Molded plastic medical parts have tight tolerances, require a high degree of cleanliness, and are made from a range of materials, including specialty polymers and elastomers that cost more than commodity rubber and plastic. Whether parts manufacturing involves injection, compression, or transfer molding, designers need to know that the components they receive are free from defects that could jeopardize quality or compliance. This includes samples for first article inspection (FAI) and high-volume production runs.
Flash, a type of molding defect, affects the surface finish of parts and can interfere with seating, sealing, and assembly. Typically, flash occurs when rubber or plastic escapes the mold cavity at the parting line, the point where the two halves of the tool meet. It’s possible to reduce flash through better part design and higher-quality tooling, but some amount of flash is usually expected. With tight-tolerance medical parts, however, defects that affect geometric dimensioning and tolerancing (GD&T) are unacceptable.
Cryogenic Deflashing for Molded Medical Parts
Nitrofeeze® cryogenic deflashing removes flash without changing part tolerances or surface finish. In other words, only the defects – the flashing – are removed. The process works by cooling plastic medical parts below their glass transition temperature (Tg) and then blasting them with a specified cryogenic-grade polycarbonate media. When flash becomes hard and brittle, it’s easy to remove. Plus, cryogenic deflashing works with a wide range of medical rubber and plastic, including silicone, PEEK, and Ultem.
In addition, cryogenic deflashing supports batch processing and leaves little to no dust or residues behind. Whether a molder needs to deflash 10 parts for an FAI or 10,000 parts for a production run, the process consistently delivers the same high-quality results. Since cryogenic deflashing is automated and computer-controlled, it’s also easy to save and reuse a deflashing recipe. Dry ice blasting, an effectively media-less process, can be used in conjunction with cryogenic deflashing if cleanliness is still a concern.
Cryogenic Deflashing vs. Other Flash Removal Methods
Nitrofreeze® cryogenic plastic deflashing represents a significant advance over manual deflashing, the traditional way to remove flash from molded medical parts. The cost of hand tools like knives and scissors is low, but the labor costs are high – especially for parts with hard-to-reach geometries. Manual deflashing also introduces part-to-part variations and the risk of removing too much material, an expensive problem with polymers like PEEK. With cryogenic deflashing, however, intricate part geometries are easy to access.
Die punching can provide more consistent quality than manual trimming, but it’s still labor-intensive and results in lower production outputs. Plus, the type of tooling that’s used isn’t designed for internal part features. Vibratory tumbling, a semi-automated process for flash removal, can increase throughputs but it can’t compare to cryogenic deflashing. Because the plastic media in vibratory tumbling is combined with abrasives, dust that requires part cleaning is left behind.
Wet tumbling, a version of the process that requires water and chemical cleaners, creates waste that requires disposal or removal. By contrast, the non-abrasive polycarbonate media for cryogenic deflashing can be reused many times. Dry tumbling doesn’t require water or chemicals, but it raises environmental health and safety concerns because workers are exposed to abrasive dust and high levels of noise. A non-abrasive plastic media can be used instead, but it’s significantly more expensive.
The Best Way to Deflash Molded Medical Parts
Do you need a better way to remove molding flash? Then why not try the best available option? Contact the experts at Nitrofreeze® to discuss your application requirements. If your part is a viable candidate for cryogenic deflashing, we can perform sampling to demonstrate our process. The consultation is free of charge and turnaround times average two days. To get started with deflashing for plastic and molded parts, contact us at the phone number and email listed below.
(508) 459-7447 x 105 | info@nitrofreeze.com