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DEVELOPMENT OF REGRIND PROCESSING

The first step of regrind processing is understanding the reasons for scrap production. Scrap is a waste of material and machine time.

In the world of plastics production, profit margins can be quite narrow. Plant success is highly dependent upon production systems execution. There is no question whether the reintroduction of scrap materials into the molding system is necessary. Failure to recapture material losses due to start up, defect production and press shut down can cripple a company’s profit margin.

But first, a company must understand that scrap is produced by not controlling the overall process and production of the organization. Scrap is not inevitable. It is the result of poor monitoring, control and failed processing approach.

This article will explain the pros, cons and procedures of regrind processing. There is of course a need to reprocess lost materials to reduce the costs of materials lost to the production of scrap. But there also needs to be an understanding that scrap prevention is the first and most profitable response. Scrap is lost product, which increases machine time during a production run. A company’s primary goal is to first eliminate scrap, thus increasing productivity and profits.

SCRAP DATA AND APPROACH

The first steps in scrap reduction revolve around scrap data. What jobs are producing scrap, and why is scrap being produced? Scrap is never an “acceptable” condition! Look to the rules of 5M for answers. Is the scrap a result of: Man, Mold, Material, Machine or Method (Process)? These simple steps can often reveal what the actual cause of scrap might be, which will help your technical support team to develop solutions for eliminating scrap events.

It is important to note that eliminating scrap is not easy. Every company has its own set of scrap producers which will require a fundamental approach to reduce, if not eliminate scrap events. But in every scrap situation, there needs to be a clear understanding that accepting scrap as a normal factor of production only accepts applying “band-aids” as a normal in the scheme of production. Make a list of your top 5 scrap producers. Evaluate the reasons for scrap events. Develop a plan to remove scrap from the equation.

MATERIAL CANDIDATES FOR REGRIND USAGE

One of the most important considerations in developing a regrind approach is material type, and visual aesthetics. Class “A” parts can be adversely affected by regrind usage. Lower ratios of regrind may be used successfully, but sampling must take place to determine the best approach.

Material blends are another factor that must be considered. Talc, mineral-filled and glass-filled materials may require lower regrind ratios. Drying might be required in some cases.

Glass-filled materials may require generational monitoring. Each time this type of material ground, the length of the glass fiber is shortened. This can affect process, as well as part impact and shrink properties.

Clear Polycarbonate regrind can be used, but it is important to note that regrind use can affect part clarity, which in optical applications is a critical component.

The following materials are great candidates for repurposing:

  • Polypropylene
  • Polyethylene
  • Styrene
  • ABS
  • PC/ABS
  • Polycarbonates (colored/ non-opticle)
  • Nylon (Glass content must be considered when determining ratio)

REGRIND APPROACHES AND PROCEDURES

While working on eliminating scrap from your facility, there is still a need to recoup lost materials, The following points are crucial when repurposing materials for reproduction.

  • Grinder selection is key to press-side reprocessing. Regrind granules need to be uniform, to assure that virgin-regrind blends are consistent during the reprocessing event.
  • Reprocessed regrind is the most effective way to assure process consistency. Materials should be re-extruded with virgin base added to improve process consistency. Both the virgin material and reprocessed blends should have separate validated processes to assure process control.
  • Regrind reintroduced at the press should be processed through a blender to assure mix ratio consistency. Virgin/ Regrind ratio should be based on the ability to maintain upper/ lower control limits in the established process window
  • It is important to note that press-side regrind usage is prone to housekeeping issues. There is a certain amount of material dusting and upkeep that has a direct relationship to at-the-press regrind use. Processing regrind in an enclosed grinding area to be reprocessed helps to eliminate much of the mess from the floor.
  • Keeping reground materials free of contaminents and cross- contamination with other materials is critical to reprocessing. Extensive training of all personnel who will be involved in the reuse process is critical to the success of repurposing material.

The first step towards regrind processing is the elimination of scrap from the production floor entirely. When regrind use is required, assure that your facility plans its reprocessing plan carefully to assure that end result is full use of materials lost during the production process. Material reuse is not the preferred method of production control. But controlling material losses is key to assuring company ROI’s are met.

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