A 3D Printer for Printing a Building This invention relates to a 3D printer for constructing a building, and is relevant to the fields of additive manufacture and masonry construction.
It has been proposed to construct buildings using a 3D printer using sand and a binding agent, with a printer having a print frame that surrounds the print volume. This type of printer is expensive and heavy and it is desired to alleviate this problem. FigureS shows an example of this type proposed by Contour Crafting of the University of South California.
According to a first aspect of the present invention there is provided a 3D printer being sized and adapted to additively manufacture a building suitable for human habitation as set out in claim 1, and in particular the print arm is adapted to pivot about a non-horizontal axis centred substantially at the print arm support, such that the print arm sweeps substantially horizontally and circumferentially across the print area.
This has the advantage that it is no longer necessary to have an expensive printer frame that surrounds the print volume.
Optionally the print head comprises a row of print heads or an elongate print head, extending generally radially away from the print arm support and along the print arm. This can speed up printing compared to a single dot' print head.
Preferably the print head is provided with radial position adjustment means adapted to control movement of the print head in a radial direction with respect to the print arm support. This allows the printer to accommodate non-circular printing areas immediately adjacent to obstructions such as buildings, lamp-posts) walls) trees etc. Preferably the print arm support is distal from a first tip of the print arm, and the print head is at the first tip of the print arm, at least when the print head is adjusted radially away from the print arm support. This has the advantage that the printer can print a building in close proximity to neighbouring objects such as other buildings.
The printer may have an adjustable counterbalance) to compensate for the radial movement of the print head. This reduces the necessary actuator forces) and in the case of a pillar embodiment will help prevent the pillar tipping over despite being quite narrow. E.g. less than 3m wide (10'), preferably less than 1.Sm (5') wide.
The means for raising the print arm may comprise means for raising the pitch of the print arm with respect to the print arm support about a pivot at the print arm support. This has the advantage of being simpler to implement) and it leads to arrangements where the print arm support is outside the print area, making it convenient to arrange building material supplies adjacent the print arm support.
The means for raising the print arm may comprise a support column arranged to allow the print arm to be raised along the support column. This avoids the need for the printer to print non-flat or non-horizontal layers, which may be challenging.
The print arm support may be located within the print volume, and the column may be provided in sections for ease of disassembly within the building after it has been completed.
The means for raising the print arm may comprise a climbing robot adapted to climb the building as it is being additively manufactured. This may be preferable as it may reduce the cost of the printer.
S There may be provided a sensor for measuring the position of the print head. This is useful as it reduces the need for accurate printer arm movements, as they can either be corrected in real-time, or the printing pattern can be corrected for errors in the arm position.
The sensor may include at least one optical distance measurement device, such as a light or IR range finder or a video motion capture system.
The circumferential motion of the print arm may include repeated full rotations in one direction, especially if the pivot is within the print area -although this requires careful design of the building materials conveyor] so that it can accommodate successive twists as shown in figure 1 (if only one material needs to be conveyed in a pipe this can be accommodated by providing the pipe with a pipe connector that permit relative rotation of two sections of pipe in the vicinity of the print arm support, while ensuring the conveying means will not be in the way of the print arm as it rotates (E.g.
by routing the pipe up inside a pillar. If multiple materials must be conveyed, this requires a complicated or conveying means connection at the print arm support -one example being a coaxial conveyor means and a connector adapted to permit relative rotation of two sections of the coaxial conveyor means, another example suitable for powder conveyors is a section where powder pours from one conveying means to another, and pouring is controlled by location or timing such that the building materials are kept separate).
Alternatively the circumferential motion of the print arm may be oscillatory, especially if the pivot is located outside the print area. In the latter case, printing may occur on both the forward and return sweep or alternatively in just one direction. This has the advantage of enabling simple and cheaper conveying means for conveying the building material(s). In most embodiments, the rate of flow of building construction material preferably varies, being greater at larger distances from the pivot at the print arm support.
There may be more than one arm, in which case the print head support is preferably within the print area, and may be a pillar, for example a beam may support two print arms cantilevered either side of the print head support, or there may be three or more print arms distributed as spokes around the pillar.
More generally the print arm does not strictly need to be a thin straight beam, and need not be strictly radial with respect to the print arm support. For example it could be contemplated that the print arm supports a component that extends in two dimensions rather than one, for example a disk, cone or dome shaped component. This component may have spoke shaped, spiral or indeed arbitrarily distributed print heads, and the term print arm is intended to cover such situations (noting that a notional print arm can be identified within such a component extending from the print arm support to a specific print head). Also the print arm may have one or more joints or be flexible in a predefined manner, for example having a vertical axis pivot midway along it, allowing it to readily sweep across a rectangular print area. Preferably however the print arm is substantially beam shaped. The beam may be a latticed boom and may be supported by guy lines.
