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 the grade from data, not assumption. Measure the actual bond-line gap on a statistically meaningful sample of mated production parts, at several points around the joint, and plot the distribution. If the widest gaps sit within a few tenths of a millimeter, CM-500 with an activator covers the range. If the tail runs wider, either tighten the molding process, redesign the joint to close the gap, or move to a high-viscosity or gel grade. Doing this analysis up front prevents a field problem that only shows up on the parts at the edge of the tolerance band.
Validation
Incure provides ISO 10993-5 summaries, technical data sheets, and sterilization guidance for your device file. The finished-device manufacturer owns the biological evaluation. Because gap-filled joints vary more than tight ones, widen your sample size during qualification and test aged, sterilized production parts across the tolerance range, not just nominal parts.
For help selecting a grade against your measured joint gaps, Email Us with your tolerance analysis.
Frequently Asked Questions
Q: What is the largest gap CM-500 can fill?
A: Up to a few tenths of a millimeter with an activator to drive cure. Larger gaps need a high-viscosity CM grade or a different chemistry.
Q: Does a thick bond line stay flexible?
A: Cyanoacrylate remains relatively rigid at any thickness. Design the joint so a mechanical feature carries peak load.
Q: Will gap-filled joints pass the same tests as tight joints?
A: They can, but they show more part-to-part variation. Qualify across the full tolerance range.
A medical grade adhesive that tolerates real molded-part variation keeps yield high without loosening the spec. Incure Cyro-Weld™ CM-500 fills that role with documented biological safety testing. Contact Our Team to request samples and technical data.
Visit www.incurelab.com for more information.