Meet Josef Průša: Founder of Prusa3D

The folks at HackSpace magazine have been having an awful lot of fun playing with/thoroughly testing the latest offering from Prusa Printers, the Mk 4. As part of that, they got the chance to pick the brains of Mr Průša himself, on the development process behind the XL and the new Mk 4, on 3D printing 3D printers, and why his suppliers hate their new X-ray machines.

Josef Průša, at home among the printers, which are busy printing more printers

Take us back to the beginning: how did Prusa Printers start?

Josef Průša: I found out about 3D printing and I found out about the RepRap project, which was wonderful. But… I’m not going to say that I’m lazy, but I like to do things urgently. So when I saw the original Mendel model, and I tried to build it, it was just so, so complex. Sourcing the parts and putting it together took far too long.

At the same time, I started to think about how to do it a different way with the things that I had around. And that is how it originally got Prusa-fied – my Prusa Mendel Iteration 2. 

But, from the very beginning, people kept calling it simply Prusa, because they didn’t want to use the whole big name. 

And that’s how it all started. I was doing it as a hobby for three, four years. And then I knew at that time that the university where I was studying wasn’t for me, I wasn’t very happy with the university. So I ended my studies there officially and, on the same day, I started the company.

Sometimes when you start a company, you have to let everybody know what you’re doing. But in my case, people had already started asking me to build printers for them long before I started doing so as a business. And they liked the design. So it was a little bit of a smoother start than usual. 

In ten years, we grew it quite a lot: I now have over 800 employees. And we make as much as we can here in Prague. We just opened our in-house PCB assembly line, so we have absolute quality control on the PCB stage, which is crucial for the longevity and the reliability of the printer. We don’t just outsource it somewhere else. Now, we manufacture in-house, so there can’t be any way to hide failures on the PCBs.

The MK4 has been in development since Before the Pandemic (BP)
The MK4 has been in development since Before the Pandemic (BP)

And I saw that you’ve bought an X-ray machine. What’s that for?

JP: That is part of the PCB assembly line, to be able to check for the voiding. I can tell you a lot of suppliers hate the X-ray machine. Because we don’t use it just for the PCBs; we can check the quality of a lot of other parts without destroying them. Sometimes if you have to mill something down to check something, the suppliers will come back to you and say that whatever defect you’ve found was broken during the milling process. 

This way they can’t trick you. And this is the second time that X-ray technology has become unpopular with our suppliers, because we also use handheld XRF spectrometers – like an X-ray gun that you can put on metal or something; you press a button and it’ll tell you the elemental parts of an alloy, for example. 

Sometimes we get suppliers switching the alloy for something cheaper, which can also be tricky. 

Do you still use 3D printers to print 3D printers in your factory?

JP: Yes, we do. We have over 700 now; most of them are Mk 3s, but we will soon be switching the whole farm to Mk 4s to get more throughput.

But yes, we still do it every day. I think it should be required for 3D printing manufacturers to use their machines in production, because the 3D printing world would be a much better place now if everyone did.

We do some injection moulding, but those are the parts that we know aren’t going to change, and it would be inefficient to make with 3D printing. But price-wise, it’s not that big of a deal compared to injection moulding. 

And the Automated Farm System is also getting quite complete; this will automate that process even further. We showed the concept machine at the Dubai Expo, representing the Czech Republic. It’s basically an automated [print] farm: you have rows of printers and there’s a picker which goes and takes the print plate out, puts the new one in, and everything is automated.

According to Josef, the current golden age of innovation in 3D printing is in danger if too many patents get in the way
According to Josef, the current golden age of innovation in 3D printing is in danger if too many patents get in the way

There’s also something very nice about open-source machines being made by open-source machines.

JP: It’s self-replication at scale. I was never trying to push it beyond what is reasonable, and I think that’s the key – to show our customers where it can be used. Because complexity in the 3D-printed parts doesn’t cost us much, and the rest of the parts can be quite simple. 

You can see this especially clearly on the previous Mendel model, the triangular shape where you can just use straight metal rods and all the complexity was held in the 3D-printed parts.

And you’re making your own raw materials now, including tungsten filament.

JP: Right! We were very pleasantly surprised because the first batch sold out quite quickly; we’ve since made a second batch, but evidently there is a big hunger for such materials. 

And it is quite cool to read the tweets a couple of hours after I posted about its release. You see guys saying ‘oh, I’ve been waiting for exactly this – I’m going to use it at work at the reactor shielding.‘ That’s a lot of fun! And we want to do more of the high-end filaments and materials in the future. We have some cool things in the pipeline, but I cannot talk about these just yet. 

Do you know what one of the biggest user bases for the tungsten filament is? People who like to go fishing. Apparently you can 3D-print part of the lure, to weigh it down. They didn’t have filament for that before. So, on the one hand, you have reactors; and on the other hand, you have fishing. Even though I know the filament is expensive, you don’t need to use all that much. So if fishing is someone’s really big hobby, a roll of tungsten filament might be cheap compared with some of the higher-end products in that hobby. 

