Object generation temperature measurement

Patent metadata

Field	Value
Publication number	US-10539474-B2
Application number	US-201515562786-A
Country	US
Kind code	B2
Filing date	Jul 21, 2015
Priority date	Jul 21, 2015
Publication date	Jan 21, 2020
Grant date	Jan 21, 2020

Abstract

In some examples, a method comprises sensing a temperature of a plurality of sub-regions of a portion of a layer of build material in an object generation apparatus. A frequency distribution of sub-region temperatures may be derived therefrom and it may be determined whether the frequency distribution is bimodal. If the frequency distribution is not bimodal, a build material temperature zone is identified. If however the frequency distribution is bimodal, a fusing build material temperature zone and a non-fusing build material temperature zone are identified. The method may further comprise determining a nominal temperature of the at least one identified temperature zone.

First claim

The invention claimed is:

1. A method comprising:
sensing the temperature of a plurality of sub-regions of a portion of a layer of build material in an object generation apparatus;
deriving a frequency distribution of sub-region temperatures;
determining if the frequency distribution is bimodal;
identifying, when the frequency distribution is not bimodal, a build material temperature zone;
identifying, when the frequency distribution is bimodal, a fusing build material temperature zone and a non-fusing build material temperature zone;
the method further comprising determining a nominal temperature of the at least one identified temperature zone.

2. A method according to claim 1 in which determining if the frequency distribution is bimodal comprises identifying the temperatures having the two highest frequencies within the frequency distribution as a first and second temperature, and, if the first and second temperatures are separated by at least a separation coefficient, determining that the frequency distribution is bimodal.

3. A method according to claim 1 comprising:
when the frequency distribution is not bimodal, determining whether the nominal temperature of the build material temperature zone is indicative of fusing build material or non-fusing build material.

4. A method according to claim 3 in which determining whether the nominal temperature of the temperature zone is indicative of fusing build material or non-fusing build material comprises sensing the temperature over the layer of build material and:
if the layer of build material has two distinct temperature zones, determining that the layer of build material comprises a non-fusing build material temperature zone and a fusing build material temperature zone, determining a nominal temperature of the temperature zones, and determining if the nominal temperature of a temperature zone of the portion of build material matches the nominal temperature of the fusing build material temperature zone or the nominal temperature of non-fusing build material temperature zone; or
if the layer of build material has one distinct temperature zone, thereby determining that the portion of the layer of build material comprises non-fusing build material.

5. A method according to claim 1 in which deriving the frequency distribution comprises assigning a sub-region to a bin indicative of a range of temperatures.

6. A method according to claim 1 in which the nominal temperature is a central temperature in a temperature bin having a highest or second highest number of sub-regions therein.

7. A method according to claim 1 in which the nominal temperature is a mean of temperatures of the frequency distribution.

8. A method according to claim 1 , further comprising determining a nominal temperature of multiple temperature zones.

9. An object generation apparatus comprising:
a print bed to support a build material;
a temperature control apparatus to control the temperature of at least a portion of build material arranged on the print bed;
an energy source to cause selective fusing of the build material;
a temperature sensor, to determine temperatures for pixels representing sub-regions of at least a portion of a layer of build material arranged on the print bed; and
a processor to:
derive a frequency distribution of pixel temperatures;
determine if the frequency distribution is bimodal;
identify, when the frequency distribution is not bimodal, a build material temperature zone;
identify, when the frequency distribution is bimodal, a fusing build material temperature zone and a non-fusing build material temperature zone; and
determine a nominal temperature of the at least one identified temperature zone.

10. An object generation apparatus according to claim 9 , further comprising a controller to control the temperature control apparatus if a determined nominal temperature differs from an anticipated temperature.

11. An object generation apparatus according to claim 10 in which the temperature control apparatus comprises a plurality of heating elements, each heating element being to heat one of a plurality of portions of the layer of build material arranged on the print bed, wherein
the processor is to determine a nominal temperature of at least one temperature zone in the plurality of portions, and
the controller is to control the temperature of a heating element if a determined nominal temperature of the portion associated with that heating element differs from an anticipated temperature.

12. An object generation apparatus according to claim 11 in which a dedicated temperature sensor is provided for each portion.

13. An object generation apparatus according to claim 9 in which the temperature sensor comprises at least one of: an infrared sensor, a thermal camera; a thermopile array.

14. An object generation apparatus according to claim 9 wherein the processor is to compensate for aberrations for anomalies when determining temperatures for pixels representing sub-regions of at least a portion of a layer of build material.

15. A non-transitory machine-readable medium encoded with instructions executable by a processor and comprising instructions to:
determine, from an indication of the temperature of a plurality of sub-regions of build material in an object generation apparatus, a frequency distribution of sub-region temperatures;
identify whether the frequency distribution is indicative of two temperature zones within the build material, or indicative of one temperature zone, the temperature zones being indicative of one of fusing build material or non-fusing build material;
determine a nominal temperature value of the at least one identified temperature zone; and
generate an output to control a temperature control device such that at least one nominal temperature value tends towards a predetermined value.

16. A non-transitory machine-readable storage medium according to claim 15 in which the instructions to determine a nominal temperature value for at least one temperature zone are to determine at least one nominal temperature value for each of a plurality of portions of build material, and the instructions to generate an output are to generate an output to control a temperature control device associated with each portion such that at least one nominal temperature value determined for that portion tends towards a predetermined value.

17. A non-transitory machine-readable storage medium according to claim 15 further comprising:
instructions to determine, if a portion of build material is determined to have one temperature zone, whether the temperature of that temperature zone is indicative of fusing build material or non-fusing build material.

18. A non-transitory machine-readable storage medium according to claim 17 in which the instructions to determine whether, for build material having one temperature zone, the temperature for that temperature zone is indicative of fusing build material or non-fusing build material comprise:
instructions to determine if any portions of build material have two temperature zones, and, if so, to determine that the build material comprises a non-fusing build material temperature zone and a fusing build material temperature zone, instructions to determine a nominal temperature of the temperature zones, and instructions to determine if the temperature of a temperature zone of the portion of build material matches the temperature of the fusing build material temperature zone or the non-fusing build material temperature zone;
instructions to determine

Assignees

• Hewlett Packard Development Co

Inventors

• Vilajosana Xavier
• Tuset Pere
• Mostaccio Diego Javier

Classifications

• B29C64/165

  using a combination of solid and fluid materials, e.g. a powder selectively bound by a liquid binder, catalyst, inhibitor or energy absorber · CPC title

• B33Y30/00

  Apparatus for additive manufacturing; Details thereof or accessories therefor · CPC title

• B33Y50/02

  for controlling or regulating additive manufacturing processes · CPC title

• B29C64/153

  using layers of powder being selectively joined, e.g. by selective laser sintering or melting · CPC title

• B33Y10/00

  Processes of additive manufacturing · CPC title