Why True Silicone Additive Manufacturing Is Now a Reality

For most of its history, silicone additive manufacturing has been a category defined by what it could not do. The material is chemically incompatible with FDM. It does not cure cleanly under standard UV photopolymerization. Its low viscosity makes dimensional control difficult, and its softness makes printed parts prone to deformation before they reach final cure. These are real constraints — and for a long time, they kept true silicone out of additive manufacturing entirely, leaving engineers to choose between expensive injection tooling and material compromises that introduced validation risk.

That constraint has been resolved. True silicone additive manufacturing is now a production-grade reality — not as a laboratory demonstration, but as a manufacturing workflow delivering certified parts to medical device teams, robotics engineers, and precision manufacturers. This article explains what changed, what it means in practice, and why the material question matters more than the process question.

Why Silicone Cannot Be Substituted

Before addressing the technology, it is worth being precise about what "true silicone" means and why the distinction matters.

Silicone — platinum-catalyzed, thermoset polydimethylsiloxane — is defined by its silicon-oxygen backbone. That molecular structure is what gives silicone its combination of properties: elastic recovery across a temperature range of -60°C to above 200°C, resistance to UV, ozone, solvents, and biological fluids, biocompatibility that can be formulated to ISO 10993 endpoints, and dimensional stability under repeated mechanical and thermal cycling.

These properties are not approximated by TPU, TPE, or flexible photopolymer resins. They are specific to the silicone chemistry. A TPU part that is soft and stretchy at room temperature behaves fundamentally differently from a silicone part when placed in a sterilization cycle, a powder coating oven, a chemical bath, or a body-contact application over time. The material identity is not interchangeable — and for engineers working in regulated industries or demanding performance environments, using a substitute is not a design decision. It is a validation risk that surfaces later in the program, when it is more expensive to address.

The market has produced a large volume of content describing "silicone-like" additive manufacturing. The category that matters is different: true silicone — the same platinum-catalyzed chemistry used in injection-molded medical-grade elastomers — produced through an additive workflow with production-grade process control and documentation.

What Made True Silicone Printing Difficult — and What Changed

The technical barriers to silicone additive manufacturing are well established. Silicone's low viscosity causes flow and spreading before cure, making dimensional control difficult. Its non-thermoplastic nature rules out FDM. Standard UV photopolymerization does not cure silicone without chemical modification that typically compromises its core properties. And because silicone is soft even in its final cured state, printed parts are prone to deformation during both the build and post-processing stages.

Solving these challenges required developing silicone chemistry specifically for additive manufacturing — not adapting an existing photopolymer process to a material it was not designed for. The key advances were:

Photocurable silicone chemistry. Spectroplast's TrueSil materials are formulated as photocurable silicone resins that retain the silicon-oxygen backbone and platinum-catalyzed crosslinking chemistry of true silicone. The photocurable formulation allows layer-by-layer DLP printing while preserving the material properties that define silicone performance. The result is a printed part with the same thermal stability, chemical resistance, and elastic recovery as a molded silicone part — not a silicone-like approximation.

Process-controlled DLP printing. TrueSil materials are printed using DLP (Digital Light Processing), a vat photopolymerization process that uses projected light to cure each layer with high spatial precision. Managing flow behavior, cure depth, and layer adhesion for a low-viscosity elastomeric material requires process parameters developed specifically for silicone chemistry — not generic DLP settings adapted from rigid resin printing. Spectroplast's process development is the result of years of silicone-specific DLP optimization, producing parts with surface finishes and dimensional accuracy that match injection-molded silicone quality.

Controlled post-cure. Achieving final mechanical properties in printed silicone requires a controlled post-cure step that completes the crosslinking reaction initiated during printing. Cure conditions — temperature, humidity, and duration — are calibrated for each TrueSil grade to reach the target Shore hardness without over-curing, which can raise hardness beyond the design specification. This post-cure step is part of the manufacturing process, not an afterthought, and it is what converts a dimensionally accurate green part into a part with production-grade mechanical properties.

Four Hardness Grades. One Material System.

Most silicone additive manufacturing platforms currently offer a single Shore hardness grade. For applications where that grade matches the requirement, this is sufficient. For applications where it does not — and there are many — a single hardness grade means either accepting a material compromise or returning to injection tooling.

Spectroplast's TrueSil material family spans Shore A20 to Shore A60, covering four distinct hardness grades that address the full range of silicone performance requirements:

TrueSil 20 (Shore A20) is the softest grade in the family. It is suited for applications requiring high conformability under minimal force — soft seals against textured or irregular surfaces, patient-contact interfaces that must conform to body geometry, and compliant grippers in robotic applications where force control requires low contact stiffness.

TrueSil 35 (Shore A35) is the general-purpose grade. It balances conformability with dimensional stability, covering the Shore A30–40 range where most catalog silicone products are positioned. TrueSil 35 is the appropriate starting point for standard bore plugs and masking components in surface treatment, gaskets and seals in industrial applications, and soft-touch interfaces in consumer and medical devices.

TrueSil 50 (Shore A50) provides higher stiffness for applications where the silicone component must maintain its geometry under insertion force, fluid pressure, or sustained mechanical load. Through-hole plugs in anodizing and e-coating baths, structural gaskets in pneumatic systems, and robotic fingertips requiring higher contact stiffness for precision manipulation all benefit from TrueSil 50's balance of rigidity and elastic recovery.

TrueSil 60 (Shore A60) is the structural grade. At Shore A60, TrueSil provides the rigidity of a semi-structural silicone component — appropriate for multi-feature masking assemblies, boot-style covers for complex connector geometries, and functional components that must maintain dimensional stability across 50 or more use cycles. Shore A60 is the upper range of typical silicone elastomers and represents the boundary between compliant and structural behavior in the TrueSil family.

