Assignment: Computer-Controlled Machining

Individual assignment

• make (design+mill+assemble) something big (~meter-scale)
• extra credit: don't use fasteners or glue
• extra credit: include curved surfaces

Introduction

For this week’s assignment on Computer-Controlled Machining, I chose to design and fabricate an African Birth Chair. I selected this project because it combines cultural significance with practical functionality. The chair is traditionally used during childbirth, symbolizing support and strength. I wanted to explore large-scale CNC machining while also creating a meaningful and usable object that reflects craftsmanship and tradition.

Step 1 - Initial Base Design:

Started with a basic vertical rectangle in CorelDRAW, forming the foundation of the chair's side panel.

Step 2 - Corner Trimming Setup:

Placed triangle shapes at the top corners to trim the edges and add a stylized chamfer effect to the backrest.

Step 3 - Applying the Trim Tool:

Used CorelDRAW’s Trim feature to cut the corner triangles from the main rectangle, shaping the backrest profile.

Step 4 - Slot Rectangle Design:

Inserted a small green rectangle to act as the seating slot in the side panel of the chair for fitting the seat.

Step 5 - Full Part Layout:

Duplicated the design and created additional parts including connectors, seat pieces, and support columns.

Step 6 - Final Fitment & Alignment:

Refined the alignment and spacing of the components. The green parts represent slot-fillers and connectors.

Step 7 - Importing Elephant Artwork:

Imported an elephant head image for engraving. This graphic symbolizes strength and cultural roots.

Step 8 - Tracing Bitmap to Vector:

Used the ‘Outline Trace > Detailed Logo’ feature to convert the bitmap image into editable vector lines.

Step 9 - PowerTRACE Cleanup:

Adjusted detail, smoothing, and background removal settings to generate clean vectors from the image.

Step 10 - Final Vector Placement:

Placed the traced elephant head vector onto the backrest. This engraving became the centerpiece of the chair.

Step 11 - Export to DXF for ArtCAM:

Exported the entire layout as a DXF file with millimeter units to be imported into ArtCAM for toolpath creation.

Step 12 - ArtCAM Setup:

Initialized the ArtCAM interface and loaded the DXF layout for 2D and engraving toolpath operations.

Step 13 - Tool Selection & Parameters:

Selected a 6mm Ball Nose tool with defined stepdown, stepover, and feedrate for both cut and engraving paths.

Step 14 - Saving Profile Toolpath:

Generated and saved the profile cutting path using inside cut method and enabled lead-in/out moves.

Step 15 - Toolpath Preview in ArtCAM:

Previewed the full toolpath outline including the profile cut and the position of the engraved elephant vector.

Step 16 - Saving Engraving Path:

Saved a separate G-code toolpath for the elephant head engraving using the same 6mm Ball Nose bit.

Step 17 - CNC Milled Components:

Cut plywood parts ready after CNC milling. This includes the backrest, base, seat, and support elements.

Step 18 - Fully Assembled Chair:

Assembled the African Birth Chair with a slot-fit design. The engraved elephant head adds cultural depth.

Step 19 - User Testing:

The final chair was successfully tested by sitting. It proved to be structurally sound and comfortable.