Leadin Moves.

[blowlamp]

Hi again.
Just checking out a few things in v2 while Robert looks at my problem with v3 and I'm wondering if MeshCAM has a facility for sloping Leadin Moves, as well as a straight plunge into the cut. I can't see anything in the Toolpath Display that looks like them, so I wonder if this might be something for the future or if it is deemed to be unnecessary?
My other CAM program, CamBam, (which for those that haven't tried it is excellent) outputs a mixture of lines and arcs for its 3D Profile function and I'm just curious as to why MeshCAM doesn't also use arcs in its strategy - although I can understand that by following each facet of the body, MeshCAM would naturally create straight lines. I find the comparison very interesting and hope Robert can find a solution so I can try v3.


Martin.

[blowlamp]

Does anybody have a view on this?
I find it's a required feature to stop smaller tools breaking and putting unnecessary strain on the mill. It also means you can use non centre cutting tools.

Martin.

[Randy]

Martin, since MeshCAM is designed to machine general 3D shapes, you must assume you'll need to use center-cutting endmills or the crests of the shapes won't be properly machined. I'm not sure what you mean by leadins, because on both parallel and waterline finishing the cut starts on the periphery of the shape. Those are both considerations for 2.5D machining, but in my experience (using down to .009" endmills in brass) not a factor in MeshCAM's 3D machining.

Edit:You do have a point about the roughing moves, Martin. They do plunge straight into the material. But I tend to forget about that because I haven't bought a non-center-cutting endmill for probably 10 years...

Randy

[blowlamp]

Hi Randy.
Thanks for your reply, but I'm afraid I don't find the straight plunge to be a very happy experience compared to a gentle ramp into the part - even with centre cutting endmills. My milling machine isn't particularly large, but it is quite heavily built for its size. Despite that, it's still possible to see things 'move' as the cutter sinks into the work during a straight plunge cut. On the other hand, ramped in moves are a joy. No twist or strain, just steady cutting. I would definitely vote for the inclusion of Leadin Moves in MeshCAM, at least as you say, at the roughing out stage.

Martin.

[Randy]

On the other hand, ramped in moves are a joy.

No argument there, Martin. I use 10-degree ramp in SheetCam and it is nice and gentle. But in small cavities there are extensive machinations of the toolpath to achieve that--sometimes ramping 4 or 5 times back and forth along a small path to achieve the depth before proceeding with the level. And I use pretty conservative stepdowns--1/5 the cutter diameter in brass and aluminum, 1/2 the cutter diameter in plastics. It would be nice for Robert to do ramping entries, but given the generalized 3D geometry (as opposed to exclusively flat-bottom pockets) it would probably be a massive undertaking. But I shouldn't speak on Robert's behalf--he's the programmer, I'm just a user...

Randy