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Plunge rate

Plunge rate in CNC routing is the speed at which the router bit moves in the Z-axis when it is driven down into the material when starting a cut.

It is measured in millimetres per minute (mm/min) or inches per minute (IPM).  

The ideal plunge rate will vary depending on the bit used and the material being cut, but it is always important not to plunge too quickly as this can damage the tip of the cutter.

Speed

Speed or spindle speed is the rotation speed of your spindle motor. 

It is measured in revolutions per minute (RPM).

For use with SmartBench, this value will be in the range of 15,000 - 25,000 RPM.

The ideal speed for your cut will depend on the material and cutter used.

Feed rate

Feed or feedrate is the speed at which the cutting tool moves through your material (in the X and Y axes) 

Feedrate is measured in millilitres per minute (mm/min) or inches per minute (IPM). 

The ideal feedrate varies significantly depending on your material, job, cutter type and cutting strategy. 

Typically, Smartbench uses feedrates in the range of 400-5,000 mm/min.

Stepdown

This is the depth the cutter moves to between each pass. 

The deeper the step down, the more load on the cutter. Too much load on the cutter will result in tool deflection, stalling, or a low feed which can cause material to burn. 

Therefore, we typically recommend doing multiple faster passes at shallow depths, rather than slower deep cuts.

Stepover (for pocketing/clearance toolpaths)

A pocketing operation is used when you want to remove all material with a closed boundary down to a given depth.

When the toolpath begins, the tool will make 100% contact with the material at first, but we can then apply a stepover value to reduce the load on the tool for the remainder of that toolpath.

We typically set this to 50% of the tool diameter.

Ramps

Ramps are used to gradually enter the tool into the material and reduce tool deflection. You can add ramps when generating your toolpath. We recommend that these ramps are kept as short as possible due to the slower feed rate in both the X and Y axis which is brought in from the plunge rate on the Z-Axis. To learn how to do this in Vectric click here.

Leads

Leads allow the tool to enter and exit the material on a segment that is not part of the original tool path vector, away from the finished part. This can be used to maintain accuracy and avoid leaving witness marks on the finished part. To learn how to do this in Vectric click here.

Finishing passes

Finishing passes are used to get the best accuracy and increase the quality of surface finish. Finishing passes are usually done at full depth to get the best finish. We have an article here which outlines how to add finishing passes to your job file. 

Direction - climb vs conventional

Picking the right cutting direction leads to less tearout (material breaking away from an intended surface) and a cleaner finish. The correct direction is often defined by the type of tool you are using:

• Conventional cutting is recommended for downcutters. This is the same direction you would use with a hand router.

• Climb cutting is recommended for upcutters.

• We have more guidance on which one to choose on our material profiles

Conventional Milling

When the cutter is doing the deepest part of its cut, it is rotating against the direction of the X/Y travel (and is cutting least efficiently).

Note how the width of the chip starts from zero and increases as the cutter finishes slicing.

Climb Milling

When the cutter is doing the deepest part of its cut, it is rotating with the direction of the X/Y travel (and is cutting most efficiently).

Note how the width of the chip starts at maximum and decreases.

Offset vs raster strategies (for pocketing/clearance toolpaths)

  

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