Patent ID: 12257659

It should be noted that some details of the figures have been simplified and are drawn to facilitate understanding of the present teachings rather than to maintain strict structural accuracy, detail, and scale.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments (exemplary embodiments) of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the invention. The following description is, therefore, merely exemplary.

While the invention has been illustrated with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” The term “at least one of” is used to mean one or more of the listed items can be selected.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all sub-ranges subsumed therein. For example, a range of “less than 10” can include any and all sub-ranges between (and including) the minimum value of zero and the maximum value of 10, that is, any and all sub-ranges having a minimum value of equal to or greater than zero and a maximum value of equal to or less than 10, e.g., 1 to 5. In certain cases, the numerical values as stated for the parameter can take on negative values. In this case, the example value of range stated as “less than 10” can assume negative values, e.g. −1, −2, −3, −10, −20, −30, etc.

In one embodiment, depicted inFIG.1, a part is undergoing a subtractive step by machining during a hybrid additive and subtractive process. A bottom portion101of a part has been added by dispensing a sinterable metal paste, transformed into a densified bound green body by drying away volatile solvents, and manipulated into a final form by a machining process. Although a sinterable metal paste is described here, the additive step may refer to any additive step including, but not limited to, extruding, dispensing, depositing, printing, jetting, and placing. Likewise, the added materials may include, but are not limited to, metals, metal alloys, oxides, sulfides, nitrides, pnictides, polymers and various ceramics. A top portion102of the part has been added by dispensing metal paste and transformed by drying although the drying could be replaced by the transformative step appropriate to the additive step and added material including, but not limited to, removing, drying, evaporating, sublimating, curing, reacting, oxidizing, coating, baking, diffusing, implanting, freezing and polymerizing. A machining tool103is driven by a spindle through a machining tool holder104in order to manipulate by machining top portion102. The manipulation could be any manipulative step appropriate to the material, the additive step, and the transformative step including, but not limited to, milling, cutting, grinding, sanding, polishing, burnishing, etching, and ablating. In the case of dried metal paste, the top portion will tend toward being friable and the swarf, which may also be referred to as waste material, will typically be in the form of fine metal particles and small clusters of particles partially prone to becoming easily suspended in an airborne cloud near the work area and eventually settling widely and partially settling on the surfaces of bottom portion101and top portion102of the part near the area as shown by settled cluster105. Note that neither widely settled particles nor clusters of particles are desired and may be advantageously removed. In the presently described embodiment, a shroud106wraps around upper portion of tool103and lower portion of holder104on all sides except adjacent and near to top portion102of the part thereby constraining all air flow past the spindle to a small area at the bottom of the shroud. Application of a negative pressure relative vacuum at a first port107via a conduit108will create negative pressure inside the shroud106which in turn creates airflows109and110adjacent and around the part and thereby removing swarf as the swarf becomes entrained within the airflows. Thus, shroud106is used to facilitate the collection and removal of swarf generated during the manipulation process. Shroud106is sealed by motional seal111around tool holder104such that rotational motion, and optionally linear motion, of the tool holder is allowed but air flow past the seal is not allowed. Importantly the seal111should not permit the flow of swarf out of the shroud and toward other parts of the machine such as the spindle. In one embodiment both shroud106and seal111may open in roughly two pieces to allow for automatic tool changing and then be able to close again sealed. Alternatively, the spindle may rise out of the shroud, or the shroud may drop down for automatic tool changing and it will be understood by a person skilled in the art that other ways to change a tool through the shroud are included within the bounds of this disclosure. In certain embodiments, the machining tool103may be held in a holder104or a machining tool shaped to function also as a holder and fit to a tool actuator may be included.

It will be of note, as shown inFIG.1, that due to the variable nature of the part under fabrication, the gap between the shroud106and the part where flow110traverses is less than the gap between the shroud and the part where flow109traverses and this will result in lower velocity and higher volume for flow109and higher velocity but lower volume for flow110. This difference will be most accentuated near the edge of the part or overhangs112where generally about half of the opening of the roughly cylindrical shroud will not be adjacent to the part. It is therefore advantageous to properly size the circular opening of the shroud106shown inFIG.1as a diameter D in relation to the total flow via the first port107and conduit108, the size of tool103, and extension of tool103beyond the opening of the shroud given as distance E inFIG.1. The ratio of D to E, i.e. D/E, is advantageous to capturing particles when it is from about 0.025 to about 4.0 and optimal when it is from about 0.75 to about 2.0. In the case where the shroud opening varies significantly from circular in shape, advantageous and optimal ranges for D/E will differ as will be apparent to a person of sufficient skill.

