Stadium seats in sports venues can be divided into injection-molded seats (includes gas-assisted injection molding), blow-molded seats, wooden seats, metal seats, upholstered seats, and genuine leather seats based on their materials. While seats made from wood, metal, soft bags, and leather seats are very easy to distinguish and compare, it is likely to confuse injection-molded seats with blow-molded seats. So what are blow molding and injection molding?

1. Blow Molding:

The manufacturing process of blow molding：

The basic principle of blow molding is to inflate a softened hot-molded plastic preform against the cooled surface of a closed mold, allowing the blown preform to solidify.

Specific steps of blow mounding:

 Step 1: Heating the plastic to soften it, then extruding it through an extruder to form a long, thin-walled tube called a parison.
Step 2: Loading the parison into the mold, which typically consists of two semi-circular components that sandwich the parison.
Step 3: Inflating the parison by injecting air into it, causing it to expand and conform to the surface of the mold.
Step 4: Cooling, allowing the parison to solidify, forming the plastic product.

Material for injection molding:

HDPE material is the most common for Blow-molding manufacturing.

2. Injection Molding:

The basic principle of injection molding:

 The process of injection molding is to use the screw or column of the injection machine to make the molten material in the barrel pass through the nozzle of the injection machine and the gating system, injecting it into the cavity and solidify it.

Material for injection molding:

Seats that use injection molding aften adopt HDPP material.

3. Gas Assist Injection Molding

The basic principle of gas-assisted injection molding:

Gas-assisted injection molding is to inject high-pressure argon directly into the plasticizing plastic in the mold cavity through the main and auxiliary controllers (segmented pressure control system), so that the interior of the plastic part expands and becomes hollow, but the product and shape are still intact. . Because the gas is not injected into the plastic, it does not form pores inside the finished product. Make the product eliminate the sag of the finished product and keep the surface of the finished product smooth, reducing warping and deformation.

Summary of understanding 3 modings

1. Blow-molded products are hollow, while injection-molded products are solid.
2. Injection molding molds are fine in texture, precise in size, and better in compression resistance.
3. The traditional internal injection molding system directly injects gas into the middle of the molten material, while the external gas-assisted injection system selects a specific product surface and injects gas between the mold wall and the molten material, so that the gas is directly pressurized on the cooled plastic surface, reducing dissolution lines and warpscaused by hollow mold cavity when plastic is cooled. The product has better impact resistance, toughness, mechanical strength and chemical stability, so compared with pure injection molding products, gas-assisted injection molding products are more favored by customers.

The advantages and disadvantages

Advantages and disadvantages of blow molding:

• Advantages:

Simple structure, relatively light seat, affordable price.

• Disadvantages:

The function is relatively simple, the appearance is average, and the grade is relatively low. But the quality of good blow molded seats is not low, the cost of good blow-molded seats is relatively high.

Advantages and disadvantages of (gas-assisted)

injection molding

• Advantages:

Accurate size, beautiful surface, seat can realize more functions, improved comfort, enhanced pressure resistance, enhanced impact resistance, and the seat of gas-assisted injection molding is more reliable and wear-resistant, and its flame retardant performance reaches B1 level, which means its harmful material emissions <E1.

• Disadvantages:

More complex structure and relatively high cost.

Distinguish blow molding from injection molding

1. By material: PP material has the advantages of not easy to deform, good impact resistance, and weather resistance. This material is commonly used in injection molding, which is more beautiful and more expensive. Blow molding is basically made of HDPE, and the price of this product is relatively economical.
2. By price: Because the purchase cost of blow molding equipment is much lower than that of injection molding equipment, and the process of blow molding is simple, and the cost of mold development is also low. Of course, the materials used are relatively economical, so injection molding seats are more than blow molding. Plastic seats are more expensive.
3. By surface: The surface of injection molding products is smooth, the texture is better than blow molding products, and the compression resistance is also better than blow molding.
4. By details: The blow molding structure is relatively simple, and there are not many places that can be adjusted, especially the inclination adjustment. Injection molded parts are assembled by multiple small molds, the structure is relatively complex, and many functions can be realized, such as multiple height adjustments and multi-level angle adjustments.
5. Gas-assisted injection molding seats are safer, more comfortable, more functional, and more upscale in appearance. Reasonably, the price is also higher. Of course, good quality blow molding products is not low, and the cost is relatively high.