Eliminate CMM Bottlenecks

5 tips for easing the load of coordinate measuring machines

Final inspection of complicated parts, such as this
casting, can be performed on a CMM only if other, less
important measuring tasks are moved off the machine. Photo
courtesy of Creaform.

Final inspection of complicated parts, such as this casting, can be performed on a CMM only if other, less important measuring tasks are moved off the machine. Photo courtesy of Creaform.

For manufacturing companies, quality control and part inspection are key requirements before getting customer approval.

To perform these jobs, production managers generally choose a coordinate measuring machine (CMM), which is one of the most common types of metrology equipment used to inspect and control quality of manufactured parts.

However, this detour from the production floor to the metrology lab often may be long and arduous because the CMM -- being very popular -- is used by all operations in the shop. In addition to not being the fastest metrology tool in terms of programming and operating times, a CMM also requires moving parts, which often have large dimensions.

The mandatory stops at the CMM, and all the delays they cause, probably are far from being your favorite moments, because they slow down the execution of your work. Thus, production managers look for ways to solve CMM bottleneck issues.

But, before diving in, it is important to know the characteristics of CMMs:

Advantage: A CMM is an automated, precise measurement instrument.

Limitation: A CMM is fixed laboratory equipment that requires moving the part to the lab, and it has a defined and nonextendable measurement volume.

Following are five tactics that can enable you to ease the burden of your CMM and, therefore, speed up your overall manufacturing process.

1. Use the CMM only if necessary.

Select the measurements that should always be performed on a CMM and decide what others could be allocated to alternative methods that, although less accurate, will be sufficient for certain applications.

Portable metrology
equipment can provide
an alternative to remove
bottlenecks from the
CMM and improve
quality control. Photo
courtesy of Creaform.

Portable metrology equipment can provide an alternative to remove bottlenecks from the CMM and improve quality control. Photo courtesy of Creaform.

Use the CMM when highly accurate measurements are needed, for example performing final inspections, creating final compliance reports, and when analyzing contentious cases.

2. Look for alternative measuring methods.

Now that you’ve considerably reduced the inspections done on the CMM, it is judicious to develop a toolbox of alternative metrology methods for the other stages of the manufacturing process. These tactics can include:

  • First-article inspection. By using an alternate measuring method, you can perform a large number of measurements on a maximized number of parts without being limited by the capacity of the CMM, which includes the measuring time and the time it takes to move the parts to the laboratory.
  • Mass production with systematic control. Good and bad parts can be sorted rapidly without sending every one to the CMM. Dubious parts still can be brought to the CMM to remove any doubt. This tactic alone can help reduce the CMM load by almost 80 per cent of measured parts.
  • Mass production with sampling control. Another alternative to relying solely on a CMM, this method offers better monitoring of any possible drift—to anticipate adjustments—and ensures a seamless detection of random faults. A CMM then can be used to analyze only the most complex cases and determine corrective actions.

3. Use metrology equipment that requires less training.

Because the CMM is a complex metrology instrument, it needs to be handled by highly trained and experienced operators. When a more user-friendly tool is used to perform inspection at different stages, the intervention of a CMM operator is not required.

In addition, because other options do not require an advanced technician, more operators can use it, which increases the number of measurements that can be performed. The more measurements that can be carried out by an alternative method, the more accessible the CMM will be to perform final inspections, make final compliance reports, and analyze contentious cases.

4. Prioritize inspection directly on the production floor.

Some measurements should always be performed on a CMM. When these measurements are necessary, the CMM must be available. Thus, prioritizing measurements taken directly on the shop floor provides more accessibility to the CMM.

For example, if a part to be measured has large dimensions and cannot be easily moved, why lose time and energy taking it to the lab? In this case, it is preferable to use a portable metrology tool that lets you measure parts directly on the shop floor.

5. Take more measurements at intermediate steps.

Each step of a production process can create new issues, such as shrinkage, changing part thickness, and distortion. Because of this, the CMM is used abundantly, which requires a lot of back and forth at the beginning of production, creating a significant bottleneck effect that clogs the manufacturing process.

Performing inspections at intermediate steps helps prevent work load bottlenecks at the CMM and puts less pressure on the quality control operators. These operators are then able to supply more complete and documented inspection reports that will facilitate the customer’s verification and approval.

Portable metrology equipment can provide an alternative to remove bottlenecks from the CMM and improve quality control. Portable technology enables operators to take more reliable and a higher number of measurements directly on the production floor and at every step in the manufacturing process.

Daniel Brown is senior product manager, Creaform, 888-381-0039, www.creaform3d.com.

About the Author
Canadian Metalworking

Joe Thompson

Editor

416-1154 Warden Avenue

Toronto, M1R 0A1 Canada

905-315-8226

Joe Thompson has been covering the Canadian manufacturing sector for nearly two decades. He is responsible for the day-to-day editorial direction of the magazine, providing a uniquely Canadian look at the world of metal manufacturing.

An award-winning writer and graduate of the Sheridan College journalism program, he has published articles worldwide in a variety of industries, including manufacturing, pharmaceutical, medical, infrastructure, and entertainment.