| 1 | Manufacturing Material | Material selection affects fatigue strength, stiffness, wear resistance, corrosion behavior, and total weight. | Forged carbon or alloy steel for high-load applications; ductile iron may be suitable where the design specifically permits it. The exact grade must follow the approved engineering drawing. | Material certificate, heat number traceability, chemical composition report, and confirmation that the supplied grade matches the drawing or customer specification. | Material described only as “high-quality steel” without a grade, standard, or traceable certificate. |
| 2 | Forging or Casting Integrity | Internal voids, laps, inclusions, and shrinkage defects can reduce steering-system durability and safety. | For forged parts: controlled forging flow and heat treatment. For cast parts: controlled solidification and documented inspection appropriate to the design risk. | Process flow chart, forging or casting parameters, first-article report, and non-destructive inspection records such as magnetic-particle or ultrasonic testing where specified. | No process records, no defect limits, or reliance on visual inspection alone for safety-critical areas. |
| 3 | Heat Treatment and Hardness | Correct heat treatment balances strength, toughness, wear resistance, and resistance to brittle failure. | Hardness and tensile targets should be defined by the part drawing or material standard. Testing should be performed using a recognized method such as Rockwell hardness testing under ISO 6508 or an equivalent standard. | Heat-treatment recipe, furnace records, hardness maps, tensile-test results where applicable, and calibration records for testing equipment. | One hardness value quoted for the entire part without location, test method, tolerance, or batch traceability. |
| 4 | Dimensional Accuracy | Critical dimensions influence steering geometry, bushing fit, ball-joint alignment, and installation interchangeability. | Critical bores, mounting faces, and joint centers should be controlled according to the approved drawing, GD&T requirements, and functional tolerance stack-up. | CMM inspection report, calibrated gauges, dimensional control plan, GD&T inspection records, and first-article measurement results. | Only overall length and width are inspected while mounting holes, bores, and pivot alignment are not measured. |
| 5 | Bushing and Joint Compatibility | Bushing stiffness, compression behavior, and joint articulation directly affect steering feel, noise, vibration, and service life. | Use the specified rubber, thermoplastic elastomer, or other approved material with defined hardness, operating-temperature range, articulation angle, and press-fit requirements. | Bushing material specification, hardness report, pull-out or retention test, articulation test, supplier traceability, and compatibility confirmation for the mating components. | Unspecified bushing compound, inconsistent hardness, visible cracks, excessive flash, or uncertain press-fit dimensions. |
| 6 | Fatigue and Load Performance | Idler arms experience repeated steering loads, impacts, vibration, and road-induced cyclic stress rather than only static loading. | Validation should represent the intended vehicle load case, duty cycle, temperature, articulation, and failure criteria. Static proof testing alone is not sufficient for fatigue evaluation. | Test plan, load-versus-cycle data, fixture description, failure analysis, durability report, and correlation between test loads and the customer application. | Only a single maximum-load result is provided, with no cycle count, test conditions, or acceptance criteria. |
| 7 | Corrosion Protection | Corrosion can reduce section thickness, damage press fits, increase friction, and accelerate fatigue cracking. | Select coating or surface treatment according to the application environment. Salt-spray testing under ASTM B117 may support comparison, but the acceptance duration must be agreed in advance and should not replace real-use validation. | Surface-treatment specification, coating thickness report, pretreatment details, adhesion results, salt-spray report where required, and protection of machined interfaces. | “Rust-proof” claims without coating type, thickness, test method, exposure duration, or uncoated-area requirements. |
| 8 | Quality Management System | A controlled quality system reduces variation and improves corrective action, traceability, and change management. | ISO 9001 certification is a useful baseline. IATF 16949 may be relevant when the supply chain or customer program requires automotive-specific quality controls. | Current certificate, certification scope, audit history, control plan, process FMEA, gauge calibration records, and documented corrective-action process. | Expired certificate, certificate scope unrelated to the product, or refusal to provide inspection and corrective-action documentation. |
| 9 | Inspection and Sampling Plan | Consistent inspection determines whether production parts continue to meet critical requirements after approval. | Use 100% inspection for designated safety-critical characteristics when required, with statistical sampling for other features based on an agreed plan such as ISO 2859-1. | Control plan, inspection frequency, acceptance quality limit, inspection equipment list, nonconforming-product procedure, and lot-release records. | Unclear sampling levels, no defined lot size, no separation of critical characteristics, or undocumented rework. |
| 10 | Traceability, Delivery, and Technical Support | Traceability and responsive engineering support reduce recall exposure, installation problems, and production interruptions. | Each production lot should be traceable to material, process, inspection, and shipment records. Delivery capability should be measured using an agreed on-time-in-full target and documented escalation process. | Lot or date-code system, production capacity statement, lead-time history, packaging specification, change-notification procedure, warranty terms, and response-time commitment. | Mixed lots, missing date codes, uncontrolled engineering changes, vague warranty terms, or no defined response process for field failures. |