Expert Interview: Petar Stefanov, Founder & CTO of Spectroplast AG, on the Benefits of Silicone 3D Printing

Material science in additive manufacturing is rapidly evolving, with silicone 3D printing being a particularly exciting development for the industry. Silicone is a versatile elastomeric material, known for its biocompatibility, thermal conductivity and heat resistance.  
 
Swiss company, Spectroplast, aims to push the envelope when it comes to silicone 3D printing. Following years of research, conducted at the Swiss Federal Institute of Technology in Zurich (ETH Zurich), Spectroplast launched its silicone 3D printing service bureau in September last year. 
 
In this week’s Expert Interview, we’re joined by Spectroplast’s Founder and CTO, Petar Stefanov, discussing the unique benefits of silicone 3D printing, the most promising applications for the technology and the realities of operating a 3D printing service bureau. 
 

Could you describe Spectroplast and the company’s mission? 

Spectroplast originated from several years of research of multiple PhDs at ETH Zurich, one of the world’s leading technology universities. With the launch of Spectroplast, our goal was to translate this research into a commercial opportunity.
 
The core competence of our company lies in material science. We’ve developed material chemistry that enables 3D printing of pure silicone.
 
In addition to this, we’ve also achieved quite substantial development on the process, as well as on the hardware. So, we cover the entire value chain needed to bring silicone from raw material all the way to a finished 3D-printed part.
 

What are the benefits of using 3D printing to produce silicone parts as opposed to traditional methods?

Conventionally, silicone parts are produced by injection moulding, a process which is tailored to a high throughput production and standardised designs. There are a lot of fixed costs attached to that process, due to the need to design and manufacture a mould. Also, the validation of the mould itself is quite costly and time-intensive. 
 
With injection moulding, we are talking about 8 to 12 weeks from when you place an order until you can see your first parts. The cost can go well above $100,000 for the mould alone.
 
If you want to change your design after seeing your first part, then you’d have to reiterate the mould, further adding to the cost and time. 
 
Spectroplast offers a complementary process to silicone injection moulding by using Additive Manufacturing (AM). Our process is tailored to the mass customisation of parts. This means that we can customise each individual part to produce the given specifications, while also saving material and energy. 
 
With injection moulding, some projects have scrap rates around 40% to 50%. This is quite significant, as it means that only every second piece works. We reduced scrap rates to almost zero, as well as the energy requirements. 
 
The ultimate benefit of AM is that with our process, shape complexity comes for free. Therefore, we can produce much more complex designs than is possible with injection moulding. 
 
To summarise, injection moulding is lacking in two key areas: the first is low to mid-volume runs, which is around 50 to 100,000 pieces per year. That’s the minimum required amount for injection moulding to be commercially viable. 
 
Second is the shape complexity. Complex parts that are either too expensive or too complex in general to mould can be more cost-effective when produced with AM.

What are some of the possible applications with silicone 3D printing?

Silicone 3D printing has applications across many different industries. If you’re in an office, most of what you see around you contains some sort of silicone part.
 
This is due to the material’s properties: silicone is an elastomer, a soft and stretchable material, and it’s non-toxic. It’s also biocompatible and resistant to heat, UV light and chemicals. It’s gas permeable, insulating and inert which makes it suitable for a variety of applications. 
 
Currently, Spectroplast is targeting higher-value healthcare applications like customised medical devices. These include devices like hearing aids, hearing protection, customised headphones, etc.
 
Other medical wearable devices, like masks, prosthetics, prosthetic liners — in particular shoe insoles — all the way up to customised medical implants, can benefit from 3D-printed silicone, due to its biocompatibility and softness. For example, tracheal stents and heart valves can be fully customised to the patient’s needs, thanks to AM.
 

You mentioned that you’re specifically focusing on healthcare applications at the moment. Could you explain the reason for that?

We believe that healthcare is a field where we can add the most value to our customers. To pinpoint one application, we’re very excited about the added value of customised prostheses, specifically customised breast prostheses for breast cancer patients.
 
After a mastectomy, part of the breast gets removed and most patients need to opt for an external prosthesis, essentially a silicone object that’s worn in a bra. Today, these come in a few standardised sizes and even fewer standardised shapes and usually don’t fit the anatomy of the patient perfectly. 

