cnc grinding machines

CNC Grinding Machines: Everything You Need To Know

CNC grinding machines are a prerequisite for a fully-fledged machine shop

Workshops across the country are transitioning from manual to automated machining, but without CNC grinding machines, that’s still not as impactful. 


You see, a machinist can have the best CNC of milling or lathe machines; however, creating a high-precision workpiece also calls for efficient material removal, among others. 


So you can’t expect the primary mill or lathe alone to bring about the most efficiency and productivity; you’ve to sort the secondary machines too. And that’s exactly where the idea of CNC grinding comes into the picture.


A CNC-powered grinding machine is the perfect way to complement the working of a CNC milling machine, lathe machine, etc. Not to mention, a grinding machine can also be the primary machine in your workshop, depending on your machining requirement. 


As such, it’s important to understand the basics of CNC grinding. 


Now, if you’re wondering what is CNC grinding and how exactly such a grinding machine works, you’re at the right place, as we’ve created an all-inclusive CNC grinding guide. 


So let’s dive right in and get detailed insights. 

What is a CNC grinding machine? 

Before we get into its functionality, you should know what a CNC grinder is all about. 


At its very basic, a grinding machine is designed for removing tiny portions of materials from various workpieces. Meaning it is essentially a finishing machine that you’ll need for creating the final details after you’ve milled or turned your piece. 


For instance, if you’re a mill machinist, you’d want to shift the workpiece to a grinding machine for a final finishing operation after having made the required cuts or drills. 


Talking about its working, a CNC grinder machine has a rotating or grinding wheel that functions as a cutting tool and removes small portions of metal from a workpiece. Herein, the workpiece is attached to the grinder for movement on the X, Y, and Z axis, and the rotating wheel itself spins in its own place. 


A CNC grinding machine functions very similarly to its manual counterparts, the only difference being that the former’s operations are entirely automated. And since the process of grinding or finishing is automated, you need to put in the least manual effort. 

How do CNC grinding machines work differently than manual grinders? 

what is cnc grinding

Unlike a manual grinding machine, where a machinist manually skims through a workpiece, a CNC grinder follows computer programs to do the same. 


So just like any other CNC machine, the grinder also follows the programmed commands to create the finishes on a piece. 


Now, automation in workpiece finishing also brings about quality and efficiency, which is hard to achieve manually. 


How, you may ask? 

  • First, you can expect an exceptionally smooth finish on the surface of your piece and also significantly reduced anomalies. 
  • Second, an automated grinder uses flood coolant that prevents the machine and the workpiece from heating while also lubricating and removing chips from the part. And this ensures smooth and consistent long-haul grinding operations. 
  • Third, the flood coolant, along with the CNC control, also helps achieve high accuracy and a top-notch finish on your workpiece. 


That’s impressive, isn’t it? 

What are the different kinds of CNC grinders? 

Now, while CNC grinding is all about automated finishing on any workpiece, there are different ways it’s done depending on the grinding machine. Meaning your grinder will decide how your piece is machined, and that, in turn, will determine the shape, smoothness, etc., of the final product. 


So let’s have a look at the various CNC grinders and how they work. 

#1. Surface grinding CNC machine 

A surface grinder is indeed the most common of all grinding machines. So much so that you’ll spot a surface grinding machine in a majority of metalworking shops. 


Talking about its utility, a CNC surface grinder comes in handy for finishing a flat metal workpiece. Herein, the metal piece is polished, and its dimensions are fine-tuned to meet the exact specifications. 


So how does this grinder work? 


Well, the working of this CNC machine class is quite simple. And it involves the chuck of the surface grinder that holds your piece while it is being finished in either of the two machine ways. 


The best thing about CNC surface grinding is the ability to effortlessly machine virtually any type of metal, including cast iron, stainless steel, brass, aluminum, and more. 


You see, the grinding wheels on a manual surface grinder call for regular dressing, among other maintenance requirements. Also, high temperatures are a worry on such machines, something that can damage your workpiece. 


Nevertheless, such concerns don’t exist on a CNC surface grinder. 

#2. Cylindrical CNC grinder

As the name itself suggests, cylindrical CNC grinding machines are used for finishing operations on round-shaped workpieces instead of flat pieces. 


So you can use a cylindrical grinder for machining objects like shafts, cylinders, and rods, among others. Also, you can use these CNC machines for those workpieces that have their axis of rotation at the center; for instance, crankshafts and camshafts. 


Coming to its working, the pieces in a cylindrical grinder spin between the centers while rotating in a single direction. The grinding wheel in this kind of operation rotates parallel to the piece but in the opposite direction, thus creating a precise finish on the object. 


However, some cylindrical CNC grinders may work differently, closely replicating the working of a CNC lathe machine


For instance, certain cylindrical grinders hold the workpiece in a 3-jaw, 4-jaw, collet, or self-centering chuck, among others. And operations on such grinding machines involve a stationary workpiece and a grinding wheel moving on a fixed bed. 


In fact, both kinds of cylindrical CNC grinders are readily available on the market, meaning you can easily choose one that suits your requirements. 

#3. Centreless grinding machine 

A centreless grinder is the most uncommon of all grinding machines, and its operations present a marvel of modern engineering. That’s because, unlike its previous two counterparts, a centerless grinder neither uses a center nor does it hold the piece in a chuck for a finishing operation. 


Now, you’re sure to wonder how this machine grinds a piece. 


You see, centerless CNC grinding involves keeping the workpiece between the main grinding wheel and a secondary regulating wheel. And it does not need any workpiece holding mechanism to do so since the piece is dependably fixated on an angled support system. 


What prevents the piece from spinning off the grinder? 


The grinding wheel plays an important role here, using its force to push the piece into the secondary wheel. 


Here, the secondary wheel decides at what speed the workpiece rotates during machining. And once machined to precision, the wheel is tilted a little for the piece to exit from the back of the machine. 


Innovative, right? 

#4. Precision CNC grinding machines (for all-purpose cylindrical operations)

There was a time when cylindrical grinders would either finish the outer diameter or the inner diameter of a workpiece. In fact, in some cases, you even needed a different grinding machine altogether for both outer and inner finishes. 


But that’s not the case anymore with the modern-day precision CNC grinding machine. That’s because these machines can easily perform finishing tasks on the outer and inner diameters of a cylindrical piece in one go. 


As such, with one of these precision grinders, you need not remove the workpiece for an inner finish after having completed the outer finish, and vice versa. Also, with the automatic tool changer on your CNC precision grinder, you don’t even need to change the tools manually for different operations. 


Sounds awesome, doesn’t it? 


While machine shops still use single-purpose grinding machines, a lot of them are quickly switching over to all-purpose precision grinders, thanks to the convenience they offer. 

#5. Special-purpose grinding machines 

Apart from the above four classes of CNC grinding machines, there are also some special grinders that are made for some specific functions. And that includes: 

Cutting and tooling grinders

These grinders aren’t meant for major finishing operations. Rather, they’re designed for tasks such as sharpening the milling cutters, taps, and reamers, to name a few. 

Threading grinders 

By the looks of it, a threading grinder closely resembles a cylindrical grinder. However, unlike cylindrical grinders, a CNC threading grinder performs tasks such as dressing the grinding wheel’s cutters or creating a thread form on a part, among others. 

Jig grinders 

These are made for precisely grinding the holes, both tapered and straight. And they do so with an in-built vertical spindle that holds and drives a grinding wheel. 


You may also want to read – CNC Controller Board: 7 Best Options In 2023

What are the important considerations before buying a CNC grinder? 

cnc grinding machine

There are a lot of considerations that a machinist should factor in before settling for a CNC grinding machine, which include: 

#1. High-precision 

Like all things CNC, a CNC grinder is also about offering the highest levels of precision and accuracy, something that’s hard to achieve manually. 


So the level of precision that a grinding machine offers should be a determining factor before you decide on buying it. 

#2. Versatility 

Modern machine shops are increasingly diversifying their operations. So much so that an average workshop now machines more than one material type, unlike in the old days. 


For instance, you can find a mill that also undertakes drilling and turning operations. 


And to that end, your CNC grinder should be multi-purpose to be able to support the versatile nature of your shop. 

#3. Sturdiness 

For effective machining and finishing, the grinder machine has to be solid. After all, it has to make cuts into heavy metals like cast iron and stainless steel, to name a few. 


Also, you should make sure that the grinding wheel of the machine is tougher than the material that you’re looking to machine. 

#4. Size of the workpiece 

Before you go on a shopping spree for the CNC grinder and its many accessories, it’s important you figure out the approximate size of the piece you’re looking to machine, 


This way, you can ensure that your piece actually fits into the grinder. 

#5. Speed vs. RPM

You see, while some machining tasks call for high speed, others need more RPM. 


For instance, removing materials and creating design patterns on a heavy metal will need a higher RPM. Similarly, some surface grinding operations meant to smoothen a surface might need more speed than RPM. 


So we suggest you go for such grinder machines that offer the right balance of RPM and speed.

#6. Coolant 

Grinding operations produce a lot of heat. And a lack of proper coolant can not only overheat the machine but also result in poor finishing. 


Worse, heating can also damage your workpiece beyond repair. 


As such, a good-quality coolant is quintessential for any type of grinding CNC or non-CNC. 

#7. Flexible conditioning and dressing

The in-build dressing and conditioning systems on the CNC grinding machine should be easy to understand and control. 

#8. Effective automation 

A CNC machine should be such that it needs the least manual intervention. In fact, for the best precision, efficiency, and machining speed, full-fledged automation is necessary. 


As such, you should check the CNC grinder machines for automatic tool changers, closed-loop measurements, etc., before buying. 

Can manual grinder machines be converted to CNC? 

grinding machine CNC conversion kit

Yes, certainly. 


If you own a manually operated grinder, you can have all the CNC machining features on the very same machine after CNC conversion. And to do so, CNC conversion kits are readily available. 


In fact, if you’re looking for cost-efficient CNC grinding, you can buy a manual machine and then get it converted to CNC. That’s because, in terms of features, a turn-key CNC is as good as a brand-new CNC machine. 

Wrapping it up

As you can see, an all-purpose CNC grinder machine is the perfect way to complement your CNC mill or lathe. 


Not to mention, CNC grinding machines can also be standalone equipment for specialized finishing workshops. 


Want to buy one such CNC grinder or get your existing machine converted to CNC? 


You can get in touch with us


At CNC Conversion Plus, we have the largest inventory of CNC conversion kits and turn-key machines from leading manufacturers like Grizzly, Little Machine Shop, and more. And we can convert your ideal machine to CNC and ship it to your workshop at the most cost-efficient prices. 


Furthermore, you can also send your existing machine to our facility for a complete CNC makeover. 


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