How To Prepare, Print & Clean Your Models
3d printing is simply amazing. You’re taking a liquid in a bottle and turning it into a solid, highly detailed object that’s ready for use. Can you print anything? No. But if the object that you want to print fits in the build volume of your printer, and you can make or find an STL source file for the object, then printing it is the next step. It’s an exciting new world!
DLP resin printers are quite different to FDM filament printers. FDM filament printers melt thin, spaghetti-like plastic filament and deposit it, layer by layer, onto a print bed, building up the desired model. With DLP resin printers, the resin is liquid and sits in a bath with an optically clear bottom. The build plate comes down into the vat of resin, hovering only one layer width from the bottom, and UV light is shone up from the bottom, curing the resin between the build plate and the bottom. That’s one layer. It moves up one layer width, and does it again. The model is printed upside down, looking like it’s being pulled out of the resin bath.
Let’s talk about the workflow, start to finish, on how to prepare, print and clean a 3d model printed on a DLP resin printer.
Select An STL File To Print
The STL file is the computer instructions that will be sent to the printer, telling it what to print and how. It’s essentially the electronic version of the model you’re wanting to print. There are two ways to get an STL file. You can find it or you can make it.
Finding an STL file is the way most of us get our STL files. You can go to websites like Thingiverse.Com or Yeggi.Com and browse. You can search google and use the extension STL. For example, search “Sailboat STL” on google, and it will return bunches of results for STL files that describe a sailboat model.
I belong to several 3d printer forums on Facebook that help people find STL files for the things that they are looking for. I tend to print items for my tabletop games, and so I belong to groups dedicated to this. Once you’re there, you can see where people are finding files, or even discuss with designers what they might design next. In there, several of the designers have run successful Kickstarter campaigns to sell their STL files. I’ve financially backed several of these and received STL files.
Some designers also use Patreon to fund their work. You pay a certain amount per month to gain access to what they’ve created. I do this too, for my favorite designers. It’s a good way to encourage them to keep making STL files for those subjects that you’re interested in.
To make an STL file, you’ll have to have some software that allows you to design 3d objects. There are several that you can purchase and use on your home PC or Mac, and there are several that work in a web browser, meaning that you don’t have to download or load any software. Simply point your browser to the website, login and begin to design. I said “simply”, but I didn’t mean it. Sure, it’s simple to get your browser to the correct page, but it’s not so simple to design. The learning curve to create 3d objects can be steep, but many do it and create excellent designs. Your mileage, of course, may vary!
Here are some free examples of 3d design software:
Once you have a viable STL file, you’re on to the next step, bringing it into your slicer software.
Add Supports In the Slicer
Load your slicer software. For DLP resin printers, I use ChiTuBox. It’s free and it has more features and seems to do a better job than the AnyCubic slicer software that came with my printer. Either will work, though. Load your STL file into the slicer software. You’ll see a grid representation of the print bed. In ChiTuBox, any areas of the model that show in red are outside the print volume.
You can scale, rotate and tilt your model as necessary inside the confines of the print volume. Once you’re happy with the placement, switch to the “Supports” tab. Here, you can add supports to your model. Supports are used as a sort of bridge from either the bare build plate or what’s already built, to areas of the model that aren’t already attached to the model.
So, think of a bent elbow, with the arm pointing up. When you print this, the print will get to the elbow and it can’t print. Sure, the elbow is attached to the rest of the body by the upper arm, but that upper arm hasn’t been printed yet. So you’re asking the printer to print the bottom part of the elbow before any of the rest of the arm. It can’t be done.
Instead, if we run a support from the build plate to the lowest point of the elbow, the printer will print this thin support structure, and when it gets to the elbow, it uses the support structure already printed as a starting point to print that elbow. This works rather well, and after printing, you can snip away the support, leaving only the properly formed elbow (and rest of the arm).
You can automatically add supports via the “Add All” button and ChiTuBox will figure out where it thinks you need supports. It’s not always perfect at this, so you may need to add a few more. I recommend watching a YouTube video or two on how to identify where to add supports. It’s quite easy to do.
