Method for controlling plurality of robotic depositors in a non-continuous deposition process

Abstract

In the context of additive manufacturing processes wherein an object is built by layered accumulations of discrete instantaneous deposits of feedstock material at specific locations according to a three-dimensional digital data model, systems and methods are taught for operating multiple independently-moving depositing devices in a shared build space to build the object. In some embodiments, depositing components perform discrete material depositing actions according to sequential lists of deposit location instructions which are dynamically sortable, enabling a control methodology to alleviate collision risks among depositing components and to improve thermal conditions of a workpiece during construction. Further embodiments provide for dynamic apportionment of discrete deposition actions among the available depositing devices for load balancing and fault tolerance.

What is claimed is: 
     
         1 . In an additive manufacturing system for constructing an object by making a series of discrete material deposits, a method comprising:
 providing at least one first robotic material-depositing subsystem comprising a first non-continuous material-depositing device attached to a first motion control system, the first subsystem acting to move the first material-depositing device to, and perform discrete deposition of material at, specific locations according to a first time-ordered list of deposit location instructions;   providing at least one second robotic material-depositing subsystem comprising a second non-continuous material-depositing device attached to a second motion control system, the second subsystem acting to move the second material-depositing device to, and perform discrete deposition of material at, specific locations according to a second time-ordered list of deposit location instructions;   detecting a potential collision between the first and second non-continuous material-depositing devices caused by simultaneous operation of the first subsystem according to the first time-ordered list and of the second subsystem according to second time-ordered list; and   altering at least one of the first and second time-ordered lists to resolve the potential collision.   
     
     
         2 . The method of  claim 1  wherein each deposit location instruction in the first and second time-ordered lists is associated with an instance of expected-time-of-occurrence data and the detecting of a potential collision comprises comparing instances of expected-time-of-occurrence data among deposit instructions in the first and second time-ordered lists. 
     
     
         3 . The method of  claim 2  wherein the altering comprises changing the value of at least one expected-time-of-occurrence data instances associated with at least one of the deposit location instructions. 
     
     
         4 . The method of  claim 1  wherein the altering comprises reordering the sequence of deposit location instructions within at least one of the first and second time-ordered lists until the potential collision is eliminated. 
     
     
         5 . The method of  claim 1  wherein the altering comprises moving at least one of the deposit location instructions from the first time-ordered list to the second time-ordered list. 
     
     
         6 . The method of  claim 4  wherein the altering further comprises moving at least one deposit location instruction from the second time-ordered list to the first time-ordered list. 
     
     
         7 . The method of  claim 1  further comprising:
 determining, as the first robotic material-depositing subsystem operates according to the first time-ordered list of deposit location instructions, a time difference between an actual time-of-occurrence for discrete deposition of material responsive to a deposit location instruction and a value of an instance of expected-time-of-occurrence data associated with the deposit location instruction; 
 detecting whether a potential collision exists when the time difference is applied to expected-time-of-occurrence data associated with subsequent deposit location instructions in the first time-ordered list; and 
 performing the altering responsive to the detecting a potential collision when the time difference is applied. 
 
     
     
         8 . The method of  claim 1  wherein at least one of the first and second material-depositing devices acts by adding heat energy to perform discrete deposition of material and wherein the method further comprises:
 obtaining a planned thermal profile for at least a portion of the object's volume; 
 producing a predictive thermal model that predicts at least one temperature within the portion caused by at least one of the first and second subsystems adding heat to specific locations of the portion as they perform discrete depositions of material within the portion; 
 comparing the predictive thermal model to the planned thermal profile to determine at least one difference value; and 
 responsive to the difference value, reducing the difference value by performing at least one of: changing timing between discrete depositions by at least one of the first subsystem and the second subsystem, reordering the programmed locations in at least one of the first time-ordered list and the second time-ordered list, moving at least one deposition location from the first time-ordered list to the second time-order list, and moving at least one deposition location from the second time-ordered list to the first time-ordered list. 
 
