Mold Box Generator

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STL, OBJ, or GLB — generates a split mold box for silicone casting

Mold Box Settings

Wall Thickness 5 mm

Clearance (Gap) 1 mm

Base Thickness 4 mm

Split Plane

Split Position 50%

Split Axis

Mold Features

Alignment Keys (Pegs & Sockets)

Key Diameter 6 mm

Key Height 4 mm

Pour Spout

Spout Diameter 10 mm

Air Vents

Vent Diameter 3 mm

View

Transparent Mold Walls

Output

Model Bounding Box—

Mold Outer Dims—

Silicone Volume (est.)—

Split Height—

Mold Pieces—

Printing Tips

Print mold halves with the flat split face down on the bed
Layer height: 0.12 – 0.2 mm for smooth cavity walls
Infill: 30–50% (walls must be rigid)
Spray mold halves with mold release before pouring silicone
Clamp or rubber-band the halves together tightly when pouring
Use alignment keys to register the halves precisely

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Free Online Mold Box Generator — Silicone Mold Casting Tool

Upload any 3D model and automatically generate a split mold box for silicone or resin casting. Set wall thickness, split position, alignment keys, pour spout, and vent channels. Preview the assembled or exploded mold in 3D and export each half as a print-ready STL. 100% browser-based — no signup, no install, no server upload.

What Is a Mold Box?

A mold box (also called a mold frame or formwork) is a rigid container that you place your master model inside and then pour silicone or resin around it. Once cured, you remove the master to reveal a cavity that replicates the model's shape exactly. Split mold boxes open into two or more pieces for easy demolding.

How This Tool Works

Import an STL, OBJ, or GLB model. The tool calculates the bounding box plus clearance, generates outer walls of configurable thickness, and splits the box along a customizable plane. It adds alignment keys (pegs and sockets) so the halves register precisely, a pour spout for silicone entry, and vent channels for air escape. Export each half as a separate STL for 3D printing.

Why 3D Print Your Mold Box?

3D printing mold boxes gives you exact, repeatable geometry that conforms closely to your model. This saves significant silicone compared to oversized rectangular molds. You can adjust wall thickness, clearance, and features per project. PLA, PETG, and ABS all work well for mold boxes — just apply mold release spray before pouring.

Moldboxer Alternative

Moldboxer is a paid desktop application for automatic mold system generation. This free browser-based tool provides the core functionality — split mold box generation with alignment keys, pour spout, and vents — without any install or subscription. Perfect for makers, hobbyists, and small-batch production.

Frequently Asked Questions

Is this a free Moldboxer alternative?

Yes. This tool provides core mold box generation entirely free in your browser. No signup, no watermarks, no limits. Your models never leave your device — all processing happens locally using WebAssembly.

What file formats are supported?

STL, OBJ, GLB, and GLTF. These cover the vast majority of 3D printable models. The tool auto-centers and scales models for mold generation.

What silicone should I use?

Platinum-cure (addition-cure) silicones like Smooth-On Mold Star or Sorta Clear are popular choices. Shore hardness 15A–30A works well for most demolding. Tin-cure silicones are cheaper but have shorter mold life.

How do I calculate how much silicone I need?

The tool estimates the silicone volume by calculating the mold cavity volume minus the model volume. Pour 10-15% extra to account for spillage and material left in mixing containers.

Do I need mold release?

Yes. Spray your 3D printed mold box and master model with mold release (e.g., Mann Ease Release 200) before pouring silicone. This prevents the silicone from bonding to the printed plastic and ensures clean demolding.

Need a custom master model for molding?

PrintPal AI generates fully custom 3D models from text descriptions or images.

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