Chapter No.1 - Setting Parameters of Resin Printing by Edoardo De Monte

AUTHOR INTRODUCTION

Hi! I’m Edoardo, an engineer from Italy. I’m a miniature painter and I also build and paint planes and sci-fi models in different scales. 3 years ago, I started my journey in the 3D printing world as a hobbyist and, also thanks to my background, I gained a lot of experience in 3D printing.

This is the first of a series of posts about resin 3D printing: these posts will be about the most common problems of this process, how to solve them and thus improving the 3D printing experience. We all want to create perfect prints, in fast time and without problems. But not all of us have the time or the technical information to build up our own knowledge going through a lot of testing. This is why I want to write these posts, to help people obtain great results from their printer by sharing the knowledge I have acquired through these years.

I’ll try to make these articles accessible to everyone, from the beginner who just bought his/her first printer and resin, to the most skilled professional 3D printer that needs to print faster. I really hope that you’ll enjoy my work and find it useful to make 3D printing easier and funnier.

I want to thank Aceaddity for giving me the possibility to spread my knowledge through their platform. It’s a very good company that not only provides high-quality products at an affordable price, but also cares a lot for their customers.

 So, let’s start this journey with the first thing to do when the new resin arrives: settings calibration.

Chapter 1 PRINTING PARAMETERS

Settings and their meaning

The first thing to understand to calibrate correctly the printing parameters is to know what each parameter does and how it influences the printing result. Once you know this, you’ll be able to independently modify the settings following your personal needs.

• Layer height:

This is the height that each layer has, and it can be measured in millimetres [mm] or microns [µm]. 10µm = 0.01mm. This parameter controls the overall printing speed in mm/hour as determines the number of layers in which the object is divided: the more the layers, the higher the printing time will be.

It also determines the quality of the prints because increasing the layer height will lead to more visible layer lines. I mainly use 3 different thicknesses: 25 or 30 µm for little and high-quality prints, 50 µm for bigger prints to balance printing time and quality, and 100 µm for very fast printing without surface quality requirements.

• Bottom layer count:

The number of layers at higher exposure time that will be responsible for the object adhesion to the printer plate. The number I suggest using is to have about 0.2mm of a solid and well-attached base, so it depends on the layer height: 2 layers at 100µm, 4 at 50 µm and 6 at 30 µ More bottom layers are useless for the adhesion but will only increase the difficulty to remove the print from the plate and the risk to overheat the screen.

• Exposure time:

The UV exposure time of each normal layer. This parameter depends on a lot of factors. The main are, first of all, resin type and manufacturer, 3D printer, layer height, ambient temperature and printing speed. In this article we will consider having an unknown 3D printer and resin brand and to only adjust the time depending on the layer height: in this way we’ll create a repeatable process that can be controlled to calibrate the parameters.

• Bottom exposure time:

The exposure of the bottom layers that must be higher in order to grant the necessary adhesion to the build plate to keep the object attached to it during the entire process. I suggest it to set it to 5-8 times the normal exposure time. More time will only make the prints harder to remove from the plate, less won’t be enough and the objects will detach from the plate while printing.

• Transition layer count:

These layers are responsible for the transition of the exposure time for the bottom layers to normal exposure time to avoid the creations of a sudden change in layer exposure and thus layer delamination. I usually set it to 5 for every layer height.

• Resting time:

The time the plate pauses in different moments of each layer printing process. It can be set as a “light-off delay” mode (= the total time the plate stays still from the start of the exposure) or “resting time” mode. I prefer the second one because it’s easier to understand and to control. This option is divided in 3 resting times:

1. Rest time before lift: the pause time between the end of the exposure and the raising of the plate after the exposure ends. In general, this time can be set to 0 as it has no impact in print quality.
2. Rest time after retract: the pause time between the end of the raising movement and the start of the retract phase. It happens when the plate is mid-air, so it has no influence in the process except for increasing the total print time. Thus, it can be set to 0.
3. Rest time after retract: the pause time between the end of the retract movement and the start of UV exposure. It happens when the plate is still in the bottom position and it’s the most important rest time for high quality prints because it prevents the blooming phenomenon (= visible horizontal lines due to the squeezing of the resin during the lowering of the plate). As the resin is viscous, it takes time to stop it’s flowing after the plate has stopped the lowering and so it’s necessary to set it at least at 0.5s, better at 1s if you want perfect prints. This allows the resin to stop flowing after the retract movement of the plate so that, when UV exposure starts, the resin will be still and ready to be solidified.

• Lifting and Retract distances:

The distance that the plate travels during the movements of lift and retract. These are responsible, respectively, for the complete detachment of the printed object from the FEP (lift) and the plate lowering to position at the correct distance to start the exposure (retract). The minimum distance required must be set in order to make sure that the printed object is fully detached from the build plate. As a starting point, we can set it to 6 mm. In further posts I’ll discuss how to minimize it for faster printing.

• Bottom Lifting and Retract distances:

Same as the previous, but for the bottom layers. As they are exposed longer and so are attached more to the FEP, we can set it to a higher value of 8mm.

• Lifting and Retract speeds:

The speed of movement during the homonymous movement phases. If too high, it will lead to the tearing of the object from the supports; if too low, it will increase the printing time without benefits. As a starting point, it can be set to 90 mm/min for the lift and 180 mm/min for the retract.

• Bottom Lifting and Retract speeds:

Same as previous, but for the bottom layers. As they are exposed longer and so are attached more to the FEP, we can set it to a lower value of 60mm/min for the lift and maintain 180 mm/min for the retract.

• Anti-Aliasing:

The settings that dims the pixels on the edges of the printed object to make the voxel lines disappear. The voxel lines are the signs of the pixels, which are more visible in smooth and curved areas. For the calibration, it is better to disable it to evaluate better the exposure as this setting doesn’t influence the resin. Once the other parameters are tested and confirmed, the AA can be evaluated to define its optimal level.