1. Injection molding product testing and inspection at injection molding factory
1.1 Inspection methods of injection molding products at our injection molding factory
1.1.1 The principle of product qualification
A) Does not affect the application of the product to the end user.
B) Does not interfere with post-process or customer assembly and processing.
C) Does not affect aesthetics.
1.1.2 The concept of First article inspection, in-process quality control and Finished product inspection(FQC)
●First article inspection
A) Purpose: to make the injection molded components meet the design and customer requirements and prevent batch scrap.
B) The first inspection time is before each production batch, after material change, after exception handling(mold repair, insert changed, ejector pin changed).
C) Note for the first inspection:
Before sending the first inspection, the workshop technician must do a good self-inspection:
check whether the product matches the drawings and other requirements, especially pay attention to structural issues; color matching; no obvious injection defects in appearance; Check assembly and functionality (especially new products, mold repaired, insert changed, ejector pin changed, injection parameters changed).
●in-process quality control
A) Purpose: timely detection of abnormalities in the injection modling process to prevent batch scrapping.
B) The inspection time is 3 shots per each machines per each two hours.
C) Note for the in-process quality inspection:
Support operation and production trouble shooting solution in many ways, such as machine, material, operator, method, management factors, to identify abnormalities, analysis of abnormalities, to solve abnormalities
●Finished product inspection(FQC)
A) Inspection timing: the injection modling workshop has produced finished products, placed them in the area to be inspected, and the operator informed the quality inspection guys.
B) Sampling standards: Sampling according to customer requirements; sampling according to enterprise specifications if customers do not require.
C) Inspection includes labeling, material, appearance, size, assimilability, and packaging etc.
1.2 Inspection standards of injection molding products at our injection molding factory
1.2.1 Inspection environment
A) room temperature 20℃±2, humidity between 30%~80% (no condensation).
B) Place the product under 40W fluorescent lamp or 60W ordinary light bulb 0.8~1m position, in 45°~135° direction, both eyes 30~45cm from the product,The visible face stays 3~5s, and the other face 2~3s.
1.2.2 Product inspection level classification
Ⅰ: Products refer to products that do not require painting, such as DVR, wall box cover, satellite switch glue tray, PHLIPS antenna and other products for indoor use with high surface requirements;
Ⅱ: Products refer to products that require painting and outdoor products.
1.2.3 Classification of products in different positions
A-Surface:The part that is visible during normal product operation, such as the top cover, front end and interface area.
B-Surface:The surface that is not often visible in normal product operation, such as the side of the product.
C-Surface:Tthe surface that is not visible in normal operation, such as the bottom of the product.
D-Surface:The non-exposed surface of the product structure, such as the inner surface of the product and the internal structural components.
1.2.4 defects level of injection moulded products
Fatal defects (Grade A)
Defects that can cause harm or be unsafe to the product user.
One or more fatal defects are called fatal non-conforming products; such products should be strictly limited (not allowed to leave the factory) to eliminate the defect. If the user finds a fatal defective product, you can reject the (batch) of products.
Due to fatal defects caused by user losses and hazards, injection molding factory will not only lose their reputation and cause great economic losses but also bear legal responsibility.
Serious defects (B level)
Although it will not constitute the same consequences as fatal defects, it will not cause harm to the user. Still, it can cause failure or seriously reduce the product’s performance, greatly reducing its expected function.
One or more serious defects, not including fatal defects in the product, is called a serious non-conformity.
Minor defects (Class C)
Only a slight impact on the application of the product performance or almost does not constitute a defect.
One or more minor defects without fatal defects and serious defects of the product are called minor non-conforming products.
There are also quality defects according to the severity of the four levels: fatal, serious, general, and minor.
1.2.5 Classification of defects in injection molding product inspection
Wrong material, mixed material, unconfirmed large proportion of Sprue material (Serious defect).
Minor appearance defects:
Scratches, shrinkage, material flow mark, color difference, ejector mark etc on the B and C surfaces of Ⅰ level products and A, B and C surfaces of Ⅱ level products.
Serious appearance defects:
Scratches, shrinkage, material flow mark, color difference, ejector mark, welding line that affects assembly etc on the A surfaces of Ⅰlevel products and Ⅱ level products.
Product construction (assembly) defect:
Resulting in product not being assembled or failure to achieve the expected function,For example: serious misalignment of the upper and lower covers after assembly, mismatch of the screw teeth, cracking after locking the screw,etc.
Product performance defects:
Defects that cause the product failed to meet the expected function of the design. For example: paint peeling, plating plating off, steel hardness, strength failure, electrical connection breakage, short circuit, attenuation reflection is not up to standard, etc.
May cause the product to appear scratches or not implemented according to the requirements of the corresponding packaging materials protective film, plastic bags etc.
1.2.6 General judgment principles
A) During the molding process of injection molded parts, we inspect the products and control the production with the concept of “zero defect”, and help the molding workshop to analyze the root causes of each defects.
B) If there are minor defects in the appearance of the produced injection molded parts, but the customer agrees to accept them and they do not affect the assembly, we can say OK.
C) Defective products causing poor assembly (hole cracking, difficult to locking screw, scorching, deformation affecting assembly, large joints, fracture, fastening is not tight, misalignment etc) shall be rejected.
1.2.7 Inspection techniques for injection molded parts
●Surface without burrs, welding lines, bubbles, flow marks, deformation, scratches.
●No Color difference (pay attention to the check assembled parts).
●No any marks/issues at gate position.
●No Flash around parting lines, insert lines.
●No plugging, hole (big or small), deformation, whitening, welding line at screw hole position.
●There should be no cracks or fractures in the joints.
●Go NO GO thread gauge required, pin gauge required.
Test assembly, functional and spraying.