Apparatus, methods, and systems for calibrating 3D printers
Aspects of apparatus, methods, and systems for calibrating 3D printers are described. One aspect is an apparatus that may comprise: a nozzle support structure that operatively attaches a nozzle to a 3D printer and comprises a strained region that experiences a surface strain of between approximately 1×10-7 and approximately 1×10-4 responsive to a contact between the nozzle and a print surface; and a semiconductor strain gauge that is attached to the strained region and operable to generate an analog signal and output a digital signal responsive to the surface strain, the semiconductor strain gauge comprising a gauge factor of between approximately 80 and approximately 200, the digital signal being detectable by the 3D printer. Related apparatus, methods, and systems also are described.
1 . An apparatus comprising:
a nozzle support structure that operatively attaches a nozzle to a 3D printer and comprises a strained region that experiences a surface strain of between approximately 1×10 −7 and approximately 1×10 −4 responsive to a contact between the nozzle and a print surface; and
a semiconductor strain gauge that is attached to the strained region and operable to generate an analog signal and output a digital signal responsive to the surface strain, the semiconductor strain gauge comprising a gauge factor of between approximately 80 and approximately 200, the digital signal being detectable by the 3D printer,
the nozzle support structure comprising:
a nozzle block extending outwardly from an extruder body for attachment to the nozzle and a heat block;
a hinge connector arm extending outwardly from the extruder body; and
a flexure bearing hinge that extends between the nozzle block and the hinge connector arm and flexes when a tip of the nozzle contacts the print surface,
wherein a flexure of the flexure bearing hinge causes the strained region to experience the surface strain.
2 . The apparatus of claim 1 , wherein the nozzle support structure extends outwardly from an extruder body operable to output a molten flow of 3D printable material.
3 . The apparatus of claim 2 , wherein the nozzle support structure comprises metallic structures that are formed integral with the extruder body.
4 . The apparatus of claim 1 , wherein:
a flexible portion of the nozzle support structure flexes when a tip of the nozzle contacts the print surface; and
a flexure of the flexible portion causes the strained region to experience the surface strain.
5 . The apparatus of claim 1 , wherein the nozzle block, the hinge connector arm, and the flexure bearing hinge are made of the same material and the flexure bearing hinge consists of a living hinge connecting the nozzle block and the hinge connector arm.
6 . The apparatus of claim 1 , wherein the nozzle block comprises:
a long leg extending outwardly from the extruder block;
a short leg connected to the flexure bearing hinge;
a bottom leg connecting the long leg and the short leg; and
an interior space defined by interior surfaces of the extruder block, the long leg, the bottom leg, and the short leg.
7 . The apparatus of claim 6 , wherein:
the heat block is attached to the bottom leg and the nozzle; and
the apparatus comprises:
a delivery tube extending from the extruder body, through the interior space, through the bottom leg, and through the heat block for connection to the nozzle; and
a heat sink surrounding a portion of the delivery tube in the interior space.
8 . The apparatus of claim 6 , comprising a hinge connector arm base extending outwardly from the extruder body to support the hinge connector arm, wherein a rigidity of the hinge connector arm base is greater than a rigidity of the hinge connector arm.
9 . The apparatus of claim 8 , wherein a bottom surface of the hinge connector arm base and a top surface of the short leg are spaced apart define a flexure gap that permits the top surface to move toward the bottom surface when the flexure bearing hinge flexes.
10 . The apparatus of claim 9 , wherein the strained portion comprises an outside surface of the hinge connector arm and the semiconductor strain gauge is located on the outside surface.
11 . The apparatus of claim 1 , wherein the strained portion comprises an outside surface of the nozzle support structure that experiences the surface strain when a flexible portion of the nozzle support structure flexes responsive to the contact.
12 . The apparatus of claim 1 , wherein the semiconductor strain gauge comprises one or more of:
a Wheatstone bridge operable to output the analog signal responsive to the contact;
an R-C high-pass filter operable to remove a temperature drift portion of the analog signal;
an instrumentation amplifier operable to increase a resistance to power supply noise of the analog signal;
an AC-Coupled amplifier operable to perform an AC-Coupled amplifier stage on the analog signal;
a peak-hold circuit operable to extend a duration of short pulses of the analog signal; and
a Schmitt trigger operable to convert the analog signal into the digital signal after passing through one or more of the R-C high-pass filter, the instrumentation amplifier, the AC-Coupled amplifier, and the peak-hold circuit.
