The short answer
A 3D-printed prototype needs redesign for injection moulding because printing builds parts layer by layer with almost no geometric limits, while moulding forces molten plastic into a steel or aluminium cavity that must fill evenly, cool evenly and release cleanly. To Be Named Labs designs enclosures to moulding rules from the first print, so the move to tooling stays a step, not a rebuild.
Founders often hear "the CAD is done" after a great-looking printed enclosure. Then a toolmaker returns the file with a list of problems. That's not the toolmaker being difficult. Moulding physics simply differs from printing physics.
| 3D printing | Injection moulding | |
|---|---|---|
| How it forms parts | Adds material layer by layer | Injects molten plastic into a closed cavity |
| Geometry limits | Very few | Many — the part must fill and eject |
| Cost driver | Part volume and print time | Tool complexity, then cycle time |
| Cost per part at volume | Stays high | Drops sharply |
| Change cost | Reprint | Modify or remake the tool |
Printers handle thick and thin sections side by side. Moulds don't. Thick sections cool slower, shrink more, and pull the surface inward, creating sink marks and warping. Keep walls uniform — for many common plastics like ABS and PC, walls typically land in the 1.5 to 3 mm range — and transition gradually where thickness must change.
Printed walls can be perfectly vertical. Moulded walls need a slight taper, called draft, so the part slides out of the tool. One to two degrees is a common starting point. Textured surfaces need more, because texture grips the steel.
Any feature that would hook the part inside the mould — side holes, internal clips, overhangs — is an undercut. Each one needs a side action, lifter or collapsible core in the tool, which adds cost and complexity. Redesign them away where possible, or move them to the parting direction.
Printed parts often get stiffness from thickness. Moulded parts get it from ribs. A rule of thumb: rib thickness around half to two-thirds of the adjoining wall, so ribs don't cause sink on the visible surface.
Screw bosses need to connect to walls with ribs, have a core so they're not solid, and match the screw type. Self-tapping screws in plastic have specific hole sizes. A printed boss that held a screw fine may crack or strip in a moulded part.
Printed snap fits are often too thick, too short or too brittle in their printed form. Moulded snaps must flex within the material's strain limit and release from the tool. Expect to redesign every snap.
The mould splits along a parting line, leaving a faint seam. The plastic enters through a gate, leaving a small mark. Both should sit where users don't look. That's an industrial design decision, not just a tooling one.
Plastics shrink as they cool — by different amounts depending on material and geometry. Toolmakers compensate, but mating parts, snap fits and button gaps must be designed with realistic tolerances. A printed fit that felt perfect may bind or rattle in moulded parts.
Printing materials — PLA, PETG, resin, printed nylon — rarely match production plastics. A part that felt strong in printed nylon may behave differently in ABS. Choose the production material early, then test with the closest prototype process: CNC machining in the real material, or vacuum casting in a similar resin.
Between printing and steel tooling, you have options:
These let you validate moulding geometry before committing to the expensive tool.
We model printed prototypes with production rules from the start: uniform walls, draft, ribs, cored bosses, realistic snap fits. The printer doesn't need them. The toolmaker does. That way, the CAD that passes your looks-like review is already close to the CAD the toolmaker quotes.
Our hydroponics system enclosure needed to handle water, humidity and regular handling by venue staff. That pushed material and sealing decisions early — gasket grooves, wall sections, fastener access — so the jump to production processes didn't reopen the design.
Rarely as-is. Most printed designs need changes to wall thickness, draft, undercuts, ribs, bosses and snap fits before tooling.
A slight taper on vertical walls — often one to two degrees — so the part releases from the mould without dragging or sticking.
Thick sections cool and shrink more than thin ones, pulling the surface inward. Uniform walls and properly sized ribs prevent it.
For a few hundred to a few thousand parts, often yes. It costs less and arrives faster than steel, though it wears sooner.
Send us the one-line version of your product. We'll come back with a technical read: the hard parts, what to cut for v1, and a realistic path from prototype to field.
Consumer electronics architects. End-to-end.