January 14, 2021

Making the move to rPET? Learn why mold cleanliness is key to injection molding success 

Dust mitigation and regular mold cleaning are vital for success when running rPET material. Learn how unique Husky technologies can help you overcome the challenges of introducing increased percentages of rPET into your production processes.


At some point every mold requires maintenance and cleaning. This is an inevitable part of running a mold, as PET dust particles can naturally accumulate. Keeping molds clean is even more important when running recycled PET (rPET), a very sustainable plastic. Using high amounts of rPET material can increase gas, powder and dust generation caused by residual contaminants, like AA blockers or O2 scavengers, that persist in the recycling process. And as demand exceeds supply, it is possible for the number of residual contaminants to increase and the quality of rPET to decline. So, with more consumers demanding sustainable packaging solutions made with higher percentages of rPET, mold cleanliness becomes even more important. The increasing speed of systems is also compounding the impact that maintenance and cleaning has on productivity, because as cycle times reduce, molds naturally create dust faster and require maintenance more often.

So how do you solve this challenge? While you may be familiar with various technologies that clean dust, Husky offers proven, innovative solutions that enable you to avoid this step completely by drastically minimizing dust creation.

These include our Ultra Hot Runner and patented Cold Half Technology, designed to enable you to eliminate dust and embrace moving to rPET with more confidence and less risk.

Invest in a solution that mitigates dust

To reduce the accumulation of PET dust, some manufacturers use vacuum technology. While vacuums may remove dust found inside Hot Runners, that doesn’t change the amount that builds up in the Cold Half. This side will eventually need a thorough cleaning, causing downtime and lost productivity. In addition, implementing an additional vacuuming step adds complexity and cost to an already complicated process.

For years, Husky Ultra Hot Runners have operated successfully by controlling and consistently delivering melt to each cavity. Ultra Hot Runners prevent plastic from leaking, helping to prevent the generation of PET dust and eliminating the need for extra vacuum technology. One secret is patented Husky Ultra Spring technology that uses a method called cold start protection. Ultra Spring technology works by keeping the nozzle and manifold sealed in a cold state before the Hot Runner reaches its operating temperature in order to reduce dust buildup in the stack.

Addressing the root cause of dust creation eliminates the need for additional mechanisms like vacuums, reducing maintenance downtime, minimizing risk of component failure and delivering a significant advantage over alternative technologies susceptible to dust buildup.

What if a mold could clean itself?

Until recently there have existed two common methods of neck ring vent cleaning—hand cleaning and dry ice blasting. While extremely effective, hand cleaning is a complex process that requires mold components to be individually removed, cleaned, rinsed, dried and replaced with the use of spray cleaners, solvents and brushes. Dry ice blasting is a nonabrasive method where the mold is cleaned directly in the press while still hot. Grain-sized carbon dioxide pellets are introduced into an air stream and are shot through nozzles at high speed to quickly remove residue.

The challenge with each of these methods is the amount of labor and downtime. Any manual cleaning method requires skilled maintenance personnel and must be thorough to avoid processing defects. Manual cleaning can be time-consuming, repeated motions can result in operator injuries, and mold parts and inserts can be damaged during the cleaning process.

Running rPET amplifies manual cleaning challenges while creating a greater need to clean molds more often. Moreover, running different qualities of recycled PET can cause greater risk of outgassing and dust deposit creation in vents, which can lead to a higher likelihood of defective parts. Having a reliable, fast and easy method of mold cleaning maximizes the success of running rPET material. Husky Self-cleaning technology is the ideal solution because it skips traditional maintenance interruptions of 2–6 hours and replaces them with an automatic process that lasts a single extended machine cycle.

Unlike manual cleaning methods, the Self-cleaning process is simplified to the touch of a button. Because Self-cleaning is an automated process, it eliminates the need for operators to enter the machine and can be performed as often as needed. With virtually no production time penalty, Self-cleaning helps to overcome the contradiction between cycle time and mold maintenance, especially beneficial for rPET since this sustainable plastic can require more frequent cleaning.

The secret to Self-cleaning technology is controlled flash, which is the intentional flash of the tool into vents where dust collects, using precisely controlled gaps to ensure flash does not travel beyond the target area. During a Self-cleaning cycle, the vents are filled by the overflow of PET from the preform. The overflow of PET, called PET flash, then sticks to dust in the vents, and the flashed preforms, complete with dust, are then ejected, leaving cleaned vents behind.

Effective combination

While Ultra Hot Runners and Self-cleaning technology do not completely eliminate the need for traditional mold cleaning methods, they represent a significant evolution in mold maintenance that offers added flexibility and reduced risk when running recycled PET—especially when used together. This combination addresses many of the common issues associated with mold maintenance, including minimizing labor and downtime, streamlining the injection molding process and making the cleaning process safer. It also enables you to be more sustainable by supporting higher percentages of rPET to be run more efficiently while maximizing part quality and minimizing risk.


Would you like to add rPET to your molding operation? Get in touch to learn more about Husky mold maintenance solutions.


Discover how much downtime you could avoid with Self-cleaning molds and Ultra Hot Runners