A crash in a CNC Machine Tool like a 5-Axis Machining Centre may not be as horrific as a road accident. However, it can be disastrous to your manufacturing productivity and very costly to repair.
But what can you do when it happens to your 5-axis Machining Center? What steps can you take to minimise machine tool crashes and restore it quickly to operational health? In this article, you will learn the following:
- Causes of CNC machine tool crashes
- How crashes affect 3-Axis Vertical Machining Centres
- How crashes affect 5-Axis CNC machine tools
- Recalibrating 5-Axis machine tools
- Repairing 5-Axis CNC machine tools
- Using calibrating systems to reduce crashes
Causes of 5-Axis CNC Machine Tool Crashes
Available in many variations and configurations, 5-Axis machining centres have multiple moving parts. However, the source of these crashes is often due to human errors rather than machine errors.
These are some of the common causes of crashes:
- Setting of wrong tool inside the Automatic Tool Changer (ATC) tool pocket
- Input of wrong tool length when they are exchanged or newly set-up
- Setting the wrong feed rate (normally too fast for the job)
- Choosing the wrong tool for the job
- Setting the job wrongly
- Wrong reference point set
- Errors in CNC programming
- Poor maintenance of CNC machine
To minimise these and other common CNC machine problems, you should ensure that your machine operators and programmers are adequately trained. This is also important to avoid any injury to the operators.
Your machine tool operators and programmers should also be alert and experienced in how to troubleshoot crashes when they occur. Thus, careful testing before the start of your production is highly recommended.
How 3-Axis Vertical Machine Crashes Compares to 5-Axis Crashes
Before we dive into 5-axis machining centre crashes, you need to know that there is a big difference between a crash happening on a 3-axis vertical machine compared to a 5-axis version.
Now, why is that so?
Well, in a 3-axis vertical machining centre a crash normally happens in the vertical axis or Z-axis. The impact happens straight down and affects mainly the spindle – particularly the first row of spindle bearings which take the main force of such an impact.
If the spindle is not damaged (lucky you!), you should check for Z-axis alignment and spindle run-out, especially if there is a higher volume of noise heard when the machine operates at a higher RPM. You may also need to re-align the spindle head or frame if both settings move out of their original tolerance levels.
Regardless of the source of impact – be it vertical or side-wise – you’ll need to re-align the spindle head. In the case of vertical impact, the X and Y axes are usually not affected. Should the crash be severe, these axes may run out of their original tolerances.
The Complications in a 5-Axis CNC Machine Tool Crash
If the same impact scenario occurs on a 5-axis configured machining centre, however, the likelihood that more than one axis needs to be adjusted by service is high.
In a machine with a built-in two axis rotary table, a straight down impact in the Z-axis will not only affect the original Z-axis but the two rotational axes C and B. This is especially so if the rotational axis at the time of impact is positioned in a certain angle/degree.
Should the impact be more severe, even the Y & X axes can be affected. This will require a greater amount of rectification.
Machine Recalibration in 5-Axis Machining Centre Crash
A re-calibration is often the minimum measure needed to ensure that all 5-axis are in perfect alignment to each other after the incident. This will also reduce the possibility of misalignments, especially at the higher tolerances, when the part is being machined during production.
However, a simple calibration is often not enough after a crash. It is better that your operator checks all the different geometrical dimensions first before calibrating the machine.
Repairing a 5-Axis CNC Machine Tool Crash
Repairs of 5-axis machining centres tend to take more time. Repair costs are higher too, due to the need to carefully realign each axis and set them properly. Such work requires skilled engineers using highly precise tools.
It is strongly advised therefore that such work should be done by a well-trained factory service engineer who knows the intricacies of the machine and how to set it correctly.
In our experience, we have seen customers trying to cut cost by hiring inexperienced engineers to do the repair job. Often, the end result is a slipshod repair work which results in more issues. The end result is that they up pay more over the long-term when they try to cut costs.
Managing 5-Axis Machining Centre Crash Through Calibration
To minimise 5-axis machining centre crashes, Hwacheon recommends that you include the HRCC II system for every newly purchased 5-Axis Machining Center. HRCC II stands for: Hwacheon Rotation Centre Calibration System, which calibrates not only the rotational axis, but also the flatness of the table relative to the axis and the linear straight angles.
The system includes a high precision wireless measuring probe (Either a Blum or Renishaw), a reference steel or ceramic Ball with mounting bracket, plus a specially developed and designed software to operate and control it.
It can be easily used – all it takes is just 45-60 seconds to run the complete cycle.
We recommend that the calibration cycle should be run once a month, or every time prior to producing very accurate parts. This will minimize temperature affected variations and ensure that your machine accuracy is kept at its best.
Handling Measuring Equipment in a 5-Axis Machine
For machines with an AWC system (Automatic Workpiece Changer), such measuring calibration equipment can be mounted on a single pallet or a part mounting holder. They can be used as many times as required.
The wireless measuring probe will be kept in the machines’ ATC (Automatic Tool Changer Magazine) until it is called up for use. Meanwhile, the measuring probe can be deployed for workpiece / part referencing or measuring specific areas of the part.
Regardless of how severe or in what direction your machine tool crash happens (vertical or side wise), we strongly recommend that you contact your local available office or the service hotline of your machine manufacturer.
Users of 5-Axis CNC Machining Centres do not need to be afraid of crashes, so long as they pay special care and attention to maintaining them. If this is done well, 5-axis machining centres can open much wider manufacturing possibilities and enhance your company’s manufacturing effectiveness and bottom line.