Try these videos to get you started:
Slice the STL File
Once you’ve got your STL looking good and supports have been added, it’s a simple step to slice the model. Back in the modification tab, you’ll find a “slice” button. Simply click it. It will take the model as it sees it, and the settings that you’ve put in, and it will create a series of images and jam them into a single file. This file is called the sliced file.
You can think of this as a loaf of bread. If the loaf is the model, then the sliced loaf of bread is the sliced model file. Each slice represents one thin print layer. If you print them all, in sequence, you’ll eventually come out with a complete model. So the sliced model file is an interim step between the STL file and the finished product.
The slicer will tell you some interesting facts once it slices the file. First, it will tell you how long it will take to print the file. The finer the z-axis resolution (or the smaller the z-axis layer height) the longer it will take to print. Second, it will give you the volume of resin that you’ll use to print the file, and a price. The price is simply the volume multiplied by the cost of the resin. You input this number in your settings. For example, if your resin costs $50.00 per liter, and the print uses 0.01 liters of resin, it will tell you that the print will cost $0.50.
Once the software has completed slicing, it will ask you whether you want to save the file. I save to my “Sliced Models” folder on my computer, and give it a descriptive name. I then copy the same file from there to my USB thumb drive (I use the one that AnyCubic gave me with my printer).
One thing to note is that you don’t have to reslice the file to print the file a second time. You only have to reslice the file if you want to change something (like layer height settings, or orientation of the model or more supports). If it printed once, you can reuse that same sliced model file over and over again. I do exactly this when I’m printing model tanks. I never need just one. For some miniature armies, I need 10 or more of the same tank, so I reuse that sliced model files a bunch of times!
Prepare the Printer For Printing
If this is your first print, remove all the packing material from the printer and get it ready to go. Follow the instructions that came with your printer to set it up.
Put the resin bath vat into the printer and locked it down. Usually, this just slides in and you dog down the two thumb screws to secure it in place. Ensure that there are no holes in the FEP film at the bottom of the resin bath vat. If there is, under no circumstances add any resin. You’ll have to replace that FEP film.
If this is your first print, you will need to the build plate. This is a procedure that is described in your printer’s documentation. There are alternate ways to do this, and I’ve found a good way for my AnyCubic photon on YouTube. Here’s the link: https://www.youtube.com/watch?v=roAqm5c3rfU. You’ll only need to level the build plate the first time, then maybe every 10 to 20 prints. If you move the printer, you’ll have to level the build plate again.
Next, add some resin to the resin bath vat. I tend to fill mine about half way. I’m printing smaller items that don’t take a lot of resin. Remember to shake your resin bottle before you add the resin, to ensure that it’s well mixed.
At this point, you’re ready to print.
Transfer the STL File To the Printer
This part is easy. Insert the USB thumb drive into the printer’s USB port. The printer itself likely doesn’t store your files. Instead, it uses the USB thumb drive as its hard drive and reads the file from there.
You’ll know that the file is available for print if it shows up under the print menu on the printer’s screen.
Print the STL File
Select the file that you want to print in the list of files under the print menu of the printer. Once highlighted, hit the “print” button and the printer should start to function. Your slicer told you how long the print will take, and there’s nothing at this point to do but wait. You don’t need to watch it print (which is good, as prints can take as long as 12 hours!)
Remove the Print From the Printer and Print Bed
Once the printer has completed the model, it will raise the build plate up. Your print will hang below the build plate and drip for a while, shedding any left-over liquid resin. I tend to leave the print there for an hour or more, to allow it to drain. You get that resin back, and you get less resin on the model that has to be cleaned off.
When you’re ready, remove the build plate from the printer (on the AnyCubic Photon, I unscrew the one mounting screw and slide the build plate assembly off the post). Tilt the build plate while still over the resin bath vat to catch any extra drips of liquid resin. Hold there for a few seconds, then move the build plate and model over to some waiting paper towels.
Place the build plate on its side on the paper towel, and use a plastic spatula to pry the model and support material free from the build plate. This shouldn’t be too hard to do. Once it’s free, replace the build plate into the printer and tighten down the mounting screw. It’s ready for the next print.
