AN ADDITIVE MANUFACTURING METHOD AND APPARATUS

• US 20190022946A1
• Filed: 11/14/2016
• Published: 01/24/2019
• Est. Priority Date: 11/16/2015
• Status: Active Grant

• Current Assignee: Renishaw PLC
• Original Assignee: Renishaw PLC
• Inventors: JONES, Nicholas Henry Hannaford, BROWN, Ceri, REVANUR, Ramkumar, MCFARLAND, Geoffrey
• Granted Patent: US 10,933,468 B2
• Time in Patent Office: Days
• CPC Class Codes: B22F 10/00 Additive manufacturing of workpieces or articles from metallic powder apparatus or devices therefor B22F12/00
• CPC Class Codes: B22F 10/10 Formation of a green body
• CPC Class Codes: B22F 10/28 Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• CPC Class Codes: B22F 10/30 Process control
• CPC Class Codes: B22F 10/32 of the atmosphere, e.g. composition or pressure in a building chamber
• CPC Class Codes: B22F 10/322 of the gas flow, e.g. rate or direction
• CPC Class Codes: B22F 12/49 Scanners
• CPC Class Codes: B22F 12/70 Gas flow means
• CPC Class Codes: B22F 12/90 Means for process control, e.g. cameras or sensors
• CPC Class Codes: B29C 64/153 using layers of powder being selectively joined, e.g. by selective laser sintering or melting
• CPC Class Codes: B29C 64/245 Platforms or substrates support structures intended to be sacrificed after manufacture B29C64/40
• CPC Class Codes: B29C 64/268 using laser beams; using electron beams [EB]
• CPC Class Codes: B29C 64/393 for controlling or regulating additive manufacturing processes
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 30/00 Apparatus for additive manufacturing; Details thereof or accessories therefor
• CPC Class Codes: B33Y 50/02 for controlling or regulating additive manufacturing processes
• CPC Class Codes: G05B 19/4093 characterised by part programming, e.g. entry of geometrical information as taken from a technical drawing, combining this with machining and material information to obtain control information, named part programme, for the NC machine
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

A method of monitoring an additive manufacturing apparatus. The method includes receiving one or more sensor signals from the additive manufacturing apparatus during a build of a workpiece, comparing the one or more sensor signals to a corresponding acceptable process variation of a plurality of acceptable process variations and generating a log based upon the comparisons. Each acceptable process variation of the plurality of acceptable process variations is associated with at least one state of progression of the build of the workpiece and the corresponding acceptable process variation is the acceptable process variation associated with the state of progression of the build when the one or more sensor signals are generated.

Claims

1. A method of monitoring an additive manufacturing apparatus comprising receiving one or more sensor signals from the additive manufacturing apparatus during a build of a workpiece, comparing the one or more sensor signals to a corresponding acceptable process variation of a plurality of acceptable process variations and generating a log based upon the comparisons, wherein each acceptable process variation of the plurality of acceptable process variations is associated with at least one state of progression of the build of the workpiece and the corresponding acceptable process variation is the acceptable process variation associated with the state of progression of the build when the one or more sensor signals are generated.

2. A method according to claim 1, wherein the state of progression of the build of the workpiece comprises a position on the workpiece/in a build volume.

3. A method according to claim 2, wherein the additive manufacturing apparatus comprises an energy beam and/or plasma jet for consolidating material, each acceptable process variation of the plurality of acceptable process variations associated with at least one position in which material is consolidated in the build using the energy beam and/or plasma jet, and the method comprises determining the corresponding acceptable process to which the sensor signal is compared from the position in which material is consolidated by the energy beam and/or plasma jet when the sensor signal is generated.

4. A method according to claim 2, wherein the additive manufacturing apparatus comprises a movable build support, wherein layers are consolidated to form the workpiece on the build support, each acceptable process variation of the plurality of acceptable process variations associated with at least one layer number, the method comprising determining the corresponding acceptable process to which the sensor signal is compared from the layer number being processed during generation of the sensor signal.

