Appearance Acceptance Specification for PCM Iron Parts of LCD MONITOR/TV Products
I. Scope of Application
This specification is the sole basis for the appearance quality acceptance of PCM iron parts of LCD MONITOR/TV products. It covers the delivery inspection of suppliers, the incoming inspection of IQC, and the full - process appearance control during mass production, and clarifies the appearance defect judgment criteria for iron parts from raw materials to finished products.
II. Basic Rules for Inspection
(I) Visual inspection conditions
Visual inspection is the core method of appearance inspection. The following parameters must be strictly followed to ensure consistent judgment:
1. Lighting requirements: The samples should be placed under natural light or an artificial light source of 500 - 800 LUX (calibrate the illuminance once a month to ensure no attenuation of the lamp tubes).
2. Observation parameters: The distance from the sample is 100 cm (simulating the normal viewing angle of the user), the viewing angle is 45° - 90° (covering the visible angles of each side), and the observation time is 10 - 12 seconds (balancing detail recognition and efficiency).
(II) Rejection criteria and dispute resolution
- Defect determination must comply with the above visual inspection conditions.
- If the supplier has objections to the rejection result, the latest R&D approved sample, the Limit Sample confirmed by the customer, or the sample sealed by IQC shall be taken as the final basis. It is prohibited to adjust the judgment logic independently.
(III) Regional definition
According to the visibility and functional importance of iron parts in the finished product, the appearance is divided into 4 types of areas:
Side X: The front side of the finished product (the visual core area with the strictest requirements);
Y plane: Celestial side + left and right sides (including the arc surface, secondary focal area);
Z plane: Screw hole/square structure area (non-primary visible area);
Surface Z1: Bottom on the ground side (almost invisible, with the loosest requirements).
III. Sampling Plan
Adopt the single sampling plan of MIL - STD - 105E LEVEL Ⅱ of the US military, and set AQL (Acceptable Quality Level) according to the severity of defects:
Critical Defect (CR): AQL = 0 (Zero tolerance, such as structural cracking, large - area exposure of the substrate);
Major Defects (MAJ): AQL = 0.4 (Strict control, such as color difference on the front side and paint peeling).
Minor Defects (MIN): AQL = 1.5 (Moderately lenient, such as slight scratches on the ground side).
*Note: The AQL value represents the allowable number of defects per 1,000 products. CR = 0 means that critical defects are not allowed to occur.*
IV. Inspection standards
(I) General appearance requirements
1. Cleanliness control
Core requirements: The surface shall be free of oil stains, dirt, whitening or powdery precipitation (such problems will damage the adhesion of the paint spray or the assembly viscosity).
Oil stain detection: Attach the back adhesive (such as acetate cloth tape) mass - produced by Lexuan to the area to be tested. If it adheres firmly without falling off, it is OK. If it comes off with a gentle tug, it indicates that the oil stains have not been cleaned thoroughly, and it is judged as NG (simulating the viscosity requirements of tape/foam in actual assembly).
2. Color difference management
Standard basis: The color shall use the color chip (Signed Color Chip) recognized by R&D as the sole standard. Suppliers are prohibited from comparing the samples with the "self - assembled semi - finished products".
Quantitative requirements: The color difference between the mass-produced parts and the color board shall meet the requirement of △E < 1.0 (△e is the international color difference formula, and when △e ≤ 1.0, the difference is hardly perceptible to the naked eye).
(II) Special tests for painting (baking finish)
Spraying paint is the core protection process for iron parts. The quality of the coating needs to be verified through 6 tests:
1. Alcohol rub resistance test (simulating daily cleaning)
Tools and parameters: Medical gauze (lint-free) + 98% alcohol, 500g weight (simulating normal force), 20mm friction length, 1 round trip per 2 seconds (at a constant speed), 100 cycles;
Judgment criteria: There should be no paint peeling or exposed substrate on the surface (98% alcohol is a strong solvent, which is used to verify the coating's ability to resist daily cleaning friction).
2. Alcohol evaporation resistance test (simulating static corrosion)
Conditions and methods: At room temperature, apply ethanol with a concentration of ≥95% to the surface and let it volatilize naturally.
