Field GuideRules of Thumb
Maker rules of thumb
The starting numbers and design moves worth memorising — for 3D printing and laser work, especially for making laser cut boxes. Every rule is a tested starting point, credited to the maker it came from. Pick a discipline.
3D Printing
12 rules · 6 topics
3D Modeling / DFM · Supports & Overhangs · Tolerances & Fit · Joining & Assembly · Printing & First Layer · Mechanisms & Hinges
Laser Cutting & Engraving
8 rules · 4 topics
Safety & Materials · Dialing In Settings · Maintenance & Alignment · Setup & Workflow
3D Printing
Wall thicknessStart FDM walls at 2–3 extrusion widths — with a 0.4 mm nozzle, that’s about 0.8–1.2 mm.Tabs & overhangsReplace a flat overhanging tab with a chamfer that runs from the part body down to the feature, and round every corner so material flows into it.Holes & boresAdd a small fillet around a hole’s edges, orient horizontal holes as teardrops to stop sagging, and size the hole up a hair because prints shrink.Walls vs. infillAdd perimeters (walls) before you raise infill; a standard grid or triangle infill around 25% is the reliable default, and infill choice mostly changes how the part fails, not how strong it is.HandlesReinforce the opening with a thickened rim, chamfer the overhang so it self-supports, and where a through-hole isn’t needed, use an indented grip instead so it prints with no support at all.Designed supportsIf a feature can’t be reoriented to self-support, add a thin modeled support (a wall or web) with a deliberate break-away contact instead of letting the slicer generate one.Build orientationReorient the part so its overhangs self-support before adding any support — often just rotating ~45° and chamfering the leading edge removes the need for support entirely, and gives cleaner edges all round.Pin tolerancesFillet the base of a pin so it doesn’t snap, funnel the top of the hole, and make the hole about a quarter of a millimetre larger than the pin.Print-in-place clearanceLeave a modeled gap between any two parts that must move or assemble — start around one nozzle width and open it until they run free.Joining featuresChamfer every tongue so layer lines wedge and lock, and prefer a flexing snap-in lock tab — it pulls the seam tight with no jiggle instead of relying on a friction fit.Designed raftsModel a thin raft plate into the part, spaced about one layer height below it, with filleted/rounded edges — so adhesion doesn’t depend on slicer settings you can’t control.Print-in-place mechanismsPrint a thin living hinge on its side so the flex runs across the layers, and where a part will flex many times, spread the stress over more material (a circular or slotted hinge) instead of one thin flap.
Laser Cutting & Engraving
Material safety & SDSNever laser an unknown or PVC/vinyl-containing material. Identify the material and read its Safety Data Sheet (SDS) before the first job.Speed / power testFor a new material, run a speed-vs-power test grid on a scrap of the real stock and read the best cell straight off the sheet.Max power in LightBurnSet your controller’s max S-value (e.g. $30 = 1000 in GRBL) to match LightBurn’s S-value max so 100% in software actually drives the laser at full power.Settings libraryRun one focused material test to find good settings, then save them as a named material profile — build a library so each material is dialed in once, not re-guessed every job.Galvo timing & delaysSet jump delays to a safe baseline, then tune Start TC and Laser Off TC on a hatched-square test card until the fill lines just meet the contour with no gap and no burn-in.Beam alignmentAlign the mirrors so the beam lands in the same spot at the near and far end of each axis — use a tape target and low power to walk it in.Machine maintenanceClean the lens and mirrors on a regular schedule and keep the rails and exhaust clear — a dirty lens quietly steals cutting power.Repeatable jigsCut a locating jig on the laser so each blank drops into the exact same position — then reuse the same file placement for every run.