5. A method according to claim 1, wherein the state of progression of the build of the workpiece comprises a time from a set event in the build.

6. A method according to claim 5, wherein each acceptable process variation of the plurality of acceptable process variations is associated with at least one build time and the method comprises determining the corresponding acceptable process variation to which the sensor signal is compared from a build time at which the sensor signal is generated.

7. A method according to claim 1, wherein the state or progression of the build of the workpiece comprises an order in which the sensor signals are generated.

8. A method according to claim 7, wherein a specified order of the plurality of acceptable process variations corresponds to an order in which the sensor signals are generated during the build and the method comprises determining the corresponding acceptable process variation to which the sensor signal is compared from an order in which the sensor signals are generated during the build.

9. A method according to claim 1, wherein the acceptable process variation comprises acceptable variations in one or more of:

a) a temperature in a build chamber of the additive manufacturing apparatus

b) a temperature of flowable material to be consolidated

c) a temperature of a melt pool

d) intensity of light collected by a sensor

e) spectral emission from the melt pool

f) dimensions of the melt pool

g) a comparison of images of adjacent layers

h) a gas pressure in the build chamber

i) oxygen concentration in the build chamber

j) pump speed of a pump for recirculating gas through the build chamber

k) elevator position, speed and/or acceleration

l) wiper position, speed and/or acceleration of the wiper

m) load on the wiper

n) a predicted temperature of current or future portions of the workpiece/build from a thermal model based upon sensor signals

o) dosing of material

p) acoustic signals

q) images of a powder bed

r) images of the consolidated material, and/or

s) a rate of change of any one of (a) to (r).

10. A method according to claim 1, wherein there is a one-to-one correlation between each acceptable process variation of the plurality of acceptable process variations and each state of progression of the build of the workpiece for which sensor signals are generated.

11. A method according to claim 1, wherein at least one of the acceptable process variations is associated with a plurality of states of progression of the build of the workpiece.

12. A method according to claim 1, wherein the plurality of acceptable process variations only apply to one or more portions of the workpiece, as specified by the associated state of progression of the build of the workpiece.

13. A method according to claim 1, wherein the sensor signals comprise signals or are derived from signals from one of more of the following sensors of the additive manufacturing apparatus:

a) a pyrometer,

b) an acoustic sensor,

c) a thermal camera,

d) a visible light camera,

e) a photodiode,

f) a spectrometer

g) a force feedback device.

h) a pressure sensor,

i) a mass flow sensor,

j) an oxygen sensor,

k) an encoder, and/or

l) accelerometer.

14. A method according to claim 1, wherein the acceptable process variation is a variation in a difference between two sensed values.

15. A method according to claim 1, comprising controlling the additive manufacturing apparatus during the build based upon the comparison of the sensor signals to the corresponding acceptable process variation.

16. A method according to claim 1, comprising controlling parameters of the build on the additive manufacturing apparatus to return the sensor signals to and/or maintain the sensor signals within the corresponding acceptable process variations.

17. A method according to claim 1, comprising halting build of the workpiece if the sensor signals fall outside of the acceptable process variation.

18. A method according to claim 17, wherein halting build of the workpiece comprises halting the entire build.

19. A method according to claim 17, wherein halting the build of the workpiece comprises suppressing build of the workpiece whilst continuing with the build of other workpieces of the build.

20. A method according to claim 1, comprising only storing a subset of sensor data derived from the sensor signals based upon sensor signals that fall outside of the corresponding acceptable process variation.

21. A method according to claim 1, comprising storing the sensor data together with coordinate data localising the sensor data in the coordinate system of the workpiece or build volume and using the coordinate data to identify regions of the workpiece in which the sensor data falls outside the acceptable process variation.

22. A method according to claim 1, comprising controlling the additive manufacturing apparatus to repair a region of the workpiece based on sensor signals for that region falling outside the corresponding acceptable process variation.

