Patent Application
20160332378
This specification relates to components of three dimensional (3D) printers, such as Fused Filament Fabrication (FFF) 3D printers.
3D printers employ additive manufacturing techniques, where a product can be built by the addition of materials. Various types of additive manufacturing techniques can be employed, including granular techniques (e.g., Selective Laser Sintering (SLS) and Direct Metal Laser Sintering (DMLS)) and extrusion techniques (e.g., FFF). In addition, various types of 3D printer structures are employed for 3D printing. For example, FFF 3D printers include both Cartesian (xyz) type 3D printers and delta type 3D printers. In typical Cartesian (xyz) type 3D printers, a carriage for a hot end for an extruder, and/or a build platform, is connected with rails that extend in the three orthogonal dimensions of printing (x, y & z). In contrast, in typical delta type 3D printers, a carriage for a hot end for an extruder is connected by arms with three rails that extend in only the z direction, and the carriage is moved in three dimensions by independently adjusting the positions of end points of the arms along the three rails.
This specification describes systems and techniques relating to 3D delta printers, such as FFF 3D delta printers. In general, one or more aspects of the subject matter described in this specification can be embodied in a 3D delta printer that includes: a build platform; a 3D printer delta motion system; and a space frame configured and arranged to support the 3D printer delta motion system as the 3D printer delta motion system moves relative to the build platform; wherein the space frame includes multiple triangular units surrounding a build volume above the build platform.
The 3D printer delta motion system can include three drive units located in three respective sections of the space frame, and each of the three respective sections of the space frame can include three triangular facets forming angles with respect to the build platform that are greater than ninety degrees. The multiple triangular units of the space frame can form eight triangular facets. The multiple triangular units of the space frame can form fourteen triangular facets. Other numbers of facets are also possible. In addition, a top center facet of the triangular facets can be parallel with a plate on a top center position of the space frame over the build volume.
The multiple triangular units can include beams connected at nodes. The 3D delta printer can include a triangular plate on a top center position of the space frame over the build volume, and the triangular plate can have truncated corners and/or include perforations. The beams can include tubes. The nodes can include welded junctions for the beams. The nodes can include fastened junctions for the beams. The nodes can include 3D printed junctions for the beams. Moreover, the multiple triangular units can include metal bent to specific angles.
Particular embodiments of the subject matter described in this specification can be implemented to realize one or more of the following advantages. Using a space truss frame structure for a 3D delta printer can reduce both flex and resonance during 3D printing. Further, the frame geometry can be designed to reduce susceptibility to torsion, as well as to reduce or eliminate the use of long vertical structural members in which frame loading can occur mid-member, at the weakest point of the member. A space truss type frame can be used, where the structural stiffness is derived from triangular frame geometries. The systems and techniques described herein can result in reduced frame distortion, which can likewise result in fewer 3D print distortions. 3D printer performance can thus be improved, including facilitating the creation of more accurate 3D prints. Moreover, in some cases, equally accurate 3D prints can be realized at higher accelerations since acceleration of the carriage imparts force on the frame, and it can take greater force to distort the truss frame the same amount as a non-truss frame.
In addition, using a circular perimeter drive structure for a 3D printer motion system can increase control and stability, and thus reduce vibrations and distortions. A circular perimeter drive structure can be used with a Stewart platform, a 3D printer delta motion system, or both. In the context of a 3D delta printer, the use of a circular perimeter drive assembly to move the carriage can eliminate the need to use long lengths of unsupported belts or cables, which can thus increase accuracy and precision of the movement of the carriage by eliminating long lengths of unsupported belts or cables that tend to resonate (like strings on a musical instrument). This can result in fewer 3D print distortions, and 3D printer performance can thus be improved, including facilitating the creation of more accurate 3D prints and higher speed 3D prints. The circular perimeter drive puts the mass of the motor and any pulleys on the frame, off the sector, and lower mass on the sector translates into less force needed for acceleration and consequently less distortion on affected components in the system and less demand on motors (e.g., potentially can use smaller, less expensive motors to accelerate a smaller mass at a given rate).
The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the invention will become apparent from the description, the drawings, and the claims.
Like reference numbers and designations in the various drawings indicate like elements.
In addition, the 3D printer delta motion system 120 can include various types of mechanical drive systems (e.g., a circular perimeter drive motor 120a) for causing delta printing movement of a carriage (e.g., a carriage 120b), as well as various types of processor electronics (e.g., a control computer 120c) that have been designed and/or programmed to control the mechanical systems to cause the delta 3D printing. Further, the 3D printer delta motion system 120 can also include various sensors and other components.
