Patent Description:
Additive manufacturing systems are used to print or otherwise build 3D parts from digital representations of the 3D parts (e.g., AMF and STL format files) using one or more additive manufacturing techniques. Examples of commercially available additive manufacturing techniques include extrusion-based techniques such as fused deposition modeling (FDM), electro-photography (EP), jetting, selective laser sintering (SLS), high speed sintering (HSS), powder/binder jetting, electron-beam melting, and stereolithographic processes. For each of these techniques, the digital representation of the 3D part is initially sliced into multiple horizontal layers. For each sliced layer, a tool path is then generated, which provides instructions for the particular additive manufacturing system to print the given layer.

For example, in an extrusion-based additive manufacturing system, a 3D part may be printed from a digital representation of the 3D part in a layer-by-layer manner by extruding a flowable part material. The part material is extruded through an extrusion tip carried by a print head of the system, and is deposited as a sequence of roads on a substrate in an x-y plane. The extruded part material fuses to previously deposited part material, and solidifies upon a drop in temperature. The position of the print head relative to the substrate is then incremented along a z-axis (perpendicular to the x-y plane), and the process is then repeated to form a 3D part resembling the digital representation.

In fabricating 3D parts by depositing layers of a part material, supporting layers or structures are typically built underneath overhanging portions or in cavities of 3D parts under construction, which are not supported by the part material itself. A support structure may be built utilizing the same deposition techniques by which the part material is deposited. The host computer generates additional geometry acting as a support structure for the overhanging or free-space segments of the 3D part being formed. Support material is then deposited from a second nozzle pursuant to the generated geometry during the printing process. The support material adheres to the part material during fabrication, and is removable from the completed 3D part when the printing process is complete. <CIT> is related to a consumable material for use in an additive manufacturing system, the consumable material comprising a polyamide blend of at least one semi- crystalline polyamide, and at least one amorphous polyamide that is substantially miscible with the at least one semi-crystalline polyamide, and a physical geometry configured to be received by the additive manufacturing system for printing a three-dimensional part from the consumable material in a layer-by-layer manner using an additive manufacturing technique. <CIT> is related to blends of at least two separately made crystalline polyarylether resins formed into an intimate moldable mixture, each resin having, prior to being formed into said mixture (i) a different crystalline melting temperature and a different glass transition temperature, of (ii) a different molecular arrangement of unit components each resin comprising <NUM>,<NUM> phenylene units separated by ether oxygen and at least one of said resins containing <NUM>,<NUM>-phenylene unit separated by a divalent carbonyl radical.

The invention is defined in the accompanying claims.

Unless otherwise specified, the following terms as used herein have the meanings provided below:.

The term "polymer" refers to a polymeric material having one or more monomer species, including homopolymers, copolymers, terpolymers, and the like.

The term "semi-crystalline polymer" refers to a polymer having an enthalpy of fusion of greater than <NUM> J/g, when measured from above the melting temperature to below the hot crystallization temperature. The term "amorphous polymer" refers to a polymer that is not a semi-crystalline polymer.

Reference to "a" chemical compound refers one or more molecules of the chemical compound, rather than being limited to a single molecule of the chemical compound. Furthermore, the one or more molecules may or may not be identical, so long as they fall under the category of the chemical compound. Thus, for example, "a" polyamide is interpreted to include one or more polymer molecules of the polyamide, where the polymer molecules may or may not be identical (e.g., different molecular weights and/or isomers).

The terms "at least one" and "one or more of" an element are used interchangeably, and have the same meaning that includes a single element and a plurality of the elements, and may also be represented by the suffix "(s)" at the end of the element. For example, "at least one polyamide", "one or more polyamides", and "polyamide(s)" may be used interchangeably and have the same meaning.

Directional orientations such as "above", "below", "top", "bottom", and the like are made with reference to a layer-printing direction of a 3D part. In the embodiments shown below, the layer-printing direction is the upward direction along the vertical z-axis. In these embodiments, the terms "above", "below", "top", "bottom", and the like are based on the vertical z-axis. However, in embodiments in which the layers of 3D parts are printed along a different axis, such as along a horizontal x-axis or y-axis, the terms "above", "below", "top", "bottom", and the like are relative to the given axis.

Unless otherwise specified, characteristics of a material or a 3D item printed from the material refer to the characteristics as measured parallel to the orientation of the 3D item layers and perpendicular to the layer-printing direction, and is referred to as an "xy-direction". Correspondingly, the term "z-direction", with reference to characteristics of a material or a 3D item printed from the material refer to the characteristics as measured perpendicular to the orientation of the 3D item layers and parallel to the layer-printing direction. Unless the measurement direction is specified as "in the z-direction", a measurement referred to herein is taken in the xy-direction. For example, a tensile strength of a 3D item of <NUM>,<NUM> psi refers to a tensile strength measured parallel to the layers of the 3D item. Alternatively, a tensile strength of a 3D item in the z-direction of <NUM>,<NUM> psi refers to a tensile strength measured perpendicular to the layers of the 3D item.

Unless otherwise specified, temperatures referred to herein are based on atmospheric pressure (i.e. one atmosphere).

The term "additive manufacturing system" refers to a system that prints, builds, or otherwise produces 3D items and/or support structures at least in part using an additive manufacturing technique. The additive manufacturing system may be a stand-alone unit, a subunit of a larger system or production line, and/or may include other non-additive manufacturing features, such as subtractive-manufacturing features, pick-and-place features, two-dimensional printing features, and the like.

The term "providing", such as for "providing a consumable material", when recited in the claims, is not intended to require any particular delivery or receipt of the provided item. Rather, the term "providing" is merely used to recite items that will be referred to in subsequent elements of the claim(s), for purposes of clarity and ease of readability.

The terms "preferred" and "preferably" refer to embodiments of the invention that may afford certain benefits, under certain circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the present disclosure.

The terms "about" and "substantially" are used herein with respect to measurable values and ranges due to expected variations known to those skilled in the art (e.g., limitations and variabilities in measurements).

The present disclosure is directed to an additive manufacturing method for printing 3D items in a layer-by-layer manner from a build material that compositionally includes a blend of one or more semi-crystalline polymers and one or more secondary materials. The combination of the semi-crystalline polymer(s) and the secondary material(s) interact to control the rate or kinetics at which crystallization occurs. The controlled crystallization kinetics results in diminished forces and stresses relative to uncontrolled crystallization, such that layers containing semi-crystalline polymer(s) can be used to build an item through additive manufacturing in a layer by layer manner that previously could not be accomplished. Additionally, the controlled rate or kinetics at which crystallization occurs generates sufficient heat of fusion or enthalpy to induce molecular reptation at the extrudate-item interface to bond the extruded layer to the item such that the layers have a sufficient bond to prevent delamination.

The disclosed method can be utilized to print an item with a number of commercially available semi-crystalline polymer(s) and/or co-polymer(s), including polyetherketoneketone (PEKK).

In some instances, depending upon the material desired to print the item, the method involves controlling the crystallization kinetics of the semi-crystalline polymer(s) upon cooling from a melted state to minimize or otherwise reduce the percent crystallinity of the printed item, while also generating sufficient crystallization-exothermic energy to induce molecular reptation at the extrudate-item interface. The rate of crystallinity can be reduced by providing a build material that compositionally includes one or more semi-crystalline polymers and one or more secondary materials that are configured to retard crystallization of the one or more semi-crystalline polymers, where the one or more secondary materials are substantially miscible with the one or more semi-crystalline polymers. Additionally, direct polymerization or selection of specially polymerized polymers, which are synthesized with disrupted structural regularity can be utilized that where the molecular structure limits and moderates their crystallization kinetics and mechanics.