23. A method according to claim 1, comprising controlling the additive manufacturing apparatus to carry out a further inspection of a region of the workpiece based on sensor signals for that region falling outside the corresponding acceptable process variation.

29. A data carrier having instructions therein, which, when executed by a processor, cause the processor to carry out the method of claim 1.

24. A controller for monitoring an additive manufacturing apparatus, the controller comprising a processor arranged to receive one or more sensor signals from the additive manufacturing apparatus during a build of a workpiece, compare the one or more sensor signals to a corresponding acceptable process variation of a plurality of acceptable process variations and generate a log based upon the comparisons, wherein each acceptable process variation of the plurality of acceptable process variations is associated with at least one state of progression of the build of the workpiece and the corresponding acceptable process variation is the acceptable process variation associated with the state of progression of the build when the one or more sensor signals are generated.

25. A controller according to claim 24, wherein the processor is arranged to receive the plurality of acceptable process variations together with the build instructions for building the workpiece.

26. A controller according to claim 24, comprising memory and the processor is arranged to store the plurality of acceptable process variations in memory on receiving the build instructions and erase the plurality of acceptable process variations from memory after completion of the build of the workpiece or when build instructions for a different workpiece are uploaded to the controller.

27. A controller according to claim 24, wherein the processor is arranged to only store a subset of sensing data derived from the sensor signals based upon sensor signals that fall outside the corresponding acceptable process variation.

28. An additive manufacturing apparatus comprising a controller according to claim 24.

30. A method of generating instructions for the building of a workpiece in an additive manufacturing apparatus, the method comprising building one or more initial workpieces nominally identical to at least a portion of the workpiece with the and/or one or more corresponding additive manufacturing apparatus, receiving a set of sensor signals from the and/or the one or more corresponding additive manufacturing apparatus during the build of the or each initial workpiece, evaluating the one or more initial workpieces to determine if the or each initial workpiece meets specified requirements and associating the or each set of sensor signals with one or more quality identifiers identifying whether all or a portion of the sensor signals of the set represent sensor signals for a build that meets the specified requirements and determining, from the one or more sets of sensor signals and associated quality identifiers, a plurality of acceptable process variations for a corresponding set of sensor signals generated during a subsequent build of the workpiece using the additive manufacturing apparatus.

31. A method according to claim 30, wherein the acceptable process variation is determined by a statistical analysis of the natural process variation in the sensor signals during the build of the one or more initial workpieces and whether the sensor signal relate to a portion of the workpiece evaluated as meeting the specified requirements.

32. A method according to claim 30, wherein the method is used in the manufacture of a series of nominally identical workpieces, the acceptable process variation refined/evolved with the sensor data from each build as more of the workpieces are built.

33. A method according to claim 30, wherein the initial workpiece(s) is/are built in a position within a build volume identical to the position in which the workpiece is subsequently built.

34. A method according to claim 30, wherein the initial workpiece(s) is/are built in a position within a build volume different to the position in which the workpiece is subsequently built and a mapping is applied to transform the acceptable process variations determined for the position of the initial workpieces in the build volume to acceptable process variations for the position in the build volume in which the workpiece is built.

35. A method according to claim 30, wherein the workpiece is one of a set of workpieces to be built together in a single build, the initial workpiece(s) also built together with an identical set of workpieces in an identical layout in a build volume to that used when building the workpiece.

36. A method according to claim 30, wherein the workpiece is one of a set of workpieces to be built together in a single build in a first build layout, the initial workpiece(s) built in a second, different build layout in a build volume and a mapping is used to transform the acceptable process variations determined from the sensor data of the initial workpiece in the second build layout into acceptable process variations for a build of the workpiece in the first build layout.

37. A method according to claim 30, wherein the corresponding additive manufacturing apparatus has/have nominally identical functionality to the additive manufacturing apparatus.

