Comment by agent462 | Hacker News Reader

Comment by agent462 | Hacker News Reader

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Please explain to me why you think there is a fundamental engineering failure in the frame design - I'd like to see the data.

Just so you can get an idea of where I am coming from, I have a Prusa XL and a Voron 2.4 right next to each other.

The Prusa XL frame is very solid and it's also not a quad gantry. The lead screws take the weight of the bed. The Voron uses 20x20mm extrusions and the Prusa XL uses 30x30mm extrusions and it has stamped steel for additional rigidity and support. On the Voron, I've added titanium backers to reduce flex from thermal linear expansion. While the XL would technicall have thermal expansion, when enclosed, it will be much less from the much larger extrusions and additional support.

The toolheads on the XL on the other hand are heavy, they will likely be the larger issue with speed+quality. People also complain about the Stealthburner weight with TAP.

There are faster projects than the Voron just like there are faster printers than the XL. You have to weigh what you want. The toolchanger design, for me, works flawlessly and is so much better than the AMS, ERCF, MMS. More companies will clone it.

This is getting into first principles territory. The short version is that the gantry being on a cantilever and an open frame means it's going to act like a tuning fork under toolhead acceleration. Higher resonance limits toolhead acceleration before print quality nose dives.

I haven't seen any accelerometer graphs posted for an XL, but it doesn't take much more than opening up PrusaSlicer and finding maximum accels set to 3k to see the direct result of that. That's where the rest of the community was 4-5 years ago. There's a reason why Prusa has an entire blogpost making excuses for why their printers' performance numbers aren't up to snuff compared to modern designs (while also cherry picking comparative numbers)[1].

It's not my only complaint about the XL but it's the most obvious one. I haven't been impressed in general with the prints I've seen come off those machines.

[1] - https://blog.prusa3d.com/original-prusa-printers-now-printin...

So your theory is anecdotal.

You should also check out multi-color print times on the XL vs the ASM or any other solution.

I think what Bambu has done is incredible but these are different machines for different reasons. The XL has a massive print area compared to the Bambu printers and the toolhead design I prefer. I just gifted an x1-carbon to my mom for Christmas. I'm not a hater or Prusa shill but people are just spouting opinions without data or truly understanding the differences between the machines.

>So your theory is anecdotal.

It's based on basic engineering principles. Prusa can't magic away physics and these are lessons the rest of the community learned years ago. E3D had to course correct on some of the same mistakes with their toolchanger. There are good reasons why nearly every other CoreXY design you're going to encounter uses a closed frame (and the best will use structural panels).

>I think what Bambu has done is incredible but these are different machines for different reasons.

Sure, it's got its niche. But the drawbacks will narrow that niche. Prusa's ever narrowing niche is kind of the focus of the OP.

> The XL has a massive print area

Which makes running slow compared to other designs more painful since print times are cubic with volume.

>just spouting opinions without data or truly understanding the differences between the machines.

If you showed me a square wheel, I can tell you it's not going to roll particularly smoothly without needing to perform extensive testing on that specific implementation of square wheel. I can do that because it's something that's been tried elsewhere and we already know the results.

This style of open frame has been tried before. We know Prusa didn't choose to use it because there's any sort of engineering advantage because Jo has explicitly told us why they're using it.

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