WO2021173146A1

WO2021173146A1 - System and method for support structure parameter and type selection in an additive manufacturing process

Info

Publication number: WO2021173146A1
Application number: PCT/US2020/020303
Authority: WO
Inventors: Gaurav AMETA; Omkar Murlidhar GHALSASI; Suraj Ravi MUSUVATHY; Wentao Fu; Christoph SAMMLER; Frederic VILLENEUVE; Livio Dalloro
Original assignee: Siemens Energy, Inc.
Priority date: 2020-02-28
Filing date: 2020-02-28
Publication date: 2021-09-02

Abstract

A method of forming a component using an additive manufacturing process includes providing a geometrical design of the component, discretizing the geometrical design into a plurality of geometric bodies, and matching each geometric body with an object from a feature database, each object including an object build setup configuration and an object support structure specification. The method further includes applying the object build setup configuration and the object support structure specification for each object to its corresponding geometric body to define a component build setup configuration and a component support structure specification, outputting the geometrical design, the component build setup configuration, and the component support structure specification to an additive manufacturing system, and forming the component including the component support structure specification using the additive manufacturing system.

Description

SYSTEM AND METHOD FOR SUPPORT STRUCTURE PARAMETER AND TYPE SELECTION IN AN ADDITIVE MANUFACTURING PROCESS

BACKGROUND

[0001] Additive manufacturing techniques have greatly enhanced the ability to manufacture parts and components that were difficult, if not impossible to manufacture using conventional manufacturing techniques. During many of the manufacturing processes, the component is built-up layer by layer. During this process, all or some of the component must be properly supported.

[0002] Laser Powder Bed Fusion (L-PBF) is one of many types of additive manufacturing (AM) processes that are now widely used to create cost effective and functionally superior metallic parts in aerospace, automotive, and other industries.

BRIEF SUMMARY

[0003] In one construction, a method of forming a component using an additive manufacturing process includes providing a geometrical design of the component, discretizing the geometrical design into a plurality of geometric bodies, and matching each geometric body with an object from a feature database, each object including an object build setup configuration and an object support structure specification. The method further includes applying the object build setup configuration and the object support structure specification for each object to its corresponding geometric body to define a component build setup configuration and a component support structure specification, outputting the geometrical design, the component build setup configuration, and the component support structure specification to an additive manufacturing system, and forming the component including the component support structure specification using the additive manufacturing system.

[0004] In another construction, a method of forming a component using an additive manufacturing process includes populating a feature database with a plurality of objects, each object including an object build setup configuration and an object support structure specification, providing a geometrical design of the component, discretizing the geometrical design into a plurality of geometric bodies, and matching each geometric body with an object from a feature database. The method also includes applying the object build setup configuration and the object support structure specification for each object to its corresponding geometric body to define a component build setup configuration and a component support structure specification, outputting the geometrical design, the component build setup configuration, and the component support structure specification to an additive manufacturing system, and forming the component including the component support structure specification using the additive manufacturing system.

[0005] In yet another construction, a computing apparatus includes a processor and a memory storing instructions that, when executed by the processor, configure the apparatus to discretize a geometrical design into a plurality of geometric bodies, match each geometric body with an object from a feature database, each object including an object build setup configuration and an object support structure specification, apply the object build setup configuration and the object support structure specification for each object to its corresponding geometric body to define a component build setup configuration and a component support structure specification, and output the geometrical design, the component build setup configuration, and the component support structure specification to an additive manufacturing system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0007] FIG. 1 illustrates an additive manufacturing system.

[0008] FIG. 2 illustrates a component and support structure arrangement produced by the additive manufacturing system of FIG. 1.

[0009] FIG. 3 illustrates a support structure design system suitable for use with the additive manufacturing system of FIG. 1. [0010] FIG. 4 illustrates an object and support structure arrangement for use with the support structure design system of FIG. 3.

[0011] FIG. 5 illustrates a routine including the support structure design system of FIG. 3.

[0012] FIG. 6 illustrates another routine including the support structure design system of FIG. 3.

