Now the H2D is out, the main thing I notice, the carbon rods are gone!! :0
My main question is why. I’ve not looked too in-depth into it, perhaps it’s weight, or longevity, or something else.
Any thoughts? Anyone have horrible longevity issues with the X1 carbon rods? (iirc I’m about 2k hours in and haven’t noticed any degradation)
I would say: No, not flawed, but for the H2D, linear rails seem to be more appropriate.
They try to achieve excellent accuracy with the H2D and linear rails are far superior in stiffness. Especially when you load them with asymmetric forces as in a CoreXY gantry. The bigger build volume also implies higher demands to stay accurate.
The higher price of the H2D probably allows the more expensive rails.
The new head and especially the big laser probably come at a far higher weight. Also the drag knive will cause forces that are not present on a mere 3D printer.
I don’t think it’s about price, the $200 a1 mini has them but not the 1k X1C.
I also got the impression that the linear rails were also better suited to deal with the fumes that’d be caused by the laser engraver/cutter.
The carbon rods and graphite bearings are not compatible with the environmental conditions inside a laser cutter. They are highly susceptible to contamination (which is why you have to clean them every once in a while). Laser cutters generate tremendous amounts of thick smoke and fine particulate. They had to change to rails because they had to make provision for the contamination generated by laser cutting.
The rails are also probably a bit stiffer than rods, which helps with the higher positioning accuracy they’re claiming.
The carbon rods were probably a better choice for a 3D printer. You can’t listen to the YouTube crowd for everything. Carbon rods are significantly lighter, and light weight means the printer can print cleaner at higher speeds.
For example, an HGN 12mm linear rail weighs 200gr and the Bambu Carbon rods weight about 50gr together.
That alone saves 200 grams of weight not including the extrusion needed to mount the rail to which is another 600 grams. That’s 700+ grams excluding the screws and other incidentals.
In the case of the H2D, that is likely why the acceleration has been nerfed to 16,000 from the 20,000 max. The toolhead and gantry are just too heavy. IMO, it’s a modern engineering marvel that they didn’t drop any more speed on the H2D.
As RocketSled pointed out, the rails were likely an answer to the laser cutting addition. As he mentioned they also add repeatable precision to the mix (and are very long lasting and low wearing). I’d say the biggest accuracy part comes from the bearing surface more than the stiffness. In a CNC, RocketSled would be on the money, stiffness = accuracy, and it doesn’t hurt in 3D printing either. But because there isn’t much drag or forces acting on a print head, I wouldn’t expect accuracy improvements from just the stiffness, or at least not much. But the precision ground bearing surface with lubrication and a roller ball bearing that can be preloaded will almost always be better for accuracy than a rod on a loose-fitting bearing face, with no lubrication.
As for how long the carbon rods would have (or will) last… my 2-year-old P1S saw decent use and never hinted at a problem, so I’d guess they’d go at least 5+years.
The carbon rods also caused some issues-
I had to replace mine when my X1C was new to get it to print at higher chamber temps.
Why do you think carbon rods are flawed? As you said, you haven’t noticed any degradation. I am close to 9000 hours.
For a light toolhead, like X1 and P1 - you don’t need MGN12 rail, don’t overdo like that. Voron Trident’s toolhead weighs 450g and it requires only MGN9 rail. X1 would’ve been feeling great using a smaller MGN7H.
H2D on the other hand, has behemoth and heavy as hell toolhead, so MGN12 is somewhat justified over there.
Additionally, there are a few issues with carbon rods.
a) They are more expensive than rails.
b) They are glued into the gantry carrier which makes any repair to the rods to force you for a full almost 100% printer teardown (been there - done this).
c) Higher defect rate. Some people, including myself experience early gantry breakdown. Mine failed at around 500 hours.
d) Clogging. Some materials release particles that clog down rails. Hence constant maintenance (more often than SS rail)
e) They are noisy. Good quality rail is super quite and doesn’t make dry rubbing sound like X1\P1 printers.
100% agree with this and most of your other points. If you could spec a 5mm rail it would be fine, mostly because its generally mounted to another hunk of aluminum. But in all honesty, the X1 and P1 series probably could have been run much harder than Bambu did. That toolhead gantry combo was ridiculously light. Has any of the Speed Voron guys swapped out the rails for the rods and run a sub 5-minute benchy? Some of those closed loop stepper setups should be able to whip a light toolhead around pretty well (and accurately). I know they love their skeletonized gantries, but the carbon rods would make that weight saving easy and about a $1000 cheaper.
I had about 1000 hours on mine and maybe cleaned the rails 6 or 7 times ever. Mine were solid, but if I’m honest, I did keep it clean in general. And most prints were in the 1-hour range. So, they didn’t live a tough life.
There were a few discussions about that about 10 years ago or so. The consensus was that it’s not really a practical application, since the precision will be worse than a high-quality rail while costing significantly more.
But speed and acceleration-wise - modern Trident and 0.2 (of course given the nature of tinker printers - with some mods and good calibration) are far outperforming X1 in both speed and precision. Same with bone stock RatRig VCore 4. While being 500mm in size, standard was able to reach 16k acceleration, and hybrid 34k acceleration. So it’s not really about the acceleration and speed. BL X1 advertises 20k acceleration, but in reality, it prints way slower.