Patent Application
20180126629
The present invention relates to additive manufacturing.
Additive manufacturing—also called 3D printing—has become an important product development tool. Rapid prototyping, iterative design and concept validation are three disciplines that are considerably facilitated by 3D printers. Several different 3D printing platforms are commercially available in the market today, and each of these platforms have important characteristics and advantages that a product developer may exploit to create design models, demonstrators, functional prototypes and small batches of components for product validation. However, currently available 3D printers share an important set of limitations that are preventing use of 3D printing technologies in mass manufacturing of components.
In mass manufacturing, a high yield is an important way to reduce manufacturing costs. For the purpose of mass manufacturing, monitoring the manufacturing process is important. However, like any manufacturing equipment, 3D printers may produce products that are different from the intended result. This may be due for instance to wear or to changes in the properties of the raw materials that are used or to temperature variations in the manufacturing facility. The result is a quality issue. In most cases, there is a tolerance interval within which the manufactured product is considered compliant. Outside the tolerance interval, the product fails to meet the standard and must be discarded.
Patent specification EP 2 186 625 discloses a system and method for additive manufacturing where a predetermined object pattern is modified, i.e. calibrated, to correct for geometric distortion of a pattern generator in an X and/or Y plane, i.e. to compensate for optical imperfections and irregularities that may impart geometric distortion on a product. Such correction serves the purpose of ensuring that each pattern generated by the pattern generator is an accurate representation of the original object pattern.
Calibration in the X and Y planes as disclosed in EP 2 186 625 serves to ensure that each object pattern is accurately projected onto a build platform that is parallel to the X and Y planes. Thus, compliance with the desired X and Y tolerance intervals are promoted. However, geometric distortion of the product, and resulting lack of compliance with tolerance intervals, may also result from lack of control over properties influencing the plane (Z) that runs perpendicular to the build platform. Such properties may include ambience temperature, radiation exposure time length, viscosity of the reactive liquid and several other parameters that may individually or in concert influence on the thickness and/or geometry of the layer that is formed as result of the radiation. EP 2 186 625 does not address distortion resulting from variations due to one or more of these properties and furthermore does not address any methods for obtaining measures in relation to (post-processing) steps carried out after printing a product.
Improved 3D printing equipment and methods that provide an increased yield compared to present equipment and methods are desirable.
The invention provides various aspects that can assist in increasing manufacturing yield in additive manufacturing.
A first aspect of the invention provides an additive manufacturing apparatus for manufacturing a product. The apparatus comprises:
In this way, at least one fiducial marker is manufactured concurrently with the manufacturing of the product.
The rigid connection with the build surface may be direct or indirect, the latter e.g. by being in rigid connection with a printed plate or other that is in rigid connection with the build surface.
Such an additive manufacturing apparatus is a means for increasing product yield in additive manufacturing as explained further in the following.
In some embodiments, the first fiducial marker is a three-dimensional fiducial marker.
In some embodiments, the product definition file includes a first fiducial marker definition defining the first fiducial marker.
In some embodiments, the first fiducial marker is defined by a corresponding first fiducial marker definition, and the electronic controller is configured to produce a modified product definition file by combining the first fiducial marker definition file with the first product definition file, and the electronic controller is furthermore configured to control at least an intensity of the hardening radiation and motion of the build platform in accordance with the modified product definition file.
In some embodiments, the first fiducial marker is formed integrally with the product.
In some embodiments, the first fiducial marker, or the first fiducial marker together with one or more further fiducial markers, if present, are configured to enable a determination of at least one of: a set of one or more positions of one or more of the fiducial markers; an orientation of the product as manufactured; a set of one or more lengths and/or sizes and/or shapes or surface contours along one or more dimensions (e.g. one or more of x, y, z) of at least one of the fiducial markers and/or at least one of the products as manufactured; at least a first relative distance between at least a first given fiducial reference point and at least a first given product reference point in a first given plane. In some embodiments, the determination being enabled for at least one of:
In some embodiments, the electronic controller is configured to adjust the manufacturing process to at least partly counteract a difference between 1) one or more results of said determination, and 2) one or more corresponding target physical dimensions (i.e. the physical length(s) or size(s) in the respective dimension(s)) and/or target orientations derivable from the first product definition file and/or from the modified product definition file. In some embodiments, the adjusting is performed if said difference exceeds a tolerance parameter accessible to the electronic controller. Preferably, this adjusting is performed automatically.
In some embodiments, the electronic controller is configured to read a product definition file of at least one of the following types: a Stereolithography file (.STL), an Additive Manufacturing File (.AMF), a Polygon File Format file (.PLY), a Wavefront object file (.OBJ), an Autodesk 3ds Max file (0.3DS), a Virtual Reality Modeling Language file (.WRL, .WRZ), a Universal 3D file (.U3D), an Extensible 3D Graphics file (.X3D, .X3Dv, .X3Ddb, .X3Ddz, .X3Dbz, .X3Dvz,). Other format may also be applicable.
