See the measurement figures some posts above. I fully realise that measure that small parts (and a bit soft…) with a caliper is not very exact but it was the only method available to me. To measure the tiniest rods I had to cut them off and place the in the caliper.
I have now also tried to print the file at 25 microns just to compare. Then the tiniest sqaure ros failed and there are som “extra structures” aside the tiniest rods. My guess is that this represents curing made by the part of the laser beam outside the absolute focus (flair, rabbit ears or whatever) which is only produced at this resolution with 4 times as many laser passages as the 100 micron file. It ´s amazing that the very thin bi-rod aside the smallest round one survives to that hight during all the peel cycles before it eventually fails.
@KjellNilsson, Have you printed anything tall and thin lately? I’m wondering if that was perfect too? Your small stuff is amazing even with the laser spot test flared. I’m curious if any flare issues show up on your tall stuff.
If you mean light visible through 300 micron - i doubt you’ll get that. The surface (especially inside a hole) is too irregular for that. On top of that, there’s no way to get the resin inside such a hole out - the surface tension is simply too strong.
As such, light passing through the 300 micron hole is not a good indicator.
Being able to discern the circle from the square, however, is.
Re: surface quality - i think it’s due to castable setting, but mostly due to regularity/irregularity of the layer striations. When you put the previous print and this one side by side, there is really not that much of a difference, and the interesting thing is, the surface is the worst near the 300 um hole side, regardless of whether it’s facing up or down (previous print had that side angled up).
Remember we are testing a whole manufacturing process, not one single part of it. The methods, resin, hardware, and software is all one system that we are testing. It either makes a hole or it doesn’t.
Edit: It just occurred to me that it might be interesting to see a cross section of a print bisecting the two smallest holes. No idea on how to do it without mangling the holes, though. It’d have to be cut with a VERY sharp cutting tool.
Hi JoshK, I mostly print rather smal stuff so I don’t have anything tall and thin to show. I´ll be happy to print a tall test - which file do you suggest?
Just put my 100 micron print in the mill/router and cut away 1 mm on front and back and then cut away down to half the round holes. I made this a bit angled to not miss the tiniest holes. There is no trace of the 300 micron which could just barely be seen on the surface to begin with.
That was a very good idea to cut into it like that. Very interesting.
There’s prior prints to compare of of Kevin’s test part. If you want to give it a go I found a link on Steve’s post here.
I’m thinking the issue with printing small details, small objects, small holes has less to do with the “minimum feature size that the laser is capable of”, and more with the resin being used, layer thickness and the laser cure time per layer and area.
Having one setting for printing delicate details and large cross-sections/large items at the same time is not going to give the best result for either print. High-end expensive printers for example treat various parts of the model differently when curing. Thin areas need less energy than thick areas, etc.
So until there is some sort of variable curing algorithm that controls the laser intensity/scan speed based on the area type, this is the best we can get. It’s highly possible that these methods are patented by patent trolls such as 3ds.
Another huge factor is the peeling mechanism. I think a lot of those bumps and tears are because of the peeling, and the condition of the PDMS layer.
Another way to get really sharp detalis/holes, is to use a highly pigmented resin that blocks light more efficiently and is optimized for a certain slice thickness.
I know this or something similar is being done by some DLP printer software (perhaps the b9 software) and there are even free software out there that do similar things with DLP. Although it’s much easier to do this with DLP projectors because you can just use variable intensity masking on each layer.
From what i’ve seen, it’s already doing this… Kinda.
From my (limited) testing, it seems castable uses different exposure for infill, but the same (or almost the same) for perimeter compared to black. And, of course, it changes based on layer height.
Both are modifications to laser output power / exposure based on parameters of the print.
So i doubt anyone’s got the patent on that (it’s too broad and it would’ve already been breached), but there might be patents on algorithms to determine curing profile / laser power based on feature size and surface.
Also, it might not be as trivial as it seems.
Consider the following - let’s say you have a flat plane. And then a flat plane with almost a fractal surface as it’s texture. How do you determine which one requires the “detailed” curing profile? Total surface? Total surface enclosed in a fixed volume? Number of faces per ml? Number of edges per square mm? It’s not that simple.
What would make things utterly simple (but still offer the possibility to improve the print quality) would be a slider you can drag yourself:
Here is the test print of Kevins test part. 50 micron setting, black resin with black setting. Front side OK, left and right side rather OK but back side not good. Hinge side part to the left in pictures. Laser spot also attached. I would say the bad back surface is due to the laser spot…? Also rather much “gelly” in the resin after this print. The non-hinge side part is slightly better, could be more movement in the resin stirring away some of the partially cured resin around that part better than on the hinge side.
@Ante_Vukorepa, What size does that test part go down to? @KjellNilsson, Those look nice except for the back side. I assume that is because of the flare. That’s real interesting because your flare does not affect the min feature test.
I have a theory about that tall object and why the back is so bad and every other side is perfect.
I don’t think it’s caused by the flare, but by “PDMS fatigue” and by the peel process. When each layer peels off the pdms layer, over and over, the very end of the peel, depending on orientation can cause bad surfaces, especially when you use the same area, over and over again for a thousand peels.
I imagine if you twist that model and make it more like a helix, it will print just fine. It’s worth a try.
