Turn any STL into a 3D-printable mold
Upload a model, pick a parting axis, and download two watertight mold halves ready to print. Automatic undercut detection, alignment pins, sprue and vent channels — all in a single ZIP.
Print the mold in PLA, pour wax, soap, resin, or silicone, then release — every time. Part of the Creator Bundle.
What makers pour into Moldforge molds
A 3D-printed mold turns any STL into a repeatable casting. Here is what people pour most.
Candle Making
Pillar candles, tealights, and sculpted shapes. Print the mold in PLA, pour soy or paraffin wax at the correct temperature, pop out a repeatable artisan candle every time.
Soap & Bath Bombs
Melt-and-pour or cold-process soap moulds in heart, star, flower, or custom shapes. Food-safe PLA prints and lives happily in a soap studio for hundreds of cycles.
Resin Casting
Jewelry, miniatures, terrain pieces — pour casting resin into a rigid PLA mold or print a flexible TPU mold for complex geometry. The CSG pipeline handles heavy undercuts cleanly.
Product Prototyping
Quick silicone molds for small-batch manufacturing. Print the rigid outer shell in PLA, pour silicone into the cavity, then pull finished rubber parts from the silicone.
How It Works
From STL to printable mold halves in four steps — under four minutes of clicking.
Upload Your STL
Drop in any STL — a miniature, a figurine, a product prototype, a soap shape. The mesh is parsed entirely in your browser; nothing is uploaded to a server. Moldforge also ships a library of 22 built-in candle, soap, and resin shapes if you don't have an STL to start from.
- STL upload (binary or ASCII) parsed locally in your browser
- 22 built-in shapes: cylinders, pillars, hearts, stars, leaves, flowers…
- SVG revolve or extrude path — bring your own silhouette
- Bounding box, triangle count, and units shown immediately
Pick a Parting Axis
Choose the X, Y, or Z axis to split the mold. Drag the parting-plane slider to position the split, and live undercut analysis shows what percentage of the surface would snag on release. When over 25% is flagged, Moldforge suggests a different axis or flexible silicone.
- X / Y / Z axis toggle with live preview
- Parting-plane position slider (0–100%)
- Automatic undercut detection scores every axis
- Padding slider adds breathing room between part and cavity
Add Pins, Sprue, and Vents
Configure alignment pins (2, 3, or 4), sprue channel, and vent holes. Pick your pour material — paraffin, soy, beeswax, melt-and-pour soap, cold-process soap, or casting resin. Recommended draft angle is auto-selected per material.
- Alignment pins: 2 / 3 / 4 count, adjustable diameter
- Sprue channels: funnel, straight, or side-entry
- Vent holes prevent trapped air in the cavity
- Material-aware defaults: wax, soap, resin
Generate and Print
Click Generate molds. Moldforge runs a watertight CSG subtraction to carve your part out of a sized block, then splits it into a top and bottom half. Download both halves as a single ZIP and print them in PLA, PETG, or TPU (for flexible molds).
- Watertight binary STL output, slicer-ready
- Single ZIP with top and bottom halves
- Draft / standard / fine resolution presets
- No supports needed — the halves print flat
Features
Everything you need to go from a 3D model to a mold that releases cleanly on the first try.
Undercut Detection
Every parting-plane position is scored for release-safety. Faces that would hook on the mold wall get flagged with a percentage; the axis picker recommends the cleanest split automatically.
Watertight CSG Pipeline
Powered by three-bvh-csg — a BVH-accelerated boolean engine. The part is subtracted from a sized block, cleanly split in two, and written as valid manifold STL meshes that every slicer accepts.
Alignment Pins
2, 3, or 4 pins placed around the perimeter of the parting plane. Solid cylinders on the bottom half, matching blind pockets on the top. Pin diameter and position adjustable.
Sprue & Vents
Single-channel funnel, straight pour, or side-entry sprue. Optional 1.5 mm vent channels eject trapped air so the cavity fills completely. Hole radius auto-sized to slicer-safe minimums.
Built-in Shape Library
Don't have an STL? Pick from 22 procedural shapes — candle pillars, tealights, hearts, stars, leaves, flowers, seashells — and configure them with sliders. Revolved or extruded, your choice.
