Written by Applications Engineer Craig Crossley
Recycled materials, up until recently, have been regarded as inferior, unusable and not worth the time. However, recent developments in regulations and technology have pushed recycling to the forefront of the plastics industry, with some very large players pledging to use recycled materials in all of their products.
But how do you develop products with high recycling content?
This is a key question that is going to rapidly make its way through engineering and product development teams over the next few years. While 3D printing direct prototypes is an excellent way to go through your first iteration of a product, there is no substitute for using the same material and process as your end product. Whether it is blow molding, thermoforming or injection molding, materials with high recycled content are going to behave differently and the only way to true verify your design is to prototype in the exact material, in the exact process. But before we dive into how to prototype your product with recycled plastic, let’s explore recycled materials.
Recycled materials come in three major form factors today: Post Consumer regrind, scrap regrind and bottle to bottle recycling.
- Post Consumer regrind (PCR) is largely made up of LDPE and HDPE and some other variations of the polyethylene family. Polypropylene and polystyrene both can be recycled well, however, the infrastructure around getting PCR for these materials is lacking.
- Scrap regrind comes on the manufacturing floor when products have a certain amount of allowable regrind, which generally comes from scrap parts, runners, and sprues. Lots of different plastics can be remelted and therefore “recycled”, dashing the myth that everything we use has to go directly to a landfill, however, the drawback is the loss in performance. When thermoplastics are remelted they lose molecular weight and exhibit a drop in mechanical performance plus the threat of contamination in the melt.
- Bottle to Bottle recycling is one of the more interesting ways to increase the use of recycled materials in product development. There are several different technologies that are able to take PET bottles: grind, melt, pelletize and churn out clean pellets, which are FDA approved, to make bottles again.
With plastic waste on the rise, the need to reuse is going to drive the plastics industry’s new product development. The answer to that question above is simple, you need to prototype your product in the same process and material as your end product. Unfortunately the answer to that question brings up another, How? Aluminum tools take months and thousands of dollars with design constraints that make it impossible to implement early enough in the development cycle. That is an issue when using regular materials, and recycled plastic exacerbates this problem by its varied processing and mechanical properties, leading to a lot more testing early on in the process to verify designs.
Fortify 3D printed mold tool
A solution to costly and slow procurement of aluminum tools is Fortify Digital Tooling (DT).
DT is a ceramic fiber reinforced photopolymer with an extremely high HDT, strength, and rigidity which translates to tooling such as injection molding, thermoforming, and blow molding. At lower costs and much higher speeds DT is an alternative to aluminum tooling which allows engineers to develop products in days instead of months. Using polymer based mold inserts allows engineers and designers to test these recycled materials in their end use manufacturing process. Not only will this speed up the development cycle, but there is the opportunity to iterate in a cost effective manner if the recycled material of choice does not function as designed. DT is a cheaper option than cutting metal prototype tooling and yet does not sacrifice the end use material of the prototype, like direct 3D printing would.
Parts in a variety of industries are good candidates for this process including aerospace, food packaging, medical devices, and even common consumer goods like toys. One of the largest spaces that will be required to use recycled materials and undergo a lot of design iterations in the near future is the caps and closures industry. With Europe implementing restrictions on single use plastic, tethered caps and closures have become a hot option for beverage manufacturers looking to make sure bottles and caps can remain intact and the same material to improve recyclability. The only way to prototype these types of caps with living hinges and complex tethering features is injection molding. Anyone familiar with prototype injection molding is aware of the high cost and lead times of getting traditional metal tooling- 4-10 weeks and anywhere from $5000-$15000. With a Fortify printer in house a design department can cut this lead time down to 3 days and only $300-$600 for a set of inserts. Not only is this a much cheaper alternative to metal tooling, the prototypes manufactured off of these tools are functional, unlike a 3D printed cap, which would not be able to be flexed and used like a molded part. Another advantage for those who are especially environmentally conscious is that your sprues, runners, start up, and scrap parts could easily become your next iteration of prototypes with just a grinder and dryer. When considering manufacturing with recycled materials, molding is really the only option, and for prototyping resin based tooling is the most cost effective and shortest lead time solution.
Processing recycled materials can be a difficult task even for very experienced process engineers and highly sophisticated presses. One technology that is flipping this on its head is the iMFLUX Auto Viscosity Adjust (AVA) which uses proprietary technology to change the injection conditions during each shot to adjust to the changing viscosity of the material. This can come in handy during normal production as molecular weight over the course of material batches can change slightly and alter the viscosity of each shot, however this variability is significantly greater when using regrind or PCR. Implementing iMFLUX into your presses would allow for the use of recycled plastic without the need for a process engineer to diligently watch every shot and try to adjust settings on the fly which in turn is going to reduce scrap rate and produce high quality prototypes and parts.
HDPE Regrind Material (Source: erema.com)
While AVA is a great tool for combating variations in PCR and regrind, getting high quality recycled resin is of the utmost importance in order to effectively implement sustainability into your manufacturing process. One option for large manufacturers would be to bring high quality recycling equipment into the facility and control the process. Simple single screw extruders are fine for shop regrind as it is less likely that there will be a high degree of contaminants, but for optimal results a larger investment in specialized equipment would be required. Recycling leader, Erema Group, has several different technologies that can address a host of different form factors for recycling including bottle to bottle, thin film, regrind, and general PCR. The advantage of using recycling equipment is that it can filter out contaminants while remelting and pelletizing the polymer which creates a much easier to use material, rather than trying to process with chunky regrind, you are able to load in pellets, much like you would do with a virgin resin. However, bringing in recycling equipment is a significant investment into technology, so for smaller manufacturers here are some suppliers of high quality recycled materials so you can begin prototyping greener:
If you are looking to test out Fortify’s Digital Tooling material for recycled plastics in your prototyping, sign up for our molding pilot program.