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BORN Tutorial -- Using Coordinate Systems
to Control a Part
Provided by Mel Boss
You can also download the PowerPoint presentation for your use.
Step 1: Toggle Local/Global Switch - "local switch off" should appear in list window. Next, "Name Part" and select the (yellow) coordinate system.
The BASE coordinate system (CS2) should represent a key feature of the part...
Step 2: You may create other coordinate systems that are offset from the base. Select the command for "coordinate system" and pick CS2. Enter "X,Y,Z" translation from the selected CS2.
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Tip: You must pick CS2 to
create the offset CS. The options for translation and rotation will not appear if part
geometry such as edge or face is chosen.
Note: CS3, the new, offset CS, appears on the part history tree as a Minor Operation. |
OPTIONAL: You may modify the name and appearance of the offset CS to distinguish it from the base CS2.
Select command to "Modify" and pick CS3 - Modify options Form. You may rename, change size and color of CS3. In this example, CS3 is renamed to "Datum_A".
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Note: The size of the CS is dynamic per zoom factor - "Redisplay". Size factor .15 is standard. Use .10 for offset CS such as CS3. This input causes CS3 to always appear smaller than CS2. |
Sketch on a plane and extrude (or Revolve) to create a feature.
STEP 3: "Sketch in Place" and pick a plane on CS2 - renamed "BORN". Focus on CS2 origin to project a related (blue) point. Use this point to create an important part feature - such as the intersection of three datum planes.
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Tip: If you are experiencing problems - such as focus point appears yellow (unrelated); Extrude command produces a "new part" - check to make sure that you named the "part" - go back to step 1. |
Create a second feature by sketching on CS3 (renamed "Datum_A")
Sketch in Place on the XY plane of CS "Datum_A" a circle - "Dia_Motor_Cutout". Focus on CS origin a (blue) point for circle center.
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Tip: When you sketch on a reference plane or CS, be sure to check the direction of the extrude. Unlike a solid’s face, a reference plane has no material side. You may find that you are cutting air or protruding into material. If you error, simply modify feature parameters and reverse the extrude direction. |
This part’s HISTORY TREE shows construction steps and reference coordinate systems.
Coordinate systems CS2 (BORN) and CS3 (Datum_A) appear as Minor Operations on the History Tree. Minor Operations appear compressed initially; "Double Click" on the "pig tail" to expand the minor operation display (to appear as shown below).
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NOTE: The placement on a part’s History Tree of a minor operation (such as reference geometry) can be very important. Reference geometry will always occur on the part’s History Tree as near its "Base" as possible. |
Reference Geometry comes in two flavors: Topological and Relational
| Relational Reference Geometry is defined by geometric and dimensional relationships from either part geometry or other reference geometry - | Examples
of Relational Reference Geometry:
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| Topological Reference Geometry is defined by part geometry, and occurs on the History Tree node that completes its definition. | Examples
of Topological Reference Geometry:
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** These are the Reference Geometries I use most often. Offset CS has replaced most plane and line functions. The CS is more functional and has an easier to control display capability. Reference Line - Intersect can be VERY valuable at times. ** These are the Reference Geometries I use most often. Offset CS has replaced most plane and line functions. The CS is more functional and has an easier to control display capability. Reference Line - Intersect can be VERY valuable at times.
Using the BORN method for part construction provides flexibility to accommodate design changes.
To change the Dia_Motor_Cutout to a .30 clearance rather than a "thru-cut", the dimension "CS3_Z" for Datum_A was increased from 0 to .20. That is, the plane it was sketched on was moved "forward" .20.
Summary: to create a BORN related part:
 | Toggle LOCAL ORIGIN OFF - yellow CS appears. |
| Name the CS as a PART. |
| Sketch in Place on one of the 3 planes of CS2. |
| Focus on the CS2 origin to create a blue, related point. |
| Constrain sketch. |
| Extrude, Revolve, Loft etc. |
