What do we mean by Precision Micro 3D Printing?

What is Micro 3D Printing?

Micro 3D Printing (or Projection Micro Stereolithography (PµSL)) is a 3D printing technology for both prototyping and low-volume manufacture – sometimes referred to as Additive Prototyping (AP) and Additive Manufacturing (AM). The technology uses photopolymer resins that are solidified by ultraviolet (UV) light. As with SLA and DLP, which also use photopolymer resins, Micro 3D Printed parts benefit from near-isotropic material properties.

Importantly, with Micro 3D Printing a complete area is cured in one UV exposure, which is similar to DLP. However, there are some important differences between the technologies, one of the most important of which is the optics. Because of the optics and the way Micro 3D Printing operates, each exposure cures a relatively small area but with extremely high resolution. Also, the layer thickness is much less than in other 3D printing technologies. What this means is that Micro 3D Printing builds parts with exceptional resolution in X, Y and Z, and very smooth surfaces.

To quantify that, the resolution in X and Y is down to 2µm and the layer thickness is 5-40µm. Consequently, we quote a general tolerance on parts of just ±10µm to ±25µm, and the technology can produce very fine details, thin walls and sharp edges.

If you take another look at those numbers, you will see they are more than an order of magnitude better than the equivalents for SLA, DLP, SLS and PolyJet (our general tolerance on these parts is ±0.5mm).

Thanks to the high optical resolution and thin layers, Micro 3D Printing produces parts with a surface finish that is typically 0.4-0.8µm Ra on the top and 1.5-2.5µm Ra on the sides. Again, this is at least an order of magnitude better than for SLA or DLP, particularly on the sides. The smooth surfaces of Micro 3D Printing parts mean sanding and other hand finishing processes are not normally necessary.

As you can see from the above, the micro stereolithography technology 3D prints parts with far higher precision and accuracy than alternatives such as SLA, DLP or SLS, and is capable of creating features measured in microns. This is why the company that developed the technology, Boston Micro Fabrication (BMF), calls it Precision Micro Stereolithography and the company claims its machines produce the industry’s most accurate and precise high-resolution 3D prints.

Part size

One of the keys to the technology’s success is the optics. However, to achieve the very high resolution, each UV exposure covers a relatively small area. This is not a problem with very small parts but what if you want larger parts? Rather than move the optics further from the bed, which would compromise the resolution, BMF has developed a high-precision step-and-repeat system for moving the bed in X and Y. Larger areas are therefore printed by means of multiple exposures that are positioned very accurately relative to each other. The step-and-repeat approach also enables multiple small parts to be built concurrently.

The 3D printer we installed is a BMF microArch S240 with a build envelope of 100 x 100 x 75 mm, we don’t recommend parts with a dimension in Z greater than 20mm. Because of the very small layer thickness and the need to step-and-repeat, it would take a long time to 3D print a part that occupied all the available volume. However, it is normally the case that tolerances of tens of microns are only necessary on smaller parts, so build time tends not to be an issue.

Material choices for micro precision parts

Whatever 3D printing technology you choose, your part will only ever be as good as the material. Clearly, when you are 3D printing small features, the material needs to be high-grade in order that fine details have good definition, strength and stiffness.

BMF offers its own range of materials or, alternatively, microArch 3D printers can be used with other photopolymers. From a choice of, potentially, thousands of materials, we have selected the following:

• HTL resin cures to a black/carbon black high-performance engineering material with excellent strength and rigidity. Finished parts can withstand temperatures up to 114°C and are autoclavable. Water absorption is minimal.
• BIO resin is used for 3D printing non-implantable medical parts requiring biocompatibility. This material is transparent yellow, can be sterilised and has passed ISO 10993 biocompatibility tests for skin irritation and sensitization, toxicity, cytotoxicity, pyrogenicity and in vitro hemolysis. Tensile strength and flexural strength are marginally lower than for HTL resin and water absorption is even less.
• Matrix HTA300: Industry-leading, ultra-high temperature (300°C) resistant rigid plastic suitable for the harshest thermal environments.

These materials can be finished in much the same way as SLA or DLP parts. However, because of the small size, tight tolerances and functional nature of the parts for which Micro 3D Printing is typically used, secondary finishes are seldom requested.

Example applications

Micro 3D Printing technology can be used for applications such as medical devices, electronics, microfluidics and MEMS (micro-electro-mechanical systems), as well as for mechatronic systems, life sciences and turbomachinery. The ability to 3D print ultra-fine detail with tight tolerances is invaluable.

When you look at what Micro 3D Printing can achieve, you realise that it could be used instead of CNC machining certain parts where high precision is required. Nevertheless, the biggest potential lies in 3D printing parts that cannot be made any other way. This means designers can truly be creative and develop ideas that would not have been feasible before. And remember, too, that Micro 3D Printing is suitable for both prototype parts and low-volume production parts.

Talk to us

If you need micro stereolithography or end-use parts 3D printed with Micro 3D Printing, or would like to explore the possibilities of this remarkable technology, contact us on 01763 249760.