Your model is free from the build plate and sitting on the paper towel. It’s time to clean it.
Clean the Model
Take your wet model and drop it into the first of your two cleaning solutions. I use two plastic pickle containers for this – one filled with Mean Green, and the other filled with tap water. I use pickle containers as they have a watertight sealable lid, and they have an internal basket that can be lifted out, allowing the liquid to drain.
Raise and lower the internal basket a bunch of times, creating liquid flow over the model. Do this for 40 to 60 seconds. Remove the model and let it drip for three or four seconds.
Drop it into water pickle container and repeat the process. When you’re done, remove it and let it sit on paper towel for a few moments, to soak up water.
At this point, you’re safe to handle the model without gloves on. It’s clean. Wet, but clean!
Remove Supports From the Model
Some people reverse this step and the next (UV Light Cure the Model) but I’ve done it both ways. If you use side clippers and remove the supports now, before curing, you’ll save yourself a lot of hassles.
The model and supports are still soft at this point, and likely a little wet. This is okay on both counts. Take your side cutters and clip each support free of the model until none are still attached. You may need to cut away some supports to get to others that are less accessible. If you do this step after curing, the plastic is brittle and can fly everywhere. It can also snap and take fine pieces of the actual model with it. I’ve broken several very thin fenders on vehicles because the supports snapped them off when they went flying.
Being wet can be an advantage as the supports, when cut free, likely stick to the model or your clippers. It’s easy to dispose of them, and they didn’t go flying every which way! I’m still finding some of my early model’s supports on the floor or behind books on the bookshelf well across the room!
UV Light Cure the Model
Take your now-support-free model and cure it with UV light. You can take it outside on a sunny day and leave it for a few hours, or you can use a UV chamber to cure the model. Simply place the model in the source of UV light (like on a backyard table or in a UV chamber) and leave it to cure.
I use a homemade UV chamber, as many times I’m curing the model at night. I have a day job and it’s much more convenient to clean and cure a model after I return from work. My UV chamber is made from an unused paint can, some reflecting plumber’s tape, a roll of strip UV LEDs, and a 12-volt power supply. I put the model at the bottom of the paint can, plug in the lights that line the inside of the can, and it can cure a 28mm Dungeons & Dragons-style figurine in 15 minutes!
Some purchase UV light stations that manicurists use to cure fingernail polish. They’re inexpensive, and will work well for small models. My paint can method is good for small or larger models, all the way up to the size of the can itself. My printer won’t print that large, but someday, I’ll pick up a larger format DLP resin printer and I’ll need the larger volume.
Your setup may take more or less time, depending on what UV resin you use and how strong the UV light is. I started with 12 hours, then 4 hours, and now I tend to let it sit for an hour, just to be sure. I’ve found models cured in as little as 10 minutes, but I do like to leave them longer.
Filing, Sanding, Priming the Model
Once your model is cured, you’re done. Your model is ready for whatever you want to do with it! Well done!
If you’re going to be painting your model, or you want a smoother finish, you may want to file and/or sand the model. Even at the finest print settings (like a z-axis layer height of 25 microns), you’ll still find very fine layer lines. Most of the time you won’t even notice, and you’ll ignore them. But if you do find that these lines bother you, you can use small hobby files and fine sand paper to clean the surface of your model.
You’ll likely only need to file and sand those areas where supports connected to the model, or where you see visible layer lines on flat surfaces. I don’t sand or file areas that have printed detail (like the faces of figurines, for example). A small hobby knife can be useful to scrape areas that a file won’t fit into.
Finally, if you’re going to paint your model, you’ll want to use a spray primer paint. I use cheap Krylon White paint and spray a light coat over the whole model. It’ll allow follow-on paints to stick well, and white won’t modify any colors that you use. If you’re a hobby painter already, you’ll be well familiar with priming and painting. Use the same techniques that you would use for an assembled plastic model.
That’s it. Your model is ready for use. In my case, that means ready for play!
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