6 Points To Better CMM Maintenance

Koon Hock Seng, regional service manager of Zeiss, takes a look at preventive and reactive maintenance and how they help maximise machine performance.

In the topic of maintenance, it is important to differentiate between preventive and reactive maintenance. Reactive maintenance is the process of reacting to failed, ineffective or damaged equipment and repairing or replacing it in order for the intended function to be achieved.

Essentially, reactive maintenance ignores any preventative measures and simply deals with a problem or issue when it is reported whereas in preventive maintenance, the primary goal of maintenance is to avoid or mitigate the consequences of equipment failure altogether. Preventive maintenance work includes tests, measurements, adjustments, and parts replacement for the purpose of maintaining equipment and facilities in satisfactory operating condition.

Care For Your CMM

As with all electromechanical machines, a Coordinate Measuring Machine (CMM) is subjected to environmental and usage influences which over time, can cause failure of the machine during operation. Many external factors influence a CMM performance. They are vibrations, temperature fluctuations, contamination, collisions, dust, humidity, usage and wear.

Aside from maximising machine performance and lifetime, regular maintenance increases machine safety, reduces downtime and unplanned breakdowns, monitors and analyses progressive failure, aid in spare parts planning and its cost is something that can be planned for.

Parts from a CMM subjected to wear and fatigue failure are:

• Air bearings (not for inline machine)
• Drives
• Friction transmissions or friction rollers
• Motors
• Controller electronics
• PC failures
• Excessive collusions affecting sensors or accuracy
• Pneumatic clogs

Good Maintenance Helps Save Costs
Your quality process in manufacturing is dependent on the CMM and other measuring processes. Upon owning a CMM, failure to recognise the importance of periodic servicing and maintenance can lead to regular breakdowns of even the best CMM and give rise to much reactive maintenance efforts.

The breakdown of your CMM also means breakdown of your manufacturing quality chain, affecting manufacturing machines heavily and indirectly increasing your breakdown overhead costs. Rather than constant firefighting, putting stress on both the service provider and your customers, perform a root cause analysis today for a more permanent solution.

Six Maintenance Tips For Your CMM

1. Guideway

The guideway is part of the measuring table and should be cleaned in the same way as the measuring table. Dust particles and the smallest of burrs on notches may damage the air bearings. Clean the guideway every day, or if necessary, more frequently.

2. Measuring Table

Any particles lying underneath the bearing surface may lead to inaccurate measurements. The surface of the measuring table and workpiece may be damaged.

3. Stylus Tips

The styli must be handled carefully. If force is exerted, the glued bond between the stylus tip and the stylus shaft may separate and the stylus shaft may bend or even break. Do not exert any force when cleaning.

• Clean the stylus tips with a lint-free cloth.
• Use a cleaning agent if required.
• Make sure that the stylus tip is free from cleaning agent residues.
• If material from the workpiece settles on the stylus tip, it can be removed with special solvents.
• An aluminium deposit can be removed with 10 percent NaOH solution (sodium hydroxide solution) or with
• 10 percent KOH solution (potassium hydroxide solution).
• Make sure that exposure to the solutions is not too long since they may attack the adhesive used to glue the stylus tip to the stylus shaft. For cleaning, proceed as follows:

Wear rubber gloves and safety goggles.

• Immerse a cloth in one of the two solvents and clean the probe element with the cloth.
• Rinse the stylus tip immediately with water and dry them.

4. Threaded Holes

Dust may accumulate in the threaded holes and threads. In order to ensure perfect condition of the threads, remove any dirt deposits from the threaded holes with a vacuum cleaner.

5. Reference Sphere

The reference sphere must be clean and in perfect condition to ensure correct qualification.

Clean the reference sphere with a lint-free cloth.
Use a cleaning agent if required.
Make sure that the reference sphere is free from cleaning agent residues.

6. Adaptor Plate

The adapter plate must be protected against soiling.

• Store the adapter plate in a dust-free and clean place, eg: in a cabinet or drawer, whenever it is not in use.
• Wipe off the adapter plate with a dry or damp cloth.
• Clean it with a mild cleaning agent.
• Dry it in order to prevent oxidation of its contacts.
• Make sure that there are no cleaning agent residues. The function of the adapter plate may be affected.

APMEN Metrology