DEPOSITION PRINT HEAD

Abstract

A deposition print head including a non-susceptive or low susceptive sleeve, a susceptive element having a filament channel, the susceptive element arranged inside the sleeve, wherein the susceptive element is susceptive for at least one of a magnetic field and an electrical field, wherein the filament channel is for feeding a thermoplastic filament in a feed direction. The deposition print head further includes an exciter arranged around the susceptive element, wherein the exciter is arranged for generating a field compatible with the susceptivity of the susceptive element, and a nozzle attached to one end of the susceptive element.

Claims

1. A deposition print head comprising; a non-susceptive or low susceptive sleeve; a susceptive element disposed inside the sleeve, wherein the susceptive element has a filament channel is for feeding a thermoplastic filament in a feed direction; an exciter disposed around the susceptive element, wherein the exciter comprises an induction coil wound around the sleeve for generating an alternating magnetic field compatible with the susceptivity of the susceptive element, wherein the susceptive element comprise a ferromagnetic material; a nozzle attached to one end of the susceptive element; wherein the sleeve comprises at least one additional susceptive element, wherein the exciter overlaps the at least one additional susceptive element.

2. (canceled)

3. (canceled)

4. (canceled)

5. (canceled)

6. (canceled)

7. (canceled)

8. (canceled)

9. (canceled)

10. The deposition print head (100) according to claim 1, further comprising a spacing element between each pair of susceptive elements.

11. The deposition print head according to claim 1, wherein the exciter is subdivided in a portion per each susceptive element.

12. The deposition print head according to claim 11, wherein the exciter has a different energy transfer ratio for each portion of the exciter.

13. The deposition print head according to claim 11, wherein the exciter has a different number of windings for each portion of the exciter.

14. (canceled)

15. The deposition print head according to claim 11, wherein each exciter portion is provided with a separately controllable power supply. (new 6)

16. (canceled)

17. (canceled)

18. The deposition print head according to claim 1, further comprising at least one temperature sensor arranged in close proximity to the filament channel.

19. (canceled)

20. A deposition printer, comprising holding means for holding an article to be deposition printed; positioning means; and control means for controlling a position of the positioning means; a deposition print head assembly, attached to the positioning means, comprising a support structure and at least one deposition print head according to claim 1.

21. A method of deposition printing using the deposition print printer according to claim 20, comprising the steps of: feeding a thermoplastic filament in a feed direction through a filament channel, melting the thermoplastic filament; positioning the deposition print head according to a predetermined pattern; depositing the molten thermoplastic filament for creating an object; and activating the respective exciter portions for each susceptive element of the deposition print head at a different energy level according to a temperature profile.

22. (canceled)

23. (canceled)

24. The method according to claim 21, wherein the temperature profile has an ascending temperature slope and subsequently a descending temperature slope in the feed direction.

25. The method according to claim 24, further comprising first preheating the thermoplastic filament to a gel temperature, second preheating the thermoplastic filament to a temperature above a melt temperature, and third heating the thermoplastic filament to the melt temperature.

26. The method according to claim 25, further comprising buffering the thermoplastic filament between second preheating and the third heating using a spacing element.

27. The method according to claim 21, further comprising controlling a filament temperature using a temperature sensor.

28. The deposition printer according to claim 20, wherein the deposition print head assembly comprises a vessel having at least one deposition print head, wherein the vessel is provided with a coolant inlet and a coolant outlet.

29. The method according to claim 20, further comprising cooling the at least one deposition print head using a coolant.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1a shows a cross section of a deposition print head according to an embodiment according to the invention.

[0039] FIG. 1b shows a side view of the deposition print head according to the invention.

[0040] FIG. 2a shows a susceptive element according to an embodiment according to the invention.

[0041] FIG. 2b shows a susceptive element and nozzle according to an embodiment according to the invention.

[0042] FIG. 2c shows a spacing element according to an embodiment according to the invention.

[0043] FIG. 2d shows a sleeve according to an embodiment according to the invention.

[0044] FIG. 3a shows a deposition print head according to the embodiment according to the invention.

