edm machine in use

What is EDM Machining? A Beginner’s Guide

Although EDM (electrical discharge machining) is among the most recent metal processing methods, its earliest application began in the mid-1940s when it was used to remove broken taps and sheared-off bolts from valuable aluminum castings. Rapidly pulsing high-voltage electrical discharges (sparks) were passed across the gap between the electrode and the grounded workpiece, removing taps and bolts from the castings by erosion. Hardened taps were removed without force or extreme heat, leaving the castings unaffected.

On the heels of this simple drilling operation, the second element of EDM processing developed: ram EDM or sinker discharge machining. Essentially identical to EDM drilling, ram EDM added a complex form to the end of the “drill” electrode, allowing a finished and precise cavity shape to be “machined” in one action. A third EDM type soon followed. Wire-cut EDM uses a straight wire electrode to cut a vertical or angled slot, as the wire is slowly fed through the cut to maintain a new electrode at all times.

EDM in 2023

Manufacturers typically choose electrical discharge machining (EDM) when conventional machining methods cannot provide a solution. The EDM process uses thermal energy to burn away material from a workpiece to create the desired shape. Although it is not the most commonly-used CNC machining process, engineers turn to EDM whenever hard materials and complex shapes are not conducive to traditional machining.

EDM does not require or employ mechanical force for material removal. Instead, it uses a rapid sequence of electrical current discharges between electrode materials submerged in a dielectric fluid. The electrodes (one being the workpiece) are separated by a spark gap generating extreme electrothermal heat in the spark gap zone. The heat vaporizes portions of the workpiece surface, a process called spark erosion.

Let’s look at the EDM process in detail to discover its two main types, where it’s used, and what benefits it offers:

What are the Two Main Types of EDM Machines?

The two main types of EDM machines are Ram EDM and Wire EDM.

How Does Ram EDM Work?

Ram goes by several names, including conventional EDM, die-sinking EDM, sinker EDM, spark-eroding EDM, and cavity-type EDM. But no matter what you call the process, it works like this: An electrical potential difference is created between the electrode and workpiece, electrically conductive materials, and submerged in a dielectric fluid such as deionized water.

In the Ram method, a graphite electrode (cutting tool) is machined into the mirror image of the desired shape and “sunk” into the workpiece on the end of a vertical ram. A sinker EDM machine uses electric spark erosion to remove the metal, creating the angles and contours of the part or cavity. The dielectric fluid acts as an insulator until the process reaches a sufficiently high voltage.

The dielectric oil also works like a coolant, removing heat from the piece to prevent excessive thermal expansion. As the oil cycles through a filter, it removes the metal particles and continues through a chiller that keeps the oil below its flash point.

Ram EDM electrode tools, like graphite or copper, must display high melting and vaporization temperatures or high thermal conductivity. The tool materials must also show the ease of fabrication and wear resistance. Cost is another consideration when choosing the material for a tool electrode.

The following are essential factors determining the suitability of a material as an electrode tool in EDM machining:

  • Higher metal removal rate
  • Lower tool wear
  • High degree of electrical efficiency

Although any conductive material can be an electrode material, taking into account the factors and properties for better application in EDM, graphite has been the most popular tool material. It exhibits a relatively low wear rate with a higher degree of electrical efficiency and is inexpensive and easy to fabricate.

How Does Wire EDM Work?

Wire EDM machining is similar to ram EDM, but the electrode is an electrically charged thin wire that cuts the metal part into various shapes. Machining a workpiece using this process also involves submerging it into a dielectric fluid and moving the wire through it to produce sparks as it passes an electric current.

Wire burning produces small chips and high accuracy by melting or vaporizing the material—even hardened steel—instead of cutting it. This so-called wire erosion process slices through metal to create parts deemed unsuitable for conventional machining techniques, and it works well as long as the workpiece has conductivity.

Like ram EDM, wire-cut EDM is another example of non-contact spark machining, during which the wire does not touch the metal. When the wire and the workpiece close, a hot electric charge jumps the gap and melts tiny pieces of the metal.

The wire is continuously fed from a spool and held between upper and lower diamond guides. Since the automatic feeder constantly unspools new wire for use in the machining, as the old wire becomes dull, new wire is there to take its place, so the wire used in this process does not necessarily need to have strong resistance properties.

The guides move in the X-Y plane, but sometimes the upper guide can also move independently, allowing for transitioning shapes, such as circular on the bottom and square at the top. The wire electrode can be programmed to cut complex geometries with excellent surface finishes while holding tight tolerances.

What is Small Hole Drilling EDM?

