CNC router cut quality depends on several factors, ranging from drive systems, vibration control, tooling, and dust removal. Although this is not a comprehensive list, these are important factors in making superior cuts when processing plastics and similar materials. Getting the cuts correct on the first attempt saves time, effort, and materials.
The heart of a CNC router is its tooling, and the tooling is determined by the nature of the job and the materials.
By selecting a tool that has the shortest overall length, will guarantee that the tool is as rigid as can be. Maintaining a level of rigidity ensures the operator of high performance. When running at 24,000+ rpm, any imbalance in the spindle or its bearings will become immediately apparent. Marks will be left on the workpiece. Often times operators will attempt to save money by using less expensive spindles. But these spindles can introduce vibration and affect the quality of the finished cuts. In most cases, consulting the manufacturer’s recommendations will give the best specification for the spindle for your CNC router. If you are still unsure, consult with the manufacturer’s rep. They know their tools and their capabilities.
Some manufacturers recommend spindles rated at even higher RPMs— 40,000. Spindles at this specification are more expensive, but they offer better cutting performance and higher operational speeds. Spindles operating at this speed can sometimes require additional cooling. Good mounting systems are also critical to secure the tool for precise cutting.
Alignment in the shanks is critical. Improperly setting the collet can damage the tool or shorten its lifespan. It is recommended that the shank fill at least 75% of the internal diameter of the collet.
One consideration that is sometimes overlooked is the tool diameter and the thickness of the material. Tool deflection is an issue caused by the resistance of the tool to the material. Because the cutter is rotating, it doesn’t want to move along the same straight path required by the tool. This can sometimes be minimized by choosing a tool with a larger diameter, but it is more dependent upon the material being cut.
Vibration was briefly discussed earlier, but it really deserves some elaboration. Vibration is not a friend to the CNC operator. It can damage the tool and the material being cut. With rotational speeds exceeding 24,000 RPMs the effects of vibrations are quickly seen along the edge of the cut. The source of the vibration can come from the drive systems, the spindles, or even in the way motion is generated by the machine. Because tolerance is such a delicate balance, it is challenging to eliminate all vibration. But with most things, a well-designed and constructed machine can go along way to reducing the effects of vibration. Solid mounting brackets are very important, as too are high-quality machine mounts.
However, when cutting thin, flexible plastics, the recommended cutter is a single flute, downcut spiral one that pushes the material down onto the bed and prevents movement and poor quality of the cut edge.
Quality cuts also depend upon efficient dust and debris removal during and after a cut is made. If debris is not quickly removed, it can become trapped in the cut. When this happens, the tool’s cutting flutes can become clogged resulting in additional friction which can sometimes damage the tool. Regardless, a build-up of debris is guaranteed to create poor quality cuts. It is generally recommended that when cutting plastics that a single flute, uncut spiral cutter be used as it better ejects debris. It makes clean cuts and reduces heat build-up. However, when cutting thin or flexible plastics, the recommended cutter is a single flute, downcut spiral. This will push the material down onto the bed and prevents movement which might affect the quality of the cut edge.
When these tools are combined with a well-designed pressure foot which, when used correctly, will generate a cyclonic vortex which sucks the waste from the cut as quickly as possible, in effect, much like a tornado, the debris is extracted from the cutting surface upward into the vacuum system. These systems help keep the work area cleaner. Dust removal is also vital in keeping the workplace safe and healthy for employees. It also directly reduces labor costs by reducing cleanup time which means employees can focus on projects.
Quality cuts don’t happen by accident. CNC routers are sophisticated machines that require maintaining operational specifications. Proper tool selection for the type of material being cut, controlling vibration, and debris extraction are critical for making high-quality cuts. When working with unfamiliar materials or tools, always consider consulting with the manufacture of the equipment for guidance. It is very likely they have already had experience working with the materials in your project.