     
     
         9 . The method of  claim 1  wherein at least one of the first and second material-depositing devices acts by adding heat energy to perform a discrete deposition of material and wherein the method further comprises:
 providing a planned thermal profile for at least a portion of the object's volume; 
 obtaining, as the construction of the object progresses, temperature measurements within the portion caused by at least one of the first and second subsystems adding heat to specific locations of the portion as they perform discrete depositions of material within the portion; 
 comparing the temperature measurements to the planned thermal profile to determine at least one temperature difference value; and 
 responsive to the temperature difference value, reducing the temperature difference as the construction of the object proceeds by performing at least one of: changing timing between discrete depositions by at least one of the first subsystem and the second subsystem, reordering the programmed locations in at least one of the first time-ordered list and the second time-ordered list, moving at least one deposition location from the first time-ordered list to the second time-order list and moving at least one deposition location from the second time-ordered list to the first time-ordered list. 
 
     
     
         10 . The method of  claim 1  wherein at least one of the first and second material-depositing devices acts by adding heat energy to perform discrete deposition of material and wherein the method further comprises:
 obtaining a planned mechanical stress profile for at least a portion of the object's volume; 
 producing a predictive model that predicts at least one mechanical stress within the portion caused by at least one of the first and second subsystems adding heat to specific locations of the portion as they perform discrete depositions of material within the portion; 
 comparing the predictive model to the planned mechanical stress profile to determine at least one difference value; and 
 responsive to the difference value, reducing the difference value by performing at least one of: changing timing between discrete depositions by at least one of the first subsystem and the second subsystem, reordering the programmed locations in at least one of the first time-ordered list and the second time-ordered list, moving at least one deposition location from the first time-ordered list to the second time-order list, and moving at least one deposition location from the second time-ordered list to the first time-ordered list. 
 
     
     
         11 . The method of  claim 1  wherein at least one of the first and second material-depositing devices acts by adding heat energy to perform a discrete deposition of material and wherein the method further comprises:
 providing a planned mechanical stress profile for at least a portion of the object's volume; 
 obtaining, as the construction of the object progresses, mechanical stress measurements within the portion caused by at least one of the first and second subsystems adding heat to specific locations of the portion as they perform discrete depositions of material within the portion; 
 comparing the mechanical stress measurements to the planned mechanical stress profile to determine at least one difference value; and 
 responsive to the difference value, reducing the difference as the construction of the object proceeds by performing at least one of: changing timing between discrete depositions by at least one of the first subsystem and the second subsystem, reordering the programmed locations in at least one of the first time-ordered list and the second time-ordered list, moving at least one deposition location from the first time-ordered list to the second time-order list and moving at least one deposition location from the second time-ordered list to the first time-ordered list. 
 
     
     
         12 . An additive manufacturing system for forming an object by successively depositing at least one material comprising:
 a first robotic material-depositing subsystem comprising a first non-continuous material-depositing device attached to a first motion control system, the first subsystem performing a material depositing action at a specified first location by moving the first material-depositing device to the first location and depositing a mass of material at the first location, the first location being within a first area comprising a plurality of locations reachable by the first subsystem and being specified by deposit location information provided to the first subsystem;   a second robotic material-depositing subsystem comprising a second non-continuous material-depositing device attached to a second motion control system, the second subsystem performing a material depositing action at a specified second location by moving the second material-depositing device to the second location and depositing a mass of material at the second location, the second location being within a second area comprising a plurality of locations reachable by the second subsystem and being specified by deposit location information provided to the second subsystem;   a central controller, communicably coupled to the first and second subsystems, operable to maintain at least one ordered list of deposit instructions comprising deposit location information and to control the construction of the object by providing deposit location information to the first and second subsystems.   
     
     
         13 . The system of  claim 12  wherein the controller controls which subsystem is to perform a material depositing action corresponding to each of the deposit instructions. 
     
     
         14 . The system of  claim 13  wherein at least one deposit location specified by a deposit instruction is within both the first area and the second area and wherein the central controller is further operable to control whether the first subsystem or the second subsystem performs a material depositing action at the deposit location. 
     
     
         15 . The system of  claim 12  wherein each instance of communication from the central controller to a subsystem contains a proper subset of the total deposit location information contained in the ordered list of deposit instructions. 
     
