Incoming Inspection (IQC)¶
Source attribution
This article is an editorially original synthesis. [Industry Knowledge] = common industry practice; [Framework Reference] = standards framework introduction; [Editorial Opinion] = researcher's original judgment. Model specifications are subject to data.hycarfilter. Backlinks: data home.
Quality is "prevented," not "inspected." Incoming Quality Control (IQC) is the first of the three gates — once bad material enters the line, any later inspection is in vain. This section breaks down the incoming-inspection points of the main raw materials.
I. Filter media incoming inspection¶
[Industry Knowledge] Filter media is the core of the filter, so IQC weighs it most heavily. Inspection items:
| Item | Method | Judgment |
|---|---|---|
| Basis weight (grammage g/m²) | Sample weighing | Deviation beyond tolerance → reject |
| Thickness | Thickness gauge | Affects pleat height and area |
| Stiffness | Stiffness tester | Too soft → collapse after pleating |
| Air permeability | Permeability tester (differential pressure–flow) | Determines finished-product differential pressure |
| Pore size / efficiency | Efficiency test bench (sampling) | Corresponds to nominal efficiency tier |
| Resin impregnation uniformity | Visual + ash content | Uneven impregnation → unstable efficiency |
| Temperature / oil resistance | High-temperature / oil-immersion aging | Must-test for oil / fuel filters |
[Editorial Opinion] Filter media is the incoming material with the highest technical content and the easiest to substitute inferior for superior. At the same grammage and thickness, different fiber ratios and resin processes can make efficiency and dust holding capacity differ by an order of magnitude. IQC cannot just look at grammage and thickness; it must sample the efficiency curve — this is the only way to keep "fake media" out the door.
II. Housing / steel shell incoming inspection¶
[Industry Knowledge] Steel housings of spin-on oil / fuel filters:
- Wall thickness: thickness-gauge sampling; insufficient thickness → burst pressure below standard;
- Drawing forming: check whether one-piece drawn (seamless), for cracks / drawing damage;
- Thread: thread go/no-go gauge inspection (go passes, no-go does not) to ensure screw-on fit;
- Plating / anti-corrosion: salt-spray test or visual, to prevent rust in storage/transport.
III. End cap / center tube / seal ring incoming inspection¶
[Industry Knowledge]
- End cap (steel / plastic / PU): dimensions, groove depth (determines adhesive fill), material verification;
- Center tube: hole-punching quality, no burrs (burrs scratch the media), dimensions fit the element;
- Seal ring (NBR): hardness (Shore A), dimensions, high/low-temperature rebound, oil-swelling rate — the seal ring is the key to spin-on filter mating-surface sealing; poor rebound / large swelling → oil leakage.
IV. Adhesive incoming inspection¶
[Industry Knowledge] End cap adhesive / plastisol / PU adhesive:
- Viscosity / mixing ratio: affects injection volume and curing;
- Curing characteristics: small-sample curing to measure strength and verify batch consistency;
- Oil / temperature resistance: oil-immersion aging test of the adhesive, to ensure it does not react with oil/fuel.
V. IQC sampling framework¶
[Industry Knowledge] Incoming materials are sampled by batch, with the sampling scheme referencing the AQL (Acceptable Quality Limit) framework (e.g. ISO 2859 or GB/T 2828): determine sample size and accept/reject numbers (Ac/Re) by lot size, rather than full inspection. Key safety parts (housing, seal ring) can use tightened AQL or even 100% inspection.
Editorial view¶
[Editorial Opinion] To judge a factory's IQC capability, don't ask "do you have incoming inspection"; ask "does the media get its efficiency curve sampled, does the seal ring get rebound and swelling tested, does the housing get thread go/no-go gauging." Whether these three exist determines whether it is preventing bad material or going through the motions. The depth of IQC, more than the existence of IQC, reflects a factory's quality level.
Continue reading: In-Process Inspection (IPQC)