Centerless Grinding: Bar Grinding Machine

A proper understanding of the basic fundamentals of this grinding process is key to achieving quality custom machined parts. To provide the best grinding services, it is important to master the process of grinding so you can avoid many of the problems that occur during precision grinding.

Learning how to grind steel through the centerless process may be quite challenging. This process is among the least understood methods of producing high quality machine parts, especially the steel round bar. Here is useful information to help navigate steel machining with ease.

What is Centerless Grinding?

This steel machining process is an OD grinding procedure that does not require the workpiece to be mechanically constrained. Unlike in chucker or center-type grinding, the centerless process does not require parts to have center holes, or work-head fixtures. Instead, the workpiece stays in place by its outside diameter, supported by a work-blade set between a regulating wheel with a smaller diameter and a high-speed grinding wheel.

If you master the relationship between among these three basic components, you are ready for rapid machining. It is what makes the difference between highly efficient precision grinding and the troubles associated with the production of misshapen machine parts. These basic parts – the work-blade, grinding wheel and the regulating wheel – combine to make the centerless
process more efficient than other grinding services.

How centerless grinding works

Before the advent of centerless machine part grinding, you would have to grind round parts between centers or find ways of holding them with a fixture of chuck. The centerless method makes work easier because it requires no such inconveniences. The centerless setup has the workpiece between the larger grinding wheel and the smaller regulating wheel.

The grinding wheel produces a force that pushed the workpiece into the smaller regulating wheel and against the work rest. The regulating wheel determines the rotational speed of the workpiece. This speed depends on the diameter of the grinding wheel. If you tilt the regulating wheel by a few degrees, the workpiece will be pulled through the wheels, courtesy of the through-feed grinding

Another technology employed in this process is the infeed grinding. In this process, the regulating wheel pulls the workpiece against a dead stop conveniently positioned at the work rest blade. The lateral force of the grinding wheel lets push into the workpiece, grinding the part to the desired size.

Advantages of centerless grinding

Though cylindrical grinding won’t go away just yet, centerless offers several advantages. First, the centerless techniques provide increased output because it allows for faster loading of parts into the grinding machine. The parts need no clamping in chucks, or location between centers, so it is easy to feed them into the grinding machine.

Centerless processes also enhance precision grinding (Centerless grinding Service Page). The grinding and regulating wheel hold the workpiece securely against the work rest, making it possible to grind even long thin parts, such as lengths of bar stock used in Swiss-style CNC lathes. Moreover, the adjustment of the wheel is diametrical – and not radial – thus reducing feed errors and
enhancing precision.

Types of Centerless Grinders

Classified according to the inclination of the machine bed, centerless machines come into two categories: horizontal and angular. The most common of these two is the former which, during wheel dressing, provides for easy accessibility. But the latter are more useful for grinding heavy parts because they apply a greater grinding force and have less abrading to the workpiece by the work rest.

Another classification does exist, categorizing the machines according to the type of their grinding zones. Under this category, you will find the moving zone, stationary zone and the cross-slide machines. Moving zone machines have the grinding wheel fixed during operation, while the regulating wheel controls the axis movement. This setup makes for a more compact design but requires constant adjustments to the work rest due to the wearing out of the grinding wheel.

As for the stationary zone grinding machines, the work rest setup is such that its support is either completely stationary or requires minimal adjustments. The regulating and the grinding wheel have their separate X and Z axis slides.

The third type in this category is the cross-slide centerless machines. These centerless grinders feature a fixed-dressing setup to maximize precision and lead to fast changeovers. The use of dual grinding machines alleviates concentricity concerns by combining both centerless and grinding between centers of some parts.

Setting up the centerless grinder

Learning the correct setup of the centerless grinder, including choosing the right grinding wheel, helps to avoid many of the errors that may occur during then grinding process. First, begin by setting the right workable height. The height controls the centerline of the workpiece, the height that determines the rounding process of the grinding operation. The workpiece height is a critical measurement that should not be left to chance.

If you are unsure how to go about setting the workpiece height, consider this rule of the thumb. If the workpiece is 1 inch in diameter, ensure half of it lies above the centerline of both the grinding and regulating wheels. This primary setup must be correct for the grinding process to be efficient.

Next, be sure to set the right grinding work-blade angle. This angle should range from 0 to 45 degrees. However, for most centerless applications, a 30 degrees top blade angle should provide the best results. Though a steeper work-blade angle gives the fastest rounding action, a shallower blade angle would be favorable for workpieces with larger diameters. However, consider 30 degrees as a safe starting point.

You also need to set the speed of the regulating wheel. Although the speed of its rotation depends on the diameter of the workpiece and the stock removal rate of the machine, you can adjust it to 30 rpm. The slow rotation speed of the regulating wheel ensures the optimization of the grinding process.

The fundamental principles of centerless grinders and long bar grinding

Centerless grinders feature a seemingly simple but very precise techniques. Since they don’t have many moving parts, they owe their functionality to the basic principles of physics. As such, the process of grinding is relatively simple, and ideal for working small cylindrical parts that need a tight tolerance.

The process of grinding metals has been around for a long time but manufacturers have been equipping grinders with modern features to enhance performance. A good example is the CNC programmable controls which make it easier to set up and change the equipment from one job to another.

Newer technologies have made it possible to make previously impossible dimensions, shapes and tolerances. They have also reduced set up times, loading and unloading times, thus shortening the cycle times of the grinding process.

Unlike most other processes, the skills needed to operate centerless grinders are enhanced through experience, not training. Years of operation in the field lets you learn to set up, adjust and operate these grinders with speed and efficiency. Advance Grinding has been specializing in centerless grinding in the Midwest since 1994!

Steel round bars and their applications

The steel round bar has a wide range of uses and applications in many industries. These bars, due to their unique qualities, have become common in applications such as building and construction shipbuilding, vehicle manufacturing and in the production of household items.

To fulfill their various uses, manufacturers specializing in steel machining fashion them into different shapes and sizes, such as the flat bar and the stainless-steel round bar. Stainless bars are corrosion-resistant, hence suitable for housing construction and creation of machine parts exposed to elements of weather. Common items include base plates, brackets, ornamental work and braces, among many others.

The steel round bar has also found its way to the oil and gas industry, where they is used to make pipes and build structures for support of various equipment. They also make pump shafts in the food and agriculture industry.

The advantages of centerless grinding are quite substantial. They range from rapid rounding to increased efficiency, and the ability to work with extremely smaller workpieces. This type of grinding is also responsible for the production of high-quality steel bars used in many industries today. If you need more information, or have any queries, please contact us at Advance Grinding.

Advance Grinding strives to deliver high precision grinding to sort out your custom parts for your high-end application. Get our free quote or contact for more details.

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