In another embodiment, shroud106, tool103, seal111, and holder104form a swappable assembly with all components and dimensions chosen to optimize collection of the type, quantity, and velocity of the swarf produced by the particular tool chosen for the assembly. In this way swarf collection may be always run under optimal conditions without compromise.

In an embodiment, shown inFIG.2, shroud106is equipped with one or more ports205,206,207, and208connected to a source of pressurized air through throttling valves, two of which are shown inFIG.2(a)as201and202, or exhaust vacuum and conduit108through one or more diverters in conjunction with throttling valves201and202, two of which are shown inFIG.2(a)as203and204, and connected and controlled by a controller499. The rate of evacuation through conduit108is controlled by exhaust throttling valve211. The ports may be arranged around the periphery of the opening in the shroud106as shown inFIG.2(b)and, optionally, directed substantially at the manipulation area where, in the exhibited case of machining, the tool103is generating swarf. A camera system450connected to controller499is used to spot or detect potential buildup of swarf. Flows through ports selected for the most advantageous approach to the work area may be then adjusted or pulsed in order to free swarf from potential trouble spots which may be prone to trapping the swarf such as settled cluster105. Based on this detection of buildup of swarf by the camera, the controller may adjust flow of the pressurized air through the one or more ports. Alternatively, some of the ports may be configured via throttling valves and diverters as exhaust and some of the ports as pressured air so as to create a cross flow across the work surface and transverse of tool103which is generating swarf. In an embodiment, an actuator220is linked to and actuates motion of the shroud106and port assembly thereby changing the extension E relative to the shroud diameter D. Finally, it will be understood that a person of skill in the art will recognize that many other configurations of valves, ports, conduits, and diverters to achieve flow patterns advantageous for swarf removal are evident within the bounds of this disclosure.

FIG.3depicts a collector210. In an embodiment, collector210comprises a magnetic mass detection chamber310. Flow entrained swarf from conduit108enters magnetic mass detection chamber310wherein is positioned a magnetic collector311. Magnetic collector311comprises a single north pole or a single south pole of a magnet, both north and south poles of a single magnet, or multiple poles of a multiple pole magnetic array. The magnet or magnets may comprise permanent magnets, electromagnets, or electro-permanent magnets. Both electromagnets and electro-permanent magnets may advantageously be increased in strength, decreased in strength, set to zero strength, or reversed in polarity thereby allowing magnetic swarf to be collected, sorted, and released according to the mass, shape, and magnetism of the swarf particles and the rate of flow through the magnetic mass detection chamber310. The type of part under fabrication and the methods and rate of manipulation of the subtractive processes being employed as well as the feedstocks used during the additive steps and the processes used in the transformative step will influence the mass, shape, and magnetism of the swarf particles. Some of the swarf particles312may thus pass directly through magnetic mass detection chamber310and some of the swarf particles313will be adhered to the magnetic collector311. Magnetic collector311is coupled to scales314outside as shown, or inside, magnetic mass detection chamber310which in turn is connected to controller499via optional hub399. Advantageously for control, multiple measurements from scales314may be combined to determine the instantaneous average magnetic mass capture rate as

(Mt⁢⁢2-Mt⁢⁢1)(t⁢2-t⁢1)
where Mt1and Mt2are the masses measured at subsequent times t1and t2.

In another embodiment, collector210comprises a gravitational swarf collection chamber320. Flow entrained swarf from conduit108or from magnetic mass detection chamber310enters into swarf collection chamber320where it is diverted by a diverter321into a cyclonic pattern322around the inside walls of the dust collection chamber320and rising slowly through the middle of the chamber to exit at a port323where a vacuum is applied. The flow pattern both slows the velocity and increases the path length of the flow and thereby gives increased opportunity for the swarf particles to fall under the influence of gravity and collect and remain trapped at a bottom324of the gravitational swarf collection chamber. Scales325measure the mass, or the increase in mass, of the collected swarf324and send the results of measurements to controller499via hub399, or directly to controller499. Advantageously for control, multiple measurements from scales325are combined to determine the instantaneous average gravitational capture rate as

(Mt⁢⁢2-Mt⁢⁢1)(t⁢2-t⁢1)
where Mt1and Mt2are the masses measured at subsequent times t1and t2.

