Activity 001: CAM Programming β Profile & Pocket Toolpaths¶
Activity ID: U4M2-ACT-001 Duration: 45 minutes Objective: Students will create a complete CAM program for a simple part featuring both profile and pocket toolpaths, simulate the result, and generate G-code. Group Size: 2 students (one computer per pair)
Overview¶
Students will import a provided DXF design into CAM software and program all operations needed to cut a nameplate with a rectangular pocket and rounded profile outline. This hands-on exercise covers tool selection, parameter entry, simulation verification, and G-code output.
Materials & Equipment Needed¶
- Computer with CAM software (Fusion 360 CAM, VCarve Pro, or Carbide Create)
- Provided DXF file: "nameplate_exercise.dxf" (8" Γ 3" rectangle with 6" Γ 1.5" inner pocket, 0.25" corner radii)
- Feed/speed reference chart (from U4M2-Material-001)
- Calculator
- Material specification: ΒΎ" Baltic birch plywood
- Tool: ΒΌ" 2-flute upcut spiral end mill
Instructions & Procedure¶
Phase 1: Setup & Import (10 minutes) 1. Open CAM software and create a new project 2. Import the nameplate DXF file 3. Define the stock: 9" Γ 4" Γ 0.75" (allows margin around the part) 4. Set the origin to the front-left corner of the stock, Z zero at the top surface 5. Select the post processor matching the lab's CNC controller (GRBL, Mach3, etc.)
Phase 2: Pocket Toolpath Programming (15 minutes) 1. Select the inner rectangle geometry (6" Γ 1.5" pocket) 2. Create a pocket/area clearing toolpath 3. Configure tool: ΒΌ" 2-flute upcut spiral, ER20 collet 4. Calculate and enter parameters: - Spindle speed: 18,000 RPM - Feed rate: Calculate using chip load 0.004" β Feed = 0.004 Γ 18,000 Γ 2 = 144 IPM - Plunge rate: 30 IPM (approximately 20% of feed rate) - Stepdown: 0.125" (50% of tool diameter) - Stepover: 0.10" (40% of tool diameter) - Pocket depth: 0.25" (2 passes at 0.125") 5. Select clearing strategy: offset/spiral pattern 6. Verify the toolpath preview shows correct geometry
Phase 3: Profile Toolpath Programming (10 minutes) 1. Select the outer rectangle geometry (8" Γ 3" outline) 2. Create a profile/contour toolpath β set to OUTSIDE compensation 3. Use the same tool and speed/feed parameters 4. Configure for through-cut: total depth = 0.78" (0.75" material + 0.03" into spoilboard) 5. Stepdown: 0.125" per pass (7 passes) 6. Add tabs: 4 tabs, one per side, 0.20" wide Γ 0.06" tall 7. Add lead-in: 0.25" arc lead-in on the scrap side 8. Set cutting direction: climb milling
Phase 4: Simulation & G-code Export (10 minutes) 1. Run the toolpath simulation β watch for: - Collisions with clamps (none in this exercise, but check habit) - Correct pocket depth (0.25") - Through-cut on profile with tabs remaining - No air-cutting or redundant movements 2. Verify estimated cycle time is reasonable (should be approximately 8-15 minutes) 3. Export G-code using the correct post processor 4. Open the G-code file in a text editor and identify: G0 rapid moves, G1 feed moves, spindle start (M3), and program end (M2 or M30)
Discussion Points¶
- What would happen if you used INSIDE compensation on the outer profile instead of OUTSIDE?
- Why is the plunge rate set much lower than the feed rate?
- How would you modify this program for acrylic instead of plywood?
- What is the purpose of cutting 0.03" below the material bottom?
Expected Outcomes¶
- Students produce a working G-code file ready to run on the lab's CNC router
- Students can explain each parameter selection with technical justification
- Students can interpret toolpath simulation results to verify correctness
Assessment Rubric¶
| Criteria | Excellent (4) | Proficient (3) | Developing (2) | Beginning (1) |
|---|---|---|---|---|
| Parameter Calculation | All speeds/feeds calculated correctly with justification | Correct values with minor calculation errors | Values entered but not calculated | Values guessed or defaults used |
| Toolpath Setup | All operations correctly configured, optimized order | Operations correct with minor setup issues | Operations present but with errors | Cannot create basic toolpaths |
| Simulation Verification | Identifies and resolves all issues in simulation | Runs simulation and catches major issues | Runs simulation but misses issues | Does not simulate |
| G-code Understanding | Can identify and explain G-code structure | Identifies major G-code elements | Limited G-code understanding | Cannot interpret G-code |
Safety Considerations¶
- This is a computer-based activity β no machine operation
- If time permits and instructor approves, the G-code may be run on the actual machine in a subsequent session
- Remind students that simulation does NOT verify workholding β that is a physical setup concern
Last Updated: 2026-03-19