CNC: Are you cutting optimally ? Your CNC turning chips can tell you !
Next time you’re in the shop floor, just look at the CNC turning chips. They can tell you whether your machine is giving you a proper return on investment or being underutilized. The shape and size of chips can give you a rough idea of whether the correct cutting parameters are being used.
Width=Depth of cut. Thickness=Feedrate
The thickness of the chip is (almost) the feed rate.
Chips are not breaking ? The feed rate is too low.
The ideal chip is up to 40 mm. long, shaped like a 6 or a 9. If the machine is turning out long chips, the feed rate is too low. Half the feed rate means twice the cycle time. Long chips also mean machine idle time to clear the chips. Look at the tool manufacturer’s catalogue and find out the correct feed rate for the insert that is being used. This post tells you how to determine the feed rate range for proper chip breaking : https://cadem.com/cncetc/cnc-turning-chip-breaking/
The width of the chip is the depth of cut If the spindle load is too low in roughing, the depth of cut is too small.
Increase the depth of cut to the maximum possible. Half the depth of cut means twice the cycle time. The depth of cut is the width of the chip. In rough turning or facing this must be such that the spindle power is being used to the maximum. If the spindle power meter shows less than 100 % in rough turning (on most shop floors it will be less than 50 %), there is scope for increasing the depth of cut. Check what shape and size of insert is being used, and look at the table in this post to get the maximum possible depth of cut: https://cadem.com/cncetc/rough-turning-depth-of-cut/
Pic. and text source: CADEM NCyclopedia multimedia CNC training software.
