Cryogenics in Plastic Manufacturing
- November 29, 2020
- Controlled Thermal Processing
- Cryogenic Processing
What do you do if you want to get a custom part or product made from plastic? The part or product that you want to get made could be large or small, it may be stiff or flexible. It could also be in any number of shapes, including an unconventional shape. So how can something like that can be made possible?
For decades this has been achieved using plastic molds. The process involves shaping liquid or another pliable material through the use of a rigid frame called a mold. Once the pliable material is inserted in the mold, it takes on its shape and the part or product is created.
The process does involve having to carefully cool the hot plastic material. This is done gradually so that it properly takes on the shape of the mold. Uneven cooling or low injection pressure in the case of injection molding can result in defects in the final product.
The quality of the molds also plays a major role in the fit and finish of the molded part.
How do you manufacture plastic molds?
There are a number of ways through which plastic molds are made. The process goes as far back as the late 1800’s when there was a need for plastic billiard balls to replace the ivory billiard balls that were commonly used at that time.
John Wesley Hyatt invented a method to manufacture billiard balls by injecting celluloid into a mold in 1868.
After four years, Hyatt and his brother invented and patented a machine that automated the entire process. This then became the first plastic injection molding machine. It’s method was fairly simple in that it used a plunger to inject plastic into a mold through a heated cylinder.
Modern methods of creating plastic molds are more efficient and are also capable of creating more precise molds. Rotational molding got its start in the early 1950’s when it was used for manufacturing doll heads.
A decade later, the process was further improved to allow for the creation of large hollow containers with low-density polyethylene.
Cryogenics and plastic manufacturing — how does it work?
A number of issues can be encountered during the plastic molding process. Warping is a common defect that’s witnessed when plastic molds are created. It’s the deformation that takes place in injection molded products when different parts shrink unevenly.
This happens during the cooling process and the uneven shrinkage puts undue stress on different areas of the molded part. The stress then results in the bending or twisting of the finished part as it cools. This can be avoided by gradually bringing down the temperature as is done in cryogenic processing.
It’s also not uncommon for vacuum voids or air pockets to appear in a finished molded product. Large or numerous voids can actually threaten the integrity of the part or product because there’s air below the surface where there should be molded material instead.
These voids are largely caused by inadequate molding pressure and often because the material closest to the mold wall cools too quickly. This causes the material to harden and that pulls it towards the outside.
Deep cryogenic treatment is a proven method for reducing issues that may occur during the molding process. Since the mold isn’t exposed to uneven cooling, there’s a much lower chance of warping. It also helps create a more durable product that has a significantly longer lifespan than its untreated counterpart.
Methods of cryogenic plastic manufacturing
There are several different methods of cryogenic plastic manufacturing. The six most commonly used methods are the following:
- Rotational
Rotational molding is used to create large hollow parts. It’s done by placing a powder or liquid resin into a metal mold and then rotating it in an oven until the resin has coated the inside of the mold.The mold’s constant rotation creates the centrifugal force that’s required to create even-walled products. After the mold has cooled, the hardened plastic product is removed.
- Injection
Injection molding is used to create highly precise molded parts. The process involves injecting molten plastic material into a metal mold at a very high pressure. This is done so that the plastic material can accurately take on the shape of the mold.
Much like the other methods of molding, once the material has been injected at a high pressure, the mold is then allowed to cool down before the finished product is removed from the inside. Injection molding is also useful for creating high volume custom plastic parts.
- Extrusion
Extrusion molding is similar to injection molding with one major difference being that it’s used to produce a long, continuous shape. The other major difference is that extrusion molding doesn’t use a mold, rather, it uses a die.The parts are made by squeezing hot plastic material through a custom die. It’s the shape of the die that then determines the shape of the final product.
- Blow
If hollow, thin-walled plastic parts need to be made, then the blow molding process is the perfect fit. The process is quite similar to that of glass blowing. The machines will heat up the plastic and then inject air to blow up the hot plastic like a balloon.The plastic is blown into a mold while it’s expanding so that it presses against the walls and takes on the shape of the mold. Once filled, it’s let to cool and harden before being ejected from the mold.
- Compression
Compression molding involves placing the heated plastic material inside a heated mold and then pressing it into the desired shape. Once the shape has been achieved after compression, the heating process is carried out to ensure maximum strength for the finished product.It’s then cooled, trimmed and removed from the mold. Compression molding is largely used for the replacement of metal parts with plastic parts.
- Thermoforming
Thermoforming requires that a plastic sheet called thermoplastic is first heated so that it becomes pliable and is then formed into the desired shape using a mold. The final product is then trimmed to achieve the desired result.
This process is commonly used to create disposable plastic products like lids, containers, cups, trays, and more. Thick-gauge thermoforming is also used for creating a variety of parts including but not limited to refrigerator liners, dash panels for cars, and utility vehicle beds.
How cryogenic processing works over other methods of plastics manufacturing
Cryogenic processing can be very useful in the plastic molding process. The industry itself is highly competitive and operates on whisker thin margins. This means that any downtime or delays are best avoided but that’s inevitable since it’s common to run into problems with seized pins, eroded gates or cavities.
Deep cryogenic processing can significantly reduce those risks. When plastic molds go through the process, whether they’re steel molds or made from any other metallic material, they are at a far lesser risk of runner and cavity wear.
Extrusion screws and dies also respond very well to the treatment. Ejector pins that are cryogenically treated are also more stable in size and shape which helps fix problems where the pins stick or gall.
Industries that use cryogenic plastic manufacturing
Cryogenic plastic manufacturing is used in a large number of industries. Plastic product manufacturers rely on the process to improve the quality of their products and also to streamline their production processes.
It’s widely used in the home appliances industry as well for products like refrigerator liners.
In the automotive industry, car manufacturers utilize cryogenic plastic manufacturing to create panels for car doors that reduce the amount of road noise that makes its way into the cabin.
This process has proven to deliver tangible results for all plastic manufacturing industries which is why we now see a much greater adoption of cryogenics in plastic manufacturing.
How to improve your plastic molding
Thinking about improving your plastic molding? Whether you’re just starting out in the molding business or would like to see the performance and durability of your molds increase, there’s a lot you can do right now to ensure that your business achieves greater efficiency.
At Controller Thermal Processing Cryogenics, we’re the leaders in the deep cryogenic treatment of plastic molds. We are the leading industry expert on treating metal and steel parts that are used in the plastic molding industry.
Our clients have seen massive gains in their efficiency and creation processes. Typically, the customers have seen two to three times the life on their pins, molds, and other parts.
CTP Cryogenics has four decades of experience in the cryogenics industry. We provide our services to customers from coast to coast through our three different locations across the United States. We are committed to using the most advanced research and technology in cryogenics.
The results of our cryogenic processes have been verified by researchers affiliated with the US Army, Los Alamos National Laboratory, NASA, and the Illinois Institute of Technology.
Contact us today for a free quote if you’d like to utilize cryogenic processing for your plastic molding business.