[0013] FIG. 7 illustrates a block support 700 in accordance with one embodiment.

[0014] FIG. 8 illustrates a tree support 800 in accordance with one embodiment.

[0015] FIG. 9 illustrates a volume support 900 in accordance with one embodiment.

[0016] FIG. 10 illustrates a line support 1000 in accordance with one embodiment.

DETAILED DESCRIPTION

[0017] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in this description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0018] Various technologies that pertain to systems and methods will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged apparatus.

[0019] It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments.

[0020] Also, it should be understood that the words or phrases used herein should be construed broadly, unless expressly limited in some examples. For example, the terms “including,” “having,” and “comprising,” as well as derivatives thereof, mean inclusion without limitation. The singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. The term “or” is inclusive, meaning and/or, unless the context clearly indicates otherwise. The phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. Furthermore, while multiple embodiments or constructions may be described herein, any features, methods, steps, components, etc. described with regard to one embodiment are equally applicable to other embodiments absent a specific statement to the contrary.

[0021] Also, although the terms "first", "second", "third" and so forth may be used herein to refer to various elements, information, functions, or acts, these elements, information, functions, or acts should not be limited by these terms. Rather these numeral adjectives are used to distinguish different elements, information, functions or acts from each other. For example, a first element, information, function, or act could be termed a second element, information, function, or act, and, similarly, a second element, information, function, or act could be termed a first element, information, function, or act, without departing from the scope of the present disclosure.

[0022] In addition, the term "adjacent to" may mean: that an element is relatively near to but not in contact with a further element; or that the element is in contact with the further portion, unless the context clearly indicates otherwise. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Terms “about” or “substantially” or like terms are intended to cover variations in a value that are within normal industry manufacturing tolerances for that dimension. If no industry standard as available a variation of 20 percent would fall within the meaning of these terms unless otherwise stated.

[0023] FIG. 1 illustrates an additive manufacturing system 100 that includes an energy source 102, an enclosure 106, and a computing apparatus 120 that operates to control the additive manufacturing system 100. The enclosure 106 includes a structure sized and arranged to support a component 110 as it is manufactured as well as a supply of powdered material 108 and a powdered material supply 112. In the illustrated construction, the powdered material 108 and the powdered material supply 112 include a powdered metal. However, other materials may be utilized in the illustrated additive manufacturing system 100.

[0024] The enclosure includes a lowering mechanism 116 arranged to lower a platform 122 that supports the powdered material 108 and the component 110 during the manufacturing process. At the completion of the formation of a given layer, the lowering mechanism 116 lowers the component 110 to allow for the formation of the next layer.

[0025] A raising mechanism 118 is positioned to raise a powdered material supply 112 and a delivery system 114 in the form of a roller is arranged to direct a portion of the powdered material supply 112 toward the component 110 to provide the needed material for the next layer.

[0026] The energy source 102 operates to produce a beam of energy 104 that is sufficiently powerful to melt the necessary portion of the powdered material 108 to form a layer on the component 110. In the illustrated construction, the energy source 102 is a laser and the beam of energy 104 is a laser beam. Of course, other sources of energy such as electron beam generators and the like could be employed as desired.

[0027] The computing apparatus 120 controls the operation of the energy source 102, the lowering mechanism 116, the raising mechanism 118, and the delivery system 114 to assure continued and proper operation of the additive manufacturing system 100. In many constructions, the geometrical design of the component 110 is delivered to the computing apparatus 120 in a suitable format such as a 3-D computer model or other computer code. The computing apparatus 120 translates this program into the necessary movements of the aforementioned components including the pattern traced by the beam of energy 104 to manufacture the component 110. [0028] The computing apparatus 120 includes a processor, a memory storage device, as well as active memory that are used in conjunction to process the computer code as required by the particular additive manufacturing system 100 being operated. The computing apparatus 120 also includes a communication system that may facilitate wireless or wired communication between another computer system as well as between the computing apparatus 120 and the additive manufacturing system 100.

