Design for 3D-Printing

Original Article ↗ Hacker News Discussion ↗

Overall reception of the article

  • Widely praised as an unusually dense, experience-based guide that condenses years of trial-and-error into one resource.
  • Many experienced users say it matches techniques they learned the hard way and still taught them new tricks (e.g., “mouse ears,” layer-aligned bridges, teardrop holes).

CAD tools and workflows (especially on Linux)

  • Strong support for FreeCAD (especially since 1.0): powerful, scriptable, but still buggy with frustrating fillet/chamfer behavior and a learning curve. Tutorials and official docs are considered essential.
  • Onshape gets repeated praise for ease of use, browser-based access, collaboration, and a gentle parametric/constraints learning curve, but is criticized as a proprietary “walled garden.”
  • Fusion 360 is seen as extremely capable, especially for CAM, but people dislike licensing shifts, feature removals on the free tier, and cloud-based STL export. Not really available on Linux.
  • Other GUI CAD mentioned: SolveSpace (lightweight “Goldilocks”), Dune 3D (new, modern UI), Shapr3D, Plasticity, Tinkercad (great for absolute beginners).
  • Strong sentiment against long‑term lock‑in: several argue it’s safer to invest in FreeCAD or other FOSS tools despite rough edges.

Code-driven and hybrid CAD

  • OpenSCAD is repeatedly praised for programmers: simple syntax, robust parametrics, powerful primitives like hull().
  • Build123d, CadQuery, RepliCAD, “OpenPythonSCAD”/pythonscad are noted as more “pythonic” or extensible successors.
  • Some use Blender with CAD add‑ons, but many warn it’s ill-suited for precise mechanical parts versus BREP-based CAD.

Design-for-manufacturing and “production-aware” CAD

  • Commenters like how the article embodies Design for Manufacturing (DFM): designing to the strengths/limits of FDM.
  • People discuss the lack of true “production-aware” mechanical CAD that enforces process constraints (like PCB DRC).
  • Fusion and others have partial tooling (draft analysis, moldability/millability checks), but mapping designs to real factories and cost is still viewed as human “art.”
  • Some are experimenting with toolpath- or machine-aware modeling libraries that only allow operations a given process/tool can actually do.

3D printers: “just works” vs tinkering, and open vs closed

  • Bambu machines are repeatedly described as a watershed: fast, very low‑tuning, and motivating people to print and learn CAD far more than with older “Ender‑class” printers. AMS is appreciated even for single‑color jobs (auto spool switching), but waste and complexity draw criticism.
  • Significant pushback on Bambu’s GPL behavior, closed firmware, mandatory/creeping cloud features, closed filament RFID, and attempts to constrain forks of its slicer. Some fear this normalizes proprietary ecosystems in a historically open community.
  • Prusa is the preferred alternative for many: open ethos, repairable/upgradable hardware, reliable “workhorse” behavior (MK3/MK4/XL/Core One), though some say the company is falling behind or slow on some firmware issues.
  • Ender‑type cheap printers are seen as good for tinkerers but often frustrating for users who “just want to print,” driving them toward Prusa/Bambu/Raise3D/etc.
  • A recurring distinction appears: “3D printing hobby” (tinkering with the machine) vs “3D printer hobby” (using it as a tool to make things).

Techniques and mechanical tricks beyond the article

  • Strong agreement with “divide and conquer”: split large parts into oriented sub-parts joined by screws, pins, zip‑ties, etc. This often improves strength, print reliability, repairability, and even shock absorption.
  • Multiple threading strategies:
    • Small machine screws or wood/plastic-cutting screws self‑tap into undersized holes for low‑cycle joints.
    • Tricks for heat‑set inserts to keep back-side holes clear (install with a screw in place).
    • “Friction heat‑set threads” by driving an undersized pilot with a drill to melt plastic around the screw.
  • Bed adhesion and strength tips: ABS “juice” (ABS dissolved in acetone) for ABS adhesion; printing 100% infill then baking in salt to reduce layer lines and approach molded‑like strength (with some skepticism).
  • Structural/hybrid ideas: printing shells and filling with resin/foam/concrete; printed molds for silicone or forged carbon fiber; use of TPU for flexible joints/straps; igus-style triboplastics for low-friction bearings.
  • Compliant mechanisms and geometry (e.g., built‑in flexures) are highlighted as a natural fit for 3D printing.

Broader manufacturing context: scalability and processes

  • Some express disappointment that 3D printing didn’t become a universal “multi-widget machine.” Others explain why:
    • Injection molding and blow-molding remain vastly faster and cheaper at volume.
    • For strong, high-tolerance metal or engineering parts at scale, traditional machining still dominates.
  • 3D print farms and service bureaus do serve low- to medium-volume, geometry‑complex parts; once volume or simplicity cross thresholds, injection molding or CNC becomes economical.
  • For ABS in small volume (tens of kg/day), one commenter shares practice-based rules: heated enclosure (~50–80°C), quality/dried filament, aggressive fume handling, flat beds, and strong adhesives. Debate appears around whether such throughput should already push toward molding.

FDM vs resin (SLA/MSLA) considerations

  • Several ask how the article’s FDM advice maps to resin printers. Experienced users respond:
    • Resin print time depends almost entirely on Z-height; printing one part vs a full plate costs about the same time.
    • Supports “pull” parts off the vat film; orientation is chosen to manage peel forces and cross‑section area per layer, not sagging.
    • Parts are essentially 100% solid or hollowed (no traditional infill); hollow parts need drain/vent holes.
    • Resin prints are often brittle, warp at larger sizes, and require messy wash/cure steps; small dimensions are accurate but big parts distort.
    • For many mechanical/functional uses, hobby-grade resin is considered inferior in toughness to decent FDM; some prefer outsourcing resin to pro services.

LLMs and CAD / modeling

  • There is clear interest in LLM-assisted 3D modeling: as parametric OpenSCAD “coders,” as command generators for tools like Rhino, or as agents driving CAD UIs. Some report promising productivity boosts for boilerplate geometry and beginner onboarding.
  • Others are skeptical about deeper integration with parametric mechanical CAD:
    • Most real-world CAD is feature-tree/constraint-driven with heavy interdependencies; changing one feature often demands global redesign.
    • Describing precise constraints (dimensions, offsets, specific edges) in natural language can be slower than just modeling.
    • Available training data for true parametric, constraint‑rich CAD is sparse compared to polygonal assets.
  • Consensus: good for roughing out simple or hobby parts, teaching concepts, or generating OpenSCAD prototypes; far from replacing skilled mechanical design.

Miscellaneous insights

  • Rules of thumb: most filaments handle ~45° overhangs safely; better materials/ tuning can push further.
  • Several users emphasize learning just three core CAD ideas (sketch → constrain → extrude) to unlock basic functional designs.
  • There’s appreciation that slicers and high-speed printers (CoreXY, input shaping, better presets) now enable closer-to “click and print,” but multiple commenters stress that understanding design-for-printing, not just hardware, is what really unlocks strong, reliable parts.