In some implementations, the 3D printer delta motion system 120 includes at least one processor and medium encoding instructions 122 (e.g., a microprocessor with embedded firmware), one or more mechanical systems 124 (e.g., to physically move the carriage, the build platform, or both), and one or more sensor(s), amplifier(s), and actuator(s) 126. Thus, the 3D printer delta motion system 120 can be a mechatronic system, which monitors the build environment and/or the 3D printer using sensors, and processes the sensor information in order to change the behavior of the system so as to react to changes in the build environment and/or the 3D delta printer itself. In this case, the encoded instructions (e.g., software) has become an integral element of the 3D printer, allowing the 3D printer to identify and react to situational changes that can occur during 3D printing.
In some implementations, the 3D printer motion system 120 includes one or more portions of the extruder. For example, the system 120 can include the extrusion motor, filament drive mechanism, or both. In some implementations, the system 120 can include extruder drives that employ the systems and techniques described in U.S. Patent Application No. 62/287,352, titled “EXTRUDER DRIVE MECHANISM FOR THREE DIMENSIONAL (3D) PRINTER”, filed on Jan. 26, 2016, under Attorney Docket No. 15786-0262P01, which application is hereby incorporated by reference. Furthermore, in some implementations, the carriage can hold and transport a hot end that employs the systems and techniques described in U.S. Patent Application No. 62/217,606, titled “NARROW ANGLE HOT END FOR THREE DIMENSIONAL (3D) PRINTER”, filed on Sep. 11, 2015, under Attorney Docket No. 15786-0265P01, which application is hereby incorporated by reference.
Referring again to
Using such non-traditional structural frame geometries with a delta-type 3D printer can provide significant improvements for 3D printing. Using a triangle based space truss frame geometry means that straight structural members are joined to form a rigid structure with triangular units connected at nodes. This type of structure can reduce or minimize distortion in the 3D printer frame during 3D printing, such as torsion, flex, and resonance caused by the mechanical forces on the frame during printing. Note that the triangular units are not perfect triangles; the corners can be rounded or otherwise truncated, and the edges can be modified while still maintaining the generally triangular nature. In addition, the triangular units can have other modifications made thereto, including use of solid pieces (e.g., triangular plates) which can include one or more holes (e.g., perforations) and potentially additional components.
The bottom facet in this example is composed of the three base beams 132d, 134d, 136d, which are connected together at their ends. In the example shown, each beam of the space frame 130 is a tube that is inserted into tubular receiving members of a junction device. However, other types of beams can be used, including solid beams, I beams, or others. Also, various types of materials can be used to construct the beams, including plastic, metal, or composite materials.
In addition, rather than using beams to form the facets, in some implementations, one or more or all of the facets can be created from plates, rather than from beams that are connected together. Moreover, in some implementations, one or more or all of the facets can be made from connected beams that also have a triangular plate attached thereto. For example, in
As noted above, each of the respective regions of the space frame 130 has four triangular facets in this example. A drive unit 124a is supported directly by four beams 132b, 132c, 132e, 132f of the space frame. A first facet of the space frame 130 for the drive unit 124a is that formed by the base beam 132d and the two beams 132c, 132e. A second facet of the space frame 130 for the drive unit 124a is that formed by the three beams 132c, 132a, 132b. A third facet of the space frame 130 for the drive unit 124a is that formed by the three beams 132e, 132g, 132f. As shown, each of these first three triangular facets forms an angle with respect to the build platform that is greater than ninety degrees.
As noted above, variations in the design of the space truss frame for a delta-type 3D printer are also contemplated.
Rather than welding, other connection techniques can be used at the junctions or elbows of the space frame, such as bolts, screws, fasteners, friction, glue or other known mechanical couplings. Further, jigs can be used to hold parts at specific angles, with or without welding (e.g., as shown in
Furthermore, as noted above, circular perimeter drive structures and mechanisms can be used.
The portion 300 of the circular perimeter drive assembly includes an arc side 305 and a circle-center side 310. The portion 300 of the circular perimeter drive assembly is sector shaped in that the arc side 305 and the circle-center side 310 correspond to a sector 320. A sector is a plane figure bounded by two radii and the included arc of a circle. As will be appreciated, many variations are possible in the portion 300 of the circular perimeter drive while still retaining it sector shaped character. For example, the arc side 305 can extend beyond the sector 320 (as shown) rather than being coextensive with it (e.g., the arc side 305 can extend for one hundred and twenty degrees of arc while the sector 320 extends for only ninety degrees of arc). As another example, the sector shaped portion 300 of the circular perimeter drive assembly can be a single solid piece, or it can be constructed from separate parts that leave some of the sector 320 void of structural material. Further variations are also possible, including implementations in which the arc side extends for ninety degrees of arc or sixty degrees of arc.
