5 ms·
A 3d printer bed is never actually flat, especially since 3d printers are cheaper and the tolerances are usually pretty loose compared to a super flat, precisel
by mardifoufs 3y ago
A 3d printer bed is never actually flat, especially since 3d printers are cheaper and the tolerances are usually pretty loose compared to a super flat, precisely ground CNC bed for example.
One of the biggest issue/pain point in 3d printing for a while was to adjust the bed to make jt flat, or at least as flat as possible so that you can actually print without massive issues on the first layer. The process used to be manual, tedious and hit or miss (due to drift in the screws, or thermal expansion) etc.
Nowadays most new printers come with a sensor that probes the bed at multiple points (say in a grid of 4x4), then using for example a lagrange interpolation you can get a mesh that represents how flat your bed is. Then, using the visualisation you can either manually adjust the bed (with screws that rise or lower a certain corner), or even just let your printer compensate for the deviations.
That is, the printer moves the Z axis even when it is still printing on the same layer to make the print surface "virtually" flat (not always ideal if the Z axis stepper is trash, or if the deviation is too wide, or if there's too much vibration). That means that usually, the issue of bed levelling is mostly solved for newer printers!
Some printers also just use the nozzle itself as a probe, combined with a load cell. But those are usually on the higher end. The most common way is just a small probe of known size that sticks out and then calculates how much it extended before reaching the bed. (Some even use a pretty high res lidar to make sure the first layer is fine, even in some sub 900$ printers).
- NegativeLatency 3y agoOr an inductive sensor: https://help.prusa3d.com/article/p-i-n-d-a-superpinda-sensor-testing_2091 https://help.prusa3d.com/article/p-i-n-d-a-superpinda-sensor...
- mardifoufs 3y agoYep, having that by default since I think 2018, is one of the reasons prusas have a reputation of being super easy to use. It's way better than even a bltouch. Nowadays it's a lot more common thankfully though I don't think other big players use inductive sensors. Even prusa is now using a load cell that apparently will be used for much more than just bed levelling (the load cell could be able to tell if filament is stuck, because the motor will push without extrusion leading to a variation in load for example). Very exciting times in 3d printing honestly (and I say that as someone that is pretty "bearish" on 3d printing usually)
- lawn 3y agoIt's often not the bed that isn't flat, but that the rest of the printer itself moves and expands.
- mardifoufs 3y agoYeah or the bed itself is fine, but it's on a bad bed support. That's why even a perfectly flat glass bed plate can be completely uneven since the structure itself is crooked! Considering that quite a few printers are self assembled too (with basically no torque specs, and users that have little means to build it accurately), it's just compounded even more.
- zokier 3y ago3D printer made of Invar/Kovar next? :)
- dotnet00 3y agoThere are also issues like even if extremely flat, the way most printers mount the bed, it's going to bend measurably simply from expanding upon heating up and the distance between the mounting points not expanding the same amount.
- londons_explore 3y agoAs long as you always print with a hot bed, that effect doesn't matter - just calibrate it when hot.
- Mashimo 3y agoYou mean "As long as you always print with the same bed temperature"? Because there is a difference how your bed looks from 60 C for PLA to 110C for ABS.
- londons_explore 3y agoJust do the first layer at 110 for all materials. PLA actually adheres far better at 110C, but obviously you need to cool it down before building too many extra layers on top. Slicers have a setting for "Bed temperature initial layer" for exactly this reason.
- Mashimo 3y agoI find it easier and faster to just print PLA at 50 - 60 C bed and use probes for mesh and z level. I never heard of anyone printing PLA with 110C first layer.
- Baeocystin 3y agoI usually start my PLA prints at ~80C for the first layer, dropping to 65C for the rest. I first tried it because I was playing with PEO plates that had an iridescent pattern I wanted to strongly embed in the layer, but it turns out to be a good general pattern overall. Really reduced the amount of support material I need on certain prints, which is a big plus.