The gasket that seals a housing, cover, or connector is, in many assemblies, the difference between a reliable product and a warranty return. Traditional cut-sheet gaskets and O-rings are consistent when installed correctly, but they add assembly steps, require precise groove dimensions, and can be displaced during installation. Form-in-place gasket (FIPG) technology replaces pre-cut gaskets with a dispensed bead of UV-curable sealant that cures in the groove or on the mating surface, conforming precisely to the actual surface geometry. UV spot lamps cure these gasket beads rapidly along their full length, enabling FIPG processes that support high-volume assembly without the waiting periods required for anaerobic or thermally cured sealants.
What Form-in-Place Gasketing Is
Form-in-place gasketing is a manufacturing process in which a liquid sealant is dispensed in a continuous bead onto one of the mating surfaces of a housing joint. The assembly is then mated, compressing the bead to fill the joint gap. The sealant cures in place, conforming to both mating surfaces and forming a seal that integrates with the actual surface geometry rather than depending on a pre-cut part that may not match.
FIPG is used in a wide range of applications:
- Engine and transmission covers in automotive powertrain assemblies
- Electronic housing covers for IP-rated (ingress protection) enclosures
- Sensor and instrument housings requiring environmental sealing
- Pump and compressor covers in industrial equipment
- Junction box and enclosure covers in outdoor electrical installations
UV-curable FIPG materials provide fast cure at the dispensed bead without requiring oven cure or waiting for anaerobic cure. The UV spot lamp traverses the gasket bead after dispensing, curing each section of the bead in sequence.
UV-Curable Gasket Material Properties
Pre-cure dispensing characteristics. FIPG materials must flow and be dispensed reliably from robotic or manual dispensing systems. Viscosity is controlled to allow bead formation with consistent width and height without sagging on vertical surfaces. UV-curable FIPG formulations are typically thixotropic — they flow under shear stress during dispensing but hold their shape when at rest.
Post-cure mechanical properties. The cured gasket must compress under assembly clamping load without cracking, must recover when the assembly is disassembled (for maintainable equipment), and must maintain sealing integrity under vibration, pressure differential, and thermal cycling. UV-cured elastomeric silicone acrylate or polyurethane acrylate formulations provide the flexibility and compressibility required.
Chemical resistance. The cured gasket is in contact with whatever fluid or gas the assembly contains or is exposed to. Engine cover gaskets contact oil; electronics housing gaskets contact humidity and possibly cleaning solvents; pump gaskets contact process fluids. Material selection must be matched to the specific chemical environment.
Temperature range. Automotive powertrain applications require gasket materials that function from -40°C cold starts to +150°C underhood temperatures. UV-curable silicone-based FIPG formulations offer wider temperature range than acrylate-only formulations, at the cost of higher material price and potentially different UV cure behavior.
Adhesion to substrate. The FIPG material must adhere to both mating surfaces to maintain seal integrity, particularly in dynamic environments where joint surfaces may move relative to each other. Adhesion to aluminum, steel, plastic, and coated surfaces must be verified for the specific substrates used in the assembly.
The UV Spot Lamp Curing Process for FIPG
After the gasket bead is dispensed onto the mating surface, a UV spot lamp traverses the bead length to cure it before assembly mating. The cure process requires attention to several factors:
Lamp head traversal. The UV spot lamp must irradiate the full bead length at consistent irradiance. Either the part moves under a fixed lamp head, or the lamp head traverses a fixed part. Robot-controlled traversal allows the cure path to follow complex gasket bead geometries — around corners, along curved surfaces, and into recesses.
Traversal speed and dose. The product of irradiance (mW/cm²) and irradiation time (seconds) at each point on the bead must meet the adhesive’s minimum dose specification. For a 365 nm UV LED spot lamp at 2,000 mW/cm² irradiance, achieving 4,000 mJ/cm² requires each point of the bead to be irradiated for 2 seconds. Traversal speed is set to ensure this dwell time across the full bead.
Spot size and bead width coverage. The UV spot must cover the full width of the gasket bead. If the spot is smaller than the bead width, the lamp head must traverse multiple passes, or the beam must be expanded using a diffuser or lens to cover the bead width in a single pass. Uncured bead edges result in adhesion failure at the bead margins after compression.
UV access to the bead surface. The gasket bead surface must be directly accessible to the UV spot lamp. Gaskets dispensed in deep grooves or channels may not receive sufficient UV at their full surface — the groove walls shadow the bead sides. For deeply recessed gasket beads, fiber optic spot lamp heads with small distal tips provide better access than bulkier lamp heads.
If your FIPG process involves complex gasket geometry or robotic traversal requirements, Email Us and an Incure applications engineer will design a cure path and lamp configuration for your application.
Cure Verification for FIPG Applications
Confirming that a gasket bead is fully cured before assembly mating is important — an incompletely cured bead will be displaced or squeezed during mating and may not form a complete seal. Cure verification approaches include:
Tack-free surface test. A fully cured UV elastomeric gasket surface is tack-free to the touch. Any remaining surface tack indicates incomplete cure at the exposed surface, which correlates with incomplete through-cure of the bead cross-section.
Hardness or modulus measurement. Shore A durometer measurement on a cured gasket bead sample confirms that the cured material has achieved its target mechanical properties. Undercured beads are softer than specification.
Cure dose monitoring. UV LED systems that record delivered dose per cure cycle provide indirect confirmation that the adhesive received the specified minimum dose — a necessary but not sufficient confirmation of complete cure.
Assembly pull-off or leak test. Ultimate verification of gasket seal performance is a leak test on the assembled housing under pressure or vacuum. Leak tests detect incomplete sealing from any cause, including undercured gasket material, inadequate joint compression, or surface contamination.
Integration with Robotic Dispensing Systems
In production environments, UV FIPG processes are often fully automated — a robotic dispenser applies the bead, and a UV LED system (either robot-mounted or at a separate cure station) cures the bead before the part moves to assembly mating. Integration considerations include:
- Synchronization between dispense completion and UV cure trigger
- Robot path accuracy for consistent bead placement relative to the UV spot position
- Cure confirmation signal (dose logged, cure cycle complete) before the part is released from the fixture
Contact Our Team to discuss UV spot lamp selection and integration for your form-in-place gasket curing application.
Visit www.incurelab.com for more information.