Material-Aware Defaults
Six pour materials with correct draft-angle defaults (2.0° resin → 4.0° cold-process soap) and cast weight / pour temperature hints. Pick your material, the rest is dialled in.
Why Generate Molds In-Browser?
Traditional mold-making services charge €50–300 per cavity and take weeks. CAD-based mold design costs months of Fusion / Solidworks learning. Moldforge gets you a printable mold in four clicks.
Order a Mold Online
- €50–300 per cavity
- 2–4 week lead time
- No undercut preview — pay and pray
- Revisions cost another order
Model in Fusion / Solidworks
- Weeks of CAD learning curve
- Manual parting line and pin placement
- No automated undercut detection
- Export, boolean, re-export loop
3DPlotter Moldforge
- €39.90 once — unlimited molds
- Four-click workflow, under four minutes
- Live undercut analysis before you generate
- STL never leaves your browser
What You Need
Everything required to generate, print, and cast from a Moldforge mold.
Hardware
- Any FDM or resin 3D printer
- PLA, PETG, or TPU filament (1.75 mm)
- Release agent: mold release spray, petroleum jelly, or silicone oil
- Optional: two-part silicone if you want a flexible cavity
Software
- 3DPlotter Creator Bundle (€39.90 one-time)
- Modern web browser (Chrome, Firefox, Safari, Edge)
- Any slicer (OrcaSlicer, Bambu Studio, Cura, PrusaSlicer)
- Optional: your favourite CAD tool for authoring STLs
Frequently Asked Questions
What file formats does Moldforge accept?
Binary and ASCII STL files (up to 50 MB), SVG silhouettes for revolved or extruded shapes, and 22 built-in parametric shapes. STL parsing is done entirely client-side — your geometry never leaves the browser.
What does the undercut report tell me?
The undercut report measures the percentage of surface area that would snag on release from the mold. Anything under 10% releases cleanly from rigid PLA/PETG molds. 10–30% still works with flexible TPU or silicone. Above 30%, try a different parting axis — the axis picker recommends the cleanest split automatically.
Can I print a two-part silicone mold?
Yes. Print the rigid outer shell in PLA, seal the seam with tape, pour two-part silicone (RTV, Smooth-On Mold Star, Ecoflex) into the cavity. When cured, split the shell open and remove the silicone — you now have a flexible production mold that handles undercuts PLA alone could not.
What materials can I pour into a printed mold?
Wax (paraffin, soy, beeswax), soap (melt-and-pour, cold-process), casting resin (epoxy, polyurethane, UV), silicone (as above), low-melt metals (bismuth/tin alloys with appropriate PLA+). Avoid zinc, aluminium, and anything above ~150 °C in PLA molds — use PETG or TPU for higher temps.
How do alignment pins work?
Moldforge adds solid cylindrical pins to the bottom half that seat into matching blind pockets in the top half. 2 pins for small moulds, 3 for asymmetric parts (prevents wrong reassembly), 4 for large rectangular moulds. All four corners of the parting plane sealed, no lateral wobble when you clamp the halves together.
Why is my generate button greyed out?
Usually one of: the uploaded STL is not manifold (holes in the surface, flipped normals), the parting plane sits outside the bounding box, or the part is larger than the configured block size. Re-export your STL from your CAD tool with "fix non-manifold" enabled, or increase the padding slider. The built-in shapes always generate; use them to validate your workflow first.
Does my STL upload leave my browser?
No. STL parsing, CSG boolean operations, and mesh export all run on your device using a pure-JavaScript pipeline (three.js + three-bvh-csg). Nothing is sent to a server. Only usage analytics (page views, feature clicks) reach 3DPlotter — never the geometry or the generated molds.
What 3D printer do I need?
Any FDM printer with a 0.4 mm nozzle works. For finer cavity detail (miniatures, jewelry), a 0.2 mm nozzle or a resin (SLA/DLP) printer is ideal. Print the mold halves flat on the parting-plane face — no supports required. Bambu Lab, Prusa, Creality, Elegoo, and most clones print Moldforge output perfectly.
Ready to Cast From a 3D-Printed Mold?
Get the Creator Bundle for €39.90 — includes Moldforge plus pen plotting, string art, wax seal, lithophane, and roll press tools. One-time purchase, lifetime access.