Model Railroad Control Panel - Manual Multi Color

I have for you today yet another model so specific that it will be useful to absolutely nobody. But since it was my first attempt at modeling/printing a manual multi-color project (multi-color on the same layer with no MMU) I wanted to post it as a vehicle for sharing my experiences with the manual multi-color process and to pass along some tips that may be useful to other folks like me just learning that process.

By the way, if you are interested in going “deadrail” with your railroad project (radio controlled battery powered locomotives…no more track wiring and cleaning!) I highly suggest you look into the S-Cab system that my buddy Neil Stanton in Seattle builds. The typical throttle setup is a carried around unit that you would certainly want for any larger railroad, but since I am doing a switching layout that will be 100% panel operated, I asked Neil to get me a stripped apart version so I could mount the boards on a control panel in alternate configurations. That way I have nothing in my hands and can more easily manipulate the throttle and the turnout switches simultaneously.

https://www.s-cab.com

The Good News: when it works out it is truly beautiful. Whenever I've done lettering or other accent color prints in the past, they were always done with recessed layers and full color-layer layouts, and while that looks OK, it is nothing like the quality of a well done flush-face multi-color print. AND, this process is in no way limited to the multiple colors on the base layers. There is absolutely no reason you can't model in accent colors anywhere in the print you choose.

The Less Good News: the process is a little bit tedious and requires a fair amount of babysitting, which is exponential depending on the number of colors and colored layers. I'll explain all of that as we go.

Before I start, if you haven't done manual multi-color yet and want to, I would HIGHLY suggest that you go to this forum subject and read through it front to back, and don't leave anything out. I'm not going to try and cover all of the settings and whatnot here so if you just jumped into using this model you'll most likely be horribly lost. The 3mf file I provided has all of the appropriate settings and special G-code revisions so you could conceivably save that as a configuration and start doing multi-color prints successfully, but it's better process to learn about the settings and whatnot yourself so you can debug and/or tweak as necessary/desired.

https://forum.prusa3d.com/forum/prusaslicer/manual-multicolor/

Rome Wasn't Built in a Day: your model needs to be designed with multi-color in mind. By that I mean rather than the typical way of modeling a single stl for the whole model, in this case each color is modeled as it's own unique part. Then when you import the various parts they are imported all at the same time. The slicer will throw up a “Multi Part Object Detected” notice to which you will answer YES I do want you to consider this a single object having multiple parts. That is how we get the slicer to apply specific colors to specific parts. (Side note: when you save your various stl files use file names with the color for easy recognition in the slicer.)

Colors are NOT all Created Equal: assess the colors you plan to use early and proceed accordingly with your modeling. What I mean by this is that in order to get the results you want you need to know the color and opacity properties of the various filaments you'll be using. For instance, even at 5 layers (see note later on) I found that my YELLOW was transparent enough that the BLACK would show through from behind and wash out the YELLOW to a dull look. To fix this I modeled in one less layer of YELLOW and added a layer of the very opaque WHITE across the back of the YELLOW before I went BACK to BLACK (screaming guitars in my head right now). Now I get a fully vibrant YELLOW.

Failing to Plan is Planning to Fail: to make sure and get vibrant colors without bleed through from the black background, this 4 color model was designed with a full 1mm of color depth, or 5 layers. With 4 colors, each layer has 3 color changes, which means in total this one required 13 filament changes (the 13th being back to BLACK for the rest of the print). You NEED to get yourself right with the world and accept that babysitting is part of the process here, so I don't recommend starting a print like this and playing League of Legends in between color changes. Focus on the task and sacrifice the time. On the same point of planning, even though I fully understand the order in which the slicer applies the 4 extruders as it moves through the model (check the forum topic), I ALWAYS go step by step and layer by layer in the slicer preview (using the lower slider bar) and make myself a map of the color changes on a piece of paper that I can follow and check off as they happen. It's important to note (and you'll read about this in the forum topic above) that the UI does NOT tell you what color you need to be inserting, so you CANNOT rely on that.

Establishing the Order of Operations - Ready, Fire, Aim?: when you bring all of the stl files into the slicer they are going to auto-assign to the virtual extruders (1 through 4) in whatever order the people who designed computers decided 50 years ago or whatever…alphabetical probably. And depending on your model it might not matter what part/color goes first. But in certain circumstances like my model here and most likely ANYTHING with text, there is a preference you want to shoot for. There's a text color and there's a color that surrounds the text and the goal here is to have the surrounding colors print FIRST and then have the text infill. In my case I wanted the BLACK and the YELLOW to print BEFORE the WHITE and the RED. If you print the text first you are asking for heartache my friend. Particularly with small text like this (the small text is 5mm which is about as tiny as I have gotten to work) if you print text first you're going to have a shitload of microscopic parts sitting there with next to no bed adhesion that are likely going to get plowed when the extruder comes to fill in around them. If you don't believe me just look at the size of the dot in the middle of the A's.

Purging Like a Stalinista: as everyone knows, when the printer changes filaments it purges some plastic to clear the nozzle of the old filament, and one purge is typically fine. However, when doing these finished face down multi color prints you're going to want to do a little extra purging, depending on the colors used and the order they are used in. Even though my choice of setup uses a wipe tower, sometimes that's just not enough. For example, when I'm changing from the Paramount Carmine Red to the Polyterra Subdued White, I'll purge three times PLUS what the wipe tower does. That red has so much pigmentation that it'll turn your white pink for quite a while. On the other hand, when I'm changing back to BLACK one normal purge is just fine. So just be aware of that…a few extra ounces of filament in the squirrel pile is better that a blown project with blending colors.

Boogers and Keeping Your Damn Hands OFF 'em: there's a lot of filament changing in a 4 color print like this (see below) so the potential for small bloops and boogers is elevated. My advice to you is leave them alone and let the 200-something degree nozzle deal with them on the next pass. My success rate with “fixing” issues is probably 50% or so, with me and my fingers/scissors/X-acto making things way worse about half the time. If you have something truly catastrophic you'll probably want to start over anyway. YMMV

Check Your Compass: going finished face down is all about pretty on the plate, so don't forget to take the infill into consideration. I like to adjust my infill angle to 0 degrees so the lines are parallel and perpendicular to the model. Default is 45 degrees which might look just fine to most folks but me no likey. Your call, just throwing it out there.

Mind The Gap: same argument here as infill direction regarding aesthetics. Typically the bottom of your print is part that you don't give a shit about because nobody will ever see it, and when you're printing a single color any little voids between the infill and the perimeters fade into the background anyway, so most folks probably don't even know where this setting is located <Print Settings-Advanced-Overlap>. BUT, when you do a multi-color finished-face-down print, all of a sudden those little gaps between black infill and some white lettering look REALLY bad at the default setting of 15%. You can tinker with this to suit yourself, but after a bunch of testing I find that 75% gets me to where all but the occasional tiniest gaps are gone. (Interesting to note that moving from 75% to 100% didn't seem to make any noticeable difference.)

Oh and don't forget to have fun!