Fab Lab Rwanda · Group work
Computer-Controlled Cutting
Our group workflow covers laser safety, focus, cutting settings, kerf and joint clearance. The test method below keeps material measurements separate from machine settings, so another group can repeat the characterization.
Safety and setup
We will start with the lab's machine-specific safety induction and an approved material. The operator should identify the stop control and fire response procedure before enabling the laser. Extraction, air assist, focus and material flatness must follow the machine instructions. Cutting requires continuous supervision.
The setup record should identify the laser model, lens, material and measured thickness, software, units and focus method. A percentage in one controller is not a transferable cutting recipe for another machine.
Focus and cutting settings
Our test sequence is to establish focus first, then cut a labelled speed/power matrix within the lab's approved range. We will hold the material, focus, number of passes and other parameters constant while comparing cells. If the controller exposes pulse frequency or rate, that setting belongs with each run.
| Test | What we compare | How we judge it |
|---|---|---|
| Focus | A small range around the prescribed focal position | Cut width, continuity and penetration |
| Speed and power | Labelled combinations on the same stock | Whether the part separates, edge quality and charring |
| Rate and passes | Controller units and number of passes | Consistent penetration without excessive edge damage |
We will choose settings from the actual cut pieces, then repeat the selected cell before using it for the joint tests.
Measuring kerf
Kerf is the width removed by the cut. One repeatable method uses a square plug and its matching opening from the same closed toolpath, with compensation disabled. For a nominal path width D, the opening is approximately D + k and the plug D − k. This gives k = (opening width − plug width) / 2.
We will measure both axes at several positions and repeat the cut. The calculation assumes the matching edges come from the same path; a multi-strip test needs its own count of the material-removing cuts. The original drawing, raw measurements and compensation setting belong together.
Joint clearance and reusable design rules
Our comb test will vary slot width around the measured sheet thickness. For an uncompensated slot, the physical opening is approximately its drawn width plus the kerf, but material compression and edge taper also affect the fit. We will compare loose, sliding and press fits rather than select a slot from the formula alone.
Different joint forms should be tested with the same stock and cut settings. We will compare insertion force, retention, ease of disassembly and damage after repeated assembly. The final design rule should state which material, thickness and joint geometry it applies to.