Judgment criteria: No discoloration and no powder precipitation (Verify the ability of the coating to resist static alcohol corrosion, which is different from the friction test).
3. Rubber resistance test (simulating physical friction)
Tools and parameters: 1F/EF74 hardness rubber, 500g weight, 80 back-and-forth movements.
Judgment criteria: No leakage at the bottom (the rubber hardness and the number of times correspond to the friction scenarios in daily use to ensure that the coating will not be easily worn).
4. Cross-cut adhesion test (to verify the adhesion of the coating)
Tools and steps: Use a cross-cut knife with a 1mm spacing to make 100 cuts → Stick 3M 600 tape (press for 1 minute) → Rapidly pull the tape off at a 90° angle;
Judgment criteria: Paint peeling area ≤ 5% (1mm spacing is the international standard. 3M 600 tape has stable adhesion to avoid misjudgment).
5. Pencil hardness test (verify the hardness of the coating)
Tools and parameters: 2H pencil (with the tip flattened), 500g weight, draw a 3mm straight line at a 45° angle.
Judgment criteria: No scratches after erasing (the 2H pencil corresponds to daily minor collisions to ensure that the coating will not be easily scratched).
6. Painting appearance control
Appearance parts (such as surface X and surface Y): Control according to the appearance grade surface of the corresponding plastic parts (for example, if surface A of the plastic part requires "no visible defects", the same area of the iron part needs to meet the same standard).
Internal visual inspection parts (such as surface Z and surface Z1): Judge by comparing with the sample parts or limit samples. "Excessively obvious defects" (such as large - area paint runs and severe orange - peel texture) are not allowed.
(III) Other key projects
1. The cut surface is rusty
Test method: Wipe the cut surface (such as the stamping cut) with a dust-free cloth.
Judgment criteria: Rust spots shall not fall off (the cut surface is the only exposed base material area. Slight rust is allowed, but there shall be no loose rust debris to avoid contaminating other components).
2. Deformation amount
Requirements: Strictly control according to the tolerances marked on the customer's drawings (e.g., flatness ≤ 0.5mm). Verify with a dial indicator or fixture. If the tolerance is exceeded, it is NG.
3. Heavy industry standards
Color requirements: The color of heavy workpieces shall be consistent with the limit sample approved by the customer.
Scope requirements: The size of the heavy - work area is not limited, but it is necessary to ensure that "there is no obvious separation line between the touch - up paint area and the original paint".
V. Special Specifications for Paint Repair Products
Touch-up painting is a process for repairing defective painting and shall meet the following requirements:
Spraying condition: There are no obvious dividing lines in the touch-up paint area (judged according to the lighting and visual conditions of this specification. In case of disputes, the Limit Sample shall prevail).
Color difference requirements: The color difference between the paint - repaired area and the original paint ≤ 1.5 (△E of the area slightly wider than the original paint < 1.0 to ensure visual consistency);
Cleanliness: No black powder should be left on a white glove after wiping (to avoid the appearance being affected by residual paint residue).
Function retention: The engraved characters and symbols are clearly distinguishable (touch-up paint should not cover or blur the markings).
Final inspection: The paint-repaired parts shall pass all the tests of the raw materials (such as alcohol rub resistance test and cross-cut test) without reducing the quality standards.
VI. Detailed rules for defect determination (divided by area)
Defect type Specification requirements Side X (front) Side Y (top/left and right) Side Z (screw holes) Side Z1 (bottom) Remarks
Colored dots (specks/bumps) P < 1.5 mm², spacing ≥ 10 cm not counted 8 pieces 5 pieces not counted p = area, d = spacing
1.5≤P＜2.0mm², spacing ≥10cm 8 pieces 5 pieces 3 pieces Not counted
Heterochromatic dots (black/white specks) P < 0.5 mm², spacing ≥ 10 cm 8 10 not counted not counted
Burrs ≤0.06mm and non - falling off Not allowed Not allowed Allowed Allowed Based on "invisible to the naked eye within 100cm"
Dirt/Oil stains Any area Not allowed Not allowed Not allowed Not allowed Zero tolerance, affects appearance and assembly
Rust stains Do not fall off after wiping the cut surface OK OK OK OK Not allowed on non-cut surfaces (e.g., painted surfaces)
VII. Exemption Rules for Special Areas
The following areas are allowed to have certain defects due to "low visibility or no impact on functionality":
1. LOGO area: Zero tolerance within 20mm (visual focus);
2. AC IN & KEY - PAD area: It is OK if the base material is exposed under the R - corner (covered by accessories).
3. Lable area: Dents/scratches (which do not affect pasting) are allowed, but cracks/bulges (which affect the flatness of the Lable) are prohibited.
