The size of the refrigerator liner is unstable? The mold and process are the key

In the refrigerator manufacturing process, the precision of the inner tank size is directly related to the assembly effect, sealing and user experience of the whole machine. In actual production, the unstable size of the refrigerator inner tank is a common problem, and the root cause is often due to mold manufacturing, injection molding process control and plastic raw material characteristics.

1. Mold manufacturing factors

The mold is the core equipment for forming the refrigerator liner. Its precision and stability determine the dimensional consistency of the product. Common problems include:

1. Insufficient processing accuracy

During the manufacturing process, the mold is affected by machine tool accuracy, tool wear, programming errors and manual operation, which can easily lead to the cavity size not matching the design value, resulting in deviation in the molded part.

2. Internal stress and deformation of materials

Mold steel may have residual internal stress after heat treatment or cutting. If it is not fully released, it will deform when exposed to heat or pressure during use, thus affecting the accuracy of the finished product.

3. Assembly error

The mold structure is complex and consists of multiple parts. If the slider, ejector pin, guide pin and other parts are not assembled accurately, it will affect the opening and closing accuracy of the mold and cause inconsistent sizes of the finished product.

2. Injection molding process factors

In addition to the design accuracy of the mold, the influence of injection molding parameter control on dimensional stability cannot be ignored:

1. Unreasonable temperature control

Inconsistent or large fluctuations in barrel temperature and mold temperature will affect the fluidity and molding shrinkage of the molten plastic, thereby causing dimensional fluctuations.

2. Injection and holding pressure are unstable

Too low injection pressure may lead to insufficient filling, while insufficient holding pressure may lead to failure to compact the product. Both may cause the product size to become smaller or uneven.

3. Improper cooling time control

If the cooling time is too short, the product will be demoulded before it is completely shaped, which may cause deformation; if the cooling time is too long, it may cause excessive shrinkage and affect dimensional consistency.

3. Plastic raw material factors

Even with good tooling and process control, differences in raw materials can cause dimensional instability in the finished product.

1. Difference in material shrinkage

Different types of plastics (such as HIPS, ABS) naturally have different molding shrinkage rates. Even for the same type of plastic, the shrinkage rate will vary due to differences in brand, additives, drying degree, etc. If the mold design does not accurately reserve shrinkage compensation, it is very easy to cause deviations.

2. Poor material batch stability

Raw materials from different supply batches, differences in molecular weight distribution or water content may also affect melt flowability and final dimensional stability

IV. Summary and suggestions: System optimization to ensure the consistency of liner size

To solve the problem of unstable size of refrigerator liner, it is necessary to start from multiple links such as mold design and manufacturing, injection molding process parameters, material selection and management , and achieve systematic optimization.

suggestion:

Pioneer

Pioneer’s experience in polyurethane foaming and injection molding equipment shows that in order to obtain consistent and stable refrigerator liner dimensions, it is necessary to achieve a high degree of linkage and precise control of molds, materials and injection molding parameters:

• High-precision foaming system : high injection metering accuracy ensures uniform foam filling and reduces dimensional problems caused by filling volume fluctuations;
• Modular mold design service : supports multi-cavity symmetrical injection, and the mold rigidity and exhaust path are optimized to ensure molding consistency;
• Automatic parameter management system : controls injection temperature, pressure and cooling rhythm, improves process repeatability and reduces the risk of human error;
• Data traceability : Key process parameters are fully recorded to facilitate quality tracking and continuous optimization.

Summary and recommendations