In other instances, depending upon the material desired to print the item, the method involves controlling the crystallization kinetics of the semi-crystalline polymer(s) to increase the kinetics or rate at which the crystals are formed upon cooling from a melted state, such that the item has a selected crystallinity while also generating sufficient heat of fusion or enthropy to induce molecular reptation at the extrudate-item interface. Typically, acceleration of the crystallization kinetics is required when the semi-crystalline polymer in pure form exhibits less than <NUM> J/g enthalpy when cooled at <NUM>/min cooling as measured by differential scanning calorimetry (DSC) when cooling from the melting temperature to the hot crystalline temperature at a rate of <NUM>/min. The acceleration of the crystallization kinetics increases the enthalpy to at least <NUM> J/g when cooled at <NUM>/min cooling as measured by differential scanning calorimetry (DSC) when cooling from the melting temperature to the hot crystalline temperature at a rate of <NUM>/min.

For instance, in FDM and EP additive manufacturing systems, acceleration of the crystallization kinetics allows the copolymer to be held within a range of the glass transition temperature and a cold crystallization temperature due to the development of small, but significant modulus and crystallinity. Techniques for accelerating the kinetics of certain polymers, such as certain polyketone and polyester copolymers include the addition of micron-scale additives, such as synthetic fibers, minerals (natural or synthetic). The addition of one or more immiscible secondary polymers, which are finely dispersed as a discrete phase through compounding techniques common in polymer processing can also be utilized to increase the crystallization kinetics.

In order to effectively induce molecular reptation at the extrudate-item and sufficiently diminish the forces and stresses caused by volumetric shrinkage associated with typical crystallization of the semi-crystalline polymer in a layer as it is cooled, a process window is created by slowing the crystallization kinetics such that where the polymer(s) generate between about <NUM> J/g heat of fusion and about <NUM>% of the heat of fusion of a build material that is compositionally about <NUM>% of the semi-crystalline build material, as measured by differential scanning calorimetry (DSC) when cooling from the melting temperature to the hot crystalline temperature at a rate of <NUM>/min. When accelerating the crystallization kinetics a minimum enthropy of about <NUM> J/g is desired. The disclosed ranges represents a continuum of the percentage of crystallinity in the build material where at the lower end of the range, the build material has properties more closely related to crystalline materials and at the upper end of the range, the build material has properties more closely related to amorphous materials. The disclosed ranges also describe the range of useful entropy for unfilled materials at the low enthalpy and heavily filled materials, at the high enthalpy end of the range.

The manner in which the crystallization kinetics of the item material are controlled can vary depending on the additive manufacturing technique used, such as an extrusion-based additive manufacturing technique including fused deposition modeling (FDM) and out of oven FDM (OOO), big area additive manufacturing (BAAM) and electrophotography-based additive manufacturing technique (EP), which is typically between the glass transition temperature and a cold crystallization temperature or a solidification temperature and the cold crystallization temperature. A selective laser sintering technique (SLS) or a high speed sintering technique (HSS) use a different process window in relative to extrusion-based additive manufacturing technique that is typically slightly above a hot crystallization temperature and slightly below a melt temperature. However, for HHS devices a process window between the glass transition temperature and the cold crystallization temperature could be used for some materials. These distinctions are primarily due to the different thermal states in which the printed layers are typically held for the given additive manufacturing techniques.

With respect to SLS and HSS additive manufacturing systems, the secondary material or materials is utilized to retard or slow the availability of the formation of crystallites. The retarding or slowing of the availability of the formation of crystallites can be caused by adding an amorphous polymer that is miscible with the semi-crystalline material and forms an amorphous alloy which lowers the hot crystallization temperature. Alternatively, a monomer can be added as the secondary material or materials to form a copolymer that breaks the long range order of the polymer and hinders the availability of the formation of crystallites and therefore depresses the hot crystallization temperature. The crystallites will maintain their respective energies required to break intermolecular bonds and hence the melting temperature of the alloy or copolymer will not change significantly.

However, the addition of the amorphous, miscible polymer or the irregularmonomer with the semi-crystalline material will decrease the hot crystallization temperature and the rate at which the crystallites form. While the amount of the secondary material will depend upon the polymer class, the combination of the secondary material, whether an amorphous miscible polymer or an irregular monomer, will cause a depression in the hot crystallization temperature. However, the depression or reduction of the hot cyrstallization temperature will allow the use of semi-crystalline materials in HSS and SLS additive manufacturing devices that typically could not be utilized.

The secondary material represses the hot crystallization temperature at least about <NUM>. The secondary material represses the hot crystallization temperature at least about <NUM> and more typically at least about <NUM>. The larger the repression of the hot crystallization temperature, the larger the processing window and the lower operating temperature can be, which can be advantageous especially when operating an SLS or HSS device.

With respect to OOO devices, semi-crystalline materials similar to that used in extrusion techniques are utilized. However a sufficient amount of plasticizer is added to reduce the glass transition temperature to between a range of <NUM> and about <NUM> such that the environment of does not require heating. By reducing the glass transition temperature, lower residual stress are retained in the item manufactured by OOO devices.

Fillers and reinforcing agents can be added to the polymer matrix to increase the heat deflection temperature. For instance, after annealing the item containing carbon fiber, significant increases in the heat deflection temperature can be realized.

By way of example, extrusion-based additive manufacturing systems typically print or otherwise build 3D items from amorphous polymeric materials, such as acrylonitrile-butadiene-styrene (ABS) resins and polycarbonate resins. During a printing operation, the amorphous polymeric material is melted and extruded as a series of roads, which cool down to form layers of a 3D item. Due to the layer-by-layer nature of the printing, the cooling of each successive layer generates residual stresses in the 3D item, which are a function of the coefficient of thermal expansion, percent shrinkage, and tensile modulus of the material. If not relieved, the residual stresses may physically distort the 3D item, such as by causing the edges and corners of the 3D item to curl up, referred to as "curl" or "curling".

Amorphous polymeric materials have little or no ordered arrangements of their polymer chains in their solid states. As such, these materials exhibit glass transition effects that can be controlled to partially relieve residual stresses. For example, as disclosed in Batchelder, <CIT>, an amorphous polymeric material may be deposited into a heated chamber (or at least a locally-heat deposition region) maintained at a temperature that is between a solidification temperature and a glass transition temperature of the material. This anneals the successively-printed printed layers, allowing them to cool down and solidify slowly, which can partially relieve the residual stresses.

Semi-crystalline polymeric materials, however, have different mechanical and thermal characteristics from amorphous polymeric materials. For example, due to their achievable crystallinity, 3D items printed with semi-crystalline polymeric materials may exhibit superior mechanical properties compared to 3D items printed with amorphous polymeric materials. However, due to their higher levels of achievable crystallinity, semi-crystalline polymeric materials can exhibit discontinuous changes in volume upon solidification. Therefore, layers of a semi-crystalline polymeric material may contract and shrink when deposited, thereby accumulating inacceptable residual stresses.

In comparison to amorphous polymeric materials, which can have relatively broad annealing windows, it has been conventionally difficult to maintain a temperature window that is suitable for annealing semi-crystalline polymers, particularly with extrusion-based additive manufacturing systems. For instance, curl will result if the polymer is held at a temperature above or below the process window. Any variations outside of this small temperature window will result in solidification with discontinuous changes in volume, such as curl, if above or below the temperature window. The discontinuous changes in volume can be particularly troublesome for extrusion-based additive manufacturing systems where the printed 3D items or support structures are coupled to underlying and non-shrinkable build sheets. Furthermore, sagging may occur if there is not enough crystallinity generated during the cooling process. Each of these conditions may result in distortions of the printed 3D item. As such, it has been difficult to print dimensionally stable 3D items from semi-crystalline polymers using extrusion-based additive manufacturing systems, where the amount of crystallinity formed during the cooling process is sufficient such that the 3D items do not sag, yet also do not induce curl forces that will curl the 3D item.

