10 Things I Wish I Knew Before Buying A DLP Resin 3d Printer

Buying a DLP resin 3d printer is the start of a journey to understand how to use it and how to use it safely. Take a look at these tips to get a good understanding of what you need to know before your first print.

Most 3d Printer Resin Is Toxic and Caustic

Just as the title suggests, 3d resin is toxic and caustic. It burns your skin, and in extreme cases, can burn your skin with chemical burns that require extensive medical treatment. With a few simple safety measures, though, it’s easy to stay safe and have no worries!

There are different styles of resins that you can buy, each with its own properties. Some are general purpose, some are flexible, some are harder, some are temperature resistant. Regardless of the properties, all of them have similar working safety procedures that should be followed. You’ve likely seen that nitrile gloves are required for working with 3d printer resin. That’s true. Other rubber gloves won’t protect you like the nitrile gloves will. They are specifically designed to handle harsh chemicals, so perfect in this application.

Be respectful of liquid resin, but don’t be terrified. It is easily cleaned up and damage is easily avoided. Spills should be wiped up immediately with paper towel, and that paper towel disposed of. Don’t hold on to it and reuse it. If you’re worried about any residue remaining, wipe the area down with Mean Green (the liquid I use to wash my models – see the next point). Liquid resin is thick, and not prone to splashing, but consider eye protection when working with it. If somehow you get liquid resin in your eye, was your eye immediately and seek immediate medical help. Getting it in your eye is a big deal. Treat it as a very serious medical issue and respond appropriately.

On removing a model from the build plate after a print, I accidentally dripped a single drop of liquid resin onto my pants. I didn’t even notice. I went for breakfast with my friend, and when I came back (one hour later), my leg itched, burned and hurt. I removed my pants and found a 3-inch circle of red on my leg. The resin had soaked into the material of my pants and spread out. The close proximity to my leg, along with a little sweat (from the heat of the day), made my leg react. I was in time to handle the issue with no major issues. I removed the pants and washed them. For my leg, I washed the area thoroughly, and then soaked the area for 20 minutes. I have access to a hot tub, so I’m lucky in that regard, but simply laying a wet wash cloth over the area should help. It itched for a day, but it went away overnight.

I think I was quite lucky to notice and handle the issue quickly. I was amazed that it only took one drop. There is a YouTuber who discusses a resin spill on his clothing (way more than one drop) and his ensuing medical issues. His spill resulted in Level 2 chemical burns. He too ignored the problem for a time before treatment.

Now that you know this, watch for any drip on your clothing. If you don’t notice, but you do notice itching later, check it out. You’re now in an activity that requires you to pay attention. Know what to do (remove the clothing and treat the chemical burn). The earlier that you start treating the issue should you have a problem, the better off you’ll be. Ask for help if you need it. The more careful you are, however, the less likely you’ll have an issue. Stay safe!

Don’t Use Alcohol To Clean Your Models

I see a lot of sites and YouTube videos recommending isopropyl alcohol for cleaning completed resin prints. Let me be clear, this will work just fine and even the manufacturers recommend this liquid for cleaning. My concern is with the alcohol itself, not the job that it does.

Alcohol is a fire hazard. It’s a minor hazard as the printers are rather well built, and in normal operation won’t electrically arc, unless something has gone horribly wrong. But why take the chance? Alcohol burns with a flame that’s very difficult to see, and can get out of control extremely quickly. For me, that scares the innards out of me! If there’s an alternative, I would use this instead.

I wouldn’t be mentioning this if there was no choice but to use alcohol to clean your models. I use Mean Green, a common household cleaner, to clean my models. It’s perfectly safe, and it won’t ever catch on fire. Other advantages are that the liquid is much friendlier to your skin and it smells rather nice. And it’s vastly cheaper! I buy bottles of Mean Green in the gallon size for not much money. It’s safe to store and is so much safer to handle and have around.

But the biggest question is does it clean models as well as alcohol? The easy answer is yes. It cleans the model very well. 30 to 60 seconds in my plastic pickle jar filled with Mean Green, agitating lightly (to get liquid flow past the model) and then 30 to 60 seconds in clean tap water in the same way. Once you’ve done this, remove the model and you’ll find no remaining liquid resin on the model whatsoever. You’re good for post-processing (or cleaning off the supports, in layman’s terms).

