It’s a mistake to think that every measurement system, or at least those of a roughly similar pedigree, were the same and would produce the same results when applied to the task of measuring machine tool workpieces. Different measurement systems can produce quite different results from each other - mainly depending on the approach and technology they use.

In this blog, we’ll examine the factors that can influence the accuracy, precision, and reliability of measurements, including the type of measurement system, environmental conditions, and the specific application involved. Then, we’ll look more closely at one approach, the camera-based measurement system, which has some inherent advantages. We’ll explain why that’s the case.

There’s more than one type of measurement system

It’s implicit from the opening paragraph that not all measurement systems are created equal and, therefore, there must be more than one type. The four principal approaches can be categorized as follows:

• Contact measurement systems physically touch the workpiece being measured (a coordinated measuring machine (CMM) is an example of this breed). These systems can be very accurate, but the results they yield can also be influenced by factors like surface roughness and probe deflection.

• Non-contact measurement systems (laser scanners and optical sensors are examples here) measure a workpiece without any physical contact. Faster and less subject to wear and tear which are pluses, they can be affected by surface reflectivity and ambient lighting conditions.

• In-process measurement systems are those integrated into machine tools, and they take measurements during the manufacturing process. It’s easy to guess the limitation here: their accuracy may be compromised by vibrations, temperature variations, other environmental factors present during machining.

• Post-process measurement systems work after manufacturing is completed. On the upside, these tend to have a high degree of accuracy. On the downside, they provide no real-time feedback that would otherwise enable immediate corrective actions where issues were detected in the machining process.

How do we evaluate the systems? How do they differ?

How, in more detail, do these systems differ from each other, and where should we look for the differences? The obvious answer is, in their accuracy and precision. While it’s true that whichever system is deployed, regular calibration will be critical, different systems will still follow different procedures which lead to their getting slightly different results.

One reason is resolution, meaning what’s the smallest increment a particular system can detect. Some systems have higher resolutions that others, meaning they can provide more detailed measurements though they may be more susceptible to noise and other interferences as a consequence.

Another way we can evaluate systems lies in repeatability; their ability to produce consistent results under the same conditions. High repeatability is essential for reliable measurements, regardless of the type of system.

It’s also worth noting that there is another level, beyond mere repeatability: reproducibility. Reproducibility is the ability to measure in different conditions and with different tools. This is difficult – but highly desirable. And we also need to consider environmental factors which, as we alluded to above, impact some approaches to measurement more than others.

Variations in temperature can cause materials to expand or contract, affecting measurement accuracy. Some measurement systems are more subject to this than others. There are also factors like dust and humidity to consider, which particularly impact non-contact optical systems.

And then there’s the question of measurement strategy (how and what the system measures). Does the system take single- or multi-point measurements? The former may yield results more quickly, but at the cost of not capturing the full geometry of the workpiece being measured. The latter may provide more comprehensive outcomes, but at the cost of complexity and the time required.

Lastly, there’s the question of data. Different measurement systems use different algorithms and software to interpret the data they collect, often leading to slight variations in the results they deliver. Data analytic techniques such as filtering out noise or averaging multiple measurements can also affect these outcomes.

The bottom line is that different measurement systems don’t produce exactly the same result as each other. How you measure something does influence the results you get. That means it’s critical to understand the limitations and capabilities of each measurement system you’re considering, maintain proper calibration, and consider environmental conditions. You must account for these variables and, if necessary, apply corrective factors or use standardized measurement procedures to avoid issues.

The camera-based advantage

Camera-based measurement systems, which fall into the broad genre of vision or optical measurement systems, offer several advantages for measuring workpieces so let’s look at those in more detail. What are the pluses:

1. Because there’s no contact in camera-based systems (they measure without physically touching the workpiece), the risk of damaging delicate or sensitive surfaces is eliminated. Additionally, without contact the system itself won’t suffer from wear and tear, thus maintaining accuracy over a longer period.

2. Camera-based systems are fast and efficient. They can quickly capture large amounts of data, and provide real-time measurement and inspection, enabling immediate feedback and adjustments to be made during the manufacturing process. Furthermore, they are able to measure complex shapes and geometries that might be challenging for contact-based systems which means they’re highly adaptable. They can be used for a wide range of applications, from small precision parts to far larger ones.

3. Unsurprisingly, high-resolution cameras and advanced optics can capture fine details with accuracy. This includes measuring minute features and small dimensions with high precision.

4. Camera-based systems are also easier to integrate into other automated systems which enables continuous measurement and inspection without human intervention and leads to streamlined workflows and better process automation.

5. They’re also able to measure in three dimensions, providing a complete spatial representation of the workpiece being measured. This includes surface contours, profiles, and topography.

6. Camera-based systems are generally equipped with user-friendly software interfaces and these both simplify the process of measuring as well as facilitating data analysis. They make it easier to understand and interpret measurement data as they can provide visual representations of results.

7. The improved quality control of manufacturing outputs is another big plus. Camera-based systems excel in this area due to their ability to quickly and accurately detect defects, inconsistencies, and deviations from specifications. This also improves product quality.

8. Camera-based systems are less sensitive to environmental conditions such as the temperature variations and vibrations that can affect contact-based systems.

9. Lastly, with camera-based systems measurements are automatically recorded and can thus be easily stored, retrieved, and analyzed. This helps to ensure traceability and provides comprehensive documentation for quality assurance and compliance purposes.

In summary, while there is a choice of approaches to measurement and different types of system yielding slightly different results, camera-based measurement systems offer numerous advantages – particularly when mounted inside the machine, where the action takes place, so expediting production.

In modern manufacturing environments where precision, efficiency, and automation are essential, they’re possibly the best way to go to get the accurate and precise measurement results you’re looking for – find out more by talking to our team. 

About Conoptica

Conoptica has been providing high tech camera-based measurement solutions for the metal working industry since the 1993. We make sure that the metal working industry has access to key quantitative data about their products and tools. Conoptica is the market leader for measurement equipment in the wire & cable industry.