Author Topic: 3D Printers  (Read 1667 times)

Spectere

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Re: 3D Printers
« Reply #30 on: April 30, 2018, 10:52:03 AM »
It definitely helps! I had both printers running for pretty much all weekend and the LulzBot was printing fairly nicely despite the Prusa shaking the crap out of the table.

The Prusa definitely has a bit of a speed advantage. It has a smaller and lighter toolhead compared to the LulzBot, as well as newer stepper motor drivers, so that thing can accelerate ridiculously fast. The LulzBot can move quickly, but it takes it a few moments to get up to full speed. The LulzBot also uses IGUS polymer bearings while the Prusa uses more traditional linear bearings (basically cylinders with tiny ball bearings along the edges). The IGUS bearings are known for introducing a bit of slop, so I suspect that the axis are slowed down intentionally to compensate. That said, after dealing with a seized linear bearing on the Prusa (which, in turn, gouged the crap out of one of the Y-axis rails) I think I prefer that!

It's kind of interesting when I feel the stepper motors while the printers are active. The Prusa XYZ-axis stepper motors barely get warm to the touch, while the E-axis (extruder) motor gets uncomfortably hot. Meanwhile, the LulzBot XY-axis steppers are hot to the touch while it's E/Z-axis motors stay cool. I suspect that's largely due to the extruder design. The Prusa uses two BondTech gears which grip the filament from both sides and push it in. This allows it to handle flexible filament a bit better, but it causes the motor a bit more stress. The LulzBot's standard toolhead uses a traditional setup, with a toothed gear and a pulley wheel pressing the filament against it.

The heated bed is a bit interesting. On both the Prusa and my old Wanhao printers, I could literally place my hand on a 60°C bed indefinitely without any major discomfort. On the LulzBot, 60°C actually feels like 60°C. I can keep my hand on the bed for maybe 2-3 seconds before it becomes painful, and that sucker can reach 120°C. O.O I'm not sure if that's due to how the hotbeds are calibrated, where the temperature is measured, or the type of material used, but it definitely makes a difference.

Also, I ended up ordering a 1.75mm toolhead for the LulzBot yesterday with a pre-installed hardened steel nozzle. The thermal properties of steel aren't quite as attractive as brass, but that'll allow me to print with abrasive filaments (glow in the dark stuff, carbon fiber blends, etc). Swapping nozzles is simple, though, so if I ever wanted to swap it with a brass nozzle it would be pretty trivial.

About the only nozzle that I wouldn't want to use on the LulzBot (though I could use it on the Prusa) would be the Olsson Ruby. Both printers do auto bed leveling, but they do it in different ways: the Prusa uses an inductive probe while the LulzBot uses conductive probing.

On the picture with both printers, take a look at the toolhead of the Prusa. You'll see a grey wire running along the right side of the extruder body. That's where the inductive probe is connected. It probes nine known points on the bed in order to build a mesh of the bed shape to account for minor warping.

Now take a look at the LulzBot. That one has four metal washers on the four corners of the bed. When it autolevels, it heats the nozzle up below the melting point of the filament, wipes the nozzle on the pad to the front-left of the bed, then gently lowers the nozzle down onto the four washers, checking for electrical conductivity. It uses that to work out what kind of angle the bed is sitting at. It's not as intricate as the Prusa's system, but since the LulzBot uses a glass build surface they can get away with that. You have to actually try to warp borosilicate glass.

So yeah, the reason it won't work with LulzBot's autoleveling system is because ruby isn't a conductive material. I've just made a short story long. You're welcome. <3
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Spectere

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Re: 3D Printers
« Reply #31 on: May 10, 2018, 12:42:59 AM »
I printed with nylon (infuses with carbon fiber!) for my first time today. Really really awesome surface finish, but it's stringy as fuuuuuck. Definitely need to dial in retraction a bit more. Kinda nice that the 1.75mm toolhead that I ordered for the TAZ 6 came with a hardened nozzle--it saved me from having to change it myself. :P

I also want to design a toolhead for the TAZ 6 at some point, so I've been looking into ColorFabb HT as an ABS replacement. ABS has some of the best temperature tolerance (its glass transition temperature is around 105C), but it lets off smelly, likely toxic fumes and has a nasty tendency to warp unless you build an enclosure for your printer to keep the ambient temperature high. ColorFabb HT is a copolyester, so it lets off minimal fumes, doesn't tend to warp as much, if at all, and HT is a specific blend that has a glass transition temperature of 100C. Copolyesters tend to be a bit stringier, but I'd rather deal with that than ABS any day of the week.

The only real hangup that I have with ColorFabb HT is that I've been having difficulties finding any sort of real information on how it performs in the real world. ColorFabb makes awesome filament, but I'd rather see a third-party put it through its paces. Most of the videos I've seen were people comparing it to PLA (which makes absolutely zero fucking sense given that PLA softens at only 60C). I want to see it compared with ABS. Even r/3Dprinting doesn't seem to have a whole lot of posts about it.
« Last Edit: May 10, 2018, 12:45:59 AM by Spectere »
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Spectere

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Re: 3D Printers
« Reply #32 on: May 14, 2018, 08:44:20 AM »
I just installed an amazing mod on the TAZ 6:

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