applicable to almost all control systems. The FANUC controller model is referenced here in order to provide clear explanations about one unified system. It is one of the most widely accepted, popular numerical control systems used worldwide.
Ken Evans, January 2016
1. Recognize the importance of safety when working with CNC machines.
2. Become familiar with tool and work holding methods for CNC machining.
3. Learn how to calculate proper feeds and speeds for CNC machining.
4. Learn how to plan for CNC programming by using process planning documents.
5. Become familiar with coordinate systems and their use in CNC programming.
6. Learn terminology associated with the basics of CNC.
7. Learn the ABCs of CNC program format.
As you begin to learn about CNC programming, it is important to become aware of and learn how to practice safe working habits. You should not operate any machine without first understanding the basic safety procedures necessary to protect yourself and others from injury and the equipment from damage. Most CNC machines are provided with a number of safety devices (door interlocks, etc.) that protect personnel and equipment from injury or damage. However, operators should not rely solely on these safety devices, but should operate the machine only after reading and fully understanding the safety precautions and basic operating practices outlined in the maintenance and operation manuals provided with the equipment. The following are some Do’s and Don’ts that should be practiced when working with CNC machines.
Safety Rules for NC and CNC Machines
Do’s:
• Wear safety glasses and safety shoes at all times.
• Know how to stop the machine under emergency conditions.
• Keep the surrounding area well lit, dry, and free from obstructions.
• Keep hands out of the path of moving parts during machining operations.
• Perform all setup procedures and loading or unloading of workpieces with the spindle stopped.
• Follow recommended safety policies and procedures when operating machinery, handling parts or tooling, and lifting.
• Make sure machine guards are in position during operation.
• Keep wrenches, tools, and parts away from the machine’s moving parts.
• Make sure fixtures and workpieces are securely clamped before starting the machine.
• Inspect cutting tools for wear or damage prior to use.
Don’ts:
• Never operate a machine until properly instructed in its use.
• Never wear neckties, long sleeves, wristwatches, rings, gloves, or loose long hair when operating any machine.
• Never attempt to remove metal chips with hands or fingers.
• Never direct compressed air at yourself or others.
• Never operate an NC/CNC machine without first consulting the specific operator manual for the machine.
• Never place hands near a revolving spindle.
• Electrical cabinet doors are to be opened only by qualified personnel for maintenance purposes.
A large investment has been made to purchase CNC equipment. It is very important to recognize the need for proper maintenance and a general upkeep of these machines. At the beginning of each opportunity to work on any turning or machining center, verify that all lubrication reservoirs are properly filled with the correct oils. The recommended oils are listed in the operation or maintenance manuals typically provided with the equipment. Sometimes there is a placard (plate) with a diagram of the machine and numbered locations for lubrication and the oil type is found on the machine. Most modern CNC machines have sensors that will not allow operation of the machine when the way or spindle oil levels are too low. Pneumatic (air) pressures need to be at a specified level and regulated properly. If the pressure is too low, some machine functions will not operate until the pressure is restored to normal. The standard air pressure setting is listed in pounds per square inch (PSI) and a pressure regulator is commonly located at the rear of the machine. Keeping machines maintained and in their optimum health is required to avoid costly failures and ensure maximum productivity. Check with your company and follow their Total Productive Maintenance (TPM) program. Refer to the operator or maintenance manuals for recommended maintenance activities.
Coolant Reservoir
The coolant tank level should be checked and adjusted as needed prior to use. A site glass is normally mounted on the tank for easy viewing. Use an acceptable water-soluble coolant mix, synthetic coolant, or cutting oil. Periodically the coolant tank should be cleaned and refilled. The coolant PH level should be checked routinely with a refractometer; the mixture should be adjusted in order to prevent bacterial growth. When synthetic coolants are used, the coolant system may stay clean longer.
Because machine slide-ways need constant lubrication during operation, automatic oiler systems inject an appropriate amount of oil at intervals determined by the builder. There is almost always excess oil that finds its way into the coolant system. Because of this condition, companies employ the use of add-on oil skimmers designed to clean the coolant. The “tramp oil” must be removed and discarded properly. Some new machine tools are incorporating sealed lubrication systems to help alleviate this problem.
Daily Maintenance Activities
Do’s:
• Verify that all lubrication reservoirs are filled.
• Verify air pressure level by examining the regulator on the machine.
• Check that the chip pan, coolant level, and mixture are correct; clean or fill, as needed.
• Make sure that automatic chip removal equipment is operational when the machine is cutting metal.
• Be sure that the worktable and all mating surfaces are clean and free from nicks or burrs.
• Check to see that the chuck pressure setting is adequate for clamping the work to be machined.
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