"Z" height in relationship to finished print dimensions
Greetings from Canada, to All,
Just finished putting together my MK3S. I found it a little difficult to establish/set the "Z" height, but am happy with the test prints I have done.
Printing artistic models generally don't have any rigid finished dimensions, but I will be printing detailed components that will have very specific dimensions (like the parts printed for the MK3S).
What I don't understand is the relationship between the "Z" height, the slicer program, and achieving accurate finished printing dimensions.
The "Z" height establishes a fixed squished factor, which creates the width, so how do you achieve the dimensions accurately? What happens if you have to adjust your "Z" height (my eyes aren't as good as they used to be)?
If someone could help me understand this it would be greatly appreciated.
Thanks to All the reply
RE: "Z" height in relationship to finished print dimensions
Are you referring to the Live-Z setting? That is only adjusting the relationship between the extruder and the build plate, once you get past the first layer each layer is the height set in your slicer program.
RE: "Z" height in relationship to finished print dimensions
Thanks @darcshadow, yes the Live-Z setting. How should I think about the settings, height/layer in PrusaSlicer?
RE: "Z" height in relationship to finished print dimensions
The Live-Z setting is to correct for the tolerance stackup of the position (and sensitivity) of the actual sensing element inside the PINDA probe in relation to the top surface of the bed. Not every printer will have the bottom of the PINDA probe at the same height relative to the end of the nozzle (following the build instructions you will get close, but that method of using a zip-tie thickness isn't likely to get sub milimeter accuracy). I haven't looked at the datasheet for the PINDA, but there is probably a tolerance specification for the distance between the internal sensing element and the bottom face. Most importantly, the PINDA senses the stainless steel sheet that is sandwiched in the middle of the build sheet, and the different surface layers (smooth PEI sticker, powder coated PEI, Buildtak, etc) are all different thicknesses. The zip-tie registration trick registers to the top surface of the build sheet, not the sensed stainless core of the sheet.
For the printing that I do (primarily PLA) the optimum live-Z setting will give me a first layer that actually measures the first layer thickness that I specify in PrusaSlicer.
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs
RE: "Z" height in relationship to finished print dimensions
Thanks @sembazuru, I don't quite follow your last statement.
Is there a way to check/verify what the Live-Z setting is prior to printing?
Is there a way to manually lower the Z-axis so I can move the nozzle down to the table, onto a piece of paper? That way I could measure/feeler-guage the gap to the bottom of the PINDA probe to the table. This process would allow me to replicate the Live-Z after changing filaments or nozzle. How can I manually adjust the Live-Z without printing?
Thanks, so much to learn.
RE: "Z" height in relationship to finished print dimensions
Thanks @sembazuru, I don't quite follow your last statement.
Is there a way to check/verify what the Live-Z setting is prior to printing?
Is there a way to manually lower the Z-axis so I can move the nozzle down to the table, onto a piece of paper? That way I could measure/feeler-guage the gap to the bottom of the PINDA probe to the table. This process would allow me to replicate the Live-Z after changing filaments or nozzle. How can I manually adjust the Live-Z without printing?
Thanks, so much to learn.
What I meant by my last statement is that when I have my live-z set properly for a particular print surface, then if I print a single layer square and then measure its thickness after pulling it off the build plate (wait for it to cool off to avoid stretching it while removing) its thickness equals what I have configured in the slicer. So if I print a 0.2mm layer, I measure 0.20mm with my calipers. If my live-z is too high (closer to zero so less negative) then I get a thicker first layer, and if my live-z is too low (further from zero so more negative) then depending on how much I either get a thinner first layer, or I measure a thicker first layer. (That last part is an odd effect, but happens because the extruded filament bead is being squished wider than the flat of my nozzle, allowing the hot filament to "pillow" up on either side of the nozzle.)
You can check the live z setting from the display menu. I'm at work now and my printer is at home so I can't check where that setting is at the moment for you. If you long-press the dial of your Prusa printer you can then move the z-axis (short cut for going through the menu settings to axis move), but that moves in 1mm increments. If you connect a computer to your printer with USB you should be able to use pronterface to move the axis, I think at 0.1mm increments.
Changing filaments shouldn't change the live-z setting. But, some people suggest manually changing the live-z setting for different filament types to get more or less "squish" against the build plate to either help the print stick during printing, or make it easier to remove after printing. I haven't done this so I can't attest to efficacy.
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs
RE: "Z" height in relationship to finished print dimensions
Thanks @sembazuru, I don't quite follow your last statement.
Is there a way to check/verify what the Live-Z setting is prior to printing?
Is there a way to manually lower the Z-axis so I can move the nozzle down to the table, onto a piece of paper? That way I could measure/feeler-guage the gap to the bottom of the PINDA probe to the table. This process would allow me to replicate the Live-Z after changing filaments or nozzle. How can I manually adjust the Live-Z without printing?
Thanks, so much to learn.
Yes, it's in the Settings menu option, or when printing its on the main menu.
Under Calibration, the First Layer Calibration function is designed to allow you to adjust the the Live-Z to get it set correct for the first layer. I've also seen others that create a simple single layer square and use it to adjust the live-z.
RE: "Z" height in relationship to finished print dimensions
Thanks, @darcshadow & @sembazuru. I have some exploring to do.
RE: "Z" height in relationship to finished print dimensions
The main thing is that all the layers that are sliced add up to the part height. The assumption is layer one is 0.20 mm (the default, but can be changed), plus all subsequent layers.
Height errors are layer one not being 0.2 mm due to bed surface variation. And the fact the actual height accuracy will be limited to selected layer resolution. I.e., plus or minus 0.025 mm if using 0.05 layers, or plus or minus 0.150 mm if using 0.30 layers.
Think about it as stacking blocks to make your model. A block is a fixed size, so you can only get as accurate as 1/2 a block.
All this said, a really intent person could use variable layers to get the best accuracy if they are willing to do the planning before they slice.