Machine Tool Maintenance

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by Douglas Rizzo

Your machine tool can last decades if you take care of it

Everyone in the shop remembers the day when the new CNC arrives. The riggers, the trucks, the people, the giant crate, the commotion, and the expectation. The new machine is uncrated, placed in position, leveled, wired, and ready to produce.

That beautiful, new, CNC machine tool, will, however, need some attention and with surprisingly little effort, can retain all of those wonderful qualities it had when new, throughout the years. A quality CNC machine tool can last 30 to 40 years, if given just a little preventative maintenance (PM) and care.

We break down basic operator PM into three categories: fans, filters, fluids. I’ll add a fourth, cleanliness.

• Fans: Most CNC’s have quite a few fans throughout their construction. When you power up, you can hear them running, and many times as you go through the power up sequence, you’ll hear more of them coming online. These fans are running at high speeds and move a huge quantity of air. Their function is critical. They are also widely overlooked, until bad things happen. We suggest these fans be checked casually every time the machine is fired, when the operator does a “walk around” but more closely inspected on a monthly basis. They should be kept clean of dirt and sludge to allow proper flow and replaced immediately when they fail. It’s much cheaper to replace a ball bearing fan than a CNC memory board that’s burned up from heat.

• Filters: Many fans on a machine tool will have a filter somewhere upstream. Some do not. Most of these filters are a nylon mesh, and are removable. We recommend these filters get cleaned once a month in normal shop conditions, or more often in extremely harsh environments. You will see just how fast they get plugged with coolant sludge, dust, and other particulates. Once plugged, the fans begin to pull harder and flow less, temperatures rise and the system comes under stress. In the summer, this can lead to an overheat condition or even a system failure. Remove the filter and clean it monthly at the least. Clean filters in the sink under running, cold tap water. No detergents, solvents, or chemicals are needed. Just cold water. Dry with dry, compressed air, and replace. Your CNC will be much happier. You may notice that some air inlets or fans do not have a filter. In those cases, placing some hand cut furnace filter from the hardware store in front of the air inlet/fan will increase fan life and cleanliness. When the furnace filter is dirty, remove and replace. It’s a lot easier than trying to clean an inaccessible fan or air duct.

• Fluids: The fluids in your CNC machine tool are its lifeblood. I’ve been amazed at the lack of attention this gets and the incredible amount of trouble, damage and even catastrophic failure that can result when fluids in a machine tool are ignored. The fluids in your machine have a finite life. They need to be changed and topped off. I’ve seen hydraulic systems so badly gummed that the pumps failed and lines had to be removed and purged to get the heavy scum out. Changing hydraulic fluid once a year will prevent this from happening. Cleaning strainers and filters will do a lot too. Use the correct fluid recommended by the manufacturer and use a brand name fluid. The added cost is due to proper chemical composition that can mean life or death for seals, pumps, motors and bearings. The same goes for Waylube systems. Even these, which get topped off regularly, need to have the tanks cleaned every so often to keep sludge from building up, plus, many have filters or strainers in them which need attention on a yearly basis. Coolants are critical too. Coolant that begins to “turn” will change Ph and destroy paint, rubber, seals, wiring and even bearing surfaces.

• Cleanliness: This is one area that even large, big name shops, skimp on. Cleaning the outside of the machine with some Simple Green or similar cleaner and a clean, soft, disposable towel will keep the machine looking good for customers, keep the shop looking straight for employees and help the machine tool retain value, as it won’t look like it was just pulled from the bottom of a river. Clean the inside with WD-40 or similar and the same can be said. I never leave chips or swarf on tables, turrets, or way surfaces. It can cause corrosion, staining, and surface damage. I recommend a soft paint brush to push the chips off into the pan. Pay attention to machining centre tool changers and lathe turrets. They can build up sludge and result in erratic operation. A simple cleaning and penetrating lube can keep them trouble free for years. SMT

Douglas Rizzo is training coordinator at Doosan Infracore America Machine Tools.


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