FI128627B

FI128627B - Stereolithography apparatus equipped with resin collecting mechanism and method of operating said apparatus

Info

Publication number: FI128627B
Application number: FI20185584A
Authority: FI
Inventors: Jukka Kanerva; Tero Rakkolainen
Original assignee: Planmeca Oy
Priority date: 2018-06-28
Filing date: 2018-06-28
Publication date: 2020-09-15
Also published as: FI20185584A1; WO2020002776A1

Abstract

Stereolithography apparatus, comprising a vat (401) for holding resin during stereolithographic 3D printing, a resin delivery mechanism (701) comprising a piston (601) and at least one resin tank, wherein the resin tank is a resin capsule (501) having one single shot of resin (703), and the resin delivery mechanism is arranged to drain the resin from the vat (401) back inside the resin capsule (501) by the movement of the piston (601).

Description

STEREOLITHOGRAPHY APPARATUS EQUIPPED WITH RESIN COL- LECTING MECHANISM AND METHOD OF OPERATING SAID APPA- RATUS

FIELD OF THE INVENTION The invention concerns the technology of ste- reolithographic 3D printing, also known as stereolith- ographic additive manufacturing. In particular the in- vention concerns the task of collecting extra resin back to resin tank.

BACKGROUND OF THE INVENTION Stereolithography is a 3D printing or addi- tive manufacturing technique in which optical radia- tion is used to photopolymerize suitable raw material to produce the desired object. The raw material comes to the process in the form of a resin. A vat is used to hold an amount of resin, and a build platform is moved in the vertical direction so that the object to be produced grows layer by layer, beginning on a build surface of the build platform. The optical radiation used for photopolymerizing may come from above the vat, in which case the build platform moves downwards through the remaining resin as the manufacturing pro- ceeds. The present description concerns in particular N the so-called "bottom up” variant of stereolithogra- N phy, in which the photopolymerizing optical radiation = comes from below the vat and the build platform moves N 30 upwards away from the remaining resin as the manufac- = turing proceeds. 3 The resin is held in a container and the user 3 estimates the amount of resin to dispense from the o container to the vat. The container may be portable N 35 (e.g. bottle) and the user pours the resin to the vat. However, it is difficult to estimate the amount ofresin that is poured and the user easily pours too much resin and the additional resin is lost. As the resins are relatively expensive, care should be taken to not allow too much resin to enter the vat and to utilize as much of the remaining resin as possible for actual manufacturing jobs. If the user pours too lit- tle resin, the desired object will be incomplete or the printing process is interrupted. Pouring may also be messy and the resin may even be spilled out of the vat.

The resin container may also be large fixed tank from which the resin is conducted to the vat by a separate channel. Different resins are needed for man- ufacturing different kinds of objects and large resin tanks are unconventional because one resin material is very difficult to replace with another resin material. The whole resin tank and the resin channel must be cleaned carefully before starting a new process with the new resin material. If some previous resin materi- al is left inside the tank or channel, it could lead to undesired result.

Prior art publications relating to aspects presented in this disclosure include US2002195748A1, US2007075461A1, US2018043612A1, US2018141267A1 and Wo2016063996A1.

OBJECTIVE OF THE INVENTION S An objective of the invention is to enable a O convenient and economical handling of resins for ste- 7 30 reolithographic 3D printing.

N

I a SUMMARY > The invention is aimed to present a stereo- 3 lithography apparatus and a method of operating a ste- > 35 reolithography apparatus enabling economical handling of resins for stereolithographic 3D printing.

These and other advantageous aims are achieved by equipping the stereolithography apparatus with a resin delivery mechanism comprising means to pump the resin out of the resin tank and drain the resin back inside the resin capsule.

According to a first aspect, a stereolithog- raphy apparatus comprises a vat for holding resin dur- ing stereolithographic 3D printing, a resin delivery mechanism comprising a piston, and at least one resin tank. The resin tank is a resin capsule having one single shot of resin, and the resin delivery mechanism is arranged to drain the resin from the vat back in- side the resin capsule by the movement of the piston.

