Bond failure using NXB-KIT-753-002 Structural Adhesive on R-50 robot arm

Description

We are experiencing a critical failure with the NexBot Drives 753-002 Structural Adhesive. Our maintenance team used the adhesive to re-bond a composite sensor mounting plate to the primary aluminum housing on Joint 3 of our R-50 series robot. The team followed the procedure outlined in the service manual, applied the adhesive, and allowed it to cure for a full 24 hours in our climate-controlled facility, which is kept at 21°C. However, within the first hour of returning the robot to its pick-and-place cycle, the bond failed completely, causing the mounting plate to detach. This resulted in an immediate line stoppage. We have used this product before without issue, but this specific application failed well below the expected 25 MPa shear strength. We need to understand if there was a bad batch of adhesive or if there is a revised application procedure we are unaware of.

Symptoms

• Complete separation of bonded components under normal load
• Adhesive appears to have fractured cleanly from the aluminum surface
• Visible residue on both the composite plate and metal housing
• Failure occurred after the recommended 24-hour cure time

Resolution

Investigation determined the likely root cause of the bond failure was inadequate surface preparation prior to adhesive application. While the surfaces were wiped down, trace amounts of machine oil and lack of surface abrasion prevented the NXB-KIT-753-002 epoxy from achieving a proper chemical and mechanical bond to the aluminum housing. The batch number for the adhesive was verified and confirmed to be within specification and shelf life. The customer was provided with a detailed best-practice procedure for surface preparation to ensure future applications achieve the rated 25 MPa shear strength.

Resolution Steps

1. 1. Fully remove all failed adhesive material from both the mounting plate and the robot arm housing using a plastic scraper and an appropriate solvent.
2. 2. Mechanically abrade both mating surfaces using 120-grit sandpaper or a Scotch-Brite pad to remove any oxidation and create a rough surface profile.
3. 3. Perform a two-stage cleaning of both surfaces: first with a degreaser, followed by a final wipe with 99% isopropyl alcohol (IPA) using a fresh, lint-free cloth.
4. 4. Allow surfaces to air dry completely for at least 10 minutes.
5. 5. Attach a new static mixing nozzle to the 50mL cartridge of NXB-KIT-753-002.
6. 6. Dispense and discard a small 'purge bead' (approximately 1-2 inches long) to ensure the two parts are properly mixed in the nozzle.
7. 7. Apply the adhesive to one surface, assemble the parts, and clamp with light, uniform pressure to ensure good contact without squeezing out all the adhesive.
8. 8. Allow the assembly to cure at a minimum of 20°C (68°F) for 24 hours before returning the robot to service.