It is important that the crystallization kinetics are accurate and correct for the semi-crystalline material with the secondary material, otherwise a process window cannot be determined. In FDM manufacturing systems, the whole item is built with partial crystallinity and the support materials are removed. After the support materials are removed, the item is annealed at a selected temperature for a selected amount of time to congruently crystallize the part and prevent warping.

In SLS additive manufacturing, the item is built with build material in an amorphous state between hot crystallization temperature and below the melt temperature. The entire part is then cooled and crystallized in a single step.

However, as discussed below, the crystallization kinetics of particular build materials can be controlled in an extrusion-based additive manufacturing system to print 3D items having mechanical properties (e.g., strengths and ductilities) similar to those of semi-crystalline polymeric materials, while also being annealable in a heated chamber of an additive manufacturing system (or at least a locally-heated deposition region) to partially relieve residual stresses.

<FIG> illustrate system <NUM>, which is an extrusion-based additive manufacturing system for printing or otherwise building 3D items, from the build material blends discussed herein, in a manner that controls the crystallization kinetics, as discussed below. Suitable extrusion-based additive manufacturing systems for system <NUM> include fused deposition modeling systems developed by Stratasys, Inc. , Eden Prairie, MN under the trademark "FDM".

As shown in <FIG>, system <NUM> may include chamber <NUM>, platen <NUM>, platen gantry <NUM>, print head <NUM>, head gantry <NUM>, and consumable assemblies <NUM> and <NUM>. Chamber <NUM> is an example enclosed build environment that contains platen <NUM> for printing 3D items and support structures, where chamber <NUM> may be may be optionally omitted and/or replaced with different types of build environments. For example, a 3D item and support structure may be built in a build environment that is open to ambient conditions or may be enclosed with alternative structures (e.g., flexible curtains).

In the shown example, the interior volume of chamber <NUM> may be heated with heater <NUM> to reduce the rate at which the build and support materials solidify after being extruded and deposited (e.g., to reduce distortions and curling). Heater <NUM> may be any suitable device or assembly for heating the interior volume of chamber <NUM>, such as by radiant heating and/or by circulating heated air or other gas (e.g., inert gases). In alternative embodiments, heater <NUM> may be replaced with other conditioning devices, such as a cooling unit to generate and circulate cooling air or other gas. The particular thermal conditions for the build environment may vary depending on the particular consumable materials used.

In further embodiments, the heating may be localized rather than in an entire chamber <NUM>. For example, the deposition region may be heated in a localized manner. Example techniques for locally-heating a deposition region include heating platen <NUM> and/or with directing heat air jets towards platen <NUM> and/or the 3D items/support structures being printed). As discussed above, the heating in chamber <NUM> and/or the localized deposition region anneals the printed layers of the 3D items (and support structures) to partially relieve the residual stresses, thereby reducing curling of the 3D items.

Platen <NUM> is a platform on which 3D items and support structures are printed in a layer-by-layer manner. In some embodiments, platen <NUM> may also include a flexible polymeric film or liner on which the 3D items and support structures are printed. In the shown example, print head <NUM> is a dual-tip extrusion head configured to receive consumable filaments from consumable assemblies <NUM> and <NUM> (e.g., via guide tubes <NUM> and <NUM>) for printing 3D item <NUM> and support structure <NUM> on platen <NUM>. Consumable assembly <NUM> may contain a supply of the build material for printing 3D item <NUM> from the build material. Consumable assembly <NUM> may contain a supply of a support material for printing support structure <NUM> from the given support material.

Platen <NUM> is supported by platen gantry <NUM>, which is a gantry assembly configured to move platen <NUM> along (or substantially along) a vertical z-axis. Correspondingly, print head <NUM> is supported by head gantry <NUM>, which is a gantry assembly configured to move print head <NUM> in (or substantially in) a horizontal x-y plane above chamber <NUM>.

In an alternative embodiment, platen <NUM> may be configured to move in the horizontal x-y plane within chamber <NUM>, and print head <NUM> may be configured to move along the z-axis. Other similar arrangements may also be used such that one or both of platen <NUM> and print head <NUM> are moveable relative to each other. Platen <NUM> and print head <NUM> may also be oriented along different axes. For example, platen <NUM> may be oriented vertically and print head <NUM> may print 3D item <NUM> and support structure <NUM> along the x-axis or the y-axis.

System <NUM> also includes controller <NUM>, which is one or more control circuits configured to monitor and operate the components of system <NUM>. For example, one or more of the control functions performed by controller <NUM> can be implemented in hardware, software, firmware, and the like, or a combination thereof. Controller <NUM> may communicate over communication line <NUM> with chamber <NUM> (e.g., with a heating unit for chamber <NUM>), print head <NUM>, and various sensors, calibration devices, display devices, and/or user input devices.

In some embodiments, controller <NUM> may also communicate with one or more of platen <NUM>, platen gantry <NUM>, head gantry <NUM>, and any other suitable component of system <NUM>. While illustrated as a single signal line, communication line <NUM> may include one or more electrical, optical, and/or wireless signal lines, allowing controller <NUM> to communicate with various components of system <NUM>. Furthermore, while illustrated outside of system <NUM>, controller <NUM> and communication line <NUM> may be internal components to system <NUM>.

System <NUM> and/or controller <NUM> may also communicate with computer <NUM>, which is one or more computer-based systems that communicates with system <NUM> and/or controller <NUM>, and may be separate from system <NUM>, or alternatively may be an internal component of system <NUM>. Computer <NUM> includes computer-based hardware, such as data storage devices, processors, memory modules and the like for generating and storing tool path and related printing instructions. Computer <NUM> may transmit these instructions to system <NUM> (e.g., to controller <NUM>) to perform printing operations. Controller <NUM> and computer <NUM> may collectively be referred to as a controller assembly for system <NUM>.

<FIG> illustrates a suitable device for print head <NUM>, as described in Leavitt, <CIT>. Additional examples of suitable devices for print head <NUM>, and the connections between print head <NUM> and head gantry <NUM> include those disclosed in Crump et al. , <CIT>; Swanson et al. , <CIT>; LaBossiere, et al. , <CIT> and <CIT>; Batchelder et al. , <CIT>; and<CIT>. In additional embodiments, in which print head <NUM> is an interchangeable, single-nozzle print head, examples of suitable devices for each print head <NUM>, and the connections between print head <NUM> and head gantry <NUM> include those disclosed in <CIT>.

In the shown dual-tip embodiment, print head <NUM> includes two drive mechanism <NUM> and <NUM>, two liquefier assemblies <NUM> and <NUM>, and two nozzles <NUM> and <NUM>. In this embodiment the build material and the support material each preferably have a filament geometry for use with print head <NUM>. For example, as best shown in <FIG>, the build material may be provided as filament <NUM>. In alternative embodiments, the build material of the present disclosure may be provided in powder or pellet form for use in an auger-pump print head, such as disclosed in <CIT>.

During operation, controller <NUM> may direct wheels <NUM> of drive mechanism <NUM> to selectively draw successive segments filament <NUM> from consumable assembly <NUM> (via guide tube <NUM>), and feed filament <NUM> to liquefier assembly <NUM>. Liquefier assembly <NUM> may include liquefier tube <NUM>, thermal block <NUM>, heat shield <NUM>, and tip shield <NUM>, where liquefier tube <NUM> includes inlet end <NUM> for receiving the fed filament <NUM>. Nozzle <NUM> and tip shield <NUM> are accordingly secured to outlet end <NUM> of liquefier tube <NUM>, and liquefier tube <NUM> extends through thermal block <NUM> and heat shield <NUM>.

