Thermoplastic extruders are the workhorses of the plastics industry. In many plants they are set up and running continuously for days and weeks on end. Then there are other applications, where changeovers are more frequent, they can be exposed to a variety of different materials. Some of which can be abrasive or even eventually corrosive. All the above can lead to your extruder getting worn out!
With extruder wear comes product inconsistency, and overall inefficient operation. If left unchecked ultimately leads to a machine breakdown. Some signs of wear can include inconsistent melt temperature, with a roaming need for adjustment. Typical is increasingly higher set points needed on the barrel heaters. Wear can produce metal particles found as evidence in the screen packs. If no screens are in place, they will show up in extrudate but can be very difficult to detect. Another machine variable to pay close attention to and monitor is the Amps, as wear can create an excessively high motor load on the extruders drive. The most obvious sign, if you are hearing loud grinding or scraping noises, it is a good bet your extruder is just about worn out. Let’s do something about it!
The best approach to a long-term wear condition is to avoid it in the first place. This can be done by breaking into production at scheduled preventative maintenance intervals. Where pushing the screw out allows for measurement and inspection. A great time saver in this process is to use Asaclean EX grade. The effort to remove the screw will be greatly reduced, and the cleanup will be minutes versus what can take hours. Consult the OEM of the extruder, or the screw and barrel supplier for measurement specifications and acceptable wear tolerances. Once identified as worn out, replace before resuming production. You’ll be glad you did.
If running production long term or on repeated basis with filled abrasive materials, you may find that extruder wear is taking place faster than it should in comparison to others. Depending on the circumstance this may be part of doing business. On the other hand, if you want to avoid it or prolong the life of the extruder components, look to specialized metals and or coatings, especially at critical areas being exposed to wear.
The upfront cost for these upgrades, may seem prohibitive at first, but consider it may prevent a larger unplanned downtime or poor-quality cost down the road.
There are also production materials than can create a corrosive environment, which can also lead to wear within the extruder. Corrosion will pit and begin break down inadequate metal surfaces and weaken the metal overall. Like abrasion, a way to prevent this is to employ the use of specialized metals or install protective coatings. The situation can also be avoided. If these materials are not inadvertently allowed to degrade and break down.
As an example, PVC can cause problems in a short hurry if left idle in the barrel for any length of extended time at process temperatures. For this instance, consider the practice of using Asaclean Purging Compounds to remove this or any material in advance of allowing degradation to take place. Further, if the machine needs to be left shut down for any length of time, the unfilled grades of Asaclean can be used to seal the machine, to limit and prevent the possibility of corrosion.
If you would like additional information and some useful tips on maintaining machinery and best practice purging methods, please contact your Asaclean Technical Sales Representative.
Learn about the importance of implementing proper purging procedures by downloading this free industry guide.