Molded parts never fit perfectly. Draft angles, sink, warpage, and tolerance stack-up leave gaps in the tenths of a millimeter at real assembly joints. A medical grade adhesive that only works in a zero-gap bond line will fail on a fraction of production parts. Incure Cyro-Weld™ CM-500 is a medium-viscosity grade formulated to hold where the fit is imperfect. The Gap Problem in Device Assembly Two injection-molded housing halves that look mated can have a bond line that varies from contact to 0.2 mm around the perimeter. An ultra-low-viscosity adhesive drains out of the wide sections and leaves them unbonded. A medium-viscosity grade stays in place long enough to cure across the whole joint and builds a fillet in the gaps that resists peel at the seam edge. CM-500 is a single-component grade in the Cyro-Weld™ CM series, formulated to meet ISO 10993-5 for cytotoxicity, and intended for external, disposable, and wearable components rather than implanted parts. Incure Cyro-Weld™ CM-500 at a Glance Chemistry: single-component, room-temperature-cure cyanoacrylate Viscosity: medium, for gap filling and controlled placement Fixture speed: seconds to tens of seconds depending on substrate and humidity Bond strength: high shear strength on suitable rigid plastics Thermal behavior: resists thermal-cycle stress at the bond line Biological safety: formulated to meet ISO 10993-5 for cytotoxicity Sterilization: compatible with validated ethylene oxide and gamma processes; confirm with Incure Where CM-500 Fits Housing perimeter seams: bonding enclosure halves where the fit varies around the joint Boss and rib capture: joints where molded features do not bottom out consistently Insert retention: holding metal or rigid inserts in oversized molded pockets Field-repair kits: rework joints where the original fit has been disturbed For a framework on matching viscosity and strength to a joint, see matching adhesive grade to viscosity and tensile requirement. Process Control for Gap-Filling Bonds A thicker bond line cures more slowly than a thin one because moisture has to diffuse further in, and the exotherm in a large mass can be significant. For gaps toward the top of the range, use an activator on one face to drive cure through the depth, or accept a longer hold before handling. Dispense enough adhesive to fill the widest section of the joint without heavy squeeze-out elsewhere. Cut and inspect sample joints during qualification to confirm the adhesive actually reached the gaps rather than bridging the surface. Where the two housing materials differ, expansion mismatch loads the filled joint across temperature; review how CTE mismatch causes adhesive bond failure. Storage, Shelf Life, and Handling Store unopened CM-500 refrigerated at 2–8°C and let each bottle reach room temperature before opening so condensation does not enter the container. Reseal after every use, keep the air headspace low, and use within the opened shelf life on the label. Rotate stock first-in-first-out and record lot numbers in the device history record. Dispense in a ventilated station with nitrile gloves and eye protection, and keep water and activator available to cure spills before cleanup. Tolerance Analysis Before Grade Selection Choose…