In an embodiment of the stereolithography ap- paratus, the piston is sealed against inner wall of the resin tank.

In an embodiment of the stereolithography ap- paratus, the piston is arranged to move reciprocating manner inside the resin tank.

In an embodiment of the stereolithography ap- paratus, the piston is arranged to be pulled back, whereby a vacuum is formed inside the resin capsule and resin is drained back inside the resin capsule.

In an embodiment of the stereolithography ap- paratus, the resin capsule is located above the vat.

In an embodiment of the stereolithography ap- paratus, the resin capsule comprises an outlet ar- N ranged in proximity of the vat.

N In an embodiment of the stereolithography ap- 3 30 paratus, the vat has an inclined position whereby the N vat is inclined towards the resin capsule.

= According to a second aspect, a method of op- 3 erating a stereolithography apparatus according to any LO of the preceding claims, comprising steps of pumping © 35 resin from the resin capsule into the vat, manufactur- N ing the object, and draining extra resin back inside the resin capsule.

In an embodiment of the method of operating a stereolithography apparatus, the resin is pumped from the resin capsule and drained back inside the resin capsule by the movement of a piston.

In an embodiment of the method of operating a stereolithography apparatus, the resin is drained by forming a vacuum inside the resin capsule by pulling the piston back up.

In an embodiment of the method of operating a stereolithography apparatus, the method further com- prises a step of inclining the vat towards the resin capsule.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illus- trate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings: Figure 1 illustrates a stereolithography ap- paratus in a front view with its lid closed, Figure 2 illustrates a stereolithography ap- paratus in a side view with its lid closed, Figure 3 illustrates a stereolithography ap- paratus in a front view with its lid open, o Figure 4 illustrates a stereolithography ap- O paratus in a side view with its lid open, O Figure 5 illustrates a stereolithography ap- K 30 paratus, N Figure 6 illustrates a stereolithography ap- E paratus in a front view, 3 Figure 7 illustrates a resin delivery mecha- 2 nism, = 35 Figure 8 illustrates a stereolithography ap- N paratus without a resin tank, and

Figure 9 illustrates a stereolithography ap- paratus with the resin tank in a front view.

DETAILED DESCRIPTION 5 Figs. 1 to 4 illustrate an example of a ste- reolithography apparatus. The apparatus could also be called a stereolithographic 3D printer, or a stereo- lithographic additive manufacturing apparatus. Basic parts of the apparatus are a base part 101 and a lid 102, of which the lid 102 is movably coupled to the base part 101 so that it can move between a closed po- sition shown in figs. 1 and 2 and an open position shown in figs. 3 and 4. Here the direction of the movement is vertical, but this is not a reguirement; the movement of the lid 102 in relation to the base part 101 could take place in other directions. An im- portant advantage of a movable lid of this kind is that an ongoing stereolithographic 3D printing process can be protected from any interfering external optical radiation by closing the lid 102.

A vat 401 is provided in the base part 101 for holding resin for use in the stereolithographic 3D printing process. A build platform 402 with a build surface 403 is supported above the vat 401 so that the build surface 403 faces the vat 401. This arrangement is typical to the so-called "bottom up” variant of o stereolithography, in which the photopolymerizing ra- O diation comes from below the vat. The bottom of the LÖ vat 401 is or can be selectively made transparent or 7 30 translucent for the kind of radiation used for said N photopolymerizing. E A moving mechanism is provided and configured 3 to move the build platform 402 in a working movement 2 range between first and second extreme positions. Of = 35 these, the first extreme position is the one proximal N to the vat 401, and the second extreme position is the one distant from the vat 401. In the first extreme po-

sition the build surface 403 is very close to the bot- tom of the wvat 401. The first layer of the object to be manufactured will be photopolymerized onto the build surface 403 when the build platform 402 is in the first extreme position. Consequently, in said first extreme position the distance between the build surface 403 and the bottom of the vat 401 is in the order of the thickness of one layer in the stereolith- ographic 3D printing process.