[0045] FIG. 3b shows a side view of the deposition print head of FIG. 3a according to an embodiment according to the invention.

[0046] FIG. 4a shows a cross section of a further embodiment of the deposition print head according to the invention.

[0047] FIG. 4b shows a side view of the deposition print head of FIG. 4a according to an embodiment according to the invention.

[0048] FIG. 5 shows a deposition print head assembly according to an embodiment according to the invention.

[0049] FIGS. 6a and 6b show temperature profiles according to embodiments of the invention.

[0050] FIG. 7a shows an arrangement of parts of a deposition print head according to an embodiment of the invention.

[0051] FIG. 7b shows a side view of the arrangement of FIG. 7a.

[0052] FIG. 8 shows a block diagram of temperature control of a deposition print head according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0053] FIG. 1a shows a cross section of a deposition print head 100 having a sleeve 102, a susceptive element 103, an exciter 105 and a nozzle 106. The susceptive element 103 is arranged inside the sleeve 102. The susceptive element 103 has a tubular shape leaving a channel 104 for allowing feed through of thermoplastic filament. The exciter 105 is arranged around the susceptive element 103. The nozzle 106 can preferably be attached to the susceptive element 103, but can also be attached to the sleeve 102. The exciter 105 is connectable to an energy source such as an electric power supply, and when supplied it generates a field compatible with the susceptive element 103.

[0054] The exciter 105 can be an induction coil combined with a ferromagnetic tubular element as susceptive element 103. Ferromagnetic materials for the susceptive element 103 include iron, iron alloys. Also materials with low conductivity can be used such as steel, carbon, tin, tungsten, which cause heating up by means of eddy currents induced by the magnetic field from the exciter 105.

[0055] When activated using an alternating voltage or current supply, the exciter generates an alternating magnetic field. The susceptive element 103 captures the alternating magnetic field. Due to hysteresis of the ferromagnetic material of the susceptive element 103 and/or the eddy currents as described, the susceptive element 103 heats up. The thus heated susceptive element 103 heats the thermoplastic filament fed through the filament channel 104 to a melting temperature of the thermoplastic material of the filament. The feeding causes sufficient pressure to cause the molten filament to be pressed towards the nozzle 106, where it is extruded. By continuous positioning the deposition print head 100 according to a predetermined pattern, the extrusion can be used for depositing the molten thermoplastic material, which when allowed to solidify, forms small portions i.e. layers on an object to be formed. By gradually forming these layers a complete object can be formed.

[0056] A space 109 between the susceptive element 103 and the sleeve 102 allows reduction of heat transfer from the susceptive element 103 to the sleeve 102. The induction coil 105 is made from windings of for example copper wire. In alternative embodiment, the coil 105 can be integrated in the sleeve.

[0057] FIG. 1b shows side view of the deposition print head 100 from FIG. 1.

[0058] FIG. 2a shows an outline of susceptive element 103. The susceptive element 103 comprises a body having a bobbin shape, comprising a tubular portion 201 and at the both ends of the tubular portion 201 comprising rims 202. The filament channel 104 has an inner diameter d1. The tubular portion 201 has an outer diameter d2 and the rims 202 have an outer diameter d3, such that d1<d2<d3.

[0059] The tubular portion 201 and rims 202 can be manufactured from an insulating temperature shock resistant material such as quartz glass or a ceramic material, having an inner layer of the ferromagnetic and/or low conductive material as described. Alternatively, the tubular portion 201 and rims 202 can be manufactured from the ferromagnetic and/or low conductive material as described

[0060] FIG. 2b shows the susceptive element 103 of FIG. 2a having the nozzle 106 attached to a lower end of the susceptive element 103. This prevents leakage of molten thermoplastic filament material into the sleeve 102.

[0061] FIG. 2c shows a spacing element 108 for spacing apart two susceptive elements 103 in the sleeve 102. The spacing element has an annular shape and can be manufactured from the same material as the sleeve 102. An inner diameter of the spacing element 108 matches the inner diameter d1 of the susceptive elements 103, whereas an outer diameter of the spacing element 108 matches the inner diameter d3 of the sleeve 102.