In another embodiment, collector210comprises a filtration collection chamber330. Flow entrained swarf from conduit108, from magnetic mass detection chamber310, from gravitational swarf collection chamber, or from bypass315enters into swarf filtration collection chamber330where it is collected by a fine particle filter such as one or more of the many varieties of High Efficiency Particulate Air (HEPA) filter. Scales331measure the mass, or the increase in mass, of the swarf collected in the chamber330and send the results of measurements to controller499via hub399, or directly to controller499. Advantageously for control, multiple measurements from scales325are combined to determine the instantaneous average filtration capture rate as

(Mt⁢⁢2-Mt⁢⁢1)(t⁢2-t⁢1)
where Mt1and Mt2are me masses measured at subsequent times t1and t2. Bypass315is controlled by controller499via hub399, or directly by controller499allows occasional sole use of the filtration collection chamber for when low latency or very accurate swarf generation monitoring is required. Such low latency monitoring may alternately be referred to as monitoring in real time or real time monitoring. Otherwise, collection system210would ordinarily include passage through the gravitational swarf collection chamber320.

In an embodiment, gravitational swarf collection chamber320may integrate a filter whereby, advantageously, all swarf trapped by filtration collection and by gravitational collection may be weighed on only the scales325whether or not it has yet settled on the filter or at the bottom of the chamber. It should be noted further that there is no delay in registration of the mass of newly introduced swarf once it has entered into the said combined filter and gravitational collection system chamber320since the mass of all swarf and entrained air minus air displaced by swarf will be measured on scales325.

In an embodiment shown inFIG.4, swarf evacuated through the shroud106by way of first port107and one or more air ports205,206,207, and208into conduit108is directed into detection system212which has the capability to monitor in near real time the quantity and type of swarf collected and the rate of swarf collection. Positioning detection system212within the conduit108and immediately after said ports gives the advantage of assuring that all evacuated swarf may be accounted for as it flows into detection system212.

In an embodiment of detection system212, swarf entrained in flow through conduit108enters an inductive particle detection chamber402fitted with a protected probe inductive particle sensor403such as the PMS Particulate Sensor available from Dwyer, Inc. of Michigan City, IN. The sensor operates on the principle that particles in motion near a protected probe drive minute currents, and thereby a measurable voltage, through electromagnetic induction. This induced voltage may be calibrated against other direct measurements of mass. The sensor may be pre-calibrated from the manufacturer, or it may be calibrated against mass measurements obtained via collector210, or it may be calibrated from milling a known mass of material from a sample and it will be apparent to those of sufficient skill that other methods of calibration are possible. Sensor403is controlled by, and sensor information is passed to, controller499via hub398, or directly by and to controller499. Further, since the induction sensor responds in a monotonically increasing fashion to increasing amounts of particles, it is possible to sidestep calibration and simplify the control process whereby flow rates are increased until further increases in flow rate do not result in increased particle detection.

In an embodiment of detection system212, flow entrained swarf enters optical detection system comprising optical detection chamber410fitted with windows411which allow detection light to pass through. Although detectors are positioned behind windows in the embodiment, detectors may be positioned within the walls of the chamber or inside the chamber in alternate embodiments. Light source412directs light through a said window in detection chamber410where the light may interact with swarf particles405. Some of the directed light may pass through detection chamber410not substantially diverted by interaction with swarf and exit through another window411in chamber410. As the concentration, size, shape, and composition of swarf entrained through conduit108varies, more or less light from source412will reach source light detector413having been scattered or absorbed by the swarf. Thus, light detector413provides a way to determine light attenuation caused by swarf through its connection to controller499via optional hub controller399, or directly to controller499. Some of the light from light source412that is attenuated by scattering and not absorption from swarf may be detected by backscatter detector414positioned behind a window411. Light so scattered in a substantially backwards direction is sometimes termed back scattering and light scattered but only marginally deviated is sometimes called forward scattering. Light detected by forward scattering detector415positioned behind a window411. Detectors414and415are connected to controller499via optional hub399, or directly to controller499thereby providing a measure of light scattered by swarf405entrained in flow through conduit108. Signal streams from detectors413,414, and415are combined to ascertain particle count, particle flow rate, particle size distribution, and particle composition. The optical detection system may be calibrated against mass measurements obtained via collector210, or it may be calibrated from milling a known mass of material from a sample and it will be apparent to those of sufficient skill that other methods of calibration are possible. As in the case of the protected probe inductive particle sensor403, it is possible to sidestep calibration and simplify the control process with an optical detection system whereby flow rates are increased until further increases in flow rate do not result in increased particle detection.