The print arm advantageously has the ability to extend pivotally or more preferably telescopically, and preferably its weight, or torque is counteracted by a counterweight on the far side of the print arm support. Extension may be achieved by providing the print head(s) on the distal of two components that are adapted to controllably extend telescopically along a mutual sliding contact path (including via bearings etc), which may include sliding the distal' part inward up to and beyond the pivot at the print arm support (into the region of a counterweight) however three or more such components may enable greater telescopic extension. Preferably both or more preferably all sections of such a telescopic print arm are provided with print head(s).
According to a second aspect of the invention there is provided a method of additively manufacturing a building suitable for human habitation, comprising the steps of: Providing a 3D printer with: A print arm support, A print arm arranged on the print arm support, the print arm arranged to pass across a print area, At least one print head arranged on the print arm, the print head being adapted to selectively deposit layers of building construction material to additively manufacture a building, Means for raising the print arm, Conveying building construction material and a binding agent to the at least one print head, and Electronically controlling the lateral motion and raising of the print arm and the at least one print head, to additively manufacture a building in accordance with a computer model thereof, Wherein the method has the further step of: Pivoting the print arm about the print arm support, such that the print arm sweeps substantially horizontally and circumferentially across the print area.
According to a third aspect there is provided a computer program for controlling the apparatus of the first aspect to perform the method of the second aspect. According to a fourth aspect there is provided a computer readable medium containing the computer program of the third aspect.
According to a fifth aspect there is provided a unitary laminar building formed of the method of the second aspect.
Brief description of the drawings.
For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is an illustration of a 3D printer according to one embodiment of the invention.
Figure 2 is an illustration of a 3D printer according to a second embodiment of the invention.
Figure 3 is an illustration of a 3D printer according to a third embodiment of the invention.
Figure 4 shows a climbing robot for use with a 3D printer according to a fourth embodiment of the invention.
Figure 5 shows a known prior art 3D printer for constructing a building.
Description of the preferred embodiment and best mode.
An embodiment of this invention will now be explained with reference to the drawings. Figure 1 shows how a building 4 can be constructed by erecting a pillar 3 in the middle of a building plot, with a print arm 2 extending radially from it. By pivoting the arm around the pillar the print head 1 sweeps across the print area and sequentially lays down layers of construction material to build up the building. This contrasts with the prior art approach shown in figure 5 where the print arm moves without rotating and is supported at either end.
In the present invention the print arm is supported at a proximal end, and preferably is freestanding at the distal end, in particular is self-supporting in the absence of a dedicated print arm support at the distal end (unsupported except perhaps guy lines back towards the proximal end, and or by the structural integrity of the print arm itself, or by resting on the building itself). If the distal end of the print arm supports itself wholly or in part by resting on the newly printed top layer of the building) this may requires a roller or similar which can be supported at sparse and varying locations corresponding to polygonal shaped walls. A roller or other compression means may optionally be used to apply pressure to the newly printed top layer which may improve the integral strength of the building structure, however care is needed to prevent the roller from squashing newly laid fluid material off from the tops of walls and other structures, if the building material used is susceptible to this effect. To avoid applying side forces to the top layer of the building, the roller is preferably conical and/or made of a plurality of rollers that can turn at differing speeds. Use of such rollers may optionally be used to control and/or measure lateral movement of the print arm.
As shown, the print head may be a row of print heads, or an elongate print head 1. This speeds up printing as an entire layer can be laid in one movement. However similarly the print head may be adapted to move radially outward. This could be to enable the printer to print larger buildings, but more typically it is useful to avoid the problem that neighbouring buildings, trees, lamp-posts, walls etc might otherwise get in the way of the movement of the print head and print arm. Alternatively, if a single point' print head is used, the radial movement can be used to allow the print head access to all positions in the print area.
Other arrangements are possible to allow for radial movement of the print head, for example in figure 3 where the print head 1 is on a secondary arm which in turn rests on the primary arm 2, in turn on the support 3.
Figure two illustrates how the print arm can be tilted upward, i.e. its pitch can be varied, such that the height of the print head is controlled without the need of a pillar. Instead the print arm is controlled to pivot at the print arm support 3. This means that the building is not built up in strictly horizontal layers, however it simplifies the printer design. Typically the print arm support is not located within the print area, which has the added advantage that a supply of building materials can be more conveniently connected and arranged proximal to the print arm support. For example hoppers of sand, cement and a water supply can be connected adjacent the print arm support instead of being connected by lengthy tubing.