Slicing of the Model Is the Most Important Thing

The most critical variables in whether a print will succeed with a DLP resin printer are bed leveling and slicing. Bed leveling is a simple process that you can follow the instructions that came with your printer, or watch any one of a number of YouTube videos to understand.

Slicing, however, is how the computer onboard the printer knows what the shape of the UV light on the screen should be for each of the layers of the model. Slicing software, too, is where you’ll add supports for your model so that it will print correctly. You can make or break how a model prints with how you slice your model.

You can use the slicer that comes with your printer (if any) or you can download ChiTuBox from https://www.chitubox.com/download.html. I recommend this slicer software for several reasons. First, it is free. They have a Professional, paid version but the free version does everything that you would need for home use, so why not? Second, it does an excellent job with supports. It highlights where a model is unsupported and thus where to put your supports, and it also does a decent job with automatic support creation. I use this automatic support creation first to get me 90% of the way there, and then add supports (I almost always do this) or take away supports (I almost never do this) as necessary.

The slicer is where you put in whether or not you want a raft (an island of plastic that the printer prints first, then the model is supported from that raft). I always use a raft, and raise the model 5mm above the raft. I find that I get the print to work near every time when I do this, but I’ve failed in my printing near all the time when I don’t use a raft.

Your “resolution” is set here too. I put resolution in quotes, as the X and Y resolution of your prints is set by the pixel size of the UV screen at the bottom of the printer. There’s no changing that (although you can turn on anti-aliasing to get smoother printing on organic shapes like faces). You can, however, change the layer height for the Z axis. Here, I use either 0.050mm (50 microns) or 0.025mm (25 microns). 25 microns is obviously the better Z axis resolution, but it means that you’re doubling the number of slices that the slicer will create. That means that it will take double the time to print. If one of my tank models takes 5 hours at 50 microns, it’ll take 10 hours at 25 microns, but the layer lines will be so much smaller, meaning less or no cleanup like filing or sanding to be done.

When printing, a part of a model that isn’t connected to another part already printed will fail. Essentially, you’re asking the printer to print a new layer in thin air. The piece will not print correctly. Instead, a support from the raft to the first part of the piece hanging in mid-air will ensure that the mid-air piece will print on top of something (the support). The slicer, when switched to Adding Supports mode, will allow you to see where a model is unsupported. You can see areas highlighted in red, and you can walk through the layers via a slider bar to see if there are any islands. An island is a piece of the model started where there either isn’t another part of the model below it or no support below it. Once you find an island, simply add a support and you’re golden.

Once you’ve got all of your supports and your settings correct, hit that Slice button, and then copy the resulting file to your USB thumb drive to transfer to your printer. Print away!

What Happens When My Print Fails?

When a model doesn’t print or a part of it fails to print, you won’t know until quite late in the process. I don’t watch my model for hours, so the first time I see if my model has printed or not is when the print is all done. While the print is in progress, it’s mostly obscured by the resin bath, so you can’t actually see if anything is printing or not.

When a part fails to print, the part that failed still leaves behind a portion of cured resin on the bottom of the resin bath, stuck to the FEP film at the bottom of that resin bath. I’ve had it happen that I printed six fantasy figures for gaming, and only four actually printed. The others left a round disk on the bottom of the resin bath (usually the same size as the raft that was going to be printed for the model).

Don’t panic! This happens from time to time. There are two things that you’ll have to do before you can print again. Simply removing the parts that did print and trying again isn’t going to work, as there are plastic bumps on the bottom of the resin bath, and that will 1. stop the build plate from getting close enough to the bottom for a good first layer, and 2. obscure any light coming through the FEP film. No resin will cure there so whatever is supposed to be there, according to the sliced model, will not print. You’re just cascading the problem of failed prints with yet another one.

First, remove the build plate and remove your models as normal (if any did manage to print). Clean the build plate and make it ready for use the next time you print.

Second, remove the resin bath from the printer very carefully. It’s still got a lot of liquid resin in it, so be extra careful to keep it level and don’t slosh it. If it spills, do whatever it takes to ensure that it doesn’t get on your clothing or skin. Jump, dive, do whatever it takes! Next, clean up as soon as you can, but do it safely. Assuming you don’t spill, drain the unused resin through a paper filter back into the resin bottle. It can be reused again. Throw away the paper filter.