While liquefier assembly <NUM> is in its active state, thermal block <NUM> heats liquefier tube <NUM> to define heating zone <NUM>. The heating of liquefier tube <NUM> at heating zone <NUM> melts the build material of filament <NUM> in liquefier tube <NUM> to form melt <NUM>. The upper region of liquefier tube <NUM> above heating zone <NUM>, referred to as transition zone <NUM>, is not directly heated by thermal block <NUM>. This generates a thermal gradient or profile along the longitudinal length of liquefier tube <NUM>.

The molten portion of the build material (i.e., melt <NUM>) forms meniscus <NUM> around the unmelted portion of filament <NUM>. During an extrusion of melt <NUM> through nozzle <NUM>, the downward movement of filament <NUM> functions as a viscosity pump to extrude the build material of melt <NUM> out of nozzle <NUM> as extruded roads to print 3D item <NUM> in a layer-by-layer manner. While thermal block <NUM> heats liquefier tube <NUM> at heating zone <NUM>, cooling air may also be blown through a manifold <NUM> toward inlet end <NUM> of liquefier tube <NUM>, as depicted by arrows <NUM>. Heat shield <NUM> assists in directing the air flow toward inlet end <NUM>. The cooling air reduces the temperature of liquefier tube <NUM> at inlet end <NUM>, which prevents filament <NUM> from softening or melting at transition zone <NUM>.

In some embodiments, controller <NUM> may servo or swap liquefier assemblies <NUM> and <NUM> between opposing active and stand-by states. For example, while liquefier assembly <NUM> is servoed to its active state for extruding the support material to print a layer of support structure <NUM>, liquefier assembly <NUM> is switched to a stand-by state to prevent the build material from being extruded while liquefier assembly <NUM> is being used. After a given layer of the support material is completed, controller <NUM> then servoes liquefier assembly <NUM> to its stand-by state, and switches liquefier assembly <NUM> to its active state for extruding the build material to print a layer of 3D item <NUM>. This servo process may be repeated for each printed layer until 3D item <NUM> and support structure <NUM> are completed.

While liquefier assembly <NUM> is in its active state for printing support structure <NUM> from a support material filament, drive mechanism <NUM>, liquefier assembly <NUM>, and nozzle <NUM> (each shown in <FIG>) may operate in the same manner as drive mechanism <NUM>, liquefier assembly <NUM>, and nozzle <NUM> for extruding the support material. In particular, drive mechanism <NUM> may draw successive segments of the support material filament from consumable assembly <NUM> (via guide tube <NUM>), and feed the support material filament to liquefier assembly <NUM>. Liquefier assembly <NUM> thermally melts the successive segments of the received support material filament such that it becomes a molten support material. The molten support material may then be extruded and deposited from nozzle <NUM> as a series of roads onto platen <NUM> for printing support structure <NUM> in a layer-by-layer manner in coordination with the printing of 3D item <NUM>.

As mentioned above, the build material compositionally includes a blend of one or more semi-crystalline polymers and one or more secondary materials that may either retard crystallization of the semi-crystalline polymer(s) or accelerate the formation of crystals within the build material. When retarding crystallization, the secondary material(s) include one or more amorphous polymers that are at least partially miscible, and typically completely miscible, with the semi-crystalline polymer(s). Also, the use of polymers with disrupted structural regularity (or steric hindrance) that limits and moderates the crystallization mechanics to retard crystallization. When accelerating crystallization, secondary materials are added that cause the formation of crystals including but not limited to, the addition of micro-scale additive such as synthetic fibers, natural or synthetic minerals, the addition of immiscible secondary polymers that are dispersed as a discrete phase through known compounding techniques. Again, whether the crystallization kinetics are to be retarded or accelerated depends upon the physical properties of the selected semi-crystalline build material(s).

<FIG> illustrates a DSC plot for an exemplary build material. The build material is nylon <NUM> under the trade designation Grivory® L16 manufactured by EMS-Grivory business unit of EMS-Chemie AG, located at Domat/Ems, Switzerland. The DSC pot in <FIG> shows the various thermal transitions that the next build material may exhibit. For example, during an initial heating phase, such as when the build material is melted in liquefier assembly <NUM>, the build material may produce a heating profile <NUM> with a glass transition temperature (Tg), a cold crystallization temperature (Tc,cold), and a melting temperature (Tm). The glass transition temperature (Tg) refers to the point along curve <NUM> where the build material undergoes a second-order transition to achieve an increase in its heat capacity.

The cold crystallization temperature Tc,cold typically occurs due to the increased mobility of the polymer molecules after exceeding the glass transition temperature Tg, which allows a portion of the semi-crystalline polymer(s) to form crystalline regions. Because the crystallization is an exothermic process, it releases thermal energy based on a first-order transition, as illustrated by the inverted peak in heating profile <NUM>.

The melting temperature Tm is the temperature at which the build material fully liquefies, also based on a first-order transition. Typically, the build material is quickly heated past its melting temperature Tm in liquefier assembly <NUM> for extrusion. As such, during this point in the process, the glass transition temperature Tg and the cold crystallization temperature Tc,cold are not overly relevant to the crystallization state of the extrudate, other than for potential melt flow and temperature control aspects in liquefier assembly <NUM>.

The DSC plot in <FIG> also includes a cooling profile <NUM>, which illustrates hot crystallization temperature Tc,hot, and describes the crystallization kinetics of the build material as it cools down from its melting temperature Tm. For example, after being extruded from nozzle <NUM>, the extruded build material may deposit as roads onto the previously-formed layer of 3D item <NUM>, and begin cooling down. In other words, the build material begins to follow cooling profile <NUM> at a cooling rate that depends on the environment temperature that 3D item <NUM> is printed in (e.g. in chamber <NUM>), as well as the particular composition of the build material and the size of 3D item <NUM>.

Preferably, the layers of 3D item <NUM> are printed in chamber <NUM> (or at least in a locally-heated deposition region) that is maintained at a temperature between a solidification temperature and the cold crystallization temperature Tc,cold of the build material. This can anneal the successively-printed printed layers, allowing them to cool down and solidify slowly, which can partially relieve the residual stresses.

Referring to <FIG>, the crystallization kinetics of the same semi-crystalline material in <FIG>, that includes a miscible amorphous polymer which in this instance is Grilamid® TR <NUM> manufactured by EMS. TR <NUM> is a polyamide based on aliphatic and cycloaliphatic blocks and therefore is amorphous and completely miscible in the base material. While the range <NUM> between glass transition temperature (Tg) and the cold crystallization temperature (Tc,cold), are slightly changed, the temperature range <NUM> between the melting temperature Tm and the hot crystallization temperature Tc,hot, is increased, either by increasing the melting temperature Tm or reducing the hot crystallization temperature Tc,hot. The increase in the temperature range between the melting temperature Tm or reducing the hot crystallization temperature Tc,hot increases the operating window for additive manufacturing techniques such as SLS and HSS.

Particularly beneficial results include the suppression or reduction of the hot crystallization temperature Tc,hot, when using manufacturing techniques such as SLS and HSS. The suppression or reduction of the hot crystallization temperature Tc,hot, allows the built item to be annealed at lower temperatures relative to those of semi-crystalline materials that have not had the crystallization kinetics modified. The suppression of the hot crystallization temperature Tc,hot, allows the annealing process to be performed at temperatures that are lower than previously obtainable. As the removal of heat from the item being built is a limiting factor in the size of the item being built through either the SLS or HSS technique, the present disclosure provides the capability of increasing the size of the item being built with the SLS or HHS technique, up to the doubling of the size of the item being built relative to currently used processes and materials.