As the positional accuracy of the print head is least at the radially outer parts of the print area, it may be useful to detect the print head or print arm position using one or more sensors 5, as shown in figure 3. These may be video, laser, infrared, ultrasound or any similar means for detecting or triangulating the location of the print head or print arm in two dimensions or three. The sensor may be at the side of the building plot, detecting a marker located on the print arm, or vice versa. Position data is used to adjust the printing schedule in real-time so that positioning errors are compensated for.
Figure 4 shows how the vertical raising of the print arm can be achieved by providing a climbing robot adapted to climb a predetermined guiding part of the building, as the building is being built.
For example this might be in the form of the end of a wall, or a groove in a wall. This however does require the print head to be able to deposit material quite close to the axis about which the print arm pivots. Conveniently, the climbing robot may be provided with a start section of this guide) which may be dug into or otherwise arranged below the height at which printing is to begin. The guide is likely to add positional error, increasing the need for position detection. The robot may have a set of wheels able to clamp tightly about a rib extending from a wall or within a groove in a wall. Caterpillar tracks may be more suitable than wheels, and where used with multiple or elongate print head(s), due to the additional positional uncertainty caused by driving up a potentially uneven surface, any position detection system may preferably locate at least two widely separated points on the print arm.
The building material to be deposited is generally a fluid (which includes dry powders, powder slurry and liquids) may be in two or more parts, such as sand, cement and water provided separately to the print head(s). The parts may be non-aqueous substances which react together to harden as described in the prior art, but most preferably may include a ceramic, a binder and water. The parts may include additives to achieve various goals, and different materials may be selectively deposited in accordance with the computer model. The parts may be mixed prior to being conveyed to the print head by conveying means 7, or they may be mixed at the print head prior to dispensing) or they may be printed separately and contact each other upon being printed upon one another. The materials may be conveyed in any convenient manner, for example liquid and slurry can be pumped along a pipe, powder can be blown along a pipe, and difficult to transport materials can be conveyed on a conveyor belt or via conveyor tubing, such as a tubular drag conveyor or a screw conveyor or a flexible pipe conveyor. Preferably they may be conveyed from a source (such as a hopper or mixer) along the ground to the print arm support, up and along the print arm to the print head(s). However equally it is possible to arrange tubing/piping that conveys materials from above the print head, at a fixed location, e.g. a hopper on an adjacent building or on a scaffold, via a path that may not include the print arm support, so that the material flows downward to the print head. This can make it easier to transport powders and slurry. The building material may be provided as a single substance or a pre-mixed fluid that hardens or solidifies over time, or in response to exposure to air, light and/or heat. Preferably the building construction material consists of at least one type of ceramic powder and at least one binding agent. Suitable construction materials include but are not limited to cement, mortar, concrete and similar hardening ceramic substances as have been described in the known art, which may be pre-mixed or mixed in situ. The building material need not be exclusively ceramic and aside from the addition of additives, the printer may be adapted to selectively deposit substances other than the main building material, which together form a unitary laminar building structure.
The term circumferential means pivoting so that the print heads can move in an arc about the print head support. The term print head encompasses means for separately depositing two or more materials upon one another so that they bind together.
The printer may deposit sacrificial material (in bulk or otherwise) which may be removed after completion of the building. Depositing sacrificial material enables flat level ceilings to be conveniently printed without risk of collapse during the printing process. Preferably the sacrificial material, if any, does not fill the entirety of the building, and more preferably the printing method largely avoids, or ideally entirely avoids the need for deposition of sacrificial material, for example utilising arched ceiling building designs.
In a best mode embodiment, the print arm support is located outside the print area and is controlled to rotate less than a full turn, in a back and forth fashion, which permits placement of hoppers for S building materials to be placed adjacent the print arm support, where they can be conveniently topped up by a user during printing. The printer has a row of print heads adapted to separately dispense at least cement and water so that the cement and water are mixed in situ. The mixture may have various additives to improve the structural qualities of the printed structure, for example those that are described in the literature or known in the fields of mortar, cement and concrete manufacture and of additive manufacture of buildings. The water is sprayed non-vertically, and slightly after dispensation of the cement (by laterally offsetting the cement dispenser and the water dispenser), such that any cement that falls from its intended location will not harden below on the floor adjacent. Alternatively the cement and water are mixed within a combined material dispensing nozzle. The row of print heads is on a section of the print arm that is adapted to move radially to and away from the print arm support, so that the printer can at all times reach as far as necessary but without extending beyond the print area, so that it's movement is not obstructed by any neighbouring buildings (or trees or street furniture) that may be adjacent to the planned building.