4. Heat dissipation hole area: Each hole can have a maximum of 2 chipping points, and there should be no more than 6 chipping points on the same piece, with a spacing of ≥10 cm (it is not the visual focus, and minor defects do not affect the function).
VIII. Dispute Resolution
If there are objections to the determination, handle them according to the following priorities:
1. Samples recognized by R&D;
2. Limit Sample confirmed by the customer;
3. IQC Sealed Sample.
This specification shall come into effect as of the date of issuance. Any revision shall be confirmed by the three parties of R&D, QC, and suppliers.
Judgment criteria for strip-shaped compression injuries
A strip-shaped crush injury refers to a squeezing injury with a linear distribution on the surface (no obvious depressions or protrusions, only presenting as linear marks). Its quality acceptance threshold is a length ≤ 30mm — that is, when the length of the strip-shaped crush injury does not exceed 30 millimeters, it is considered qualified; if the length exceeds 30 millimeters, it is directly judged as unqualified (no additional evaluation of other parameters is required).
Judgment criteria for non - perceptible scratches
The core definition of non - perceptible scratches refers to surface scratches that are not felt as uneven when touched by hand (only visible visually with no difference in physical tactile sensation). Requirements should be clearly specified in two categories based on the color characteristics and length of the scratches:
1. Non - tactile scratches with different colors: The color of the scratch is significantly different from the color of the substrate (e.g., the substrate is white and the scratch is gray), and there is no tactile sensation. Such scratches need to be directly evaluated according to the different - color clause in the "Judgment criteria for non - tactile scratches" (usually, additional restrictions on width or location are required, such as width ≤ 0.1mm and not in the functional area).
2. Ordinary non - perceptible scratches: Scratches whose color is the same as that of the substrate but with a length of 30mm. Such scratches need to be strictly judged according to the supplementary conditions in the "Judgment Standard for Non - perceptible Scratches" (e.g., width ≤ 0.2mm, no bifurcation, not in the key area, etc.). Ordinary non - perceptible scratches that do not reach 30mm are considered qualified by default.
Judgment criteria for pressure injuries without sensory perception and with the same color
Non - tactile and color - matched indentation is a squeezing damage that has no tactile sensation and the color is completely the same as that of the substrate (only visible under specific light or filters). Its qualification requirements need to meet three conditions simultaneously:
1. Visual concealment: When observed through a 25% filter (a neutral gray filter with a light transmittance of 25%), the bruises are completely invisible. If traces can still be seen under the filter, it is directly judged as unqualified.
2. Dimensional parameters: The characteristic parameter P of the crush damage
3. Density limit: ① Local density: In an area of 100 mm² (about the size of a fingernail), a maximum of 2 such indentations are allowed. ② Overall density: The total number of non - perceptible same - color indentations on the entire surface material shall not exceed 5. If either density limit is exceeded, it will be judged as unqualified.
Judgment criteria for scratches and exposed substrate scratches
This type of damage belongs to a serious defect, and there is no room for concessionary acceptance.
1. Scratches and dents: Scratches with tactile sensations caused by collisions and friction (with obvious unevenness or deformation on the surface, such as scratches left by nail scraping). Regardless of the length, width, or location, they are directly judged as non - conforming (NG).
2. Scratches exposing the substrate: Any scratch that damages the surface coating or the substrate, resulting in the exposure of the substrate (for example, if the coating is black and the white substrate is exposed after scratching) - even if the scratch is only 1mm in length and 0.05mm in width, as long as the substrate is exposed, it is not allowed at all and shall be directly judged as unqualified.