The term grinding machine is the blanket name given to a wide range of machines that are used to grind components or workpieces into shape, producing the required dimensions and the desired surface finish of the pieces. A conventional or “centred” machine has a spindle or fixture that locates the workpiece and secures it while it is ground between rotating wheels. The centreless grinding machine makes use of the rotating wheels to secure the workpiece, and so can discard with the spindle.
It is the absence of this centred spindle in the grinding process that gives centreless grinding machine its power and flexibility. The process is most often used on smaller workpieces that can be worked quickly and that do not need a lengthy grinding process. These items are typically dowels and rods, pivot pins, pistons and other small industrial pieces. The materials that can be worked by the process include metal and metallic alloys, wood, glass and synthetics like nylon and plastics.
How does the machine work?
The centreless grinding machine is made of two wheels that rotate in the same direction but at different speeds, and it is the variation of the wheel speeds that provides the grinding operation of the machinery. The workpiece is placed on a workholding platform, another component of the machine. The grinding wheel is stationery. It rotates on a fixed axis, applying downward force to the workpiece against the workholding platform. The moving or regulating wheel has a rough, abrasive surface that applies lateral force to the workpiece, removing material in large or small amounts.
There are various kinds of centreless grinding processes. With through-feed grinding, the workpiece is fed through the wheels, entering the machine on one side and emerging on the other. The regulating wheel is angled away from the grinding wheel, exerting a lateral force as the workpiece is fed through the wheels. This is a simple and efficient method that is suitable for producing rods and other pieces with cylindrical shapes. End-feed grinding is suitable for tapering workpieces. In this process, the workpiece is fed into one side of the machine and the piece exits after the grinding process. The other side of the workpiece is then fed and worked upon, so that the machine can complete the process.
More complex workpieces require the use of the infeed or plunge grinding process, suitable for items that have more than one diameter. An operator places the workpiece manually on the workstation. He then puts the regulating wheel in place and the grinding process begins. The most up-to-date machines make use of computer technology both to automate the process and to achieve more precise grinding. This matching of technology to the process means that workpieces requiring a high degree of precision can be produced more quickly and easily.
What are centreless grinding machines used for?
More than ever, industry requires precision tools, made to exact dimensions and with the kind of high-quality finish that only precise grinding can produce. For example, the alternative energy sector requires a constant supply of precise, highly finished engine parts such as rotating blades, valves and pistons. The medical profession requires instruments so refined that their production requires almost the same precision as the actual surgical procedures. On the domestic market, there is a constant demand for high-quality items with superb finishes, like electrical goods for the kitchen.
The wonder of the centreless grinding process is that it is available to trades outside of the heavy industrial sphere. There are centreless grinding machines that the user can push across flooring in the manner of a lawnmower, with rotating wheels that level materials like concrete, stone and granite. There are machines that polish high-quality surfaces like marble, applications that are of use in building construction and interior design. Smaller grinding machines can be used to sharpen and refine tools, like sawblades.
Because of changing technology, it makes sense for the modern business to use the services of a specialist centreless grinding firm. Most often, a firm like this can produce the highest quality items at the lowest cost. The firm is likely to have access to computer software into which the machine operator simply feeds the dimensions of the item that he wishes to produce. The computer then takes control of the grinding process, prompting the operator when manual intervention is required. Overall, the centreless grinding process is invaluable to specialist workshops producing dedicated machine parts, rapidly and inexpensively.