More Options for CNC Machines

We focus our posts mainly on machine shops since we operate several multi-axis DMG Mori machines in our facility. We focus on high-precision parts manufacturing working mainly with aluminum. We also offer engraving which prompts this coverage of CNC applications on a variety of cutting and printing machines. One advantage of a CAD/CAM system is that it can store jobs for various machines and this can include those separate from milling and turning since it employs standard coding that can be applied to any automated process. The CNC term is most often used in reference to mechanical machining but there are many more options for CNC machines. We review several computer numerical control devices following.

CNC Basics

In understanding where CNC programming can be used it’s important to understand the basic principles of operation. We covered an overview of CNC machining hardware and automation. Let’s look at the functions of the CNC machine. In its simplest form, inputs, whether manual, semi-automatic, or automatic are received by a central processor or controller that sends commands to an electric motor. That motor moves arms and pulleys to position the tools along any number of axes with sensor feedback to perfectly calibrate the part location and tool position.

Milling and turning are very common applications for CNC machining but this basic premise of a brain, motor, and sensors can be employed for any number of processes to produce a part. Many don’t require the raw material to be clamped in place and others make quick work of cutting dense materials with ease. CNC machines can offer part manufacturing with these approaches:

EDM

An Electrical Discharge Machine (EDM), as its name implies discharges an electrical current creating extremely high temperatures that melt the targeted material. As with many inventions, the discovery of electrodes melting away from the spark created in an experiment was the first step in developing this process over 200 years ago. CNC technology controls the movement of the discharge to aim it precisely. Often with EDM machining, the raw material does not always need to be fastened securely since it receives no physical force applied to it.

The most common application is Wire EDM where the electrical discharge is sent through a fine wire (usually brass or copper) that cuts materials similar to the action of a bandsaw. Conductivity is controlled through the use of deionized water continually fed into the cutting path. Linear passes create straight edges and fairly smooth cuts but often need a second run at a lower speed to clean up edges.

Other types of EDM include Ram or Die Sinker, and Drill. The Ram requires a specific graphite piece to be precision formed to create a unique hole size. The graphite becomes the electrode that is directed to bore into the material. This is an expensive and often difficult process to control. The Drill uses a wire thread through a part to expand the size of a pre-drilled hole. This can be useful to fabricate round shapes in hard, conductive materials.

In most cases, an EDM application requires a pre-drilling by another machine to locate where the EDM process will begin. It can be used for large shapes, hard materials that may easily break other cutting tools, and for pieces with difficult geometries. EDM is used in the manufacture of jet engine turbines, tools and dies, metal stamping dies, and other conductive metal applications. Due to the timing of the electrical discharges, the positioning of the same, and the repetitive nature of this manufacturing method it can easily receive commands from a computer. Thus, the development of CNC EDM machines is in use in many manufacturing facilities.

Laser

Laser cutting is used extensively for engraving but also finds use in drilling precise holes and milling slots due to the intense focus of laser light on the raw material. Lasers are available for the hobbyist and are often a first entry into CNC programming for a shop transitioning to automated systems. Laser equipment is generally less expensive to purchase than mechanical CNC equipment. It is also less costly to use and maintain. Lasers provide shallower cuts but a high degree of accuracy for complicated shapes. One main factor in the low operating cost is the ability to cut through material in one pass. They are quieter and create less waste but do not offer the deeper and wider cutting capacity of mills or lathes and do produce toxic smoke from the melted materials requiring quality ventilation.

In laser cutting, a beam derived from a laser light source is directed with mirrors through a focusing lens and nozzle to direct concentrated thermal light that melts and removes material. The speed and focus of the beam dictates the size and depth of the cut. As with any CNC application, the focal length, the position of the nozzle, and the speed of movement are all controlled through computer input. A laser can cut many raw materials typical in CNC machining, like aluminum or steel but also offers quality work on softer materials like leather, paper, foam, and more.

Water Jets

Another subtractive process available offers a cleaner approach with no off-gassing or high temperatures but is powerful enough to cut a hole right through titanium. Water is forced at extremely high pressure (up to 420 MPa) through a small nozzle to deliver cutting power that is razor sharp. Initially, only 2D water jet machines were available but 3D and 4D models are now offering more options as well as a mixture of diamond or other sands in the water stream to further intensify the cutting capabilities.

The advantages of the cool application are the avoidance of any distortion of the raw material due to heat or friction. It is becoming quite well-known in both aerospace and military applications. Once again, the control of the water pressure and the direction and speed of the cutting path make a perfect application for CNC connectivity.

3D printing

A different approach to machining is the additive process of 3D printing. Our full comparison between the additive versus subtractive approach covers many aspects of this manufacturing method. This may best exemplify the CNC concept as we can easily picture a home or office printer receiving a print command and sending a print head back and forth across the page. 3D printing utilizes this same concept depositing heated material such as plastic or some metals at specific locations rather than ink. A new axis is introduced to allow the building of a form as the print head moves back and forth.

3D printing continues to advance in quality and applications and adds another option to the CNC family of manufacturing. It is best suited to prototypes and custom pieces such as medical devices and military but continues to expand due to intense fascination with its capabilities.

Computer Numerical Control

The term CNC can apply to a growing number of approaches to manufacturing beyond the typical mechanical machine operations it generally references. We, at Rapid Enterprises, are eager to learn and grow as more options for CNC machines become competitive in our precision marketplace. Contact us to find out how we can help guide your manufacturing journey.