The position shown in figs. 3 and 4 may be the second extreme position, or at least closer to the second extreme position than to the first extreme po- sition. A working region of the stereolithography ap- paratus may be said to exist between the vat 401 and the second extreme position of the build platform 402, because the object to be manufactured will appear within this region. The build platform 402 does not need to move up to or even close to the second extreme position during the manufacturing of an object; the second extreme position may be most useful for making it easier to detach a manufactured object from the build platform 402 once the object is complete.

In the embodiment of figs. 1 to 4 the moving mechanism for moving the build platform 402 is inside the base part 101, and only represented by the two slits 301 seen in a vertical surface of the base part 101, as well as the horizontal support 404 of the N build platform 402. There is also a similarly hidden N moving mechanism for moving the lid 102 with respect 3 30 to the base part 101. This second moving mechanism may N comprise parts inside the base part 101 and/or parts = inside the 1id 102. Enclosing essentially all moving 3 mechanisms within the casings of the base part 101 x and/or the lid 102 involves the advantage of added o 35 safety, because it makes it improbable that a user N could get injured by any moving parts of such mecha- nisms.

The horizontal support 404 of the build plat- form 402 is shown only schematically in the drawings. In a practical implementation a support of the build platform 402 may comprise various advanced technical features, like joints and/or fine tuning mechanisms for ensuring that the orientation of the build surface 403 is appropriate. However, such features are out of the scope of this description and are therefore omit- ted here.

Another feature of the exemplary stereo- lithography apparatus of figs. 1 to 4 is a user inter- face, which comprises a touch-sensitive display 103 in the lid 102. The user interface may comprise various functions for implementing interactions between the apparatus and its user, including but not being lim- ited to buttons for controlling the movements of the lid 102 and the build platform 402. A touch-sensitive display is an advantageous feature of a user interface in particular if the stereolithography apparatus is to be used in environments where thorough cleaning and disinfecting are regularly required, like at medical and/or dental clinics. Placing a touch-sensitive dis- play 103 and/or other parts of the user interface in a front part of the lid 102 is advantageous, because it makes such parts of the user interface easily accessi- ble to the user. As such, at least some parts of the user interface could be implemented in the base part N 101. The touch-sensitive display 103 may be used for N receiving information of the object design and the 3 30 resin. It may be also used for inputting needed param- N eters (e.g. properties of the resin) for the printing = process. 3 The resin that is to be used in the stereo- LO lithographic 3D printing process may be brought to the © 35 stereolithography apparatus in a resin tank. The des- N ignation "resin tank” is used in this text as a gen- eral descriptor of any kinds of containers that mayhold resin in readiness for the resin to be used in a stereolithographic 3D printing process.

Fig. 5 illus- trates an example of a stereolithography apparatus having the lid 102 in the open position.

The resin tank is provided in form of a resin capsule 501, which contains one single shot of resin that is needed for a single stereolithographic 3D printing process.

The needed amount of resin depends on the object to be printed and, therefore, the size of the resin capsule 501 may vary.

The needed amount of resin may be calcu- lated by the user or the stereolithography apparatus may have means to calculate the amount based on the object design.

After calculating the needed amount of resin, the stereolithography apparatus may suggest the resin capsule to be used.

The resin capsule 501 is lo- cated above the vat 401 so that the resin may be emp- tied from the resin capsule 501 straight into the vat 401, which prevents unnecessary spillage.

According to one embodiment, the vat 401 com- prises a channel that is arranged to receive the resin from the resin capsule.

In fig. 5, the channel 502 is located below the resin capsule 501 in the corner of the vat 401. The channel may be a groove or a tube which conducts the resin further into the vat 401. The vat 401 may comprises several channels so that one is located below each resin capsule.

