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Performance Tips

The Dyna-Purge family of products have been designed to meet your demanding conditions. However, there may be instances where process alterations can enhance the results. The following is a collection of comments we have received from devoted customers over the years that we feel offer processors potential benefits:

1. Increasing Back Pressure can improve purge results by adding force and agitation to the purge process. This is true of Dyna-Purge, because it is a mechanical purge, needing no chemical component to do its job. Be sure to use enough material to fill the barrel, so Dyna-Purge can scrub and push through contamination, including carbon build-up caused by degradation, which leads to black specks. Increasing the back pressure between 50% and 100% will usually improve the purging experience. As with any purging application, extra caution should be taken not to exceed any of the manufacturer's operating requirements.
2. Increasing the Screw Speed by raising the RPMs will help Dyna-Purge flow downstream faster. This increases the level of agitation and allows for the Dyna-Purge to plasticize sooner. The combination of producing more thermal heat and agitation may enhance the purging process.
   1. Always work within resident resin temperature profile to minimize possible degradation of the resin.
   2. Start purging at low speed. When the purge material starts coming out of the head, increase screw speed to the maximum safe level.
3. Reducing the Screw Speed will allow the unique properties of Dyna-Purge to maintain their rigidity longer and travel further downstream before completely softening. This procedure will allow for extra scrubbing, when contamination is downstream at the end of the barrel and screw.
4. Shutting off the machine between changeovers can allow for additional contamination to be removed from the barrel and screw. Leave one half to a full barrel of Dyna-Purge in the machine, then turn the machine off and let it cool down. Once ambient temperature is reached, turn the machine on and raise the temperature for the next production run. When the temperature reaches the lowest level for Dyna-Purge, begin to rotate the screw slowly, being careful not to over-torque the machine. Introduce another scoop of Dyna-Purge to push out the remaining purge and then immediately use your next production resin. This purging procedure allows for the Dyna-Purge to bond with any residual contamination on the barrel and screw, so that, as temperatures are brought up, Dyna-Purge will pull it off the surface and remove it from the machine.
5. If experiencing contamination in the accumulator, raising the temperature approximately 50°F(28°C) and then soaking may enhance the performance of Dyna-Purge. Fill the accumulator with Dyna-Purge. Purge a small amount of Dyna-Purge through the die, then soak for 30 minutes. If the accumulator has internal agitation, turn on periodically while soaking. When there are more than 2 heads, raise the temperature of the outboard heads 50°F(28°C) higher than the rest of the system. This will compensate for the longer flow path. Empty the accumulator, adjust temperature settings for your next resin and flush out Dyna-Purge.
6. If experiencing problems purging out highly pigmented colors, such as blue or red, raising the temperature might help. Raise the temperature approximately 50°F(28°C) above the normal operating temperature, up to 500°F(260°C). Always work within resident resin temperature profile to minimize possible degradation of the resin. Soaking at either the standard temperature or at higher temperature may also help. In this case, begin purging until only Dyna-Purge is exiting the nozzle, then allow to soak for 5 to 10 minutes before continuing to purge until clean.
7. If experiencing contamination at the check ring, running several short, high velocity shots will help to dislodge and remove the contamination.
8. When purging hot runners, below are two procedures we recommend for different needs:
   
   1. 2-step purge process for thorough cleaning when signs of degradation are present –
      1) retract the nozzle from the mold base and purge the screw and barrel first, then 2) reattach the nozzle to purge the manifold. Selectively closing the gates and purging one hot runner at a time will increase pressure and improve purging through the manifold.
   2. 1-step purge process for simple color or resin changes –
      1) with the nozzle still attached to the mold base, purge directly through the hot runners, keeping the mold in the open position. This will save retraction time and expedite the purging process.
9. Clumping or "balling-up" in the feed throat can be avoided by keeping the feed throat cool. The temperature of the feed throat coolant should be maintained between 80-120°F(27-49°C). It is best to control the feed throat temperature as close to 100°F(38°C) as possible. In humid weather, the temperature should be just warmer than the dew point to avoid condensation.
10. For Extrusion applications:
    1. Vent holes – Cleaning a vent hole can be accomplished by introducing small amounts of Dyna-Purge through the vent hole during the normal purging process. Purging with the vent capped can also help to clean the vent hole. In this case, care should be taken not to allow pressure to build up beyond specifications.
    2. Dies – Raising the temperature of the die about 30-50°F(17-28°C), while remaining within the service temperature range of the resident resin, may help remove material deposits more quickly.
    3. Gear Pumps – Operating at low delta P (low difference in pressure) will improve purging.To get the optimal cleaning effect in the extruder (and some in the viscoseal of the pump), it helps to vary the inlet pressure.

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