Adaptive Control in CNC : What is it, and how does it work ?
Adaptive control in CNC machines is the continuous monitoring of cutting load and automatic adjustment of cutting feed rate based on the load.
During machining, the cutting load may suddenly increase because of local hard spots in castings or variation in the height of raw material. The load also increases as the tool wears out. This is how adaptive control works: You set a normal load level for an operation. If the load increases, the feed rate reduces to bring the load back to the normal level. If the load reduces (e.g., because the raw material is less than what the program was written for, or there’s a gap in the casting), the feed rate increases.
You typically set these parameters for adaptive control:
– The normal spindle load in the operation
– Lower and Upper limits of feed rate. The adaptive control logic will increase or reduce the feed rate within this range, and not go beyond the range.
– An ultimate power level. If the load increases to this level in spite of the feed rate being reduced to its lowest set value, the machine generates an alarm or stops. All values are set as percentages. The normal load is a percentage of the spindle motor’s rated max. load, the ultimate load is a percentage of the normal load. Feed rate limits are percentages of programmed feed rate.
The feature is usually an option on controllers, and not all controllers may have it. Adaptive control has been around for a few decades, and is not some hot new technology. I’ve used it way back in 1985, as a young lad of 25. I used to program a Mitsui Seiki HR7 HMC with a Fanuc 6MB control, that had adaptive control. The parameters were programmed through G codes in the program. Today’s controllers allow the parameters to be entered through the screen interface itself.
Disclaimer: This info is based on my own experience of using adaptive control in CNC machines 3 decades ago. I checked on the web and could not find any current info on it. I also asked around, and found that very few people actually use it. So pardon me for any goof ups here, and please feel free to add any more knowledge that you have as a comment, so I can add it to this post.