[0029] FIG. 1 illustrates the additive manufacturing system 100 in the form of a laser powder bed fusion arrangement. However, as one of ordinary skill will appreciate, the system described below is equally applicable to other types of additive manufacturing systems and can be utilized with other materials in place of powdered metals.

[0030] FIG. 2 illustrates a component and support structure specification 200 in which the component 110 is supported by a component support structure specification 202 that may include one or more support members in the form of block supports 204, line supports 206, tree supports, and volume supports 208 among others used in additive manufacturing applications.

[0031] As illustrated in FIG. 2, the block supports 204 are thin-walled supports arranged in a grid while having contact to the component 110 at a small area. The block supports 204 connect two points, one on the component 110 or at the base of another support member, and the other one either somewhere else on the same or a different component 110 or on a support member or platform 122. In general, block supports 204 may be created as volume-less (minimum thickness determined by the additive manufacturing process) single-path entities or solid voluminous ones. In addition, block supports 204 may be connected in a fashion that does not form a grid. These are then called line supports.

[0032] Also illustrated in FIG. 2 are line supports 206 (sometimes referred to as polyline supports, bouquet supports, tree supports, and the like) that branch out to support a line, an edge, or an elongated or enlarged area (when compared to the support provided by block supports 204). The illustrated line supports 206 support the component 110 along a line.

[0033] FIG. 2 also illustrates support members in the form of volume supports 208. In general, volume supports 208 are hollow, regular structures similar to walls or solid regions. [0034] In general, all support members can be categorized as one of block supports 204, line supports 206, and volume supports 208 with other shapes, arrangements, or names being possible.

[0035] FIG. 2 illustrates the component and support structure specification 200 determined by a support structure design system 300. The component and support structure specification 200 illustrated in FIG. 2 includes the component 110 supported by the component support structure specification 202 The component support structure specification 202 includes a number of support members that extend from the platform 122 to the component 110 to support each component 110.

[0036] The support structure design system 300 operates to select the component and support structure specification 200 to assure a probability of failure that is lower than the predetermined limit or goal, but balances this with the amount of material required for the component and support structure specification 200 as well as the speed with which the component 110 can be manufactured.

[0037] The arrangement, shape, size, and placement of the component and support structure specification 200 can greatly affect the quality of the finished product as well as the efficiency (i.e., quantity of material used) and the speed with which the component 110 is manufactured.

In many cases, trial and error experiments and the experience of a manufacturing engineer is required to properly design the component support structure specification 202.

[0038] FIG. 3 illustrates a support structure design system 300 that includes an offline portion 302 and an online portion 304 that are run or operated by a computer, such as the computing apparatus 120 or other data processing device. The offline portion 302 includes a feature database 306 that includes a number of objects in the form of simple geometric objects. The feature database 306 is filled prior to use of the support structure design system 300 and may include simple objects such as cubes, spheres, arches, and the like with an example illustrated in FIG. 4.

[0039] FIG. 4, illustrates an example of an object and support structure specification 400 which includes an object 402 arranged in a build setup configuration and supported by an object support structure specification 404. The object support structure specification 404 includes a plurality of support elements 406 that extend from the platform 122 to the object 402 to support the object 402 in the desired build setup configuration. While the object 402 and the object support structure specification 404 are used throughout the following description, it should be understood that many different objects and support structures are possible.

[0040] Returning to FIG. 3, for each object in the feature database 306, a build setup configuration 308 is generated, with the build setup configuration 308 including the position and orientation of the object. An object support structure specification 404 is selected for the object 402 positioned in the build setup configuration 308 using conventional techniques or other techniques. Once an object support structure specification 404 is selected, a simulation plan 310 including a design of experiments plan can be formulated to test the feasibility of the build setup configuration 308 and the object support structure specification 404. The simulation plan 310 can include finite element analysis and Latin hypercube sampling (LHS). With the simulation plan 310 completed, the user can conduct the simulation 312. The results of the simulation 312 can include the deformations and locations of that deformation of the individual support elements 406 within the object support structure specification 404 and their failure criteria. The failure criteria could account for factors such as material selection, desired manufacturing process, and other criteria for different applications. The data generated in the simulation 312 is used to build a surrogate model for the object 402 using the build setup configuration 308 and the object support structure specification 404. The data also includes a probability of failure during the manufacture of the object 402 using the build setup configuration 308 and the object support structure specification 404.

