DLP Printing in Jewellery Making
DLP Printing in Jewellery Making
Digital light processing and its role in modern jewellery fabrication
Digital light processing (DLP) printing is a vat photopolymerisation technology in which an ultraviolet projector flashes a complete cross-sectional image of each layer onto a bath of liquid photopolymer resin, curing the entire layer simultaneously rather than tracing it point by point. In jewellery production, DLP printers are used principally to produce highly detailed wax-substitute models in castable resin, which are then invested and cast by conventional lost-wax methods. The technology has become standard equipment in professional jewellery studios and trade casting houses worldwide, having substantially compressed the time between design and metal casting while enabling geometric complexity that hand-carving cannot reliably achieve.
Operating Principle
A DLP printer positions a build platform just above — or, in bottom-up configurations, just below — a shallow reservoir of liquid resin. A digital micromirror device (DMD) chip, the same technology used in digital cinema projectors, modulates a UV light source to project a precise bitmap image corresponding to one layer of the three-dimensional model. Exposure times per layer are typically one to ten seconds. The platform then advances by one layer thickness — commonly 25 to 50 microns in jewellery-grade machines — and the next layer is projected. Because the entire layer cures at once, build speed is largely independent of the complexity of the cross-section at any given height, a meaningful advantage over laser-based stereolithography (SLA), in which a focused beam must trace every feature sequentially.
The practical consequence for jewellery work is that a ring model requiring several hours in SLA may be completed in under an hour on a comparable DLP machine, and a full build plate carrying multiple models scales with almost no additional time penalty per piece. This throughput advantage has made DLP the dominant photopolymerisation format in trade casting environments.
Resolution and Surface Quality
The spatial resolution of a DLP print is governed by two independent parameters: the XY pixel pitch, determined by the projector's resolution and the size of the build area, and the Z-axis layer thickness. Entry-level jewellery DLP printers typically achieve XY pixel sizes of 50–75 microns; higher-end machines reach 35 microns or below. Layer thickness in jewellery applications is most commonly set between 25 and 50 microns, though some operators use 100-micron layers for speed on less detailed sections.
Because each layer is a discrete step, curved surfaces exhibit a characteristic staircase texture when examined under magnification. Post-print cleaning in isopropyl alcohol followed by a secondary UV cure partially consolidates surface geometry, but fine finishing — particularly on visible metal surfaces after casting — still requires hand polishing. Experienced casters note that DLP-printed models, when properly cleaned and cured, produce cast surfaces comparable in quality to those from traditional injection-wax models, and superior to many hand-carved waxes for fine engraving and milgrain details that are designed digitally.
Castable Resins
Standard photopolymer resins used in engineering or dental DLP printing are generally unsuitable for jewellery casting: they leave carbonaceous ash on burnout that contaminates the investment mould and produces porosity in the finished casting. Jewellery-specific castable resins are formulated to burn out cleanly at investment burnout temperatures (typically 730–760 °C), leaving minimal residue. Leading resin suppliers for the jewellery trade include Formlabs (Castable Wax resin series), Asiga (PlasGRAY and DEF resins), and Envisiontec (now Etec), whose machines and companion resins were among the earliest adopted by trade casting houses.
Wax-filled castable resins — hybrid formulations containing a significant proportion of actual wax dispersed in the photopolymer matrix — have gained considerable acceptance because their burnout behaviour more closely mimics injection wax, reducing the need to modify established investment and burnout schedules. These resins are slightly more brittle in the green (uncured) state and require careful handling, but they are now the preferred choice for high-volume casting operations.
Workflow Integration
The DLP printing workflow in jewellery begins with a three-dimensional CAD model, most commonly produced in dedicated jewellery design software such as Rhino 3D with RhinoGold or Matrix, or in parametric tools such as Fusion 360. The model is exported as an STL or OBJ file, imported into the printer's slicing software, oriented on the build platform, and supported with fine breakaway structures that hold the model during printing and are removed afterwards. Support placement is a skilled task: poorly placed supports leave witness marks on visible surfaces that must be polished away after casting, while insufficient support causes layer delamination or print failure.
After printing, models are rinsed in isopropyl alcohol to remove uncured resin, post-cured under a broad-spectrum UV lamp, and inspected under magnification before spruing. They are then invested, burned out, and cast by standard lost-wax procedures. The resulting metal casting is finished by conventional bench methods. The printed resin model is consumed in the process, exactly as a wax model would be, so digital files serve as the permanent record from which additional models can be reprinted on demand.
DLP versus SLA and Other Additive Technologies
SLA (stereolithography) printers use a laser to cure resin point by point and can achieve very fine feature resolution, but their layer-by-layer laser tracing makes them slower than DLP for typical jewellery geometries. MSLA (masked SLA, sometimes called LCD printing) uses a monochrome LCD panel as a pixel mask in place of the DMD chip and has become competitive with DLP at lower price points, though the LCD panel degrades over time and requires periodic replacement.
Fused deposition modelling (FDM) printers, which extrude thermoplastic filament, are rarely used for fine jewellery models because their layer resolution (typically 100–200 microns minimum) and surface texture are insufficient for the detail required. Wax inkjet printing — used in machines such as the Solidscape series — deposits actual wax droplets and produces excellent castable models, but build speeds are slow and machine costs are high; DLP has largely displaced wax inkjet in new studio installations, though Solidscape remains valued for its burnout reliability.
Adoption and Industry Impact
The widespread adoption of DLP printing has restructured the economics of custom and small-batch jewellery production. A design that previously required a skilled wax carver several hours of bench time can now be printed overnight unattended, and design revisions that would formerly have required a new carving can be made digitally and reprinted within the same working day. This has lowered the effective minimum order quantity for custom casting and enabled smaller studios to offer bespoke work at commercially viable price points.
The technology has also influenced design vocabulary: undercuts, internal voids, interlocking structures, and extremely fine surface textures that are impractical or impossible to carve by hand are routinely achievable in DLP-printed models, and designers have increasingly exploited these freedoms. At the same time, some practitioners note that the ease of digital iteration can encourage over-complexity, and that the discipline of designing for the carver's hand imposed a useful restraint on earlier generations of jewellery design.
Quality control in DLP-printed casting remains an area of active development. Resin lot variation, ambient temperature, UV lamp degradation, and resin ageing in the vat all affect dimensional accuracy and burnout behaviour. Reputable casting houses maintain calibration protocols and resin management procedures to ensure consistency, and the major resin manufacturers publish detailed casting guidelines that are updated as formulations evolve.