Cylindrical grinding/cylindrical polishing

On this page, we will explain the processing methods of cylindrical grinding and cylindrical polishing, and introduce the characteristics, advantages, and disadvantages of each type of cylindrical grinding, which can be roughly divided into three types.

Please also refer to the “Polishing service” page for the polishing process performed at TDC.

What are cylindrical grinding and cylindrical polishing?

Cylindrical grinding, as the name suggests, is a processing method for grinding the outer surface of a cylindrical workpiece. The process generally called “cylindrical polishing” is actually this “cylindrical grinding”.

Grinding uses a grindstone with each grain acting like a blade, so it is suitable for manufacturing and precision processing that require a higher degree of precision, and has much higher dimensional accuracy than lathes and milling machines. is possible.

For this reason, when it is difficult to finish the part within the specified error range with lathe processing, or when heat treatment makes it impossible to use a general turning tool, cylindrical polishing is used.

In addition, after cylindrical grinding and cylindrical polishing, a scratch-free finish that makes polishing marks less noticeable enables a more precise and beautiful polishing finish.

Advantages of cylindrical grinding/polishing

Cylindrical grinding and cylindrical polishing have the following advantages.

• Higher precision processing than processing methods such as lathe, milling, and centerless grinding is possible.
• Can grind the outside of circular side and cylindrical workpieces
• By using CBN grindstones and diamond grindstones, it is possible to cut extremely hard workpieces such as chrome-plated or hardened steel.
• Machining is possible even if there are grooves, etc.

Disadvantages of cylindrical grinding/polishing

While cylindrical grinding and cylindrical polishing have many advantages, they also have the following disadvantages.

• less productive

Cylindrical grinding and cylindrical polishing require time to attach and detach workpieces and to operate machines in the machining process.

Therefore, compared to other processing methods, it has the disadvantage of being unsuitable for mass production.

Please use TDC’s polishing technology for cylindrical polishing

At TDC, we are able to respond to consultations on all kinds of cylindrical polishing with our know-how on polishing and grinding that we have accumulated so far and our extensive processing equipment.

• From 1 piece to mass production
• Support from material procurement to full processing
• Compatible with a wide variety of materials

Scratch-free mirror finishing is possible while maintaining strict processing accuracy such as geometric tolerances and dimensions.

*TDC’s cylindrical polishing technology that achieves nano-level surface roughness is also introduced in “Precise Mirror Polish Surface on Roll and Shaft“.

Types of cylindrical grinding

There are three main types of cylindrical grinding

• traverse grinding
  A method of grinding by moving the grindstone parallel to the axial direction of the workpiece.
• plunge grinding
  A method of grinding by moving the grindstone while fixing the workpiece
• angular grinding
  A method in which a top-shaped grindstone is pressed against the axis of the workpiece by setting a certain angle.

Each processing method has advantages and disadvantages.

traverse grinding

Traverse grinding is one of the processing methods using a cylindrical grinder, and it is a method of performing surface processing by reciprocating in the axial direction of the workpiece.

Reciprocating polishing increases the surface roughness after processing, so mirror surface processing is also possible.

Traverse grinding is suitable for workpieces that are wider than the width of the grinding wheel or for workpieces without steps.

Advantages of Traverse Grinding

Compared to plunge grinding, it is possible to achieve a higher surface roughness.

Mirror surface processing is also possible, so it is possible to manufacture high-precision cylinders.

Disadvantages of traverse grinding

When processing a long object, attention must be paid to accuracy because the central portion tends to bend and the amount of traverse increases.

plunge grinding

Like traverse grinding, it is one of the most commonly used grinding methods. It is a method of scraping by pressing the grindstone vertically against the rotating workpiece.

It does not slide in the axial direction of the workpiece, but only gives motion in the cutting direction to grind.

Advantages of plunge grinding

Efficient grinding is possible because the force is transmitted more strongly than traverse grinding, which moves in the horizontal direction.

It has high power transmission efficiency and less damage to the machine tool spindle, so it has excellent durability.

Disadvantages of plunge grinding

When machining deep pockets or dents, the chips may become clogged and difficult to eject.

In addition, it is necessary to install a hole as a discharge port for chips.

angular grinding

It is a grinding method in which a top-shaped grindstone is pressed against the axis of the target object at a certain angle.

It is characterized by being able to grind the outer diameter and end face of a cylinder at the same time, making it possible to perform stepped workpieces more efficiently in a short time. Also called angle slide plunge grinding.

Advantages of angular grinding

In addition to being able to process the end face into a concave shape, the end face and outer diameter can be ground at the same time, resulting in high processing efficiency and high productivity.

Disadvantages of angular grinding

Ultra-high precision and precision grinding such as mirror surface grinding cannot be performed.

Normally, NC equipment is used for processing, but since it cuts at an oblique angle, it is necessary to make corrections that take into account deterioration over time.

Another disadvantage is that it is complicated to sharpen the surface of the whetstone to restore its sharpness.

spark out

In cylindrical grinding, you often hear the term “spark out”.

Spark-out means to let the grindstone idle for a few seconds without cutting at the end of the grinding process.

By using spark-out for the final finish, the uncut part is removed and the machining accuracy in cylindrical grinding can be improved.

Precautions for cylindrical grinding

The following precautions and defects may occur in cylindrical grinding.

• chatter
• Scratches and feed marks
• Poor workpiece accuracy

crack

Chattering refers to the condition in which mottled patterns occur on the finished surface of the part to be machined.

• The main causes are as follows.
• machine vibration
• Run-out or inaccuracy of grinding wheel
• Incompatibility of processing conditions
• Decrease in sharpness

Scratches and feed marks

A feed mark is a flaw that occurs on the machined surface, and it is a defect that is likely to occur in cylindrical grinding that gives rotary motion.

The main causes are as follows;

• Inappropriate grinding wheel selection
• Poor dressing of grinding wheel
• Inappropriate grinding fluid
• Inappropriate selection of granularity
• Inappropriate grinding wheel peripheral speed
• Poor center alignment
• Inappropriate retouching

Poor workpiece accuracy

Defects can occur if the workpiece to be ground has poor accuracy.

The main causes are as follows;

• Inappropriate grinding wheel selection
• work imbalance
• Poor dressing
• Inappropriate center or center rest blade
• Misadjusted grinding machine
• Work thermal expansion

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