Raft density and structure, and using rafts to achieve dimensional accuracy [solved]

[Andrew1 0]

I'm using cura 4.8 and there does not seem to be any way to adjust the density of a raft without the top layer being uneven. The density could be controlled with the line spacing but there's no way to make the topmost layer(s) solid while having many lower-density middle layers.

 

This seems important because unless the print bed is very flat I don't see how to make a dimensionally accurate part without using mesh leveling and a raft whose height is greater than the z-fade setting. If your raft is higher than the z-fade then the flatness of the bed no longer matters, just that the printer's x/y/z axes are orthogonal. However, if all but the first two layers of the raft must be solid then a 5-10mm raft for a large, flat part is not very economical. Wouldn't it make more sense for the raft to have a structure like that of supports, at least for the middle raft layers?

 

Perhaps the easiest way to implement this would be a setting to adjust the number of "middle layers" so then many low-density middle layers could be used to achieve dimensional accuracy and take up the unevenness of the bed without using too much material.

Edited June 26, 2022 by Andrew1

[Andrew1 0]

Thinking about it more, the raft and support settings could probably be unified so that any part of the object not touching the build plate (even if it's the entire model) is supported, or just the lowest part of the model (which would be similar to enabling a raft but without having supports). In this case, it would be convenient to combine the features of the support/raft so that rafts and supports can have separately adjustable bottom layers, top layers and any number of middle layers with adjustable fill, fill pattern, etc. That's probably how I'd do it, anyway.

 

P.S. z-fade is a marlin setting. I assume Ultimaker printers have a similar feature. It's my understanding that if the z-fade is set to N millimeters then the Z corrections applied by mesh leveling are gradually reduced during the first N millimeters of the print and are no longer applied after Z > N millimeters. I'm sure Ultimaker makes a fine product, but at present I only have an ender 3 whose bed is only slightly flatter than the swiss alps.

Edited June 26, 2022 by Andrew1

[Andrew1 0]

Looks like support for multiple middle raft layers was added in 5.0 (didn't see it at first because the setting was disabled), so I guess that solves my problem.