Measuring X-ray CT apparatus and production work piece measurement method

Patent metadata

Field	Value
Publication number	US-11262319-B2
Application number	US-201916291699-A
Country	US
Kind code	B2
Filing date	Mar 4, 2019
Priority date	Mar 12, 2018
Publication date	Mar 1, 2022
Grant date	Mar 1, 2022

Abstract

When measuring a mass-produced work piece using a measuring X-ray CT apparatus, which is configured to emit X-rays while rotating a work piece that is arranged on a rotary table and to reconstruct a projection image thereof to generate volume data of the work piece, the present invention assigns values to volume data for a predetermined work piece and stores the same as master data; obtains volume data for a mass-produced work piece under identical conditions to the predetermined work piece; measures the volume data and obtains an X-ray CT measured value for the mass-produced work piece; and corrects the X-ray CT measured value for the mass-produced work piece using the master data.

First claim

What is claimed is:

1. A measuring X-ray CT apparatus that is configured to emit X-rays while rotating a work piece that is arranged on a rotary table and to reconstruct a projection image thereof to generate volume data of the work piece, the measuring X-ray CT apparatus comprising:
one or more memories that store:
a set of executable instructions, and
volume data for a predetermined work piece as master data, for which values are assigned ahead of time, wherein the predetermined workpiece is a hollow cylindrical workpiece and the master data includes ΔR o and ΔR i , which are calculated using the following master data formulas:
Δ R o =R co −R xo   (1)

Δ R i =R ci −R xi   (2)

wherein R co is an actual coordinate measuring machine measured value of an outer diameter of the predetermined workpiece, R xo is an X-ray CT measured value of the outer diameter of the predetermined workpiece, R ci is an actual coordinate measuring machine measured value of an inner diameter of the predetermined workpiece, and R xi is an X-ray CT measured value of the inner diameter of the predetermined workpiece; and
a processor, which when executing the set of executable instructions, is configured to operate as:
a system that obtains volume data for a production work piece under identical conditions to the predetermined work piece;
a system that measures the volume data for the production work piece and that obtains R wo , which is an X-ray CT measured value of the outer diameter of the production work piece, and R wi which is an X-ray CT measured value of the inner diameter of the production work piece; and
a corrector that corrects the X-ray CT measured value for the production work piece in accordance with the following:
R′ wo =R wo +ΔR o   (3)

R′ wi =R wi +ΔR i   (4)

Δα>Δβ  (5)

Δα+Δ B   (6)

wherein R′ wo is a corrected X-ray CT measured value for an outer diameter of the production workpiece and R′ wi is a corrected X-ray CT measured value for an inner diameter of the production workpiece, and
wherein Δα is a difference between the coordinate measuring machine measured values of the predetermined workpiece and the X-ray CT measured values of the predetermined workpiece, and Δβ is a difference between the X-ray CT measured values of the predetermined workpiece and the X-ray CT measured values of the production work piece.

2. The measuring X-ray CT apparatus according to claim 1 , wherein:
the production work piece includes a plurality of production work pieces, and
the predetermined work piece is a mass-produced work piece selected from the plurality of production work pieces.

3. A work piece measurement method of a measuring X-ray CT apparatus which, when measuring a production work piece, emits X-rays while rotating a work piece that is arranged on a rotary table, and reconstructs a projection image thereof to generate volume data of the work piece, the method comprising:
assigning values to volume data for a predetermined work piece, and storing the volume data as master data, wherein the predetermined workpiece is a hollow cylindrical workpiece and the master data includes ΔR o and ΔR i , which are calculated using the following master data formulas:
Δ R o =R co −R xo   (1)

Δ R i =R ci −R xi   (2)

wherein R co is an actual coordinate measuring machine measured value of an outer diameter of the predetermined workpiece, R xo is an X-ray CT measured value of the outer diameter of the predetermined workpiece, R ci is an actual coordinate measuring machine measured value of an inner diameter of the predetermined workpiece, and R xi is an X-ray CT measured value of the inner diameter of the predetermined workpiece;
obtaining volume data for a production work piece under identical conditions to the predetermined work piece;
measuring the volume data for the production work piece and obtaining R wo , which is an X-ray CT measured value of the outer diameter of the production work piece, and R wi , which is an X-ray CT measured value of the inner diameter of the production work piece; and
correcting the X-ray CT measured value for the production work piece, in accordance with the following:
R′ wo =R wo +ΔR o   (3)

R′ wi =R wi +ΔR i   (4)

Δα>Δβ  (5)

Δα+Δ B   (6)

wherein R′ wo is a corrected X-ray CT measured value for an outer diameter of the production workpiece and R′ wi is a corrected X-ray CT measured value for an inner diameter of the production workpiece, and
wherein Δα is a difference between the coordinate measuring machine measured values of the predetermined workpiece and the X-ray CT measured values of the predetermined workpiece, and Δβ is a difference between the X-ray CT measured values of the predetermined workpiece and the X-ray CT measured values of the production work piece.

4. The work piece measurement method according to claim 3 , wherein:
the production work piece includes a plurality of production work pieces, and
the predetermined work piece is a mass-produced work piece selected from the plurality of production work pieces.

5. The measuring X-ray CT apparatus according to claim 1 , wherein:
Δα relates to an error arising from a shape or a material of the predetermined workpiece.

6. The work piece measurement method according to claim 3 , wherein:
Δα relates to an error arising from a shape or a material of the predetermined workpiece.

7. The measuring X-ray CT apparatus according to claim 1 , wherein:
Δβ relates to a difference between a shape of the predetermined workpiece and a shape of the production work piece.

8. The work piece measurement method according to claim 3 , wherein:
Δβ relates to a difference between a shape of the predetermined workpiece and a shape of the production work piece.

9. The measuring X-ray CT apparatus according to claim 1 , wherein:
the predetermined workpiece comprises a first material and a second material, the first material and the second material having the same dimensions and different X-ray CT measured values.

10. The work piece measurement method according to claim 3 , wherein:
the predetermined workpiece comprises a first material and a second material, the first material and the second material having the same dimensions and different X-ray CT measured values.

Assignees

• Mitutoyo Corp

Inventors

• Asano Hidemitsu
• Kon Masato

Classifications

• G01N2223/3306

  object rotates · CPC title

• G06T2207/30164

  Workpiece; Machine component · CPC title

• G06T2207/30168

  Image quality inspection · CPC title

• G01N2223/419

  computed tomograph · CPC title

• G01N23/046 Primary

  using tomography, e.g. computed tomography [CT] · CPC title