VTube-STEP Model-based Definition (MBD) and Why It Is Important

What is Model-based Definition?

"Model-based definition (MBD), sometimes digital product definition, is the practice of using 3D models (such as solid models, 3D PMI, and associated metadata) within 3D CAD software to define (provide specifications for) individual components and product assemblies."

VTube-STEP and VTube-LASER ENABLE Model-based Definition for Tube Fabricators

An essential feature in all versions of VTube is the ability to import generic solid models of tube shapes in the STEP or IGES formats and then calculate and derive all of the following: Part Number (based on the incoming filename) XYZ centerline Radius values for every bend Diameter Wall thickness Bender data Cut Length

Explain the Benefits of Model-based Definition

The benefits of MBD are significant:

1. ELIMINATES KEYBOARD REENTRY
   Creating tube bender data from a solid model eliminates keyboard entry of centerline data for the nominal or master part. This is a huge benefit, considering many mistakes are made due to misreading or mistyping numbers from one data grid to the next.
   
   
2. Three TIMES FASTER THAN KEYBOARD ENTRY in VTube
   Importing data from a solid model tube is three times (or more) faster than entering it on a keyboard, even if the keyboard entry is perfect the first time.
   
   
3. VISUAL CROSS-CHECK
   Model-based definition gives instant visual feedback and confirmation that the part is correct, because the derived parametric model is superimposed on top of the imported model on the same screen.

Compare TRADITIONAL KEYBOARD INPUT and MBD IMPORT Methods

To demonstrate the speed difference, we will use this tube shape:

Traditional Keyboard Entry Method - TIME REQUIRED: 1 Minute 33 Seconds

In traditional data entry, the coordinate data is manually entered by typing the numerical data from a print or layout in this format:

The time required to enter the data by a VTube expert, including the coordinates above, part name, diameter, wall thickness, and default radius, is 1 minute 33 seconds.

Operators familiar with data entry like this will recognize that this pace is very fast for keyboard entry. Since this part is so simple, the time recorded DOES NOT INCLUDE DOUBLE-CHECKING THE COORDINATES. OTHER PARTS WITH THE SAME COORDINATE COUNT COULD EASILY REQUIRE MORE TIME because they would require double-checking the values input to the original print.

If the original print has no XYZ centerline grid (uses linear dimensions), then keyboard entry is MUCH SLOWER than what was recorded here.

MDB Solid Model Import Method - TIME REQUIRED: 30 SECONDS

The MBD method is significantly faster and enhances data integrity while importing data. This is the result of an import in VTube for the same part. (The model also includes a non-tubular part of the tube - the tabletop.)

Only 30 seconds are required to open the file, load the file, completely import the data by a VTube expert, and derive all the data entered above automatically.

This is what was calculated:

1. CENTERLINE COORDINATES: VTube calculated the centerline coordinates from the straight sections selected.
2. RADIUS: VTube calculated the radius values because the straights are built from tangent point to tangent point (where the straights meet the bends).
3. DIAMETER: VTube calculated the diameter from the largest cylinder selected.
4. WALL THICKNESS: VTube found the wall thickness because we also selected the inner wall of straight 7 (see the end at point 8 in the image above).
5. PART NUMBER: The part number is filled using the incoming filename with the path removed.
6. CUT LENGTH: The cut length is automatically calculated during import.