     
         16 . The system of  claim 15  wherein each instance of communication from the central controller to a subsystem contains no more than one single instance of deposit location information for use by the subsystem. 
     
     
         17 . The system of  claim 12  further comprising:
 a source of time information available to the central controller; 
 wherein each deposit instruction in the ordered list is associated with a scheduled time-of-occurrence value; and 
 wherein the central controller is operable to change scheduled time-of-occurrence values. 
 
     
     
         18 . The system of  claim 17  further comprising a thermal sensor coupled to the central controller and detecting one or more thermal conditions of materials that have been deposited by the system, wherein the central controller operates to change at least one scheduled time-of-occurrence value responsive to at least one thermal condition detected by the thermal sensor. 
     
     
         19 . The system of  claim 17  wherein the first and second subsystems are positioned within the system such that, for at least one combination of a first location within the first area and a second location within the second area, moving the first subsystem in accordance with the first location while moving the second subsystem in accordance with the second location results in physical contact between one or more components of the first subsystem and one or more components of the second subsystem. 
     
     
         20 . The system of  claim 19  wherein the central controller is operable to analyze the scheduled times of occurrence values for as-yet-unexecuted deposit instructions in the at least one ordered list and to detect the presence of one or more collision instances in which moving the first subsystem in accordance with the first location and moving the second subsystem in accordance with the second location will be coincident. 
     
     
         21 . The system of  claim 20  wherein, responsive to detecting the presence of at least one collision instance, the central controller is further operable to iteratively rearrange the deposit instructions in the at least one ordered list and analyze the scheduled times of occurrence values for all as-yet-unexecuted deposit instructions until no collision instances are detected. 
     
     
         22 . The system of  claim 19  wherein the controller maintains a first subsystem-specific ordered list of deposit instructions corresponding to a sequence of deposit actions to be performed by the first subsystem and a second subsystem-specific ordered list of deposit instructions corresponding to a sequence of deposit actions to be performed by the second subsystem. 
     
     
         23 . The system of  claim 22  wherein at least one location specified by a deposit instruction in the first subsystem-specific ordered list is also within the second area and wherein the controller is further operable to move the deposit instruction from the first ordered list to the second ordered list. 
     
     
         24 . The system of  claim 22  wherein each instance of communication from the central controller to a particular subsystem contains a proper subset of the total deposit location information contained in the subsystem-specific ordered list of deposit instructions for that particular subsystem. 
     
     
         25 . The system of  claim 24  wherein each instance of communication from the central controller to the particular subsystem contains no more than one single instance of deposit location information for use by the particular subsystem. 
     
     
         26 . The system of  claim 21  wherein at least one subsystem is operable to detect failure of an attempted discrete deposit at a specific location corresponding to a first deposit instruction and to communicate a first notification of the failure to the central controller and wherein, in response to the notification, the central controller is operable to suspend communicating further deposit location information to the subsystem until receiving a second notification from the subsystem that the discrete deposit at the specific location has been successfully completed. 
     
     
         27 . The system of  claim 26  wherein the central controller is further operable to compare a time associated with the successfully completed discrete deposit to the scheduled time-of-occurrence value for the first deposit instruction and calculating an incurred delay time value resulting from the failure at the subsystem. 
     
     
         28 . The system of  claim 27  wherein the central controller is further operable to apply the incurred delay to changing the scheduled time-of-occurrence values for all as-yet-unexecuted deposit instructions in at least one ordered list. 
     
     
         29 . The system of  claim 28  wherein the central controller is further operable, upon applying the incurred delay to changing the scheduled time-of-occurrence values, to iteratively rearrange the deposit instructions in the at least one ordered list and analyze the scheduled times of occurrence values for all as-yet-unexecuted deposit instructions until no collision instances are detected. 
     
     
         30 . The system of  claim 23  further comprising:
 a thermal sensor coupled to the central controller and detecting one or more thermal conditions of materials that have been deposited by the system, wherein the central controller is further operable to, responsive to detecting at least one thermal condition, move at least one deposit instruction from the first ordered list to the second ordered list and to iteratively rearrange the deposit instructions in the at least one ordered list and analyze the scheduled times of occurrence values for all as-yet-unexecuted deposit instructions until no collision instances are detected.