by Purging Compounds: An Effective Solution to Clean Plastic Molds and reduce Production Downtime
A purging compound is a specialized material that is used to clean thermoplastic injection molds and extrusion equipment. Composed of thermoplastic resins and additives, these compounds are designed to flow easily through an injection molding or extrusion machine, removing traces of prior materials from the processing system. By thoroughly clearing out residual polymers, these compounds help reduce contamination between jobs and minimize production downtime.
Types of Purging Compounds
These compounds are available in different formulations suited for specific resin types and production requirements. Some common varieties include:
– Polyolefin PCs for cleaning molds used with polypropylene (PP) and polyethylene (PE). These purge easily at temperatures matching PP and PE processing.
– Polyester PCs formulated for use with polyesters like polyethylene terephthalate (PET). Thermally stable at higher temperatures required for polyester processing.
– Nylon PCs designed for nylon materials like nylon 6 and nylon 6,6. High viscosity helps these compounds effectively remove traces of nylon from molds and screws.
– Thermoplastic Elastomer PCs suited for thermoplastic elastomers like thermoplastic polyurethane (TPU) and styrenic block copolymers. Allows thorough purging at lower processing temperatures.
– All-Resin PCs capable of clearing multiple resin types like polypropylene, polyamide and polycarbonate from processing equipment. Useful when frequent changes in resin are required.
Benefits of Using PCs
Regular usage of PCs in injection molding and extrusion lines provides several advantages:
– Reduces Contamination: Purging removes residue from prior materials, minimizing cross-contamination between jobs and batches. This improves product purity and reduces rejects.
– Prevents Machine Downtime: Thorough clearing of molds and screws with purging compounds significantly cuts downtime required for changeovers. Less manual cleaning is needed.
– Improves Product Quality: Eliminating remnants of prior resins from molds and screws helps maintain consistent material properties, colors and specifications in output parts.
– Extends Equipment Lifespan: Regular purging protects expensive molds and plasticating units from corrosion and wear caused by residual polymers. This enhances equipment performance over time.
– Saves on Production Expenses: Less contamination results in higher output rates and fewer rejects, directly cutting operational costs. Quick changeovers through purging further reduce lost hours.
How these Compounds Work
The purging process starts by first heating the plasticating unit – the injection barrel, screw and molds – to a temperature appropriate for the purging compound being used. The purging compound is then manually loaded into the injection hopper or gravimetrically dosed for fully automatic purging.
Once temperatures equalize, the compound is plasticized by shear forces inside the heated screw, transforming it into a fluidized state. Turning on the injection unit pushes the purging material through the nozzles and into all mold cavities as well as residual areas inside molds.
While still molten, the purging compound effectively wets all surfaces and reaches tight, intricate areas to lift and flush away any trapped polymer particles. Purging continues until the mold fully ejects clean, virgin compound pellets indicating a successfully cleared system. The process typically takes just a few cycles.
Implementing an Effective Purging Program
To consistently reap the benefits of purging, manufacturers establish standardized purging protocols optimized for their specific production needs. Key elements of an effective purging program include:
– Determining the best purging compound chemistries for each resin family processed. This ensures compatibility.
– Setting purging frequency guidelines based on resin changes, production volumes and downtime targets. Purging after set parts counts is common.
– Calibrating machine controls to heat barrels, screws and molds to precise purging compound melting temperatures.
– Establishing clear SOPs for loading purging compound, starting purge cycles and verifying clean outputs.
– Training operators to follow SOPs step-by-step without variation each time.
– Maintaining comprehensive records of all purging event details for traceability and continuous improvement.
With diligent execution of a well-designed purging program, manufacturers realize major benefits in productivity, quality and total cost of production. PCs are an indispensable solution for any plastic processor seeking a highly effective method to clean molds and reduce equipment changeover times.
*Note:
1.Source: Coherent Market Insights, Public sources, Desk research
2.We have leveraged AI tools to mine information and compile it
Money Singh is a seasoned content writer with over four years of experience in the market research sector. Her expertise spans various industries, including food and beverages, biotechnology, chemical and materials, defense and aerospace, consumer goods, etc.
