9 CNC machine failures and troubleshooting tips

by | Jul 22, 2022

If you’re running CNC machining service, then you know that occasional failures are just part of the game.Luckily, many of these failures are easy to troubleshoot if you know where to look.

In this article, we’ll take a look at 9 common CNC machine failures and how to fix them.We’ll also discuss some general troubleshooting tips that can help you solve issues. So whether you’re just getting started with CNC machining or you’ve been using them for years, be sure to read on for some helpful tips!

Some of the most obvious errors are wrong tooling and incorrect machining settings chosen. The instant consequence you may observe are rough edges, metal shavings, and cutter marks. Quick note: tool wear may lead to similar results as well. 

CNC cutting tool

Solution:

The right corrective action here is to examine the cutting tools in use and find out if there are visible defects. The good idea is to verify the tool’s characteristics against a material’s properties and find out if they match. Revolutions per minute (RPM), feed rate, coolant flow, and other settings should be revised as well. 

Programming Errors

It’s safe to say that CNC machines are sophisticated pieces of machinery that require absolutely precise execution commands. A single G or M-code error in a CNC file instantly results in a result that does not comply with technical requirements.

CNC Programming examples

Solution:

There are two ways in which this trouble should be approached: fully-fledged rapid prototyping practices in place and proper training for operators.

Sitting in their control cabinet, an employee has very restricted control over the machining process. Yet, they can always spot the problem and manually fix an incorrect G or M code command.

On the other hand, rapid prototyping serves the purpose of making impeccable CNC files with zero errors. If there are some related issues, the approach to rapid prototyping should be revised. 

Poor CNC Machine Tool Maintenance

Unfortunately, even the best tooling does not live through more than a few months of constant work. Cutters slowly deteriorate while removing the material of a workpiece. Unremoved dirt, sand, lubricant, and metal dust only add to tool wear. This effect typically leads to poor fabrication quality and machine failure, eventually.

Solution:

The best you can do about it is to follow the maintenance regime for all the machine tools in use. It includes checking coolant level and air filter integrity, sharpness, absence of visible defects, and so on. 

Incompetent Workers and Lack of Training

Machine operators, engineers, programmers, and other labor involved playing a crucial role in the machining process. The variation between the levels of knowledge and skills between employees of the same rank is of equal importance. Without the right machining skills and programming skills, you workers are just unable to optimize the yield.

CNC machining worker

Solution:

The best corrective action here is to ensure that absolutely every worker receives appropriate training.

It’s not necessarily that you should conduct such events yourself. There are sufficient facilities that familiarize workers with technology advancements and train them to select the correct tools, write the programs, and more.

Issues With the Power Supply

On some rare occasions, you may face a sudden stop of an entire machining line. Alternatively, a CNC unit’s display may turn on and off uncontrollably. These are other similar problems that clearly indicated the issue with a stable power supply. 

Solution:

The recommendation here is to let an electrician do their job. It may include examining input and output wires, checking the voltage, finding blown fuses if there are any, rebooting the CNC unit, etc. 

Another tip is to add checks of wires and fuses to your routine support and maintenance procedure and conduct it regularly. 

Problems With Automatic Tool Changer

Normally, automatic tool changers in CNC units are the last part to fail. Yet, occasionally you may observe machines struggling to switch tools in the required tempo, which leads to setbacks on the production line.

Solution:

You should approach the issue by checking the base, the gripper arm, support arm, tool holder, and tool magazines of a tool changer. Try to find out what part exactly malfunctions, and then give it a good cleaning and lubrication, repairment, if necessary, or replacement.

Machine Vibration or Chatter

Tool chatter, more commonly known as vibration, is the movement between the workpiece and tooling. It instantly leads to waves onto the machined surface and compromised machining quality. It also conceives loud noise that interferes with employees’ normal workflow and endangers labor. 

CNC Machine Tool Vibration

Solution:

The recommended corrective action is to examine both the workpiece and a cutting tool. One of them or both may have defects. Besides, it’s frequent, in the machining process, that some RPMs make tooling resonate. If that’s the case, just adjust the settings slightly. 

Another tip is to use balanced tool holders while utilizing spindle speeds of more than 8,000 RPMs. Such machining solutions sope with increased speeds way better. 

Machine Tool Overheating

CNC machines usually run constantly since every hour of their time has a price. Yet, when tooling cuts the metal at high spindle speeds for a prolonged time, some overheating seems to be unavoidable. For reference: temperatures of 150°C or above are considered deteriorating for nearly every CNC machine tool. 

Solution:

The corrective action here is to use appropriate coolants and lubricants. Oil-jet or Air-Oil lubrication spindles are considered optimal. Variations in environment temperature in the workshop are also of no good. 

Besides, you should consider choosing optimal values of spindle speed of rotation. Higher than necessary RMPs cause an adverse impact on fabrication quality in multiple ways. See what lubricating of the CNC machine may look like in the image below.

Clamping/ Unclamping Problem of Chucks and Fixtures

It’s a complex issue resulting in the impossibility of securely gripping a workpiece in the chuck. If that’s the case, a workpiece starts shifting or vibrating and may even fall out of the chuck. 

CNC machine fixture

Solution:

Consider following these steps to resolve the issue:

  1. Check the positioning of a workpiece.
  2. Check the hydraulic pump integrity and hydraulic pressure level.
  3. Check if the jaws are set correctly, and you use surface gripping instead of point gripping.
  4. Check the integrity of the foot switch and if the contacts are still working.
  5. Check if there is enough lubricant for the parts of the chuck.
  6. Check if the chuck has an appropriate M-code command control.
  7. Check the output of the solenoid. 
  8. Check the integrity of the draw tube connecting the hydraulic cylinder and the chuck.

Make sure that the machine is disconnected from the power grid before performing any of the detailed steps. 

Summary

Although there are many potential causes for CNC machine failures, the most common ones can be easily identified and troubleshot.

By being aware of these problems and their solutions, you can minimize downtime and keep your CNC machines running smoothly.

Have you experienced any of these issues with your CNC machines? What steps did you take to fix them? Let us know in the comments here.

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