WO2017127027A1

WO2017127027A1 - Method of manufacturing a customized interface component for a device

Info

Publication number: WO2017127027A1
Application number: PCT/SG2017/050033
Authority: WO
Inventors: Ivan Chandra SURIADY; Norman Julius WANTO
Original assignee: Inspirate Medical Pte. Ltd.
Priority date: 2016-01-20
Filing date: 2017-01-20
Publication date: 2017-07-27

Abstract

A method of manufacturing a customized interface component for a device such as a mask is disclosed. The method comprises: obtaining three dimensional subject model data representing part of human subject; generating interface mandrel data from the three dimensional subject model data; forming a customized mandrel using the interface mandrel data; and forming the customized interface component for the device using the customized mandrel. The customized mandrel may be formed by three dimensional printing. In some embodiments the customized interface component is formed from an elastomer such as silicone by dip moulding in an elastomer dispersion. A material that is resistant solvents present in the elastomer dispersion such as nylon may be used to form the mandrel.

Description

Method of manufacturing a customized interface component for a device

FIELD OF THE INVENTION Embodiments of the present invention relate to manufacturing customized interface components for devices such as masks which are customized to fit a human subject.

BACKGROUND OF THE INVENTION Personalized, customized medical devices have the potential to offer better fit and efficacy as compared to traditional, mass-produced devices. This is especially true in the case of continuous positive airway pressure (CPAP) masks, where interface fit is an important requirement for treatment effectiveness. Non-fitting masks result in uneven pressure being exerted across the patient's face, inflicting pain at particular points, while leaking at other points. Full-face CPAP masks are particularly prone to these problems, as the large interface contact area means that the mask has to accommodate a great variation of facial shapes and features. There is thus a strong reason to believe that customization will improve mask fit, and consequently, treatment efficacy and compliance.

Despite these possible benefits, customization is usually constrained by higher costs of production and longer production time.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided a method of manufacturing a customized interface component for a device. The method comprises: obtaining three dimensional subject model data representing part of human subject; generating interface mandrel data from the three dimensional subject model data; forming a customized mandrel using the interface mandrel data; and forming the customized interface component for the device using the customized mandrel. l The customized interface component may be formed from an elastomeric material. Thus the formation of the customized interface component for the device using the mandrel comprises dip coating the mandrel in an elastomer dispersion to form the interface component.

Embodiments of the invention provide a rapid method of manufacturing a customized interface component for a device such as a mask.

The elastomer dispersion may comprise a silicone dispersion. The elastomer dispersion may comprise a solvent and the customized mandrel is formed from a material resistant to the solvent.

Examples of possible solvents include xylene, ethylbenzene, naphtha. The dip coating process to form the interface component may comprise a plurality of dipping cycles, each dipping cycle of the plurality of dipping cycles comprising dipping the mandrel in the elastomer dispersion; removing the mandrel from the elastomer dispersion and allowing the elastomer dispersion to devolatilize. In some embodiments, at least one of the dipping cycles of the plurality of dipping cycles comprises a partial dipping cycle in which only a part of the mandrel on which the interface component is to be formed is dipped into the silicone dispersion. This allows the thickness of the interface component to vary at different points. In some embodiments, a final dipping cycle of the plurality of dipping cycles comprises a full dipping cycle in which all of the mandrel on which the interface component is to be formed is dipped into the silicone dispersion. If the final dipping cycle is a full dipping cycle, the smoothness of the final surface of the interface component can be improved. In an embodiment allowing the elastomer dispersion to devolatize comprises exposing the mould to an airflow. The airflow may be a heated airflow. Such embodiments allow the devolatilization process to be speeded up. Allowing the elastomer dispersion to devolatilize may comprise rotating the mandrel around at least one axis while allowing the elastomer dispersion to devolatilize. Rotation of the mandrel during the devolatilization process helps to ensure that the interface component has an even thickness. This is because the elastomer dispersion can drip while it is wet; therefore, the mandrel is rotated while the elastomer dispersion is dried and / or cured.

In some embodiments the method further comprises curing the interface component after dip coating. The curing process may involve heating the interface component to temperatures of at least 120 degrees Celsius.

In some embodiments the customized mandrel is formed from a material comprising nylon. Nylon has been found to be a suitable material the mandrel since it is resistant to solvents such as xylene and is also able to withstand temperatures involved in the devolatilization and curing processes.

The device may be a mask such as a continuous positive airway pressure mask. In such embodiments, the three dimensional subject model data represents part of a face of the human subject.

The mandrel may formed by three dimensional printing. The mandrel may be three dimensional printed using nylon filament. In some embodiments, the nylon filament is heat treated prior to three dimensional printing. The nylon filament may be heat treated again after the three dimensional printing. The reason for this is as follows. Nylon easily absorbs atmospheric moisture. The curing and devolatilization process involves heat, an untreated nylon mould may release steam during the curing/ devolatilization process, resulting in bubbles on the silicone.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, embodiments of the present invention will be described as non- limiting examples with reference to the accompanying drawings in which: Figures 1A and 1 B show a continuous positive airway pressure (CPAP) mask comprising an interface component manufactured according to an embodiment of the present invention Figure 2 shows a method of manufacturing a customized interface component for a device according to an embodiment of the present invention; and

Figure 3 shows a method of manufacturing a CPAP mask according to an embodiment of the present invention.

DETAILED DESCRIPTION

Figures 1A and 1 B show a continuous positive airway pressure (CPAP) mask comprising an interface component manufactured according to an embodiment of the present invention. Figure 1A shows the assembled CPAP mask and Figure 1 B is an exploded view showing the components of the CPAP mask.

The CPAP mask 100 can be considered as two main parts: a solid frame component 120 made of polycarbonate or other hard plastics material and a soft cushion or interface component 140 made of silicone or other soft elastomer material. The frame component 120 gives form to the mask 100, and houses the fittings that connect the mask 100 to a CPAP pump device and headgear. The cushion or interface component 140 is the interface between the frame component 120 and the patient's face when the mask 100 is worn. Thus, it is the interface component 140 that is more important in establishing and ensuring fit and comfort. For this reason, in embodiments of the present invention the interface component 140 is customized to fit the patient or subject's face.

The frame component 120 has four strap fittings 122 which allow straps or headgear to be attached to the mask 100. As shown in Figure 1 B, when the mask 100 is assembled, the interface component 140 fits inside the frame component 120. In other masks, the silicone piece 140 is attached to frame component 120 either with glue and / or with a physical mechanism. The interface component 140 has an edge section 142 that is shaped to fit against the face of a patient. The mask 100 shown in Figures 1A and 1 B is a full face CPAP mask and so the interface component 140 is shaped to fit over the mouth and nose of the patient. In some embodiments the mask is a nasal mask. In such embodiments, the interface component is configured to fit over the nose of the patient. A plurality of vent holes 144 are located on the top of the interface component 140 close to where the patient's nose when the mask 100 is worn. There is a circular hole 146 in the interface component 140 opposite the opening formed by the edge section 142.

A ring-shaped plastic part 150 fits into the circular hole 146 in the interface component 140. An elbow connector 160 fits into the ring-shaped plastic part 150. The elbow connector 160 allows a hose connecting the interface component 140 to the CPAP pump device to be connected at 90 degrees with respect to the interface component 140. The connection between the ring-shaped plastic part 150 and the elbow connector 160 allows the elbow connector 160 to be rotated through 360 degrees with respect to the interface component 140. The elbow connector 160 has a set of holes 162 which serve as an air exhaust. A silicone flap 164 is located over the opening of the elbow connector 160 which connects to the ring-shaped plastic part 150. The silicone flap 164 functions as an anti-backflow flap and prevents air breathed out by the patient from re-entering the hose connecting to the CPAP pump device. The presence of the silicone flap 164 thus prevents the carbon dioxide content of the breathing space from rising due to backflow of exhaled air into the connecting hose.

The elbow connector has a small port which is covered by a silicone cap 166. The small port may be used to introduce extra oxygen into the breathing space or to test for carbon dioxide concentration. A hose connector 170 couples to the elbow connector 160. The hose connector 170 allows the hose connecting the mask 100 to the CPAP pump device to be rotated through 360 degrees with respect to the elbow connector 160. Figure 1 B also shows a strap 80 which is worn over the patient's head to hold the mask 100 in place. A plastic clasp 182 attaches the strap 180 to the strap fittings 122 of the frame component 120. The length of the strap 180 is adjustable using Velcro fasteners.

As described above with reference to Figures 1A and 1 B, in order to customize a device such as a CPAP mask to a wearer or subject, the shape of an interface component 140 can be customized to fit a part of the body of the subject. Figure 2 shows a method of manufacturing a customized interface component for a device according to an embodiment of the present invention.

In step 202, three dimensional subject model data is obtained for the subject. The three dimensional subject model data represents part of the body of the human subject. The part of the body of the subject is the part for which the device is intended to be customized. For example, if the device is a mask, then the three dimensional model data represents the face of the subject. Step 202 may be carried out by scanning the part of the body of the subject to obtain the three dimensional subject model data. In some embodiments, the scanner also measures the dimensions of the face. This means that extra measurements are unnecessary.

In step 204, the three dimensional subject model data is processed to generate mandrel data. The processing may involve orientating the three dimensional subject model data using particular identification points such as the eyes or the tip of the nose of the subject. The mandrel data generated in step 204 may include features of a mandrel such as a connection point to allow the mandrel to be connected to a dip moulding mechanism.

In step 206, a customized mandrel is formed using the mandrel data generated in step 204. Step 206 may comprise 3D printing the mandrel data using a 3D printer. Alternatively another rapid customization technique such as computer numerical control (CNC) may be used in step 206. Examples of possible alternative rapid customization methods include: selective laser sintering; stereolithography; fused deposition modelling; and computer numerical control machining.

In step 208, the customized mandrel is used to form a customized interface component for the device. Step 208 may comprise dip moulding the customized mandrel in an elastomer dispersion such as a silicone dispersion.

A process of manufacturing a CPAP mask including a customized interface component will now be described with reference to Figure 3.

In step 302, the face of the patient or subject is scanned with a 3D scanner. The customisation process begins by scanning the patient's face using a 3D scanner such as a 3DSense 3D scanner. In some embodiments, only the front profile is scanned as the back of the head is unnecessary in customising the mask. The scanning process takes approximately 30 seconds. The scanning process may be repeated 3 times to ensure that there is at least one usable scan result. It has been found that usually all scans are directly usable; however the redundancy can be used as a safety measure. The scan process is carried out about 70 cm from the patient, and involves no direct physical contact. The result of the scan is a 3D mesh that is shaped and scaled exactly as the subject's face. This 3D mesh is the input for the next step of the process.

In step 304, the 3D mesh is processed to form a mask mould or mandrel. The 3D mesh is imported into a surface modelling program such as Rhinoceros. In an implementation, a plugin called Grasshopper is used to procedurally generate a mould or mandrel for the silicone part using the cleaned 3D mesh as the input. With this procedural generation capability, most of the production process is automated.

A mould generation algorithm first orients the facial mesh to a pre-set direction, and also positions the mesh to have the nose and mouth fit within the area of the mask. This requires an operator to identify 3 points on the mesh. These three points may be: the tip of the nose, the left pupil, and the right pupil. The mould generation algorithm generates a mask surface that runs tangentially against the face mesh. The facial features are fully preserved and copied onto the model. The algorithm may also generate support structures that form the entirety of the silicone part. At this point, an operator may visually check for fit and accuracy, and several parameters may be adjusted as needed to modify the part.

The customised part becomes a mould or mandrel for casting the silicone part; it is exported as an STL file. This STL file is imported into a 3D-printer slicing program, such as Cura, which converts the mould model into a G-code file. The G-code file is a set of printing instructions that is recognizable by a 3D printer.

In step 308 the mask mould, or mandrel, is printed using a 3D printer.

The mould or mandrel is printed using a desktop 3D printer and a 3mm nylon filament. In one implementation an Ultimaker 2 desktop 3D printer is used. Nylon is used because it resists the harsh conditions required for the silicone moulding process. In one implementation, the type of nylon used is Nylon 680, which is an FDA-approved material for indirect food contact. This is beneficial because it does not use any chemical additives, and is sterilisable using steam or ethylene oxide. While the material will not be used in the final product, this minimizes the possibility of contaminating the CPAP mask itself. Before printing, the nylon filament is pre-processed in step 306 by heating the filament in a 150 degrees Celsius oven for at least 3 hours to remove any moisture that the filament has absorbed. Preheating prevents 3D printer nozzle blockage due to the release of steam from the filament, and also changes the nature of the filament from flexible to more crystalline. When the mould is more crystalline, printing imperfections are easier to remove, resulting in a cleaner mould surface. After preprocessing, the filament is fed into the printer. The nozzle temperature is 250 degrees Celsius, while bed temperature is 70 degrees Celsius. In this implementation, the nozzle fan is not used, and the bed which may be formed from tempered glass is lined with an adhesive, such as a polyvinylpyrrolidone glue stick, to improve printed object adhesion. Printing the mould takes approximately 10 to 12 hours. After 3D printing, the printed mould is cleaned with running water to remove the glue stick. Then in step 310 the mould is heat treated in an oven at 150 degrees Celsius for at least 1 hour to remove all leftover moisture. This is to prevent moisture release during the dip moulding process which can cause silicone bubble formation. After cooling the mould for 5 minutes to approximately room temperature, in step 312, a medical grade mould release agent is lightly coated over the mould.

The mould is then installed on a dip moulding mechanism and in step 314, the mould is dipped into a silicone dispersion. The dip moulding process uses a medical grade dispersion of silicone in xylene to build up a thick (2~4mm) layer of silicone over the mould.

The dip moulding mechanism automates the dipping process while ensuring accuracy, reliability, and repeatability of the process. The silicone dispersion is prepared by mixing the two-part silicone dispersion with equal weight for each part. It is mixed thoroughly using a clean metal spatula in a clean metal container. After mixing, bubbles within the dispersion mixture are removed by resting it in a vacuum chamber set at 0.1 ATM for at least 10 minutes. Upon visual confirmation that there are no more bubbles, the vacuum is released and the silicone dispersion container is placed onto the dip mechanism. Otherwise, the vacuum procedure is repeated. In the case of a one-part silicone dispersion, mixing is not necessary and the silicone dispersion container is placed directly in the vacuum chamber.

During the dipping process, at times, the silicone may be diluted by introducing fresh xylene into the mixture, mixing it, and then vacuuming it to remove bubbles. This is because as the dispersion is used, the amount of xylene it contains decreases due to evaporation to the environment. Mixing is an important step because the top layer of the dispersion usually contains a higher proportion of silicone solids. This is because it is a boundary layer through which xylene evaporates. At this boundary layer, xylene is not replaced fast enough by diffusion from the bulk of the mixture.

The amount of xylene to be replaced is equal to the amount that has evaporated, calculated by multiplying the area of dispersion surface by rate of evaporation and by the duration of time that the silicone can is open.

In step 314, the prepared mould is vertically dipped fully into the silicone dispersion. Following dipping in the silicone dispersion, in step 316, the mould is slowly removed from the dispersion to ensure an even coating. It is lifted up slowly - the speed at which it is lifted should be slower than the speed at which the dispersion flows down a vertical flow. In embodiments a speed of less than 1cm per minute has been found to be effective. Once the mould clears the top of the container, it is moved to a horizontal position. Once horizontal, the mould is rotated continuously along the horizontal axis to prevent the still-wet dispersion from flowing down, which may result in varying silicone thicknesses.

Each time the mould is dipped into the dispersion and lifted out of it, a thin layer of silicone dispersion adheres on the mould. This layer of dispersion is allowed to devolatilize - to remove the volatile xylene content by means of evaporation. High air flow around the mould and elevated temperatures are used to expedite this process and ensure complete removal of xylene. The devolatilization process takes place in steps 318, 320, 322 and 324. In step 318, for the first 5 minutes, devolatilization is carried out at room temperature using only a steady stream of air. In step 320, for the second 5 minutes, 50 degrees Celsius hot air is blown instead to increase devolatilization speed and extent. Then, in step 322 for 15 minutes, devolatilization is carried out using 80 degrees Celsius air. Finally, in step 324 for the final 15 minutes, the mould is placed in a 120 degrees Celsius conventional oven for complete removal of xylene in addition to partial cure. After a 5-minute rest period, in which the mould cools down to near room temperature, the dipping process is repeated to a total of 5 times, or until an approximate thickness of 2 mm is achieved. In step 326 it is determined whether the layer of silicone is thick enough and the method either returns to step 314 where the mould is again dipped in the silicone dispersion or moves to step 328. This determination may be done by eye.

In some embodiments a series of dips and partial dips into the silicone dispersion are carried out. The use of partial dips makes it possible to vary the thickness within the same silicone piece.

