1. Lab Safety Training & Protocols

Before powering on our large-format CNC router, our group completed the mandatory lab safety induction. Because heavy-duty CNC systems present dynamic operational hazards (flying debris, high noise levels, powerful spindle torque, structural break risks), we follow a zero-compromise safety protocol:

• Personal Protective Equipment (PPE): Safety glasses must be worn continuously to block high-velocity chips. Ear protection (muffs or plugs) is non-negotiable due to high spindle decibels and dust extractor noise. No loose clothing, scarves, or hanging jewelry are permitted, and long hair must be strictly tied back.
• Emergency Controls (E-Stops): We mapped out the active physical Emergency Stop hit-buttons on both the main handheld operator pendant and the primary machine housing chassis.
• Machine Environment: Keep the safety boundaries entirely clear of loose debris. The blast gates and high-volume vacuum extraction unit must be verified as open and running before launching any files.
• Active Monitoring: Never leave an active machining file unattended. The operator must keep an eye on the toolpath vector, ready to hit pause or E-stop if structural lift, tracking errors, or localized burning smells occur.

2. Machine Characterization & Testing Matrix

To understand the cutting limitations and mechanical accuracies of our specific CNC installation, we executed a unified calibration diagnostic cut on a 19mm local plywood panel.

A. Runout Testing

Tool runout is the measure of how far a spinning tool rotates off its true theoretical axis of symmetry, which directly impacts slot tolerances. We took a precision dial test indicator and rotated the collet manually by hand. We noted a baseline static shaft deviation of less than 0.02 mm. Following a test pocket profile, measurements taken across the cut width using digital calipers revealed an effective dynamic cut width of 6.05 mm with our 6.00 mm bit. This leaves us with a dynamic runout delta of approximately 0.05 mm.

B. Axis Alignment & Squareness Tracking

We generated a clean 300 mm × 300 mm test profile square. After cutting, we evaluated both diagonal lengths ($D_1$ and $D_2$) using long-jaw micrometers to confirm the squareness of our Gantry tracking ($X$ to $Y$ perpendicular alignment):

• Diagonal $1$ ($X_0, Y_0$ to $X_{300}, Y_{300}$): 424.26 mm
• Diagonal $2$ ($X_0, Y_{300}$ to $X_{300}, Y_0$): 424.31 mm

The small difference of 0.05 mm confirms that the machine axes are squared correctly and tracking accurately.

C. Fixturing & Hold-Down Methods

We evaluated two primary methods for securing raw material sheets to the machine bed:

Fixturing Strategy	Observed Advantages	Observed Trade-Offs / Risks
Perimeter Edge Clamps	Fast to setup; leaves zero physical damage holes on stock faces.	Does not correct internal bowing in large sheets; risks collisions with the tool holder.
Direct Wood Screws (Spoilboard)	Secures interior dead-spaces perfectly flat; zero collision risk when planned correctly.	Leaves small puncture marks on stock; requires deliberate layout checking to avoid vectors.

Our Verdict: For large furniture parts and tight nest patterns, direct mechanical screw fixturing placed inside internal cutout waste areas provides the safest results and keeps the material completely flat.

3. Speeds, Feeds, and Toolpath Profiles

We computed our chip load settings using the standard machining formula:

Feed Rate (F) = RPM (N) × Number of Flutes (Z) × Chip Load (C)

Using a 6mm 2-Flute Upcut HSS Flat End Mill targeting a baseline chip load of 0.07 mm per tooth for local structural plywood panels, our parameters match the values below:

Parameter Name	Calculated/Tested Bounds	Selected Production Value	Operational Justification Notes
Spindle Speed (N)	16,000 - 20,000 RPM	18,000 RPM	Keeps tool torque high without generating excessive frictional heat on plywood layers.
Feed Rate (F)	2,000 - 2,800 mm/min	2,520 mm/min	Matches our 0.07mm chip load exactly ($18000 \times 2 \times 0.07$). Prevents wood burning.
Plunge Rate	600 - 1,000 mm/min	800 mm/min	Protects the bottom cutting edges of the mill from aggressive vertical loading stresses.
Max Pass Depth	2.0 mm - 4.0 mm	3.5 mm	Maintains a safe stepdown limit (~0.6 × tool diameter) to prevent bit deflection and breakage.

4. Verification Clearances (The Comb Joint Test)

Because nominal 19mm plywood panels often vary in thickness, we milled an interlocking test comb containing slot widths from 18.7 mm to 19.5 mm. We found that a slot configuration of exactly 19.15 mm provided a solid, rigid press-fit joinery connection across our stock sheet without causing splits.