Today, manufacturing has developed to a more complex setting, requiring tight tolerance for several custom parts or prototypes. Therefore, manufacturers must employ suitable machining techniques to produce components that meet the standard requirements. Precision grinding remains one of the most effective machining processes applied across diverse industries to produce quality parts. Hence, this article examines the various types, working principles, and applications of precision grinding. Let’s get right into it.
What is Precision Grinding?
Precision grinding is a form of grinding process that focuses on manufacturing and finishing parts with very close tolerances. Typically, grinding machining constitutes a subset of cutting as a metal-cutting process in manufacturing and tool-making. In production, grinding is used for machining various materials, particularly for making shallow cuts to produce fine finishes, shapes, and dimensions.
However, some industrial manufacturing processes require precision and accuracy, so there is little room for production errors, which applies when aiming to fabricate specific components without compromise. As such, precision grinding provides workable solutions to the issue of tight engineering tolerances and finishing problems that most manufacturers face. This grinding operation can remove materials to produce custom parts with tight tolerance dimensions or quality surface finish.
More specifically, high precision grinding allows the machining of workpieces with complete accuracy, achieving very close tolerances as intricate as +/- 13 microns to +/- 1.3 microns for diameter and +/- 2.5 to 0.25 microns for roundness. Likewise, the method can also attain precision for typical finishes with a tolerance range of 0.20 to 0.81 microns.
Benefits of Precision Grinding
Precision grinding offers certain benefits in manufacturing. Check them below:
Cost-Effectiveness and Accuracy
To a large extent, high precision grinding guarantees accuracy while providing a cost-effective means of producing different parts. Most metal manufacturers use this machining method to reproduce specific measurements of intricate parts within the acceptable level of variance. On top of this, the grinding operation helps increase the manufacturing productivity of exact parts while making quality control consistent and easier. Put together, precision grinding is an efficient manufacturing process.
Reliable Machining Alternative
Expert machinists use precision grinding processes when other machining methods or techniques like milling and turning cannot be used. This usually occurs due to the following:
- Type of material；
- The quality of the surface finish required；
- The need to produce parts with small diameters and tight tolerance.
Types of Precision Grinding
There are diverse types of precision grinding processes applied to achieve the precise surface finish and dimension for various components. The characteristics of these grinding operations inform their respective application for specific machining projects. As a result, manufacturers must select the proper grinding operation depending on the size, shape, finishing features, and desired production rate needed for the part.
Here are some of the commonest types of precision grinding.
1. Surface Grinding
Surface grinding is a machining process that produces a smooth finish on flat surfaces, giving them a more refined appearance or adding a particular function. It involves using a rotary wheel coated with rough abrasive particles to remove tiny chips or excess material from the surface of the workpiece. Aside from the wheel, the surface grinding machine comprises a chuck and a table that uses magnets to affix the material.
The integration of CNC provides automated features that enable the consistent removal of materials, thus ensuring high-volume production. However, most precision surface grinding processes are often applied to make the two ends of a metal part perpendicular to the external diameter. In other cases, it is used to attain parallel or squareness in cubic parts.
When CNC turning and milling processes are not adequately precise for a manufacturing project, manufacturers employ precision surface grinding as an excellent alternative. This is because the grinding operation can attain micron-level production tolerances and finishes as low as 0.2 microns. Note that the quality of surface finishes obtained with surface grinding depends on factors such as wheel speed, feed rate, wheel size, abrasive material, and the type of material.
Additionally, surface grinding is well suited for materials easily held by the magnetic chuck without clogging the grinding wheel. These materials include cast iron and many steel grades. Other materials like aluminum, brass, and plastics clog the wheel, preventing it from cutting. That way, only expert machinists conduct surface grinding operations for these materials.
2. Cylindrical Grinding Machining
This grinding operation, also known as center-type grinding, applies to cylindrical surfaces and the shoulder of suitable workpieces. A cylindrical grinder comprises a grinding wheel, a chuck, two centers that hold the workpiece in place, and other features for driving the workpiece. Furthermore, most cylinder grinders come with a swivel to create tapered pieces. The abrasive or grinding wheel can also have different shapes. Machinists use the standard disk-shaped wheels to fabricate tapered or straight workpieces, while the formed wheels help create shaped workpieces.
Concisely, the workpiece is affixed on the center and rotated by the lathe dog or center drive in cylindrical grinding operations. The workpiece and the grinding wheel use separate rotary motors at different speeds. More so, the wheel and workpiece move parallel to one another in longitudinal and radial directions.
Generally, precision cylindrical grinding provides smooth surface finishes for round objects. Moreover, the standard precision tolerances for cylindrical grinding stands at 1.3 microns for diameter and 0.25 microns for roundness. There are two main types of cylindrical grinding, which are:
Internal or Inner Diameter Grinding
As the name suggests, this cylindrical grinding type removes excess material on the internal diameter (ID) of tubes or other part features, including holes or bores. Manufacturers use ID grinding alongside honing to produce smooth surface finishes and parts with tight tolerances.
