UV Curing: Equipment & technology, every question, answered
56 answers below, written from the manufacturer's manuals and our own bench experience. Prefer to tap through them? The same answers power the live chat in the corner. Ready to buy? See the systems or request a quote.
Spot curing vs flood curing, what's the difference?
A spot system concentrates its output into a small, intense spot for one or a few bond points; a flood system spreads gentler light over several square inches for whole-surface cures. Spot wins on speed per joint and thermal control; flood wins on area coverage.
Many lines use the two together, spot to tack and fix parts, flood for final coating cures.
When is a conveyor curing system a better fit?
Conveyor systems carry parts under a fixed lamp on a moving belt, which suits high-volume flat work like coated panels and printed sheets. If your cures are discrete joints on assembled parts, a spot system is usually faster, more compact, and far easier to fixture.
How does a mercury short-arc lamp work?
A high-voltage pulse strikes an arc between two closely spaced electrodes inside a pressurized quartz envelope containing mercury. The excited mercury plasma emits intense light across the UV and visible spectrum, and a reflector focuses that output into the light guide.
Why do arc lamps need a warm-up period?
After ignition the mercury takes a few minutes to fully vaporize and the arc to stabilize at operating pressure and temperature. Output during warm-up is lower and less consistent, so hold production exposures until the lamp settles.
Why can't I restart an arc lamp right after shutdown?
A hot lamp holds high internal pressure that prevents the arc from restriking until it cools, typically for several minutes. That is why arc systems use a shutter for exposure control during production rather than cycling lamp power.
What does the reflector in an arc system do?
It sits behind the arc and focuses the lamp's output into the light guide entrance, without it, most of the energy would never reach the work. Our SunSpot 2 modules combine lamp and reflector in one quick-change cartridge, so the pair is always replaced as a matched set.
How do curing LEDs differ from arc lamps?
LEDs emit one narrow wavelength band, switch on and off instantly, run for tens of thousands of hours, and add almost no infrared heat. Arc lamps trade those conveniences for broad-spectrum output that some chemistries still require.
Why can LEDs switch on and off instantly?
An LED is a semiconductor junction, so light output follows drive current within microseconds, there is no plasma to ignite or stabilize. That means no warm-up, no cool-down, no shutter, and exposure timing handled purely by electronics.
What does narrowband LED output mean in practice?
An LED concentrates nearly all its energy within a band roughly 10–20 nm wide around its rated peak, 365, 385, 395, or 405 nm on our SkyBeam heads. Your adhesive's photoinitiator must absorb at that peak, so match the LED to the adhesive datasheet.
How long do curing LEDs last vs arc lamps?
Short-arc lamps typically run about 2,000 hours; the LED heads in our SkyBeam are rated around 20,000 hours. LEDs also fade gradually rather than failing outright, which makes replacement plannable.
Do LED systems really run cooler at the part?
Yes, LEDs emit essentially no infrared, so the part receives UV energy without radiant heat. Arc lamps carry significant IR alongside the UV, which is why heat-sensitive optics and plastics usually favor an LED source.
Liquid-filled vs fused-fiber light guides?
Liquid-filled guides transmit more UVA and cost less, which makes them the standard for spot curing. Fused-fiber bundles tolerate tighter routing and autoclaving in exchange for lower transmission.
Our catalog guides are liquid-filled; fused-fiber versions are available made to order.
How does light travel through a liquid light guide?
By total internal reflection: light entering within the guide's acceptance cone bounces along the liquid core, which has a higher refractive index than the surrounding wall. Losses come from core absorption and end-face condition, which is why length and cleanliness matter.
How much light is lost per meter of guide?
Plan on roughly 10–15% loss per meter in the UVA band for liquid-filled guides. Order the shortest guide that comfortably reaches the work, and verify tip output with a radiometer after any length change.
What's the minimum bend radius for a light guide?
Hold at least a 100 mm (4 in) bend radius on our liquid-filled guides. Kinking permanently damages the core and drops transmission, and straightening the guide afterward does not undo it.
What is light guide solarization?
Gradual UV-induced darkening of the core and end faces that permanently reduces transmission. It is one reason guides are consumables: baseline output when new and replace when readings drop about 20%.
How do I know when to replace a light guide?
Compare tip intensity on a radiometer against the baseline you took when the guide was new. With a known-good lamp, a drop of about 20% means end-face wear or solarization has caught up with it.
Handled gently, a guide typically outlasts two to three lamp changes.
How should I clean light guide end faces?
