13
Dec
Recently, we received feedback from an old customer that the ceramic CBN internal grinding wheel he used had a cracking problem during the dressing process.
The specifications of this grinding head are: 13D-4T-R0.3-R2.778-R1.528-3.4H B150,
the processing material is SCM420, the heat treatment hardness is 58-62HRC, the spindle speed is 45000 RPM, and the cooling method is oil cooling. The following is the detailed process of the incident and our analysis and suggestions on the problem.
1. Moresuperhard trimmed the initial shape of the cbn internal grinding wheel according to customer needs, leaving a processing allowance of about 0.02-0.03mm. After receiving it, the customer carried out final finishing on the machine.
2. During the dressing procession, the customer adjusted the equipment speed to 28000 RPM, the dressing wheel speed to 1000 RPM, trimmed 0.02mm at a time, the depth was 1.6mm, and the grinding head burst.
3. The customer said that the remaining 4 cbn internal grinding were temporarily suspended due to safety concerns.
After comprehensive analysis by Moresuperhard engineers, the possible reasons for the cbn grinding wheel bursting are as follows:
Excessive dressing pressure – The dressing depth of 1.6mm is large and may exceed the bearing range of the grinding head.
Excessive load – The feed amount during dressing is not clearly stated. If the feed is 0.02mm at a time, the load may be too high, especially at high speeds, which is more likely to cause unbalanced force on the grinding head.
Large machining allowance – The machining allowance of 0.02-0.03mm requires precise control of the dressing process, otherwise it is easy to cause stress concentration.
Internal defects of the grinding wheel – If there are invisible cracks or other defects in the cbn grinding wheel, it may indeed explode during the dressing process. But based on the current information, this possibility is low.
Optimize the dressing process
Ensure that the dressing feed is controlled within 0.01mm at one time to avoid excessive pressure caused by high feed.
Determine the type of dressing roller used and its dressing method, and give priority to rollers with smooth contact rather than sharp contact.
Step-by-step dressing
If a large depth of dressing is required, it is recommended to complete it in multiple times, and the dressing depth of each time should be controlled within a reasonable range to avoid high load concentration.
Equipment parameter verification
Confirm whether the speed of the equipment during dressing is suitable for the characteristics of the grinding head.
The spindle speed is recommended to be close to the design value (45000 RPM) to avoid abnormal force caused by reduced speed.
Test the internal grinding wheel before use
It is recommended to conduct a simple test on the grinding head before use to check whether there are any appearance cracks or other abnormalities.
By optimizing the dressing process and properly controlling the parameters, the customer has successfully solved the problem and the grinding head has been able to perform normally. This case reminds us that in the use of high-performance abrasive tools, precise control of process parameters and reasonable matching of equipment are crucial.If you have any grinding and dressing problems,please contact us freely.