[0041] The just-described process is repeated for each object using one or more of a different build setup configuration 308 and/or a different object support structure specification 404. For example, for any given build setup configuration 308, support elements 406 of varying types and varying ranges of parameters (e.g., length, width, cross-section, etc.) could be employed with varying levels of success, efficiency, and speed of manufacture. This allows for the construction of a collection of surrogate models for each object using the different build setup configurations and/or the different object support structure arrangements. With sufficiently large databases, machine learning methods may also be used to create additional surrogate models.

[0042] It should also be noted that the just-described process could be applied for different additive manufacturing processes. For example, the statistical database 314 could be constructed and filled with data for various objects from the feature database 306 based on using a laser powder bed fusion process. The same objects could then be used to construct another database, or add to the existing statistical database 314, surrogate models based on another different additive manufacturing process.

[0043] The illustrated object and support structure specification 400 would constitute one entry in the statistical database 314. It is possible that the same object 402 would be included in the statistical database 314 with a different build setup configuration and/or a different object support structure specification 404.

[0044] The offline portion 302 is generally prepared prior to use with an actual component 110. The statistical database 314 is generally completed or at least partially completed and is populated with data for a plurality of geometric bodies or objects.

[0045] With continued reference to FIG. 3, the online portion 304 includes a discretizing step 318, an applying inverse surrogate models step 320, and an output step 322. In order to initiate the online portion 304 of the support structure design system 300, a user first provides an input design 316. The input design 316 may include a 3-D computer model or other geometrical design that can be used by the computer operating the support structure design system 300.

First, the discretizing step 318 breaks the 3-D computer model into smaller simpler discrete geometric features or geometric bodies that, in general each match the geometry of one of the objects in the feature database 306.

[0046] With the 3-D computer model now discretized, the data from the statistical database 314, including the failure likelihoods, the selected build setup configuration 308, and the selected object support structure specification 404, is applied to the discretized components in the applying inverse surrogate models step 320. Thus, the output of the applying inverse surrogate models step 320 is a discretized geometry of the component 110 including a component support structure specification 202 and a build setup configuration for the additive manufacture of the component 110. The applying inverse surrogate models step 320 also calculates a statistical probability or probability range of failure of the component support structure specification 202 or the component 110 during the manufacturing process.

[0047] As discussed, in the offline portion 302, various build setup configurations 308 and support structure arrangements 202 are analyzed to calculate a likelihood of failure. In the applying inverse surrogate models step 320 several of these objects are combined to arrive at a desired build setup configuration 308 and component support structure specification 202, however there is no actual analysis. Rather, the known likelihoods of failure (known probability of failure) for the various objects that make up the discretized geometry are used to calculate the probability of failure for the selected build setup configuration 308 and component support structure specification 202 for the component 110. Only when this probability meets a predetermined standard (e.g., greater than ninety percent likelihood of success) is the output step 322 performed.

[0048] In the output step 322, the selected build setup configuration 308, component support structure specification 202, and component 110 design are outputted, in a desired format to the additive manufacturing system 100 or the computing apparatus 120 for the additive manufacturing system 100.

[0049] In block 502, the method of forming a component 500 receives a geometrical design or input design 316 of the component 110. In block 504, the method of forming a component 500 discretizes the input design 316 into a plurality of geometric bodies. In block 506, the method of forming a component 500 matches each geometric body with an object from a feature database 306, each object including a build setup configuration 308 and an object support structure specification 404. In block 508, the method of forming a component 500 applies the build setup configuration 308 and the object support structure specification 404 for each object to its corresponding geometric body to define a component build setup configuration and a component support structure specification 202. In block 510, the method of forming a component 500 outputs the geometrical design, the component build setup configuration, and the component support structure specification 202 to an additive manufacturing system 100. In block 512, the method of forming a component 500 forms the component 110 including the component support structure specification 202 using the additive manufacturing system 100.

