Just procured an Elegoo Mars 3 resin printer to make locomotive parts. After studying build threads, reddit posts, and all sorts of other internet pages I decided 4K resolution would work for HO scale details. But I was still uncertain abut how detailed I could go before fillets turned into walls and other things that a small HOn3 locomotive presented. The fellow who blogged his On3 Shay at MRH talked about designing details just to have them obliterate in print, so I figured I'd have to draw, print, and re-wicker a bit. After it arrived, it took a bit of effort to get ready to use the thing. As has been described elsewhere, resin printing is messy and smelly. My workspace is small, in the far corner of the basement, and is also my day-job telecomute place, so I couldn't afford to render it unhabitable. It's also chilly, temp in the low 60s F all year round, So, for fume and temperature management, I built a cabinet for the printer and a bit of workspace. Not my best furniture, but I decided to do it cheaply, use it a bit, and then build a nice box when I figured out what design would work best. I also will be constructing a paint booth, so it's probable that the two will share components. Here's the first attempt: Please excuse the surrounding clutter. Floor and walls are 1/2" plywood from a shipping container, 24" on one side which fit well with a 20"x24" piece of plexiglass for the front. I used corner molding (holy cow, is wood expensive of late, 1 1/8" corner molding was $3US per foot...) to reinforce the rear corners and make slide slots for the plexiglass in the front. The top is an old cupboard door from a built-in we tore out decades ago. My thought with the slide-up plexiglass was to drill holes in the slide sides in which to slide pins to hold the plexiglass partially open in a couple of places, one being about 1" for the low air intake, another about 1/2 way up for operating the printer. This would make the plexiglass the front of a large "range hood" so to speak. The top just sits loose on top of the walls and slides back to allow the plexiglass to slide up. I planned to operate the printer without its cover, so I taped a sheet of red acrylic film on the plexiglass to filter UV light and still allow observation. The ventilation is just 4" ductwork with a 200CFM vent fan originally designed for grow tents. Hard to see, but hanging on the right-side wall is the fan controller, which allows 8 speeds. I also procured a small heater (in the box behind the right-hand container) and a temperature controller (hanging on the right-side wall below the fan controller). The fan hangs on a small piece of plywood that fits in the right side of the window, with a louvered vent to keep the squirrels out. After about a month of work, I finally got the whole thing ready for printing. So today was the day, started the heater first thing this morning to get the cabinet and contents up to 75F. I had already leveled the build plate, so when the temperature was reached I poured in a bit of resin and started a print of the compressor I designed for my DRG #168 project. A small part for easy first-print, but it had details I wanted to see the printer resolve (or not). Resin printing is such a tease, all you can observe for such small parts is the up-and-down movement of the build plate as it goes through its slice-by-slice exposure routine, no clue if any one of a dozen print failures has happened until the plate finally lifts from the goo. Ah, there hangs the part from the center, well something shaped like it anyway, so small.... One thing nice about the Elegoo printers, you can remove the build plate without disturbing its leveling, so I did that and gently pried the part off the plate. The slicing software made supports on rafts that had bevelled edges under which to slide the scraper, so the small part popped off easily. Too excited was i, so I rushed the alcohol cleaning and UV curing and ended up with white spots of excess resin. Turned around a second print, took a bit more time with post-processing and ended up with this: Westinghouse single-stage air compressor, HO scale, on 1/4" engineering grid paper. Even though I spent a good bit of time with two brushes and a lot of agitation, the cylinder fins still had excess resin, which fortuitously shows off the fin detail. I was sure it wouldn't survive. Indeed, every face, edge, and shape I designed in was resolved by the 4K LCD and Elegoo water-washable resin. The slicing software auto mode wanted to put supports all over the thing. I deleted those and put just five on the bottom of the part. For the final print, I'm going to embed the center support more deeply than the others so it can be used as a handle for drilling and painting. I still have more details and pipe interfacing to add, which I can now do confidently knowing the printer will resolve them. So, lessons learned: 1. The cabinet is too small (24" wide) in which to do work. 36" would be better for doing the cleaning, and might also be enough space to incorporate the paint booth as a separate wall insert to isolate the printer. 2. Fine details require vigorous cleaning. I might procure an ultrasonic cleaner... 3. There's a reason a lot of folk just leave resin in the vat, it's a pain to pour it back in the bottle and clean the vat. I need some sort of vat cover. 4. While printing is pretty convenient, all the prep and post work is still tedious and time-consuming; kinda reminds me of photo darkroom work. I'm going to plan my print sessions, preparing slice files containing multiple parts to take advantage of the printer's decent build volume. I've already assembled a slice file containing the compressor, smokebox front, and 168 front plate for tomorrow. After today, I think small parts will be easy to do. Next level of complexity will be boiler courses; the On3 Shay fellow had some good prose an pictures to help with that. After that, the cab; not sure if one complete print or three separate walls will work better to get flat, straight surfaces.
Congrats on a successful print and welcome to the wonderful world of resin printing! This is the way to do it. After printing for awhile you get into your workflow groove and you'll have a better idea of what you need. I like your ventilation setup - I was scoping parts for something like this but got distracted and never pulled the trigger. Have fun! -Mike
Got the fan at HomeDepot, AC Infinity Cloudline S4. For cutting the holes, Harbor Freight has the best prices on hole saws. Get the 4 1/4" saw; I got the 4" and have had to file extra diameter to take the fittings.
One more lesson occurred as I cogitated about yesterday's work: Get flexible metal build plates. Removing the Elegoo build plate yesterday was a bit awkward, trying to keep it from dripping all over the place, and I managed to knock it out of kilter with the mount ,which required re-leveling, which required draining the vat, etc. The third-party plates are thin steel mounted magnetically to the OEM build plate, and designed to flex and pop back into flat shape to facilitate removing parts. My consideration is that they would limit exposure of the leveled build plate to un-leveling, and be easier to remove and transport to a work area for post-processing. Also, multiple vat covers. Covering the goo immediately when the print is finished will minimize exposing it to droppage of parts and other stuff, and having at least two will make it easy to clean one while the other serves its purpose on the vat.
I'll preface this with minimal experience in resin printing, but I have seen the various magnetic built plates out there, but haven't pulled the trigger on them as I don't print enough. I use a steel palette knife (from any art store) like this one: https://www.dickblick.com/items/blick-painting-knife-716-x-1-516-detail-style-1-/. It will separate any print raft from the build plate with gentle pressure, wiggling the knife under the raft and side to side to loosen it. I had one on my modeling box, so I used it and it worked. Some use putty knives, but I found it too thick, and required extra effort to loosen the raft. I removed my build plate assy and reinstall it sideways on the machine to drain into the vat. That only works for short prints. I was printing N scale high-side coal gons, so they're pretty short.
