Silicone DLP Printing Explained: Why Standard Resins Fail

Silicone cures differently, flows and shrinks differently, and needs its own cleaning and post-cure process, which is exactly why standard DLP resins and processes can't simply be adapted for it. This article explains why silicone 3D printing is challenging and how TrueSil combines dedicated material chemistry, printing technology, and post-processing to support applications from prototyping to production.

What Is DLP 3D Printing?

DLP-style 3D printers, or Digital Light Processing printers, are a popular choice for creating highly detailed and accurate 3D models. Unlike other 3D printing technologies that use extrusion or deposition methods, DLP 3D printers use light to cure liquid resin into a solid object.

In a typical bottom-up DLP system, the projector sits below a resin tray with a transparent window. The build plate sets the layer thickness in the Z-axis, exposure cures the layer through the window, and the platform lifts to "peel" the layer from the window so fresh resin can recoat before the next exposure.

In top-down DLP, the projector is positioned above the vat and cures the layer at the free surface of the resin. The build plate is lowered to the target layer thickness, and recoating happens at the surface without peeling from a window. This architecture can be advantageous for larger build areas and a wider viscosity range, since it avoids the separation forces and optical constraints associated with a bottom window/film.

The process is mature, and most materials on the market are rigid resin systems, optimized for stiffness, detail, and dimensional accuracy — a fundamentally different set of priorities than silicone requires.

Why Standard DLP Materials Don't Work for Silicone

DLP and SLA materials are photopolymer resins, typically formulated from three main components: monomers, oligomers, and photoinitiators. Under UV or visible light, the photoinitiator generates reactive species — free radicals, for example — that drive polymerization and cross-linking of the monomers and oligomers into a solid network.

Most photopolymer resins used in DLP and SLA are based on low-viscosity (meth)acrylate systems with relatively short molecular chains. When photocured, these systems can rapidly form a tightly cross-linked network. That can yield excellent print resolution and fast cure, but often at the expense of toughness.

Over the past decades, polymer additive manufacturing has pushed this chemistry past its early limitations — tuning acrylates and methacrylates, and introducing new chemistries, to deliver more resilient, elastomeric performance.

Silicone sits inside that same evolution, but represents an advancement step. Conventional silicones don't cure through the same free-radical photopolymer pathway, so making them printable typically requires chemical modification from the ground up. And even once a printable chemistry exists, silicone brings its own process control challenge: it takes advanced material formulation combined with a platform and post-process capable of precise, consistent part production. This is where Spectroplast's core expertise comes in.

TrueSil: True Silicone, Not a "Silicone-Like" Resin

TrueSil is a category of materials developed by Spectroplast to enable true silicone 3D printing. Our photo-silicone platform is designed to deliver the combination of properties that demanding applications require — such as strong tear resistance, high elongation at break, and low compression set — without the common trade-offs seen in many "rubber-like" photopolymers. TrueSil is also biocompatible, giving product teams a reliable foundation for skin-contact and medical-use applications.

We offer TrueSil A20, A35, A50, A60, and A60 Black, each grade engineered for specific hardness and application needs, reaching up to 1000% elongation and > 15 N/ mm. Silicone formulations are inherently highly viscous — our current TrueSil materials run up to 200,000 mPa·s, and that flow behavior strongly affects recoating, leveling, and dimensional stability during printing. This is why TrueSil currently runs best on top-down DLP architectures, where high viscosity is easier to manage: the design eliminates peeling forces, allows recoating at the surface, and provides the process control needed for consistent, repeatable results with thick, elastomeric materials.

True silicone DLP printing only works when the material and the process are engineered together: silicone's rheology and inherent softness affect leveling, feature definition, and deformation risk, so we develop formulation and process as one coupled system rather than treating them separately.

In our in-house production, this means repeatable, production-grade process control — exposure strategy, layer formation, handling — and, crucially, treating post-processing as part of performance.

Why This Matters for Your Application

If you're developing a medical device, soft robotics component, or precision seal, this gap is familiar. Fast prototyping tools work well for proving a concept, but the materials are a compromise — they don't tell you how the part will actually perform. True production material, by contrast, typically means injection tooling: $10K–50K+ in cost and 8–16 weeks of lead time before you know if the design holds up.

DLP silicone is built to close that gap: prototype in the same production-grade material you'd scale with, without committing to tooling first. Print one part or a thousand at the same per-part cost structure. Refine hardness or geometry between iterations instead of re-tooling. And when the design is validated, scale on your terms — we manufacture it, we co-develop it with you, or we transfer the material and process for your in-house production.

Ready to see how TrueSil performs on your application? Request a sample or get in touch with our team to discuss your project.

FAQ: Silicone and DLP 3D Printing

What's the difference between a flexible resin and true silicone?

Standard DLP flexible resin are most often urethane-based photopolymers, not silicone, and they don't replicate silicone's chemistry or long-term elastomeric behavior. Printing true silicone on DLP requires a dedicated silicone formulation and a process engineered specifically for silicone.

Is Spectroplast's DLP silicone production-ready?

Yes — TrueSil is production-ready today. Our TrueSil formulations are currently optimized for our in-house top-down DLP architectures and available now — you can order parts from us.

Is Truesil silicone compatible with standard DLP printers?

Because TrueSil formulations are highly viscous, they currently benefit most from top-down DLP for robust processing. Formulation validation is underway for commercially available bottom-up DLP platforms, and further platform validation is planned. We're working to make TrueSil available for your in-house production.

If your program requires true silicone performance — at prototype, at low volume, or at scale — contact Spectroplast to discuss material selection, application engineering, or in-house production. Parts quoted within 24 hours. Delivered in under a week.