LOM, FDM, and SLA are additive manufacturing techniques, but they build objects differently: LOM bonds and cuts sheets, FDM deposits molten thermoplastic, and SLA cures liquid resin using ultraviolet light. This creates important differences in materials, accuracy, cost, and applications.
In each process, a three-dimensional CAD model is divided into thin digital layers by slicing software. The manufacturing system then produces those layers sequentially, allowing complex forms to be made without conventional tooling.
| Technique | Manufacturing mechanism | Main characteristics |
|---|---|---|
| Laminated object manufacturing (LOM) | Sheets of paper, polymer, or metal are bonded using heat, pressure, or adhesive. Each sheet is cut to the layer profile by a blade or laser. | Relatively fast and suitable for large models. Unused sheet material supports the object during manufacture, but material is wasted and fine detail may be limited. |
| Fused deposition modelling (FDM) | A heated nozzle melts and extrudes thermoplastic filament along a programmed path. The deposited material cools and solidifies layer by layer. | Affordable, accessible, and suitable for functional prototypes. However, layer lines are visible, accuracy is moderate, and support structures may be required. |
| Stereolithography (SLA) | An ultraviolet laser selectively cures a liquid photopolymer resin in a vat. The build platform moves after each layer is formed. | Produces high accuracy, fine details, and smooth surfaces. Resin and equipment can be expensive, and parts require washing, support removal, and ultraviolet post-curing. |
A common misconception is that all 3D printers melt solid plastic. Only FDM normally melts thermoplastic filament; SLA causes a chemical curing reaction in liquid resin, while LOM bonds and cuts solid sheets.
For A4.1 Manufacturing techniques (HL only), an examiner may ask you to compare processes or recommend one for a design context. Link the manufacturing mechanism to a justified consequence: choose SLA for a detailed presentation model, FDM for a low-cost functional prototype, or LOM for a relatively large form where very fine detail is unnecessary.