CNC Machine Maintenance: Tips, Insights, and Preventative Maintenance Checklists

12/09/2021 | Paul Endries

“Don’t skimp on the maintenance!”

As far as manufacturing advice goes, that’s solid wisdom. Think about it: nothing gets done when CNC machines are down, and it takes proper machine maintenance to keep them up and running.

A machine breakdown can cost a business thousands of dollars in wasted hours, overnight shipping of replacement parts, and missed deliveries, not to mention a damaged reputation. With so much high-tech equipment in one area, breakdowns are inevitable. However, performing regular maintenance helps keep the machines running properly, eliminating the possibility of a costly shutdown.

Let’s explore CNC machine maintenance in more detail.

What CNC Machine Maintenance Is Needed?

As complex and precise as CNC machines are (cutting to within 0.0001”), maintenance is relatively simple stuff … simple but critical. After all, CNC machine damage is a costly mistake no shop can afford.

A complete list of all maintenance steps would take up this entire article, but it’s easy (and important) to review the basics.

Coolant — Tooling moves quickly, which means heat. Without proper coolant levels and concentration, Parts being machined and tooling will quickly become ruined.

Cooling Oils---spindles move quickly, and often run over 10,000 RPM. which means heat. Thermal problems are easy to avoid with the right cooling system in place, and temperature sensors alert to anything out of the ordinary.

Lubrication — In most machinery, oil/grease keeps things running smoothly. Moving parts get dry and need lubrication to reduce unwanted wear.

Other fluid levels, such as hydraulic fluid, need to be replenished in CNC machines, too. Excessive use of fluids is a red flag that the machine may have a problem.

Surfaces — Shop grime builds up if left unchecked. Wipe down all surfaces — window, door, light, handle, etc. — to ensure visibility, good grip, and an overall clean working environment.

Another responsibility of maintenance is a skill that isn’t found in a CNC machine manufacturer’s operating guide: listening. A seasoned maintenance pro knows these machines inside and out, and they know what they should sound like when humming at full speed. For instance, when a machine experiences even the slightest mechanical failure, it sounds different. Odd sounds during a cycle is an instant red flag that something’s not right.

How Often Should Maintenance Be Done?

An unplanned CNC machine breakdown typically costs about 5 times more than it does to create an annual maintenance plan, often called a “Preventive Maintenance Plan.” Maintenance done on a routine basis helps ensure that CNC machines hold up; but what is that routine, and how often do tasks need to be completed?

CNC machine manufacturers do recommend certain maintenance intervals for their machines, yet many CNC machines shops alter those based on their own production needs and experience. It’s not that the OEM’s recommendations are incorrect, it’s more about each shop establishing a flow for top-end performance and controlling downtime.

A plan alone isn’t enough. A CNC machine’s sophisticated, automated sensors and detector systems also flag potential problems, alerting maintenance crews to areas that need attention. For example, when a hydraulic hose bursts, The machine will detect the loss of pressure and stop the cycle to avoid further damage. The machine also sends an alarm notification to the operator. In the case of a more serious issue, not only is the machine operator alerted,  an email is sent to the supervisor. Fortunately, most CNC machines are robustly built, so it takes a lot to seriously damage them.

It makes sense for CNC machine maintenance to be based on hours of use, similar to changing your car’s oil every 5,000 miles. But that strategy makes it tremendously difficult to monitor dozens, or even hundreds, of CNC machines within a single shop. It’s much easier to schedule preventive maintenance on all machines shop-wide every day or month or year.

The following is not a comprehensive list, but it covers the majority of what needs to be done at different intervals.

Daily Maintenance:

  • Check lubrication levels; replenish if needed
  • Grease parts that look dry
  • Check coolant concentration and fill levels
  • Empty chip hopper
  • Check levels of hydraulic system
  • Wipe down all surfaces to keep small metal shavings from building up

Monthly Maintenance:

  • Clean/replace air filters
  • Check and clean coolant filters
  • Clean radiators and cooling fans
  • Review oil fill checklists for unusual oil consumption
  • Remove and clean chuck and jaws
  • Grease and adjust chains or conveyors

Yearly Maintenance:

  • Remove coolant tank completely; take out metal chips not caught by the conveyor; check for bacterial growth; inspect and clean the system
  • Test hydraulic oil for contaminates; replace filters
  • Drain and clean lubrication unit; change oil
  • Check headstock for tapering
  • Check drawbar tension
  • Inspect chuck cylinder
  • Run backlash program; replace the X and Y axis gibs if needed

Depending on the shop’s size and number of machines, the daily tasks alone may be enough to keep several maintenance people fully employed. Smaller shops may ask CNC machine operators to handle their own machine’s daily maintenance needs (lubrication, coolant, etc.), which no doubt cuts into their productivity.

Full Maintenance = Machine Efficiency = Satisfied Customers

Although not all CNC machines perform the same tasks, their maintenance needs are very similar: lubrication, coolant, filters, etc. Robotics is another story. Those beasts take robustness to another level, requiring very little overall maintenance.

When it comes to breakdowns, prevention is the goal, but repairs are a reality, too. 

A shop that has the internal resources needed to get machines back up and running changes the game. Outside support takes time and costs money, however internal maintenance crews can jump on a CNC machine breakdown, resulting in reduced downtime. As long as parts are available in-house, repair times are usually minimal. This efficiency is not only seen in the bottom line but also in on-time delivery with happy customers.

Trusted Performance For Years

How long do CNC machines usually last with proper maintenance? Trusted performance can be expected for as long as 20 years. Again, these are rugged machines built to withstand harsh environments and continuous use.

Most often, machine replacement is dictated by a newer technology or faster capability rather than a catastrophic breakdown. Accuracy issues are usually the first telltale sign that a machine is reaching its end, often far enough that no maintenance intervention can bring it back.

The right CNC machine maintenance not only results in high-end performance, it also means peace of mind. Operators and supervisors know that these valuable pieces of equipment are well cared for, and instant alerts will be sent if a problem occurs.

However, peace of mind really rests on the reliability of the information in a shop’s preventive maintenance system. Documentation of everything —  machine inspection, service, issues, replacement — is critical in evaluating maintenance’s effectiveness and how much you can rely on it to make future business decisions.

Pallet-jacks, forklifts, floor scrubbers. A valued maintenance professional’s knowledge goes beyond CNC machines, of course. To be successful, it takes a mind that always asks, “What makes it tick?”

Careers in CNC Machine Maintenance

Want to work as a CNC machine shop maintenance pro? There are not many formal educational paths to success; you just need to have a knack at fixing things and have good problem-solving skills.

This desire to learn overcomes any education or prior knowledge. In general, CNC machine shops have a reputation for training their own on that shop’s unique needs. In fact, the internal training depth at a CNC machine shop runs deeper than most manufacturers. 

Shortsighted machine shops may see maintenance as a function that doesn’t bring in money. But, when a CNC machine goes down and the shop is in a jam, the maintenance team becomes a lifesaver.

That’s why we should always remember: “Don’t skimp on the maintenance!”

Proper maintenance goes hand-in-hand with lean manufacturing. Get an overview of lean, including actionable insights, by reading our eBook: The Benefits of Lean Manufacturing in Machine Shops.

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Paul Endries

About the Author

Paul is the Maintenance Manager, and his maintenance philosophy is straightforward. Keep machines running. Do whatever we can do to keep production going. It's important to find balance between manufacturing and maintenance. Enthusiastically embrace and helps adopt new technology to grow the company.

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