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How to catch and prevent defects during injection molding

Contributed by: Sciemetric Staff

injection mold application

From bottle caps to toys and complex automotive components, injection molding is a common manufacturing process. Defects and scrap can also be common without appropriate quality checks. How do you ensure a proper mold in production real-time without costly quality inspection delays?

Common problems with injection mold applications 

Injection molding can suffer from a number of issues that impact part/product quality. The variance from a good part may be purely aesthetic – such as superficial surface defects that impact product appearance and require additional finishing steps, or that lead to outright scrap. While these can be caught with visual inspection, such inspection methods can be time-consuming, costly, and inconsistent depending on the diligence of the inspector.

Then there are the hazards that may lie unseen below the surface and risk part failure. For example, simple visual inspection can’t easily detect defects such as air pockets, or mold materials that have been compromised by overheating. In these cases, quality issues are more likely to not show up until there’s a warranty claim from the field.

The key to reliable injection molding quality assurance is being able to effectively catch defects before they leave the factory, or even better, before they leave the station or process in which a quality problem has occurred. The closer to its point of origin you can detect any defect, the less costly and disruptive to the line it will be to fix. 

But how do you apply such real-time quality checks to an injection molding station?

Easy. By adding to the station digital pressure sensors and analytics software that will track the common feature checks that can flag a poor or otherwise defective mold.

The proof is in the production data: Monitoring an injection nozzle can highlight many problems  

With the addition of these tools, the station’s injection nozzle becomes a rich source of real-time production data. Injection pressure, flow, temperature, and vibration can all be captured, measured, and visualized to provide the station operator with quick insight to detect the most common injection molding problems, such as:

  • sigPOD screen
    The above shows a sigPOD PSV™ (process signature verification) software screen, using the Injection Mold template, designed to monitor the injection molding process.
  • Sink marks
  • Voids
  • Part shrinkage
  • Brittle parts
  • Poor appearance
  • Mold and machine nozzle wear
  • Debris or hardened material



Case Study: Automaker turns to Sciemetric to tackle its injection-molding issues

Take this example, from the plant floor of a global auto maker that worked with Sciemetric to tackle quality issues with its injection-molded car bumpers.

The injection molding operation for bumpers and other plastic parts didn’t always produce at the desired level of quality. In addition, the mold machine would shut down and stop production due to unexpected machine component failure. 

The automaker lacked the data or insight to determine why these issues were occurring and how best to address them. 

Sciemetric’s data-driven intelligence identifies issues early

We added digital pressure sensors to the injection nozzle of the mold station, connected to a Sciemetric sigPOD set up to measure and monitor clamp pressure, injection pressure, injector position, injector temperature, and cavity temperature. This setup could detect the overheating, air pockets, over/under fill of the mold and other indicators of a flawed process and a defective part. 

The sigPOD captures the full digital process signature, or waveform, of each injection cycle, and monitors for any variance outside of the accepted norm for a “good” part. Additional analytics could also be performed offline with our QualityWorX software to proactively review and continuously improve the process.

sigPOD has led to more reliable and consistent defect detection for quality issues such as excessive flash, parting lines, weld lines, shrinkage, warping and sink marks in molded parts. Time-consuming subjective testing has been replaced with hard data and real-time analysis that prevents down-time, cuts scrap rates and improves preventative machine maintenance.

Contact us to learn more

Sciemetric offers a free pre-configured sigPOD template for injection mold monitoring applications. This template is easily customized to get you up and running in record time. Check out our sigPOD Injection Mold Monitor Application Guide to learn more.