CNC Machines – The Ultimate List Of Dos & Don'ts

CNC Machine Tools are essential work tools in today’s modern manufacturing environment. The constant demands for higher production speed, ever changing parts with increased complexity and the focus to consistent product quality mandate that your CNC machines stay in tip-top condition to meet or exceed these requirements.

 

Here are some tips that will help you to get the most value out of your CNC machines over a prolonged period of time.

#1 Setup

Prepare and place fixtures, tools and materials near your CNC machines to reduce setup time and keep changeovers as simple as possible. If space does not allow you to do so beside or near your machines, you should allocate a specific location for the preparation work within your facilities. This will ensure that focused preparation and everything you need to do the job is readily available.

 

Don’t create complex setup processes, if possible, as they may result in unnecessary downtime and errors. Many manufacturers work with specialized fixtures that are expensive and take time to design and make. These are useful for one particular operation and possible for one particular part only. If the need for such specific parts and the required operation increase, the responsible managers should consider and recommend the purchase of a 5-Axis Machining Centre instead—this will save you expensive fixtures and time, energy and over the long-run—money.

#2 Accuracy

Do understand the components used in your CNC machines. A machine with a linear drive system is certainly modern and attractive; however, such systems are also more sensitive and expensive. While they may help your machines to achieve slightly better tolerance, they are preferably used in a better machining environment. Why not consider modern machines with good overall mechanic, quality Ball Screws and Linear Roller Guides or Solid Box Guideways? Hardened, grinned and hand-scraped to perfection, they are perfectly capable and proven of delivering long-term accuracy and stability.

 

Beyond having a good mechanical structure and high-quality components in your CNC machines, do pay attention to the environment in which the machines are operating. This is widely left out and ignored but very important.

 

Don’t place your CNC machines near a heat or cooling source (for example, an air-conditioner blowing directly onto your machines). A gate left open near your CNC machines may also disturb the mechanics in the same way as the colder or warmer temperatures of air entering your workshop could negatively influence machine performance. In short, ensure good air circulation at all times.

Similarly, positioning your CNC machines above a drainage or cable duct is not advisable either as it might potentially create vibrations during machining. Keep to the recommended temperature of around 25 degrees Celsius, and maintain a constant and stable temperature within your workshop.

#3 Tolerance

Do ensure stable temperature in the workshop as fluctuating and changing temperature can affect tolerances. To supply clean air to your CNC machines; your air compressor should not be located too far away and should provide clean and dry filtered air.

 

Air is used by CNC Machining Centres to clean the spindle and tool taper during tool change, provide air for the Air-Oil lubrication system at the spindle (if available), clear the tool measuring system and operate inside Linear Glass Scales (if available) to protect your expensive glass scale from external pollutants. (Constant positive air pressure from inside to outside), a similar system is used at your machine spindle nose, positive air pressure from inside – out is avoiding, that coolant or dirt enters your spindle during machining.

 

Don’t place your CNC machines near foundry, stamping, welding or grinding machines. Dust in any form or shock waves created by presses, stamping or electrical variations and fluctuations should also be strictly avoided.

#4 Surface Finish

Do use the right feeds and speed during part machining. Note that these factors can affect the surface quality of your part or mold: Vibration caused by the CNC machine itself; tooling that are not sharp or unbalanced; tool holders that are not suitable or unbalanced; as well as influence from external sources to your machine (mentioned in the above point – dust or shock waves created by presses, stamping or electrical variations and fluctuations). These factors will not only reduce your tool life —they may potentially shorten the lifespan of your CNC machine spindle itself.

 

Don’t use worn out tools or already on the limit tools or too low a feed / speed setting as these can cause burnt marks on the workpieces. Likewise, avoid using the same tool for roughing and finishing if your surface quality needs to be good. Check that your part is clamped, rigid and stable. If you use fixtures, ensure that the fixture supports the part properly.

#5 Cutting Tools

Do choose the right cutting tools and start with the recommended cutting settings to achieve high quality surface and finishing. If your operator is experienced, he will know what is required to achieve the best result.

 

Don’t use blunt tools, wrong (dimension) tools or tools that are not suitable for the materials used as these can cause rough edges, cutter marks, raised marks or burn marks on the finishes. Or simply result in poor performance.

#6 Coolant

Do check the coolant regularly to ensure that the right amount and mixture used are suitable for the continuous operation of your machine.

 

Don’t use coolant which is high in concentration as this can cause machine damage and components to rust or corrode. Additionally, it can affect the health of your operator. Please consult your machine and coolant supplier to recommend a suitable water-based mixture for your machining and manufacturing needs.

#7 Lubricant

Do check regularly and use the right recommended lubricant for your CNC machines. Check your machine manuals for the appropriate oil type, brand and viscosity. In the long run, using the right lubricant will keep your machine operating at maximum performance. The correct lubricant used for the internal components of the CNC machines can also help you to maximize your machine health and performance, especially this of the machine spindle.