[0062] FIG. 2d shows a sleeve 102 having a tubular shape, and an inner diameter d3 for receiving at least one susceptive element 103. When multiple susceptive elements 103 are inserted in the sleeve 102, these susceptive elements can be separated and spaced apart by spacing elements 108 between the susceptive elements 103.

[0063] The sleeve 102 has an outer diameter d4>d3 providing sufficient wall thickness for thermal insulation of the susceptive element 103 to protect the surroundings of sleeve 102.

[0064] The sleeve 102 is made of a thermally insulating and heat shock resistant material. Preferably quartz glass is used. Possible alternatives include ceramic material.

[0065] FIG. 3a shows a deposition print head 100 having a multiple susceptive elements 103 separated by spacing elements 108. Susceptive elements 103, the spacing elements 108, sleeve 102, exciter 105 and nozzle 106 are centered around a common filament channel 104. The exciter 105 in FIG. 3a can be subdivided in portions, each portion corresponding with a susceptive element 103.

[0066] FIG. 3b shows the deposition print head 100 of FIG. 3a in a side view, and with driver circuits 302 connected to the respective portions 301 of the exciter 105 of the deposition print head 100. The portions 301 of exciter 105, when electrically separated, allow individual excitation of these portions. In the case of the exciter 105 being formed by an induction coil, each coil corresponding to a portion can be activated at a different energy level by means of a dedicated driver circuit 302. Such a driver circuit 302 can be an amplifier for amplifying an RF-signal. The amplified RF-signal is supplied to the portions 301 of the exciter 105 via electrical connection leads. The energy levels of the RF-signals supplied to the respective portions 301 of the exciter 105 are controllable by a control device (not shown), in accordance with a temperature profile.

[0067] RF-signals for exciting the ferromagnetic susceptive elements 103 can have a frequency in a wide range of hundreds of kilohertz to several Megahertz or tens of Megahertz, which frequency range depends on the material and layer thickness, and/or resistivity of the susceptive element material.

[0068] FIG. 4a shows a cross section of an alternative configuration for the deposition print head 100 having three susceptive elements 103. FIG. 4b shows a side view of the deposition print head 100 of FIG. 4a. The susceptive elements 103 are arranged in the common sleeve 102 and separated by spacing elements 108 as in the deposition print head of FIGS. 3a and 3b. From FIGS. 4a and also FIG. 4b it should be apparent that exciter 105 can be single coil wound around the common sleeve 102. The induction coil shows a varying density of windings around the sleeve 102 for each susceptive element 103. This allows a different energy level for each respective susceptive element 103 with a single exciter 105.

[0069] In the example of FIG. 4b, the lower portion 401 of the exciter 105 has the most windings for the corresponding susceptive element 103, and will therefore have the highest energy transfer level compared to the middle portion 402 and upper portion 403. It should be clear to the skilled person that the energy transfer level per portion 401, 402, 403 can also be the same for each portion 401, 402, 403. The energy transfer level is chosen to accommodate a temperature profile to be created in a longitudinal direction along the deposition print head 100.

[0070] FIG. 5 shows a deposition print head assembly having multiple print heads 100 mounted in a vessel 501. The vessel 501 allows coolant 504 to be introduced via inlet 502 and to be discharged via outlet 503. The coolant 504 includes water, oil, any other liquid. The coolant may also be a gas such as air. The coolant 504 allows the deposition print heads 100 to be operated during prolonged time periods. The vessel 501 can be mounted onto a platform which is connected to a positioning system of a deposition printer.

[0071] FIG. 6a shows a temperature profile of a deposition print head in feed direction 107, x in FIG. 6a, in accordance with one of the FIGS. 3a, 3b, 4a and 4b. FIG. 6a shows that while thermoplastic filament material passes through a first susceptive element 103, a filament temperature increases in stage I to a first level indicated. This can be a pre-heating stage. Continuing to a second susceptive element 103 in stage II, the filament temperature is allowed to increase further. Passing by the last susceptive element 103 in stage III, the filament temperature reaches a maximum level. This is preferably a temperature above a melt temperature T.sub.m of the thermoplastic filament material, allowing the filament material to be deposited by the nozzle 106 of the deposition print head 100.

