Advanced CNC Surface Grinder Considerations

Posted on Oct 23, 2020

CNC Surface Grinder

A CNC surface grinder is a computer-controlled machine tool that removes material from the surface of a workpiece with a grinding wheel. This is known as an abrasive machining method in which abrasive materials are mounted on the top and corners of the grinding wheel for more accurate finishing. Each abrasive particle is used as a single-point cutting tool, and a grinding wheel filled with abrasive is called a multi-point cutting tool.

Due to its relatively limited material removal power, the grinding process is one of the commonly known finishing operations and the chip size ranges from 0.25 to 0.5 mm. Since the pieces are magnetically sealed, CNC surface grinding is typically carried out on ferrous metal materials. In other cases, in preparation for surface grinding, non-magnetic sections may be clamped. In this post, we will take a look at the fundamentals of CNC surface grinders and then explore some advanced considerations.
 

How a Surface Grinding Machine Works

Once the table lifts the object, the chuck of the CNC surface grinder will move back and forth the grinding wheel. The interval can be set for each pass. As the grinding wheel and its abrasive particles rotate, a small amount of material is removed each time to form a flat surface. Therefore, the surface grinding process is usually a finishing step to reach a certain tolerance. A polishing step is usually carried out during the grinding and lapping process. Below is a video animation breaking down the surface grinding process.
 


Surface Grinding Machine Working & Classification, AniMech

 

CNC Surface Grinders Development

Over time, CNC surface grinders have been developed into more advanced machines. Today, there are even some ergonomic and portable machines. No matter which type of machine you choose, it is commonly controlled by a computer interface.
 

Materials Used In a CNC Surface Grinder

Two types of abrasive materials are used in the grinding wheel. As long as the material has high ductility or permanent deformation ability, alumina will be used. The other is silicon oxide, which is used when the material being polished has low ductility. No matter what type of material you want to grind, the abrasive particles of the machine can smoothen the surface. Usually, these abrasive particles are coated with diamonds.
 

Types of CNC Surface Grinders

The grinding wheel of a CNC surface grinder has a design similar to a doughnut. The hole in the middle slides down over the top of the metal rod or spindle. Today, these CNC surface grinding machines are produced by many different manufacturers, so there is a wide variety of models to choose from. However, they still use one of the following structures:
 

Vertical Type

The vertical spindle design CNC surface grinder has the spindle aligned vertically. The grinding wheel itself lies flat on the bottom of the spindle, so the entire width of the grinding wheel can be used for grinding objects. Generally, this design is used in situations that require the processing of larger panels or plates or where a large amount of material needs to be ground quickly.
 

Horizontal Type

The wheels of the horizontal spindle design are suspended above the worktable. Only the flat outer edge of the wheel will come into contact with the object held by the chuck. Thanks to the small grinding surface, high precision can be achieved when cutting, which is why they are usually used when small features are required.

The spindle used to rotate the grinding wheel can be placed vertically or horizontally. The rotary grinder has a rotating work table, and the grinding wheel itself can also rotate. They can be vertical or horizontal.
 

The Grinding Wheel and the Material of the Workpiece

When performing machining operations on your CNC surface grinder, you need to understand the relationship between the grinding wheel and the workpiece material. Cast iron and most steels are often ground to perfection. However, other materials, such as aluminum, stainless steel, brass, and plastic, may become overheated and begin to corrode in the grinding wheel.

Both of these issues slow down the process. The grinding wheel does not have to be flat. In some cases, you may want to customize the contour of the grinding wheel to apply selected patterns to the surface of the workpiece.
 

:: Read More: Problems in a CNC Surface Grinder
 

Why Are Coolants Necessary in a Surface Grinding Process?

Most CNC surface grinders are equipped with a coolant system. The coolant is guided through the contact point between the grinding wheel and the workpiece. This prevents the deformation of the workpiece due to uneven temperature caused by the cutting motion. In addition, the coolant can keep the washed chips away from the grinding wheel and contact points, to ensure unhampered cutting.
 


 

Water can be used as a coolant, but various alkali-containing compounds are usually added to improve the lubrication quality and prevent the machine and workpiece from rusting. With the exception of aluminum, cheap coolants commonly used for all metals consist of about 1/4 pound of sodium carbonate solution dissolved in 1 gallon of water. Another good coolant is made by dissolving soluble cutting oil in water. For grinding aluminum and its alloys, the use of a transparent water coolant will produce good results.
 

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