38. A method according to claim 30, wherein the specified requirement for a build of the initial workpieces comprises completion of the build of the workpiece, a density of the consolidated material, an absence or a maximum number or size of cracks, voids or inclusions in the workpiece, surface finish, porosity, a crystal structure and/or a chemical composition of the workpiece.

39. A method according to claim 30, wherein the specified requirement comprises a specified compressive strength, tensile strength, shear strength, hardness, micro-hardness, bulk modulus, shear modulus, elastic modulus, stiffness, elongation at fracture, Poisson'"'"'s ratio, corrosion resistance, dissipation factor, conductivity and/or magnetic properties of the workpiece.

40. A method according to claim 30, wherein the specified requirement is a specified performance when carrying out functional testing.

41. A method according to claim 30, wherein, where only a region of the initial workpiece is deemed not to meet the specified requirements, the method comprises receiving from the user identification of whether all sensor signals for the build of that initial workpiece are identified as relating to a build that fails to meet the specified requirements or whether only the sensor signals associated with the region deemed to not meet the specified requirements should be identified as such with the other sensor data relating to an acceptable build.

42. A method according to claim 30, wherein evaluation of the initial workpiece(s) to determine if the workpiece meets the specified requirements comprises non-destructive testing (NDT).

43. A method according to claim 30, wherein evaluation of the initial workpiece(s) comprises destructive testing.

44. The method according to claim 30, comprising associating each acceptable process variation with at least one state of progression of the build of the workpiece.

45. The method according to claim 30, comprising determining a set of primary acceptable process variations from the one or more sets of sensor signals and associated quality identifiers, each primary acceptable process variation associated with a state of progression of the build of the workpiece, generating a reduced set of secondary acceptable process variations from the set of primary acceptable variations, at least one of the secondary acceptable process variations associated with a plurality of states of progression of the build of the workpiece.

46. A method according to claim 45, wherein the reduced set of secondary acceptable process variations are generated by grouping together similar ones of the primary acceptable process variations and generating one of the secondary acceptable process variations for each group, each secondary acceptable process variation associated with a plurality of states of progression corresponding to the states of progression associated with the primary acceptable process variations of the corresponding group for which the secondary acceptable process variation is generated.

47. A method according to claim 46, wherein each secondary acceptable process variation is generated from characteristics of the primary acceptable process variations of the corresponding group for which the secondary acceptable process variation is generated.

48. A method according to claim 46, wherein the primary acceptable process variations are grouped using values derived from a similarity function.

49. A method according to claim 48, comprising receiving a user input identifying different regions of the workpiece for which different similarity criteria are used for grouping the primary acceptable process variations together.

61. A data carrier having instructions thereon, which, when executed by a processor, cause the processor to perform in accordance with claim 30.

50. A system for generating instructions for controlling an additive manufacturing apparatus, the system comprising a processor arranged to receive a set of sensor signals for each build of one or more initial workpieces, nominally identical to at least a portion of the workpiece, with the and/or one or more corresponding additive manufacturing apparatus, receive an indication of whether the or each initial workpiece meets specified requirements, associate the or each set of sensor signals with one or more quality identifiers identifying whether all or a portion of the sensor signals of the set represent sensor signals for a build that meets the specified requirements and determine, from the one or more sets of sensor signals and associated quality identifiers, a plurality of acceptable process variations for a corresponding set of sensor signals generated during a subsequent build of the workpiece using the additive manufacturing apparatus.

51. A system according to claim 50, wherein the processor is arranged to associate the acceptable process variation with a state of progression of the build.

52. A system according to claim 50, wherein the state of progression is a position within the build volume/on the workpiece.

53. A system according to claim 50, wherein the state of progression is a time during the build.

54. A system according to claim 50, wherein the state of progression is an order in which the sensor signals are collected during the build.

55. A system according to claim 50, wherein the processor is arranged to generate a build file comprising scan paths and scan parameters for an energy beam or plasma jet to follow when consolidating material in the formation of the workpiece in a layer-by-layer manner and the acceptable process variations.

