too long, didn’t watch: black and whiteimages limit your print resolution to the resolution of a pixel. grey scale images allowsyou to get sub pixel resolution. steve here from autodesk. on the ember teamwe’re exploring how to use software to get higher quality prints without changing ourhardware. let’s see how we can achieve some features that are smaller than the nominalresolution of the ember printer. so, theoretically,
best autodesk software for 3d printing, it all starts with the voxel.the voxel is the building block of dlp 3d printing. the size of the voxel, and in turnthe resolution of the printer, is defined by the pixel size of the projected image andthe layer thickness in the vertical direction. so a print of a 3d model is an approximationof many many tiny cubic voxels.
in a single layer, the location of voxels is set by the projected image. if a pixelis white, the projected light will cure the resin and solidify a voxel. if a pixel isblack, there’s no light and the resin stays liquid.this means that if the voxels are 50 microns on a side, we can arrange them on a grid with50 micron spacing. we could create a group of 4 voxels over here, and also another groupof voxels spaced 50 âµm away, or 100, or 200, or some other multiple of 50 âµm. but we cannotarrange them, say, 125 âµm apart because voxels are the indivisible atoms of dlp printing(in theory). so far we’ve been assuming that our imageis composed of either purely black or purely
white pixels. but what would happen with agrey pixel? would it print half â a voxel? if so, which half? top half, bottom half,left half, right half, center half? richard greene on the ember team created anexperiment where he printed a solid row voxels followed by a row of pixels ranging in brightnessfrom very dark grey (almost black) up to a fully white pixel. he found that pixels darkerthan a certain shade don’t print at all. then at a certain point a small, hemisphericalbump forms attached to the previously printed layer. a brighter pixel produces a tallerbump, and as the pixel gets brighter the voxel grows wider and slightly taller. this means the sizeof the voxel is can be controlled by varying the luminosity of a single pixel. in practicewe found that a grey-pixel or “half-voxelâ€
will tend to merge with adjacent voxel. so2 white pixels on the left and a grey pixel in the middle, the half voxel will form onthe left. if the two white pixels are on the right, the same â grey pixel will merge towardthe right. in practice this allows us to do some reallycool tricks. here is an image slice of printing a small cube with 10-pixel by 10-pixel crosssection and another cube of the same size that’s offset one pixel. by using just blackand white images that’s the best we can do with arranging their relative locations.now if we use grey values in the image, we can locate the cube with more precision thatthe projector should theoretically allow. this also allows us to create very precisevertical slopes. here, in the x-y plane, is
a cross section through a stack of slice images.note the voxels are rectangular because the pixels are 50 âµm in the x and y dimensionsbut here we’ve chosen to have 25 âµm steps in the z direction. there’s a vertical pillarof solid white voxels which forms a 90 degree angle with the base. but by adding a one pixelwide gradient of 32 grey values along the side, what we get is a very precise slopewhere each layer is roughly 1 and a half microns thinner than the layer below it. so insteadbeing perpendicular, we’ve added a precise draft angle of 3.6 degrees. all within a single50 micron wide pixel. here’s another great example. printing aslope of 75 degrees with just black and white pixels results in a stairstep pattern.because for every 7 or 8 25 âµm z-layers, there
is 1 50 âµm step over in the x-direction.however, if we use grey scale we get a much flatter slope.this also works with shallow horizontal slopes. by using a controlled gradient of 32 greyvalues we can create a very shallow slope -- all within a single printed layer -- thathas an average z step of less than 2 microns. the slope is less than 1 degree above horizontal.these greyscale tricks don’t magically allow you to print sub-pixel features, but theydo allow you to reduce the layer lines and
some other artifacts you see on 3d prints.check out some other related videos like this one about the difference between video andpattern mode in dlp projectors. there’s also an instructable in the description thatgoes into more depth about printing single
voxels with greyscale. thanks for watching!and have a beautiful tomorrow!
