Optimal Layer Exposure Time for Perfect Resin Prints

Heyya all, just put the finishing touches on the guide Optimal Layer Exposure Time for Perfect Resin Prints

Understanding exposure test models means you can nail the exposure time for your printer-resin combo. This is the secret to producing crispy 3D prints that capture every single detail of the original design. Layer Exposure Time determines the light exposure duration for a single layer of an object that you are trying to print. Unlike filament printing (where it can feel like there is an almost endless amount of settings that you must know about for perfect 3D prints) resin 3D printing machines have much simpler dials to adjust up and down. And the most crucial dial is Layer Exposure Time and its wrong adjustment is one of the major reasons why resin 3D prints fail. This guide teaches you exactly how to find this exposure time using test models like the Photonsters Validation Model and the Make:Rook Chess Piece. STL download link for these models found in the article.

As a general rule for Normal Layer Exposure Time use 0.5-5 seconds for Monochrome Screen Printers and 2-20 seconds for RGB Screen Printers. Another good rule of thumb to follow is to set the Bottom Layer Exposure Time to be 8-12 times longer than the Normal Layer Exposure Time. This is good generally but make sure to keep the bottom exposure time lower than ~30 seconds.

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Hi (sorry for my inglish who is very bad). I have a question how to print the validation matrix and what factors to change. since being such a low piece, I don’t know if it will be altered by lower or normal exposure values. Thanks in advance.

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Hi. I just asked a question and I forgot to add this other question: I don’t know if my printer (LD-002R) has an RGB or monochrome screen. If anyone knows or can tell me where to see that I appreciate it.

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Heyya mate,

You have almost perfect English, the Creality LD-002R LCD Resin 3D Printer has an RGB Masking Screen. The full written up article has all the setting you need to print a Validation Matrix (check the third paragraph of the Decoding the Best Layer Exposure Test Print section. The only real complexity is to use 4 Bottom Exposure Time Layers. With every other model I Resin print I normally use ~10 Bottom Exposure Time Layers.

Hope that helps,
Tim

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Hi Tim,
Just to be 100% clear… you print this calibration model (and other stuff) flat on the build plate? I haven’t tried this model yet, but other things I’ve tried I’ve had trouble doing this, but found that printing at 45 degrees works (mostly). I did some reading and I think this is what’s described as a “suction cup” issue?

Also, in your Layer Heights Guide you say exposure time increases with increasing step height, but not by how much. If I have a perfectly calibrated 10 micron exposure time, would a good starting point for the 20 micron exposure time be about 1%, 10%, 20%, 50% more (assuming all else remains the same)?

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Heyya Frank,

Absolutely I print these calibrations directly and flat onto the Build Platform. Zero support is needed and 4 Bottom Layers.

I have heard reference to ‘Suction Cup’ issues mainly in Resin 3D prints that are hollow. For these 3D prints, it is preferable, during the CAD or slicing stage, to have holes in the design to prevent a Negative Pressure Vaccum from building up inside the Hollow sections. Managing this correctly will increase the longevity of the FEP sheet and produce consistently successful prints. This is a topic I mention briefly in the guide Preparing a CAD file for Resin 3D Printing.

Exposure Time definitely increases with increased step height however in my experience it isn’t a linear increase in time. Light scattering through a material is wonderfully easy to visualise in one’s head and yet deceptively complex once you start pinning accurate Mathematical Equations to it. For a general rule of thumb - each time you double the Layer Height I would ballpark a 20% increase in Normal Exposure Time. I would then confirm this result with testing as outlined in the Optimal Layer Exposure Time for Perfect Resin Prints.

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Thanks for that. I didn’t get a calibration card with my printer so followed the previous owner’s advice to “just use the FEP film to calibrate”. Which of course was totally wrong since it leaves no space between the film and build plate for the resin. Now I’ve leveled it a couple of paper thicknesses higher I can print things flat on the plate. :smiley:

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Hello, I was wondering if the dimensions of the test calibration squares are important?

Hello,

It is a pretty important thing to print them at the recommended size for your printer. Some printers may have alternate sizing for test squares though this particular provided square is designed to be printed by these dimensions to provide accurate results.

Cheers,
Blayden