When using extrusion-based additive techniques such as FDM, BAAM, and EP, chamber <NUM> or the locally-heated deposition region is maintained at a temperature between a solidification temperature and the glass transition temperature Tg of the build material. These embodiments are suitable for build materials having low levels of crystalline regions, where the crystalline regions are not capable of supporting the printed layers at higher temperatures without slumping.

Alternatively, in other embodiments, chamber <NUM> or the locally-heated deposition region is maintained at a temperature within an annealing window <NUM> having a lower limit at about the glass transition temperature Tg of the build material and an upper limit that is less than the cold crystallization temperature Tc,cold of the build material. In particular, annealing window <NUM> preferably encompasses the plateau region <NUM> of DSC heating curve <NUM>, which is above the increased slope for the glass transition temperature Tg and below the decreased slope for the cold crystallization temperature Tc,cold. These embodiments are suitable for build materials having enough crystalline regions to support the printed layers without slumping, despite being held above the glass transition temperature Tg of the build material.

In further techniques, such as OOO, where low-temperature materials are used (e.g., those with glass transition temperatures near ambient temperatures), chamber <NUM> may be omitted, and the build material may be printed at room temperature (e.g., <NUM>). Regardless of the annealing temperature, it has been found that the substantially-miscible blends for the build material modify the glass transition temperature Tg of the build material from that of the amorphous polymer(s), typically flowing the Flory-Fox Equation. The substantially-miscible blends may also decrease the hot crystallization temperature Tc,hot of the build material from that of the pure semi-crystalline polymer(s). This provides a unique advantage in that the cumulative amount of crystallization for the build material upon cooling can be reduced, which accordingly allows the printed layers of the build material to have low levels of crystallinity.

In particular, upon being extruded and deposited from nozzle <NUM>, the build material preferably is quickly cooled down past its hot crystallization temperature Tc,hot to its annealing temperature below the cold crystallization temperature Tc,cold of the build material (e.g., within annealing window <NUM>). This effectively supercools the build material down below its cold crystallization temperature Tc,cold. It should also be noted that when sufficient amounts of filler such as, but not limited to glass and carbon fiber, items can be printed in the cold crystallization temperature Tc,cold region, because the filler effectively retards the volumetric change during crystallization.

It has been found that the level of crystallinity can be controlled based on the particular annealing temperature used. For instance, if more amorphous properties are desired, the annealing temperature may be set to be set within about <NUM> of the glass transition temperature Tg of the build material. Alternatively, if more crystalline properties are desired, the annealing temperature may be set to be set within <NUM> of the cold crystallization temperature Tc,cold of the build material. Furthermore, any intermediate amorphous-crystalline variation may be achieved by maintaining the annealing temperature at a selected temperature within annealing window <NUM>.

The incorporation of the amorphous polymer(s) also assists in physically impeding the semi-crystalline polymer(s) from grouping together in ordered arrangements to form crystalline regions. As such, as the build material quickly cools down from its melting temperature Tm, the short residence time in the region between its hot crystallization temperature Tc,hot and its cold crystallization temperature Tc,cold, combined with the crystallization impedance, preferably minimizes or otherwise reduces the formation of crystalline regions in the build material.

For instance, if a given pure semi-crystalline polymer (i.e., non-blend) is capable of crystallizing to its fullest extent in about <NUM> seconds in the region between its hot crystallization temperature Tc,hot and its cold crystallization temperature Tc,cold, and if it quickly cools down such that it resides in this region for about one second, it may form about one-third of is achievable of crystalline regions. In comparison, the crystallization impedance of the build material blend may require more than a <NUM> to <NUM>-fold increase in the time required to fully crystallize. As such, when the build material resides in this region between its hot crystallization temperature Tc,hot and its cold crystallization temperature Tc,cold for about one second, it may only form about <NUM>-<NUM>% of its fully-achievable crystallinity, for example. In fact, it has been observed that the supercooled build material exhibits a translucent, substantially non-opaque appearance. This is an indication that crystallinity has been significantly retarded since crystalline regions typically modify the indices of refraction of the extruded layers to render them opaque.

The minimized or reduced crystallization correspondingly reduces the discontinuous changes in volume of the semi-crystalline polymer(s), thereby reducing the residual stresses on the printed layers. Furthermore, holding the printed layers at the annealing temperature (e.g., within annealing window <NUM>) also anneals the successively-printed printed layers, allowing them to cool down and solidify slowly, which can relieve the residual stresses typically associated with amorphous materials.

In other words, the build material is preferably supercooled quickly from its extrusion temperatures down to an annealing temperature in annealing window <NUM>, and then held within annealing window <NUM> for a suitable duration to relieve the residual stresses. After that, the printed layers of the build material may be cooled down further (e.g., below its glass transition temperature Tg and/or its solidification temperature).

Another interesting property of the build materials of the present disclosure is that, despite the minimized or reduced crystallinity, the crystallization that does occur during the supercooling generates a sufficient amount of heat to induce extra or increased molecular reptation at the extrudate-item interface. In other words, the heat produced during the limited crystallization-exothermic reaction allows the polymer molecules at the extrudate-item interface to move and become highly entangled. It has been observed that, due to the heat of fusion of the extruded roads, the rate of temperature decay of the extruded build material can change, and cool down at a slower rate. For example, in an interior raster pattern, this can result in an interfacial temperature boost, causing better reptation in the X-Y build plane, as long as the rastered roads contact each other before the extruded build material cools down to the annealing temperature in chamber <NUM>. This accordingly increases the strength of the printed 3D item <NUM> in both the intra-layer x-y directions, and also in the interlayer z-direction. As a result, 3D item <NUM> may have mechanical properties (e.g., strengths and ductilities) similar to those of semi-crystalline polymer(s). Also, if the material is maintained at a temperature above the glass transition temperature, the transition is not necessary to be overcome to impart mobility at the item-extrudate interface.

In extrusion based printing techniques other than OOO, and with HSS once the printing operation is completed, 3D item <NUM> may then be cooled down to room temperature and optionally undergo one or more post-printing processes. Alternatively, 3D item <NUM> may be reheated in a post-printing crystallization step. In this step, 3D item <NUM> may be heated up to about its cold crystallization temperature Tc,cold for a sufficient duration to induce further crystallization of the semi-crystalline polymer(s). Examples of suitable annealing durations in the post-printing crystallization step range from about <NUM> minutes to <NUM> hours, and may vary depending on the dimensions of each 3D item <NUM> and the build material compositions. Correspondingly, examples of suitable annealing temperatures in the post-printing crystallization step range from about the cold crystallization temperature Tc,cold of the build material to within about <NUM> above its cold crystallization temperature Tc,cold, and more preferably to within about <NUM> above its cold crystallization temperature Tc,cold.

The post-printing crystallization step can further increase the mechanical, thermal, and chemical resistance properties of 3D item <NUM> due to the increased formation of the crystalline regions. Additionally, this post-printing crystallization step is performed on 3D item <NUM> as a whole (i.e., congruent crystallization), rather than as the layers are individually printed. As such, any potential shrinkage on 3D item <NUM> from the formation of the crystalline regions occurs in a uniform manner similar to the effects in an injection molding process, rather than in a layer-by-layer manner that can otherwise result in curling effects. Another important feature with the post-printing crystallization step is that 3D part <NUM> is preferably de-coupled from platen <NUM> (e.g., from a build sheet of platen <NUM>), allowing 3D part <NUM> to be further crystallized without being restricted by any non-shrinkable build sheet or rigid support material. However, a supporting sand or powder may be acceptable.

