Chip control and chip jamming present major challenges in all turning operations. Poor chip control can lead to reduced workpiece quality, scrap component, wasted material, shorter tool life and machine stoppage. All factors that negatively impact productivity. The insert nose radius, rake angle, chipbreaker form, cutting speed and feed, and coolant flow all should be considered for successful chip control when cutting metal. In this guide, we will explore CNC chip control tips to ensure quality chip control in conventional operations.
Chip control issues are particularly common within a mass production environment, where the components machined are castings or forgings. Improving chip control comes down to four factors. The nose radius, the depth of cut, the feed rate and the top-form geometry of the insert.
– Insert geometry: Based on the width of the chip groove and the micro- and macro geometry design, the chip will be open or more compressed,
– Nose radius: Smaller nose radius controls the chip more than a bigger nose radius
– Cutting depth: Depending on the workpiece material, a larger cutting depth will influence the chip breaking, leading to bigger forces to break and remove the chip
– Feed rate: If the feed rate is too low, the chip will form on the primary rake and cause the workpiece pile up on the cutting edge, if it’s too high, the highly compressed chip will cause high pressure and tool breakage.
– Cutting speed: Change of cutting speed will affect the CNC chip control.
– Material: A short chipping material is in general easy to machine. For materials with excellent mechanical strength and resistance to creep, the chip breaking is of greater concern.
– Many shops try to be as efficient as possible with conventional turning, using tools with large entering angles and the largest nose radius possible. This helps thin the chips, resulting in increased tool life and productivity. However, this method makes chip breaking more difficult, leading to long, stringy chips that can wind around tools or the workpiece. Stopping the machine to manually untangle the jam greatly slows down production. Thus, using a smaller nose radius than usual can be a successful, though less conventional method.
– Additionally, the operator also needs to factor in the feed, depth of cut and insert selection. Consider selecting a tool with precision coolant. Paired with an insert geometry that offers better chip breaking capability will allow you to increase both the feed and depth of cut resulting in much higher productivity.
– To reduce chip jamming in conventional turning, turn towards the shoulder and stop before the dimension of the shoulder. Maintain the same feed rate for four horizontal cuts. The final vertical cut should be done from outer diameter towards the inner diameter.
– The most common method of chip breaking is to use inserts with special geometries to create stresses in the chip that cause it to break.
– The most efficient operation involves chips breaking toward the unmachined surface, forming a roll that will break consistently. This results in superior surface finishes and operational efficiency while avoiding costly tool damage.