The introduction of CNC machining has revolutionized the way our industry processes goods.
The dependency on human labor has been reduced to half, with computers taking their place. As a result, we are able to witness an increased efficiency, improved product quality and the ability to produce almost everything with exact precision- 3D, 4D or 5D.
But then again, it’s a computer system directing actual ‘CNC machines’ to perform a task. Tool wear is as common as it gets. It may experience a breakdown or failure after working for an extended period of time. In fact, every cutting tool will experience wear at some point in its production life.
While it might be common, excessive wearing is not good for our product or machine. The inconsistencies caused by such wears and tears may have unwanted effects on your workpiece and may do damages to the primary piece of equipment. Its failure might even lead to irreplaceable damages such as rework, a collection of scrapped parts, or a total breakdown which might cost us more than the product itself.
Thus, it’s pretty important to find out such abnormalities and correct them in real-time so we get optimal end mill performance. Here’s our take on the various types of tool wear, and how to identify and mitigate them, complied with our experience. Hope they will help you manage tool wear better!
Abrasive Wear
Mechanical stress is one of the major causes of tool wear with thermal taking a close second place.
Abrasion, especially the wear land abrasion, is pretty common amongst cutting tools. It is caused by the uniform abrasion on the cutting edge of the tool, dulling the edge as a result. If severe like added thermal stress at higher speeds, it can even alter the dimensions of the tool edge. This is why a tool coating is of utmost importance for tool longevity.
How to Avoid
If you start witnessing a certain abrasion pattern on your tool’s edges, it’s time for you to reduce the cutting speed and optimize coolant usage, especially when working with this particular tool. Even High-Efficiency Milling (HEM) tool paths can be used to reduce wear by distributing the work done across the entire length of the cut. This helps focused abrasion while contributing to the longevity of the tool life.
Thermal Cracking
Thermal cracks are caused by temperature fluctuations during a milling process. They are identified as a series of cracks on the tool’s surface perpendicular to the cutting edge. Such cracks form over a long period of time and are often the most difficult to deal with once present.
How to Avoid
One of the best ways to divert thermal cracking is to add a proper heat-resistant coating to the end mill. Similar to abrasion wear, HEM tool paths can also be utilized for an even distribution of the head across the tool, thus reducing the heat on a certain area.
Fracture
Fracture, as the name suggests, refers to the sudden breakage of a tool during a machine operation. It, of course, results in improper speeds and feeds, and incorrect coating, thus spoiling the product or part in hand altogether.
Such fracture cases aren’t restricted to abrasion or wear only. A loose handle, inconsistent workpiece, incompetent materials, or other tool holder issues can cause them too.
How to Avoid
You may go ahead and adjust the speed, feed and depth of the cut to keep the tool fracture at bay. Checking the machine set up of appropriate rigidity and optimizing coolant usage can also help reduce fracturing.
Chipping
Chipping is caused by a number of different reasons such as excessive shock-loading during operation, thermal cracking or abrasion. It can be seen as a series of chips or flaked bits on the cutting tool. This type of wear often leads to a poor surface finish and may even cause a severe tool failure if not corrected in time.
How to Avoid
There are several steps to check whether your cutting tool is experiencing chipping or not. First, you need to ensure your CNC milling machine is free of vibration or chatter. Then adjust your speeds and feeds accordingly, increase the speed and reduce the feed rate.