Use 99% isopropyl alcohol on a lint-free wipe, then inspect for scratches or discoloration. Keep the protective end caps on whenever a guide is disconnected, a damaged input face absorbs energy and can heat-crack the guide.
What is a pole splitter or multi-leg light guide?
A guide that divides one lamp's output into two or four legs so several joints cure at once in a single timed exposure. Our SunSpot 2 splitters are balanced to within ±5% between legs.
Do splitter legs each get less intensity?
Yes, the lamp's output divides among the legs, so each leg of a 4-pole splitter carries roughly a quarter of the single-pole energy. Budget exposure time accordingly and verify every leg with a radiometer at setup.
How do exposure timers improve consistency?
A timer delivers the same exposure every cycle, taking the operator's reflexes out of the dose equation. On the SkyBeam, each of the four channels has its own independent timer, so different joints can run different recipes at the same time.
How do I adjust cure intensity?
On LED systems you set the drive level electronically per channel; on arc systems the lamp runs at fixed power, so intensity is adjusted optically through spot size, working distance, guide choice, or filtering. Changing spot size or distance is usually the most practical control at the part.
Why does spot size change irradiance?
The same optical power spread over a larger area means proportionally lower irradiance, halving the spot diameter roughly quadruples intensity. Pick the smallest spot that still covers the bond line.
What does a focusing lens assembly do?
It mounts at the guide tip and focuses the output to a tighter or wider spot, tighter for micro-joints, wider for bond lines. SkyBeam LED guides ship with 6 and 12 mm lenses; for other setups, ask us and we'll configure focusing optics to your guide.
Does working distance affect intensity?
Strongly, the beam diverges after it leaves the guide tip, so irradiance falls quickly with distance. Fixture the tip at a repeatable height and treat that distance as a locked process parameter.
Why does lamp output drift over time?
Arc electrodes erode and sputter material onto the quartz envelope, dimming output as hours accumulate; LED output declines far more slowly through gradual junction aging. Either way, periodic radiometer checks catch the drift before cures start failing.
How do I track lamp and LED hours?
The SunSpot 2 has a lamp-hour meter and the SkyBeam keeps a life log per channel, so replacement is planned rather than reactive. Reset the counter after every swap.
What are heat filters and do I need one?
Filters between a broadband source and the work strip infrared and unwanted wavelengths so the part sees mostly useful UV. For the SunSpot 2, the snap-in UV1870 band-pass kit trims output to the UVA band for heat- or short-wavelength-sensitive assemblies.
When should I use a UVA band-pass filter?
When your adhesive cures fine on UVA alone but the part cannot tolerate the arc's UVB/UVC or heat content, delicate plastics, coated optics, or work near operators. Filtering costs some total output, so re-verify dose after installing it.
Do curing systems need special cooling or airflow?
Arc systems are fan-cooled and need clear intake and exhaust space, blocked vents shorten lamp life. Give benchtop units a few inches of clearance and keep vents clean per the manual.
LED systems dissipate far less heat but still rely on unobstructed convection or fans around the heads.
Does duty cycle matter when picking arc vs LED?
Very much, an arc lamp burns hours continuously behind its shutter whether or not you are curing, while an LED only accumulates hours during exposures. Low-duty-cycle work therefore favors LED economics dramatically.
Can I power-cycle an arc lamp between parts?
No, each ignition stresses the electrodes, and a hot lamp will not restrike until it cools. Leave the lamp running, use the shutter and timer for exposures, and save shutdowns for breaks and end of shift.
Which LED wavelengths are available?
Our SkyBeam offers 365, 385, 395, and 405 nm heads, one per channel, mixed however you like, and the SkyWand comes in 365 or 405 nm. 365 nm is the workhorse for most industrial adhesives.
How do I choose the right cure wavelength?
Start with the adhesive datasheet, it lists the wavelengths its photoinitiator absorbs and the dose required. If it cures at a single UVA peak, match an LED to it; if it calls for broad-spectrum or UVB content, use an arc source.
Who still needs a broad-spectrum arc source?
Anyone running chemistries that want UVB/UVC or visible content: older broadband formulations, surface-inhibited adhesives that stay tacky under a single wavelength, and deep encapsulant sections that benefit from visible light penetrating the fill.
What spot sizes can these systems produce?
From about 2 mm up to 12 mm at the part, set by guide core diameter, lens choice, and working distance. SkyBeam guides include 6 and 12 mm lenses; SunSpot 2 spot size follows the guide diameter and tip-to-part distance.
5 mm or 8 mm light guide core, which one?
