Formlabs Resins Review: Grey V4.1, Tough 1500 V2, True Cast | Webinar

A Detailed Review of Grey Resin V4.1, Tough 1500 V2, and True Cast Resin. An analysis of specifications and their direct impact on prototype quality, functional parts, and casting master models

Center 3D Print recently hosted a technical webinar dedicated to the new generation of Formlabs engineering resins. In the world of additive manufacturing, selecting the right material is a stage just as critical as the 3D modeling itself or the printer configuration. Often, the specific properties of the photopolymer determine whether a prototype will fulfill its purpose: whether it will pass functional testing, whether it can be objectively evaluated visually, or whether it will transform into a flawless metal casting.

The goal of our review was not merely to list specifications, but to provide engineers, designers, and casting specialists with a clear technical toolkit for selecting materials tailored to specific tasks. The focus was on three key resins, each filling a specific niche in R&D and manufacturing processes.

1. Grey Resin V4.1: when visual precision is the priority

The primary objective of any prototype is to facilitate an objective evaluation of design and ergonomics. Standard glossy photopolymers often present a challenge: they reflect light, accentuating print layer lines and distorting the perception of the form.

Grey Resin V4.1 addresses this issue through its matte surface, which serves as an engineering solution rather than merely an aesthetic one. It diffuses light, effectively neutralizing the visual perception of layers. This results in a monolithic part with an appearance that closely approximates a component manufactured via injection molding.

During the webinar, we also highlighted a key upgrade in version V4.1 compared to V4: increased impact resistance. In practice, this means the prototype is less brittle and can withstand handling during post-processing or demonstration, significantly reducing the risk of damaging the model prior to presentation.

2. Tough 1500 V2: functional Testing Analogous to PP

When a visual assessment is insufficient and the prototype must actually "work," engineering resins come into play. Tough 1500 V2 is a material engineered to simulate the properties of one of the most ubiquitous industrial plastics – Polypropylene (PP).

Its modulus of elasticity (approximately 1500 MPa) provides a balance of stiffness and flexibility. This allows engineers to test part behavior–such as the operation of snap-fits, living hinges, or fasteners–in conditions close to real-world application. A prototype made from Tough 1500 V2 can undergo deformation and return to its original shape without structural failure.

The V2 update, particularly when paired with the Form 4 platform, demonstrates significantly higher tear strength. This enables the creation of reliable manufacturing aids (jigs and fixtures) and functional assemblies for actual field testing.

3. True Cast Resin: technical purity for flawless casting

The third segment of the webinar was dedicated to a highly specialized task: investment casting (lost-wax casting), which is critical for the jewelry and dental industries.

Here, the key advantage of True Cast Resin comes down to a single metric: an ash content of no more than 0.03%.

In practice, this ensures a complete, clean burnout of the model from the mold without leaving soot or ash. It is this residue in non-specialized resins that is the primary cause of surface defects (porosity, pitting) on the final metal casting. Using True Cast Resin minimizes, and often completely eliminates, the need for complex manual post-processing of the metal.

Additional benefits include high resolution for reproducing sharp edges and micro-textures, as well as dimensional stability, guaranteeing that the casting corresponds exactly to the initial CAD model.

Selecting the right material is always a compromise between mechanical, thermal, and visual characteristics. Understanding the deep technical distinctions between resins allows engineers and designers to accelerate iterations, reduce prototyping costs, and elevate the quality of the final product.

The full webinar recording is available for viewing

For those who could not join us live or wish to review the technical details, we have prepared a full recording of the webinar. This allows you to dive even deeper into the technical nuances of each material and see examples of their application.