CMM vs. Manual Measurement – Which Makes Sense & When?
From time-tested hand tools to cutting-edge automated technologies like coordinate measuring machines (CMMs), dimensional measurement can be done in a myriad of ways. The best method for your project depends on what you need to measure and the level of precision your project demands.
In general, manually operated hand tools such as calipers and micrometers are best used on a small scale, when basic measurements will suffice. When the job calls for ultra precise measurements, or when complex geometries or mass production are involved, CMMs deliver greater accuracy, speed and versatility.
Traditional Measurement Tools — Capabilities & Limitations
Traditional hand tools are typically simple to use and provide reliable methods of measurement. Below is an overview of the capabilities and drawbacks of some classic hand tools.
| Tool | Capabilities | Limitations |
|---|---|---|
| Caliper |
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| Micrometer |
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| Height Gauge |
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| Tape Measure |
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Benefits of Using CMMs
CMMs use a probe to automatically capture a large number of data points and calculate precise dimensions. CMMs match and surpass the capabilities of hand tools, and overcome the limitations of manual methods, to deliver far greater accuracy and flexibility. The benefits of CMMs include:
- Advanced Measurement Capabilities: CMMs can accurately measure a wide variety of sizes and far more complex shapes and contours than traditional tools can tackle, including 3D shapes, levels, and fully assembled components.
- Greater Precision: Compared to the micron-level accuracy offered by some traditional tools, CMMs deliver sub-micron precision, making them ideal for applications where there is little room for error.
- Time & Cost Savings: Because they are automated, CMMs can measure multiple dimensions and multiple parts far more quickly than hand tools, saving manufacturers time and money.
- Greater Reliability: By helping to avoid the risk of human error associated with manual measurement, CMM technology provides consistently reliable measurements.
CMM Limitations
While CMMs offer many significant advantages, including accuracy and versatility, there are limitations to consider as well:
- Cost: The initial investment in a CMM can be substantial; and ongoing maintenance and probe calibration costs should be considered, too.
- Size: Today’s large CMMs have a significant footprint, requiring a large, temperature-controlled space to ensure measurement accuracy.
- Complexity: CMMs can be complicated to operate, requiring specialized knowledge, training and skills. In addition, different CMMs use different software, adding to the complexity.
- Measurement Limitations: Some CMMs cannot measure certain items and are not well-suited for all applications.
The limitations of CMMs should be taken into account when considering alternate measurement methods. It’s important to note, however, that when you partner with a well-equipped metrology lab like Industrial Inspection & Analysis (IIA), limitations like cost, size and operational complexity become irrelevant.
For example, IIA has already invested in an array of CMM machines, and offers affordable measurement services to customers. Likewise, our customers need not worry about making space for a large CMM in an environmentally controlled lab or hiring and training staff on the operation of various CMM machines. In addition, our metrology labs have alternate tools available for instances where CMM measurement is not suitable for a particular object or application.
When deciding which measurement method to use, consider the capabilities and limitations of hand tools and CMMs to the item you need to measure and the accuracy your project demands.
Conclusion
It’s great to have traditional hand tools in your toolbox and know how to use them, but if you’re looking for ways to streamline your inspection process, more advanced measurement tools like CMMs are a good investment. You can save even more time and money when you partner with a leader in dimensional measurement like Industrial Inspection & Analysis (IIA).
Across the U.S., our ISO-accredited labs are equipped with an array of state-of-the-art CMMs to meet your unique needs — from touch probe CMMs to the world’s first purely optical CMM. When you let our metrology experts focus on what they do best, you can focus on what you do best: manufacturing a quality product.
