Swapping a mercury arc spot lamp for an LED unit looks like a hardware change. In practice it is a process change, because the light reaching the adhesive is different in spectrum, intensity, and behavior across a shift.
Q: Can You Replace a Mercury Arc Spot Lamp With an LED Spot Lamp Without Requalifying?
A: No. The Adhesive Must Be Requalified at the LED’s Single Wavelength, and the Cure Recipe Rebuilt From New Measurements
A mercury arc lamp spreads output across a wide spectrum. Incure’s S20™ arc spot lamp covers 275 to 650 nm, and standard mercury bulbs have strong peaks at 254, 313, 365, and 405 nm. An LED spot lamp emits one narrow band. Each Incure L9000™ unit is factory-set to 365, 375, 385, 395, or 405 nm. An adhesive that cured well under the broad arc spectrum may have relied on bands the LED does not produce, so cure must be proven again. Incure’s UV LED spot curing system overview covers the LED hardware; this guide covers the transition.
Step 1: Confirm the Adhesive’s Absorption Band
Start with the adhesive, not the lamp. Ask the supplier which wavelengths the photoinitiator package responds to, then choose the LED wavelength inside that band.
Because the L9000™ wavelength is fixed at the factory, this decision happens before the order is placed and cannot be changed on the floor. Some families make this straightforward: Incure’s Uni-Weld™ plastic bonder grades cure across 365–405 nm, while the Uni-Weld™ glass and metal bonder line is documented as typically curing at 365 nm. If a station currently cures several adhesives under one arc lamp, check every one of them; a single LED wavelength may not suit all of them.
Step 2: Measure the Old Process Before Removing It
The existing arc process is the only reference you have, so record it before decommissioning anything:
- Irradiance at the bond position, with the radiometer and jig you will use going forward
- Exposure time and controller intensity setting
- Lightguide type and the distance from tip to part
- Cure results on retained parts: strength, appearance, and any functional test
Note what the radiometer actually reads. A meter’s response may not cover every band an arc lamp emits, so treat the arc reading as a site-specific reference rather than a universal number.
Step 3: Translate the Recipe, Then Prove It
Do not copy the old exposure time. Rebuild it from dose: exposure time equals the adhesive’s required dose divided by the LED irradiance measured at the bond.
The L9000™’s irradiance depends steeply on distance, from 7,500 mW/cm² at a 9 mm focal point to 1,200 mW/cm² at 20 mm. As a hypothetical example, a bond needing 2,400 mJ/cm² at 20 mm would need 2,400 ÷ 1,200, or 2 seconds, as a starting point. That number is only a starting point: run cure trials at, above, and below it, and confirm properties on parts.
The controls translate differently too. The S20™ adjusts intensity from 25% to 100% with a 1–99 second timer; the L9000™ adjusts from 10% to 100% with a 0.1–999.9 second timer. Recipes can be set more finely on the LED, which helps when the new exposure time is short.
Email Us with your current arc settings and adhesive, and Incure’s engineers can help plan the requalification runs.
Step 4: Check Lightguide and Fixture Compatibility
The guide changes along with the source. The S20™ uses liquid lightguides in 1- to 4-pole configurations, while the L9000™ pairs with its own guides: the 83 mm Cool Guide, the 66 mm Short Guide, and the 118 mm Long Guide, with up to four guides per controller. Confirm that the new guide length reaches the bond in your existing fixture, and that the tip sits at the distance you qualified. Incure’s guide to what a light guide does in a spot lamp system explains why this matters.
Accessories may need review as well. Incure’s LS217™ lightguide simulator fits mercury arc, xenon, and halogen spot lamps but not LED units, so lightguide monitoring on the LED line moves to working-distance radiometer checks.
What Changes on the Line
Several daily routines change once the LED is running:
- No warm-up. The S20™ needs 1 to 2 minutes to reach full output and a cooldown before restart. The L9000™ fires at full intensity from the first trigger.
- No scheduled bulb changes. Arc bulbs are commonly replaced every 1,000 to 2,000 hours, with about 30 minutes of cooling before removal. The L9000™ is rated for 15,000 hours with less than 20% intensity decay, and the LED module is replaced at end of life.
- No periodic calibration returns. The L9000™ is calibration-free across its rated life.
- Automation stays available. The L9000™ supports PLC-triggered activation over RS-232.
- Eye protection stays. UV exposure at curing intensities still calls for certified eyewear such as Incure’s Vison™, rated to block 99% of UVA, UVB, and UVC.
Update the Documentation
Treat the migration like any process change. Revise the work instruction with the new wavelength, distance, intensity, time, and measurement method. Record the new baseline readings, archive the arc settings, and decide whether retained parts from both processes should be kept for comparison.
Final Thoughts
Moving a spot cure from mercury arc to LED removes warm-up and bulb changes, but it narrows the spectrum to one band. Requalify the adhesive at that band, rebuild the recipe from measured dose, and confirm the guide fits the fixture. Contact Our Team to plan an LED migration with Incure’s spot curing equipment.
Visit www.incurelab.com for more information.