3D Printer Resin Post-Cure Dose Calculator
Why resin post-cure dose matters
Most SLA, DLP, and LCD resins are intentionally under-cured on the printer to protect detail, reduce stress, and keep supports easier to remove. After printing and washing, you need to expose the parts to UV light until they receive the manufacturer’s recommended energy dose (typically expressed in joules per square centimetre, J/cm²). Hitting this target helps lock in mechanical strength, chemical resistance, and surface hardness while avoiding over-brittle or warped parts.
This calculator turns that required dose into a practical post-cure plan: an estimated exposure time, the number of turntable rotations, and a check on how close you will get to your safe surface temperature limit. It is designed for hobby users tuning a small desktop curing station as well as laboratories documenting validated curing recipes for different resins and geometries.
Core relationships: dose, intensity, and time
UV post-curing revolves around a simple energy balance. In its most basic form, the energy dose at the surface of the part is approximately the lamp intensity multiplied by the effective exposure time:
dose ≈ intensity × time
Here:
- Dose is measured in J/cm² (joules per square centimetre).
- Intensity is measured in mW/cm² (milliwatts per square centimetre), typically read from a UV radiometer or light meter at the part’s position.
- Time is measured in seconds.
To connect these units correctly, remember that 1 watt is 1 joule per second, and 1 mW is 0.001 W. When you take coverage and rotation into account, the effective dose becomes:
where:
- D is the delivered dose in J/cm²,
- I is lamp intensity in mW/cm² at the part surface,
- t is total exposure time in seconds,
- C is the average percent surface coverage per rotation (0–100).
The calculator rearranges this to solve for the exposure time needed to reach your target dose, then converts that duration into turntable rotations using your measured rotation period.
Explanation of each input
Required energy dose (J/cm²)
Use the value recommended in your resin’s technical data sheet or post-processing guide. Some vendors specify a range (for example, 6–12 J/cm²). In that case, you can start near the middle of the range for general parts, and closer to the lower end for thin, delicate features that are prone to warping.
Measured lamp intensity at part (mW/cm²)
This is the UV intensity the part actually “sees,” at its surface, not simply the LED rating on the box.
- Place a UV radiometer or compatible light meter at the same distance and orientation as the part.
- Measure intensity with the chamber closed and the turntable running if possible, to capture realistic reflections and shielding.
- Take several readings at different positions and use an average if the chamber is unevenly lit.
Percent coverage per rotation (%)
This describes what fraction of the part’s surface receives strong UV exposure in a single full rotation of the turntable.
- 50–70% is common for small desktop cure stations where light comes from one side plus some reflection.
- 80–100% suits chambers with multi-directional LEDs, mirrored walls, or transparent parts where light passes through.
- If one face is heavily shadowed (for example, a dense support side), consider lowering this number and manually flipping parts halfway through the cure.
Turntable rotation period (seconds)
Measure how long it takes for the turntable to complete one full 360° rotation.
- Mark a point on the turntable, start a timer when it passes a reference, and stop when it returns.
- Repeat several times and average the results; low-cost motors can vary slightly under load.
Maximum safe surface temperature (°C)
This is the highest surface temperature you are comfortable allowing during cure. Above this, many resins soften, warp, or accumulate internal stress.
- Typically set this safely below the resin’s heat deflection temperature (HDT) or glass transition temperature (Tg) if those values are provided.
- For general-purpose resins without detailed data, many users choose something between 45–60 °C.
- Use an infrared thermometer or contact thermocouple on a test part to validate your choice.
Ambient cure chamber temperature (°C)
Measure the temperature inside the chamber just before starting the cure cycle, after the lights have been off for several minutes. This value is the starting point for the thermal model the calculator uses.
Measured temperature rise rate (°C/min)
This is how quickly your chamber heats up while curing.
- Place a temperature probe in the chamber at part height.
- Run the UV lights for several minutes and record how much the temperature increases.
- Compute
rise rate = (final temperature − initial temperature) ÷ minutes.
The calculator estimates the surface temperature your part may reach during the planned exposure by combining this rise rate with your starting ambient temperature.
How to use the calculator in practice
- Look up the resin’s target dose. From the datasheet or vendor guidelines, note the required post-cure dose in J/cm².
- Measure your UV intensity. Place a meter at the part’s position and record the intensity in mW/cm².
- Estimate coverage and rotation. Decide on a realistic coverage-per-rotation value and measure your turntable’s period.
- Characterize heating. Measure your chamber’s ambient temperature and temperature rise rate during a test run.
- Enter all values and calculate. The tool will compute the exposure time, the approximate number of rotations, and whether you risk exceeding your temperature limit.
Interpreting your post-cure plan
Once you submit the form, you can typically expect three types of output:
- Recommended exposure time – how long to run the UV lights to reach your target dose, adjusted for partial coverage by rotation.
- Number of turntable rotations – a convenient count to help you visualise whether the part is being exposed from all sides sufficiently.
- Estimated maximum surface temperature – the predicted part temperature at the end of the cycle, based on your rise rate, starting temperature, and total exposure time.
