Building an SLS system is more complicated than most realize. This is what SLS system manufacturers have been saying for years, five years to be exact, since the first SLS patent expired in February 2014. Then a few companies set out to change that myth and only one of them – so far – has succeeded: Krakow, Poland-based Sinterit. Its Lisa and latest Lisa Pro systems are real, reliable products. We had the chance to test and review their technology first-hand, after visiting the company in Krakow for a hands-on training session.
Sinterit was one of the very first companies to debut an affordable system in 2015, along with Italy’s Sharebot and Switzerland’s Sintratec. However, for different reasons, both these companies have been rather quiet about their projects. Then came new announcements from Spanish company Natural Robotics and from low-cost SLA market leader Formlabs. However, once again, both these companies have not yet launched a viable product to the market.
So, if you need to leverage laser sintering’s extreme geometric freedom using durable thermoplastic materials, today you only have one real cost-effective solution available. The good news is that – starting at just €12,000 – it’s also one of the most competitively priced. This is not a casual achievement. After former Google Software Engineer Konrad Glowacki and his partners, Michal Grzymala-Moszczynski and Pawel Szczurek, co-founded the company, they recognized the need to scale up with a professional management team. That’s when experienced new figures came in for senior management, sales, marketing and R&D, along with experts in key positions at support, production, finance and the legal department.
“When we arrived at Sinterit, about a year ago – General Manager Maxime Polesello told us in a full interview that will be published in full in the upcoming days – we realized there were so many opportunities and so many ideas. So, we decided to focus on one aspect first and foremost: print quality. Now our machines may not be as fast as industrial products priced more than ten times as high, but they deliver quality parts. Together with Jaroslaw [Pieniążek, CMO] we also decided that we would not play into the hype and we would only communicate our commercially available products. The Lisa Pro is here, and now the lead time is down to just over a month. And the market is responding in an amazing way.”
Playing the SLS game
My training day begins at 9 am on a sunny Krakow October morning. I walk down to the Sinterit HQ, not far from the city center. The company has now outgrown it and is ready to move to a much larger 2,500 square meter facility, a bit further outside the city. I meet with Michal Krzak, who is in charge of content and PR, and Grzegorz Konwalinko, Customer Support Manager. We begin by checking out some samples. I’ve seen some of these at shows and they really are impressive, both the hard nylon ones and the soft rubbery ones. I also find out that Sinterit has been making moves in materials, now offering as many as six different ones (with more in development) – including PA 12 Smooth, a really tough PA 11 Onyx (which requires the Lisa Pro to support a nitrogen atmosphere) and soft TPU and TPE, even light-colored ones. Most of the models have very smooth surfaces, some also have very thin walls.
Before coming in I had sent Michal a 3D model to print as a test, a cool looking Steampunk Octopus I downloaded from Thingiverse (designed by user jre). The idea was to find a model with moving parts. Although this geometry could theoretically also be printed in a filament extrusion system, I thought it could be good enough to test the SLS system’s precision as well. The truth is that the models that Sinterit’s Lisa Pro usually prints are much more complex.
The main idea was to find out exactly how hard it is to print using an SLS system. It’s not just a matter of pressing print, however, it’s not much more complicated than an extrusion system and probably simpler than most low-cost stereolithography. As you may have guessed, most of the challenges are in the file preparation phase. The model I used had some holes in the mesh so it needed to be fixed. Nothing overly complex to do, with any mesh fixing software. We then uploaded the file to Sinterit’s latest 2019 Sinterit Studio.
Great abilities and great responsibilities
The software comes in four versions. The basic Sinterit Studio is free with all systems. The Open version is €999; it comes free with the Lisa Pro and includes open materials parameters. The Profiles and Advanced versions are a bit more expensive and include the ability to process elastomeric TPU and TPE materials. The interesting part – Grzegorz tells me – is that these materials have much lower temperature requirements. Users can select the correct materials settings by following the prompts on the display.