The stereolithography apparatus may comprise N a holder for removably receiving a resin capsule to an N operating position in the stereolithography apparatus. 3 30 An example of such a holder is illustrated in fig. 6 N and 8 with the reference designator 602. Providing a = holder for removably receiving a resin capsule in- 3 volves the advantage that the user may easily exchange 3 resin capsules to ensure the use of the most optimal o 35 resin for each stereolithographic 3D printing jok.

Q A resin capsule that can be removably re- ceived in the holder 602 may have the form of an elon-

gated capsule, as in figures, preferably with a cover or plug covering an opening in one end, and with an outlet 704 appearing in the other end. The outlet 704 may be equipped with a valve, seal, plug, or some oth- er means that keep the resin from escaping the resin capsule unless explicitly desired. Such an elongated resin capsule can be removably received in the holder 602 so that the end with the opening is upwards, and the outlet 704 is in or close to the vat 401.

In the example embodiment of fig. 6 and 8 a piston 601 is attached to the same support 404 as the build platform 402. When the build platform 402 moves downwards in order to assume the first extreme posi- tion, which is the starting position for producing a new object, the piston 601 moves downwards in concert with the build platform 402. This movement of the pis- ton 601 pumps the resin out of the resin capsule that was received in the holder 602, so that the resin flows out of the outlet 704 and into the vat 401. The cover or plug that covered the opening in the upper end of the resin capsule must naturally have been re- moved before that, as well as the means that closed the outlet 704 unless some mechanism is provided that automatically opens the outlet when needed.

It must be noted that making the piston 601 move in concert with the build platform 40? is only an example implementation. It involves the advantage that N only one moving mechanism is needed to move two parts. N However, in some applications it may be desirable to 3 30 be able to control the delivery of resin to the vat N 401 independently of the movement of the build plat- = form 402. For such applications an embodiment can be 3 presented in which there are separate mechanisms for x moving the build platform 402 and for delivering resin o 35 from a resin capsule into the vat 401. Such a separate Q mechanism may involve for example a piston that isotherwise like the piston 601 in fig. 6 but supported and moved by a moving mechanism of its own. Figures comprise only examples of the piston design. It is understood that the piston may have dif- ferent shapes and structures as far as it works in its purpose and is suitable to pump the resin out of the resin capsule 501. Only one holder 602 for one resin capsule is shown in the drawings, but the stereolithography appa- ratus may comprise two or more holders, and/or a sin- gle holder may be configured to receive two or more resin capsules. In particular if there are separate mechanisms for pumping resin from different resin cap- sules to the vat 401, the provision of places for re- ceiving multiple resin capsules involves the advantage that different resins can be used automatically, even during the manufacturing of a single object. Such a feature may be useful for example if the object to be manufactured should exhibit a sliding change of color.

The stereolithography apparatus might comprise two resin capsules of differently pigmented resin, and these could be delivered to the vat in selected pro- portions so that the resulting mix of resins in the vat would change its color accordingly.

According to one embodiment, the holder 602 comprises adjustable clasps 702 that may be adjusted to receive resin capsules with different sizes and N shapes.

N Fig. 7 illustrates a resin delivery mechanism 3 30 701 comprising a resin capsule 501 having some resin N 703 inside. The resin capsule is held by the adjusta- = ble clasps 702 that retain the resin capsule from its 3 sides. The resin delivery mechanism comprises also a x piston 601 arranged to move up and down. The downwards o 35 movement pumps the resin 703 out of the resin capsule so that the resin flows out of the outlet 704 and to the vat 401.

According to an embodiment, the resin capsule 501 is disposable so that after single use, the resin capsule is replaced by a new one.

As the resin is relatively expensive, it is not economical to waste the resin that is left over after the printing process.