Both ID grinding and honing processes involve holding the workpiece in place and rotating to limit the size of the part’s internal diameter, becoming lesser than the grinding wheel diameter.
External or Outer Diameter Grinding (OD)
Outside diameter (OD) grinding uses a single wheel to shape the external surface of the workpiece held by the centers. During the OD grinding process, both the grinding wheel and the workpiece rotate in the same course around the central axis constantly. While OD grinding applies to various part shapes such as cylinders, ellipses, and cams, note that the workpiece must have a sizeable central axis diameter that allows hitch-free rotation.
3. Centerless Grinding
This grinding operation entails removing tiny materials to produce a specific finish to the outside diameter or periphery of small, cylindrical workpieces. In most cases, manufacturers use centerless grinding to enhance the surface finishing of turned machined parts to achieve more precision. In contrast to traditional OD grinding machining, centerless grinding does not hold the workpiece between centers or chucks. Instead, the centerless grinder uses a rest blade to support the workpiece on the outside diameter.
Further, centerless grinding employs the action of two wheels: the abrasive grinding wheel and the regulating wheel. Even though both wheels rotate in the same direction, the grinding wheel rotates at a higher speed than the regulating wheel. This allows the centerless grinding operation to grind very small parts.
Unlike other grinding processes, the workpiece moves through the centerless grinder machine without fixtures or motors. Instead, the grinding operation controls the movement through the so-called “magical angle” between the two wheels.
Applications of Precision Grinding in Manufacturing
In most manufacturing industries, precision grinding is often applied as a final machining procedure for diverse components of varying sizes, ensuring accuracy and high productivity rates. They include automotive, aviation bearing, electrical, medical, etc. Here are some common applications of precision grinding:
- Micro-finishing of flat and cylindrical surfaces
- Grinding machining of outer circles, holes, and hole systems
- Grinding of bearing surfaces
- Precise machining of aerospace fasteners, tubes, rods, wires, tools with blades, etc.
Working Principles and Precautions of Precision Grinding Machine
The precision grinding machine uses a rotatory grinding wheel consisting of abrasive particles to remove material from workpieces. Also, the grinder machine comprises an electric motor that delivers motion power to the abrasive wheel through the belt and pulley system. Most grinder motors rotate at a set speed of anywhere from 150 to 15000 rpm, which varies based on the type of grinding project.
Precautions for Using a Grinder Machine
You must follow several safety measures to use a grinder machine safely. Before operating the grinder, you should always wear Personal Protective Equipment (PPE). They help shield against sparks and other flying particles when grinding. PPE includes an apron, safety glass, glove, dust mask, hearing protection, safety boots, etc.
There are some notes to use grinders safely:
- Ensure the grinding guard is well attached.
- Use the right wheel for each grinding operation.
- Ensure the proper assemblage and tightening of flanges and other parts.
- Secure the workpiece to prevent deflections when grinding.
- Check and adjust the grinding speed to the right intensity.
- Ensure the work area is clean.
Main Components of a Grinder Machine
A typical grinder machine is made up of several components. Take a look at the main parts below:
- Grinding Wheel
- Wheel Guard
- Abrasive Wheel Head
- Traversing Wheels
- Coolant Supply Nozzle
Get High Precision Grinding Services At WayKen
Precision grinding operations are common in several industries today. Some manufacturing factories offer precision grinding services on-site, while others outsource it to companies specializing in this machining service.
At WayKen, we have the necessary on-site precision machining technologies and equipment to handle your projects. We take pride in our professionals with many years of experience and skills ready to accommodate your design specifications. Moreover, we assure high-quality, precise, long-lasting, and affordable precision machined parts at any volume.
Feel free to contact us today for one-on-one support service, and you will get a response within 12 hours.
Precision grinding remains one of the most effective and efficient machining techniques for fabricating and finishing parts with closely detailed tolerance requirements. It provides benefits such as cost-effectiveness and accuracy, straightforward quality control, and increased productivity. As a result, precision grinding is applied in many industries today to produce high-quality surface finishes.
What is the accuracy of the grinding machine?
Generally, the accuracy of the grinding machine varies based on the manufacturing project. This is because some rough grinding operations rapidly remove high volumes of metal workpieces. However, in most applications, as a finishing process, the accuracy of the grinding machine stands in the order of +/- 0.000025mm. Experts often apply grinders to remove small quantities of metal anywhere from 0.25 to 0.50mm depth.
What is the cutting speed of the grinding machine?
The cutting speed of the grinding machine is ideal when set between 20 and 25 m/s. For most surface grinding operations, experts use wheel speeds of 30 to 35m/s. But keep in mind that grinder machines can be successfully applied with less than 1m/s speed. Besides, the cutting speed of a 0.2mm grinding pin rotating at 40,000 rounds per minute amounts to approximately 0.4 m/s.
Further, high-speed grinding operations involves using special wheels at cutting speed up to 100m/s. In most cases, high-speed grinding provides increased productivity and efficiency, as well as the improved tool life of the grinding wheel due to reduced grain loads.