roivai wrote:I came up with third method to implement the ramp. I think this minimizes the movement needed for the ramp. On the other hand there is a sudden direction change in the middle of the ramp, which may or may not affect surface finish on that spot.
I'm a mechanical engineer and I work sometimes in a very busy machine shop. I think you're over-thinking this ramp operation. Ramp entries are great, but the first consideration is what ramp angle can your cutter handle
. This is specified by the cutter manufacturer, and you respect it or you damage your cutter.
So, from this standpoint, by trying to compute this angle in software based on the requested Z level plunge depth, you take away all the certainty required by the machinist to respect the tool capabilities and specs, and you force him/her to pull out a calculator to make sure your software isn't going to ruin the cutting tool.
Please let the machinist specify the max allowable ramp angle, and the depth they want to ramp down to. This should be specified as the entry method for a pocket operation. Or allow the tool definition to include the max allowable ramp angle. 0 angle should mean the tool isn't designed for center cutting (plunging cuts).
Modern machining practices are typically shifting toward getting down to a deeper Z level as quickly as possible using a helix or linear ramp operation, then using more of the flute length of the cutter to make shallower passes at the pocket. Depths can be as high as 3/4 - 1" for a 3/4" diameter cutter, depending on the material.
For outer contours/profiles the a similar method is becoming more and more main stream. The cutter starts at a Z level that allows the flutes full engagement in the material, then makes as many passes as possible at this depth. Then the cutter moves UP to the next highest Z level and make as many passes as possible. It's the best for rapid material removal, the best for tool life, and the best for machine life (fewer passes to take away a given amount of material means less machine wear, and the spindle load you can choose based on the cutter engagement (step over as a percentage of cutter diameter.)