Silgan Plastics devoted countless hours to maintaining product molds by hand, but the company was still unhappy with the quality of its cleaning methods.

Silgan Plastics is the largest supplier of metal containers for food products in North America and is a leading supplier of plastic containers for personal care products. With more than 22 production plants, Silgan is one of the top 10 blow molders in North America, providing stock and custom packaging for many of the top consumer goods manufacturers.

The company’s Toronto-based manufacturing plant is home to three types of molding systems:

• Injection molding

• Injection blow molding

• 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 software that produces 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.

With the 72-cavity molds, products are made in 10 second cycles. After every 15,000 cycles, the maintenance crew cleaned 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 between 2-3 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. The coatings and plastics that we use tend to get on other parts of the equipment, which also adds to the challenge.”

- Joe Pond, Silgan Plastics Setup Supervisor

Silgan implemented dry ice blasting

Silgan discovered dry ice blasting as a solution to the company's unique needs. The plant acquired two dry ice blasting machines, one for the plant floor and one for the company's maintenance room.

Dry ice blasting uses non-abrasive media in the form of recycled CO₂ pellets that won’t damage surfaces or equipment. 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 dry ice cleaning they can decrease cleaning time by 50 to 75%, and because the dry ice sublimates on contact, there is no run-off, rinsing or drying required.

Learn more about how dry ice blasting works

Dry ice blasting improved efficiency

Silgan has been able to reduce its maintenance room staff to a single person and has trained all its machine operators how to use the dry ice blasting machines.

Cleaning time for a single mold went from two to three hours to less than 45 minutes.

Silgan uses an anti-static spray on the bottles as they move along the conveyor system to prevent them from sticking together. The spray accumulates on the conveyor rollers, slowing down production. Normally to clean the anti-static spray machine, workers would have to disassemble the system, clean the components by hand with food-grade cleaners and then reassemble the machine in a process that took at least a day.

With dry ice blasting, machine operators can now clean the entire machine in an hour without taking the equipment apart and risking damage to the components.

Learn about dry ice blasting for plastics

Silgan also recalled an experience 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. This was a 12 to 24 hour process. 

Using dry ice blasting, Silgan was able to remove the resin and restore the dryer in less than two hours.

Silgan also noted that they have also "eliminated nearly three days of downtime" by using dry ice blasting to clean press injection screws at the facility rather than offsite.

“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.”

- Joe Pond, Silgan Plastics Setup Supervisor

Silgan Plastics still cleans on a cycle basis, but cleaning is now faster and easier. Every 15,000 cycles, machine operators use dry ice blasting systems 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 blasts the molds with dry ice, clearing away most of the residue before the molds are removed and cleaned more thoroughly with dry ice blasting.

Pond is completely satisfied with Silgan's investment in their dry ice blasting machine.

"They have easily paid for themselves more than two or three times over It is because of [dry ice blasting] that we are able to meet our high cleaning standards and our customers’ mold maintenance cycles.”