What is Centerless Grinding?
Centreless Grinding is a round cut operation, in which a product is placed between two discs, supported by a ruler. One disk (the control disk) causes the product to run and ensures that the higher speed of the other disk (the grindstone) is never overtaken. A constant circulation speed is important. The distance between the two discs determines the diameter (grinding size) of the product. This distance can be adjusted extremely accurately (μ range).
Advantages of Centerless Grinding
- High level of automation – saving time and maximising productivity.
- Short set-up times, hence flexible.
- Accurate: small tolerances achievable; because the positioning inaccuracy of the grinding disc to the control disc is half with respect to the positioning of the grinding disc during circular grinding.
- Aligning of product is not applicable.
- Thin, needle-shaped products easily sharpened (control disc and support line eliminate risk of bending).
- Large machining capacity: machines for Centreless Grinding have high capacities (up to 40Kw).
- In the grinding disc, earlier shapes can be made, so that several diameters can be sharpened simultaneously.
There are two techniques:
Centreless Thru-Feed Grinding
Thru-Feed Grinding is used for cylindrical products, where the largest diameters are to be ground. Because the control disc is at an angle relative to the grinding stone, the product is pulled from the front to the rear between the discs. This technique enables products to be added and removed via a conveyor belt, enabling a high degree of automation. If the product so allows, several machines can also be connected in a chain.
Product specifications
| Products are made with the following specifications: | |
|---|---|
| Grinding diameter | Ø 0.3 - Ø 60 |
| In certain circumstances | Ø 100 |
| Lengths | Theoretically unlimited |
| Tolerance | In µ range |
| Roughness | < Ra 0.1 and < Rt 1 |
| *) In deviation from this, there are probably more possibilities | |
- Grinding disc
- Controlling disc
- Product
- Supporting ruler
- Feeding channel
Centreless In-Feed Grinding
The advantage here is that the eccentricity of the diameters is nil. In-feed grinding is used for products with multiple shapes and / or diameters. The two disks are placed horizontally to each other. Products are laid vertically between the discs. The discs then move towards each other by means of a carriage, to achieve the required grinding size. Products may be manually inlaid; larger volumes may be placed in series, by means of a portal loader.
The image opposite shows two diameters being sharpened during the same operation.
Product specifications
| Products are made with the following specifications: | |
|---|---|
| Grinding diameter | Ø 0.3 - Ø 30 |
| Lengths | 1,000 mm maximum |
| Length grinding diameter | < 350 mm |
| Tolerance | In µ range |
| Roughnesses | < Ra 0.1 en < Rt 1 |
| *) In deviation from this, there may be more possibilities | |
- Grinding disc
- Controlling disc
- Product
- Supporting ruler
