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What is the Difference Between Injection Molding vs Thermoforming?

Table of Contents

Generally speaking, thermoforming vs injection molding use different equipment, different materials, different mold structures, different molding methods, and different prices.

Thermoforming is mainly used for products with simple structure, single-sided molding, and low volume, and the mold is very cheap, only 1/5 of the cost of injection molding, and the opening time for products of similar complexity is only 1/2 of injection molding.

Injection molding requires molten liquid polymers, through custom plastic injection molding machine high pressure into the mold, cooling molding. Generally suitable for large volumes, high precision products, the tooling costs are very high ( tooling material like steel, beryllium copper alloy, and heavy aluminum).

Injection molding and thermoforming are two popular methods of manufacturing plastic products. But what’s the difference between them? In this blog post, we will discuss the pros and cons of each manufacturing process, and help you decide which is right for your business.

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What is thermoforming?

Thermoplastic molding is a kind of thermoplastic sheet processing into various products more special plastic processing methods.

This molding process mainly uses a vacuum suction vacuum pump generated after heated plastic sheet through the thick wall of the mold into a variety of shapes of vacuum cover or stick attached to the appearance of products in various shapes.

In the market, there are more and more thermoforming products, such as bottle caps, cups, dishes, food plates, toys, hats, automobile parts, architectural decoration parts, chemical equipment, and so on.

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Thermoforming Different Types

There are a variety of thermal forming methods but are based on vacuum, air pressure, or mechanical pressure three methods to be combined or improved.

Vacuum forming

There are dozens of thermal forming methods, vacuum forming is one of its representatives.

The sheet softened by heat is formed by a vacuum against the surface of the die. This method is the simplest, but the pressure difference caused by vacuum is not large, only for simple products.

Air pressure thermoforming

Compressed air or steam extreme pressure is used to force the sheet, which is softened by heat, to be formed against the surface of the die. Because the pressure difference is larger than that of vacuum forming, it can make more complicated products.

Hot molding of the die

The sheet softened by heat is placed between a pair of male and female plastic molds and molded by mechanical pressure. This method of forming pressure is greater, can be used to manufacture complex products, but the up front cost of the male and female mold is higher.

Plunger assisted molding

Parts of the heated sheet are pre-drawn with a plunger or a male die, and then molded by vacuum or air pressure, and the products with large depth and uniform wall thickness can be made.

Solid-phase forming

The sheet is heated to a temperature not exceeding the melting point of the resin so that the material remains in a solid-state. Used for ABS resin, polypropylene, high molecular weight high-density polyethylene. The rigidity and strength of the products are higher than those of the general thermal forming products.

Double sheet hot forming

Two pieces superimposed together,the middle of the air blowing can make large hollow pieces.

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Thermoforming process classification

Thermoplastic forming according to the varying thickness of the sheet is divided into thin section thick wall and thick wall thick wall blister.

Thick wall vacuum

A thick wall blister refers to the original data thickness of more than 2mm, can not be in the full active machine blister molding, it is necessary to choose thick plate special semi-active blister molding machine processing production skills.

Thick blister products generally have the characteristics of large area, large height, and thick data.

Thick wall blister and thin wall blister products are almost the same way of production, are based on vacuum blister mold forming.

Most of these plastic products are widely used in car watch interior decoration, transportation, building materials, packaging, medical equipment, household appliances, sanitary ware, sports goods, and Other People’s Daily categories.

Thick sheet blister processing principle and conventional blister process are common, the plastic sheet is cut into a certain scale heating softening, with the difference of air pressure on both sides of the sheet or mechanical pressure, so that the deformation of the cover posted on a specific mold, through cooling shaping, and trimming demand products.

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Thin wall vacuum

The thickness of Thin Blister is 0.14 ~ 5.0mm, mainly PVC, PP, PS (HIPS), PET (including APET and PETG), PE, BOPS, and other materials.

Widely used in food, medicine, electronics, toys, computers, daily necessities, cosmetics, mechanical hardware, and other industries.

Diagram of the thermalforming process

General process: heated plastic sheets — cutting — sheet fixed — heating — molding — demolding — cutting edge — the finished product

Material requirements for thermalformal

  1. Thermoforming can only produce uniform wall thickness products, (general bevel slightly thin), can not be made of plastic products with a wide gap in wall thickness.
  2. The wall thickness of thermal molding is generally within the range of 1 to 2mm or thinner (small packaging with blister packaging sheet thickness is most commonly used for 0, 15 to 0, 25mm).
  3. The tensile strength of thermoforming products is limited to a certain extent. The diameter depth ratio of plastic containers formed by blister is generally not more than 1, and in extreme cases, it shall not exceed 1.5.
  4. The dimensional accuracy of hot forming is poor, and the relative error is generally more than one percent.

What is injection molding?

Injection molding is an injection molded method. As for injection molding, plastic pellets are fed through the machine past a heating element where they are melted. The molten plastic is then injected into a double-sided mold. The advantages of the injection molding method are fast production, high efficiency, the operation can be automated,

There are many varieties of colors, shapes can be from simple to complex, sizes can be from large to small, and the size of products is accurate, products are easy to update, can be shaped into complex parts,

Injection molding is suitable for mass production and complex shape products and other molding processing fields. At certain high temperatures, completely melted plastic material and molten plastic parts material are stirred with a screw.

High pressure shot into the mold cavity, after cooling and curing, the method of forming injection molded product. This method is suitable for the mass production of complex plastic parts and is one of the popular manufacturing processes methods.

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The plastic injection molding process

The injection molding process can be roughly divided into the following 6 stages.

The injection molding process mainly consists of six stages: mold closing – filling – holding pressure – cooling – mold opening –Demolding and other 6 stages.

These six stages directly determine the molding high quality products, and these six stages are a complete continuous process.

The above process is repeated, and the products can be produced in batch cycle.

Conclusion

While thermoforming is typically used for large-scale mold design and shorter production runs, plastic injection molding is often a better choice for small, complex parts and high volume production runs.

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Thermoforming vs injection molding

Unique Advantages: a simple right method, less investment in equipment and thermoforming molds has lower tooling costs, can manufacture products with a larger surface.

Disadvantages: lower and smaller production quantities efficiency, high raw material cost, more processing procedures after products.

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