Over the years, purging compounds have come to play a crucial role in thermoplastic processing. They have become a vital tool to facilitate a number of market related factors such as enhancing reliability on just-in-time processes, enabling cost saving in competitive markets, allowing the use of advances additives colorants and resins; and improving reliability. While these compounds are primarily used for injection molding purging purposes, it has been found that they offer similar benefits to extrusion processes as well.
Quintessentially, it was believed that these compounds had more use in injecting molding purging, and wasn’t used in extrusion as frequently because of the design of the equipment and the simple fact that extrusion is a continuous process and not a cyclical process like the former. Nonetheless, engineers have been able to find a number of benefits in the use of purging compounds for an extrusion process-
1. In comparison to traditional methods of running thousands of pounds worth of virgin material through an extruder for the purpose of purging the previous material, it has been found that the material and colour changes can be executed much faster by the use of purging compounds.
2. Since injections molding purging compounds are developed to get rid of stronger colour deposits and carbon, they are more effective than regular processing resins.
3. It has also be noticed that the use of these compounds eliminate or reduce the need for screw pulls. And if they must be conducted, the time and effort taken to overhaul the machine is reduced to a very large extent.
Applications of Injection molding purging compounds in Extrusion processes
Purging compounds can be used in a range of extrusion projects such as the tubing, sheet, film, pipe, profile, compounding, and extrusion blow molding processes. They are most often used in profile extrusion and compounding since the turnover is a lot more often and the colours, resins and additives used are a lot more diverse.
You can as your purging compound supplier to show you their full range of compounds that are developed specific to purging requirements and also have the capacity to deal with the different kinds of resins that you may be using. A number of suppliers may also offer customized formulations which are designed especially for extrusion and are able to address mineral –filled grades and aggressive glass.
How to use Injection molding purging compounds for Extrusion
1. To optimize the use of purging compounds, it is important that it is fed slowly so as to make sure that all the flights are completely full.
2. After this, you can increase the speed of the screw to the maximum possible rpm that is considered to be safe to the point the purge begins to come out of the machine. The mechanical purge is at a benefit when the higher screw rpm leads to increased agitation and turbulence.
3. It is important to regularly put a stop to the screw and enable to purge to settle into any dead areas.
The benefits of injection molding purging compounds in extrusion processes are now known to engineers around the world. Its time saving and cost cutting capabilities offer members of the plastic industry a much needed competitive edge.
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John Steve is mechanical engineer with passion to improve machine performance. He is expert in plastic extrusion process especially for injection molding purging.
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