Hey gang, Tim here at Core Electronics and today we're finding the optimal layer exposure time so we can make perfect resin 3D prints.

Exposure time is the length of time that UV light shines onto a single layer of a 3D printed model. This is a crucial parameter which when dialed in produces awesome crispy results that captures every single detail of an original 3D computer design. As a model can have potentially thousands of layers, there is no setting more important. Wrong exposure time is the major reason why resin 3D prints fail or are imprecise. Underexposing each layer results in serious loss and miniaturization of intricate details, delamination, weak spots and poor adhesion to the build plate. Overexposing results in light bleed which scatters UV light too far through the resin liquid resulting in fuzzy details, overbaked edges and dimensional inaccuracies.

It is all about finding that sweet spot. The best way to home in and find the correct exposure time for your particular resin and printer combo is to print exposure test models. The best starting point is the validation matrix. Printing these matrices are the master key to unlocking your optimal exposure setting. The goal here by altering the layer exposure time is to reproduce as accurately as possible this CAD model in real life. As a quick note, a download link for this model is available in the description.

Zooming in close into the STL, you can notice on the model that the two sides of the infinity sign perfectly touch in the middle. Also take note in the bottom section that the bars will fit perfectly if shifted down into the corresponding slots. On a correctly calibrated printer resin combo, these slots and bars can all be reproduced by a 3D printer. But the extreme edges of this section are so thin and delicate that they'll wash away during the IPA cleaning stage.

And finally, take note that there are several pins and voids on the left hand side that become increasingly smaller in diameter. By producing several 3D prints of these matrices with different exposure times, we can gain the best real life representation of this STL file. Once we have produced that optimal matrix, we have found our optimal exposure time.

Exposure settings can be adjusted beforehand in any slicing software. To do so in Lightsheet, by clicking on the 3D printer symbol and then clicking on this cog here, we have access to the exposure setting. For your first test, adjust the exposure time found under normal layers. A great starting number is using a 2.5 second exposure time. This is a good general number for both RGB and monoscreen printers. Note here that the default exposure setting that Creality has set is 3.5 seconds. Resin printers are usually shipped with an exposure setting too high on purpose. Do this so that your first print with this technology will basically be guaranteed to stick to the build plate, no matter what the initial resin is chosen.

Once we have printed, washed and cured this model with this setting, we will then adjust this number for the next matrix print based on the features seen in that printed model. So let's get into it by slicing this model just like normal and getting the printer running. We're going to talk about burn-in layers, also known as bottom layers, in just a second.

If you are instead using Chitubox, you can adjust the exposure settings here and you can slice your matrix just like this.

So I brought to the table many validation matrices that haveAll of the matrices shown here have been printed at different exposure amounts using the Creality LD002H UV 3D printer and the grey Creality resin. The top section of matrices have normal exposure times ranging from four seconds to one second, with a 0.5 second variation between them. This range would be suitable for testing a printer with an RGB LCD screen. However, to find the perfect exposure settings for a monochrome printer, it is worth running tests with a 0.1 second variation.

The lower section of matrices have exposure times ranging from 1.9 to 1.1 seconds for normal layer exposure. If you want to know which test piece has undergone the exact same post-processing and bottom layers, you can refer to the article for those specific details. Although it may seem like a lot of testing, this collection is very comprehensive and the models are thin and quick to 3D print.

For this particular resin and 3D printer combo, a normal layer exposure time of 1.7 seconds was determined to be perfect. Let me zoom in on this specific matrix and explain the conclusion. A perfect exposure time is indicated when the two halves of the infinity sign in the middle perfectly touch. Additionally, the majority of bars in the bottom section should fit perfectly if shifted into the corresponding slots. Lastly, the number of pins and voids on the left-hand side should be equal.

In the matrix produced using a 3.5 second normal exposure setting, you can see that the infinity sign in the centre overlaps. This model also has more pins than voids, and the bars do not fit into the corresponding bottom slot sections. This is the stock exposure setting that this model of Creality resin printer shipped with.

Now let's zoom in further. In this closed-caption transcript, we can see a discussion about an underexposed matrix and its effects on 3D printed models. The matrix was created using a 1-second normal exposure setting. One obvious sign of underexposure is blemishes on the model, where certain sections appear shinier. This occurs when the UV light from the printer is not strong enough to cure the resin properly, resulting in sticky and tacky resin that sticks to the surface of the part. This type of resin is difficult to remove during the IPA wash and does not create good surface features.

Additionally, the underexposed matrix displays fewer pins than voids on the left side, and the bars have extra space in the bottom gap sections. In severely undercured examples, there may be an empty gap between the infinity sign in the center. Undercured parts have weak spots that can lead to failures, and completely underexposed models may fall off the build platform.

The bottom layers of a 3D printed model are the first few layers exposed to UV light. The exposure times for these bottom layers are always longer than the normal layer exposure times. This is done to ensure that the model adheres securely to the build platform. A general rule of thumb is to have 6 to 10 bottom layers, with the bottom layer exposure time set to be 10 times longer than the optimal normal layer exposure time.

In the specific case mentioned, where a 1.7-second normal layer exposure time was found to be optimal, a 17-second bottom layer exposure time would be recommended. However, it is important to note that it is always best to test the normal layer exposure for your own printer and resin combination. Relying on someone else's results can lead to issues. Be in a different climate, or your printer could have some quirks, or the resin batches might be slightly different. Other people's settings are a great starting point and will save you producing heaps of test matrices, but fine-tuning with those test prints is how you get your exposure settings perfect.

Exposure settings can be adjusted beforehand in any slicing software worth its salt or directly through your 3D printer. On Creality machines, this can be done by clicking on the cog in the bottom right of the touch screen. Then by clicking on each of the numbers, you can change or alter the exposure time, the bottom exposure time, and how many layers of bottom exposure.

Validation matrices are great for checking two-dimensional accuracy, but won't supply you with knowledge of a couple of details. To make sure overhanging features and overall model stiction to the build platform is still occurring, your best procedure is to print a more three-dimensional test object. The best model to do this is the Make Rook calibration chess piece. This model has heaps of overhangs from the double helix in the center to the outside walls and internal staircase structure.

You can verify the settings found from the validation matrix by accurately printing this Make Rook model with all the text clear and legible and that the overhanging structures are sharp and unbroken. Once you achieve that, you are good to print your dreams. My dreams consisted of a Gengar with a very special little filigree all around his body. All of that crispy filigree has printed really, really well. The optimal exposure time changes whenever you use a new printer, whenever you fill a tank with different resins, or whenever you place contaminants to colorize the resin, every time you change your layer height, and even over the lifetime of your resin printer. So it is good practice to run off some of these test pieces in all of these occasions.

All the models talked about here, as well as some other great test models, can be downloaded from the article page linked down below. It is worth noting all of these tests have been done for a single location in the centre of the build platform. Depending on the quality of the 3D printer, the power of the UV light hitting the resin can be weaker the further you go away from the centre of the build platform. Thus, it is worthwhile to run some test prints along the extremities of your build platform to see if there is any degradation of quality.

Also, whenever producing these test parts, to save confusion, make sure to write down on the model itself the settings you use to print them, much like I have done here. With my printers here pumping out crispy, beautiful models, I hope I have provided you with all the information to do the same. So until next time, stay cozy.