Computer Numerical Control (CNC) machines are heavy-duty and extremely accurate performers. Machine tools such as lathes, milling machines, and multi-axis machining centers perform multiple complicated machining tasks at the same time and sometimes lead to long uninterrupted periods of production. Studies show that manufacturing and process industries lose an estimated $20 to $60 billion each year due to unscheduled downtime and poor asset quality. Because of this, preventive maintenance is needed to help the company catch minor issues before the machines cause major breakdowns, which saves time and money in the long run while keeping it at peak performance. An unplanned CNC machine breakdown typically costs about five times more than having a Preventive Maintenance Plan. Therefore, investing in preventive maintenance makes the company save from 12 to 18% in total maintenance, compared to reactive ones.
Preventive maintenance, also known as “planned” maintenance, is a proactive approach in which there is a planned time or schedule for a machine tool to be taken down for servicing so that its service life would be extended. Before companies schedule preventive maintenance, it should coincide with their equipment needs and not interrupt with their production. It can be figured out through the facility’s actual usage patterns and availability of the operators and the machine. Most companies do preventive maintenance daily, weekly, monthly, once every few months, or yearly which are performed by the machine operators. Some of these are:
- Daily or Weekly
- Check on the cutting tool, any leakage, or strange sounds
- Check the hydraulic systems for any leakage and ensure that the hydraulic pressure remains at 4.5 MPa, as well as the hydraulic fluids
- Check grease, chuck pressure, and ensure that spindles, chucks, and any moving parts are cleaned by brushes or flushed with coolant
- Check if the lubrication operating level is at the right level because failure to top up lubrication oil might cause the machine to stop or have insufficient stocks of the oil
- Check on air supply to make sure that it is clean and dry because dirty or humid air can affect production quality and result in costly damages
- Clean out chips to avoid chips overflow that result to blockage of production, but ensure that the chips are not blown off with an air gun to prevent damage
- Clean out the window of the door, wipe down stainless steel covers and lubricate machine’s moving parts using hydraulic oil
- Every three (3) months or 500 hours
- Check, clean or replace the filters on the coolant tank because drop of coolant levels below the limit may result in overheating and damage
- Check the chain on the chip conveyor and grease it
- Every six months (6) or 1000 hours
- Have the coolant tank cleaned of sludge, chips, and oil
- Remove the chuck and jaws off the machine and have it cleaned
- Drain and clean the hydraulic tank and replace the hydraulic oil
- Change the line and suction filters
- Clean the radiator and make sure that the radiator fins are straight and not damaged
- Drain and clean lubrication unit and add fresh lube
- Drain, clean, and refill cooling unit if the machine is equipped with it
- Check the levelling of the machine and adjust if necessary
- Inspect the wipers for any damage, then clean and replace damaged wipers
- Yearly or 2000 hours
- Check headstock for any damage or misalignments, and the spindle taper at milling machines
- Check spindle for radial and end play issues
- Check chuck cylinder for run out
- Check tailstock for misalignment and quill function
- Check the turret parallelism and inclination
- Run a backlash program to check the backlash in the X, Y, and Z axis and adjust if necessary
- Check the X, Y, and Z axis gibs and adjust if necessary
- Check the whole machine for leakage of oil or air
It is also important to have employees or operators that are knowledgeable about the machine’s condition and performance so they can figure out the system errors, highlight maintenance requirements, and pass it on to the management through an easy-to-use reporting system. However, breakdowns are not entirely avoidable so spare parts should be sourced before they are required. With this, they have plenty of time to look for the desired components and be prepared in case some of it needs to be replaced. It also reduces the possibility of an extended failure by purchasing parts with questionable quality.
When a company decides to do preventive maintenance, all processes, findings, and status should be documented to have a baseline of events and a checklist for future reference and to ensure reliable and accurate maintenance. With this, the company will be able to evaluate the true maintenance cost. It also helps the company keep track of components or parts, whether it needs to be repaired or replaced and be able to prepare it beforehand. Complete and strong records can also be used as a basis for making other business decisions.
A systematic and calibrated schedule of preventive maintenance can maximize CNC machine uptime and avoid disruption, while maintaining the accuracy and quality of the machined parts. Its goal is to maintain the machine before breakdown because unscheduled downtime causes disruption. If there is a disruption, the total output decreases. Preventive maintenance ensures that the machine tools will continue to function well despite of frequent and prolonged use. It also helps to steadily increase the profitability of the company, extend the lifespan of both the machine and cutting tools, minimize or eliminate accidents that can be dangerous for operators, reduce and avoid expensive repair costs when machines break down unexpectedly, and increase efficiency by using less material and reducing scrap materials.
Note that the more axes a CNC machine tool has, it is not only more critical to keep it aligned and calibrated but also it needs to do preventive maintenance more. Doing so keeps the CNC machine tool in a healthy running order, and as the saying goes, prevention is always better than cure. Although we can’t control the aging of the machine, we can control how well it ages with the help of CNC machine tool preventive maintenance. If you’re interested in purchasing a CNC machine, browse our extensive inventory of used CNC machines. Contact us at Tramar Industries and we’ll help you find the right machine for the job.