Why Are Bottom Layers Overexposed in Resin Printing? Understanding the Five Factors

In resin printing, sometimes the print results are not ideal, and some printing problems can prevent the user from getting an accurate model. A common challenge faced by users of resin printers is overexposing the bottom layer. Overexposure of the print creates an "over-curing" phenomenon that can lead to a number of problems such as over-hardening of the resin. In this tutorial, we will explain the concept of exposure, discuss the reasons for overexposure of the bottom layer, and provide effective methods to help you reduce the possibility of overexposure of the bottom layer and obtain better printing results.


Understanding Overexposed Bottom Layers

What is the bottom layer? In resin printing, the bottom layer is the initial layer of the print that adheres directly to the build platform. When slicing, we need to set the number of bottom layers to provide sufficient thickness and strength to secure the print to the build platform. The number of bottom layers is not fixed and can be adjusted according to the printer model, resin type, print size, etc. Usually, 5 layers or more are set.

Bottom Exposure Time

In the process of resin printing, the resin needs to be cured layer by layer, and the time for each layer to be exposed to the UV light source is the exposure time. Set the proper exposure time to cure the resin properly, it will avoid overexposure and underexposure issues. The exposure time of the bottom layer refers to the exposure time specially set for the bottom layer. Usually, it is different from the normal exposure time setting, and the bottom exposure time is longer, because it needs to adhere firmly to the build platform to improve adhesion and stability, and avoid prints from falling off.


Underexposure and Overexposure

If the number of bottom layers is set too few, or the exposure time is set too short, it cannot meet the adhesion of a large-sized model, for example, there is a risk that the model will fall off and the print will not be completed. If the bottom is overexposed, it may prevent subsequent layers from bonding properly, which can lead to printing problems or print failure. Overexposure can cause the resin to harden more than expected, increasing the brittleness of the underlying layer and making it prone to breakage. Even more problematic, it becomes difficult to remove the over-hardened print from the build platform.

Why Are Bottom Layers Prone to Overexposure? Five Factors

Exposure time

Resin manufacturers usually provide recommended settings for their resin-specific number of bottom layers and exposure times. If the exposure time for the bottom layers is set too long, this can lead to overexposure.

Insufficient layer thickness

If you set a very thin printing layer thickness, it will easily lead to overexposure.

Light source intensity

Higher UV light source intensity means the ability to cure the resin faster. For some darker resins, higher UV power is suitable, but in the case of highly translucent resins, this may result in not curing the material properly, such as overexposing the bottom layer.

Support structures

3D printing often uses structures to support the overhanging parts of the print. When there is a problem with the design of the support structure or the positioning is not correct, it may cause overexposure in some areas and become an inducement for overexposure of the bottom layer.

Printer leveling

It is possible that the resin printer is not leveled, or needs to be leveled again. An uneven build platform will lead to uneven layer thickness in the actual printing process, resulting in inconsistent exposure or overexposure of the bottom layer.


For the problem of overexposure of the bottom layer, five common causes are given above, which can help you understand and troubleshoot this problem. To reduce the trouble of overexposure, we usually adjust the bottom layer exposure time and re-leveling the machine to correct the problem. For the exposure time required by different resins, you can refer to the official recommendations and conduct an exposure test. With these precautions and printing adjustments, you can reduce the possibility of overexposure of the bottom layer and regain good printing results.

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