Although not used as often as wire and ram EDM, hole drill EDM machining is designed to drill small, deep holes with diameters as small as 0.065 mm and depths up to 1m (or 250 times the hole diameter). The electrode and the workpiece are connected to a power supply. After sufficient charge builds up on the electrode to create a high-temperature spark, the electrode vaporizes and erodes the workpiece in a localized area.

The electrode is hollow, allowing dielectric fluid to pass through it, and along with the rotation of the electrode, stabilizes the EDM process and helps remove the workpiece debris. The spark erodes the material as the electrode is rotated and moved down until the hole is complete.

What are the Applications of EDM Machining?

Because they are high-precision machine tools, wire EDM machines are top-rated in the automotive, medical, and aerospace industries. However, they help make prototypes or for full production runs and are often employed in the manufacturing industry for metal components and tools. The EDM process is favored for applications requiring low levels of residual stress.

Here are the three leading industries of EDM machining:

Automotive Industry

The automotive industry requires a manufacturing process for parts with complex shapes using hard materials. Because of this, they favor using wire EDM machines because the process does not rely on mechanical forces that lead to tool wear, and the wire electrode does not need to be stronger than the workpiece. The process works well for making holes and cavities for parts like bumpers, dashboards, and car doors.

Medical Industry

EDM machines produce accurate parts in all medical fields, including optometry and dentistry. They are used to manufacture medical equipment parts and components and medical and dental implants and syringe components without affecting their structural integrity.

Aerospace Industry

Wire EDM produces close-tolerance parts for aerospace part manufacturers. This process benefits parts unable to withstand the high temperature and stress associated with traditional cutting tools. For example, many of these components—engines, turbine blades, and landing gear parts—require accuracy and an excellent surface finish.

Applications Specific to Ram EDM

Ram EDM can create complex cavities, making it particularly useful for fabricating molds, dies, and other types of tooling made from hard materials such as tungsten, carbide, and tool steel. It also works better than conventional machining processes for creating sharp inside corners and deep ribs.

Common ram EDM applications include:

  • Dies
  • Plastic injection molds
  • Deep and thin ribs
  • Blind cavities
  • Rapid tooling
  • Sharp inside corners
  • Blind keyways
  • Internal splines
  • Threads

Is EDM a CNC machine?

An EDM machine is one of several CNC machines like CNC mills, lathes, and routers. Programming a wire EDM, for instance, is much like a two-dimensional milling machine, and the program can start away from the workpiece or in the middle inside a pre-drilled hole. Wire EDMs require an NC G-code program for the geometry, as found in milling (G90, G91, G00, G01, G02, G03).

The differences are in the M-code commands. Wire EDMs have many specialty M-codes specific to wire EDM operations. The most effective method for wire EDM programming is a dedicated software module designed for wire EDM operations. This specialty software provides time-saving processing tools that will not be found in software designed for milling.

What Materials Can Be Machined by EDM?

Any conductive material, including stainless steel, titanium, tungsten, carbide, aluminum, brass, alloys, and superalloys, can be cut using the EDM machining method. Because of its accuracy and capabilities on hardened steel, EDM, specifically the wire-cut technique, has become a popular cutting method in all industries.

What are the Benefits of EDM Machining?

One primary advantage of the EDM process is that the tool electrode (wire or graphite) never touches the workpiece, meaning that it never stresses the part. For example, medical device manufacturers can use EDM to add slots, grooves, and eyelets in machined parts while applying minimal stress.

Another plus of EDM is its high-quality surface finish. The EDM process creates smooth surfaces without burrs while holding tight tolerances. For instance, wire EDM can build very thin eyelets and through-slots in medical devices, which cannot be machined using conventional machining centers.

Other advantages of the EDM method include:

  • Manufacturers can use EDM successfully on heat-treated or any hard materials
  • An excellent surface finish, up to 0.2 microns, can be achieved
  • Because the tool and work do not have contact, mechanical stresses are not developed
  • Complex shapes can be reproduced
  • Highly accurate
  • Economical
  • Machining time is not significantly more than the traditional machining process.
  • The tool life is extended because of proper lubrication and cooling
  • Hard surfaces that are also resistant to erosion can be developed easily on the dies
  • EDM works on any material that is electrically conductive

What are the Limits (Disadvantages) of EDM?

The EDM process removes material with electrical charges, which means it’s limited to electronically conductive workpieces and will not work on composite or dielectric materials. Wire EDM cutting may create an oxide layer on the surface of specific metals, so it must be cleaned to maintain optimal quality.

Electric discharge machining is challenged by parts and components that can only be held firmly without compromising the shape. For example, tubular-shaped parts risk being deformed while secured for EDM cutting, causing quality issues.