In some embodiments, the determination is carried out one or more times after manufacture of the product and/or after carrying out one or more subsequent post-processing steps, e.g. after manufacturing and additionally after one or more subsequent post-processing steps.
The post-processing steps typically happen after completion of the additive manufacturing process, and examples of such processes include one or more of the following:
It may be important to carry out the determination at one or more of such post-processing steps as they may also influence the shape of a manufactured product, e.g. causing it to no longer be in compliance with one or more tolerance limits.
In some embodiments, the first fiducial marker together with one or more further fiducial markers, if present, are printed on a printed plate where the first fiducial marker together with one or more further fiducial markers, if present, are configured to allow stacking of the printed plate with other printed plates.
A second aspect of the invention provides a method for additive manufacturing of a product.
The method comprises:
The method is advantageously carried out with an apparatus in accordance with an embodiment of the first aspect of the invention. Other apparatuses configured suitably may alternatively be used.
Again, the rigid connection with the build surface may be direct or indirect, the latter e.g. by being in rigid connection with a printed plate or other that is in rigid connection with the build surface.
In some embodiments, the first fiducial marker is a three-dimensional fiducial marker.
In some embodiments of the method, the one or more fiducial markers are incorporated into a first product definition file defining the product.
Some embodiments of the method further comprise providing a modified product definition file by combining a first product definition file defining the product with a fiducial marker definition file defining the one or more fiducial markers.
Some embodiments of the method comprises manufacturing 2, 3, 4 or more fiducial markers that are configured to allow a stacking of a plurality of products manufactured during corresponding 2, 3, 4 or more manufacturing processes.
Some embodiments of the method comprise:
Tolerances such 0.025%, 0.5%, 1%, and 5% are examples of tolerances each of which might be suitable in a practical situation. The tolerance criterion may alternatively or additionally involve a trend analysis or other statistical analysis of at least one of the one or more measured physical dimensions and/or positions and/or orientations.
Some embodiments comprise performing the method and embodiments thereof after various steps in a manufacturing process and/or one or more post-processing processes.
Measuring and comparing relative distance(s) may e.g. reveal that a printed plate or other, upon which the products (and fiducials) are manufactured, has warped, become bent, etc.
The controller may be connected to the additive manufacturing apparatus via a data interface, or it may be built into the additive manufacturing apparatus.
The shown additive manufacturing apparatus 100 is a so-called top projection additive manufacturing apparatus. Manufacturing one or more fiducial markers concurrently with one or more products may also be done by other types of additive manufacturing apparatuses, e.g. by a bottom projection additive manufacturing apparatus such as shown in
In this case, the fiducial markers have been placed in such a way that each fiducial marker 202a, 202b, 202c, and 202d has at least a first certain predetermined relative distance 210 relative to at least a first reference point on each particular product 201a, 201b, 201c, and 201d. By measuring a) a set of positions, shapes or surface contours, and/or heights of one or more fiducial markers and ensuring their compliance with the tolerance limits e.g. defined in a fiducial marker definition file, and b) measuring said relative distance 210 between a fiducial marker and a product, compliance to the tolerance limits defined in the product definition file may be verified.
In principle, one fiducial marker (according to a determined convention) may be sufficient, but using more fiducial markers reduces uncertainty through the use of e.g. triangulation or similar methods of metrology. For more complex product geometries, multiple reference points and relative distances in multiple planes may furthermore be used. The products (and fiducial markers) are supported by a printed plate 205 being located on a build platform (see e.g. 105 in
In some embodiments, the fiducial markers are 3D fiducial markers, i.e. they have a detectable extent in the x, y, and z directions (or another corresponding 3D coordinate system). The detectable extent may vary according to a given use or purpose, and does not necessarily need to be the same for the different directions, but can be (e.g. for two or for all three). A detectable extent in the z direction is at least 0.001 mm or more such as at least 0.01 mm or more, such as at least 0.1 mm or more, such as at least 1 mm or more, and such as at least 10 mm or more.
The certain predetermined relative position 210 may be in 2D or preferably it is in 3D, i.e. the certain predetermined relative position 210 is defined according to x, y, z (or another corresponding 3D coordinate system).
In some alternative embodiments, the fiducial markers are manufactured to be on the products (e.g. one marker for one product). At some later stage, the fiducial markers may be removed from the products if such removal is required.
