🔪 Blade Profile Generation System

1. System Overview

The Blade Profile Generation System creates fixture blades that precisely conform to part geometry. A blade is a flat steel plate that supports a part during waterjet or laser cutting operations. The blade must:

• Pass through the part at a specified position and angle
• Have cutouts matching the part's cross-section at that location
• Support compound angles (not just orthogonal X/Y/Z orientations)
• Handle hollow parts with multiple disconnected profile regions

Key Innovation: Dual-Section Method

Unlike simple projection-based approaches, this system sections the part at both faces of the blade (front and back), then combines the profiles. This correctly handles compound angles where front and back sections differ.

2. Prerequisites & Limitations

Understanding the Problem

When a blade plane passes through the hollow interior of an open part (e.g., an open-topped box), the sectioning operation produces multiple disconnected wall profiles. The mosaic algorithm then tries to combine these profiles, but creates spurious "gap" regions between the wall sections that don't correspond to actual part material.

Two Solutions

Option 1: Make the Part Watertight (Recommended)

Close any open faces on the part before blade generation. Use SLD FAC REM or similar hole-closing commands to cap open regions:

• Ensures all sections produce clean, closed profiles
• Works with any blade position/orientation
• Most robust solution for production use

'*** Close holes in part before blade generation
sld fac rem none i_openFaceSet 0 0 0 1 0 0 i_ret

Option 2: Position Blades to Avoid Hollow Regions

If making the part watertight is not practical, ensure blade planes only intersect solid material:

• Position blades through walls, ribs, or solid features
• Avoid blade planes that pass through empty cavities
• Suitable for simple open parts with predictable geometry

Detecting Failures

If a blade cuts through hollow regions, the system may produce:

• Diagonal strip artifacts on the blade surface
• Incomplete cuts through the part
• Multiple overlapping cutout regions
• Unexpected sheet body counts in debug output

Summary of Requirements

3. Architecture & Workflow

High-Level Workflow

Coordinate Systems

The system uses two coordinate systems:

Transforms are stored in matrix variables:

• mi_FX_MATRIX_FORWARD - World → Local (for profile extraction)
• mi_FX_MATRIX_INVERSE - Local → World (for final positioning)

4. Orthogonal Blade Generation

Orthogonal blades have normals aligned with X, Y, or Z axes. These are the most common case.

Characteristics

• Normal vector: (1,0,0), (0,1,0), or (0,0,1)
• Front and back sections are identical
• Mosaic may produce degenerate output (handled automatically)
• No divergence corners
• Fastest processing path

Transform Method: Theta Rotation

For horizontal normals (Z component ≈ 0), uses simple theta rotation:

'*** Calculate rotation angle from normal
w_theta = atn2(w_normY w_normX)

'*** Forward transform: world -> local
set mi_FX_MATRIX_FORWARD
translate mi_FX_MATRIX_FORWARD x(-w_centerX) y(-w_centerY) z(-w_centerZ)
rotate mi_FX_MATRIX_FORWARD z(0-w_theta)
rotate mi_FX_MATRIX_FORWARD y-90

Degenerate Mosaic Handling

When front/back sections are identical, mosaic produces zero-area line segments instead of closed regions. The system detects this and falls back to using the largest original kurve:

'*** Check if mosaic produced valid kurves
i_mosaicResult = 0
if i_mosaicCount > 0 then
   for i_mosaicIdx = 0 to i_mosaicCount - 1
      get k(i_mosaicOutStart + i_mosaicIdx) D i_numSpans w_perim w_area
      if abs(w_area) > 0.0001 then
         i_mosaicResult = 1
      end if
   next
end if

5. Compound Angle Blade Generation

Compound angle blades have normals that aren't axis-aligned (e.g., 45° in XY plane, or arbitrary 3D angles).

