Two topics are addressed in this thread that I have some experience with and might be able to offer some useful insight
Topic One Scanners:
Watching the scanner advertisements, the vendors sure make it look easy. Just check out their ads on social media and the majority of the comments read like those in this thread. Easy? Nothing could be further from the truth - especially if you need to edit the mesh produced. (Usually called "point clouds" which I think is an apt description.) One was shown in this thread already, with bazillions of points. To reduce a mesh by combining adjacent polygons to something you could work with in your lifetime would take more time than it takes to learn how to model and build your own part!
Mesh reduction is very labor-intensive. CAD programs like Fusion, SolidWorks, ProE and the like don't care about polygons. You can change the mesh density within them, but you aren't going to get something that's easy to work with in it's simplest form (four-point polys) if you ever need to manually edit the mesh. CAD programs output a mesh in triangles, so the first step is to combine each pair of triangles into a quad (four-point) polygon. I've reduced some huge CAD-generated meshes, but I had to turn them into STL files and reduce the mesh density before they were worth spending several days to a week of eight-hour days reducing them to prevent my modeling program from choking to death. I specialize in tedious, but the workflow isn't for everyone. It took me several weeks to figure out how to reduce SolidWorks (our CAD program of choice at work) to be compatible with my modeling program which was used to turn the SolidWorks parts into photo-realistic objects. Nobody online seemed to know how to do it.
The first time I sat down with a mechanical engineer to attempt a conversion, we took down the server at our facility and another connected server in another city. We thought it was just our computer that locked up. The chorus of "WTFs!!!!" that echoed down the halls convinced us otherwise. We never said a word and an onsite IT guru brought everything online after a major outage that took a weekend. We refined the procedure with smaller CAD files until we found an optimal solution. I'm sure he's recounting that story to this day at that place.
I've attached a file that explains how I converted it into my modeling program (Lightwave3D) I posted online years ago in the main Lightwave forum that generated a lot of thanks and interest, but it assumes you're using SolidWorks. At the time, I imported the STLs (since we weren't 3D printing) into OBJs which I imported into LW. The conversion program mentioned below, is from Canada, which didn't meet the US-made software criteria for where I worked, but I have it installed on my personal computer for times I find a cool file built in say, Maya and need it converted without having to own a copy of Maya.
This is a paid program I've used for nearly twenty years called "PolyTrans64" which can turn nearly any CAD or modeling program output file into an STL. You can check their site and decide if it fits your needs and budget.
Okino PolyTrans and NuGraf, the primary 3D CAD, VR/AR and DCC/Animation conversion + optimization products on the market for well over 30 years. Hand's on, one-on-one, personal communications and customer driven '3D conversion solutions'.
www.okino.com
Topic Two: Printer Resolution
There is no comparison between FDM (filament) and Resin print resolution when detail counts. It just isn't physically possible because of hardware limitations.
The default hole diameter on most FDM printers is .4 mm. I've seen smaller, (and larger) but the smaller sizes clog so easily it's a PITA to deal with the aftermath.
Once a .4mm bead is laid on the warm build plate, the next layer has to be compressed against it. Let's say by half for a .2mm layer height (I'm being generous). The result is the visible layer lines common to nearly all FDM printers. Great for Braille, but not-so-good for modelers. When removing layer lines, you either get to spend an inordinate amount of time sanding, or covering the part with an epoxy-like finish and you'll still get to sand. Acetone vapor smoothing can be used, but have fun using it. That's just for the surface finish - FDM cannot get the resolution needed by most of the highly-detailed model parts used in this hobby unless you're printing at a scale you could float in.
Resin printing can get down to 22 microns (and smaller.) That's .022mm compared to .4mm in the example cited above. After using several ridiculously expensive ($6K) high-maintenance, Raise3D printers at work for four years, I took a chance and splurged on a $500 Amazon deal for a 50-micron printer and UV cure station at home. My first submarine hull section was silky-smooth and needed just a few minutes of 600 grit sanding to be ready for priming. I took the parts to work and every engineer that saw them was blown away by the level of detail, which looked like it was machined or injection-molded. I hope they added a few resin printers after I retired, but doubt it, since the majority couldn't bear to get their hands dirty or thought "manual labor" was beneath them. (We tended to hire prima donnas, with the expected results.) I took over maintenance to learn more about FDM printing, which prevented large puddles on the floor due to snowflake melt.