Lengthy software support means your Prusa won’t turn into a paperweight overnight

Am I right in thinking that the initial demand for the tungsten filament came from a medical research centre in the Czech Republic? 

JP: The best way to come up with new products, the only way to come up with new products, is to try to solve somebody’s needs. In this case, it was co-operation with a hospital. And we nailed that down. And on top of that, we are finding use cases for many, many, many other fields.

That brings us on to Printables, the site you launched a while back to host 3D models. How’s that going so far?

JP: So for me, I think our biggest competitor in this regard was a little bit left behind by its parent company. 

I knew that we needed to do something; we already had as our domain name, for our own blog, so we used that. 

I’m quite happy that we used the Prusa Printers name as a way to grow it. Because, at the moment when it was time to switch the name, we knew that it was a very good concept and we were not afraid to, you know, get such a wonderful domain as

It was quite a hassle to acquire it, but I’m very, very happy about it. I think there’s a chance that will be the largest [3D model hosting site] by traffic within the next year. I’m very, very happy about it. 

That’s not long at all.

JP: Three years of hard work is actually a long time in the 3D printing space. Especially at the very beginning, it seemed like a very daunting task to become the number one, but as we are growing and growing, I can see it happening quite soon. 

It really is a service to the community for us. We still don’t run ads – I’m very happy about this, that there can be some nice place on the internet that doesn’t have hidden extra ways to squeeze money out of the user.

On a different note, I saw an update from the Elizabeth Holmes trial and it reminded me to offer you a belated congratulations on making it into the Forbes 30 Under 30 list. 

JP: Three years on from making that list and I still haven’t been arrested! 

What is more important to me than these awards is that my printers’ users are happy with the machines, getting upgrades, upgrading them to the new models. That’s what brings me joy. Not being on some list. 

What good is being on a list? We’re not seeking any investments. Rather, we invest ourselves in local hardware startups. There’s not many people investing in hardware, especially if it’s everyday working things. We backed an IoT bike lock and stuff like that, which is also important.  

I guess that you’re not working on a ChatGPT extension for PrusaSlicer then?

JP: That will be interesting. What’s going to happen in a year from now? If we make a prediction now of where AI will be in a year from now, we’ll be laughing at ourselves in a year’s time. We’re obviously looking into using the new technologies in many places around the company. But I value security and safety and privacy quite a lot; I don’t think many of the AI machine learning things which are now being hyped can be done quite safely or privately now. I think, in the rush to adopt this stuff, a lot of engineers at some companies are just pumping super-secret stuff into the GPT interface over the internet. That is not what we would like to do. We would like to do all the machine learning on the premises.

Who owns the art created by AI? Because it’s just an amalgamation of all the data that was put in, it would be very difficult to prove a breach when anything with a non-commercial licence has been used. 

What I tried myself is coding. Over the years, I got quite rusty in programming, I must admit, and I just wanted to test it out. So I did a little script to take data from one API and put it into another API. With me being rusty, it might have taken me three days. But with all the new AI stuff, it was done in an hour. I had to correct it a couple of times, but it was quite amazing.

If I may make one prediction, I think people will soon start to value face-to-face communication a lot more, because we’ll get fed up of all the chatbots trying to pose as real humans. 

You decided to add RGB LEDs to the Mk 4. 

JP: I mean, RGB LEDs are just fun. But, you know, sometimes when you have the printer at the other side of the room and you’re printing at high speeds, you don’t know, you don’t hear if it’s printing well or not. I wanted to have a quick way of glancing across the room and seeing what is happening with the printer, if everything is OK. The RGB LED is a good way to indicate that. 

So, it’s not because of the normal maker tendency to put flashy lights on everything?

JP: No, no – I really try not to have parts on the machine which are just non-functional in 3D printing. 

And the next-gen extruder – what was the breakthrough there? 

JP: The breakthrough was the combination of all of the parts in one. Basically, we just manufacture one big, solid part. There are no connection points; it is impossible for it to leak. People call it the blob of death, when they don’t tighten the nozzle properly and the plastic gets heated and starts to leak, and you come to the printer and you just see the extruder covered in a huge blob of plastic. [That can’t happen with our extruder.]

That is one of the things that we are very happy about. It is faster, it’s more reliable, and more integrated. We wouldn’t be able to do the load cell without it.

And are you planning to keep supporting the Mk 4 with upgrades, like you have done from the original Mk 1?

JP: So, I would say with the Mk 3 we have a very good track record. We’ve been doing firmware updates and keeping everything top-notch for five years. And that is just the beginning. 

We still support the Mk 2s and everything. So I would say we are ready to support the Mk 4 for quite a long time. That is what people love about us: the machine is not a paperweight after a year.

And I’m especially proud of the possibility to do the upgrades, because we have saved a lot of e-waste this way. People love it. And I love it too.

HackSpace magazine issue 67 out NOW!

Each month, HackSpace magazine brings you the best projects, tips, tricks and tutorials from the makersphere. You can get HackSpace from the Raspberry Pi Press online store or your local newsagents.

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