What is successful ramping?
Linear ramping is a commonly used, efficient way of approaching the workpiece when machining closed slots/pockets/cavities, and it eliminates the need for a drill.
Linear ramping is defined as simultaneous feeding in the axial direction (Z) and in one radial direction (X or Y), i.e. two-axes ramping.
Circular ramping (also called helical interpolation, spiral interpolation, orbital drilling, etc.) is a simultaneous movement in a circular path (X and Y) together with an axial feed (Z) at a defined pitch, and also an alternative to drilling.
Circular ramping is always preferred to linear ramping (full slotting), because helical interpolation is a much smoother process as the radial cut is reduced. It allows for pure down-milling, and provides better chip evacuation. An anti-clockwise rotation ensures down-milling.
Two axes ramping – linear
How to apply ramping
A demanding cutting process
There are three cutting processes that occur simultaneously during the linear ramping operation:
1) Periphery cutting with the leading insert.2) Bottom cutting with the leading insert.3) Bottom cutting with the trailing insert.
The cutting forces are both axial and radial.
There is also added stress on the tool due to full slotting, which means that
ae=Dc, creating large radial forces and long chips.
- Reduce feed to 75% of normal
- When slot milling is performed directly after ramping, it is important to continue at a lower feed, for a distance that corresponds to the cutter diameter, until the trailing insert has stopped cutting
- Use cutting fluid to help with chip evacuation
- Reduce the tool radius to reduce the area of contact
- Linear ramping should be limited to narrow slots less than 30 mm wide, if access for circular ramping is limited
When ramping for several passes to produce a deep slot, productivity can be easily increased by ramping in both directions (progressive ramping) instead of ramping in only one (single pass ramping).
Note: When feeding the cutter at the maximum ramping angle, it must be lifted distance h before changing direction. This prevents damage to the central part of the cutter body.
Single pass ramping.
Tool path correction
Progressive ramping at maximum ramping angle.
Insert radius affects maximum ramping angle
The curves in the diagram are valid for minimum and maximum radii. For intermediate radii, please interpolate.
= Insert size 22
= Insert size 16