Purging compound reduce machine downtime & increases productivity. Effective cleaning of plastic processing equipment is vital for keeping the machinery running productively and free from trouble.
There are several occasions that call for purging & cleaning processing equipment, including colour changes, resin changes, formulation changes & routine shutdown and maintenance. Ensuring that the machinery is cleaned thoroughly and effectively is critical for quality control and in extending the operating life of the machinery. Although breaking down a large extruder and painstakingly cleaning it by hand is thorough and effective, increasing pressures in the market place can make this method a strain on productivity. For example, just-in-time delivery demands result in greater frequency of resin and colour changes. In addition, there is always the need to manage bottom-line costs to stay competitive and profitable. Machine downtime is neither competitive nor profitable to the processors.
The use of commercial purging compounds is helping processors to meet today`s pressures by minimizing machine downtime and boosting productivity. A purging compound is introduced to the system to expunge a colour, resin or formulation before a change over or shutdown. Purging compounds are particularly helpful in preventing streaking, caused by bits of previously run colour becoming trapped in a negative flow area. Since there is not enough physical turbulence in the area to remove colour, the nest material processed picks up the trace amounts of the colour and causes a streak in the new product. The streaking will continue until the trapped colours is flushed away by the next resin.
If the streaking occurs in the same lo9cation, then the entrapment is probably closed to the die. If streaking is random, then the colour is likely trapped in the barrel or feed nozzle of the machine. Inconsistent material due to colour is considered scrap and represents wasted material and non-productive time. Purging compound are designed to remove all traces of the previous colour or resin, allowing the processor to resume full production sooner and with little, if any, scrap.
Processor using purging products may still break down a machine for manual cleaning however, pre-cleaning with the purging compound saves a significant amount of time, frequently 50% or more. This bolsters the company`s capability to meet their requirements of its customers.
In addition to cleaning of the previous colour, resin, or formulation, purging compounds are also effective in removing black specs (carbon buildup). These can be caused by any number of reasons such as hot temperature spots in the machine, degrading of polymers, separation of additives, fillers and colour concentrates from the carrier, dead spots or negative flow area in the barrel, mixing area or die, regular start up & shut down, or a lack of regular preventative maintenance. Like shale rock, the carbon buildup will break into pieces and be moved forward by the screw, only to be displayed as unwanted black spec in the finished palatalized product.
Purging compounds – the scrubbing granules used in their formulation safely penetrates into the dead spots and hot spots in the machine to break away and remove the carbon build up, including layers of separated additives and degraded polymers. This mechanical, non abrasive action will not damage the surface of the screw, barrel, or any metal components or tolerance of the plastic processing equipment.
Although there are various hybrid sold, commercial purging compounds are available in three primary types.
- Chemical
- Mechanical / Abrasive
- Mechanical / non abrasive
Usage of purging compound may it be simple LDPE or complex Nylon material, following benefits can be obtained:
- Machinery can be cleaned in very short time.
- Saving of costly raw material
- Minimum rejection of the final product
- Material can be grounded and used upto 2 or 3 times.
