A spot-cure recipe copied from a data sheet tells you where to start, not where to run. A dose window shows the range of settings that produce good bonds on your parts, so you can pick a production setting with room on both sides.
Q: How Do You Establish a Reliable Dose Window for a UV Spot Cure?
A: Run a Small Test Matrix of Time, Intensity, and Distance, Judge Each Cell Against Pass/Fail Tests, and Lock the Center of the Passing Region
The method below uses three variables, a defined set of tests, and a written release step. It works with either an LED or an arc spot lamp, and it turns cure settings from a guess into a documented process.
Step 1: Define What “Pass” Means Before Testing
Agree on acceptance criteria first, so results are judged the same way every time. Typical criteria for an industrial bond include:
- Mechanical strength: a pull, shear, or push-out test on the real joint, against a minimum you set from the part’s load requirement.
- Surface state: no tack or soft film on the exposed adhesive.
- Through-cure: the material against the substrate is as hard as the surface when sectioned or peeled.
- Part condition: no warping, discoloration, or movement of the components.
- Durability: strength retained after the environmental exposure the part must survive, such as thermal cycling.
Record the criteria and the test method on one sheet before any parts are made.
Step 2: Choose the Three Variables and Their Levels
Dose equals irradiance multiplied by exposure time, and irradiance depends on intensity setting and working distance. Those three settings are the matrix.
On Incure’s L9000™ UV LED spot lamp, use the published irradiance curve to choose distance levels: 5,000 mW/cm² at 10 mm, 2,300 mW/cm² at 17 mm, and 1,200 mW/cm² at 20 mm. Intensity adjusts from 10% to 100% and the timer runs 0.1–999.9 seconds. On Incure’s S20™ arc spot lamp, intensity adjusts from 25% to 100% with a 1–99 second timer.
Pick three levels of each variable that bracket the data sheet’s recommendation, one below, one near, and one above.
Step 3: Turn the Data Sheet Dose Into Starting Times
Take the adhesive’s required dose from its data sheet and divide by the irradiance at each distance. As a hypothetical example, suppose a data sheet calls for 3,000 mJ/cm². At 100% intensity on an L9000™:
| Working distance | Irradiance | Time for 3,000 mJ/cm² |
|---|---|---|
| 10 mm | 5,000 mW/cm² | 0.6 s |
| 17 mm | 2,300 mW/cm² | about 1.3 s |
| 20 mm | 1,200 mW/cm² | 2.5 s |
These are arithmetic starting points only. Measure irradiance at your own bond plane with a radiometer and use that figure, since your guide and fixture define the real value.
Step 4: Run the Matrix on Real Parts
A full three-by-three-by-three matrix is 27 cells, which is often more than needed. A practical approach:
- Fix distance at your intended production standoff.
- Run a three-by-three grid of intensity and time.
- Build several parts per cell and test them against every criterion from Step 1.
- Repeat the best row at one closer and one farther standoff to see how sensitive the result is to fixture drift.
Label each part with its cell so results can be traced. The L9000™ working-distance guide helps when choosing which standoffs to test.
Email Us with your adhesive data sheet and part drawing, and Incure’s team can help lay out a test matrix for your bond.
Step 5: Map the Window and Find Its Center
Mark each cell pass or fail. Two edges usually appear:
- A low-dose edge, where bonds show tack, soft interiors, or low strength.
- A high-dose edge, where parts show heat effects, discoloration, or stress.
The passing region between them is the dose window. Choose a production setting near its center, so that normal variation in standoff, guide transmission, or source output stays inside the passing region. A setting that sits right at the low-dose edge will fail as soon as anything drifts.
Step 6: Lock and Document the Recipe
Once the center is chosen, write the controlled recipe:
- Lamp model, wavelength, and guide configuration.
- Working distance and how the fixture holds it.
- Intensity setting and timer value.
- Measured irradiance at the bond plane on the release date.
- The pass/fail criteria and the results that justified the setting.
- The recheck interval for irradiance, and the reading that triggers investigation.
Restrict changes to that recipe and require a partial re-run of the matrix after any change to adhesive, guide, fixture, or lamp.
Keeping the Window Valid
The window describes your process on the day it was measured. Guides can lose transmission over time, as covered in what causes UV light guide degradation over time, and arc lamps age toward replacement. Periodic radiometer checks against the release reading show whether the process is drifting toward an edge. For the system fundamentals behind dose and distance, see Incure’s explainer on how a UV LED spot curing system works.
Final Thoughts
A dose window replaces a single remembered setting with a mapped, documented range, and running at its center keeps production away from both failure edges. Contact Our Team to develop and document a spot-cure recipe with Incure.
Visit www.incurelab.com for more information.