Other disadvantages of EDM machining include:

  • Slower machining times
  • Excessive electrode tool wear
  • Reproduction of sharp corners might not always be possible
  • Metallurgical properties of the material could change from the high heat
  • Deep-hole electrodes often need redressing
  • Experienced EDM operators are hard to find
  • EDM machines consume high amounts of power

In Summary

A quick comparison of sinker EDM and wire EDM reveals their differences:

Sinker EDM uses a graphite electrode tool with a shape machined on the end that is “sunk” into the workpiece. The movement of this method is mainly along the Z-axis. The dielectric liquid in which the operation occurs is typically hydrocarbon oil. The process is predominately used in mold making.

On the other hand, wire EDM has thin brass wire as its electrode to cut into the workpiece from the side. The movement in this method is along the X and Y axes, and its dielectric liquid is usually deionized water. Wire EDM has numerous applications, with punches, tooling, and dies being high on the list.

As with other CNC machine tools, EDM machines are becoming more intelligent, resulting in devices requiring little or no attention. Most of these changes focus on making the equipment easier to operate or run without an operator.

As things stand now, EDM machining offers various benefits such as high accuracy, good surface finish, and the capability to machine hardened material. However, EDM machining has a few disadvantages, such as slower machining times, that must be addressed when applying EDM machining.

About Peter Jacobs

Peter Jacobs is the Senior Director of Marketing at CNC Masters, a leading supplier of CNC mills, milling machines, and CNC lathes. He is actively involved in manufacturing processes and regularly contributes his insights for various blogs in CNC machining, 3D printing, rapid tooling, injection molding, metal casting, and manufacturing in general. You can connect with him on his LinkedIn.

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MX Software – Easy to Use, Easy to Learn – Included with your machine purchase
The MX software is designed to work seamlessly with your CNC Masters machine. It is made to work with Windows PC – desktop, laptop, or an all in one – on standard USB. Use it on Windows 8 or 10 64-bit operating systems.
No internal conversion printer/serial port to USB software or additional conversion hardware is used with the MX.

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2. Clutter Free Interface
The MX is engineered for the CNC MASTERS machine so you do not have to fiddle with a detailed complicated configuration that can be overwhelming. Just load in the MX and start machining!2. Clutter Free Interface
The MX is engineered for the CNC MASTERS machine so you do not have to fiddle with a detailed complicated configuration that can be overwhelming. Just load in the MX and start machining!

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3. Features Tour and Tutorials Included
The Features Tour will give you a quick run-down on all the features the MX can do for you. The Tutorials are easy to follow even for the first time CNC machinist.
Feel free to download the MX on any of your computers. We recommend downloading the MX along with your CAD and CAM software there at the comfort of your office computer to generate your tool path programs. You don’t need to be hooked up to the machine either to test your program in simulation mode.

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4. Navigate and Edit Your Program through the MX interface with Ease
With a few clicks of the mouse or using touch screen technology, you can easily navigate through the MX interface importing saved programs into the Editor from the File drop down menu. Using standard windows features to edit your program you can then lock the Editor Screen to avoid accidental editing, and if you need to insert a line in the middle of a program, just click on [ReNum] to re-number your tool path list.
You can create a program or import CAM generated G-code tool paths into the Editor
The X Y and Z W arrow jog buttons are displayed from the point of view of the cutter to avoid confusion when the table and saddle are moving. You can also adjust your spindle speed and coolant control while jogging each axis.

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5. Feed Hold – Pause in the Middle of your Program
Feed Hold lets you pause in the middle of a program. From there you can step through your program one line at time while opting to shut the spindle off and then resume your program.
You can also write PAUSE in the middle of your program and jog each axis independently while your program is in pause mode.

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6. Hot Keys
Hot Keys is an alternative method to easily control your machine using your hard or touch screen keyboard. One can press P to pause a program, press S to turn Spindle On, G to run a program, Space Bar to Stop, J to record your individual movements one line at a time to create a program in teach mode.

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7. Pick Menu – for conversational mode programming
Write FANUC style G-codes directly into the Editor or select commands off the [Pick] menu and write your tool path program in conversational mode such as what is written in the Editor box. You can even mix between conversation commands and G-codes in the same program.

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8. Pick Menu List of Options
Use commands such as MOVE, SPINDLE ON/OFF, COOLANT ON/OFF, PAUSE, DELAY, GO HOME…. to write your tool path programs in conversational mode.

