Using Layer Heights to get accurate z values
I'm trying to print small support pieces to go inside RF devices, which means they are all essentially rectangles with a little lip on two of the top edges. Surface finish doesn't really matter, but getting the final height in the z axis is critical. Is there a simple way I can use layer heights to make sure that my top surfaces lie exactly where I need them to be? If anything, larger layer heights are slightly better for my application, but when I go large, the slicer will round off the top bit so it matches a layer height it's able to put down. I've tried eyeballing it, but the slicer is optimized for getting a smooth curve over getting an accurate result. I can print a calibration cube, which are always multiples of the layer height tall, accurately, so I'm more worried about the rounding of the top layer.
I'm using a new MK3S and PrusaSlicer, but I'm willing to switch to a different slicer if there's one that does this better.
Here's an example of the type of part I'm talking about:
https://www.prusaprinters.org/prints/25978-rf-support
There's a bunch of variations on that, with different heights, so ideally I'm looking for some kind of setting I haven't found that does this for me.
Thanks!
Best Answer by __fense:
To follow up with this, a few days after my initial post Prusa released version 2.2.0 of Prusaslicer, with adaptive layer heights. This feature actually does exactly what I'm asking for when given an object with a flat top. all of the layers are the normal layer height until the last layer, which gets shortened to be the correct height for the surface of the model, and this will work with models with steps as well, correcting for every step at the right height. Exactly what I needed.
RE: Using Layer Heights to get accurate z values
Prints on a smooth PEI sheet with layer height 0.2 mm.
If the Z level of the printer is properly calibrated, your first layer should be 0.2 mm thick, and if the height of your RF support is evenly divisible by 0.2 mm then there should be no problem with the tolerances. As an example, I have printed a 40x40 mm cube. If I measure the height (Z level) on it, my digital caliper measures 40.00 to 40.01 mm. That accuracy should be sufficient for your RF support, or?
If you use the textured print surface, the tolerance may be slightly greater due to the grainy surface.
Bear MK3 with Bondtech extruder
RE: Using Layer Heights to get accurate z values
I am using the smooth PEI sheet came with the printer, and am getting decent tolerances with calibration cubes. I can consistently get a 20mm cube to be +/- .03mm, which is good enough for my application.
My issue is that the heights I need are not evenly divisible by 0.2mm. I'm pretty sure the motor steps can set positions of .0025mm apart, so I'm trying to find a way in the software to hit those exact marks without making my layer sizes tiny.
RE: Using Layer Heights to get accurate z values
Use 0.2 layer height and then use the variable layer height control to set the top few layers to be thinner might be a possible solution.
RE: Using Layer Heights to get accurate z values
To follow up with this, a few days after my initial post Prusa released version 2.2.0 of Prusaslicer, with adaptive layer heights. This feature actually does exactly what I'm asking for when given an object with a flat top. all of the layers are the normal layer height until the last layer, which gets shortened to be the correct height for the surface of the model, and this will work with models with steps as well, correcting for every step at the right height. Exactly what I needed.
RE: Using Layer Heights to get accurate z values
The variable layer height was in there before 2.2.0, only it was a manual process (you can still adjust it manually in 2.2.0). Its what I was talking about before.