The symmetry is lost, and this has a major effect on the well-being of the patient. What we enable is the complete customisation of the prostheses to fit an individual patient and retain the original symmetry. 
 

Can you highlight specific examples of how you’ve helped your customers?

Talking about breast prosthetics, we have just partnered with the University Hospital of Zurich, which recommends that patients try our service. That’s our latest partnership that we’re very proud of. It’s important to be exposed to patients in need and get their feedback directly.
 
While I’ve mainly spoken about healthcare applications, we’re also active in other industries. Typically, these are uncertified applications, which we can immediately access, including automotive and aerospace customers. 
 

What are some of the challenges associated with 3D printing silicone specifically, since it’s very different from metal or polymer 3D printing?

The key challenge of printing silicone lies in the viscosity of the material. Silicone, in its natural state, is a highly viscous, almost gel-like substance, which is very difficult to process using conventional AM approaches. 
 
People are using different extrusion-based processes to print silicone. Examples include Robocasting and drop on demand, processes that involves extrusion of the material. Due to the material’s high viscosity, extrusion can be done right down to a specific resolution level, which cannot be further improved. Since the material is so viscous, almost like honey, extruding it through a tiny orifice has its limitations.
 
So essentially, the level of resolution, and therefore surface finish, as well as a range of accessible silicones, is limited by these conventional methods. What we’ve managed to do at Spectroplast is we adapted the material to a Stereolithography-compatible approach, or more specifically, a Digital Light Processing method, which yields a much greater resolution and therefore, improved surface finish. 
 
We’ve managed to improve the existing resolution level by a factor of 20. So, from around the millimetre tolerance, which was existent on the market, we brought it down to 50 microns. 
 
On the scalability side, existing methods of printing silicone aren’t industrially scalable in terms of speed and throughput. However, we’ve managed to increase the speed by at least 10 times compared to conventional 3D printing methods for silicone. 
 
We believe this combination of exceptional surface finish, together with the high throughput process, makes this the first AM technology for silicone that is tailor-made for use on an industrial scale.

What is it like to run a service bureau as a business? What are the day-to-day challenges?

The one word I would use to describe it is exciting. It never gets boring. This has to do with all the different client requests that we get daily. Spectroplast was incorporated in September last year. Since then, we have more than 150 B2B customers, and all of them have very different applications.
 
Every day we learn from our clients about new ways that our technology can be used, which we would never have thought of ourselves. This is invaluable because it helps us to develop the technology further in a direction that is needed on the market, rather than push something to the market which has already been developed. 
 
With that comes its own challenges. As we are getting so many different applications from our customers daily, we need to constantly adapt to each new application that comes in as an order. 
 

How would you describe the current status of 3D printing? And how do you see it evolving in the next few years?

We are at the tipping point, where AM is finally starting to become a viable manufacturing process. 
 
Finally, we have the technologies and workflows, as well as software out there, that can support the adoption of AM for serial production. However, don’t confuse this with very high-volume serial production. I don’t think we’re there yet. 
 
I believe there is a special place for AM as a complementary process to conventional methods, and it finds its own place in terms of production volumes and value.
 

Are there specific trends that you’re seeing?

Absolutely. For example, we noticed that the order volumes are increasing. We’re moving from simple prototyping and tooling to end-part production.
 
From the demand side, we see that product life cycles are becoming shorter, and products are getting more and more diversified. This means that fewer pieces of every design are being manufactured, which is very good for AM because this is exactly where it can add value. So, diversifying product designs and lowering the series volume of products is something we’ve noticed in various industries. 
 

Spectroplast recently received 1.4 million CHF in seed funding. What does this investment mean for your company going forward?

As I mentioned, we’re already serving more than 150 customers, and that customer base is growing daily. The investment will help us with upscaling our production capacity. We are investing in additional machinery and personnel, which will help us to support the larger and returning orders. 
 
On the other hand, the investment also helps to further develop the technology and to launch a new generation of materials on the market. 
 
All in all, we are pushing the quality level that our service bureau provides to the level comparable to injection moulding standards, which our clients naturally expect.
 
To learn more about Spectroplast, visit: spectroplast.com