The lamp choice in spot curing usually comes down to a question about chemistry rather than hardware: does the adhesive’s photoinitiator absorb where the lamp emits? Answer that first, and the arc-versus-LED decision largely makes itself.
Q: When Does a Broadband Arc Spot Lamp Make More Sense Than a UV LED Spot Lamp?
A: When the Adhesives in Use Are Mixed, Unknown, or Absorb Outside a Single LED Wavelength
A broadband arc source covers a wide range of photoinitiators at once. A narrow-band LED source is the stronger fit when one adhesive, with a known absorption band, runs on a dedicated station. Most labs and multi-product lines sit somewhere between those two cases, which is why the decision deserves a structured look.
What the Two Spectra Actually Look Like
Incure’s S20™ UV arc spot lamp uses a 200W mercury arc and emits across 275–650 nm, spanning ultraviolet into visible light, with peak output above 21 W/cm² (up to 23 W/cm²) at the lightguide tip. Standard mercury arc bulbs show strong peaks at 254, 313, 365, and 405 nm, so a single source reaches several absorption bands.
Incure’s L9000™ UV LED spot lamp emits a narrow band at one factory-set wavelength: 365, 375, 385, 395, or 405 nm. It does not switch between them after purchase. Its strength is concentration: 7,500 mW/cm² at a 9 mm focal point at 365 nm.
The arc spreads its energy across many wavelengths. The LED puts all of its energy where one adhesive needs it. Neither is better in general; each is better for a specific situation.
Reading the Adhesive Data Sheet for Absorption
Before comparing lamps, extract three facts from each adhesive’s data sheet:
- The cure wavelength or band the manufacturer specifies.
- The dose required for full cure at that wavelength.
- Any note on surface cure or shadowed areas, which can point to a dual-cure mechanism.
Incure’s Uni-Weld™ plastic bonder grades and multi-substrate grades cure in the 365–405 nm range, and Uni-Weld™ glass and metal bonders typically cure at 365 nm. Adhesives from those families sit comfortably inside a single LED wavelength. An adhesive specified only for a band an LED does not cover, or one with no stated wavelength at all, points toward a broadband source.
Scenario A: The Multi-Chemistry Lab
Consider a development lab that qualifies several adhesives a month from different formulation families. Some specify 365 nm, others 405 nm, and some give only a broad range. A single L9000™ set to one wavelength would suit some of those adhesives and not others, forcing a second unit or a compromise.
Here the S20™’s 275–650 nm output earns its place: one lamp covers every candidate during screening. Its adjustable 25–100% intensity and 1–99 second timer let the lab build comparable cure schedules across chemistries. The trade-off is a 1–2 minute warm-up and a cooldown before restart, which matters little on a bench but more on a line.
Scenario B: The Dedicated Production Station
Now consider a station that bonds one component with one qualified adhesive, all day. The adhesive’s cure wavelength is fixed and known. Here the L9000™ fits naturally: it fires at full output with no warm-up, it is calibration-free, and it is rated at 15,000 hours with less than 20% intensity decay. Its 0.1–999.9 second timer and RS-232 PLC trigger suit automated cycles.
The L9000™ lightguide and working-distance guide covers how to pick the guide once the wavelength decision is made.
Email Us with the data sheets for the adhesives you run, and Incure’s team can map their cure bands against arc and LED options.
A Decision Table in Words
Work through these questions in order:
- Is there one adhesive per station? If yes, and its wavelength matches an LED option, favor LED.
- Do adhesives change often, or come from several suppliers? Favor broadband arc.
- Is start-stop operation constant? The arc’s warm-up and cooldown cost time; LED fires instantly.
- Is the cure band known but unusual? Check it against the five L9000™ wavelengths before deciding.
- Will the process move from lab to line? Many teams screen on an arc, then move the qualified adhesive to an LED unit set to its wavelength and re-verify the dose.
Maintenance Follows the Spectrum Choice
The two sources age differently. S20™ bulbs are model-matched: the 282008 (100W) or 282068 (200W) short arc lamp, depending on configuration. Arc lamps are commonly replaced every 1,000–2,000 hours depending on duty cycle, with the S20™ rated at 2,000+ hours. The L9000™ LED module is replaced at end of life rather than recalibrated. Both still benefit from a radiometer check at the bond plane, since the lightguide can lose transmission over time.
For the guide side of the system, see what a light guide does in a UV spot lamp system, and for the full architecture, Incure’s explainer on how a UV LED spot curing system works.
Final Thoughts
Start with the adhesive’s absorption band, not the lamp catalog. One known chemistry points to a narrow-band LED; many or unknown chemistries point to a broadband arc. Contact Our Team to match an Incure spot lamp to the adhesives on your floor.
Visit www.incurelab.com for more information.