[0072] By varying the excitation, i.e. energy transfer, from the exciter 105 to the different susceptive elements 103, the temperature level may vary indicated by the dotted line in FIG. 6a.

[0073] FIG. 6b shows a more advanced temperature profile of a deposition print head in feed direction 107, x in FIG. 6b. Three pre-heating stages are shown indicated by I, II and III, allowing the thermoplastic filament feeding through the filament channel 104 starting from temperature T0 to reach gel temperate Tg. Than in stage IV, the thermoplastic filament gel is heated to a temperature above the melt temperature Tm. This ensures that all of the thermoplastic filament material is molten when it reaches the last stage V where it is allowed to drop in temperature to the melt temperature Tm. Thus after stage V the thermoplastic filament material is homogenously molten before it exits the nozzle 106. The various temperatures can be achieved by controlling the energy transfer levels between the exciter portions and respective susceptive elements 103 in the filament path towards the nozzle output in the feed direction 107. A temperature drop can be realized by keeping the respective portion of the deposition print head at a predetermined temperature. Also a temperature drop can be realized by passing the filament through a spacing element which allows heat transfer from the filament channel 104 towards the sleeve 102.

[0074] FIG. 7a shows an arrangement of susceptive elements 103 having two spacing elements 108 interposed between the elements 103 and sensing elements 701. The sensing element comprises a temperature sensor 702. All elements are normally arranged in a sleeve 102, which is not shown in FIG. 6a.

[0075] The sensing elements 701 comprise an annular body 704 from for example the same material as the spacing elements 108 and have a filament channel 104 in communication with the filament channel 104 of the susceptive elements 103 and the spacing elements 108. The temperature sensor 702 is positioned in a cavity 703 such that the sensor is in close proximity to the filament channel 104. The temperature sensor 702 can be a resistive temperature device (RTD) such as for example a PT100 element.

[0076] The sensing elements 701 are suitable for measuring the filament temperatures T1 and T2 respectively.

[0077] FIG. 7b shows a cross section a sensing element 701 having a temperature sensor 702.

[0078] FIG. 8 shows a block diagram of a process for controlling a temperature, e.g. T1 of filament passing through the filament channel 104 of FIG. 7a in a deposition print head as described above.

[0079] A set temperature 801 is compared with a measured temperature 812 by temperature sensor 811 corresponding to sensor 702 in FIG. 7a. The difference temperature 803 is sent to a control unit 804 which converts the temperature difference in a control signal 805 which determines an energy level of an exciter 806. An energy transfer 807 from exciter 806 to susceptive element 808 corresponding to a susceptive element 103 of FIG. 7a causes the susceptive element 808 to heat up thermoplastic filament being fed through the filament channel of the susceptive element 808. Temperature sensor 811 corresponding to temperature sensor 702 of FIG. 7a, measure the temperature 810 (T1) of the filament which passed through the susceptive element.

[0080] The embodiments described above are intended as examples only, not limiting the scope of protection of the claims as set out below.

REFERENCE NUMERALS

[0081] 100 deposition print head [0082] 102 sleeve [0083] 103 susceptive element [0084] 104 filament channel [0085] 105 exciter [0086] 106 nozzle [0087] 107 feed direction [0088] 108 spacing element [0089] 109 space [0090] 201 body [0091] 202 rim [0092] 203 receiving space [0093] 301 additional heating element [0094] 302 driver [0095] 501 vessel [0096] 502 input [0097] 503 output [0098] 504 coolant [0099] 601 temperature profile [0100] 602 temperature profile [0101] 701 sensing element [0102] 702 temperature sensor [0103] 703 cavity [0104] 704 annular body [0105] 800 temperature control process [0106] 801 set temperature value [0107] 802 subtraction unit [0108] 803 temperature difference [0109] 804 control unit [0110] 805 excitation energy [0111] 806 exciter [0112] 807 heat transfer [0113] 808 susceptive element [0114] 809 hot filament feed [0115] 810 filament temperature [0116] 811 temperature sensor [0117] 812 measured temperature value