This page is the fast version for sourcing and program managers.
If you already know your load case and need joint design details, read the engineering deep-dive: Adhesive Bonding vs Press-Fit: Engineering DFM Playbook.
Need a direct fit-screening tool for alias intent? Use the 3 8 diameter miniature press fit magnetic contact checker.
1. Fast screening thresholds (RFQ stage)
Use this as a first-pass filter before DFM review.
| Program condition | Adhesive-first starting point | Press-fit/sleeve-first starting point |
|---|---|---|
| Maximum rotor speed | Up to around 8,000 rpm | Above around 12,000 rpm |
| Continuous operating temperature | Up to around 120 C | Above around 150 C |
| Thermal cycling severity | Moderate cycle count | High cycle count with large temperature swing |
| Chemical exposure | Mild humidity / light oils | Aggressive oils, solvents, or process chemicals |
| Rework priority | Reworkability required | One-time locked assembly acceptable |
For boundary cases between these bands, request both process paths in the supplier DFM response.
2. What to include in RFQ so quotes are comparable
Most "process recommendation" disagreements are RFQ definition gaps. Include the fields below:
- maximum speed and overspeed requirement
- continuous and peak temperature with dwell time
- exposure media (oil, coolant, solvent, humidity)
- service life target and critical failure mode
- runout / balance requirement for rotating assemblies
- allowed retention verification method
If these are omitted, suppliers will quote with different assumptions and the lowest quote is not directly comparable.
3. Gate criteria before method freeze
Do not freeze retention method after a visual sample check. Freeze only after measurable gates are met.
| Gate | Minimum evidence |
|---|---|
| EVT (fit/function) | n >= 10 samples, no magnet crack/chip caused by assembly, retention test method defined |
| DVT (stress) | n >= 30 samples across stress profile, no catastrophic detachment, drift inside agreed window |
| PVT (process) | pilot lot trend stable, critical retention dimensions/process variables controlled, reaction plan signed |
Recommended acceptance lines for RFQ notes:
- zero catastrophic detachment in defined stress profile
- no uncontrolled crack/chip defect on magnetic-critical surfaces
- process capability target (for key retention variable) agreed before pilot PO
4. Cost and lead-time reality
| Cost / schedule item | Adhesive path | Press-fit / sleeve path |
|---|---|---|
| Early fixture complexity | Lower | Higher |
| Process cycle impact | Cure time and verification time | Insertion force monitoring and fit control |
| Rework path | Usually easier if procedure is defined | Limited once interference lock is applied |
| Reliability upside | Good in moderate thermal/load envelope | Better under high load/high speed if process is controlled |
Ask suppliers to quote prototype and production assumptions separately. If they use one process description for both, request split documentation.
5. Common failure pattern seen in buyer projects
Case pattern:
- RFQ specified magnet size but not adhesive gap
- supplier used near line-to-line fit to "avoid looseness"
- assembly passed room-condition pull test
- field returns appeared after thermal cycling due to adhesive starvation
Corrective action that worked:
- add explicit retention gap window
- define thermal-cycle validation before pilot approval
- add process check on adhesive application coverage
The cost of this correction at pilot stage was far lower than field replacement cost.
6. Supplier evidence checklist (before PO)
Require the supplier to provide:
- retention method selection rationale against your load profile
- test setup definition (fixture, temperature, duration)
- sample size and pass/fail criteria
- failure analysis workflow if a sample fails
- change trigger list (what forces revalidation)
If one of these is missing, keep retention method as open risk and do not close sourcing decision.
7. Which article to read next
- Need design-level numbers and process windows: Adhesive Bonding vs Press-Fit: Engineering DFM Playbook
- Need full RFQ structure: How to Specify a Custom Magnetic Assembly in Your RFQ
This page intentionally stays at screening depth for sourcing teams. For engineering-level joint geometry, thermal stress, and retention validation structure, continue to the deep-dive article linked above.
For buyer-side review of your current RFQ and retention assumptions, contact [email protected] or WhatsApp +8618857971991 (Open WhatsApp).
