The differences between an extruder and an injection molding machine

1. The working principle is different

1. Injection molding machine

   The working principle of the injection molding machine is similar to that of a syringe for injection. It uses the thrust of the screw (or plunger) to inject the plasticized plastic in the molten state (that is, the viscous state) into the closed mold cavity and obtain products after curing and shaping.

Injection molding is a cycle process, each cycle mainly includes: quantitative feeding - melt plasticization - pressure injection - mold filling and cooling - mold opening and taking out. After the plastic parts are taken out, the mold is closed again for the next cycle.

2. Extruder

   A single screw is generally divided into three sections in terms of effective length, and the effective length of the three sections is determined according to the diameter of the screw, the pitch, and the depth of the screw, which are generally divided into one-third each.

The last thread of the material port begins to be called the conveying section: the material here is required not to be plasticized, but it must be preheated and compressed. In the past, the old extrusion theory believed that the material here was a loose body. Solid plug, that is to say, the material here is solid like a plug after being squeezed, so as long as the conveying task is completed, it is its function.

2. The characteristics are different

1. Injection molding machine

The injection device and the clamping device are on the same vertical centerline, and the mold is opened and closed in the up-down direction. The floor area is only about half of that of the horizontal machine, so the productivity is about twice as much in terms of floor space.

2. Extruder

The safety items that the extruder should pay attention to when extruding are electricity, heat, mechanical rotation, and loading and unloading of heavy parts. The extruder workshop must be equipped with lifting equipment to assemble and disassemble heavy parts such as heads and screws to ensure safe production.

3. Different classification

1. Injection molding machine

Classification by plasticizing method:

1) Plunger plastic injection molding machine

Its kneading property is very poor, and its plasticizing property is not good, so a shunt shuttle device should be installed. Rarely used.

2) Reciprocating screw plastic injection molding machine;

Relying on the screw for plasticization and injection, the mixing and plasticizing properties are very good, and it is used the most.

3) Screw-Plunger plastic injection molding machine relies on the screw for plasticization and the plunger for injection, and the two processes are separated.

2. Extruder

Plastic extruders are divided into twin-screw extruders and single-screw extruders.