Third, you can now see the pieces of cured resin plastic on the bottom of the bath. You’ve still got your nitrile gloves on, of course. Gently lift up the FEP film from below, flexing it and pry the cured resin plastic up with your fingernail (through the glove). It should just pop off! Once you have all of the pieces of cured resin off the FEP film, go ahead and wash the resin bath with Mean Green and then rinse with clean water. Dry with paper towel and you’re ready to put it back in the printer and pour in some new resin.

FEP Film In Your Resin Bath Is Fragile and Expensive

As a safety note, watch for any holes in the FEP film. If you see one, do not pour in resin, or if there is any in there, pour it back into the bottle as soon as you can. Again, spilled liquid resin, even through a tiny hole, can damage you or your printer, or both. The only option with a hole in your FEP sheet is to replace that FEP film, which is not that hard to do, but it is time consuming.

Watch this video on how to replace the FEP film from AnyCubic and another from Elegoo. It’s the same for nearly all of the DLP resin printers out there.

FEP films can be purchased online but they’re expensive. I found it difficult to separate the sheets, and in fact, replaced the FEP film on my resin bath with three FEP sheets. They stuck together and I didn’t realize I’d grabbed three instead of one. Now that I know I can do that, it’s easy enough to check the edges and separate the film until I get just one, but I didn’t realize that when I did it the first time.

Elegoo was rumored to be bringing out a line of replacement resin baths. These are supposed to be plastic and will fit into most of the DLP resin printers out there. That’s something that you may not know: Elegoo, AnyCubic, MonoPrice and a few others all use the same design for the resin bath. It means that you can use an Elegoo resin bath that comes with an Elegoo Mars printer in an AnyCubic Photon or vice versa. As of writing, these replacement items aren’t available. 

Your Plastic Spatula Is For the Print Plate, Not the Resin Bath

As the title says, only use a plastic spatula for removing models from the metal build plate. Do not use it to dislodge cured resin from the FEP film on the bottom of the resin bath. Instead, use the method I describe in the “what happens when my print fails” section above. The reason is simple: any spatula or other mechanical device (like a screw driver or knife) can put a hole in the very fragile FEP film. I’ve done it twice now (you’d think I’d learn after the first time!) Now, I never use the spatula for anything other than on the build plate. I haven’t damaged my FEP film since!

And while we’re on spatulas, use a plastic one. Never use a metal one. The AnyCubic Photon comes with one, and it’s quite effective. A metal one can score the build plate, where liquid resin can get trapped and cause issues. It may still print just fine, but it’s better not to have to find out that it doesn’t. The plastic will never damage the build plate, so you’re safe.

Use Spray Glass Cleaner To Clean Splashed Resin In Your Printer

Resin gets splashed inside the enclosure of your printer. When you’re first starting out, it’s very possible to splash or drip the resin inside the enclosure. As long as the drip isn’t on the UV screen on the bottom of the print area, it’s rather easy to clean up.

Remember, the resin is toxic and caustic, so be careful with it at all times. I know I mentioned this earlier, but it’s worth mentioning again. Use your nitrile gloves whenever you’re working inside the printer, even if there’s no visible liquid resin around. Save yourself the grief!

If you do splash or drip, wipe the spots of liquid resin with a paper towel sheet right away. If the drip is on the bottom of the inside of the printer, then this is especially important. Carefully remove the resin bath from the printer (even if it has liquid resin) and place it on a paper towel. Once it’s safe and stable, go ahead and wipe down the inside of the printer to clean up the spill.

It’s critical that a pool of resin not sit on or near the screen on the bottom of the print area. First, the resin residue will obscure the UV light that needs to shine to harden the resin for your models. Second, if the resin drips or seeps past the screen, it can damage or destroy the underlying circuit board. Luckily, this is a not-too-expensive replacement part, but why do it at all? Avoid this and clean spills as soon as possible to avoid that seeping.

For those minor spills or drips that leave a fine layer or small drip behind, it can be difficult to clean these. Once they’ve hardened (by exposure to light) then simple cleaners won’t budge them. Try a spray glass cleaner (like Sprayway Glass Cleaner, available on Amazon.Com). It can attack the hardened resin and give you a clean surface. It’s also safe for the screen for the UV light. Keeping that clean is critical.

But don’t bother if the drips or splashes are out of the way and unobtrusive. At this point, it’s a cosmetic cleaning. Sure, do it once in a while, but don’t obsess over these non-obstructing drips or splashes. For the AnyCubic Photon, for example, it’s harder to clean as the cover does not remove. You should wait until you’re not using the printer and you’ve emptied the resin bath and cleaned it. Then go ahead and clean the interior. For those with an Elegoo Mars printer, you can remove the cover and easily clean it completely separate from the printer. In that case, it’s personal preference as to when you clean it.