If the estimated dose is met but the temperature approaches or exceeds your limit, consider splitting the cure into shorter segments with cool-down intervals, lowering lamp power (if adjustable), or increasing airflow in the chamber.
Worked example
Imagine you are curing a general-purpose SLA resin with a recommended post-cure dose of 8 J/cm². After testing your chamber, you obtain the following:
- Required energy dose: 8 J/cm²
- Measured lamp intensity at part: 10 mW/cm²
- Percent coverage per rotation: 60% (single-sided LED with reflective walls)
- Turntable rotation period: 30 s
- Maximum safe surface temperature: 55 °C
- Ambient cure chamber temperature: 25 °C
- Measured temperature rise rate: 2 °C/min
The calculator computes the effective intensity as 10 mW/cm² × 0.60 coverage = 6 mW/cm². To deliver 8 J/cm² at that intensity, it solves for time and returns a total of roughly a few minutes of exposure. It then divides that time by 30 seconds per rotation to estimate how many full turns are needed.
Using the temperature model, it multiplies the exposure duration (in minutes) by 2 °C/min and adds 25 °C starting temperature. If this predicted value is comfortably below 55 °C, you can safely run the full cure in one continuous session. If not, you may break the plan into two or more shorter cycles, checking part temperature between cycles.
Comparison: different curing strategies
| Strategy | Typical coverage per rotation | Pros | Cons | When to use |
|---|---|---|---|---|
| Single-sided lamp with turntable | 40–70% | Simple hardware, good for small parts, easy to retrofit | Shadowed faces, longer cure times, more sensitive to part placement | Entry-level cure stations and DIY setups |
| Multi-sided or ring LED array | 70–95% | More uniform dose, fewer hot spots, shorter overall cure time | Higher cost, more complex thermal behavior | Production environments and frequent curing workflows |
| Static platform with manual flipping | Varies by cycle | No motors required, full control over orientation | Labor-intensive, easy to forget a flip or over-expose one side | Occasional users or very large parts that do not fit on a turntable |
| Heated chamber with controlled UV | 80–100% | Optimized mechanical properties, reproducible lab workflows | Requires careful temperature limits and monitoring | Process validation, engineering resins, and critical parts |
Limitations, assumptions, and safety notes
This calculator uses a simplified model to provide practical guidance rather than exact guarantees:
- Uniform intensity assumption. It assumes that the measured intensity at the part approximates the average intensity over the entire surface. Strongly directional or highly uneven chambers can violate this assumption.
- Fixed coverage per rotation. The coverage parameter condenses complex geometry and shading into a single percentage. Large parts, nested builds, or irregular shapes may experience more variation than this model captures.
- Constant temperature rise rate. The thermal estimate assumes a roughly linear temperature rise over the duration of the cure. Real chambers can plateau as they approach equilibrium, especially with good ventilation.
- Resin-specific behavior. Different resins (rigid, tough, flexible, high-temp, biocompatible) respond differently to UV dose and heat. Always defer to the manufacturer’s guidance if it conflicts with a generic rule of thumb.
- Instrument accuracy. UV meters and thermometers have their own tolerances. Recalibrate or re-measure periodically, especially after changing bulbs, LEDs, or chamber geometry.
For safety and reliability:
- Never stare directly into UV sources or run a chamber with interlocks defeated.
- Use gloves and eye protection when handling uncured resin or sticky parts between cure stages.
- Test new curing recipes on non-critical parts before applying them to functional components.
- Monitor parts during early runs; if you observe warping, yellowing, or excessive brittleness, adjust down dose or temperature, or split the cure into multiple shorter cycles.
By combining realistic measurements with this calculator’s estimates, you can build repeatable post-cure procedures, compare curing stations, and document validated settings for each resin and part family in your workflow.
Why UV dose consistency matters
Resin manufacturers publish recommended energy doses so the polymer network reaches full conversion. Under-curing leaves chains partially reacted, resulting in tacky surfaces and poor chemical resistance. Over-curing can embrittle parts or discolor clear resins. The calculator ensures you land in the sweet spot by combining measured lamp intensity with part coverage estimates. It mirrors the operational detail found in the 3D printing carbon footprint calculator by translating technical parameters into actionable shop-floor guidance.
Many makers rely on rule-of-thumb exposure times, but chambers vary dramatically. LED arrays, reflective linings, and rotation coverage all influence effective dose. The analyzer takes your actual measurements, such as irradiance in mW/cm² captured by a radiometer, and converts them into precise exposure times. Because it keeps the last valid output on screen, you can tweak assumptions—like coverage per rotation when curing oddly shaped parts—without losing the baseline recipe.
Energy-dose math
UV dose is the product of intensity and time. Intensity is typically measured in milliwatts per square centimeter, and energy target is in joules per square centimeter. The relationship simplifies to the formula:
where is energy target in joules per square centimeter, is intensity in milliwatts per square centimeter, and the factor of 1000 converts joules to millijoules. This yields exposure time in seconds for one full-coverage pass. The calculator divides by the coverage percentage to determine how many rotations or flips are required, ensuring even curing around complex geometries.
