[0053] In this way, all polygons of a layer are covered with a size sufficient 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 process may further include, between steps (h) and (j), the step of:

[0056] (i) add a path for filling the updated polygon to the list of paths filling jectories of the first deposit head or the list of filling trajectories of the second deposit 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 deposit heads, by carrying out the remaining filling of the updated polygon with a single deposit head from among the first or the second deposit head.

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

[0059] Steps (c) to (i), referred to as processing steps, may be performed for one layer of said at least one layer, and repeated for the remaining layers of said at least one layer. Step (j) then consists of performing an additive filling after having performed the processing steps for all the layers of said at least one layer.

[0060] According to one aspect, step (j) can be performed for said layer and steps (d) to (j) can be repeated for the layers of said at least one layer. In other words, the process can consist of performing the processing steps (c) to (i) for a 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), we mean 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 process includes steps (a), (b), (c), (d), (e), (f), (g), (h), (i), (j), the steps between step (b) and step (j) are understood to be 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 saves execution time on filling the 3D model of said at least a part of the part and optimizes computing resources.

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

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

[0070] Additive manufacturing by filament deposition (or "Fused Deposition Modeling" in English) allows manufacturing to be carried out with a very wide choice of materials, among They are thermoplastics.

[0071] Furthermore, it optimizes the material used compared to other additive manufacturing technologies such as laser melting. In addition, laser melting 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 process may further include a contouring phase.

[0074] The contouring phase may precede, follow, or be performed during the steps of the aforementioned process. 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 axis of translation of the heads,

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

[0079] - a first independent deposit head and a second independent deposit head, the first the depot head and the second depot head being mounted sliding on said at least a second rail and being able to translate along the axis of translation of the heads;

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

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

[0082] The computer can 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, coupling the device to the process allows for optimized filling: on the one hand, the deposition heads can manufacture additively by translating along the axis of translation 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 deposit head and the second deposit head can be of different dimensions.

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

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

[0087] The features described in this document may optionally be implemented independently of each other or in combination with each other. Brief description of the drawings

[0088] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0089] - [Fig. 1] is a schematic top view of an additive manufacturing device according to a particular embodiment;

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

[0091] - [Fig.3] is a diagram illustrating the different successive stages of a process additive manufacturing of at least part of a component according to a given 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 a part of a component during different successive stages of additive manufacturing according to the process of [Fig. 3]; Description of embodiments

[0093] Figures 1 and 2 illustrate an embodiment of the additive manufacturing device along a horizontal plane which includes 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 sliding on the first two rails 2 and extending along the transverse axis X.

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

[0097] Bridge 6 further comprises a first and a second independent depot 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 dimension 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 8b, 10b nozzle is generally conical in shape.

[0102] In operation, the depot 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 axis of translation of the heads.

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

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

[0106] A step (b) of the process then consists of performing EB a slicing of the 3D model of said at least a 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 process, 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 process of finding ED 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 Y axis.

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

[0110] During a step (e) of the process, this largest rectangle 40 is divided EE according to a axis 40c parallel to the Y axis in 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 of 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 sub-rectangles 42a, 42b are completely filled.

[0116] In other words, each sub-rectangle 42a, 42b can be imagined as a matrix: the deposit heads 8, 10 fill a row and move on to the next row 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 an optimized filling.

[0118] During a step (g) of the process, 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 process in which steps (d) to (g) are repeated for each of the subpolygons 34a, 34b, 34c, 34d of the plurality of subpolygons.

[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 length of the resulting sub-rectangles is less than a threshold value.

[0122] For example, this threshold value can be the sum of the dimensions Lxl and Lx2 of the deposit 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 simultaneously with the two deposit heads 8, 10.

[0123] During a step (i) of the process, a filling trajectory for a sub-polygon obtained at the end of step (h) is added El 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 process, an additive filling of at least a part 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

Demands

1. A three-dimensional additive manufacturing method for at least a part of a component 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 additively 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 a part of a component; (b) performing (EB) slicing of the 3D model of said at least a part of a component 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), search (ED) for the largest sub-polygon (40) symmetric with respect to the longitudinal axis (Y) and inscribed in the polygon (34);(e) for said layer (30), divide (EE) along the longitudinal axis (Y) the subpolygon (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), add (EF) a filling path of the first portion (42a) and a filling path of the second portion (42b) to a list of filling paths of the first deposition head (8) and a list of filling paths of the second deposition head (10) respectively; and (j) perform (EJ) an additive filling of said at least a part of the part according simultaneously to the list of filling paths of the first deposition head (8) and the list of filling paths of the second deposition head (10).

2. Method according to the preceding claim, wherein 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 polygon (34) the sub- polygon (40) to form at least one updated polygon; and (h) for said layer (30), repeat (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, wherein the translation axis of the heads (X) is orthogonal to the longitudinal axis (Y).

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

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

7. A method according to any one of claims 3 to 6, further comprising, between steps (h) and (j), the step of: (i) adding (E1) 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 one of the preceding claims, wherein the steps between step (b) and step (j) are carried out simultaneously for at least two layers of the 3D model of the part.

9. A filament deposition additive manufacturing process 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 axis of translation of the heads (X); - a bridge (6) mounted to slide 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); - an independent first deposition head (8) and second deposition head (10), the first deposition head (8) and the second deposition head (10) being mounted to slide on said at least one second rail (4) and being capable of translating along the axis of translation of the heads (X); - a memory for storing at least the steps of the process according to any one of the preceding claims; and - a computer having access to memory to read the steps stored in memory and execute the steps of the process according to any one of the preceding claims.

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