We then proceeded to place the 3D model in the print area. This is probably the most complex part of the entire printing workflow because you have to do it just right in order to get the best results. “With great abilities also come great responsibilities”, someone once said. The same is true of SLS. The greater geometric freedom you enjoy means you can place a model anywhere in the build box. No supports needed. How well it will print will have a lot to do with orientation and thermal stresses. One valid indication to keep in mind is to avoid printing large surfaces as horizontally flat parts, tilting them instead. Another is to avoid having the laser jump around from a large surface to a small dot, as the layers build up on the Z axes.
Along with the fact that you can place the model anywhere in the build box, another very cool aspect of SLS is that you can do batch printing. In fact, you should do it. Models should be placed as near as possible to each other so that the temperature doesn’t jump around too much as the laser moves around a layer. The software allows you to move all the models as a single one in the 3D space, and also to move each model separately if you need to, which is a nice feature for batch printing.
The training on how to best position a part in the Lisa Pro build box took some time. However, nothing about it was beyond me. Skills will come in time with experience but a basic training session of no more than a few hours can get anyone printing right away. Sinterit and its distributors offer hands-on training sessions though many users feel comfortable operating on their own from the getgo.
It’s between you and me now, Lisa
The next part is the human-machine interaction. The Sinterit Studio software lets you control several networked printers. From the software, you can access each printer to queue a file and monitor prints through the on-board camera. Getting the printer ready to print is a bit more manual labour-intensive. However, it’s not as time-consuming as calibrating the plate on a low-cost filament printer and it is a guided procedure. One thing to really keep in mind is that you need to clean the laser protective glass and – even more importantly – the glass protecting the pyrometers. These are the systems that regulate the temperature in the build chamber. If the sensors cannot get a good reading and the temperature is off, so will your print.
Once all that’s set, you can fill the material. An SLS system has two platforms. One that goes up and adds more material for printing the next layer, and the other – where the actual sintering takes place – that goes down and gets filled with material layer after layer. When it’s empty, Lisa Pro needs a little more than one material container. Which is not that much and makes it an ideal solution for SLS material research (which, as Maxime told us, is actually one of the key applications for Lisa Pro adopters today). When the machine is full, it gets flattened out by the arm and you’re ready to print. Now you can just press print.
Handling the powder was a little strange at first. Unlike filament or resin, it is very fine and light so it tends to get dispersed in the air and I preferred wearing the protective gear. You do need plastic gloves and you should be wearing an apron to avoid getting it on your clothes. As you get familiar with it, you realize that it’s actually much cleaner than both filaments and resins: no thermoplastic fumes get dispersed in the room as the printing is fully enclosed and it doesn’t get nearly as messy as photopolymer resins. It’s also much easier to clean off: all you need is compressed air.
Lisa Pro review: not over till it’s over
As anyone involved in production 3D printing knows very well, printing is only the beginning. Post-processing is where most of the physical effort goes. When the SLS print is done, you get a “cake”, which is a rectangular box of compressed powder. You then need to break it up and extract the printed parts. While it does get messy, because of the powder, it is actually a fun process when compared to any support removal activity in other technologies. Once the parts are sufficiently clean you just place them inside the air compressor to finish removing any loose powder. This is also very easy to do.
You now have your parts, but if you want to optimize your investment, it’s good practice to recycle as much powder as you can. Sinterit says that you just need to add 30% new powder to the used powder in order to have an optimal print. While this is a best in class result, they are constantly working to improve it since the refresh rate is a key element in reducing part cost. A refresh rate of 50%, means that powder costs half as much in the end. In fact, Sinterit is currently working on a lot of new projects, including the next generation of machines. One technological focus for the next-gen will be streamlining the entire workflow, making it even easier and more error-free. In terms of market reach, Sinterit is continuing to push the products that they have now on the market, at a time when SLS 3D printing is really taking off in terms of adoption, even as giants like HP have made polymer powder bed fusion, in general, a more accepted and widespread standard for AM. Sinterit’s main priority will be to continue ensuring quality parts for a very low CapEx. And they already have that down pretty good.
This article was created in collaboration with Sinterit.