The print arm support is arranged to position the print arm substantially horizontally and at a low level at the beginning of the printing process, so as to be flush with the foundations of the planned building as this avoids having to print only with the tip of the array of print heads at the beginning of the print process (which would be slower). The printer may even me controlled to dispense building materials into dug foundations, so as to fill the foundations even though it may be problematic to arrange the print heads near to the bottom of those foundations -this may be acceptable because accurate printing may not be required for filling pre-dug foundations.
As the printing process progresses, the print arm is tilted upward to enable it to print successive layers -these layers will not be horizontal layers. The print arm preferably has a counterweight so that powerful actuators are not required, and to enable the print arm to be flat and at ground level at the outset, but tiltable upwards during printing) the counterweight can be raised above and behind the pivot at between 20 and 70 degrees. Alternatively to aid stability, the counterweight may be adapted to pivot upward slowly during the printing process to avoid contacting the ground, or the print head support may both pivot and vertically raise the print arm, so that the print arm essentially pivots upwards about a region that is near to the counterweight (alternatively, a horizontal axis pivot can be arranged at or near the counterweight, such that the print arm support raises the print arm at the lateral pivot location -i.e. the lateral and raising pivots need not be one and the same and can be separated from one another).
As the row of print heads moves radially this is ideally compensated for by movement of other weight, which may be the counterweight, or more simply may be a second weight that moves near to and parallel to, but in the opposite direction of the moving print heads, their motion being coupled together for example by a belt loop.
Preferably there are at least two rows of print heads, that move radially with respect to one another, this has the benefit that when the radially moveable print heads are radially extended, this does not leave a blank area where the printer cannot print material and avoids the need for each layer to be completed in multiple passes. Alternatively, especially where the print head support acts to pivot the print arm upward about a region near the counterweight, it is possible for the row of print heads to be retracted back past the pivot into the region near the counterweight, avoiding the need for two sets of print heads.
S Optionally the row of print heads and the conveying means for conveying building materials to the print heads, is provided in a modular fashion having conveniently releasable end sections, so that the length of the row can be adjusted to suit the size and shape of the building that is to be constructed.
This alleviates the need for the row of print heads to move a large distance, and for many building sites a design with just one row of print heads that can retract back towards and past the pivot to the counterweight region, may be sufficient to enable each layer to be printed in one pass.
Rather than controlling the movement accurately and dispensing materials in accordance with the anticipated position/motion, it may be much better to control the movement acknowledging that it is challenging to control the arm position very accurately, and to monitor the position with sensors, and then to control the dispensation in real-time in response to accurate measurement of the position of the arm as it moves. The printer has at least one position measurement sensor, such as a set of three range finders or a set of two video capture cameras which may be integral with or closely associated with the print arm support (e.g. above and either side of the print arm support) such that the position of the end of the print arm can be determined accurately. Alternatively a single video camera on the end of the print arm may be used to track multiple markers (which may be connected to the base of the print arm support and on rigid poles extending to disparate visible locations above the print arm near the print arm support so as to be visible to the camera at all times). It is desirable to control and/or measure the position of the distal end of the print arm accurate to 25mm (1"), more preferably accurate to 5 mm (0.2"), more preferably accurately 2.5mm (0.1"). A lower accuracy may be acceptable if the same error is repeated for each layer, to achieve a smooth wall surface even if the wall is not exactly where planned. I.e. precision is more important than accuracy. For example it may not be necessary to construct a building as a whole upon its foundations more accurately than 25mm (1") in any direction, but desirable that wall surface roughness does not exceed 10mm variation (0.4") or more preferably 2.5mm (0.1"). In general, the size and density of print heads, and their printing thickness is desirably fine enabling detailed printing and accurately reproduced structures, however it need not be finer than the ability to measure or control position, especially where the print heads are adapted to move radially to and away from the print arm support.
The print heads include powder print heads adapted to control a rate (or an average rate, e.g. by pulse width modulation) of dispensation.
The printer is provided with a large tent which surrounds the printer and the print volume (i.e. the printer and the planned building. This protects the printer from gusts of wind, prevents rain falling on the drying cement, and provides a degree of site security and visual shielding, reducing the likelihood of trespass such that the printer can be left alone for periods of time. Typically this will enable the user to collect and top up the supplies from a building materials supplier, or if the hoppers are large enough and enables the printer to be left unattended overnight. The printer is provided with sensors to detect when the supply of one or more building materials has run out, and to stop printing accordingly.