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9. Draw the Tool Path to verify it before pressing Go
Hit Draw to view your tool path program drawing, check out its run time, or even simulate the tool path in 3D mode. This can be helpful to quickly verify your program before running it. You can also slow down or speed up the drawing or simulation process.
You can also hit Go within the Draw Window itself to verify the cutter’s position on the machine. The current tool path will be highlighted and simultaneously draw out the next path so you can verify what the cutter will be doing next on the program.

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10. Run each tool path independently to study its movement
1. Run the machine on Trace mode. You can run each tool path independently, one line at a time to study the tool path movement on the machine to verify the position of the application and if any fixture/vise is in the way of the cutter’s path.

2. You can also verify your program by clicking on the Trace and Draw buttons together. This will allow you to view each tool path independently one line at a time in the Draw Window.

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11. Counters display in Inches or Millimeters – Continuous Feed
1. When running a program, the counters will display a “real-time” readout while the machine is in CNC operation without counting ahead of the movement.
2. The current tool path is highlighted while the machine is in operation without causing slight interruptions/pauses as the software feeds the tool path to the machine. The MX internally interprets a program ten lines ahead to allow for “continuous machining” avoiding slight interruptions as the machine waits for its next tool path command.
3. “Run Time” tells you how long it takes to run your tool path program.

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12. Use the “Go From Line” command to start in the middle of your program
If you ever need to begin your program from somewhere in the middle of it, use [Go From Line] which you can find under Tools. The Help guide will walk you through how to position the cutter without losing its position on the machine.

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13. Exact Motion Distance without over-stepping on an axis while jogging
Use “Relative ON” to enter a specific coordinate to jog any of your axes to an exact location without having to write a program. It’s like using “power feed” but easier. You can jog an exact distance on any of the axes without needing to keep the key pressed down and mistakenly over-step the movement releasing your finger too slowly off the jog button.
Let’s say you need to drill a hole exactly 0.525” using the Z. So you enter 0.525 in the Z box. Next, adjust the JOG FEED RATE slider for the desired feed rate. Then “click once” on the +Z or -Z button to activate the travel. In this case you click once the -Z button first to drill the hole exactly 0.525”. Then click once on the +Z button to drive the axis back up 0.525”.

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14. Teach Mode – Jog Input
You can create a tool path program by storing each point-to-point movement by simply jogging an axis one at a time. Click on either of the Jog Input buttons to store each movement on the Editor Screen. You can then add Spindle ON, feed commands, and press GO to run the new program as needed. This is a great feature to help you learn to create a program by the movements you make on the machine without necessarily writing out an entire program first.

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15. Override on the fly to adjust the Jog Feed to Rapid or the Spindle Speed during the middle of a program
1. Jog Feed and Rapid with Override: You can adjust feeds using the slider from slow minimum 0.1″ per minute to a rapid of 100″ per minute of travel. You can even micro-step your jog as low as 0.01”/min. The [-][+] buttons allow you to fine tune feeds in 5% increments while the program is in motion.
2. Spindle Speed with Override: You can adjust speeds using the slider from a slow minimum RPM to the max RPM according to the machine setup. The [-][+] buttons allow you to fine tune feeds in 5% increments while the program is in motion.

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16. Adjust Counters using Pre-Set if you cannot begin the program from 0.00
In a situation where you cannot begin your cutter at it’s 0.00 location, you can “Pre-Set” directly into the counters by typing in your beginning coordinate. You can press Go from here to run your program. You can also “zero all” or “zero” your counters independently. With one click of the [Return to 0.0] button, all axes will travel back to its respective 0.0 on the machine.

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17. Set and Save your 0.00 position for future runs
Set and save your 0.00 position on the machine. These coordinates will be recorded as the first line of the program in the Editor Screen. Should you desire to return to this program at a later date, you only have to click on the Set Zero Return button. This will command the machine to automatically jog each axis to its saved “set” 0.00 position according to the recorded coordinates at the first line of the program.

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18. Create a “Home” position to clear your application and run multiple times
Let’s say you need to machine one application times 100 pieces. This usually requires a jig to retain that physical 0.00 position. But in this case, you want the program to end with a clearance of the axes to easily switch out the next piece of stock and start again. With Save Home, you have the ability to save this offset (home) position while still retaining your Set Zero position where the machine will mill your part out. Pressing [Save Home] will record this new position under the Set Zero line in your program.
Pressing [Go Home] will jog your axes back to your “saved home” position where you originally pressed the Save Home command. You can also input GO_HOME from the Pick Menu as its own tool path in your program. At the completion of your program the axes will end at your Home position. Replace your part, then press [Return to 0.0] button to allow the axes to return to its zero position, and press Go to start your next run.

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19. Disable the axis motors to manually hand crank each axis into place
Easily de-energize the axis motors by clicking [Disable Motors] to crank each axis by hand, and then press [Reset Control] to re-energize the axis motors.