FDM printing is great for fixtures and jigs. I've got a friend I can call and have stuff like that printed if needed, but it's rare that I would need them. FDM printing is fast, and it isn't messy. (Unless there's an issue and the print head gets stuck in a molten blob of plastic, or it starts air-printing and you return to a printer full of spaghetti.) PLA is non-toxic but easily warps when heated. I lost a completed submarine hull when I painted it and let it dry outside for ten minutes in the sun once after investing days sanding it. Lesson learned.
Resin printing is for detail work and smooth hulls that require minimal sanding if they're modeled with small polygons. Large polygons can be seen as faceted surfaces and require sanding to remove.
Resin printing is messy as hell. I don't advise doing it in a room inside a house - especially if you're married. It needs a specially-prepared work area, with surfaces protected by silicon mats and smooth floors like concrete. The fumes can be toxic and require a ventilated space that is climate-controlled. The temp band is usually centered around 72 degrees. A heated enclosure can be used but the thermostat's duty cycle is important to prevent banding on the model.
Resin eats skin, so rubber gloves and eye protection is required until it is cured via UV light. If any resin gets on your gloves, it will etch the plastic covers that most printers use. Get some flicked in an eye and you've got serious problems - especially if it cures even a little bit under ambient light. Spill resin (and you will) and you're thank the day you put a paper towel holder within easy reach. Before every cleaning cycle, I cut paper towels into different sizes for the amount of resin I need to clean off. Little ones for single drops and larger pieces for wiping down my build plate to avoid contaminating more IPA.
Routine parts cleaning is messy. The outside of the part is covered with liquid resin. The only cured part is the space between the layers. Some folks like to submerge their printed parts for a few minutes in 91 IPA in a cleaning station that may have an agitator. (IPA eats resin and will ruin your detail if you forget about it while it's submerged.) Then you have to place it in water to clean off the remaining resin and dry it with compressed air. If you cure it with water on the part it leaves a white film you have to clean off.
After cleaning, you have to deal with the waste.
I started out submerging my parts in IPA which got expensive. On a large format machine, you can easily use a gallon and it is less effective with each use.
I read a tip online about spraying a finished part with IPA in a spray bottle in a plastic tub along with an inexpensive foam brush and reduced my IPA use by 95%.
The brushes last a couple of cleaning cycles and get tossed in the trash, along with the contents of the plastic tub, which is usually just a couple of tablespoons of IPA. It evaporates but still stinks up the garage, so I place the plastic-lined trash can outside when necessary. The used water goes in a plastic jug and any resin settles on the bottom where it's cured by sunlight. I pour out the water and toss the jug.
Both of the plastic tubs I use (resin and water) are wiped down with clean paper towels after each use. The "clean" tub (for water rinsing) will get covered with sticky, uncured resin residue so I wipe it down with an IPA-sprayed paper towel since I don't want that gunk on my parts.
The first couple of times I cleaned my resin parts (after four years of FDM printing at work) I was depressed. Cleaning took so much longer than pulling off a bunch of plastic filament supports with my bare hands. I got used to it and could do it faster, but it wasn't until I quit submerging my parts that it became bearable, and less expensive. Now, it's a 20-minute process and I'm used to it. Having a dedicated, protected spot in the garage to clean parts with everything set up beforehand is a big timesaver. The incredible detail and minimal sanding (if required) is worth the extra time and effort.
Support removal is easy. Once I soak the part in hot water -to help release the part from the build plate, with the aid of a thin, metal scraper, the supports soften. I either pull them off with my gloved hands or cut them off (if it's a super-delicate part) with nippers after curing.) The supports go into the trash containing paper towels and IPA.
The learning curve for resin print slicing is steeper than FDM. One of my favorite FDM printing slicers has always been ideaMaker - free from Raise3D. The same screen graphics are replicated on their (large) 3D printers.
I hope this doesn't put anyone off regarding resin printing, but if you're on the fence, you need to know these things before pulling the trigger and/or getting divorced. My brother-in-law bought a resin printing setup for his gaming miniatures without knowing any of this, and thought he was going to do this indoors on his bench in a carpeted room. I brought him to his senses, and he got a refund without opening the boxes.
If you love the detail of resin printing but hate the hassle, your best bet is to have someone do it for you.
For the conversion procedure below, substitute "Lightwave" for whatever modeling program you're using if converting to an editable mesh.
Questions? Fire away.
CC
modelshipworld.com