In
In the example shown, the coupling is indirect in that the coupling between the drive gear 352 and the arc side of the sector shaped body 335 is made through a belt 350 that wraps around idlers 354a, 354b. The idlers 354a, 354b are attached to the frame, and the belt 350 is attached to the sector shaped body 335 at a first point 337a and at a second point 337b; note that the points 337a, 337b can be on the non-arc side (as shown) or the arc side of the body 335. The sector shaped body 335 is also attached to a rigid body (e.g., an arm) 356 at a first universal joint 358a, and this rigid body 356 is attached to a carriage 360 of a 3D printer at a second universal joint 358b. Thus, the movement of the sector shaped body 335 about the pivot 345 causes the carriage 360 to move. Moreover, as shown in the previous figures, when the circular perimeter drive assembly includes three such structures in a 3D delta printer, movement of the carriage 360 in three dimensions is readily controllable by the independent movement of the three respective sector shaped bodies about their respective pivots on the frame.
As will be appreciated, various different structures and configurations can be used to engage each motor with its associated sector shaped body. In some implementations, a chain 350 is used rather than a belt 350. Various numbers of gears, chains, teeth, etc. can be employed.
Regardless of such modifications in the mechanical structures, 3D printer delta motion systems in accordance with the present disclosure include hardware, firmware and/or software that moves the sector shaped bodies to cause the printer carriage to move as desired in 3D space within the build volume.
With the coordinate system shown in
E
0
=[x
0
, y
0
, z
0]
E
0
′=[x
0, 0, z0]
E
1
′=[x
0
+r
e, 0, z0]
r
r
′=√{square root over (rr2−x02)}
Two circles are defined by:
(x−x1)2+(z−z1)2=rr′2
(x−x3)2+(z−z3)2=rb2
A shift is made so the origin is at the shoulder pivot point of the frame:
(x−x0′)2+(z−z0)2=rr′2
x
0
′=x
0
+r
e
−r
f
x
2
+z
2
=r
s
2
And a generic formula for points of intersection between two circles is as follows:
Plugging in the circles, am=0, bm=0, rm=rs, an=x0′, bn=z0, and rn=rr′, results in:
Forward kinematics of a 3D printer delta motion system can implemented in accordance with the following equations, beginning with the equations for three circles:
(x−x1)2+(y−y1)2+(z−z1)2=re2 (1)
(x−x2)2+(y−y2)2+(z−z2)2=re2 (2)
(x−x3)2+(y−y1)2+(z−z3)2=re2 (3)
Multiplying out (noting that y1=0) results in:
x
2
+y
2
+z
2−2x1x−2z1z=re2−x12−z12 (4)
x
2
+y
2
+z
2−2x2x−2y2y−2z2z=re2−x22−y22−z22 (5)
x
2
+y
2
+z
2−2x3x−2y3y−2z3z=re2−x32−y32−z32 (6)
Subtracting the equations from each other results in:
(x2−x1)x+y2y+(z2−z1)z=(w2−w1)/2 (7)
(x3−x1)x+y3y+(z3−z1)z=(w3−w1)/2 (8)
(x2−x3)x+(y2−y3)y+(z2−z3)z=(w2−w3)/2 (9)
where:
w
1
=x
1
2
+y
1
2
+z
1
2 (10)
w
2
=x
2
2
+y
2
2
+z
2
2 (11)
w
3
=x
3
2
+y
3
2
+z
3
2 (12)
Subtracting and rearranging to solve for y gives:
Substituting and solving for x in terms of z gives:
Substituting and solving for y in terms of z gives:
Substituting back into the original equation for the circle results in:
(a1z+(b1−x1))2+(a2z+(b2−y1))2+(z−z1)2=r22
a
1
2
z
2+2a1(b1−x1)z+(b1−x1)2+a22z2+2a2(b2−y1)z+(b2−y1)2+z2−2z1z+z12=re2 (26)
(a12+a22+1)z2+2(a1(b1−x1)+a2(b2−y1)−z1)z+((b1−x1)2+(b2−y1)2+z12−re2)=0 (27)
Finally, solving for z can be done with the quadratic equation:
Note that solving for x and y is trivial with known z using equations 16 and 22.
In addition, although this disclosure focuses on 3D printing and the use of a circular perimeter drive assembly for delta-style, 3-axis movement, the circular perimeter drive systems and techniques described can also be used for Stewart platform, 6-axis movement (also referred to as hexapod machine movement), either in the context of a 3D printer or in other applications, e.g., subtractive machining operations, pick-and-place robotic applications, etc.
In
While this specification contains many implementation details, these should not be construed as limitations on the scope of the invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments of the invention. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.
Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments.
Thus, particular embodiments of the invention have been described. Other embodiments are within the scope of the following claims. In addition, the actions recited in the claims can be performed in a different order and still achieve desirable results.
This application claims the benefit under 35 U.S.C. §119(e) of U.S. Patent Application No. 62/288,246, entitled “THREE DIMENSIONAL (3D) DELTA PRINTER FRAME STRUCTURE”, filed Jan. 28, 2016; this application is related to U.S. Patent Application No. 62/288,262, titled “THREE DIMENSIONAL (3D) PINTER MOTION SYSTEM”, filed on Jan. 28, 2016, under Attorney Docket No. 15786-0257P01; and both of these prior applications are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62288246 | Jan 2016 | US |