In one embodiment, it is desired to have the interface part 142 to be thinner than the 'supporting' part that is the rest of part 140 as shown in Figures 1A and 1 B. To achieve such an interface part, the mould is angled in such a way that the part 142 is on top. Then dip the mould is dipped into the silicone, stopping short of dipping part 142. Then the mould the mould is lifted, again, slowly at approximately 1 cm per minute. It is noted that the final dip of the whole production process should be a whole dip such that the whole interface part is dipped into the silicone dispersion. This has been found to make the final texture more even.

In one embodiment the dipping cycle comprises: 4 full dips, followed by 5 partial dips, and finally 1 full dip. This has been found to give a good balance of solididity, strength, and comfort. In step 328, after building up a thick layer of silicone by multiple dipping, the silicone is cured at 150 degrees Celsius for at least 2 hours, in the example shown in Figure 3, the curing is done for 3 hours.

As described above, the dip moulding and curing process is done using harsh conditions: temperatures as high as 150 degrees Celsius and the usage of xylene, a solvent which is able to dissolve many types of plastics. As such, it becomes necessary to use a material such as nylon as the material for the mould. Nylon is easily able to handle these temperatures without softening, unlike other 3D-printable materials.

Following step 328, the mould along with the cured silicone piece is removed from the dipping mechanism.

In step 330, the cured silicone piece is then trimmed manually by running a pen knife perpendicularly along a cutting guide, which has already been printed directly on the mould. At this stage, the silicone is still sticking onto the mould.

In step 332, the silicone piece is manually peeled off the mould, and becomes 2 separate pieces of silicone; the unused one is discarded. The removal of the silicone piece from the mould may be made easier by the application of mould release; otherwise the silicone will stick tightly and require a lot of force for removal.

In step 334 the silicone piece is cured in an oven for one hour to remove any remaining solvent. The curing in step 334 may take place at a temperature in the range 130 to 180 degrees Celsius, for example 150 degrees Celsius. In step 336 the silicone interface piece is washed and dried and assembled into a mask. The removed silicone piece is one that exactly fits the facial contours of the scanned patient. The silicone piece is then cleaned by washing it in boiling clean water for 5 minutes, then by cleaning with isopropyl alcohol. It is then fully dried by placing it in a 150 degrees Celsius oven for at least 15 minutes. Assembly is done by simply fitting the silicone piece over a fitting on the solid part. The headgear is then fitted over the mask, marking the end of the production process. Whilst the foregoing description has described exemplary embodiments, it will be understood by those skilled in the art that many variations of the embodiment can be made within the scope and spirit of the present invention. For example, in the examples described above, the device which is manufactured is a mask with a customized interface customized. However, the methods described above can also be applied to the manufacture of customized interface components for other types of device. For example the methods described above may be used to manufacture interface components for other types of mask such as breathing masks worn by pilots. The methods described above may also be used to manufacture interface components for other devices which are worn on the body, for example, prosthetics. Thus in some embodiments, the interface component may form a prosthetic liner which forms the interface between a stump or residual limb and the prosthetic. In such embodiments, the fit of the interface component is important as it determines comfort of the prosthetic.

Further embodiments of the present invention are set out in the following clauses: 1. A method of creating an elastomeric interface that is customised to the wearer's body part so as to ensure exact fit.

2. The method of clause 1 comprising of the steps of scanning the patient's body part, converting the 3D model into a mould, 3D-printing said mould, dip-moulding said mould to produce a customised interface between the device and the patient's face, and assembling said interface into a medical device.

3. The method of clause 2 wherein the 3D model is converted into a mould model for the silicone piece using a 3D-modelling computer program.

4. The method of clause 3 wherein the mould model includes grooves, fittings, and attachment points required for the subsequent dip-moulding process.

5. The method of clause 2 wherein the mould is 3D-printed using nylon as the printing material, because nylon is able to withstand the high temperatures needed for curing the elastomer piece, and does not soften or dissolve in the solvents used in the elastomer dispersion. 6. The method of clause 5 wherein the nylon filament is pre-processed by drying in an oven or other suitable heating mechanisms before being 3D-printed.

7. The method of clause 2 wherein the mould is dip-moulded to form an elastomeric skin that forms the device-wearer interface.