As mentioned above, a 3D part <NUM> having a translucent, substantially non-opaque appearance is an indication that crystallinity has been retarded during the printing operation. Similarly, the transformation from the translucent, substantially non-opaque appearance to an opaque appearance is an indication that the build material of 3D item <NUM> has undergone significant crystallization in the post-printing crystallization step. After the post-printing crystallization step is completed, the resulting 3D item <NUM> may then be cooled down to room temperature and optionally undergo one or more post-printing processes.

The post-printing crystallization step may be performed in chamber <NUM> of system <NUM>, or alternatively in a separate annealing oven. A separate annealing oven may be preferred in many situations, such as when support structure <NUM> needs to be removed prior to the post-printing annealing step and/or when system <NUM> needs to be used for subsequent printing operations. For example, a printing farm of multiple systems <NUM> may operate in coordination with one or more separate annealing ovens to maximize the duty cycles of the systems <NUM>.

The above-discussed control of the crystallization kinetics of the build material requires the build material to have a blend of one or more semi-crystalline polymers and one or more secondary materials, preferably amorphous polymer(s), that retard crystallization of the semi-crystalline polymer(s) and that are at least partially miscible (or more preferably, substantially miscible) with the semi-crystalline polymer(s).

Preferably the semi-crystalline polymer(s) and the secondary material(s) in the blend are separate compounds (e.g., separate polymers) that are homogenously blended. However, in alternative (or additional) embodiments, build material may include one or more copolymers having chain segments corresponding to the semi-crystalline polymer(s) and the secondary material(s), where the chain segments of the secondary material(s) retard the crystallization of the chain segments of the semi-crystalline polymeric material(s).

The build material includes a substantially miscible blend of one or more amorphous polyetherketoneketones (PEKK) and one or more semi-crystalline polyetherketoneketones (PEKK). Concentrations of the amorphous polyaryletherketones(s) in this blend range from about <NUM>% by weight to about <NUM>% by weight, and more typically from about <NUM>% by weight to about <NUM>% by weight, where the semi-crystalline polyaryletherketones(s) constitute the remainder of the blend.

In some build material compositions, the build material may also include additional additives, such as colorants, fillers, plasticizers, impact modifiers, and combinations thereof. In embodiments that include colorants, preferred concentrations of the colorants in the build material range from about <NUM>% to about <NUM>% by weight. Suitable colorants include titanium dioxide, barium sulfate, carbon black, and iron oxide, and may also include organic dyes and pigments.

In build material compositions that include fillers, concentrations of the fillers in the build material range from about <NUM>% to about <NUM>% by weight for some fillers (e.g., glass and carbon fillers), and up to about <NUM>% by weight for other fillers, such as metallic and ceramic fillers. Suitable fillers include calcium carbonate, magnesium carbonate, glass spheres, graphite, carbon black, carbon fiber, glass fiber, talc, wollastonite, mica, alumina, silica, kaolin, silicon carbide, zirconium tungstate, soluble salts, metals, ceramics, and combinations thereof.

In the build material compositions including the above-discussed additional additives, the polymer blend preferably constitutes the remainder of the build material. As such, the polymer blend may constitute from about <NUM>% to <NUM>% by weight of the build material, and more preferably from about <NUM>% to <NUM>% by weight. In some embodiments, the polymer blend constitutes from about <NUM>% to <NUM>% by weight of the build material, more preferably from about <NUM>% to <NUM>% by weight. In further embodiments, the build material consists essentially of the polymer blend, and optionally, one or more colorants and/or anti-oxidants and/or heat absorbing materials which typically are utilized with EP, SLS and HSS techniques.

In particular PEKK is a useful semi-crystalline polyaryletherketones PAEK relative to PEEK and PEK because PEKK has a higher Tg and improved thermo-oxidative stability relative to PEEK. Further, PEKK has excellent chemical resistance and high strength and stiffness, even without reinforcement additives.

When formulating a PEKK semi-crystalline build material, PEKK co-polymers of differing T/I ratios and viscosities can be blended to achieve balances between toughness, crystallinity and thermal capabilities. Stabilizers and fibrous fillers including, but not limited to, glass and carbon can be added to improve physical properties while inorganic agents can be added to manipulate the crystallinity of the build material. Exemplary inorganic agents include titanium dioxide, talc, mica, boron nitrate (BN), calcium carbonate, phosphates, sulfates, salts and combinations thereof Referring to <FIG>, PEKK sold by Arkema Inc. located in Phillidephia, PA under the Kepstan® <NUM> designation was utilized with BN as a nucleator. As illustrated, an HHS system could print items in the Tg to the Tc,hot range. However, an item using the same formulation could not be printed with an SLS technique because the energy required to melt the polymer with a laser would burn the material. HSS techniques allow for the modification of the temperature profile to be more gradual, then followed by a rapid cooling to the recited range.

Referring to <FIG>, an alloy of Kapstan® <NUM> and <NUM> designation manufactured by Arkema was blended with <NUM> parts of Kapstan® <NUM> to one part Kapstan® <NUM> with BN utilized as a nucleator. <FIG> illustrate that this alloy could potentially be utilized at about <NUM> which is above the lower melting point of the polymer, provided the crystallite is in the proper ratio.

All of the above mentioned polymer blends are also substantially homogenous, allowing each portion of the build material used in an additive manufacturing system to consistently exhibit the same thermal and physical properties. As such, if the polymer blend were otherwise non-homogenous, the build material would not be uniform. Additionally, a non-homogenous blend may result in imbalances in the crystallization kinetics of the build material, which could reduce the above-discussed benefits of controlling the crystallization kinetics. Further, non-miscible alloys are only strong as the interfacial adhesion between the two phases in the Z- axis meaning that non-miscible alloys are weak in the Z-direction. As such, miscible alloys or copolymers with controlled crystalline kinetics are desired. Accordingly, feed stock of the build material is preferably manufactured from a build material having a substantially homogenous polymer blend of the semi-crystalline polymer(s) and the secondary material. In embodiments that include one or more additives, the additive(s) are preferably dispersed in the polymer blend in a substantially uniform manner.

As mentioned above, the above-discussed method may also be utilized with electrophotography-based additive manufacturing systems, selective laser sintering systems and high speed sintering systems. With respect to electrophotography-based additive manufacturing systems, the build material may be provided in powder form for use in an electrophotography-based additive manufacturing system, such as those disclosed in <CIT> and <CIT>, and<CIT> and <CIT>.

As discussed in these references, the electrophotography-based additive manufacturing systems preferably operate with layer transfusion assemblies that transfuse each successively-developed layer based on interlayer polymer entanglement (i.e., reptation). As such, the above-discussed method for controlling the crystallization kinetics of the build material for the extrusion-based additive manufacturing systems may also be used in the same manner with the electrophotography-based additive manufacturing systems.

In comparison, however, SLS and HSS systems may print 3D items in which is held in a gelatinous, undercooled amorphous state between the hot melting temperature and the hot crystallization temperature of the nylon material. However, many semi-crystalline materials, such as nylon materials, typically have small temperature windows between their melting temperatures and the hot crystallization temperatures, rendering it difficult to hold the printed layers in this amorphous state after being melted with a laser beam.

As discussed above, it has been found that the substantially miscible blends for the build material of the present disclosure decrease the hot crystallization temperature Tc,hot of the build material from that of the semi-crystalline polymer(s). Conversely, the melting temperature Tm of the build material remains substantially unchanged. As such, the substantially miscible blend for the build material widens the operating window, referred to as operating window <NUM> in <FIG>, in which the printed layers may be held in the gelatinous, undercooled amorphous state to prevent warping and distortions. In this case, the powder materials may be selectively melted with the laser beam and held within this operating window <NUM> until the printing operation is completed. The whole 3D item <NUM> may then be cooled down in a conventional manner.

