Mechanical Knowledge

8 Common CNC Machine Problems

Based on our experience, most of the problems faced by mechanics when using CNC lathes, milling machines and multi-axis machining centers revolve around four main issues.

1. Using Cutting Tools / Settings wrongly

Choosing the wrong cutting tool can often result in poor quality material finishes. This can be seen as rough edges, cutter marks on the surface, raised marks or burn marks on the edges or corners of the material. This error may cause extensive tool wear.

Poor finish of the material may be due to the tool being too blunt or the feed rate ratio is incorrect. It may also be caused by the wrong size of the tool in hand in terms of size, quality or matching with the material.

To solve this problem, it is important to choose the right tools and settings for the work and materials.

2. Programming error

As a highly complex device controlled by a CNC computer, many problems that arise in CNC machining usually come from programming. These may be due to lack of understanding of the different codes used by the controller, setting errors or entering wrong data variables into the CNC controller.

In order to resolve these errors, it is important to fully train new operators in different ways of programming CNC machine tools. The machine supplier or experienced operator should provide the new operator with comprehensive user manuals and training, motion sequences, and machine operation.

CNC machine tool-desheng precision

3. CNC machine tool is poorly maintained

Modern machinery has many moving mechanical parts, so the CNC machine tool needs to be cleaned and maintained regularly to keep it in optimal operating condition.

Failure to remove dust, materials and other debris may cause accumulation, and over time may result in inaccurate processing or even machine failure.

To prevent this, it is essential for machine operators to follow the detailed maintenance system of the machine tool used. They should also regularly check the level of coolant or air flow, such as air filters, to ensure continuous and uninterrupted operation.

Note: Overheating of the spindle may be due to clogged air filters in the cooling system.

4. Inadequate worker skills and training

With the increasing use of computing and programming, today's CNC machine tool operators require a different set of knowledge and skills. Without proper organization, planning and programming skills, even if previous machine models have been used in the past, workers cannot optimize the output of these machines.

To ensure that this problem is solved, you need to hire the right machine operators who can visualize and design the machining process, choose the correct tools and job sequence, and write programs.

CNC machine tool-desheng precision

5. Clamping and loosening of chucks and fixtures

This can be a major problem when the workpiece to be processed cannot be grasped firmly by the chuck, or when displacement or vibration occurs during processing. To resolve this issue, consider the following steps:

1). Check whether the position of the parts is correct to ensure a firm clamping.

2). Check whether the hydraulic pump and hydraulic pressure are set correctly.

3). Check whether the installation position of the jaws used is correct and is sufficient to hold the material. Ensure a wider surface grip, not point grip.

4). If the chuck cannot be opened/closed, please check whether the foot switch is working normally-check whether the contact is still working and whether the wire is disconnected.

5). Check whether the lubricant is suitable for different parts of the chuck, and there is no dust or debris affecting the movement.

6). Check whether the chuck is working normally according to the MDI M-code command.

7). Check if the solenoid output is working properly. If so, disconnection at the connector may be a problem.

8). Check whether the pull pipe connecting the hydraulic cylinder and the chuck is working and whether it is loose.

Note: Improper clamping of machine parts can lead to accidents, damage or more serious consequences – operator injury! Therefore, it is essential that the parts must be properly clamped by the machine tool.

6. Automatic tool change

Sometimes, you may face challenges when using automatic tool changers in CNC machine tools. This can be solved by learning each step of the tool replacement process and troubleshooting it by diagnosing the problem.

Check that the base, gripper arm, tool holder, support arm and tool magazine are working properly. Or check the movements of the rotating arm and the mechanical arm to ensure that they are working properly. Also keep the automatic tool changer and tool holder free of chips and coolant.

7. Machine vibration/flutter

When your CNC machine vibrates during work, it may greatly shorten the life of the tool, affect the durability of the CNC machine or damage the quality of the processed parts. You can only detect this by listening to the noise generated – sometimes the sound may be loud!

To solve this problem, you need to diagnose whether the workpiece vibrates or the tool vibrates. You can also adjust the RPM of the machining process so that the frequency of the machining process does not resonate with the material frequency.

Note: For machining centers, when the spindle speed is higher than 8,000 rpm, a balanced tool holder must be used. Otherwise, vibration marks first appear on the machined parts. The ensuing is to shorten the life of the tool, and finally the failure of the spindle bearing.

8. Machine overheated

For high-volume and long-term processing, overheating may sometimes occur. Your CNC machine tool temperature may reach 150 degrees or higher. This may have a negative impact on your machining work, the tools used and the CNC machine itself.

To avoid this, make sure to clean all channels and clean the machine regularly so that it is free of dust, dirt and materials. Clean all metal shavings and liquid used in cutting regularly.

The overheating of the machine tool spindle is mainly caused by a large amount of use at the highest speed. Grease-lubricated spindles cannot be used at full speed for a long time. Spindles lubricated with air oil are better, and like the oil-lubricated spindles used by Huachuan, they can run for long periods of time even at maximum rpm.

Changes in the ambient temperature of the workshop will also affect the overheating of the machine. Wind/air passing through doors or open windows can affect the precision of precision machine tools.

The wide windows allow the sun to shine freely, with air-conditioning, which can give your operators a pleasant feeling, but your machine can't enjoy it at all, because its entire shaft is deformed.

CNC machine tool-desheng precision

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