Milling machines. Common problems, measurement solutions

Having familiarized ourselves with milling machines, understanding how they work and the roles they perform, let’s look at the sort of problems that can occur during their operation. If you’re a manufacturer reliant on milling machines, being aware of these will put you in position to head off issues. Doing so is vital to maintaining your machine’s efficiency and ensuring the quality of the machined parts they’re responsible for producing.

Common problems in milling machines

Unsurprisingly given their relative complexity, milling machines can encounter a variety of problems, perhaps the ten most common of which are as follows:

1.      Tool wear

As you might expect, over time cutting tools wear down as they continually come into contact with workpiece material. When this happens, accuracy and surface finish will be compromised. Therefore, regular tool inspection and replacement are necessary to maintain performance.

2.      Chatter

“Chatter” is the undesirable vibration of machine parts that can occur during milling. It has much the same effect as tool wear: reduced accuracy and poor surface finish. Chatter can have many causes ranging from selection of the wrong tool, setting the wrong cutting parameters, or an insufficiently rigid machine setup.

3.      Poor surface finish

This can be caused mainly by incorrect tool geometry, erroneous cutting speeds and feeds, or the use of worn-down tools with the result that machined parts end up with poor surface finishes.

4.      Inaccurate dimensions

Issues in areas like tool deflection, machine misalignment, and incorrect programming are the causes of inaccurate dimensions. Regular calibration and proper set-up are the keys to resolving issues in this area.

5.      Overheating

Milling machines, operating at high speed, generate excessive heat and that can lead to both tool and workpiece damage when inadequate cooling, incorrect cutting speeds, improper lubrication and other issues are present.

6.      Chip formation problems

The process of milling results in the creation of material chips (milled away from the workpiece) which can then jam the machine if the cutting parameters aren’t optimized to account for the material being processed. Without adequate chip evacuation, tool damage follows, and machine accuracy is compromised.

7.      Broken tools

Factors like excessive cutting force, poor tool handling, or using a worn-out tool can lead to sudden tool breakage so monitoring tool condition and usage parameters is vital to prevent problems in this area.

8.      Rigidity and alignment

If a milling machine isn’t rigid enough or its component parts are misaligned, accuracy and repeatability decrease. Again, maintenance and alignment are the way to guarantee continually optimal performance.

9.      Spindle problems

Spindles present issues like excessive runout and bearing wear both of which impact accuracy and surface finish. So regular spindle monitoring and maintenance are critical.

10. Errors in programming

Most milling machines today depend on complex software, so errors and bugs in their code can lead to machining inaccuracies and parts defects. Here, carefully validating and simulating CNC programs before running them on the machine can identify and correct potential errors.

What we can immediately see is that in a multi-part milling machine responsible for a high degree of accuracy in its output, quite a lot can go wrong!  So, keeping milling machines in optimal condition through a combination of proper machine maintenance, tool selection, cutting parameter optimization, and operator training is vital. Regular inspections, preventive maintenance, and adherence to best practices all contribute to solving potential problems, and the role of measurement here is absolutely central.

Measurement matters

Think about why! Almost all the problems identified above relate to issues of “accuracy” (calibration, alignment, correct geometry, etc.) From this perspective the role of measurement in addressing the problems we’ve identified will obviously be central.  For example, one focus area should be improving and maintaining the quality of the cutting surfaces that are used to remove material. This can best be achieved by using a camera-based measurement system, which takes measurements using cameras inside the actual milling machine – so data is captured in situ.

How does camera-based measurement help to head-off or resolve other issues like those we’ve identified above? There are plenty of examples. For one, tools may not be quite as precise claimed and as a result, they may overcut (remove too much) or undercut (leave too much) too much material from the workpiece. Only through accurate measurement can such an issue be identified, before the milling process even begins.

Then, during production a variety of issues can arise. Traditionally, laser measurements have been used to detect these anomalies but while lasers are generally accurate, their measurements are not taken in situ. Rather, they are taken before a milling process is initiated or after it has been completed. If you can measure during the process (as you can with a camera-based, in-machine system), you can understand wear and make adjustments literally on the fly because you can really see if tolerances can be enhanced and compensate for any issues.

Leading the way in camera-based measurement

In camera-based measurement systems one company, Conoptica, leads the way. Conoptica provides real-time feedback, in an automated manner – which means its operations can be adjusted via closed loops. That’s because the camera-based system is inside the machine and functions while the workpiece or tool is in situ. Only the camera-based system thus captures data that provides records for comparison and quality assurance in near real time.

The importance of this can’t be overstated. Milling is an industry that supports high volume output, with machines being used in factories and large-scale production facilities where, often, margins can be very low. This reality underlines exactly why measurement, which ensures optimal output accuracy, is so vital.

Furthermore, with margins tight, it can also pay to ensure accuracy of the tools (blades and cutting surfaces), so that end quality is enhanced. As a result, for the manufacturer camera-based measurement literally provides a competitive advantage. Of course, we also want to reduce unnecessary waste to ensure sustainable (and cost-effective) production.

Given the range of challenges that milling machines can present and the importance of a high-quality product, manufacturers who use milling machines should quickly grasp the importance of camera-based measurement both to the quality of their manufacturing outcomes and, equally, to their bottom lines.

About Conoptica

Conoptica is the market leader for measurement equipment in the wire & cable industry and has been providing high tech camera-based measurement solutions for the metal working industry since the 1993. We make sure that the metal working industry has access to key quantitative data about their products and tools.