56. A system according to claim 50, wherein the processor is arranged to determine a set of primary acceptable process variations from the one or more sets of sensor signals and associated quality identifiers, each primary acceptable process variation associated with a state of progression of the build of the workpiece and generate a reduced set of secondary acceptable process variations from the set of primary acceptable variations, at least one of the secondary acceptable process variations associated with a plurality of states of progression of the build of the workpiece.

57. A system according to claim 56, wherein the reduced set of secondary acceptable process variations is generated by grouping together similar ones of the primary acceptable process variations and generating one of the secondary acceptable process variations for each group, each secondary acceptable process variation associated with a plurality of states of progression corresponding to the states of progression associated with the primary acceptable process variations of the corresponding group for which the secondary acceptable process variation is generated.

58. A system according to claim 57, wherein each secondary acceptable process variation is generated from characteristics of the primary acceptable process variations of the corresponding group for which the secondary acceptable process variation is generated.

59. A system according to claim 56, wherein the primary acceptable process variations are grouped using values derived from a similarity function.

60. A system according to claim 59, wherein the processor is arranged to receive a user input identifying a region of the workpiece and group the primary acceptable process variations associated with the identified region using a different similarity criteria to that used to group primary acceptable process variations associated with other regions of the workpiece.

62. A method of controlling an additive manufacturing apparatus comprising providing instructions for building a workpiece by consolidating material in a layer-by-layer manner using the additive manufacturing apparatus and determining a plurality of acceptable process variations for sensor signals of the additive manufacturing apparatus and generating a build file comprising the instructions and the plurality of acceptable process variations.

63. A method according to claim 62, wherein each of the acceptable process variations is associated with at least one state of progression of the build of the workpiece.

64. Apparatus comprising a processor, the processor arranged to carry out the method of claim 62.

65. A data carrier having instructions stored thereon, which, when executed by a processor, cause the processor to carry out the method of claim 62.

66. A data carrier having thereon a build file for instructing an additive manufacturing apparatus in the building of a workpiece in a layer-by-layer manner, the build file comprising instructions for how the additive manufacturing apparatus is to build the workpiece and acceptable process variations for sensor signals generated by sensors of the additive manufacturing apparatus during the building of the workpiece.

67. A method of monitoring an additive manufacturing apparatus comprising capturing a plurality of thermal images of a material layer as the material is consolidated and determining a rate of change in temperature of consolidated areas from a comparison of the plurality of thermal images and storing a record of the rate of change of temperature of the consolidated areas.

69. A data carrier having instructions therein, which, when executed by a processor, cause the processor to carry out the method of claim 67.

68. An additive manufacturing apparatus comprising a support, a material source for providing material to the support and a radiation source for consolidating layers of the material to form a workpiece in a layer-by-layer manner, a thermal camera for imaging the material as the material is consolidated and a processor arranged to receive images from the thermal camera, compare a plurality of images of consolidated material to determine a rate of change of temperature of the consolidated material.

70. A method of monitoring an additive manufacturing apparatus comprising capturing images of consecutive layers of material, determining a difference in the images between corresponding regions of the consecutive layers for a plurality of corresponding regions, determining from the differences a dissimilarity value quantifying an overall difference in the images for the plurality of corresponding regions and controlling the additive manufacturing apparatus based upon whether the dissimilarity value is above or below a threshold value.

71. A method according to claim 70, wherein the images are consecutive layers of material before consolidation with an energy beam/plasma jet.

72. A method according to claim 70, wherein the threshold value is set based upon expected dissimilarity values identified for two consecutive material layers that have been formed correctly and do not have consolidated parts projecting therethrough.

73. A method according to claim 72, wherein the threshold value is determined from a statistical analysis of the dissimilarity values generated for such correctly formed consecutive layers, the threshold value set above the statistically determined natural variation.

