Skip to content

Model-Based Inspection for Gap, Flush and Step

Ernie Husted
By Ernie Husted CEO, Verisurf Software Inc.

Measuring and inspecting gap, flush and step of adjacent surfaces, such as hatches, doors and intersecting body panels, has always been a challenge, usually requiring the inspection plan to incorporate intermediate processes or separate paper drawings.  This breaks the continuity of the all-important digital thread associated with Model-Based Definition (MBD) and opens the inspection routine up for human error.

Verisurf Software, which is built on a CAD platform, developed a 2-Point Analysis feature, which allows users to measure length, width, height, step, flush, or gap on any set of offset surfaces with only two surface point measurements. The displayed results show dimension type, measured value and nominal value—providing a quick way to identify the deviation between measured and nominal dimensions.

Verisurf 2-Point analysis is enabled when the Inspect/Build dialog is set to Measure Two Points. The operator can record points as needed. Instead of saving the individual surface deviations, Verisurf automatically saves the dimension value by utilizing the CAD nominals from the 3D model. In the screen image, the same panel is measured in nine locations in a matter of seconds, completely removing any input error from the technician. The on-screen info text also shows the individual analysis summary along with the actual and nominal step values.


A key benefit of 2-Point analysis is the ability to leverage an automated inspection plan since they share the same reporting properties as regular analysis objects. This improves productivity and further preserves the integrity of the inspection routine, maintaining consistency from one inspection to the next.  And because the location of the CAD distance value is determined from the location of the measured analysis pair, tapered or chamfered steps will not affect the measurement integrity. This process is great for measuring step dimensions on contoured shape surfaces, which is commonly needed for determining shim sizes for aircraft assembly.   

To save time reporting step results, a dimension field is included under Analysis in the Report Manager and can be included in all Verisurf report formats.

Verisurf Software is committed to 3D Model-Based inspection, with this new ability to quickly and accurately inspect direct dimensions using CAD surfaces, depending on the surface normal during the measurement. If both points have similar direction normals, Verisurf will calculate a Step, when two points have opposite facing normals, Verisurf will calculate Thickness and when facing each other Verisurf will calculate a Gap.

Many industries, including aerospace, automotive, energy and more must deal with the challenges of measuring and inspecting gap, flush and step. By automating the process and using the 3D CAD model as the design nominal, productivity, quality and data integrity are all improved.

  • View All Articles
  • Connect With Us

Webinars, White Papers and More!

SME's Manufacturing Resource Center keeps you updated on all of the latest industry trends and information. Access unlimited FREE webinars, white papers, eBooks, case studies and reports now!