Discerning Processing Discontinuities During Manufacturing

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It is normal for the metal or components to go through various metallurgical changes during the manufacturing process. This holds true during machining and fabrication phases, including melting, rolling, stamping, forming, grinding, welding, plating, or heat treating. During these processes, it is common to develop some processing discontinuities. Investigating the extent of these discontinuities can be challenging for technicians, especially if they rely on visual inspection.

Nondestructive testing (NDT) technologies effectively identify material imperfections at all stages of production without damaging the properties or performance ability of the material.  In particular, Eddy current (EC) testing and ultrasonic testing (UT), can look into these processing discontinuities for in-depth analysis and keep them off the production line. 

Understanding Processing Discontinuities In Manufacturing Setting

Discontinuities originate when the materials are subjected to extreme stress or temperature to alter the physical or chemical properties to satisfy the manufacturing needs.  These may appear in the form of inclusions, cracks, laps, seams, laminations, shrinkages, cold shuts, voids, and so on. Depending on when and how they are formed, processing discontinuities can be classified as:

1. Primary processing discontinuities: These discontinuities occur in the primary manufacturing phases when the metal ingots are worked down using casting, hot and cold forming, and rolling processes to give it a desirable shape and size. Poor practices, rapid temperature changes, extreme stress application, and improper surface preparation contribute to the following types of primary processing discontinuities:

Casting discontinuities	Porosity, cold shuts, shrinkage, dross
Rolling discontinuities	Laminations, stringers
Forging discontinuities	Laps, bursts

2. Secondary processing discontinuities: These discontinuities originate during the finishing operations, such as grinding, heat treating, plating, grinding, welding, and machining. The most prominent types of secondary processing discontinuities include:

Machining discontinuities	Tears
Grinding discontinuities	Cracks
Heat treating discontinuities	Stress cracking
Welding discontinuities	Undercut, lack of fusion, porosity, cracks, inclusions, lamellar tearing

As industries use these processed materials further down the production line, ensuring their defect-free status becomes vital for analyzing the safety and quality of the product. This confirmation can be achieved with EC and UT methods of NDT testing. 

Volumetric Inspection of Processing Discontinuities With NDT 

From raw metal ingot to the processed final product, at each stage of production, NDT can recognize indications of flaws. With eddy current testing, the probability, and accuracy of detecting surface or near-surface flaws increases. With ultrasonic testing, in-depth, volumetric subsurface flaws can be identified by focusing on the ultrasonic beam and analyzing the deflection. 

Although the accuracy and precision in an inspection are an advantage, the sheer scale desired for maintaining a healthy production level in the manufacturing industry can be challenging for complex inspections using regular NDT instruments. NDT instruments with scalability options can be used as a solution. These instruments can be configured to scale, and multiple units can be stacked together and operated in parallel to cover a wide inspection area. This approach is advantageous for the following reasons:

• Large volumes of data collected in a single scan can help in detailed inspection and analysis.
• Volumetric scanning increases inspection speed fostering higher productivity.
• Real-time inspection can help in the speedy analysis and immediate filtering of defective products.   

With the flexibility to inspect complex geometries and scalability to test volumes of products, discontinuities during manufacturing can be easily discerned while avoiding bottlenecks in the production environment.  

NDT Enhances Productivity and Quality

Metal processing is a common manufacturing phase, as is the inspection of processed products. Products with discontinuities can pose a significant risk to human lives, the environment, and the operation. NDT instruments can prevent these products with discontinuities from moving forward in the production stream. Through flexible, advanced, compact, and scalable instruments such as Zetec’s Emerald (www.zetec.com/emerald) and Quartz, manufacturers can look forward to increased productivity of quality products. 

Zetec’s advanced NDT instruments with powerful inspection and data analysis capabilities can provide reliable inspection results to meet your manufacturing standards. Contact us today to learn more about how Zetec can help improve quality by identifying processing discontinuities.