74. A method according to claim 70, wherein the corresponding regions are corresponding individual or groups of pixels of the images.

75. A method according to claim 70, wherein the dissimilarity value are determined from the differences between corresponding regions, wherein greater differences are weighted to disproportionately contribute to the dissimilarity value compared to the magnitude of the difference.

77. A data carrier having instructions therein, which, when executed by a processor, cause the processor to carry out the method of claim 70.

76. An additive manufacturing apparatus comprising a support, a material source for providing material to the support and a radiation source for consolidating layers of the material to form a workpiece in a layer-by-layer manner, a camera for imaging consecutive layers of the material and a processor arranged to determine a difference in the images between corresponding regions of the consecutive layers for a plurality of corresponding regions, determine from the differences a dissimilarity value quantifying an overall difference in the images for the plurality of corresponding regions and control the additive manufacturing apparatus based upon whether the dissimilarity value is above or below a threshold value.

78. A method of monitoring an additive manufacturing apparatus comprising capturing an image of a layer of material that has been spread by a wiper but before consolidation of the layer with an energy beam, determining a dissimilarity value quantifying a difference between different columns of the image and controlling the additive manufacturing apparatus to change/adjust the wiper and/or generate an alert for a user to check the wiper based upon whether the dissimilarity value is above or below a threshold value.

80. A data carrier having instructions therein, which, when executed by a processor, cause the processor to carry out the method of claim 78.

79. An additive manufacturing apparatus comprising a support for supporting a material bed, a material source for providing material, a wiper for spreading material provided by the material source across the material bed and a radiation source for generating an energy beam for consolidating layers of the material to form a workpiece in a layer-by-layer manner, a camera for capturing images of each layer before consolidation of the layer with the energy beam, and a processor arranged to determine, for each image, a dissimilarity value quantifying a difference between different columns of the image and control the additive manufacturing apparatus to change/adjust the wiper and/or generate an alert for a user to check the wiper based upon whether the dissimilarity value is above or below a threshold value.

81. A method of monitoring an additive manufacturing process in which a workpiece is built by consolidating material in a layer-by-layer manner, the method comprising receiving sensor signals from the additive manufacturing apparatus during a build of a workpiece, identifying from the sensor signals a region of the workpiece for further inspection and maneuvering a sensor system to capture further sensor data from the identified region.

82. A method according to claim 81, wherein the sensor system comprises an optical sensor system for capturing radiation generated by the region.

83. A method according to claim 82, wherein the optical system comprises steerable optics for capturing radiation emitted from a selected locality on the workpiece, the method comprising controlling the steerable optics for capturing radiation from the identified region.

84. A method according to claim 82, wherein the optical system shares optical components with an optical system for directing a laser beam for consolidating the material, wherein the optical system is directed to capture further data on a region in between consolidation of material with the laser beam.

85. A method according to claim 82, wherein the optical system comprises an optical system separate from the system for steering an energy beam that is used to consolidate material.

86. A method according to claim 81, wherein a region is identified for further inspection if the sensor signals fall outside of an acceptable process variation.

89. A data carrier having instructions therein, which, when executed by a processor, cause the processor to carry out the method of claim 81.

87. A controller for controlling an additive manufacturing apparatus, the controller comprising a processor arranged to receive sensor signals from the additive manufacturing apparatus during a build of a workpiece, identify from the sensor signals a region of the workpiece for further inspection and generate instructions for maneuvering a sensor system to capture further sensor data from the identified region.

88. An additive manufacturing apparatus comprising a controller according to claim 87.

90. A method of generating instructions for the building of a workpiece in an additive manufacturing apparatus, the method comprising receiving a set of primary acceptable process variations for sensor signals generated during a build of the workpiece using the additive manufacturing apparatus, each primary acceptable process variation applicable to sensor signals generated during a particular state of progression of the build of the workpiece associated with that primary acceptable process variation and generating a reduced set of secondary acceptable process variations from the set of primary acceptable variations, at least one of the secondary acceptable process variations associated with a plurality of states of progression of the build of the workpiece.