The 5 mm core concentrates the lamp into a hotter spot, roughly 2.5 times the irradiance of the 8 mm at the same setting, while the 8 mm gathers more total energy for wide bond lines and mini flood cures. Pick the smallest core that covers your joint.
Can I order custom light guide lengths?
Yes, single-pole guides are made to order from 0.5 m to 3 m in 3, 5, and 8 mm cores, typically shipping in 2–3 weeks. Longer runs trade away intensity, so verify tip dose before locking in the process.
Do light guides interchange between systems?
SunSpot 2 guides (UV0570, UV0571, UV0774 and the multi-pole splitters) interchange freely with each other. SkyBeam channels take the dedicated UV4053/UV4054 LED guide matched to the channel wavelength, the two families don't cross over.
What automation interfaces do curing systems offer?
The SkyBeam provides PLC I/O, RS-232 control, and a safety interlock input, with independent timers per channel; foot-pedal and TTL trigger options are available on all our systems. That covers everything from a bench pedal to full line handshaking.
How often should I measure UV output?
Weekly spot checks suit most production lines, tightening to daily for validated processes. Take a fresh baseline any time you change a lamp, guide, lens, or working distance.
What's inside a quick-change lamp module?
The short-arc lamp and its matched reflector in one cartridge that swaps in seconds without tools or alignment. Keep a spare on the shelf and a lamp change never becomes a line-down event.
Can I replace SkyBeam LED heads myself?
Yes, on the SkyBeam the LED and light guide replace as one assembly: order UV4053-xxxF (fan-cooled) or UV4054-xxxC (convection) at your wavelength, plug it into the channel, and reset that channel's hour log per the manual.
How does the SkyWand keep output constant on battery?
Its drive electronics regulate LED current so intensity holds steady as the pack drains instead of fading. Packs are hot-swappable, keep one on the charger and one on the tool for uninterrupted work.
Why choose a handheld LED unit for rework?
Rework and field repair rarely fit a fixture, so a cordless handheld brings the cure to the part, at the bench or in the field. The SkyWand runs the same 365/405 nm chemistries as a benchtop LED system.
Do LED curing systems need warm-up time?
No, output is at full, stable intensity the instant a channel fires, and it stops just as fast. That is one of the biggest process-control advantages over arc sources.
What is a safety interlock input?
A circuit that lets a guard door or enclosure switch inhibit the UV source, open the guard and the light cannot fire. The SkyBeam includes an interlock input for exactly this in automated cells.
What electrical supply do the systems need?
The SunSpot 2 ships in a 120 VAC version (UV1853) and a 240 VAC version (UV2132), and the cordless SkyWand runs on hot-swap Li-ion packs with about a 4-hour charge. Tell us your region on a quote request and we will confirm the right configuration.
Why is my cure suddenly taking longer?
Something in the optical chain has drifted, an aging lamp, a solarized or dirty guide, a changed working distance, or a mis-set intensity. Measure at the guide tip with a radiometer and compare against your baseline to locate the loss.
What happens as arc lamp electrodes wear?
Electrode material erodes and deposits on the quartz envelope, darkening it while the arc gap widens, output drops, ignition gets unreliable, and eventually the lamp will not strike. Those are the classic end-of-life signs alongside the roughly 2,000-hour rating.
Does an old arc lamp change spectrum, not just output?
Somewhat, envelope darkening attenuates shorter wavelengths first, so a tired lamp can under-deliver UVB/UVC content before total UVA looks bad. If your chemistry relies on short-wavelength content, replace on the conservative side.
How much heat does the beam put into the part?
An LED spot adds almost none, since the output is nearly all UVA. A broadband arc beam carries meaningful infrared and visible energy, if a part warms noticeably, consider the UVA band-pass filter, shorter exposures, or an LED source.
What is an LED head, exactly?
The emitter assembly for one channel: one or more UV LED dies on a heat-sinked substrate with optics that couple output into the light guide. Heads are rated by peak wavelength and are the replaceable light source of an LED system.
Can one system cure several points at once?
Yes, two ways: split a SunSpot 2 arc across up to four balanced light-guide legs, or run four independent SkyBeam LED channels, each with its own timer and wavelength. Either approach cures a multi-joint assembly in one cycle.
Why won't my arc lamp ignite?
If it is hot, wait for a full cool-down, a hot lamp will not restrike. If cold ignition fails repeatedly, the lamp is usually at end of life: check the hour meter and swap the module, and contact tech support if a fresh module still will not strike.
Shutter or lamp switch, which controls exposure?
On an arc system, always the shutter and its timer, the lamp stays lit. On an LED system the source itself switches instantly, so the timer drives the LED directly and no shutter exists.
