Ice-blast cleaning of molds

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Molds cleaned by Cold Jet technology--before and after.
Silgan is the largest supplier of metal containers for food products in North America and a leading supplier of plastic containers for personal care products.

In addition, the company is a leading worldwide supplier of metal, composite, and plastic vacuum closures for food and beverage products. With more than 22 production plants, Silgan Plastics is one of the top 10 blow molders in North America, providing stock and custom packaging for many of the top consumer goods manufacturers.

Silgan Plastic’s Toronto-based manufacturing plant is home to three types of molding systems: injection molding, injection blow molding, and injection stretch/blow molding. The plant produces a variety of plastic containers, lids, and caps, many using PET preform molds with 72 individual cavities. Because Silgan runs a lot of PET and Pharmaceutical products, the company has developed a preventive maintenance routine that meets customers’ product quality needs.

At the center of the routine is a software program that generates a work order based upon cycles for each mold. The cleaning cycles are set-up with each customer to ensure that their molds are well maintained and in good working condition. This effort has become a standard for all Silgan molds and customers’ molds. With the 72-cavity molds, products are made in 10 second cycles. After every 15,000 cycles, the maintenance crew used to clean the hot molds by hand in the presses using chemical and citrus cleaners, degreasers, wire brushes, drills and pipe cleaners. Given the large number of cavities, each mold would take two to three hours to clean by hand. After every 60,000 cycles, the molds were removed from the presses and given a more thorough cleaning. Despite the amount of time spent maintaining the molds, it was difficult to get them completely clean.

“When you clean a 72-cavity mold by hand, not only is it time consuming, it is difficult to get behind every slide and neck ring,” says Joe Pond, Setup Supervisor for Silgan Plastics. “In addition, the coatings and plastics that we use tend to get on other parts of the equipment, which also adds to the challenge.”

After attending a Husky Injection Molding Systems seminar, Pond asked Husky representatives what was the best method for cleaning high-cavitation molds. Husky recommended dry ice blast cleaning systems from Cold Jet.

Dry ice blasting uses non-abrasive media in the form of recycled CO2pellets that won’t damage surfaces or equipment. The dry ice pellets are propelled at high velocities to blast contaminants from the mold surface. The combination of dry ice blast cleaning’s kinetic energy and thermal effects breaks the connection between the dirt and the surface, lifting away contaminants. Other manufacturers have found that by using Cold Jet’s system they can decrease cleaning time by 50 to 75%, and because the dry ice evaporates on contact, there is no run-off, rinsing, or drying required. Cold Jet systems do not damage or change the dimensions of the mold surface, thereby ensuring consistent part quality. Dry ice blasting is also safe and non-toxic, does not create downstream contamination, and reduces or eliminates employee exposure to dangerous chemical cleaning agents.

Following Husky’s recommendation and a Cold Jet demonstration, Silgan acquired two dry ice blasting cleaning systems, one that is located on the plant floor and the other used in the company’s maintenance room. Since integrating the systems into its cleaning cycles, Silgan has been able to reduce its maintenance room staff to a single person and has trained all its machine operators how to use Cold Jet’s cleaning systems. Cleaning time for a single mold went from two to three hours to less than 45 minutes, and the company is now finding multiple ways to use dry ice blasting in other areas of the plant. For example, Pond recalls the time when a PET dryer overheated and the resin melted in the dryer. Normally, workers would have to wait for the dryer and the resin to cool down and then remove the resin by chipping it out, a 12-24 hour process.Using dry ice blasting, Silgan was able to remove the resin and restore the dryer in less than two hours.

“In addition to the molds and the PET dryer, we have also eliminated nearly three days of downtime by using Cold Jet’s system to clean the injection screws on our presses, a process that usually required us to send the screws offsite,” adds Pond. “The time savings alone have been phenomenal as we have been able to clean our equipment better and faster while they are still online. We no longer have to worry about working dangerously close with hot equipment, our on-site environment and safety managers are happy, and we have dramatically reduced the amount of cleansers, degreasers, and alcohol that we buy and use for cleaning.”

Silgan Plastics still cleans on a cycle basis, but cleaning is now faster and easier. Every 15,000 cycles, machine operators use the Cold Jet system to clean and prepare the molds for the next 15,000 cycles. When a more thorough cleaning is required at 60,000 cycles, the maintenance person first blasts the molds with dry ice, which removes the majority of the residues. The molds are then removed from the presses so that workers can clean the rest of the equipment, oftentimes using only dry ice blasting.

“Everyone is impressed with the speed and effectiveness of Cold Jet’s systems,” says Pond. “They have easily paid for themselves more than two or three times over. It is because of Cold Jet’s systems that we are able to meet our high cleaning standards and our customers’ mold maintenance cycles.”

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