By Emma Dylan
A breakdown of the basic principles, methods, and practices involved in plastic prototype fabrication for both beginners and experts.
CNC machining and rapid prototyping are methods that when combined, yield more precise, accurate end results. Plastic prototyping simply involves applying the principles of rapid prototyping onto plastics.
Generally, most businesses that have experience in the field of plastic products of any kind refrain from skipping the prototyping process. This is because despite the time and money savings that stand to be gained from going straight to final design, there is usually an exponentially higher price to pay on the long run – in the form of customer dissatisfaction and product failures.
As a rule of thumb, plastic prototyping can employ three main methods: 3D printing, CNC machining, and injection molding. In the following paragraphs, we are going to take a look at all the instances, understand their underlying merits and demerits, and the situations in which they are best used.
3D printing is an additive manufacturing method that by itself, is an umbrella term for a handful of underlying manufacturing technologies. With this in mind, the most commonly used 3d printing methods for plastic prototyping are Selective laser Sintering, Fused Deposition Modeling, and Stereolithography.
Fused Deposition Modeling (FDM) is the most popular form of 3D printing for plastic prototype jobs. These machines can come in industrial-grade configurations, allowing manufacturers to churn out high quality, high resolution results.
With regards to materials, PLA (or Polylactic Acid) is an affordable material that can be used to create prototypes with little or no functional use as products. On the more functional side of things, Nylon, PETG (used in bottles and other containers), and Polycarbonate are strong choices. Polycarbonate especially is coveted for its ability to withstand the elements and as such, is used in the manufacture of consumer electronics like gaming and PC accessories, smartphones, TV’s, etc.
When it comes to plastic prototyping use cases, 3D printing is popularly applied in small volume situations with short timelines for work turnover. Simply put, when you want to fabricate a small amount of prototypes in a short time, 3D printing is a sure bet. This is because the additive trait of 3D manufacturing allows designers and engineers to tweak the prototype at any point in production, allowing for flexibility in testing and manufacturing.
CNC machining or milling is another plastic prototyping option. It provides a viable option for manufacturing functional prototypes. A subtractive method, it varies in principle and practice from 3D manufacturing, allowing engineers to cut out a prototype from a solid, unformed piece of plastic and compared to it, CNC allows the engineers the flexibility to fabricate things like threads, undercuts, and an increased number of surface finishes.
With regards to use cases, CNC offers a few advantages over 3D printing and injection molding technologies. CNC machined plastic offers noticeably improved structural integrity, which is especially crucial when manufacturing functional plastic parts. Also, it possesses improved mechanical quality and allows for use a greater variety of thermoplastic materials within its purview.
Finally, we move on to injection molding. This, as mentioned earlier, is the most commonly used method of plastic prototyping. Injection molding allows for the mass production of plastic parts and finished goods and although this is its most common use case, it can also serve as an expedient medium for producing plastic prototypes. This allows it to stand as a viable option for full-scale industrial production in industries like home appliances, consumer electronics and devices, aerospace industries, and automotive parts manufacturing.
With injection molding, a metal die is first created, and then plastic resin is heated in a barrel, mixed, and forcefully injected into the metal die. When this process is finished, the plastic is rapidly cooled and thus forms a solid, finished part. This results in a finished product that possesses qualities such as a higher quality surface finish compared to other plastic prototyping processes.
With injection molding, a lot of the same plastic materials that are used with 3D printing and CNC milling can also be used. Some of them include Polycarbonate, Nylon, ABS, and Polyethene.
Nylon, for example, produces plastic prototypes that have high material stability and resistance to the elements as well as chemical action and material abrasion. Polyethene allows for high tensile strength, impact resistance and low moisture absorption.
In conclusion, getting better at plastic prototyping, just like any other craft, requires an understanding of the little nuances as much as the larger, more obvious principles. The industry is cut-throat, with clients usually possessing a precise idea of the vision they have for their product. It falls on you, the professional, to bring those visions to life. Try experimenting with different methods to boost your knowledge of their various merits as well as their drawbacks. Specializing in one thing is good, but having an all-encompassing knowledge of any field is always admirable.