 

Don’t use lubricants that are cheap and not recommended by the machine supplier. Do not forget to check the properties of the lubricant to ensure that it is compatible with the machine and internal machine components like seals, hoses, and other parts. Caring for your CNC machine is similar to caring for your car and the car’s engine. If the wrong lubricants are used, it will not only result in voided warranties but result in repair costs for you.

#8 Overheating

Do stay within the spindle load recommendation to avoid overheating the spindle and spindle motor. Change filters regularly and check that the compressed air is kept clean and dry to avoid contamination from water and dirt. An overheated spindle could result simply from having a choked air filter at the spindle motor or the spindle cooling system. Replace the filter and renew oil regularly for your spindle lubrication systems. 

Note: this is valid for Air-Oil and also for Oil Jet spindles.

 

Don’t use a spindle with greased lubrication for extensive machining at full RPM, not longer than a few (10) minutes is recommended as doing so will cause overheating. Grease lubrication systems are closed up systems where no fresh grease is coming in to replace used up grease or in worse – burnt out grease. In case of overheating, the grease will eventually lose its lubrication effect and burn, resulting in spindle bearing failures and extensive machine downtime as well as high cost. It is necessary to allow the spindle to cool down after being used at maximum speeds, and to run it at lower RPM for some time. Doing so helps to prolong the lifespan of the spindle. Air-Oil Spindles can run at maximum RPM for a longer period of time (approximately 2 hours) compared to Grease lubricated versions. If you need longer running time, it is better to run them at 80% of their maximum RPM range or allow operation time at lower speeds in between. Only an Oil-Jet Lubrication system provides the guarantee to run your spindle at maximum RPM for 24h or longer if needed.

#9 Crashes

#10 Chucks & Fixtures

Do ensure that your work pieces are securely clamped. Ensure that the chucks used at turning machines are not only cleaned (do not use an air-gun to do so out of convenience) but also maintained and greased on a regular basis. This helps to maintain the efficiency and operating features of the chucks. Check with either the CNC machine manufacturer who supplied the CNC machine and chuck, or directly with the chuck manufacturer for recommendations on the maintenance, greasing intervals and type of grease to be used.

 

Don’t use an air-gun to clean the machine or machine parts inside your CNC machines. This will result in small dirt, chips and possibly coolant to be blown straight into the system—these affects the functionality and safety of the equipment and CNC machines in the long run. Lathe hydraulic or manual chucks, machine spindle nose, guideway covers and underneath guideways, linear glass scales, ATC mechanism – all of these can be affected due to the extensive usage of air-guns.

#11 Programmers

Do invest adequately in experienced programmers and various ways in programming as operations of CNC machines are controlled by CNC controls.

 

Don’t attempt to operate highly sophisticated CNC machines if there is a lack of knowledge. For example, without appropriate knowledge, G and M codes set up or data input may be set up wrongly—such errors can cause multiple and expensive problems right at the start of your cutting processes.

#12 Operators

Do hire the right machine operators and continue to upgrade their skills and knowledge to optimize the yield of your machine tools. As these machines are expensive investments, you should ensure that they are handled and operated correctly.

 

Don’t immediately deploy machine operators to any CNC machine that they are unfamiliar with, even if they have some prior machining experience. Wherever possible, allow them sufficient time to familiarize themselves with your CNC machine tool before hitting the Start button.

#13 Automation

Do take advantage of automation solutions, especially during this current challenging environment. Check out the various options available to increase your production efficiency and diversify your product offerings. Low Mix – High Volume or High Mix – Low Volume, there are solutions available. Reduce manpower and rely on more knowledgeable engineers.

 

Don’t jeopardize your production and delivery schedule by eschewing all automation options. Discuss your needs with the DiPaolo Machine Tools team  to find out which automation system makes the most sense for your production needs.

 

Remember, the cheapest solution is not necessarily the best way to make more money; conversely, the most expensive option may not be the right solution either. To change supplier is also not necessary – provided they are professional and have a comprehensive line of machines and solutions in hand for you.

 

#14 Maintenance

 

Do follow a detailed maintenance schedule and conduct regular checks to ensure maximum levels of performance and uptime of your CNC machines. Regular maintenance on your CNC machines is a crucial factor in running a successful machining workshop.

 

Don’t let dirt, materials and debris accumulate as these can result in damage and inaccuracies in your parts machining, costing you downtime and losses incurred in expensive repairs. Ensure that your operators treat your CNC machines well as they are your investments to generate revenue.

#15 Safety

In manufacturing, production downtimes and costly repairs often result in loss of revenue. These will be damaging for your bottom line if producing top quality products and quick delivery is your niche to stay competitive.

 

Understanding how your CNC machines and their functions can equip you better with the best practices and knowledge to improve your factory’s operational efficiency, increase revenue, and prevent unnecessary problems from occurring.