The structure, material and strength of the barrel of the injection molding machine

I. Injection molding machine barrel structure

1.1 Integral barrel and combined barrel

The integral barrel is processed on the integral blank. This structure can easily ensure high manufacturing accuracy and assembly accuracy, simplify assembly work, facilitate the setting and installation of the heating and cooling system, and the heat is evenly distributed along the axial direction.

Combined barrel means that a barrel is composed of several barrel sections. Experimental extruders and exhaust extruders often use combined barrels. The former is to facilitate changing the barrel length to adapt to screws with different aspect ratios, and the latter is to set the exhaust section.

1.2 Bimetallic barrel

In order to meet the barrel material requirements and save precious materials, many barrels are inlaid with an alloy steel bushing inside the general carbon steel or cast steel matrix.

1.3 IKV barrel

The IKV barrel is a new type of barrel developed by the German IKV Institute, with the following characteristics:

Longitudinal grooves are opened on the inner wall of the barrel feeding section or processed into a taper to improve the solid conveying rate.

Force cooling of the barrel in the feeding section to maintain the solid friction properties of the material.

1.4 Shape and position of the feeding port

The shape of the feeding port and its opening position on the barrel have a great influence on the feeding performance. The feeding port should enable the material to be freely and efficiently added to the barrel without bridging. When designing, it should also be considered whether the feeding port is suitable for setting up a feeding device, whether it is conducive to cleaning, and whether it is convenient to set up a cooling system in this section.

II. Barrel material and strength calculation

2.1 Barrel material

The selection of barrel material depends on many factors, including:

**Processing performance: **The material should have good machining performance and heat treatment performance for easy processing and manufacturing.

**Wear resistance: **The material should have good wear resistance to resist the wear of plastic particles.

**Corrosion resistance: **The material should have good corrosion resistance to resist the corrosion of plastic melt.

**Strength: **The material should have sufficient strength to withstand high pressure and high temperature.

Common barrel materials include:

45 steel: It has good comprehensive performance and moderate price, and is a commonly used barrel material.

40Cr: has high strength and wear resistance, suitable for processing high hardness plastics.

38CrMoAL: has high strength and corrosion resistance, suitable for processing corrosive plastics.

Cast steel: has low cost, suitable for processing large barrels.

Ductile iron: has good wear resistance and corrosion resistance, suitable for processing glass fiber reinforced plastics.

Xaloy alloy: is a new type of wear-resistant and corrosion-resistant material with good comprehensive performance, but the price is high.

2.2 Determination of barrel wall thickness and strength calculation

Determination of barrel wall thickness

The determination of barrel wall thickness mainly considers the following factors:

**Strength:**The barrel wall thickness should be sufficient to withstand high pressure and high temperature.

**Processability:**The barrel wall thickness should be easy to process and manufacture.

**Thermal inertia:**The barrel wall thickness should be able to ensure sufficient thermal inertia to reduce temperature fluctuations.

Barrel strength calculation

Barrel strength calculation is carried out according to thick-walled barrels. For specific calculation methods, please refer to relevant standards or specifications.

III. Precautions for barrel design and manufacturing

Barrel design

When designing the barrel, the above factors should be fully considered, and appropriate materials and structures should be selected.

Attention should be paid to the sealing of the barrel to prevent leakage of the plastic melt.

The convenience of repair and maintenance of the barrel should be considered.

Barrel manufacturing

The manufacture of the barrel should comply with relevant standards and specifications.

Attention should be paid to the surface finish of the barrel to reduce the friction resistance of the plastic melt.

Attention should be paid to the heat treatment of the barrel to improve its strength and wear resistance.

IV. Maintenance and care of the barrel

Barrel maintenance

Regularly check the wear of the barrel and replace the seriously worn parts in time.

Clean the barrel regularly to prevent the plastic melt from remaining.

Regularly check the sealing of the barrel to prevent the plastic melt from leaking.

Common barrel failures

Wear: This is the most common failure of the barrel, and the main reason is the wear of the plastic particles.

Corrosion: This is another common failure of the barrel, and the main reason is the corrosion of the plastic melt.

Cracking: This is a serious failure of the barrel, and the main reason is overload or excessive thermal stress.

Barrel troubleshooting methods

**Wear:**Replace severely worn parts.

**Corrosion:**Replace severely corroded parts, or apply anti-corrosion coating on the inner wall of the barrel.

**Cracking:**Replace cracked parts.