On a UV conveyor, the lamp’s height above the belt is the setting most often left wherever it was last time. Yet the published irradiance of every lamp head is quoted at a specific working distance, and a tall part, a fixture, or a recessed bond line changes that distance without anyone touching the controls.
Q: How high should the lamp be on a UV curing conveyor?
A: Set the lamp so the distance from the lamp face to the bond line — not to the belt — matches the working distance the cure was qualified at, while leaving clearance for the tallest part and fixture to pass. On Incure’s CDM™, LED heads adjust from 0.5 to 2.0 inches and F400/F500 arc heads from 3.0 to 6.5 inches.
Measure to the Bond Line, Not the Belt
A height scale on the conveyor reads the distance to the belt surface. The adhesive does not sit on the belt; it sits on the part, sometimes on top, sometimes halfway down a side wall, sometimes at the bottom of a pocket. The distance that matters is from the lamp face to the adhesive.
As a hypothetical, suppose a part is 1.0 inch tall with its bond line at the top surface, and the LED head is set 2.0 inches above the belt. The real working distance is 1.0 inch, not 2.0. If the same head cures a flat label lying on the belt, working distance is the full 2.0 inches. Two products at the same height setting can see very different irradiance.
Why Published Figures Name a Distance
Incure’s LED head figures are quoted at a 2-inch working distance: 1,900 mW/cm² at 385/395/405 nm for the L64 and L88, 3,100 mW/cm² at 365 nm for the M62, and 6,150 mW/cm² at 365 nm for the M51. Arc head uniformity figures are given at 2.0 inches as well. Incure notes that delivered dose varies with working distance and part height, so a distance different from the reference changes what the part receives.
The direction of the change depends on the head and its optics, so do not assume a closer lamp always delivers more. Measure irradiance with a radiometer placed at the bond-line height of the actual part, at the height setting you intend to use, and record that reading as the reference for the product.
Clearance: The Mechanical Limit
The lamp must also let every part pass. Check three things before setting height:
- Tallest point of the part, including connectors, leads, or features that stand above the bond line.
- Fixture or carrier height, since a fixture adds to the part’s stack height.
- Part movement on the belt. Parts that can tip or shift need margin above their resting height.
The LED heads’ 0.5–2.0 inch range suits flat and low-profile parts. Taller parts may fall outside the LED range entirely, which is one reason the F400/F500 heads, with a 3.0–6.5 inch range, exist on the same platform. The trade-off is width: the F400 and F500 allow up to 5 inches of part width, against 8 inches on the L88.
Email Us with your part height, bond-line position, and fixture dimensions, and Incure can check which CDM™ head’s height range fits.
Mixed Part Heights on One Line
When a line runs parts of different heights, each product needs its own height setting in its recipe. Practical rules:
- Record height for each product as the lamp-to-bond-line distance, then translate it into the belt-referenced setting.
- Re-measure irradiance after every height change; do not reuse the reading from the previous product.
- Group products by height so the lamp moves in one direction through the day rather than back and forth.
- If two products need heights outside the same head’s range, they may need different heads or chassis setups.
Side Walls and Recesses
Bond lines on vertical faces or in pockets are partly shadowed from an overhead lamp, and changing height does not fix shadowing. A focused-beam head concentrates output on a narrow strip — 1 inch on the M51, 2 inches on the M62 — but it is still overhead. For deeply recessed joints, consider whether the part orientation on the belt can be changed, or whether a spot-curing step better suits that bond.
Height, Speed, and Dose Together
Height sets irradiance; belt speed sets exposure time; together they set dose. If a height change lowers measured irradiance, restore dose by slowing the belt in proportion rather than accepting under-cure. On the CDM™ the belt adjusts from 1.5 to 12.0 ft/min. Remember that speed cannot raise irradiance: if an adhesive has a minimum irradiance requirement, height and head selection are the only ways to meet it.
Quick Setup Sequence
- Identify the bond-line height on the part.
- Choose a lamp setting that gives the qualified working distance with clearance for the tallest feature.
- Run the belt empty with a sample part to confirm clearance.
- Measure irradiance at bond-line height.
- Set belt speed for the required dose and record all values.
For the overall process context, see the curing conveyor industrial guide; the CDM™ lamp-head guide lists height range and width for each head.
Contact Our Team for help setting lamp height for your parts.
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