There’s a great chart listing out the differences between the Form 3 and Form 2 in this comparison article:
The XY resolution for the Form 2 isn’t listed, but you guys tested it and found an XY resolution of approximately 150microns (https://formlabs.com/blog/horizontal-resolution-meaning-3d-printing/)
Why don’t you list this in the comparison article?
Going from a measured XY resolution of 150 micron down to 25 micron in one generation is phenomenal!
Minimum feature size and resolution have little to do with each other. Actual resolution of the Form 2 is much finer than 150u.
The Form 2 has a minimum spot size of 140 or 150u, the Form 3 has a minimum spot size of 85u. The minimum spot size is quite a bit larger than the resolution, (and I believe there is some antialiasing implemented on the Form 3,) so it is generally the limiting factor.
The other reason they probably don’t list it on the Form 2 is it’s actually better than the 25u on the Form 3, but it’s mostly academic.
The reason we don’t list it for Form 2 is that it’s not as well defined as it is for Form 3. The X-Y positioning on Form 2 is done by pointing mirrors attached to galvanometers with a very complex control system, some of which is analog, and some of which is digital. The analog parts of the system have no inherent resolution, the digital parts have resolutions on the order of a few um, and altogether the system has a repeat ability on the order of 10’s of um. In some cases, Form 2 could position the laser with better repeatability/precision than the Form 3, but the repeatability of this positioning is generally worse than that of Form 3. This improved repeatability yields generally smoother surfaces on the Form 3 than on the Form 2.
I wish we could make clearer comparisons, but its hard to give a small set of numbers with clear definitions that characterize how the printer performs across a wide range of parts.
A bit of reading on resolution vs repeatability vs accuracy may be helpful https://www.zettlex.com/articles/accuracy-resolution-repeatability-stuff/
The X/Y resolution would refer to the steps between positions of the laser spot, which isn’t something applicable to the Form2 since the position is changed using galvo mirrors. The Form3 has a galvo mirror for the Y-axis but moves the entire optical assembly for the X-axis. I’ve seen some other printers compare to the Form2 and incorrectly report the laser spot size as the X/Y resolution which isn’t the case. A smaller laser spot size (like on the Form3) allows for it to fit into tighter spaces and makes the corners sharper, resulting in an overall sharper print.
Here’s a simple explanation. “resolution” refers to a grid that divides a plane up into Pixels.
The idea being that each pixel is either on, or off. The smaller the pixels, the smoother a circle you can image with less noticeable stair stepping along what ought to be a smooth curve.
The Form 2 uses a laser that draws a continuous line. That is, it can draw a perfect circle ( well, almost )
This makes it more akin to an old fashioned PLOTTER that drives an actual ink pen to draw on paper- rather than an inkjet that squirts out tiny spots of ink. In X and Y there AREN’T any stair steps along a curve.
Not unlike a Filament printer that can extrude a smooth line of plastic in a plotted curve.
Laser spot defines the smallest CORNER it can draw… which will be the radius of the laser spot. and so has some effect on the detail it can achieve in sharp edges. Like how crisp a square can you draw with a marker that has a tip 3mm across, versus drawing a rectangle with a ball point pen. The sides of both will be perfectly smooth… but the corners on the marker drawn square will look rounder,
The Form 2 can also plot the path of the laser spot anywhere on the xy plane… so it can adjust the path such that the known EDGE of the spot runs along the profile rather than the center of the spot… so it can draw with positional accuracy finer than the spot size.
Ergo- it has no inherent resolution in x/y- The Form 3 has a smaller spot size, and so can draw a sharper corner than the Form 2- In very fine edged details, like, say, the scale pattern on a snake or dragon. the From 3 will achieve what looks like a more sharply focused result.
“repeatability” refers to the variance in any x/y profile from one z layer to the next. That is… so it can draw a ‘perfect’ circle on layer one… How perfectly can it draw ANOTHER perfect circle exactly on top of that first circle?
In filament printers this ‘repeatability’ is rather low and that is why you can see all the layers as each one shifts a tiny bit to and fro from the idealized plane they ought to describe.
This, combined with the specified layer heights in Z gives the Form 2 and 3 their only real parameter that can be expressed as “resolution”- .025" is the size of layer you are going to be able to make out in any model… and those layers will be made more or less noticeable by the level of repeatability.
DLP printers use an actual pixelated screen to expose the resin. therefore they DO have an inherent resolution in x and y.