Shake, Shake, Shake Your Resin

When you add resin to your printer’s resin bath, shake your bottle (with the lid tightly closed, of course). Do this for 15 to 30 seconds, to ensure that it’s well mixed. The longer that a bottle of resin sits, the more it separates, with the lighter elements rising to the top of the bottle. You will get better prints (as intended by the manufacturer of your resin) if you shake the bottle. Otherwise, you’ll have thinner, lighter resin at the start of the bottle and heavier, thicker resin at the end of the bottle.

Shaking will introduce small bubbles into the resin. For those of us who’ve done resin casting by pouring time-curing resin into a rubber mold, then you will know that bubbles are the bane of good models. But that’s not the case here. The print plate will move into the resin bath to within one layer’s width from the bottom, and harden from there. The bubbles, however, being air, rise to the top of the resin bath. So your printing is happening away from where the bubbles are, so you’re quite safe. Don’t worry about the bubbles.

It is a good idea, however, to leave the printer for a couple of minutes after you pour a particularly bubbly mix of resin into the resin bath. This gives a good amount of time for the bubbles to rise to the surface and thus be away from where the printing is happening.

If you’re near the end of one bottle of resin, and you need to use a second bottle of resin to fill the vat, go ahead. It’s not a problem. Shake both bottles before adding the resin to the resin bath. If you’re mixing two different types of resin (you’re running out of transparent green and are going to add gray) then go ahead. I’ve had no issues mixing resins, but they’ve always been general purpose resin. I’m not sure what would happen if you mix resins of very different properties (like a general purpose resin and a flexible resin). That I haven’t tried.

Remove Supports Before UV Curing

At first, I would snip supports off of my models after I cleaned them and cured them. What I would find is that I’d need eye protection as snipping the supports with a side-cutter would send bits flying all over the room! I couldn’t find some of them. There’s likely bits of plastic in my bookshelves and behind furniture in my work area. Bits would fly everywhere!

One solution suggested by a friend is to clip supports with the model and the clippers held inside a one-gallon ziplock bag. The supports still go flying, but they’re contained by the bag. You can see what you’re doing, as the bag is clear, but I found that my hands were constrained too much for my liking. My eyes are bad enough, that I found the minor distortion of what I’m looking at through the plastic of the bag gave me some grief. I don’t want to cut off fine detail, just the supports!

Instead, I’ve settled on snipping supports after cleaning the model in Mean Green, then water, but before curing in UV light. The model is still wet at this stage, and the model and supports are much softer. You can clip the supports and they will either fall away or, more likely, just stick to the side of the model due to the water still on the model. It’s easy to just tap them off or use your side cutters as pliers and gently remove them for discarding. They don’t go flying around the room and it’s easier to cut thin or delicate pieces when the plastic is still soft. I have broken several models by clipping after curing, and a thin part will break off at the same time. I haven’t run into that at all with cutting supports between cleaning and curing.

Let The Light Shine In! – Curing Your Models

I cured the first models to come out of my printer overnight. After 8 to 10 hours, I removed from the curing chamber (UV strip lights inside of an unused paint can). Next, I tried only 4 hours of curing. It seemed to work just as well. Now, I’m finding that 30 minutes is all I need for most models, and 45 minutes for the biggest or bulkiest of models. Remember, you can’t get too big or bulky, as the build area of the home DLP resin printers isn’t that large. Still, a solid 5″ x 4″ x 4″ block would likely take longer to cure. My models are nowhere near that bulky, and in many instances, the walls are quite thin and cure very quickly.

You may need to do some trial and error to see what works best for your models. Start long and work your way back, perhaps starting at 4 hours. I’m sure you’ll find that you can get away with 30 minutes. Some on Reddit even suggest 10 minutes is enough time! I haven’t tried that short of a time frame yet.

If you’re curing out in natural sunlight, your curing times will be longer. My little paint can curing chamber puts a lot of 405nm UV light in a small space, with shiny sides for the light to bounce around. It accelerates the curing time dramatically. You may want to start with 4 hours again with natural light, but you may find that you can’t get anywhere near as short of a time as I’m experiencing. Remember that you can’t use daylight that shines through a glass window. Glass filters a lot of the UV light out of the light shining through, meaning it isn’t curing your model!

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