What does it mean, grinding burn?
The term grinding burn while grinding is understood as the thermal damage of a ground part caused by an incorrect grinding process. Grinding burn is caused by excessive heat dissipation into the part material. As materials cool as rapidly as they heat, the material undergoes a treatment similar to a tempering process. At high enough tensile stresses, caused by the grinding burn at the outer edges of the material rim zone, the material could undergo micro cracking. Dynamic strain causes the micro cracks to grow into greater cracks which consequently lead to a mechanical failure of the part. Thus, grinding burn is the most common reason for mechanical failure of dynamically strained metal parts.
What are the reasons for grinding burn?
Common reasons of grinding burn are:
- Inadequate supply of cooling lubricant into the grinding zone,
- Occurring of clogging effects on the grinding wheel by grinding chips (grinding wheel surface too finely grained or too finely dressed, porosity is to low…)
- too high infeed value or too high material removal rate (material volume ground per second)
How can you avoid grinding burn?
An adequate supply of cooling lubricant is important to prevent grinding burn during the grinding process. Grinding burn is preventable by using a coolant jet stream with 30-50% of the circumferential speed of the grinding wheel. Needle nozzles (pdf) by Grindaix apply this and efficiently prevent grinding burn on ground parts. It is important to know the pressure directly before the needle nozzle, resulting in what coolant exit speeds and coolant flow rates. Grindaix provides such characteristic diagrams for each of its coolant supply systems. The right use of these parameters efficiently prevents grinding burn while grinding.
Another possibility to avoid grinding burn is to ensure large enough pore space between the grinding grains within the grinding wheels topography to enable the transportation of cooling lubricant into the grinding zone. However, fine porosity is often used to meet surface-finish requirements. Grindings chips which clog between the grinding grains rapidly decreases the porosity. This problem is easily solved using a Grindaix high pressure cleaning nozzle (pdf). The cooling lubricant is then again able to flow in the grinding area to prevent grinding burn.
Avoiding too high infeed or too high material removal rates limits the productivity and is therefore counterproductive. High infeed and low cycle times are possible and guaranteed without causing grinding burn by using the first two above mentioned aspects.
How can you measure burning caused by grinding?
There are many different ways to measure grinding burn. The most common ones are listed below:
- Nital etching
- Barkhausen noise analysis
- Testing of surface cracks by fluorescence effects
Precise measurements of burning can be made using destructive measurement methods such as:
- Analyzing microstructural sections
- Electron microscope analysis
- Testing micro hardness on microstructural sections
Avoid burning by testing grindaix coolant supply systems now!
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Although grinding is a widely used manufacturing process, it is complex and in many places carries the risk of making mistakes. These have an effect on efficiency and component quality in all cases.
Why are components ground and what are the options? For which cases is a grinding necessary? These questions are dealt with in our article "Grinding of components"
A grinding process has to be supplied with lubricoolant, that´s easy to understand. But what are the tasks of the coolant and exactly what are the challenges in the coolant lubricant supply?
The use of lubricoolants always requires the operation of a filtration system that meets the requirements, because the influence of the purity of the cooling lubricant is considerable. Therefore, we have collected what is important in the lubricoolant filtration.