CNC Machining is critical manufacturing process for producing a variety of accurate parts. All manufacturing procedures have certain limitations. The limitations are about what features they cannot deliver. In this post, we will look at the limitations of CNC milling machining inside square corners. Moreover, we will look at various options available to product designers and engineers.
What is CNC machining?
CNC (Computer Numerical Control) machining includes a rotating cutter. The rotating cutter removes the material from a workpiece in CNC. We can call this a subtractive process. The cutter follows the path of a CNC program. To make CNC programs, industries use CAD and CAM software.
Can a CNC milling machine cut the rectangular shapes?
The answer is no; a conventional CNC machining method cannot cut rectangular cavities. Yet, there are procedures to redesign your component to resolve this problem. First, we need to understand the ‘Inside Corner’ problem in detail. Further, we have to look at procedures to machine square corners.
Understanding the problem of inside corners:
The cutters have a circular cross-section that we use in CNC Machining. The cutting tool in CNC milling must rotate to provide the cutting mechanism. Due to this combination, a circular cutter can’t make a precise square inside the corner.
It is necessary to differentiate between external and internal corners. It is effortless for CNC milling to create square corners on external. The reason is the cutting tool can contact all aspects of the corner.
Yet, square internal corners are unfeasible to create for CNC milling. The path that cutter follows will leave a certain amount of the corner unreachable. The radius of the cutting tool in CNC milling determines this amount.
There are many reasons that a rounded corner might be a problem. The problem also occurs while CNC machining a right mounting block. So, let’s suppose this corner is part of a more significant assembly. And another component interfaces or mates with this corner. So, it may be critical that the corner is square and precise.
Before starting production, there is a need to remove all inside square corners. Yet, there are several procedures to redesign your CNC Machined components. These procedures will also improve the machinability of the components. It depends upon the use case of the part and what procedure you will choose.
Including radius corners (fillets):
The easy way to resolve the problem of ‘Inside Corner’ is to include a radius corner. In general, these radius corners are also known as fillets. The procedure to have radius will be the best option for one case. And that is if the corner does not interface with other components.
The size of the cutting tool in CNC machining often decides the size of the fillet. Yet, try to reduce the machining cost by using the largest radius. The reason is the size of the cutting tool partly determines the CNC machining time.
A small cutting tool needs the CNC milling machine to run at a low speed. So, it will take a long time to remove material. Also, if the pocket is very deep, a more extensive and robust cutting tool will need to use. It means there is a need for a large radius. A law of thumb is to keep the corner radius larger than ⅓ cavity depth.
You can visit Prime Technology for the smalles fillet radius range they offer. It is workable to manage the radius range if necessary for some materials. Further, it also depends upon the design and the use case of the component.
What is dogbone, and when do we need it?
Consider that a mating part is square and needs to fixed into a pocket on the component. The dogbones can offer an optimal solution in this case. A dogbone is an expanded or ‘overshot’ cut in a component. It is the best and a simple explanation of a dogbone. A dogbone permits to the machine for the area occupied by a square corner. Consider it as pushing the cutter further into the component on need.
T-bone:
A simple dogbone expands the corner in only a single direction. It is a simple explanation of ‘T-bone’ corner. You have to push the dogbone into the component by at least the circle’s radius. There is, yet, no need to go further than a single radius.
Two direction dogbone:
Another choice is to expand the corner in two directions. Some designers choose to place the circle’s center straight on the corner itself. It is an easy and suitable solution. Yet, it does remove extra material than our need.
Let me explain the most elegant and least noticeable solution. The solution is to center a two-directional dogbone from the corner itself at a distance √ (R² / 2). It permits the complete area to machine occupied by the corner. While not removing any extra material from the component then our need.
Procedure to design the components for CNC machining:
Appropriate part design is critical for engineers to produce parts via CNC Milling. One feature of CNC part design is understanding of machining of square corners. You must take care of wall thickness, tolerances, and cavity sizing.
I will also write about the beginner’s guide to CNC Milling. It will help you with all the introduction questions about the machining processes. Do not forget to do proper research work before starting any project about CNC machining.
Try to approach the professional CNC machining services providers. Professionals manufacture the components through CNC Machining for a wide range of industries. They complete each project with great care and proper planning.
Final Words:
I am sure that you are now familiar with procedures to machine square corners. First, there is a need to understand the problems of inside corners. Then, you have to adopt a proper method as per your need.