In the present exemplary embodiment, fiducial marker 202d differs from the other three fiducial markers 202a-202c. This difference allows e.g. an electronic imaging and analysis system that may be either separate from or integrated into the additive manufacturing apparatus, to determine for instance an orientation of the products. By recording one or more images, an analysis can reveal the position of the square marker 202d and one or more of the other markers 202a-202c. Since the absolute positions and physical dimensions of the fiducial markers are known in advance from the fiducial marker definition, the orientation, location, and physical dimensions of the products (relative to the fiducial markers) can be determined. A robotic measuring system may also perform such a determination by initially measuring and characterizing positions, shapes and/or heights of the fiducial markers to ensure that they comply with the fiducial marker definition. By subsequently making physical contact with at least a given first fiducial reference point in a first given Z-axis plane on one or more of the fiducial markers 202 and subsequently making contact with at least a given first product reference point in the first or another given Z-axis plane on one or more of the products and registering the relative distance 210 between said first fiducial marker and first product reference point, a robotic measuring system can determine the location and/or orientation and/or physical dimensions of the products. In some embodiments, two or more products manufactured during a manufacturing process each has one or more associated fiducial markers.
The above-mentioned imaging system and robotic measuring system could also, or alternatively, determine an actual size and/or shape (in each relevant dimension, e.g. 1D, 2D or as preferred in 3D) of each of one or more of the fiducial markers based on the same principles (i.e. visual and/or physical contact). The ideal size and/or shape of a given fiducial marker is known beforehand, e.g. from a product definition file and/or design.
By measuring an actual size and/or shape in one or more, preferably three, dimensions after the fiducial marker has been manufactured, it is possible to compare with the respective ideal size and/or shape and check whether a difference is within a tolerance threshold. If not, the relevant manufacturing process may be changed for manufacturing of subsequent products. E.g. a fiducial marker should be 1.1 cm×1.1 cm×2.0 cm in x, y, z but is measured to have an actual size being 1.0 cm×1.2 cm×2.0 cm signifying that the manufactured products have correspondingly inaccurate sizes. Thus the manufacturing of subsequent products should be modified (scaled)—e.g. by modifying a product definition file—by 1.1; 0.91666; 1 along the respective x, y, z directions. This would bring the fiducial markers (and more importantly the products) to have an accurate size, at least within a predetermined acceptable threshold. This may be checked and handled automatically. See also below.
In some embodiments, the imaging system and the robotic measuring system are used together. In some embodiments, one of the systems can communicate one or more measurements to the other system, and the other system be configured to operate based on the received one or more measurements.
In some embodiments, the verification of sizes and/or shapes of one or more fiducial markers along one or more dimensions is carried out or carried out again after one or more post-processing steps, e.g. cleaning, drying, post-curing, (re-)coating, etc.
In the present embodiment, each fiducial marker (or at least some of them) has an additional function. Markers 202a-202c have a stacking pin part (labelled 202a-202c in
As mentioned, measurements of the fiducial markers furthermore allow the additive manufacturing apparatus to adjust the manufacturing process in response to changes in the printed elements relative to a target or intended result. In the latter embodiment, the electronic controller is configured to receive information representing one or more determined fiducial marker lengths and/or sizes and/or shapes along one or more dimensions and/or positions, e.g. from an electronic imaging and analysis system and/or a robotic measurement system, and to adjust the manufacturing process in response.
For instance, a change in liquid temperature may cause the physical dimensions of the manufactured product to deviate from the target physical dimensions. Such a deviation may be determined by for instance optical analysis of the printed plate to determine for instance sizes along two or three dimensions of the square marker 202d. If the sizes in one or more directions deviate from the target such that the marker 202d is no longer square and/or has the ideal height, the electronic controller may cause a change in the manufacturing to compensate for the deviation. This compensation may in one embodiment be performed by effectively scaling the product definition.
If the square marker 202d has target physical dimensions of 1×1 cm, but turns out, after the above-described optical and/or mechanical analysis, to be 1×1.040 cm, the electronic controller may scale the definition in the enlarged direction. Since one of the physical dimensions is 4.0 percent too large, the electronic controller scales (or otherwise interprets) the file in such a way that the nominal or target definition results in the correct physical dimension of the manufactured product. In this example, the definition file is scaled by a factor of for instance 0.96154. When a section is printed in accordance with this factor, the additional 4.0 percent added during the printing will result in the correct physical dimension, namely 1×1 cm (0.962 times 1.040 equals 1.00048, which in the present example is considered to be compliant).
A single fiducial marker can have a shape that allows a determination of for instance position and/or orientation and/or size along one or more dimensions. This can be achieved using a fiducial marker having a rectangular cross-section with uneven side lengths, or other shape that allows a similar determination.
When the new layer 412 is formed, it is essentially glued to the floor of the vat. To form a new layer, the newly formed layer must be released from the floor, and the build platform 405 be raised some distance.
The shown additive manufacturing apparatus 400 may also manufacture one or more fiducial markers concurrently with one or more products as described elsewhere.
| Number | Date | Country | Kind |
|---|---|---|---|
| PA201570271 | May 2015 | DK | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/060224 | 5/6/2016 | WO | 00 |
