Rigid PP PS Washing Machine Housing Plastic Washing Line – Engineering Case Study

Project Context

In appliance recycling systems, washing machine housings represent a typical source of large rigid plastics, mainly composed of PP (polypropylene) and PS (polystyrene). These materials are structurally rigid and usually contain metal inserts, rubber parts, and labels, requiring size reduction and multi-stage washing before recycling.

This case involves a rigid plastic washing line designed to process post-dismantling washing machine housings and produce clean plastic flakes suitable for pelletizing preparation.

Input materials come from appliance dismantling operations with pre-sorting completed.

Material Input Characteristics

Typical material characteristics:

Engineering challenges include:

· Irregular shapes affecting feeding stability

· High rigidity requiring sufficient crusher torque

· Label removal through friction washing

· Metal contamination removal

Process Design Logic

The washing line follows a standard rigid plastic wet washing process:

Feeding → Crushing → Friction washing → Density separation → Dewatering → Thermal drying

Engineering considerations:

1 Size reduction before washing
Improves washing efficiency through increased surface area.

2 Mechanical cleaning before separation
Removes loose contamination before density sorting.

3 Staged moisture removal
Mechanical dewatering reduces thermal drying load.

This represents a typical rigid plastic washing line process design.

Equipment Configuration

Main equipment observed includes:

Feeding Conveyor

Function:

Transport housings into crushing stage.

Typical configuration:

· Carbon steel frame

· Wear resistant rubber belt

· Gear motor drive

· Variable frequency control

Typical widths:

800–1200 mm depending on material size.

Rigid Plastic Crusher

Function:

Reduce housing size to washing grade flakes.

Typical technical specifications:

Design consideration:

High rotor inertia improves crushing stability.

Friction Washer

Function:

Remove contamination through mechanical scrubbing.

Typical operating parameters:

Engineering role:

Removes:

· Stickers

· Labels

· Surface contamination

This unit is a key pre-cleaning stage.

Sink Float Separation Tank

Function:

Density based impurity separation.

Separation principle:

Typical structure:

· Steel tank body

· Screw discharge

· Bottom impurity outlet

· Water recirculation

Engineering benefit:

Reduces downstream wear.

Mechanical Dewatering Machine

Function:

Remove surface moisture.

Typical parameters:

Mechanical dewatering reduces drying energy demand.

Key Engineering Parameters

Typical design range: