cnc grinder machine

CNC Grinding Machine Buyers Guide: What They Are & How They Work

CNC grinders combine a high-speed grinding operation with precision and an excellent surface finish. Unlike machining operations from other CNC machine tools, its main objective is not material removal. Instead, holding close tolerances using the automation of CNC controls takes precedence.

Here is what you should know about these high-performance machines:

What is a CNC Grinder?

A CNC grinding machine uses a rotating grinding wheel to remove small amounts of material from a workpiece. They are, first and foremost, finishing machines. In the case of round work, a machinist often removes significant amounts of material using a lathe before transferring the part to a cylindrical grinding machine for the finishing operation.

CNC grinding is primarily about taking off small amounts of metal with a high-speed abrasive rotating wheel acting as the cutting tool. The grinding wheel rotates in place while the part is fastened to the machine and moves in the X-, Y-, or Z-axis. Although these movements depend on the part’s shape and size, the grinding wheel usually requires multiple passes to get the correct finished dimension.

A CNC grinding machine, or CNC grinder, operates automatically with minimum intervention from a machinist or operator. It follows programmed instructions to produce smooth surface finishes while reducing distortion and increasing the grinding process’s efficiency. Flood coolant aids in maintaining the part’s accuracy and finish during the machining process, and Fanuc controls typically ensure an excellent CNC system.

Although the term “CNC grinder” refers to a machine that takes away material via a grinding wheel, there are several ways to make that happen and different types of machines to accomplish it. Here are four of the most common.

What are the Common Types of Grinders?

The most common types of CNC grinders are surface grinders, cylindrical grinders, precision ID & OD grinders, and centerless grinders.

1. Surface Grinders

By far the most common grinding operation, surface grinding is a finishing process to grind a flat metal surface, providing a polished look or holding a critical dimension. The grinder comprises an abrasive wheel, a chuck to hold the work, and a table that either reciprocates or rotates.

The chuck holds the material as it is ground in one of two ways. A magnetic chuck typically holds a ferromagnetic part. If the piece is non-ferromagnetic and nonmetallic, it will require vacuum or mechanical means such as a precision steel vise holding the work and placed on the magnetic table.

The grinding wheel and the part’s material factor into the surface grinding operation. Cast iron and steel make up most grinding projects and tend not to clog the typical grinding wheel. Aluminum, stainless steel, and brass require frequent dressing (regrinding) of the wheel. Grinding at high temperatures can weaken the material or cause it to lose its magnetism.

Whether it’s used for flat, contoured, or irregular surfaces, CNC surface grinding is an efficient and popular automated process.

2. Cylindrical Grinders

In contrast to surface grinding, where a flat plate is a typical workpiece, you would choose a cylindrical grinder for round pieces. As a result, rods, shafts, and cylinders are prime candidates for the cylindrical grinder, but as long as the part has a central axis of rotation, you can also run cams and crankshafts.

The cylinder spins between two centers and rotates in one direction. At the same time, the grinding wheel meets the cylinder, turning in the opposite direction and precisely reducing the diameter of the workpiece. The grinding wheel could be at an angle or parallel to the workpieces during the operation.

Like a lathe, the workpiece can be held in a 3-jaw, self-centering chuck, 4-jaw check, collet chuck, or magnetic chuck. With these setups, the part remains stationary, except for rotating, with the grinding wheel, while the grinding wheel traverses along a fixed bed. However, in all cases, the grinding wheel material must be tougher than the workpiece, and it’s often made of a synthetic compound containing aluminum oxide.

3. Precision ID & OD Grinders

In the past, separate cylindrical grinders would perform the grinding operations on the cylindrical piece’s OD (outside diameter) or on the ID (inside diameter). Whether you worked on the ID or OD, the part and wheel rotated in opposite directions, and the wheel moved toward and away from the piece.

Even though many of these single-purpose cylindrical grinders are still producing parts in many machine shops, they are being replaced by machines with the grinding capabilities for OD and ID grinding in one machine, making them more versatile, productive, and efficient. These ID/OD grinders finish parts with high-quality surface finishes, exceptional accuracy, and concentricity.

ID/OD grinders offer precision grinding on either the inside or outside of a hollow cylinder without removing the part from one machine and setting it up a second time. By changing the grinding tools, operators can grind tapers, steps, contours, and grooves inside and outside a hollow round piece.

4. Centerless Grinders

Centerless grinding is a mystery to many in manufacturing because it doesn’t involve using centers or gripping cylindrical parts in a chuck or fixture to grind them. No work-holding methods are needed since the part is fed between a grinding wheel and a smaller regulating wheel as it rests on an angled workpiece support.

During the grinding operation, the force of the grinding wheel pushes the workpiece into the regulating wheel and against the support, keeping it from spinning off the machine. The regulating wheel determines the workpiece’s rotational speed. By tilting it a few degrees, the workpiece will exit through the wheels and out the back of the machine, a technique called through-feed grinding.

Another method, called infeed grinding, involves the regulating wheel pulling the part against a dead stop placed at the work-rest blade. The grinding wheel is then fed into the part until it is to the correct size. Centerless grinding is an appropriate choice in any industry where cylindrical surfaces’ roundness and accuracy are required.

What are the Primary Grinding Applications of a CNC Grinder?

Automotive

Automotive applications for grinding machines are plentiful and include brake cylinders, brake and steering pistons, spline and gear shafts, connecting rods, camshafts, and crankshafts. Although cylinder heads are typically milled, surface grinders do an excellent job of precision grinding a cylinder head’s face.

The precision grinding of shaft ODs enables perfect fits between gears, bearings, and other mating components. OD grinding ensures the concentricity of the shaft to its centerline while ensuring that accompanying diameters are concentric with one another.

Offset ODs for non-concentric diameters, such as crank pin journals and cam lobes, are ground using crank and camshaft grinders. These special machines are programmed to grind both on-center and offset diameters on the same shaft. Similarly, ID grinders provide precise fits for brake cylinders and connecting rods.

Aerospace

The aerospace industry is well-known for requiring the materials of its components to survive in the harsh environment of aerospace engines. As a result, these high-strength parts can be a nightmare to cut on mills and lathes with conventional cutting tools and processes. Fortunately, those attributes that make these materials challenging to machine can also make them appropriate for precision grinding. Turbine rings and turbine shafts are two of the many aerospace components commonly precision ground.

Medical

Medical industry equipment offers several grinding challenges. For instance, the parts must be corrosion and wear-resistant to ensure they are durable and hold up under the cleaning and sanitization methods they will face. For this reason, medical components are often made with stainless steel and titanium, making them harder to machine using conventional methods. Medical manufacturers call upon surface grinders, cylindrical grinders, and centerless grinders when traditional machining cannot get the precision results their customers demand.

Machine Tool Manufacturers

Grinding is the most accurate of all machining processes, so it isn’t surprising that machine tool manufacturers would turn to CNC grinders when building equipment requiring tolerances of plus or minus 0.0001 inches.

The most popular grinding machines used for building machine tools are surface grinders, ID/OD cylindrical grinders, and centerless grinders. These grinders produce parts that include spindles, ball screws, linear guideways, couplings, cams, racks, pistons, and valve spools.

Tooling Industry

The tooling industry supports the machine tool industry by producing precision chucks, drills, reamers, carbide inserts, gages, collets, and tool holder shanks. It’s worth noting that while the tooling used on conventional machining centers wears over time, grinding wheels can be dressed multiple times to maintain the shape and edge of the abrasives for accuracy and an excellent finish.

What are the Main Features of a CNC Grinder?

The CNC grinding machine consists primarily of the grinding spindle head holding the workpiece while the grinding wheel removes material from the lateral sides or the front. It’s possible to create various shapes on the part, including flat surfaces, steps, grooves, and chamfers, using a surface grinder.

A cylindrical grinder consists of four parts: the head and tail stocks, the grinding wheel (sometimes more than one), the wheel head, and the table. These grinders can do tapering, profiling, stepping, or straight diameters on the ID and OD. There are various ways to hold a workpiece: between centers in the headstock and tailstock, in a chuck, or a collet.

How Much Does a CNC Grinder Cost?

A lot! Studer and Okuma, two respected names in CNC grinding, sell new cylindrical grinders for $300,000 up to the one to two million dollar range. Even a 20-year-old Cincinnati centerless grinder is selling for $80,000.

Find CNC Milling Machines and Lathes to Help You Boost Your Profits

CNC grinders are precision machines for components requiring the tightest tolerances and the smoothest finishes. However, you can also increase your bottom line with versatile machine tools that enable you to participate in work that is too complex or slow for manual mills and lathes. The lineup of CNC machine tools at CNC Masters will hold your tolerance over production runs of thousands of parts. Their surface finishes are second only to those coming off expensive grinders.

We provide innovative technologies to machine shops, fabricators, and the manufacturing sector by offering select products that give you more for your money. Our CNC control and operating software are designed to be easy to learn and operate, making it ideal for the hobbyist, the self-employed machinist, or any company doing woodworking or metalworking.

No matter where you are, a CNC milling machine or lathe is here to meet your needs at a price you can afford. Talk to the knowledgeable professionals at CNC Masters, and find out what you’ve been missing by not having a CNC machine for your machining work.

CNC Masters designs and builds their CNC machine tools in the USA. So, if you have any questions or concerns about our products, please contact us at CNC Masters today!

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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