13 . The apparatus of claim 12 , wherein each leg of the Wheatstone bridge experiences equal voltage variations of opposite polarity.
14 . The apparatus of claim 1 , wherein the semiconductor strain gauge is operable to generate the analog signal and output the digital signal by:
outputting, with a Wheatstone bridge and the semiconductor strain gauge, the analog signal responsive to the contact;
removing, with an R-C high-pass filter, a temperature drift portion of the analog signal during a filter stage comprising a corner frequency of between approximately 1 Hz and approximately 100 Hz;
increasing, with an instrumentation amplifier, a resistance to power supply noise of the analog signal during an amplifier stage comprising a gain of approximately 50 to approximately 1000;
performing, with an AC-Coupled amplifier, an AC-Coupled amplifier stage on the analog signal comprising a gain of approximately 50 to approximately 1000;
converting, with a Schmitt trigger, the analog signal into the digital signal.
15 . The apparatus of claim 14 , wherein each leg of the Wheatstone bridge experiences equal voltage variations of opposite polarity.
16 . The apparatus of claim 1 , wherein the semiconductor strain gauge comprises one or more of:
a voltage divider operable to output the analog signal responsive to the contact;
an R-C high-pass filter operable to remove a temperature drift portion of the analog signal;
an AC-Coupled amplifier operable to perform an AC-Coupled amplifier stage on the analog signal;
a peak-hold circuit operable to extend a duration of short pulses of the analog signal; and
a Schmitt trigger operable to convert the analog signal into the digital signal after passing through one or more of the R-C high-pass filter, the AC-Coupled amplifier, and the peak-hold circuit.
17 . The apparatus of claim 1 , wherein the semiconductor strain gauge is operable to generate the analog signal and output the digital signal by:
outputting, with a voltage divider and the semiconductor strain gauge, the analog signal responsive to the contact;
removing, with an R-C high-pass filter, a temperature drift portion of the analog signal with a filter stage comprising a corner frequency of between approximately 1 Hz and approximately 100 Hz;
performing, with an AC-Coupled amplifier, one or more AC-Coupled amplifier stages on the analog signal comprising a gain of approximately 50 to approximately 1,000,000; and
converting, with a Schmitt trigger, the analog signal into the digital signal.
18 . The apparatus of claim 1 , comprising the nozzle, the 3D printer, and the print surface, wherein the strained portion comprises an outside surface of the nozzle support structure that experiences the surface strain when a hinge of the nozzle support structure flexes responsive to the contact.
19 . The apparatus of claim 18 , wherein the 3D printer is operable with the semiconductor strain gauge to calibrate a Z-offset between the print surface and the nozzle by:
moving, with a processor of the 3D printer, the nozzle to a plurality of different locations on the print surface;
at each location plurality of different locations:
causing, with the processor, one contact between the nozzle and the print surface that causes the strained region to experience the surface strain;
generating, with the semiconductor strain gauge, the analog signal responsive to the surface strain; and
converting, with the semiconductor strain gauge, the analog signal into the digital signal;
outputting, with the semiconductor strain gauge, the digital signal to the 3D printer; and
determining, with the processor of the 3D printer, the Z-offset based on the digital signal.
20 . An apparatus comprising:
an extruder body;
a heat block;
a nozzle support structure that operatively attaches a nozzle to a 3D printer and comprises a strained region that experiences a surface strain of between approximately 1×10 −7 and approximately 1×10 −4 responsive to a contact between the nozzle and a print surface; and
a semiconductor strain gauge that is attached to the strained region and operable to generate an analog signal and output a digital signal responsive to the surface strain, the semiconductor strain gauge comprising a gauge factor of between approximately 80 and approximately 200, the digital signal being detectable by the 3D printer, the nozzle support structure comprising:
a nozzle block extending outwardly from the extruder body for attachment to the nozzle and the heat block;
a hinge connector arm extending outwardly from the extruder body; and
a flexure bearing hinge that extends between the nozzle block and the hinge connector arm and flexes when a tip of the nozzle contacts the print surface,
wherein a flexure of the flexure bearing hinge causes the strained region to experience the surface strain.