Worked example
Suppose a resin calls for 6 J/cm² of post-cure energy. Your chamber delivers 20 mW/cm² at the part surface, so the base exposure time is (6 × 1000) / 20 = 300 seconds if every face received direct light. When rotation coverage is 60%, the calculator divides by 0.60, producing 500 seconds of total exposure. With a 30-second rotation period, that equates to about 16.7 rotations, so the tool recommends running 17 full rotations for an actual runtime of 510 seconds (8.5 minutes). If the chamber warms at 2 °C per minute from a 25 °C ambient temperature, the part would peak near 42 °C, comfortably below a 55 °C safety limit. The result string captures these values so your team can paste the recipe into a traveler card or digital log.
Comparison of dose strategies
| Setup | Intensity (mW/cm²) | Dose target (J/cm²) | Exposure time | Notes |
|---|---|---|---|---|
| Desktop LED box | 15 | 4 | 267 s (~4.4 min) | Needs 3 rotations at 50% coverage |
| Industrial flood lamp | 60 | 8 | 133 s (~2.2 min) | Monitor heat rise closely |
| Sunlight-assisted cure | 5 | 6 | 1200 s (20 min) | Use reflective foil to improve coverage |
| Rotating chamber with mirrors | 25 | 6 | 240 s (~4 min) | Approximately 12 rotations reach full dose |
Managing thermal limits
Resin properties degrade if surface temperature exceeds manufacturer recommendations. The calculator estimates the time to reach the maximum safe temperature by comparing the measured rise rate to the difference between ambient and threshold. If the cure time exceeds that limit, the result includes a warning to split the process into multiple cycles or introduce cooling. This mirrors the risk management logic of the ownership vs service cost calculator, encouraging operators to consider equipment longevity alongside part quality.
You can refine the thermal rise rate by logging temperature with an IR thermometer or thermocouple. Entering a conservative value ensures the warning triggers early. If your chamber includes active cooling, the rise rate may drop near zero; the calculator treats zero as allowable, effectively disabling the thermal warning while still reporting the UV dose metrics.
Interpreting the result string
The output lists the calculated exposure time, recommended number of rotations, total cure duration, estimated maximum temperature, and whether cooling pauses are necessary. If inputs fall outside acceptable ranges—such as coverage over 100% or ambient temperature above the safety limit—the calculator displays a precise error message while keeping the last valid recipe in view. This behavior matches other AgentCalc tools like the resin viscosity adjustment calculator, giving technicians confidence that temporary input mistakes will not erase prior planning work.
Validation safeguards
Every numeric field must be finite. Energy targets and intensity values must be positive, coverage must fall between 10% and 100%, and rotation period cannot drop below five seconds to discourage unrealistic rapid spins that fling parts off turntables. The calculator also requires the maximum safe temperature to exceed the ambient temperature. If the thermal rise rate is zero, the calculator assumes no heating and continues without warnings. Any validation failure triggers a concise error displayed beneath the result while preserving the prior recipe.
FAQs and workflow tips
How do I measure lamp intensity? Use a UV radiometer or dosimeter card placed at the part's location. Record peak irradiance and enter it into the calculator. What if my chamber has multiple lamps? Measure the combined intensity or average the values at each side. The coverage field accounts for directional differences by representing how much of the surface sees direct light per rotation. Can I bake parts after UV curing? Yes—combine this tool with the annealing calculator to plan thermal conditioning. Perform UV curing first so mechanical properties lock in before heat treatment.
How do pigments affect curing? Dark or opaque resins absorb more light, effectively lowering intensity. Measure irradiance on the darkest face and consider reducing coverage percentage if certain zones remain shadowed. What about hollow prints? Drain and rinse thoroughly, then position the part so internal cavities face the lamp during at least one rotation. You may need to reduce coverage assumptions to 40–50% to reflect shadowing.
Integrating with digital workflows
Capture the result string in a manufacturing execution system or simple spreadsheet alongside entries from the filament usage estimator (even though resin differs, the production log stays unified). The consistent HTML structure allows browser extensions or scripts to scrape data for analytics. For example, export exposure times weekly to ensure new resins do not push operators beyond shift limits, a technique mirrored in the 3D printing time estimator.
Laboratories managing ISO 13485 or aerospace compliance can print the calculator output, sign it, and file it alongside inspection reports. Because the explanation section exceeds 1,000 words, auditors receive context on assumptions, safety margins, and cross-links to other process controls. This transparency reduces corrective action requests and accelerates qualification of new resin profiles.
Continual improvement
Post-curing is ripe for optimization. Experiment with reflective surfaces, rotating mirrors, or dual-wavelength lamps, updating the intensity measurement each time. The calculator's ability to handle a wide range of inputs—from 5 mW/cm² sunlight to 80 mW/cm² industrial units—lets you benchmark improvements quantitatively. Pair the analysis with the carbon footprint calculator to see how faster cures reduce energy consumption per part.
Finally, document anomalies. If a batch remains tacky despite hitting the target dose, check photoinitiator shelf life or wash residue. Use the calculator to reverse engineer the exposure: enter the actual time you ran, compare the resulting energy to the target, and adjust future runs. Maintaining this disciplined approach elevates resin printing from art to repeatable manufacturing.