Therefore, according to one embodiment, the upwards movement causes a vacuum inside the resin capsule 501 and the resin from the vat 401 may be drained back into the resin capsule 501 and used again later.

The vacuum is achieved by seal- ing the piston air tightly against the inner wall of the resin capsule.

As the piston is pulled back up, a vacuum is formed inside the resin capsule between the piston 601 and the outlet 704. The resin capsule is located so that the outlet is at the proximity of the vat and it is able to reach the resin on the vat.

Af- ter the printing process, the extra resin is drained back inside the resin capsule for later use.

According to an embodiment, the vat 401 may be inclined towards the resin capsule.

In this in- clined position, the extra resin is flown towards the outlet of the resin capsule and the extra resin may be collected more efficiently.

Fig. 9 illustrates schematically a case in which a resin capsule 501 has been received in the holder 702. The resin capsule 501 may comprise an identifier (e.g. graphical or electronical) having in- N formation regarding the resin, contained in that par- N ticular resin capsule 501, or the resin capsule 501 3 30 itself.

Said information may contain for example one N or more of the following: an identifier of resin con- = tained in the resin capsule 501, an indicator of 3 amount of resin contained in the resin capsule, a man- x ufacturing date of resin contained in the resin cap- o 35 sule 501, a best before date of resin contained in the N resin capsule, unique identifier of the resin capsule 501, a digital signature of a provider of resin con-

tained in the resin capsule 501. Said information may be used for controlling the stereolithography appa- ratus. For example the identifier may contain infor- mation of the size of the resin capsule 501 and said information is used to define the movement of the pis- ton 601 when pumping the resin out of the resin cap- sule 501 or when draining the left over resin back in- side the resin capsule 501. It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above, instead they may vary within the scope of the claims.

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Claims

1. Stereolithography apparatus, comprising: - a vat (401) for holding resin during stereolitho- graphic 3D printing, - a holder for removably receiving a resin tank, - a resin delivery mechanism (701) comprising a piston (601) and at least one resin tank, wherein - the resin tank is a resin capsule (501) having one single shot of resin (703), and - the resin delivery mechanism is arranged to drain the resin from the vat (401) back inside the resin capsule (501) by the movement of the piston (601).

2. A stereolithography apparatus according to claim 1, wherein the piston (601) is sealed against inner wall of the resin tank (501).

3. A stereolithography apparatus according to claim 1 or 2, wherein the piston (601) is arranged to move reciprocating manner inside the resin tank (501).

4. A stereolithography apparatus according to any of the preceding claims, wherein the piston (601) is arranged to be pulled back, whereby a vacuum is formed inside the resin capsule (501) and resin (703) is drained back inside the resin capsule (501).

5. A stereolithography apparatus according to S 25 any of the preceding claims, the resin capsule (501) N is located above the vat (401). 3 K

6. A stereolithography apparatus according to N any of preceding claims, wherein the resin capsule z (501) comprises an outlet (704) arranged in proximity x 30 of the vat (401).

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7. A stereolithography apparatus according to any of the preceding claims, wherein the vat (401) hasan inclined position, wherein the vat is inclined to- wards the resin capsule (501).

8. A method of operating a stereolithography apparatus according to any of the preceding claims, comprising steps of: - using the resin delivery mechanism (701) for pumping resin from the resin capsule (501) into the vat (401), - manufacturing the object, - using the resin delivery mechanism (701) for drain- ing extra resin (703) back inside the resin capsule (501).

9. A method of operating a stereolithography apparatus according to claim 8, wherein the resin is pumped from the resin capsule (501) and drained back inside the resin capsule (501) by the movement of a piston (601).

10. A method of operating a stereolithography apparatus according to claim 9, wherein the resin is drained by forming a vacuum inside the resin capsule (501) by pulling the piston (601) back up.

11. A method of operating a stereolithography apparatus according to any of claims 8-10, comprising a step of inclining the vat (401) towards the resin capsule (501).

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