91. A method according to claim 90, wherein the reduced set of secondary acceptable process variations are generated by grouping together similar ones of the primary acceptable process variations and generating one of the secondary acceptable process variations for each group, each secondary acceptable process variation associated with a plurality of states of progression corresponding to the states of progression associated with the primary acceptable process variations of the corresponding group for which the secondary acceptable process variation is generated.

92. A method according to claim 91, wherein each secondary acceptable process variation is generated from characteristics of the primary acceptable process variations of the corresponding group for which the secondary acceptable process variation is generated.

93. A method according to claim 90, wherein the primary acceptable process variations are grouped using values derived from a similarity function.

94. A method according to claim 93, comprising receiving a user input identifying different regions of the workpiece for which different similarity criteria are used for grouping the primary acceptable process variations together.

95. A controller comprising a processor, the processor arranged to carry out the method of claim 90.

96. A data carrier having instructions therein, which, when executed by a processor, cause the processor to carry out the method of claim 90.

97. A method for generating instructions for machines of a manufacturing chain used to manufacture a workpiece, the manufacturing chain including an additive manufacturing apparatus, the method comprising receiving sensor signals from the additive manufacturing apparatus during the build of a workpiece and generating instructions for at least one further machine of the manufacturing chain based upon the sensor signals.

98. A method according to claim 97, wherein the method comprises comparing the sensor signals to acceptable process variations in the sensor signals and instructions for at least one further machine of the manufacturing chain are generated based upon the comparison.

99. A method according to claim 97, wherein the further machine comprises a subtractive manufacturing machine, a polishing machine, a support removal machine, a measuring machine, a further additive manufacturing machine, a machine for relieving thermal stresses in the workpiece, and/or a machine for reconditioning a build substrate.

100. Apparatus for generating instructions for machines of a manufacturing chain used to manufacture a workpiece, the apparatus comprising a processor arranged to carry out the method of claim 97.

101. A data carrier having machine-readable instructions stored thereon, wherein the machine-readable instructions, when executed by a processor, cause the processor to carry out the method of claim 97.

102. A manufacturing chain for manufacturing a workpiece, the manufacturing chain comprising an additive manufacturing machine, at least one further machine and apparatus according to claim 100.

103. A method of manufacturing a workpiece comprising using an additive manufacturing apparatus, in which the workpiece is formed by consolidating material in a layer-by-layer manner, the method comprising receiving sensor signals from a sensor of the additive manufacturing apparatus during a build of the workpiece and displaying a representation of each sensor signal together with a corresponding acceptable process deviation for signals from that sensor for the state for progression of the build at the time the sensor signal is captured, wherein different ones of the states of progression are associated with different acceptable process variations.

104. A visualisation apparatus to be used in a manufacturing process, the visualisation apparatus comprising a processor and a display, wherein the processor is arranged to carry out the method of claim 103 to cause the display to display the representation.

105. A data carrier having instructions therein, which, when executed by a processor, cause the processor to carry out the method of claim 103.

106. A method of manufacturing a plurality of nominally identical workpieces using one or more additive manufacturing apparatus, in which each workpiece is formed by consolidating material in a layer-by-layer manner, the method comprising receiving sensor signals from a sensor of the or each additive manufacturing apparatus during a build of the workpieces, determining a plurality of acceptable process variations from the sensor signals for different states of progression of the build and displaying a representation of each sensor value for at least one of the workpieces together with a corresponding acceptable process deviation of the plurality of acceptable process variations for the state for progression of the build at the time the sensor signal is captured.

107. A visualisation apparatus to be used in a manufacturing process, the visualisation apparatus comprising a processor and a display, wherein the processor is arranged to carry out the method of claim 106 to cause the display to display the representation.

108. A data carrier having instructions therein, which, when executed by a processor, cause the processor to carry out the method of claim 106.