In embodiments involving the above-discussed technique used in a selective laser sintering system (e.g., systems disclosed in Deckard, <CIT> and <CIT>), the build material may be provided in powder form for use in other powder-based additive manufacturing systems.

HHS systems operate in a similar manner as SLS systems. However, heat is supplied to the material through radiation on thermal sources such as infrared(IR) heat, HHS devices and methods are disclosed in<CIT>.

Referring to <FIG>, the method of the present disclosure is illustrated at <NUM>. In step <NUM>, the technique used for additive manufacturing is selected. A non-exhaustive list of techniques includes extrusion based techniques, such as FDM, BAAM and OOO; EP, SLS and HSS.

At step <NUM>, the semi-crystalline material to be utilized to build the item is identified and the crystallization kinetics of the semi-crystalline material is identified. In the event that the crystallization kinetics require modification such that the heat of fusion is between about <NUM> J/g heat of fusion and about <NUM>% of the heat of fusion of a build material that is compositionally about <NUM>% of the semi-crystalline build material, as measured by differential scanning calorimetry (DSC) when cooling from the melting temperature to the hot crystalline temperature at a rate of <NUM>/min, a decision is required to either retard or accelerate the crystallization kinetics to utilize a build material that is within the identified heat of fusion range. The determination of whether to accelerate or retard the crystallization kinetics can be determined by obtain a DSC trace from a solid form to a melt temperature and cooled back to a temperature through which the material crystallizes using the DSC technique as described herein. However, other measurements and testing techniques besides DSC can be used to determine the heat of fusion of a particular semi-crystalline material.

Upon determining that the crystallization kinetics required to be slowed or retarded, a secondary material is added producing a build material that maintains the heat of fusion in the above-disclosed range during crystallization at step <NUM>. Typically, the secondary material can be a completely miscible, amorphous polymer to form the modified build material. Additionally, direct polymerization or selection of specially polymerized polymers, which are synthesized with disrupted structural regularity can be utilized. However, the present disclosure is not limited to the above-listed secondary materials.

At step <NUM>, a DSC trace is obtained to determine the Tg, Tc,cold, Tm, and Tc,hot on the modified build material. From the DSC trace on the modified semi-crystalline material, process conditions can be determined for extrusion based additive techniques, such as FDM, BAAM and OOO, and EP additive techniques by maintaining the material between approximately between about Tg and about Tc,cold and in the case of SLS or HSS the process conditions are maintained slightly below Tm, and about Tc,hot in step <NUM>. The amount of crystal formation in the build material is determined based upon the process conditions used, as the amount of crystal formation is on a continuum between the low temperature range and the high temperature range for both types of additive manufacturing techniques.

The item is then built in step <NUM> by the additive manufacturing technique identified in step <NUM>. Optionally, post build processing steps can be conducted, including, but not limited to additional annealing in step <NUM>.

Upon determining that the crystallization kinetics requires to be accelerated, a secondary material is added produce a build material that maintains the heat of fusion in the above-disclosed range during crystallization at step <NUM>. Typically, the secondary material include the addition of micron-scale additives, such as synthetic fibers, minerals (natural or synthetic), or by the addition of one or more immiscible secondary polymers, which are finely dispersed as a discrete phase through compounding techniques common in polymer processing. However, the present disclosure is not limited to the above-listed secondary materials.

At step <NUM>, a DSC trace is obtained under conditions described in step <NUM>. From the DSC trace obtained in step <NUM>, process conditions are identified in step <NUM> for a selected additive manufacturing technique described in step <NUM>. The item is built in step <NUM> as described in step <NUM> and optional, post build processing steps can be conducted in step <NUM> as described in step <NUM>.

The present disclosure is more particularly described in the following examples that are intended as illustrations only, since numerous modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise noted, all parts, percentages, and ratios reported in the following examples are on a weight basis, and all reagents used in the examples were obtained, or are available, from the chemical suppliers described below, or may be synthesized by conventional techniques.

A series of items were using an FDM printing technique where a FORTUS 400MC machine manufactured by Stratasys, Inc. located in Eden Prairie, Minnesota was utilized. The semi-crystalline build materials being tested in this Example included a co-polymer of poly(oxy-<NUM>,<NUM>-phenyleneoxy-<NUM>,<NUM>-phenylene carbonyl-<NUM>,<NUM>-phenylene) PEEK and the polyimide formed from <NUM>,<NUM>'-(<NUM>,<NUM>'-isopropylidene-diphenoxy)bis(phthalic anhydride) and <NUM>,<NUM>-phenylenediamine PEI.

The PEI is available commercially under the ULTEM ® <NUM> Resin series of polymers manufactured by SABIC Innovative Plastics located in Pittsfield, Massachusetts. The PEEK is available under the KetaSpire® KT-<NUM> resin series manufactured by Solvay Corporation located in Broxelles, Belgium or the Vitrex ® series <NUM> PEEK polymer manufactured by Victrix USA, Inc. locatedin West Conshohocken, Pennsylvania.

The materials were compounded on a twin-screw extruder Model Number ZSE <NUM> lab compounder, manufactured by Leistritz Aktiengesellschaft located in Nuremberg, Germany at a temperature between <NUM> and <NUM>. The formulations in Table <NUM> below were blended within <NUM>% at the stated relative weight percentages as set forth in Table <NUM>. After being compounded, the materials were extruded as strands, cooled and pelletized for further processing and analysis.

The materials in Table <NUM> along with neat PEEK (KT-<NUM>) were subsequently tested using DSC on a Model Number DSC <NUM> manufactured by PerkinsElmer, Inc. located in Waltham, MA. The samples were heated <NUM> /min until the melting temperature was obtained. The samples were then cooled at a rate of <NUM> /min. The results of the DSC testing are set forth in Table <NUM>, where all temperatures are in degrees Celsius. It is noted that the formulation designated PEEK-PEI <NUM> was reheated a second time and has data from the second run in parentheses.

The resulting formulations illustrate the compounding PEI with PEEK reduces the heat of fusion to between <NUM> and <NUM> and that there is a direct correlation between the amount of amorphous PEI added to the PEEK and the reduction the heat of fusion. It is also noted that the change in the heat of fusion is within the disclosed range as set forth above.

A series of "tee" bars were built using the FDM additive technique where a nominally dense (><NUM>% fill) "tee" bar is built with a second, removable material support structure to test the curl of the disclosed formulations. After annealing the "tee" bars for an additional amount of time, such as more than <NUM> hours after the build, the "curl" of each sample was is measured at the extreme ends of the sample (corners), after removal of the support material and the sample is cooled to room temperature.

It should be noted that an acceptable level of curl is <NUM>% over the length of the sample. Thus, for a <NUM> inch bar, a curl result of <NUM> mils or less is desired. Further, temperature gradients and build inaccuracies in R&D-scale materials and systems can lead to non-uniform results for one side of the bar vs. the other. The results of the "curl" test are set forth in Table <NUM>, below.

The data in Table <NUM> illustrates that where dimensional accuracy is critical, a PAEK (PEEK-PEI) material with substantially reduced crystallinity is preferred, at least where larger parts and higher temperatures are involved. In the more crystalline sample, even with substantial fiber filler, it was determined that the higher oven (quench) temperature of <NUM> allows too much crystallinity (stress and shrinkage) to develop to meet acceptable curl standards. Thus, a lower oven temperature is preferred, as this will help to quench out an additional fraction of the potential crystallinity, thus reducing overall shrinkage, and giving better dimensional control in a formulation that consists substantially of PEEK.