[0050] In block 602, the method of forming a component 600 populates a feature database 306 with a plurality of objects, each object 402 including an object build setup configuration and an object support structure specification 404. In block 604, the method of forming a component 600 provides a geometrical design of the component 110. In block 606, the method of forming a component 600 discretizes the geometrical design into a plurality of geometric bodies. In block 608, the method of forming a component 600 matches each geometric body with an object from the feature database 306. In block 610, the method of forming a component 600 applies the object build setup configuration and the object support structure specification 404 for each object 402 to its corresponding geometric body to define a component build setup configuration 308 and a component support structure specification 202. In block 612, the method of forming a component 600 outputs the geometrical design, the component build setup configuration 308, and component support structure specification 202 to an additive manufacturing system 100. In block 614, the method of forming a component 600 forms the component 110 including the component support structure specification 202 using the additive manufacturing system 100.

[0051] Figs. 7-10 illustrate various examples of shapes and types of supports that can be selected by the support structure design system 300 to support a component 110. FIG. 7 illustrates a block support 700 that would be selected to support a large area. The block support 700 includes a plurality of support points 702 that each engage the component 110 to support it as desired.

[0052] FIG. 8 illustrates a tree support 800 that can be selected by the support structure design system 300 to support an area that may not be suited to support by a block support 700. Each tree support 800 includes a plurality of branches 802 that extend from trunks 804. The larger trunks 804 provide strength and stiffness for the total load being carried while the individual branches 802 provide support for smaller areas. Each branch 802 includes a support point 702 at its end.

[0053] FIG. 9 illustrates a volume support 900 that can be selected by the support structure design system 300 to support a narrow area. The volume support 900 includes a top surface that acts as the support point 702 for the volume support 900 and engages the component 110 being supported.

[0054] FIG. 10 illustrates a line support 1000 that can be selected by the support structure design system 300 to support a very narrow area or an edge. The line support 1000 includes a plurality of support points 702 that can be sized and spaced as desired to provide the necessary support for the component 110. In addition, stiffeners 1002 can be added to the line support 1000 to stiffen the line support 1000 and assure it provides the desired support. [0055] As one of ordinary skill in the art will understand, these examples of supports are but a few of the possible choices. These supports can be mixed or have features combined to define different types of supports. In addition, similar supports may have different names in the industry. As such, the supports provided herein should be considered as mere examples of the possible supports and the invention should not be limited in any way to these supports or their description.

[0056] It should be noted that the foregoing description describes a known probability of failure with regard to the objects, and a likelihood or probability of failure with regard to the component. The known probability of failure is calculated through analysis for each object and is therefore considered “known”. In contrast, the component support structure specification 202 is not analyzed such that only a probability of failure can be determined.

[0057] It should also be clear that the probability of failure should be low and that the probability of success is the inverse of the probability of failure. It is preferred that any design have a probability of failure of under ten percent with more preferred designs having a probability of failure of under five percent, and most preferred designs having a probability of failure of under two percent.

[0058] In use, a user first populates the statistical database 314 by building and analyzing simple geometric features or objects. In some constructions, a database including some of these features may be publicly available or provided to the user. However, the user could augment the statistical database 314 with more specific or detailed objects that might be more common or suited to that user's particular needs.

[0059] With the input design 316 populated, the user can provide a 3-D computer model of any desired component 110 to the online portion 304 at the discretizing step 318. The support structure design system 300 then performs the online portion 304 to arrive at a solution that includes the build setup configuration and the component support structure specification for the particular component being designed. The output step 322 then outputs these results, including the probability of failure, the selected component build setup configuration, and the selected component support structure specification. The output data can be directed to a specific user or could be output directly to an additive manufacturing system 100 or the computing apparatus 120 of the additive manufacturing system 100 if desired. [0060] Although an exemplary embodiment of the present disclosure has been described in detail, those skilled in the art will understand that various changes, substitutions, variations, and improvements disclosed herein may be made without departing from the spirit and scope of the disclosure in its broadest form.