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20. Change up to 30 tools with compensation, and store your tool offsets for other programs
The MX supports…

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21. Use the optional ATC rack up to 8 tools for milling, drilling, and rigid tapping applications
The CNC Masters Automatic Tool Changer Rack and Tools (US Patent 9,827,640B2) can be added to any CNC Masters Milling Machine built with the rigid tapping encoder option. The tutorial will guide you through the set-up procedure using the ATC tools.

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22. Use the optional Rigid Tapping Wizard without the need for tapping head attachments
When you order your CNC Masters machine, have it built with the optional rigid tapping encoder. You can take any drill cycle program and replace the top line with a tapping code created by the wizard to tap your series of holes up to 1/2” in diameter.

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23. Use the optional Digital Probe to scan the profile and/or pockets of your fun/hobby type designs to write your tool path program and machine out a duplicate of your original design To “surface” scan an object, you can program the probe along the X or Y plane. The stylus will travel over the part starting on the left side front corner of the object and work its way to the end of the part on the right side. Depending on how the stylus moves, it will record linear and interpolated movements along the X, Y, and Z planes directly on the MX Editor.
To “pocket” scan an object containing a closed pocket such as circles or squares, the scan will start from the top front, work its way inside of the pocket, and scan the entire perimeter of the pocket.
Under the Setup of the MX software you will find the Probe Tab which will allow you to calibrate and program your probe. Your “Probe Step”, “Feed”, and “Data Filter” can also be changed on the fly while the probe is in the middle of scanning your object.

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24. Use work offsets G54-G59 for nesting applications
The work offsets offer you a way to program up to six different machining locations. It’s like having multiple 0.0 locations for different parts. This is very useful especially when using sub-routines/nesting applications.

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25. Create a Rectangular Pocket / Slot with our selection of Wizards to help you build a tool path program
The Cycle Wizards for the mill or lathe makes it easy to create a simple tool path without needing to use a CAD and CAM software.
On this Wizard, the Rectangular Pocket / Slots, can be used to form a deep rectangular pocket into your material or machine a slot duplicating as many passes needed to its total depth.

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26. Create a Circular Pocket Wizard
Input the total diameter, the step down, and total depth and the code will be generated.

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27. Do Thread Milling using a single point cutter Wizard

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28. Cut a gear out using the Cut Gear Wizard with the optional Fourth Axis

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29. Create a Peck Drilling Program in Circular or Rectangular Patterns
Using the Circular or Rectangular Drilling Wizards, you can program the machine to drill an un-limited series of holes along the X and Y planes. Program it to drill straight through to your total depth, use a high-speed pecking cycle, or deep hole pecking cycle. You can program the cut-in depth and return point for a controlled peck drill application to maximize chip clearance.

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30. The MX interface can easily be interchanged from Mill Mode to Lathe Mode
Use this interface for your CNC Masters Lathe. It contains all the same user-friendly features and functions that comes in Mill Mode. Simply go to the Setup page and change the interface.

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31. Use Tool Change Compensation or the optional Auto Tool Changer Turret if your application requires more than one tool in a single program
You can offset the length and angle of each tool and record it under Tools in your Setup. The program will automatically pause the lathe’s movement and spindle allowing you to change out your tool, or allowing the optional ATC Turret to quickly turn to its next tool and continue machining.
On the MX interface, you also have four Tool Position buttons. Select your desired T position, and the auto tool post will quickly turn and lock itself to that position.

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32. Use the Lathe Wizard Threading Cycle to help you program your lathe’s internal or external threads in inches or metric

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33. Use the Lathe Wizard Turning / Boring Cycle to help you program simple turning and boring cycles without having to go through a CAM or writing a long program with multiple passes

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34. Use the Lathe Wizard Peck Drilling Cycle to help you program your drill applications or for face grooving

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35. Facing / Grooving / Part Off Cycle Wizards – with Constant Surface Speed
These cycles can be used with Constant Surface Speed allowing the spindle speed to increase automatically as the diameter of the part decreases giving your application a consistent workpiece finish. With CSS built into the wizard, there is no need to break down the cycle into multiple paths and multiple spindle speed changes.

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36. This is our list of supported G and M codes which can be found under Tools > G Code/ M Code List in the MX
If you plan to use a third-party CAM software to generate your tool path program, use a generic FANUC post processor and edit it to match our list of codes. As an option, we also sell Visual mill/turn CAM software which comes with a guaranteed post processor for our machines to easily generate your tool path programs based on your CAD drawings.

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37. Our pledge to you…

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