4 Study on a Digital Inspection Method for Aircraft Tubing Assembly
43
Central point of left fixed joint
Sleeve-fitting
Central point of tubing
Sleeve-fitting
Tangent point of tubing center line
Locating point of clamp
Central point of tubing
Bent section
Central point of right fixed joint
Butt clearance
Angle deviation
M isalignment
Line section
Fig. 4.1 Digital inspection plan for tubing assembly
4.2.1 Analysis of Tubing Assembly Datum
Generally, three-step method is used in aircraft tubing assembly. The first step is
to align the left and right tubing end with the fixed joint in aircraft and make them
concentric; the second step is to fix the middle part of tubing on the locating point of
the clamp; the third step is to tighten the nuts of the left and right tubing end. During
the assembly process, it is necessary to check that the angle deviation, butt clearance
and misalignment between the central points of the tubing end and those of the
fixed joints, avoiding exceeding the specified values. Therefore, tubing assembling
positioning datum is determined by two central points of fixed joints and one locating
point of a clamp.
4.2.2 Data Extraction on the Centreline of Tubing
Due to the geometric and structural features of the tubing, the deviation of tubing
centreline can directly represent the deviation of tubing shape. Additionally, the
central coordinates of the circle can be measured by the existing commercialized
fork laser scanning equipment. By continuously scanning the contour of lines of
tubing, the coordinates of central points of two tubing ends and those of several
consecutive measured points on the lines can be directly obtained; the centreline’s
equation in the line section and the coordinates of the tangent points to the bent section
are obtained by the calculation method, viz., finding the mean values of the multiple
points for the centreline. Therefore, the two ends coordinates in the centreline and
the coordinates of the tangent points to the bent section can be used to calculate and
express the actual shape of the tested tubing completely, as shown in Fig. 4.2.
43
Central point of left fixed joint
Sleeve-fitting
Central point of tubing
Sleeve-fitting
Tangent point of tubing center line
Locating point of clamp
Central point of tubing
Bent section
Central point of right fixed joint
Butt clearance
Angle deviation
M isalignment
Line section
Fig. 4.1 Digital inspection plan for tubing assembly
4.2.1 Analysis of Tubing Assembly Datum
Generally, three-step method is used in aircraft tubing assembly. The first step is
to align the left and right tubing end with the fixed joint in aircraft and make them
concentric; the second step is to fix the middle part of tubing on the locating point of
the clamp; the third step is to tighten the nuts of the left and right tubing end. During
the assembly process, it is necessary to check that the angle deviation, butt clearance
and misalignment between the central points of the tubing end and those of the
fixed joints, avoiding exceeding the specified values. Therefore, tubing assembling
positioning datum is determined by two central points of fixed joints and one locating
point of a clamp.
4.2.2 Data Extraction on the Centreline of Tubing
Due to the geometric and structural features of the tubing, the deviation of tubing
centreline can directly represent the deviation of tubing shape. Additionally, the
central coordinates of the circle can be measured by the existing commercialized
fork laser scanning equipment. By continuously scanning the contour of lines of
tubing, the coordinates of central points of two tubing ends and those of several
consecutive measured points on the lines can be directly obtained; the centreline’s
equation in the line section and the coordinates of the tangent points to the bent section
are obtained by the calculation method, viz., finding the mean values of the multiple
points for the centreline. Therefore, the two ends coordinates in the centreline and
the coordinates of the tangent points to the bent section can be used to calculate and
express the actual shape of the tested tubing completely, as shown in Fig. 4.2.