Advanced CNC Surface Grinder Considerations

Posted on Oct 23, 2020

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CNC Surface Grinder

A CNC surface grinder is a computer-controlled grinding wheel that removes material from the surface of a workpiece. It is also known as the abrasive machining method in which abrasive materials are mounted on the top and corners of the grinding wheel for more accurate finishing.

A CNC surface grinder is a computer-controlled grinding wheel that removes material from the surface of a workpiece. It is also known as the 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 to make it deeper into 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.
 

CNC Surface Grinders Development

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

:: Read More: The Critical Chain Component in Metal Machining: CNC Surface Grinder

Materials Used in a CNC Surface Grinder

Two types of abrasive materials are used in the grinding wheel. As long as the material being ground 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 smooth 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 are many different models to choose from. However, they still use one of the following types of structures:
 

Vertical Type

The vertical spindle design CNC surface grinder has the spindle vertically up and down. 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 processing on larger panels or plates or where a large amount of material needs to be quickly ground.
 

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.

Like there are two common types of spindles, there are also two common types of CNC surface grinders, both of which can only grind flat surfaces. These include: the surface grinder keeps the grinding wheel in one position when moving the worktable of the grinding wheel, thereby generating a reciprocating back and forth movement, which can be controlled manually or by a mechanical or hydraulic drive mechanism.

The spindle used to rotate the grinding wheel can be placed vertically or horizontally. The rotary grinder has a round rotatable worktable, 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 or may become embedded in the grinding wheel.

Both of these issues slow down the process. The grinding wheel does not have to be straight. In some cases, you may need to customize the contour of the grinding wheel because they will give the selected pattern to the surface of the ground part. It is also known that surface grinding operators use straight grinding wheels and process patterns in them.
 

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 temperature unevenness caused by the cutting action. In addition, the coolant can keep the washed chips away from the grinding wheel and contact points, so that they can cut freely.

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 quite good results.
 

Offhand Grinding

Secondary grinding on a CNC surface grinder is the process of positioning and feeding the workpiece onto the grinding wheel by hand. Auxiliary grinding is used to reduce welding marks and defects on workpieces, ordinary lathe tools, planer tools, shaping tools, and drills. Determining the depth of cut and feed depth depends on the operator's knowledge of grinding.

The secondary grinding is carried out on general-purpose grinding machines. These grinding machines usually have a fixed spindle speed and fixed grinding wheel size requirements. Therefore, the cutting speed of the grinding wheel is constant and cannot be changed for different materials.

Therefore, the operator of a CNC surface grinder must be extremely careful when feeding and do not damage the grinding wheel excessively. Otherwise, it will cause excessive wear of the grinding wheel. Likewise, he or she must be careful not to glaze the wheels by applying excessive pressure.

 

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