In an embodiment, sensors213and214are positioned within the shroud106and outside of the work area, and collect signals A and B, respectively, to controller499. Sensors213and214may be a protected probe inductive particle sensor such as403; optical detection systems described in a previous embodiment; or other sensors that measure a particle concentration. Flows are increased so as to increase the swarf collection power and thereby amount of swarf collected. Signals A and B may be considered singly, jointly, or the ratio

AB
as a super signal. As swarf collected reaches near the point of all swarf generated, signals A,

AB,
and B will increase, increase, and decrease, respectively, until a point of saturation where further increases of collection power, e.g. flows, does not produce further increase, increase, and decrease in signals A,

AB,
and B, respectively, after which flows can be set for a duration, or collection rates may be dithered to determine rate of change of said signals to flow, or by several other methods of setting and control that will be apparent to a person of sufficient skill in the relevant arts.

Control and calibration of the said one or more throttling valves201,202, and others, diverters203and204and others, and exhaust throttling valve211may be by digital software computer algorithm which resides and executes on controller499, said controller comprising a computer system. Alternatively, a digital software algorithm may reside and execute on a remote computer system that is part of a network which the controller499is in communication with, and may be directed by, said remote computer system. The controller may automatically adjust the throttling valves according to the build program running under computer numerical control on controller499. In an embodiment, flow through air ports operating in the vicinity of large or small gaps between the shroud opening and the part may be adjusted up or down by adjusting throttling valves201,202, and others, diverters203and204, and others, and the exhaust throttling valve211be adjusted up or down according to a model of expected and needed airflows required to optimize swarf removal and collection into the shroud.

An embodiment comprises a control scheme as depicted inFIG.5as follows; Once machine instructions are ready for a manipulation step in the hybrid process, acquisition of monitoring data is begun including flow rates, capture rates, particle detections, camera images, and part mass loss. Then a swarf generation model of the part being built encompassing the additive steps e.g. dispensing, the transformative steps e.g. drying, and the manipulation steps e.g. machining, is used to calculate a set of expected swarf generation rates. The swarf generation model may encompass both calculated and measured quantities or masses of material added e.g. by dispensing, transformed e.g. by drying away solvents, and manipulated e.g. by machining. Calculation may be by a variety of methods such as calculating the added volume or mass of a layer or some portion of a part, the change of mass expected during the transformation e.g. the amount of solvent to be removed from the added volume, and the mass of transformed material to be removed during manipulation to achieve the final form of said part or portion of part. Measurement may be by a variety of methods such as measuring, for example, the mass of material dispensed during addition, measuring, for example, the amount of solvent removed during transformation, and measuring, for example, the mass of material removed during fabrication of the said part or portion of part. For purposes of measuring the mass of material gained during addition, lost or gained during transformation, and lost or gained during manipulation, part101under fabrication resides on scales230which is connected to controller499as depicted inFIG.2. A set of required flow rates are calculated from said swarf generation model and a model of the performance of the particular mechanical arrangement of the shroud106, ports205,206,207,208, and others, the collector210and the exhaust system comprising107,108, and exhaust throttling valve211, throttling valves201,202, and other, and diverters203,204, and others. An operating margin is determined within which required air flow rates are deemed suitable for operating with process parameter adjustment. The manipulative step, e.g. machining process, is started and the monitoring data is compared to the expected swarf generation plus design bias. If less swarf is detected than expected, or if the camera spots accumulation of swarf on the part, the process flows need to be increased and the model appropriately adjusted. Camera system450spotted swarf may indicate interrupting the normal part processing for removal if possible and deemed necessary. If more swarf is detected than expected but within the operating margin then processing continues without adjustment to the process flows or model, and if swarf is detected in excess of the expected amount plus the operating margin, flows may be too high and need to be decreased and the model appropriately adjusted. Additionally, very excessive swarf flows may indicate a significant and unexpected process excursion and an alarm may be raised or the process can be halted otherwise the process proceeds until the manipulation, e.g. machining, step instructions are completed. In several embodiments, the adjustment of flows and model may happen continuously, quasi-continuously, intermittently, at predetermined times e.g. every few seconds, at predetermined points e.g. between layers or cycles of addition, transformation and manipulation, part to part such as during multiple piece part fabrication, or any combination comprising the aforementioned ways.

