3D Printing

A hands-on guide to desktop 3D printing (FDM and resin). Learn the workflow from CAD to slicer to print, key settings (layer height, infill, walls, temperature, speed), materials, tolerances, G-code basics, estimating time and cost, and troubleshooting.

Desktop 3D printers have put rapid prototyping on every engineer's desk. In a few hours you can hold a fixture, enclosure, jig or prototype part you designed that morning.

Getting good prints depends on understanding the slicer settings and designing parts that suit the process.

An analogy

An FDM printer is a very precise, computer-controlled hot-glue gun that draws a part one thin layer at a time.

Workflow

Design in CAD → export STL/3MF → slice (Cura, PrusaSlicer, Bambu Studio, OrcaSlicer) into layers and G-code → print → remove supports → finish. Resin (SLA/MSLA) printers need washing in IPA and UV post-curing.

Key slicer settings

These have the biggest effect on strength, time and quality.

• Layer height: 0.1 mm fine, 0.2 mm standard, 0.28+ draft (≤ 75 % of nozzle size).
• Walls/perimeters: 2–4; strength comes mostly from walls, not infill.
• Infill: 10–20 % for prototypes, 40 %+ for functional parts; gyroid is strong in all directions.
• Temperature: PLA 190–220 °C, PETG 230–250 °C, ABS/ASA 240–260 °C with enclosure.
• Supports & brims: for overhangs > 45° and warping-prone parts.

Materials

PLA: easy, stiff, low heat resistance (≈ 55 °C). PETG: tougher, chemical-resistant. ABS/ASA: heat-resistant, needs enclosure (ASA is UV-stable). TPU: flexible. Nylon & CF-filled: strong engineering parts, need drying. Resins: fine detail; engineering resins mimic ABS, PP or high-temperature materials.

Design rules

Clearance for fits ≈ 0.2–0.3 mm; holes print slightly small (drill or ream to size). Avoid unsupported overhangs; use chamfers instead of fillets on down-facing edges. Parts are weakest between layers (Z) — orient so loads run along layers. Use heat-set inserts for threads.

Tuning and troubleshooting

Calibrate e-steps/flow, pressure advance and input shaping for speed and sharp corners. Common problems: warping (bed adhesion, enclosure, brim), stringing (retraction, temperature, wet filament), layer shifts (belt tension, speed), under-extrusion (clog, too-high flow demand — hotends max out around 10–25 mm³/s), elephant's foot (first-layer squish).

Formulas

• Volumetric flow: Q = w · t · v
• Print time (rough): time ≈ printed volume / Q (+ travel, ~10–30 %)
• Filament mass: m = ρ · V_printed
• Filament length: L = V / (π d²/4) (d = 1.75 mm)

Worked example: Estimate time and filament

Given: Printed volume 40 cm³ (walls + infill); 0.45 mm line, 0.2 mm layer, 60 mm/s; PLA 1.24 g/cm³, 25 per kg

Find: Time, mass, cost.

• Q = 0.45 × 0.2 × 60 = 5.4 mm³/s
• t = 40 000/5.4 = 7407 s ≈ 2.1 h (+ travel ≈ 2.5 h)
• m = 40 × 1.24 = 49.6 g → cost ≈ 1.24

Answer: ≈ 2–2.5 h, ≈ 50 g, ≈ 1.24 in filament

Worked example: Filament length

Given: 49.6 g PLA, 1.75 mm filament

Find: Length used.

• V = 40 000 mm³; A = π/4 × 1.75² = 2.405 mm²
• L = 40 000/2.405 = 16.6 m

Answer: ≈ 16.6 m

Typical FDM start G-code (Marlin firmware)

M140 S60        ; set bed to 60 °C (PLA)
M104 S210       ; set nozzle to 210 °C
G28             ; home all axes
M190 S60        ; wait for bed
M109 S210       ; wait for nozzle
G29             ; auto bed levelling (if probe fitted)
G92 E0          ; reset extruder position
G1 Z0.3 F3000   ; move to first-layer height
G1 X10 Y20 F5000
G1 X10 Y150 E15 F1500   ; prime line: extrude 15 mm of filament
G92 E0
; ...slicer-generated layers follow...
M107            ; fan off at end
M104 S0         ; nozzle heater off
M140 S0         ; bed heater off
M84             ; disable motors

G1 moves with extrusion (E), M104/M109 set/wait nozzle temperature, M140/M190 set/wait bed, G28 homes, G29 levels, G92 resets the extruder position.

Common mistakes

• Wrong: Relying on 100 % infill for strength. — Right: Add walls/perimeters and orient the part; walls carry most load.
• Wrong: Designing exact-size holes and pegs. — Right: Allow 0.2–0.3 mm clearance and test with calibration prints.

Applications

• Prototyping: Form, fit and function checks within hours.
• Jigs & fixtures: Assembly aids, drill guides, soft jaws and gauges on the shop floor.
• Low-volume parts: Enclosures, spare parts, drone frames, custom brackets.

Key takeaways

• CAD → slicer → G-code → print → finish.
• Walls > infill for strength; orient for loads.
• Pick material by temperature and toughness.
• Estimate time from volume / (w·t·v).

Going further

• Input shaping & pressure advance: Klipper-style firmware cancels frame resonances and pressure lag, allowing 200–500 mm/s with sharp corners.
• Annealing: Heat-treating PLA/nylon parts increases crystallinity and heat resistance (with some shrinkage).
• Continuous-fibre printing: Printers laying carbon/Kevlar fibre make parts with aluminium-like stiffness.