Depth of cut (DOC) is a main cutting parameter in machining, alongside feed rate and cutting velocity. It is the thickness of material removed from a workpiece material in a single pass in CNC machining.
This parameter can significantly affect the quality of CNC-machined parts. It influences tool wear, surface finish, structural integrity of the part, and heat generation during machining.
As a supplier or dealer who regularly makes orders of CNC-machined parts, it is essential to understand the basics and effects of depth of cut in machining. This post delves into the DOC concept, outlining its relevance, factors, and best practices.
What is the Depth of Cut in Machining?
The depth of cut (DOC) in CNC machining refers to the extent to which a cutting tool enters a workpiece in a single pass. This parameter of machining operations is given in mm or inches.
There are limits for the depth of cut depending on the operation. The best CNC machining service providers implement such best practices for to ensure optimal parts.
Importance of Depth of Cut in Machining
Depth of cut is critical in CNC machining because it directly influences tool wear, heat generation, the structural integrity of the machined part, and surface finish. Overlooking it during the CNC machining process can easily lead to poor results or even total loss.
Tool Wear
The depth of cut in machining is a major contributor to cutting tool wear. The best CNC machining service providers know how to counter this, specifically by increasing the cutting edge. Spreading the tool wear in this manner is a notable principle in high-efficiency machining.
Excessive tool wear
Heat Generation
Increasing the depth of cut can markedly reduce machining time, but it can be counterproductive if it is too large, as it can generate too much heat. Therefore, it is important to optimize the DOC in CNC machining so that even with a large DOC, the tool and workpiece are safeguarded from heat effects.
Structural Integrity of The Part
The depth of cut is typically directly proportional to the cutting forces. As the tool digs deeper into the workpiece, the amount of forces subjected to the workpiece tends to increase. High cutting forces can compromise the structural integrity of the part due to heightened chatter and vibrations.
Chatter effect
Surface Finish
The depth of cut has a direct effect on the surface finish of a machined part. Smoother surfaces often go with shallower cuts due to less tool wear and vibrations.
Deeper cuts can produce a range of textures, which are sometimes what is required for both functional and aesthetic value.
Depth of Cut in Different Machining Processes
Different machining processes have their unique way of treating and presenting the depth of cut. The measurements and parameters for depth of cut vary across different machining processes, including turning and milling.
What is the Depth of Cut in Lathe Machining?
In lathe machining, the workpiece rotates, and a stationary cutting tool cuts along the length. The depth of cut in this machining process is given by;
Where d1 = diameter before machining
d2 = diameter of the machined surface
What is Deep Cut in Milling
To understand the depth of cut in milling, an overview of the process is important. Milling is characterized by a rotating tool machining a blank that is fixed on a worktable. If the milling tool diameter is larger than 20 mm, the depth of cut should be 4 times that diameter.
For diameters smaller than 20 mm, a depth 10 times that is adopted.
Factors for the Optimal Depth of Cut
The depth of cut in CNC machining depends on several factors, mainly the cutting tool geometry, cutting tool material, CNC machine rigidity & capabilities, workpiece material properties, coolant, and required surface finish.
The CNC Machine and Cutting Tool
The machine’s power and capability can determine the depth of cut, especially in advanced processes such as 5-axis CNC machining. Rigid and versatile machines produce larger depths than less rigid machines. However, the cutting tool also has to match the capacity of the machine for this to happen.
Material Properties
Workpiece materials have properties that can influence the depth of cut – hardness, toughness, strength, thermal conductivity, and others. For instance, harder materials require smaller DOC and vice versa.
Challenges and Solutions When Setting Depth of Cut
Setting the ideal depth of cut in CNC machining is a systematic process. The common challenges that machinists encounter entail material inconsistency, tool breakage, heat generation, balancing depth against surface finish quality, power consumption, and chip evacuation.
Fortunately, there are proven solutions to these challenges. Let’s see how top CNC machining companies deal with these problems.
Material Inconsistency
Inconsistency of hardness and other material properties can interfere with setting an optimal DOC in machining. A practical solution is to regularly confirm the material properties and adjust the depth of cut settings accordingly.
Tool Breakage
The cutting tool can break or deflect if the DOC is set too high. This problem is expectedly to be more common with the more slender cutting tools. Machinists overcome the challenge by using the right tool geometry and minimizing the depth of cut.
Damaged tools
Heat Generation
Deep cuts accompanied by high feed rates generate significant cutting forces and heat, which can shorten tool life. Investing in quality coolant can safeguard the cutting tool and ensure optimal machining results from the optimal depth of cut.
Coolant
DOC vs Surface Finish Quality
The chatter and vibration caused by deep cuts can result in a poor surface finish. The solution is to find an optimal balance between spindle speed, feed rate, and DOC. Using a machine with quality anti-vibration features is also helpful.
Power Consumption
A CNC machine consumes more power for higher DOC than in shallower depths. Optimizing this angle by operating the machine within its capacity can help manage power consumption.
Chip Evacuation
When deeper cuts must be used, another problem arises – long chips. These can affect tool performance and cut quality if they are not handled properly. Modifying the tool path or using chip breakers can solve this issue.
In Summary
Good management of the DOC is a big contributor to quality CNC-machined parts. As this guide has shown, several factors related to this element need to be addressed for optimal machining results.
The experienced CNC machining team such as ProleanMFG is ready to provide quality CNC-machined parts with the right depth of cut.