[0061] None of the description in the present application should be read as implying that any particular element, step, act, or function is an essential element, which must be included in the claim scope: the scope of patented subject matter is defined only by the allowed claims. Moreover, none of these claims are intended to invoke a means plus function claim construction unless the exact words "means for" are followed by a participle.

Claims

CLAIMS What is claimed is:

1. A method of forming a component using an additive manufacturing process, the method comprising: providing a geometrical design of the component; discretizing the geometrical design into a plurality of geometric bodies; matching each geometric body with an object from a feature database, each object including an object build setup configuration and an object support structure specification; applying the object build setup configuration and the object support structure specification for each object to its corresponding geometric body to define a component build setup configuration and a component support structure specification; outputting the geometrical design, the component build setup configuration, and the component support structure specification to an additive manufacturing system; and forming the component including the component support structure specification using the additive manufacturing system.

2. The method of claim 1, wherein the additive manufacturing process comprises a laser powder bed fusion process.

3. The method of claim 1, wherein the geometrical design comprises a 3-D computer model of the component.

4. The method of claim 1, wherein the object support structure specification for the object from the feature database has a known probability of failure.

5. The method of claim 4, further comprising determining a likelihood of failure for the component support structure specification based on the known probability of failure for each of the object support structure specifications of the objects used in matching the geometric body.

6. The method of claim 5, further comprising repeating the matching step, the applying step, and the determining step in response to the determined likelihood of failure being below a predetermined value.

7. The method of claim 6, wherein the predetermined value is greater than 90 percent.

8. A method of forming a component using an additive manufacturing process, the method comprising: populating a feature database with a plurality of objects, each object including an object build setup configuration and an object support structure specification; providing a geometrical design of the component; discretizing the geometrical design into a plurality of geometric bodies; matching each geometric body with an object from the feature database; applying the object build setup configuration and the object support structure specification for each object to its corresponding geometric body to define a component build setup configuration and a component support structure specification; outputting the geometrical design, the component build setup configuration, and the component support structure specification to an additive manufacturing system; and forming the component including the component support structure specification using the additive manufacturing system.

9. The method of claim 8, wherein the additive manufacturing process comprises a laser powder bed fusion process.

10. The method of claim 8, wherein the geometrical design comprises a 3-D computer model of the component.

11. The method of claim 8, further comprising determining a known probability of failure for each object support structure specification.

12. The method of claim 11, further comprising determining a likelihood of failure for the component support structure specification based on the known probability of failure for each of the object support structure specifications of the objects used in matching the geometric body.

13. The method of claim 12, further comprising repeating the matching step, the applying step, and the predicting step in response to the predicted likelihood of failure being below a predetermined value.

14. The method of claim 13, wherein the predetermined value is greater than 90 percent.

15. A computing apparatus, the computing apparatus comprising: a processor; and a memory storing instructions that, when executed by the processor, configure the apparatus to: discretize a geometrical design into a plurality of geometric bodies; match each geometric body with an object from a feature database, each object including an object build setup configuration and an object support structure specification; apply the object build setup configuration and the object support structure specification for each object to its corresponding geometric body to define a component build setup configuration and a component support structure specification; and output the geometrical design, the component build setup configuration, and the component support structure specification to an additive manufacturing system.

16. The computing apparatus of claim 15, wherein the additive manufacturing system comprises a laser powder bed fusion process.

17. The computing apparatus of claim 15, wherein the object support structure specification for the object from the feature database has a known probability of failure.

18. The computing apparatus of claim 17, wherein the instructions further configure the apparatus to determine a likelihood of failure for the component support structure specification based on the known probability of failure for each of the object support structure specifications of the objects used in matching the geometric body.

19. The computing apparatus of claim 18, wherein the instructions further configure the apparatus to repeat the matching step, the applying step, and the predicting step in response to the determined likelihood of failure being above a predetermined value.

20. The computing apparatus of claim 19, wherein the predetermined value is ten percent.