Authored by Nitesh

CNC gives significant design flexibility but there are some restrictions in it. These restrictions are primarily related to tool geometry and tool access, and they are associated with the fundamental mechanics of the cutting process.

Tool geometry

The drills and end mills most frequently used for CNC cutting have a cylindrical shape and a finite cutting length.

When the material is removed from the workpiece, a machined item receives the tool’s geometry. For instance, no matter how small a cutting tool was used, the inside corners of a CNC item will always have a radius.

Tool access

The cutting tool approaches the workpiece straight from above to remove the material. CNC machined features cannot be accessible in this manner.

When machining features with a high depth-to-width ratio, tool access becomes a problem. Tools having a long reach are necessary, for instance, to reach the bottom of a deep hollow. The end effector will have a greater range of motion as a result, which raises machine chatter and reduces the possible precision.

Essential details for creating CNC design 

  • Cavities and pockets
  • Internal edges
  • Thin walls
  • Holes
  • Threads
  • Small features
  • Tolerances
  • Text and lettering

CNC machine setups and parts orientation

One of the primary design constraints in CNC machining is tool access. The workpiece needs to be turned several times to access all surfaces of the model.

The machine must be recalibrated each time the workpiece is rotated, and a new coordinate system must be established.

Machine installations should be taken into account when planning for two reasons:

  • The total number of machine sets influences the cost. The item must be manually rotated and realigned, which extends the machining process.
  • Two features must be machined in the same arrangement for the relative positional precision to be at its highest. This is due to a slight inaccuracy introduced by the new calibration step.

CNC machining undercuts

Because parts of their surfaces are not readily accessible from above, undercuts are features that cannot be machined using conventional cutting tools.

T-slots and dovetails are the two primary varieties of undercuts. Undercuts are machined using specialized tools and can be single-sided or double-sided.

A horizontal cutting blade is joined to a vertical shaft to form T-slot cutting tools. An undercut can have a width of 3 to 40 millimeters because it is more likely that the right equipment is already accessible.

Drafting a technical drawing

  1. Orthographic views should be placed in the drawing’s center after determining which views are most crucial for your component.
  2. Add segment views or more in-depth views.
  3. All of the views should include building lines.
  4. Your drawing should have dimensions.
  5. List each thread’s position, dimensions, and length.
  6. Add additional tolerance information for any features requiring a higher level of accuracy than the default tolerances.


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