rubber deflashing | Injection Molding Flash

Injection Molding Flash and Cryogenic Flash Removal


Injection molding flash is excess material that is forced out of a mold cavity at the parting line or ejector pin locations. This molding defect mars the surface finish of injection molded parts and can interfere with sealing, mating, or assembly. Traditionally, injection molders removed flash by hand. Yet manual trimming is time-consuming and can result in parts with different levels of surface quality. Plus, workers can deflash only one part at a time. They also risk changing part tolerances by removing too much material.

By contrast, cryogenic flash removal is fast, consistent, and cost-effective. This computer-controlled, semi-automated batch process speeds deflashing times, eliminates part-to-part differences, and reduces labor costs. The safe, clean, non-abrasive media that’s used won’t change part tolerances or harm surface finishes either. By simply changing the process parameters and the media size, the same cryogenic deflashing equipment can be used with molded parts such as grommets, O-rings, bumpers, and  gaskets.

What Causes Injection Molding Flash?

Injection molding supports quick cycle times, custom shapes, and a wide range of molded plastic and rubber materials. The advantages of this manufacturing process include precision, repeatability, and a relatively low cost per part across high volumes. Although injection molding minimizes material waste, the initial costs are high. Depending on the part, tooling can cost tens of thousands of dollars. Consequently, there is a financial incentive to retain and restore injection molds.

Yet, worn tooling can result in parting line mismatches. Dust, dirt, residues, and contaminants can also prevent the mold’s core and cavity from mating tightly and closing properly. Injection molded parts with complex geometries are also subject to flashing, especially if there are problems with the mold design or with restoring older molds. Flashing can also result form improper venting, inadequate clamping pressure, poor sprue bushing support, and excessively low viscosity of the mold material.

Disadvantages of Manual Flash Removal

Injection molders have a choice of deflashing methods for plastic and rubber parts. Typically, manual processes involve cutting or trimming thin layers of flash with scissors and knives. Although the costs of these tools are low, the labor costs are high – especially for injection molded parts with challenging geometries. Importantly, hand trimming also introduces part-to-part variations. In applications such as medical device manufacturing, these inconsistencies can carry significant risks, even with prototype injection molding.

Die punching affords another way to remove mold flash. Workers place the injection molded part into a die that is shaped like the finished part. The parts are then punched out onto a flash mat, much as baker uses a cookie cutter. Die punching can provide more consistent quality than manual trimming, but it’s still labor intensive and results in lower production outputs. Injection molders with workforce challenges also face an opportunity cost by deploying skilled labor in this way.

Advantages of Cryogenic Flash Removal

Cryogenic deflashing for injection molded parts provides important advantages over manual trimming and die punching. Although an operator loads and unloads a parts basket, the cryogenic deflashing process itself is automated. This ensures the high-quality removal of mold flash and eliminates part-to-part variations. Whether you need to deflash tens of parts of hundreds or thousands of parts, Nitrofreeze® can determine the optimal recipe for flash removal. At our Worcester, Massachusetts (USA) facility, we also perform initial sampling and inspect your parts both before and after deflashing.

Cryogenic deflashing uses very low temperatures to embrittle injection mold flash for ease-of-removal; however, the process does not change the physical or mechanical properties of your parts. The blast media, a cryogenic-grade polycarbonate, comes in different lengths and diameters to allow processing without impacting critical tolerances or surface finishes. Except for the absence of flash, your injection molded parts will look the same as they did before. And without the flash, they’ll look and work better.

How to Remove Injection Mold Flash

Do you need a more efficient way to remove injection mold flash? The experts at Nitrofreeze® are ready 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, contact Nitrofreeze® at the phone number and email listed below.

(508) 459-7447 x109 |