Maintaining inspection equipment--any type of equipment for that matter--is generally viewed as a nuisance, and manufacturers rarely think about the benefits, only the costs involved. In fact, machine maintenance is not only necessary to keep the system in optimal condition, it also offers several benefits that positively affect the bottom line, enhance product quality, and protect your investment.
Proper maintenance of coordinate measuring machines (CMMs) basically requires two key services that are often confused: Preventative maintenance (PM) and machine calibration. Maintenance includes machine inspection, replacement of worn or damaged components, hardware (mechanical/electrical) adjustments, and thorough cleaning to ensure that the machine is in a reliable condition. Calibration service generally consists of verifying how accurately the machine measures a workpiece, and any adjustments that are needed to achieve optimal data results.
Many owners of CMMs believe that a calibration is sufficient to keep their machine running and in peak condition. In reality, calibrating a machine without performing preventative maintenance leaves the manufacturer open to problematic, possibly costly, repair services. To avoid unnecessary repairs, emphasis on preventative maintenance should be considered in addition to the usual calibration work that will be done during your next scheduled service.
Before scheduling a service call, manufacturers should define a few machine specifics for the service personnel, such as:
What are the quality requirements? Does the machine need an ISO 17025 calibration?
ISO 17025 is a calibration-system standard and a requirement for manufacturers producing parts for an automotive manufacturer. It's a documented quality process that provides information on how the machine is performing before it's serviced--that is, it informs the service technician of any problems with data quality up to that point. Both the before-calibration and after-calibration data include linear- measurement uncertainty and scanning-performance uncertainty data, and this information is only produced by this particular process.
What is the operational uptime? How many hours per day is the machine used?
Many manufacturers run more than one shift. Calculated over one year, one shift generally adds up to 2000 hr of machine operation, if the machine is used throughout the course of that shift. If the machine is operated on a two or three-shift schedule, the frequency of machine-maintenance and machine-calibration services should be increased to ensure best performance. When it comes to service visits, the manufacturer's recommended maintenance intervals serve as your guideline and should be followed.
Utilizing a full service provider, in most cases the original manufacturer of the CMM, and understanding your operational needs, are the keys to ensuring that your machine is in optimum condition. Full-service providers can help you develop and implement a machine-maintenance program tailored to your company's operational requirements. While on-site, well-trained technicians from full-service OEMs can identify performance issues, and correct them. Immediate correction of any suboptimal performance prevents future machine failure, and also saves you the cost associated with a follow-up repair service. In addition, good technicians can adjust the machine's mechanics, controller, or accuracy. Keep in mind that making such adjustments generally requires using the CMM manufacturer's proprietary software.
The benefits that arise from maintaining your inspection system not only include increased machine uptime, but also extended component lifetime, lower maintenance costs, and optimal inspection results. After a complete maintenance service has been performed, the machine is going to be in a reliable condition for basically one year, or 2000 hr of operation. Planned maintenance is certainly preferable to the expensive and unnecessary downtime that can result when a machine is not properly adjusted.
A few CMM manufacturers even offer remote services that can make an on-site service call unnecessary, or reduce its costs, because technicians can determine which part to bring on-line, before coming to your site. For remote service, only a network connection is needed to allow opt-in desktop sharing, and therefore monitoring of the CMM computer and machine. Remote service can put your machine back into action quickly, and help to reduce downtime.
In a nutshell, maintenance and calibration services are basically designed to help keep CMMs in peak form. Proper maintenance decreases unscheduled repairs, which in turn reduces overall service costs. Maintained parts function better for a longer period of time, and help your equipment provide consistent results.
This article was first published in the October 2005 edition of Manufacturing Engineering magazine.