Internal Grinding Wheels
Internal Cylindrical Grinding Wheel
- Center Type
- Planetary Type
- Centerless Type
Internal grinding wheels are mainly used to grind the inner surface of cylindrical, conical or other shaped workpieces.
Internal grinding wheel is used to process through-holes, non-through-holes, step holes, etc. on the machine parts. Internal grinding expands the internal holes of the workpiece to precise dimensions and the required surface roughness.
Internal cylindrical grinding wheel usually smaller diameter plane grinding wheel and is widely used in mechanical processing. The dimensional accuracy of machining can reach tolerance levels IT6-IT7. If high precision grinding technology is used, the dimensional accuracy can be controlled within 0.005mm.
Process Workpiece Display
Types of Internal Grinding
It can be divided into the following three types:
Center Type Internal Grinding
When grinding, the workpiece rotates around the center line of the main shaft of the headstock.
Common and universal external cylindrical grinding machines belong to this form.
It is suitable for grinding the inner holes of sleeves, gears,flanges, and other parts.
Planetary Internal Grinding
Cutting- in grinding method, also known as lateral grinding method.
When grinding, the workpiece is fixed and does not rotate. In addition to high-speed rotation around its own axis, the wheel also rotates the center of the hole at a lower speed to achieve rotary feed.
In addition, the wheel also performs the longitudinal feed motion and periodic lateral feed. The lateral feed of the grinding wheel is achieved by increasing the turning radius of the planetary motion.
The planetary internal wheel is mainly used for grinding the parts that have grinding large volume and inconvenient to rotate.
Centerless Internal Grinding
The workpiece is supported by its machined external cylindrical on the support wheel and the pressure wheel on the centerless internal grinding machine, and is driven by the guide wheel to rotate.
This type of wheel is suitable for grinding inner holes of annular thin-walled parts.
Features of Internal Grinding Wheel
Compared with external cylindrical grinding wheel, internal grinding wheel has the following features:
In mechanical processing, the measurement of product is one of the indispensable technology. The same goes for external cylindrical grinding. After external cylindrical grinding, measure the dimensional accuracy, roundness, and cylindricity. At the same time, any defects during measurement should be eliminated.
The internal grinding wheel and the workpiece are in tangential contact, and the contact arc between the wheel and the workpiece is larger than that of the external cylindrical grinding wheel. Therefore, the grinding heat and force are relatively large, and the abrasive particles are prone to dulling, while the workpiece heats and or burns.
When internal grinding, the cutting fluid is not easy to enter the grinding area, and the grinding debris is also not easily discharged. When the debris is in the inner hole of the workpiece, it is easy to cause blockage of the wheel and affect the surface quality of the workpiece. Especially when grinding the brittle materials such as cast iron, the debris mix with the cutting fluid to form the paste, making the grinding wheel blockage and affecting the grinding performance.
The rigidity of the extended shaft of the grinding wheel is relatively poor, which is prone to bending deformation and vibration, and has a significant impact on machining accuracy and surface roughness, also limiting the improvement of grinding amount.
Methods of Internal Grinding
Adjust the position of the wheel before grinding. When grinding inner holes on the universal cylindrical grinder, the wheel contacts the front wall of the hole. The lateral feed direction of the grinding wheel is the same as when grinding external cylindrical. On the internal grinding machine, the grinding wheel contacts the back wall of the hole, making the convenient for the operator to observe the surface processed by the longitudinal grinding method.
Longitudinal Grinding Method
This grinding method is the same as the cylindrical longitudinal grinding method.
When grinding through holes, first select the diameter of wheel and the extension shaft based on the aperture and length of the workpiece. The rigidity of the extension shaft is good, and the length of the extension shaft only larger than the length of the hole.
Cutting-in Grinding Method
When grinding with cutting-in grinding method, the rigidity of the extension shaft is good, and the grinding wheel is easily to be blocked and dullness during the continuous feeding. The wheel should be dressed. A lower cutting speed should be used when precision grinding.
How To Choose The Internal Grinding Wheel
CBN&diamond grinding wheel is an important component of grinding equipment. The wheel plays a crucial role in the grinding the inner circle. When grinding the inner circle, the method is different, and the selection of the wheel is also different.
Selection of Abrasives:
There are mainly the traditional abrasive wheels. Superhard grinding wheel mainly include CBN and diamond grinding wheel. CBN grinding wheel has its own advantages for grinding the materials containing iron group elements. Diamond grinding wheel is suitable for grinding engineering ceramics, tungsten carbide, glass, and etc.
Selection of The Diameter Of Internal Grinding Wheel
The selection of the diameter of wheel is a complex problem. On the one hand, in order to achieve the ideal grinding speed, the diameter of wheel is close to the aperture size. On the other hand, as the diameter of wheel increases, the contact arc between the grinding wheel and the workpiece also increases, causing to an increase in grinding heat and difficulty in cooling and debris removal. To achieve good grinding results, the ratio of the diameter of wheel to the aperture should be appropriate, usually between 0.5 and 0.9.
When the aperture of the workpiece is small, the main problem is the low axial speed of the grinding wheel. In this case, a larger proportion should be used; When the aperture is over 100mm, the circumference speed of the grinding wheel is higher, and the heat and debris removal become the main problems, so a smaller proportion should be taken. If the inner hole diameter of the workpiece is more than 100mm, it should be noted that the turnover rate of the wheel should not higher than the working speed of the grinding wheel.
Selection of The Width Of Wheel
The large width of the grinding wheel is good for improving the surface quality of the workpiece, improving production efficiency, and reducing wear. The selection of grinding wheel should not be too wide, otherwise it will increase the grinding force and cause the long axis of the wheel to bend and deform.
Selection of The Hardness Of Wheel
The contact arc of internal grinding is relatively large, and the heat dissipation of the workpiece is poor. Only by fully utilizing the “self sharpening” of the grinding wheel can the grinding force and heat be effectively reduced. Therefore, a softer grinding wheel should be chosen. The hardness of the wheel is 1-2 levels softer than that of the external cylindrical grinding wheel . When grinding the small holes with longer length, the hardness of the grinding wheel should not be tool low in order to avoid the taper on the workpiece. Usually, the hardness of the internal grinding wheel is medium soft.
Selection of The Shape of Internal Grinding Wheel
The common diamond internal grinding wheel shapes include flat, single-sided concave type. In addition to grinding inner holes, single-sided concave grinding wheel can also for the end face of stepped holes grinding.
Related Products
Performance of 5 Types Grinding Wheels
Type of Binder | Self-Sharpening | Sharpness | Life | Dressing Difficulty | Price |
Metal | |||||
Resin | |||||
Vitrified | |||||
Electroplated | |||||
Metal-Resin |
Diamond VS CBN Grinding Wheels
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