Measure Parts Closely

Moving the inspection process to the shop floor can speed production while also making it more efficient. Photo courtesy of Carl Zeiss.

To be competitive, today’s machine shops must complete their work in the shortest time possible. When scrap and the requisite rework cause delays, it costs money. Moving the inspection process to the shop floor can speed production while making it more efficient. CIM—Canadian Industrial Machinery asked Peter Detmers, vice president of sales for Mitutoyo Canada, and Rob Johnston, product manager—Carl Zeiss IMT products for Elliott Matsuura Canada, for their opinions about shop floor measurement. Here’s what they had to say.

CIM: What are the benefits of having measurement capability on the shop floor?

Detmers: Today it is very important for shops to operate with high efficiency and produce good-quality parts each and every time. Adding measurement capability to the shop floor helps to maintain a controlled process because machine operators are able to respond quicker to process variation. This quick response ensures that scrap and rework are minimized, or possibly even eliminated, making the overall operation more efficient and, hopefully, profitable. Process monitoring through measurement can also be used to monitor other machine aspects such as tool wear.

Johnston: The closer you are to the process, the better you can provide real-time feedback. By having a CMM closer to manufacturing, machine operators and production staff become more engaged in the quality process. It puts more of a front-end emphasis on quality and process control.

CIM: What is enabling CMMs to now be part of the shop floor environment?

Detmers: One change is the addition of temperature compensation, which allows for temperature variations in the machine structure, as well as those in a part, to be compensated in real time.

Another important factor is new machine design related to shop environments. Many conventional CMMs use air bearings, which in a shop may become an issue when oils and dust are present. In these cases, we have designed machines with precision linear guides enclosed within the machine covers, allowing high-speed, highly accurate measurements in harsh environments.

Johnston: There are a couple of reasons behind this, including material sciences, perception, and more companies investing in their shop floor environment. Our Zeiss Maxline CMMs are built with materials that are resistant to temperature fluctuations and have vibration-dampening systems so they can be near the shop floor.

There also seems to be new openness to placing this technology on the floor, where historically people felt gauges were tried, tested, and true. In addition, many shops are installing demisters and dehumidifiers. This helps when putting precision measuring equipment closer to manufacturing.

CIM:How do you keep shop floor CMMs from becoming a bottleneck?

Fast response from the measurement process reduces scrap and rework, making the overall operation more efficient. Photo courtesy of Mitutoyo Canada.

Detmers: Our MACH series shop floor CMMs, for example, are high speed machines that enable the CMM to keep pace with the demanding tasks associated with shop floor needs. We also encourage manufacturers not to use the inline or sideline equipment in the same way they would use it for final inspection. They should use the machine to control the process, not to measure features that cannot be controlled. Additionally, if the shop has parts that go through many different machining or processing operations, checking them after each operation can prevent further work being done to a part that isn’t going to pass in the end.

Another way to improve the efficiency is to rely on the SPC [statistical process control] data to flag problematic features. If only a couple of features are difficult to maintain, then measurements should be concentrated on those features, thereby giving operators more ability to control the overall outcome.

Johnston: Many industries want 100 percent inspection on every part, which means the quality system can easily become the bottleneck, especially if the inspection time is longer than the machining and automation time.

Smart decision-making on critical features and using software correctly will keep CMMs from becoming a bottleneck. The shop must invest in good part planning to measure the critical features on the floor.

CIM: Is getting measurement data back to the production equipment as fast as possible important?

Detmers: Data transfer to the machine can be very important if tool wear can be offset to correct the problems found via measurement. These problems can be flagged in a few ways, either to the cell operator so he can react and make adjustments to the machine or process, or automatically via a machine tool offset package. These packages can allow the process to be automated so that typical wear issues can be adjusted for during the process, allowing for corrections before problems occur that can result in scrap or rework.

Johnston: The more parts that are inspected, the more data we have that can be statistically tracked. There are new products on the market that automatically read CMM data and provide secondary software tools to update machine tool offsets. This is great for cutter compensation and basic offsets.

When more complex 5-axis geometry is being inspected and analyzed to unconstrained datums, this sort of higher-level offset and corrections are still done through manual changes.

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