Hardness selection is an engineering decision, not a catalog constraint. TrueSil's defined Shore range gives engineers the ability to specify compliance level as a design variable — selected for the application requirement, not inherited from what a single-grade platform provides.

Where True Silicone Performance Is Non-Negotiable

Medical Devices

Medical device applications impose the most demanding material requirements of any industry. The silicone component must survive sterilization — autoclave, EtO, gamma irradiation — without dimensional change or property degradation. Patient-contact applications require biocompatibility documentation against ISO 10993 endpoints. And the material used in clinical validation must be the same material used in production — any substitution between prototype and production restarts the validation process.

TrueSil materials are formulated from biocompatible silicone chemistry and are supported by batch-level Certificates of Conformance, material traceability documentation, and ISO 9001-certified manufacturing processes. For teams developing patient-contact seals, custom interfaces, soft-touch handles, and implant-adjacent components, TrueSil provides the material identity and documentation infrastructure that regulated development requires — from the first prototype through production.

The prototype-to-production continuity argument matters here more than anywhere else. Many development programs prototype in a silicone-like material, then transition to injection-molded true silicone for production. When that transition happens, the engineering insight gained from prototype testing does not transfer cleanly — the material behaves differently under sterilization, compression set, and biological contact. Prototyping in TrueSil means the prototype is the production material. Validation data is continuous. The transition risk disappears.

Robotics and Soft Actuators

Robotic applications — fingertips, grippers, compliant joints, soft actuators — require silicone geometry that conventional manufacturing cannot produce without multi-part tooling and assembly. A robotic fingertip with an integrated tactile surface texture, variable wall thickness for controlled compliance distribution, and a rigid mounting interface cannot be molded as a single part. It can be printed as one.

TrueSil 20 and TrueSil 35 cover the compliance range for most soft robotic applications. TrueSil 50 and TrueSil 60 address applications requiring higher contact stiffness or structural rigidity in the silicone component. The ability to select hardness grade, iterate geometry in days, and produce functional parts in quantities of one to several hundred without tooling investment makes true silicone additive manufacturing a natural fit for robotic development programs at any stage.

Precision Manufacturing: Masking and Sealing

Surface treatment and coating applications — powder coating, anodizing, e-coating, electroplating — require masking components that survive process temperatures of 180–200°C with full elastic recovery, resist chemical bath exposure, and seal precisely against non-standard bore geometries that catalog plugs do not fit. True silicone is the only masking material that meets these requirements reliably.

TrueSil 35 covers general-purpose masking applications. TrueSil 50 is suited for through-hole plugs in bath immersion processes where fluid pressure could displace a softer grade. TrueSil 60 handles structural masking assemblies that must hold precise geometry across 50 or more coating cycles. Without additive manufacturing, custom silicone masking requires injection tooling at $5,000–$20,000 per geometry and four to eight weeks of lead time — economically inaccessible at development volumes. With TrueSil, custom masking geometry is available in days, at any volume, with no tooling investment.

From Prototype to Production, Without Lock-In

One of the structural limitations of current silicone additive manufacturing offerings is hardware dependency. Several platforms offer true silicone materials that are designed exclusively for proprietary printing systems. If you want the material, you buy the machine — and if you want to scale production in-house, you scale the machine fleet.

Spectroplast's model is different. The TrueSil materials that run in Spectroplast's manufacturing facility are the same materials available for in-house DLP production. Teams can begin with on-demand manufacturing — no capital equipment, no minimum order quantities, parts delivered in under a week — and transition to in-house production on compatible DLP hardware using the same TrueSil chemistry. The material system does not change. The validation data carries forward. There is no re-qualification cost when the manufacturing model changes.

This flexibility is the practical expression of a single principle: customers should not be locked into a manufacturing model that no longer fits their program. Whether the right model is on-demand parts from Spectroplast, application engineering for a custom formulation, or in-house production with TrueSil materials and process support — the material stays the same, and the customer retains full control of the path forward.

What "Production-Grade" Means in Practice

The claim that true silicone additive manufacturing is production-grade requires evidence, not assertion. In practice, production-grade means:

Dimensional accuracy. TrueSil parts achieve surface finishes and dimensional tolerances consistent with injection-molded silicone quality. Feature resolution supports functional sealing interfaces, precision bore plugs, and tactile surface geometries.

Mechanical property consistency. Shore hardness, elongation at break (>200% for TrueSil 20 and 35), and tear resistance are controlled within specification across batches. Post-cure conditions are calibrated per grade to prevent over-cure hardness drift.

Thermal and chemical stability. TrueSil materials maintain their Shore hardness and elastic recovery after repeated thermal cycling to 200°C — the operating condition for powder coating cure cycles and autoclave sterilization. Chemical resistance to sulfuric acid anodizing baths, e-coat chemistry, and common solvents is inherent to the silicone chemistry, not a coating or surface treatment.

Documentation. ISO 9001-certified manufacturing, batch-level Certificates of Conformance, and material traceability documentation are available for every production order. For regulated industries, documentation is not an optional add-on — it is part of the manufacturing deliverable.

The Decision That Matters

The question engineers face when evaluating silicone additive manufacturing is not whether the technology exists. It does. The question is whether the specific platform they are evaluating delivers true silicone — with the hardness range their application requires, the process control their quality system demands, the documentation their regulatory pathway needs, and the business model flexibility their program stage allows.

A single-grade, hardware-locked silicone AM platform answers part of that question. TrueSil answers all of it.

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.