8. The method of clause 7 wherein the 3D-printed mould is pre-processed by drying in an oven or other suitable heating mechanisms before dip-moulding, in order to prevent the evolution of bubbles during the dip-moulding process.

9. The method of clause 7 wherein a medical grade elastomer dispersion, such as a dispersion of silicone in xylene, is used as the dipping material.

10. The method of clause 7 wherein the mould is dipped several times through a cycle of dipping - devolatilizing - dipping to build up elastomer thickness.

11. The method of clause 10 wherein devolatilizing the mould is done by exposing the dipped mould to a wind flow of elevated temperature to speed up the process. 12. The method of clause 10 wherein the dipping and devolatilizing of the mould is done in an enclosure with ample air exhaust flow to remove the evaporated solvent from the work area.

13. The method of clause 10 wherein the mould is rotated along 1 , 2, or 3 axes during devolatilization to promote the creation of an even skin.

14. The method of clause 7 wherein the elastomer skin forming around the mould is cured by placing the whole mould in an oven or other suitable heating mechanisms.

15. The method of clause 2 wherein the elastomer piece is removed from the mould by peeling. 16. The method of clause 2 wherein the elastomer piece is post-processed by heating in the oven, boiling in water, or steaming in water or EtOH, or other suitable methods, to remove residual solvents as well as to clean the elastomer piece. 17. The method of clause 2 wherein the elastomer piece is trimmed and fitted into the other parts of the medical device.

18. A customised device for applying CPAP treatment, the device comprising plastic housing attached to an elastomeric interface, wherein the interface configured to exactly match the facial features of the wearer.

Claims

1. A method of manufacturing a customized interface component for a device, the method comprising:

obtaining three dimensional subject model data representing part of human subject;

generating interface mandrel data from the three dimensional subject model data;

forming a customized mandrel using the interface mandrel data; and

forming the customized interface component for the device using the customized mandrel.

2. A method according to claim 1 , wherein forming the customized interface component for the device using the mandrel comprises dip coating the mandrel in an elastomer dispersion to form the interface component.

3. A method according to claim 2 wherein the elastomer dispersion is a silicone dispersion.

4. A method according to claim 2 or claim 3 wherein the elastomer dispersion comprises a solvent and the customized mandrel is formed from a material resistant to the solvent.

5. A method according to any one of claims 2 to 4, wherein dip coating the mandrel in an elastomer dispersion to form the interface component comprises a plurality of dipping cycles, each dipping cycle of the plurality of dipping cycles comprising dipping the mandrel in the elastomer dispersion; removing the mandrel from the elastomer dispersion and allowing the elastomer dispersion to devolatilize.

6. A method according to claim 5 wherein at least one of the dipping cycles of the plurality of dipping cycles comprises a partial dipping cycle in which only a part of the mandrel on which the interface component is to be formed is dipped into the silicone dispersion.

7. A method according to claim 6 wherein a final dipping cycle of the plurality of dipping cycles comprises a full dipping cycle in which all of the mandrel on which the interface component is to be formed is dipped into the silicone dispersion.

8. A method according to any one of claims 5 to 7, wherein allowing the elastomer dispersion to devolatilize comprises exposing the mould to an airflow.

9. A method according to claim 8, wherein the airflow is a heated airflow.

10. A method according to any one of claims 5 to 9, further comprising rotating the mandrel around at least one axis while allowing the elastomer dispersion to devolatize.

11. A method according to any one of claims 2 to 10, further comprising curing the interface component after dip coating.

12. A method according to any preceding claim wherein the customized mandrel is formed from a material comprising nylon.

13. A method according to any preceding claim wherein the device is a mask and the three dimensional subject model data represents part of a face of the human subject.

14. A method according to claim 13 wherein the mask is a continuous positive airway pressure mask.

15. A method according to any preceding claim wherein forming a customized mandrel using the interface model data comprises three dimensional printing the customized mandrel using the interface mandrel data.

16. A method according to clam 15, wherein three dimensional printing the customized mandrel using the interface mandrel data comprises three dimensional printing the customized mandrel using nylon filament.

17. A method according to claim 16, further comprising heat treating the nylon filament before three dimensional printing the customized mandrel.

18. A method according to claim 17, wherein heat treating the nylon filament before three dimensional printing the customized mandrel comprises heating the nylon filament to a temperature of at least 200 degrees Celsius.