VariCAD Sheet Metal Design: Bending, Unfolding, and Manufacturing Export

VariCAD Sheet Metal Design: Bending, Unfolding, and Manufacturing Export

VariCAD includes dedicated sheet metal design tools for creating bent sheet metal parts, calculating bend allowances, unfolding 3D models to flat patterns, and exporting to DXF for laser cutting and CNC punching. This guide covers the complete sheet metal workflow.

Sheet Metal Setup

Material Properties

Before creating sheet metal parts, define the material:

1. Tools > Sheet Metal > Material
2. Set:
   • Thickness: Sheet thickness (e.g., 1.5mm, 2.0mm, 3.0mm)
   • Bend radius: Minimum inside bend radius (typically 1× thickness)
   • K-factor: Bend allowance factor (0.3-0.5 typical, depends on material and method)
   • Bend deduction: Optional, if you use bend deduction instead of K-factor

K-Factor Reference

| Material | Thickness | K-factor | |----------|-----------|----------| | Soft aluminum | < 3mm | 0.33 | | Soft aluminum | 3-6mm | 0.38 | | Hard aluminum | < 3mm | 0.40 | | Steel | < 3mm | 0.42 | | Steel | 3-6mm | 0.44 | | Stainless steel | < 3mm | 0.44 | | Stainless steel | 3-6mm | 0.46 |

Creating Sheet Metal Parts

Method 1: Flange from Base

1. Create a base plate (extrude a rectangle to sheet thickness)
2. Tools > Sheet Metal > Add Flange
3. Select an edge of the base plate
4. Specify:
   • Flange length: Distance from bend to flange end
   • Bend angle: 90° for standard, or custom angle
   • Bend radius: Inside radius (uses material default or override)
   • Flange position: Inside, outside, or centered on edge
5. The flange is created with proper bend geometry

Method 2: Sketch-Based

1. Create a sketch of the unfolded flat pattern
2. Tools > Sheet Metal > Create from Sketch
3. Select the sketch
4. Specify bend lines (lines where bends will occur)
5. Specify bend angles for each bend line
6. VariCAD folds the flat pattern into 3D

Method 3: Convert Solid to Sheet Metal

1. Model a part as a regular solid (with uniform thickness)
2. Tools > Sheet Metal > Convert to Sheet Metal
3. Select the solid
4. VariCAD identifies bends and flanges
5. Verify the identified bends and adjust if needed

Editing Sheet Metal Parts

Modifying Flange Length

1. Right-click the flange in the feature tree
2. Edit > Flange Length
3. Enter new value
4. The flange updates

Changing Bend Angle

1. Right-click the bend in the feature tree
2. Edit > Bend Angle
3. Enter new angle
4. The flange rotates to the new angle

Adding Corner Relief

1. Tools > Sheet Metal > Corner Relief
2. Select the corner where two bends meet
3. Choose relief type:
   • Circular: Round cutout (most common)
   • Square: Square cutout
   • Tear: Slit without material removal
4. Specify relief size (typically 1× thickness to 2× thickness)

Adding Bend Relief

1. Tools > Sheet Metal > Bend Relief
2. Select the bend edge
3. Specify relief width and depth
4. The relief cut is added to prevent tearing during bending

Unfolding to Flat Pattern

Automatic Unfolding

1. Tools > Sheet Metal > Unfold
2. Select the sheet metal part
3. VariCAD calculates:
   • Bend allowance for each bend
   • Flat pattern dimensions
   • Bend lines on the flat pattern
4. The flat pattern is displayed

Verifying the Flat Pattern

Check the following on the unfolded pattern:

• Overall dimensions match expected flat size
• Bend lines are marked with centerlines
• Bend direction is indicated (up or down)
• Corner reliefs appear correctly
• Bend reliefs appear at bend edges

Exporting Flat Pattern

1. With the flat pattern displayed
2. File > Export > DXF
3. Set options:
   • Include bend lines: Yes (as separate layer or color)
   • Include text annotations: Yes (bend angles, direction)
   • Scale: 1:1 (essential for manufacturing)
4. The DXF file is ready for laser cutting or CNC punching

Bend Allowance Calculation

VariCAD calculates bend allowance using the formula:

BA = (π/180) × BendAngle × (InsideRadius + K-factor × Thickness)

Where:

• BA = Bend Allowance (length of material in the bend)
• BendAngle = Bend angle in degrees
• InsideRadius = Inside bend radius
• K-factor = Neutral axis position factor
• Thickness = Sheet thickness

The flat pattern length is:

FlatLength = Leg1 + Leg2 + BA

Common Sheet Metal Issues

Issue: Unfolded Pattern Is Wrong Size

Cause: Incorrect K-factor or bend radius. Fix: Verify K-factor matches your material and bending method. Adjust in Material settings and re-unfold.

Issue: Flange Intersects Adjacent Geometry

Cause: Flange length or angle causes collision. Fix: Use Interference Check (Tools > Assembly > Interference) to detect collisions. Reduce flange length or adjust bend angle.

Issue: Bend Lines Missing in DXF Export

Cause: Bend line layer not included in export. Fix: In DXF export options, ensure "Include bend lines" is checked. Check that bend lines are on a visible layer in the DXF file.

Issue: Corner Tears at Bend Intersection

Cause: No corner relief at bend intersection. Fix: Add corner relief at the intersection point. Use circular relief with size = 1.5× thickness.

Manufacturing Export Checklist

Before exporting for manufacturing, verify:

• [ ] Material thickness is correct
• [ ] Bend radius matches tooling availability
• [ ] K-factor is appropriate for material
• [ ] All corners have relief cuts
• [ ] All bends have bend relief
• [ ] Flat pattern dimensions are verified
• [ ] DXF export is at 1:1 scale
• [ ] Bend lines are on a separate layer
• [ ] Bend direction annotations are included
• [ ] No overlapping or duplicate lines in DXF

Manufacturing Export Best Practices

When exporting sheet metal flat patterns from VariCAD for laser cutting or CNC punching, follow these best practices to ensure clean manufacturing output. First, always verify the unfolded pattern is correct — check that bend lines are marked, the overall dimensions match the expected flat size, and there are no overlapping contours. Second, export to DXF format rather than DWG — most laser cutting and CNC punching machines read DXF files directly. Third, set the DXF version to R15 (2000) for maximum compatibility with manufacturing equipment. Fourth, ensure all geometry is on a single layer with color set to white or black — some laser cutting software interprets colors as cutting power levels. Fifth, remove all text, dimensions, and annotations from the export file — manufacturing machines only need the cutting contours. Sixth, set the drawing units to millimeters, as most manufacturing equipment expects metric units. Finally, if the part has internal cutouts, verify they are separate closed contours and not connected to the outer profile. Following these steps ensures the manufacturing shop can process your file without manual cleanup.

Conclusion

VariCAD's sheet metal tools cover the complete workflow from 3D design to flat pattern export. The automatic unfolding with K-factor-based bend allowance calculation produces accurate flat patterns for manufacturing. By properly configuring material properties, adding corner and bend reliefs, and exporting with bend line annotations, you can produce DXF files that go directly to laser cutting and CNC punching machines without additional processing.