Characteristics

• Normal vector has multiple non-zero components
• Front and back sections differ
• Mosaic produces valid combined regions
• Divergence corners occur at profile edges
• Requires full dual-section processing

Transform Method: Euler Angles

For general 3D normals (Z component ≠ 0), uses Euler angle decomposition:

'*** Calculate Euler angles
w_rotY = atn2(w_normX w_normZ)
w_xzMag = (w_normX*w_normX + w_normZ*w_normZ)@0.5
w_rotX = 0 - atn2(w_normY w_xzMag)

'*** Forward transform: world -> local
set mi_FX_MATRIX_FORWARD
translate mi_FX_MATRIX_FORWARD x(-w_centerX) y(-w_centerY) z(-w_centerZ)
rotate mi_FX_MATRIX_FORWARD x(0-w_rotX)
rotate mi_FX_MATRIX_FORWARD y(0-w_rotY)

Section Face Detection

After subtracting cutting sheets from part copies, finds section faces by:

1. Iterating all faces on new bodies
2. Checking face class = 4001 (planar)
3. Computing dot product of face normal with blade normal (must be > 0.90)
4. Checking distance from blade center (must be within halfThick + tolerance)

6. Divergence Corner Clearance

When front and back blade sections differ (compound angles), their profiles diverge at corners, creating sharp internal angles that could collide with the part.

Configuration Variables

Corner Detection Algorithm

'*** Scan kurve spans for acute corners
for i_spanIdx = 1 to i_spanCount
   '*** Get incoming and outgoing vectors
   '*** Calculate dot product (corner angle)
   w_dotCorner = w_vecInX * w_vecOutX + w_vecInY * w_vecOutY
   
   '*** Acute corner if dot < 0.866 (angle > 30° from straight)
   if w_dotCorner < 0.866 then
      '*** Store corner position and angle in VDM
      write $_scratch w_cornerX w_cornerY w_dotCorner
      vdm add i_cornerVDM i_cornerCount $_scratch 1
   end if
next

Angle-Based Radius Scaling

Sharper corners get larger cylinder radii:

'*** Base radius = 0.7 * half thickness
w_cornerRadius = w_halfThick * 0.7

'*** Scale for sharper corners (dot < 0.866)
if w_cornerDot < 0.866 then
   w_angleScale = 1.0 + 1.0 * (0.866 - w_cornerDot) / 1.866
   w_cornerRadius = w_cornerRadius * w_angleScale
end if

7. Global Variables Reference

Debug & Output Control

Profile Generation

Fouling Check

Internal State (Do Not Modify)

8. File Reference

Core Blade Generation

Support Utilities

Testing

9. Utility Macros

fxWindow - Window State Control

Controls graphics window updates for performance. Window updates are expensive during heavy geometry operations.

'*** Turn window off for batch operations
call fxWindow 0

'*** ... heavy geometry work ...

'*** Restore window
call fxWindow 1

'*** Check mode - verify expected state (debug)
call fxWindow -1 0 'callerMacroName'

fxPrintStatus - Formatted Output

Outputs timestamped messages with caller identification:

write $_FIXTURE_PERSISTENT_MESSAGE 'Processing blade 5 of 12...'
call fxPrintStatus 'fxMyMacro'

'*** Output: [timestamp] [fxMyMacro] Processing blade 5 of 12...

fxProgressPie - Visual Progress Indicator

Creates a pie-chart style progress indicator using 8 colored segments:

'*** Initialize
call fxProgressPie 0

'*** Show progress (1-8 segments)
call fxProgressPie 3   '*** 37.5% complete

'*** Cleanup when done
call fxProgressPie -1

10. Testing & Debug

Test Modes

The test macro fxTestCreateBlade.ovm supports 5 blade orientation modes:

Debug Levels

Set i_FX_DEBUG_LEVEL in fxGlobals.var:

Visual Debugging

Set i_FX_KEEP_CUTOUT_BODIES = 1 to preserve intermediate geometry:

• Profile sheets (green)
• Divergence cylinders (magenta)
• Cutout bodies on temp layer