Quicklinks: Overview, Calibration Tests, Slicer Settings, Troubleshooting, Bottom Exposure, Environmental Factors, Additional Resources
Overview
Resin 3D printing (MSLA, SLA, DLP) is an additive manufacturing technology that utilizes photopolymers that when exposed to UV light will harden individual layers or slices in order to build on itself forming a three dimensional object.
Exposure Time is the duration of time the light source is emitting UV light to cure resin per sliced layer.
This is arguably one of the most important parameters for resin 3D printing and is one of the most common sources of print problems for resin printing.
While many companies and communities have recommended exposure time settings for your printer experience. Finding your exposure time for your unique environment will both give you confidence to experiment with new things and understand when and how your settings should change.
Exposure time can vary and be influenced based on several factors:
- Temperature
- Resin Color & Opacity
- Screen Type (Mono vs RGB)
- Resin Brand
- UV Power
- Layer Height
- other setting influences
So the leading question is “What does proper exposure look like? And how do I tell if I’m properly exposing my model?”
Signs of ideal exposure will successfully produce your print with a strong bond between the individual layers of the print without over curing or thickening details resulting in the loss of detail. The trick is to dial in your exposure time, using different calibration tests. In order to know if you are over or under exposing, read on to see signs and symptoms outlined in the exposure troubleshooting section.
Exposure Test Calibrations
So how do you determine your exposure time? In this hobby there are several different types of exposure calibration tests to choose from each with their own strengths and weaknesses.
UVTools Exposure Time Finder
UVTools GitHub
How to Read test Github Writeup
| Advantages | Disadvantages |
|---|---|
| Only test to allow test of multiple exposure times at once | Very small to see with naked eye, suggested use with camera |
Where To Find Exposure Time Settings in Your Slicer?
So now that we have talked about exposure times, where do we find exposure times in our slicer software? Below I have pictures of where to find this setting on three of the most popular resin slicing software: Chitubox, PrusaSlicer and Lychee. Note that all slicers denote exposure time as the same thing but bottom exposure can be referred to as burn in layers, initial exposure time and bottom exposure time.
Troubleshooting
When looking for guidance in resin 3D printing one of the most commonly suggested solutions would be to modify your exposure time. However how do you know that your real issue is revolving around exposure time? What does over exposure or under exposure look like? Below are some of the common issues associated with exposure time.
Signs of To Little Exposure
Some of the most prolific issues related to resin (SLA, MSLA, DLP) 3D printing is due to improper exposure and or more commonly too little exposure time. These issues commonly manifest as delamination, loss of intricate details, poor model adhesion to supports or build plate, and model flattening commonly referred to as pancaking.
Delamination
Delamination occurs when layers of your model do not properly bond to each other resulting in layer separation. This can be in all or only a portion of a print. This issue might also not be immediately apparent but can be worsened during the post print cleaning and curing.
Flattening “Pancaking” of the model
One of the most common issues resulting from under exposure would be partial failure of the model. You can observe this where portions of the model go flat. It can also result in regions of the model missing from the model entirely such as a leg or arm. If you have this occurring make sure portions of cured resin are not floating around in the vat of resin which could lead to other issues.
Supports vs Exposure: Pancaking can also sometimes be an indication of too little supports in that area, especially for fine detail areas. How do you tell the difference? If you are printing a large build plate of models and only have a small area of pancaking it could be due to supports. If the issue occurs across multiple models on the build plate exposure could play a larger factor.
Still unsure? If printing presupported models check the community to see if others have the same issue on that model. If repeated across multiple members of the community this could also be an indication of too little supports.
Models Pulling from Supports
In other situations of under exposure, supports do not form a strong enough attachment or fully form which results in models pulling from the supports entirely resulting in the print stuck to the FEP or partially formed and hanging from supports.
This also could be an indication of too little supports as well as exposure. Some solutions would be to increase exposure time or add more supports to the model.
Detail Not Printing
Under exposure will also result in detail missing all together. This is due to the detail of the model not being provided ample time to form and solidify. This is most often seen in 3D printing raised text or thin details.
Signs of To Much Exposure
When a 3D print has too much exposure several issues can occur. The most visual example of over exposure is that detail on the model will “overflow” which will obscuring it or loose the detail entirely. Also with too much exposure supports and details can thicken resulting in fusion of supports to model where they would normally have clearance. Supports will also form extremely hard adhesion points between the model and its supports leaving damaging marks on the model and require the use of a cutting tool.
Support Damage/ Difficulty Removing
This is an example where the tip of the support adheres significantly to the model itself resulting in pot marks into the model or pieces of remaining supports which need to be shaved and sanded down. While this issue can from using thick tipped supports over exposing can aggravate these issues.
Loss of Detail
Over exposure will also result in detail being lost on the model especially in intricate details such as cords of rope or engravings as shown in the cauldron below.
Support Fusion & Loss of Clearance
In some cases with over exposure the supports themselves can fuse against the model. This is different than support damage as the sides support trucks can be touching and form alongside the model. In some cases a support would have clearance to avoid printing on the model but due to overexposure the support will increase in diameter enough to form into the model.
Bottom Exposure Time
How does bottom exposure time influence your print? What is the relationship of bottom exposure time vs regular exposure time?
Bottom exposure or Burn in layers refers to the time set for the initial layers of your print. These layers are those that would form against the build plate and securely hold the entire print during the build process. Bottom exposure time will typically be 6 to 10 times the duration of your normal exposure time. If your bottom exposure time is too low you commonly will have issues with models even attaching to your build plate and have the model stuck the FEP. If bottom exposure is too high it could be difficult to remove the model from your build plate.
Environmental Factors on Exposure Times
So after spending all the time calibrating your exposure time did you know other factors could cause you to have to modify your exposure time settings? The most common one is temperature and may hobbyists have to increase their print time during the colder months to account for temperature decrease in their printing areas.
Some variables to influence exposure times:
- Ambient Temperature
- Resin Color & Opacity
- Screen Type (Mono vs RGB)
- Resin Brand
- UV Power
- Layer Height
- other setting influences
Additional Resources From the Community
Optimal Layer Exposure Time For Perfect Resin Prints by Core Electronics. com
How To Get The Perfect 3D Printer Resin Settings Quality by 3Dprinterly.com
If you have a favorite resources do not hesitate to comment down below for it to get added to the list.
Still Have questions?
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