Buying a Coordinate Measuring Machine: CMMs Past and Future
While there has been much speculation that CMMs are becoming obsolete, the opposite is true.
Share
Coordinate measuring machines (CMMs) have been around since the 1960s. In most precision manufacturing facilities, the CMM is the company’s chief dimensional measurement device that is traceable to the standards maintained by National Institute of Standards & Technology (NIST). Most CMMs are used to verify dimensional accuracy for quality control (QC) and first-article inspection, the function of checking the first part produced by a manufacturing process to verify that it is meeting tolerance requirements. Inspection with a CMM provides data for in-process measurements to ensure dimensional integrity from operation to operation and to satisfy traceability requirements. CMMs are also used to perform gage repeatability and reproducibility (R&R) studies, 2D and 3D scanning, part sorting, reverse engineering and a host of other tasks.
By some estimates, the global installed base of CMMs is about 150,000 units. Because of the typical air-bearing design of many CMMs, the structure of these devices seldom wears out. Therefore, the lifespan of a CMM may exceed 30 years. Many 30-year-old CMMs are used daily throughout the precision manufacturing world. Older CMMs can be easily upgraded with new electronics, drives and the latest software, adding an extra 10 years to a machine’s usable life. In fact, a CMM can be retrofitted multiple times to extend its life even further.
During the past several decades, CMMs have become faster, more accurate and more affordable. While there has been much speculation that CMMs are becoming obsolete, the opposite is true. Today, CMMs are more versatile and functional than ever before.
Shop-Hardened CMMs
For all their advancements, CMMs have long been the source of bottlenecks and frustration on the manufacturing floor. Machine tools may sit idle for hours, even days, waiting for the inspection results from the QC lab prior to the production. It’s not hard to understand why many production managers would like to see CMMs taken out of the QC lab and put onto the manufacturing floor.
Unfortunately, CMMs utilizing the traditional air-bearing construction with granite tables do not perform well in an open shop environment. Unlike temperature-controlled QC labs, shopfloor conditions rarely can maintain a constant 68°F temperature considered optimal for CMM performance in a lab. When the ambient temperature varies, measurement results also vary. The laws of physics underlie these variabilities. Furthermore, holes in air bearings tend to clog with oil, dust and debris floating in the air when machine tools are nearby. In these conditions, a CMM will eventually stop working properly. Today, shop-hardened CMMs have emerged to resist these problems. For these devices, air bearings have been replaced with mechanical bearings and linear guideways. Machine components manufactured from thermally stable materials have resulted in stiffer, lighter structures and thermal compensation for use outside temperature-controlled settings. Machine footprints are smaller to take up less valuable manufacturing floor space. Cantilever designs, which offer the most effective measuring volume, are making a comeback for shop-hardened applications. Interestingly, cantilever designs were once the most common type of inspection machines in the early years of CMM technology.
The Future of Production CMMs
As for the future, I envision that there will come a time when all CMMs will be fully integrated into the manufacturing process as manufacturing companies continue to demand in-line measurements for immediate feedback. This will enable timely, in-line adjustments to eliminate scrap and improve quality.
CMMs will be treated like any other machine tool as an integral part of the manufacturing process. The same operator machining the part will also load the part onto the CMM and push the button. Simplicity and ease of use will be required for this integration. Developments advancing this trend include color mapping to show where a workpiece is in or out of tolerance. Easy-to-read reports will be the norm. Because machine operators are not metrologists, the information from the CMM must be displayed in easy-to-understand reports. Systems capable of performing measurements at different stages throughout the process without human intervention are emerging, and manufacturing processes will self-correct based on these automated measurements.
This is part one of a three-part series about buying a CMM.
Find more insights about acquiring a new machine tool by visiting the Techspex Knowledge Center, “Guide to Buying Machine Tools.”
Related Content
How to Choose the Correct Measuring Tool for Any Application
There are many options to choose from when deciding on a dimensional measurement tool. Consider these application-based factors when selecting a measurement solution.
Read MoreThe Link Between CNC Process Control and Powertrain Warranties
Ever since inventing the touch-trigger probe in 1972, Sir David McMurtry and his company Renishaw have been focused on achieving process control over its own manufacturing operations. That journey has had sweeping consequences for manufacturing at large.
Read MoreParts and Programs: Setup for Success
Tips for program and work setups that can simplify adjustments and troubleshooting.
Read More6 Machine Shop Essentials to Stay Competitive
If you want to streamline production and be competitive in the industry, you will need far more than a standard three-axis CNC mill or two-axis CNC lathe and a few measuring tools.
Read MoreRead Next
Inside Machineosaurus: Unique Job Shop with Dinosaur-Named CNC Machines, Four-Day Workweek & High-Precision Machining
Take a tour of Machineosaurus, a Massachusetts machine shop where every CNC machine is named after a dinosaur!
Read MoreThe Future of High Feed Milling in Modern Manufacturing
Achieve higher metal removal rates and enhanced predictability with ISCAR’s advanced high-feed milling tools — optimized for today’s competitive global market.
Read MoreIMTS 2024: Trends & Takeaways From the Modern Machine Shop Editorial Team
The Modern Machine Shop editorial team highlights their takeaways from IMTS 2024 in a video recap.
Read More