In an embodiment, depicted inFIG.6(a), tool103is milling into a recessed feature600such as a blind trench or hole in order to finish a rough edge601in top portion102of a part undergoing hybrid additive and subtractive fabrication. This action may create a swarf cluster602to settle against a previously finished surface603and become trapped due to the lack of air circulation in the recessed feature600. In the embodiment, tool103is advantageously equipped with internal air conduits604and605which are fed with pressurized air through a rotational feedthrough a seal606in holder104. As the tool mills, pressurized air flows out of the tool within the recessed feature thereby creating turbulent air currents which lift swarf from the recessed feature and force the swarf toward the opening of shroud106. Negative pressure inside said shroud caused by a negative relative pressure applied through port107through conduit108creates a collecting action. The air flows within the recess combined with said collecting action advantageously remove and prevent the formation of swarf clusters602.

In another embodiment, shown inFIG.6(b), a nozzle610positioned within shroud106is supplied with pressurized air through throttling a valve611and directed substantially at the work area represented by surface601undergoing milling by tool103. In a similar way to a previous embodiment shown inFIG.6(a), air flows within the recess feature600combined with the collecting action of shroud106prevents the formation of swarf cluster602against finished surface603. It will be apparent to a person of sufficient skill in the subject matter that there are many other possible configurations of this embodiment. For example, in certain embodiments, residue removal may be completed after one or more machining steps. Additionally, alternate embodiments may include nozzles in any combination of configurations described in previous embodiments herein. One or more cameras may detect whether all residue has been removed and thus determine whether the residue removal may continue or be stopped.

In a related embodiment, any residual swarf clusters602trapped in recessed feature600is removed by pressurized air fed through ports205/206/207/208, conduits604/605or nozzle610after the milling step and before dispensing the next layer of sinterable paste. This swarf removal step may be performed in addition to the swarf removal during the milling step. The swarf removal step may be performed by rastering shroud106across the entire surface of the part or just in areas of the part where swarf clusters602are expected to form based on the swarf generation model. The swarf removal step may be performed in response to swarf clusters602spotted by the camera system450connected to the controller499.

In an embodiment shown inFIG.7, part102resting on a build plate701is undergoing the manipulative step in a hybrid additive and subtractive manufacturing process. Tool103is creating swarf, which for various particular geometries of part and tool may result in accumulated clusters of swarf105and jet of ejected swarf706. A port705is positioned so the jet706flows substantially into port705and port705opens to a duct703which would lead onto conduit108ofFIG.2comprised with collector210and detection system212ofFIG.3andFIG.4respectively, for purposes of swarf collection, detection, and abatement. Air is supplied from port704via duct702oriented opposite port705and duct703with tool103and part102positioned substantially on a line between ports704and705such that airflow sweeps over part102where tool103generates and ejects swarf. In an embodiment, ports704and705may be oriented and rotated about axis707of tool103, which advantageously allows interception of jet706independent of part102geometry or tool103orientation relative to the part102and also allows airflows to be optimized in places where swarf cluster105may accumulate. In addition to orientation about tool axis707, ports704and705may translate “up” or “down” in the direction of tool axis707. Alternatively, ports704and705may be stationary and build plate701may rotate and translate in a plane perpendicular to tool axis707and translate in the direction of tool axis707. In a further alternative embodiment, both the ports704and705and the build plate701may allow some or any of the above described types of motion so as to further allow flexibility and optimize airflow across part102to facilitate removal of swarf.

In an embodiment depicted inFIG.8, a fabrication chamber800houses a fabrication system801comprising exhaust conduit108and tool103which is generating swarf during the manipulation step of hybrid additive and subtractive manufacturing. As air and swarf are evacuated via conduit108, a negative pressure or relative vacuum is established within fabrication chamber800. Chamber800is substantially sealed so that negative pressure prevents swarf from escaping, however make up air may be drawn in through an inlet baffle802which has a series of orifices within the chamber such that a laminar flows803is established along the inner walls of chamber800. In this way, swarf is advantageously prevented from escaping into the environment and all swarf may be detected, measured, collected and abated via detection systems212and collection system210.

It will be clear to a practitioner with ordinary skill in the art that many other extensions and configurations in addition to the preferred embodiments are possible and exemplification of these preferred embodiments herein does not preclude these other embodiments for the purposes of this disclosure.