The materials were then tested for out of build plane strength (z-strength) when build an item using the FDM build technique. The samples were built using single FDM beads/roads with aspect ratio (width to height) between <NUM>:<NUM> and <NUM>:<NUM>. All samples were printed with a liquefier temperature between <NUM> and <NUM>, and at an appropriate temperature to control curl in large parts. The exception is neat PEEK which was printed at <NUM>. In all cases the layer Resolution was <NUM> mil. The results of this test are set forth in Table <NUM>, below.

A major increase in Z-strength up to and over PEI by itself with the addition of <NUM>% PEEK to PEI for predominantly PEEK alloys was observed. Further, it was observed that a reduction in the rapid crystallization inherent to PEEK alone has increased Z-strength significantly over the base PEEK, which could not successfully be built. For pure PEEK even in an environment kept at or below its Tg, the self-lamination strength is so weak that moderate stresses from differential shrinkage are enough to peel layers apart. It is believed this result occurs because PEEK crystallizes so fully and so rapidly that each subsequent layer of deposited material cannot input enough additional heat into the previous layer to fully re-melt all the crystallites and allow for meaningful interpenetration (diffusion/reptation) of polymer molecules.

The retardation of the crystallization of the build material, especially at low temperatures, is important for annealing parts to relieve stresses that lead to curl, in a semi-amorphous or pseudo-amorphous state in the FDM and/or EP additive techniques. <FIG> illustrates the crystallization half times, i.e. the time to reach a peak in the exotherm for recrystallization indicative of reaching approximately <NUM>% of the material's full level of crystallinty. Each of the PEEK-PEI alloys were rapidly heated at a rate of <NUM>/min to the isotherm temperature followed by a hold for up to <NUM> hours. PEEK data was obtained from the literature. It was observed that compounding PEEK with just <NUM>% PEI has a marked effect on the crystallization behavior of PEEK. It is noted that the tested compositions in Example <NUM> are not exhaustive and that system optimization and "tuning" of build parameters can further enhance the positive effects, including solidification without excessive crystallization, leading to better layer to layer bonding, and the ability to tailor the crystallinity in the finished item by enlarging a post-process annealing window at a higher temperature than the build temperature.

Example <NUM> illustrates that with some semi-crystalline build materials the crystallization kinetics are required to be accelerated to provide a suitable printed item. Acceleration of the crystallization kinetics can be advantageous when using polyetherketoneketone PEKK as a build material. PEKK is commercially available as a series of copolymers based on a chemistry in which "straight" co-monomers, i.e. <NUM>,<NUM> or para substituted moieties may be substituted for "kinked" co-monomers, i.e. <NUM>,<NUM> or meta substituted moieties which can be introduced carefully (and under manufacturer's proprietary techniques) to reduce the melting point of a purely <NUM>,<NUM> substituted material. A purely <NUM>,<NUM> phenylene polymerized polymer has a melting point near <NUM>, which is also in a range where material viscosity becomes unstable, and thermal degradation begins to occur relatively rapidly. Thus, using such a technique to lower the polymer's melting point is useful. It is also useful in additive manufacturing processes, as a side effect of the copolymerization is a reduction in melting point, and also a reduction in recrystallization temperatures and crystallization rates, both upon heating and cooling.

In Example <NUM>, the materials utilized are Solvay KetaSpire KT-<NUM> PEEK as discussed in Example <NUM> and Kepstan® <NUM> and <NUM> and Kepstan® <NUM> PEKKs all manufactured by Arkema Inc. located in Philadelphia.

The materials in Table <NUM> were subsequently tested using DSC on Model Number DSC <NUM> manufactured by PerkinsElmer, Inc. located in Waltham, MA. The samples were heated <NUM>/min until the melting temperature was obtained. The samples were then cooled at a rate of <NUM>/min. The results of the DSC testing are set forth in Table <NUM>, where all temperatures are in degrees Celsius.

The DSC results from Table <NUM> illustrate that it is possible to appreciably modify the crystallization behavior of pseudo-amorphous PEKK to achieve similar crystallinity reductions as in the PEEK-PEI alloys described in Example <NUM>. In these cases, acceleration of the "slow" Kepstan <NUM> is the desired result. One strategy involves the addition of a much more crystalline, and more rapidly crystallizing PEKK copolymer, Kepstan® <NUM>. In the <NUM> and <NUM> copolymers, it was observed that the addition of the Kepstan® <NUM> PEKK can increase the relative crystallinity of a blend based on Kepstan® <NUM> to between <NUM> and <NUM> percent of the enthalpy observed cooling at <NUM> C from the melt vs. the neat Kepstan® <NUM> material.

Another strategy that can be employed to increase the crystallization rate and amount of the Kepstan® <NUM> polymer was to introduce a less compatible polymer, such as, but not limited to, PEEK, which should crystallize more rapidly, and exist as a discrete phase that "precipitates from solution" upon cooling from the melt. The above DSC data shows that a <NUM>% PEEK loading has increased the relative crystallinity of a PEKK copolymer from <NUM>% to as much as <NUM>%. The relatively low result in the <NUM>% PEEK alloy may be due to the low loading level, incomplete mixing, or a slight degree of miscibility between the two polymers that necessitates adding much higher levels to achieve appreciable effects.

Referring to <FIG>, dynamic mechanical analysis (DMA) of the formulations designated N1 and N3 in Table <NUM> provides evidence of enhanced crystallinity and crystallization rate through modulus development during when a temperature is increased over time. The data in <FIG> illustrates slight, and subtle differences between <NUM>% and <NUM>% PEEK alloys with Kepstan <NUM> (N1 and N3). The data graphically illustrate that the <NUM>% PEEK loading was more effective in increasing modulus at temperatures approaching and exceeding the Tg, which is important for FDM part construction and annealing. If the modulus of the part were only slightly above the Tg, excessive part warping and distortion would occur from annealing processes. The following data also graphically illustrates that increasing oven temperature (quench temperature) can subtly, but significantly affect the modulus of the printed parts, thus allowing them to be printed in an environment that is above the Tg of the semi-crystalline polymer, but below the melting point.

Due to the controlled crystallization kinetics, the material does not crystallize as fast, and the material is allowed to stay molten for longer. As such items printed with controlled crystallization kinetics are more dense, while maintaining feature definition.

While others may be able to achieve the densities achieved with the control crystallization kinetics, other processes will lose downward facing definition and aesthetics.

The present disclosure allows an SLS device to produce an item with isotropic properties and with feature detail. Currently SLS devices cannot print an item with isotropic properties and feature detail. Rather one is compromised for the other
Due to the suppression of the hot crystallization temperature using the formulations set forth herein, the part bed can be maintained at lower temperatures, and have a higher gradient between the powder temperature and the lasered part, without worrying about feature growth. The present disclosure provides superior printed items relative to parts printed with semi-crystalline polymers without the secondary material.

Claim 1:
A polymeric material comprising:
a semi-crystalline polymer having an enthalpy of fusion of greater than <NUM> J/g, when measured from above a melting temperature to below a hot crystallization temperature of the polymer; and
a secondary material or materials wherein when the secondary material or materials are combined with the semi-crystalline polymer to form a blend that increases an enthalpy of fusion to at least <NUM> J/g when cooled at a rate of <NUM>/min as measured by differential scanning calorimetry (DSC) when cooling from above the melting temperature to below the hot crystalline temperature; and
wherein the polymeric material is a consumable feedstock material configured for use in an additive manufacturing system (<NUM>) for printing three-dimensional parts (<NUM>,<NUM>) in a layer-by-layer manner; and
wherein the secondary material comprises one or more amorphous polyetherketoneketones (PEKK) and the semi-crystalline polymer comprises one or more semi-crystalline polyetherketoneketones (PEKK).