CNC Machining Design for Manufacturing Checklist
CNC machining is one of the most renowned manufacturing methods since it is highly versatile, reliable, and repeatable. It is also compatible with an array of materials, varying from plastic foam to metal. At Creatingway, our product team spends a lot of time and effort on the design for manufacturing. This is to lower the production cost and time of CNC machined parts.
Here Is The Main CNC Machining Design For Manufacturing Tips
Presence of Deep Pockets in the Design
Deep-narrow slots or pockets require longer tools for machining. Longer tools are more prone to breakage and can cause machine vibrations or chatter. Also, it takes several passes to machine deep pockets with increases the machining time and cost. We try to avoid designing parts with deep pockets. If they are unavoidable, we can opt to decrease its depth or increase the pockets’ cross-section area. For instance, pockets must be deeper than 1.5” when using a 0.5” cutter. We may have to change this figure depending on the material and the available tools for your CNC machining design.
Narrows regions are tricky to manufacture since they restrict the size of the cutter. Long and small diameter cutters are prone to chatter and breakage. We try to avoid designing faces or features that are narrow to allow the cutter to easily pass through. If narrow regions are unavoidable, then they must not be too deep. The depth of any feature must be less than 3x the diameter of the tool. The preferred practice is to make wall sections that are greater than 0.01 inches thick. Also, we can employ the use of a shorter cutter with a large diameter to lower the chatter.
Sharp Internal Corners
It is tasking to create sharp internal corners since all CNC machining drills are circular. Instead, the drill bit is likely to leave a pocket of unmachined space. We call this an internal corner radius. It is possible to machine sharpen internal corners through workarounds. This can be through electrical discharge machining which tends to make the entire process more costly. Therefore, we try to avoid sharp corners whenever possible. Normally, a corner radius has to be slightly larger than the cutter. If it is the same diameter as the cutter, then it may cause premature tool wear and chatter. Raising the corner radii above the standard value by as little as 0.005” gives the tool enough space to move around. It can thus follow a more circular path.
Counterbores are examples of inaccessible features that open inside another pocket. They have negative drafts that take longer to the machine if even possible. This is since it is not easily accessible to the cutting tool which thus raises the costs. We try to ensure the cutting tool has full access to all features when doing CNC machining design. This is without getting blocked by another feature.
Fillets on the outside or the top edges of bosses, pockets, and slots need an extremely sharp cutter and accurate setup. Both of these needs can be quite costly to obtain. To avoid incurring these extra charges, we opt to chamfer or bevel the outside edges of features.
Extremely Thin Part Walls
In CNC machining of metal parts, very thin walls increase the chatter. This can compromise the overall accuracy of the machining process as well as the part’s surface finish. In plastics, thin walls are more prone to softening and warping. We thus try to avoid designing parts with thin walls. The preferred minimum wall thickness for metal is 0.8 mm while 1.5 mm for plastics. Though it may be possible to achieve thinner sections without much risk, we must assess it on a case-by-case basis.
Flat bottomed holes need advanced machining operations. This may cause a problem down the production line for certain operations like reaming. We try to avoid creating blind holes with flat bottoms. Instead, we use a standard twist drill to create holes that have cone-shaped bottoms. The cone angle can either be 118 or 135 degrees.
The Ability of the CNC Machine Drill to Enter and Exit Easily
A drill tip may tend to wander when it comes into contact with the material’s surface. This is especially the case when the surface is not perpendicular to the drill axis. Additionally, uneven exit burrs at the exit hole make removing the burr difficult. To ease entry and exit of the CNC machine drill, we avoid CNC machining design holes featured with start and end faces that are not at a right angle to the drill’s axis.
Designing for manufacturing serves to accelerate the CNC machining process and lower operating costs. It also raises energy efficiency and aids product teams in creating clean and functional parts. The above checklist helps ensure our designs are right on track. Working with a top-notch manufacturer like Creatingway can offer more nuanced insights. Contact us now if you have any inquiries.
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