How to Avoid Breaking Cutters
Broken cutters are one of the more frequent challenges of working with CNC machines at both beginner and advanced levels. Once a cutter tool becomes broken, it is rendered totally unusable. Because cutters are very instrumental in milling operations, the cost of replacement can be very high. If you experience frequent breakage with your tools, replacing your cutter on every project will significantly increase the cost of the operations.
Broken cutters may be caused by three broad categories of issues. First, breakage might occur as a result of software and programming problems. It may also be hardware related (material and tool), which is more common or due to a lack of maintenance. Today’s article takes a look at the most common causes of broken cutters and how best to avoid it.
1 : Use the proper tool in the right conditions
Every tool has a shape and size. The selection of a tool for any milling operation should take consideration of the material to be milled, the size of the material, the cutter diameter and cutter geometry. Using the wrong cutter will often lead to repetitive work before attaining the final piece. This repetitive effort will also put an extra stress on the tool which may result in tool breakage.
As a rule of thumb, try to always approach your material with the biggest cutter diameter that will achieve your desired geometry with the least effort. Doing this will allow you to complete your job using a tool that is tougher, faster and less likely to break during operations. Another thing to keep in mind is the length of your cutting tool. At every instance, try to use the shortest possible cutter to lower the chances of breaking cutters as longer tools are more prone to breaking from torque and vibration.
Another thing to consider is the number of flutes in your cutter. Flutes are the deep helical grooves that run up the cutter. The tooth of the flute is what chips away at the material. The higher the number of flutes, the faster the milling operation. However, more flutes may also lead to tool breakage because of the heat that may be generated by more flutes during milling. The key is to find the ideal tool with just enough flutes to get the job done efficiently.
Finally, avoid frequent tool runouts when milling your job. A tool runout is said to occur when a cutting tool, spindle or holder spins off its axis. This runout, when milling will occur from time to time due to inconsistencies in the speed and accuracy. However, frequent tool runout will inevitably lead to tool breakage.
2 : Understand the material
You should have a fair understand of the material to be milled to prevent breaking your cutter tools by milling at the wrong speed and feeds. A good way to think about it is to always assume that the material to be milled is stronger than your cutter tool. Doing this will help you manage the feed rate and speed to help you get through the material with a lower risk of broken cutters.
Another serious area that requires attention is the material stability and holding during milling. An imbalanced and unstable material can cause all sorts of problems for both the material, tool and machine. For one, you could have a broken tool. You might also lose the geometry and shape you’ve been trying to mill the material. In extreme cases, you could damage some parts of your machine or even have someone injured by a falling or flying workpiece.
Lastly, try to perfect your start point and entry into the material when beginning your project. Position your tool to get the cut set at the best entry possible to prevent tool breaking from rough or forced entries.
3 : Perfect your running parameters
Now to the software aspect – Feed and Speed rates.
The feed rate simply refers to the amount of material that is fed to the cutting tool at any point during the milling operation. Feed rates depend on the material type, hardness, tool diameter, number of flutes and cutting speed.
A feed rate too fast will result in the cutter tool having to mill through too much material. As the pressure increases, the tool will accumulate heat and fatigue, inevitably resulting in a breakage.
The key is to find the perfect balance between slow and fast as using a feed rate too slow will also result in a significantly longer job time, effort and cost. Slower feed rates will also cause the cutting to be rough and less accurate. As you begin to work, monitor your feed rates and know when to lower or increase the rate of work.
4 : Cleaning and Maintenance
As milling is a continuous operation that involves the removal of materials from a workpiece, it is not unusual to have material shavings all around the place. In order to ensure steady functioning of your machine and cutter, clear these shavings immediately every milling or engraving operation is completed.
Material shavings will lead to inconsistent finishes on your workpiece at the very least. It can cause prevent new chips from coming into or out of your cutter or even worse, it may cause chips to become stuck between the material and the cutter. This will often result in chip breakage.
Depending on the volume of work being done, you may decide to clear all material chips and shavings at the end of the job or occasionally during the job.
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