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    Default Recommended toolpath for profile/through cuts?

    I'm quite new to router-based CNC, but am really enjoying writing some exploratory g-code programs to help with woodworking projects. I have a BobsCNC Evolution 4, have a quality 1/4" spiral upcut bit installed, and I feel like I am getting the hang of it. But I have a fundamental question that I can't see to craft the right forum or google query to answer on my own:

    If I use this setup to cut profiles/shapes out of, say, .75" thick hardwood, do I need to worry about making the profile cuts wider than the 1/4" endmill diameter, to clear chips or avoid rubbing? I know that I need to program ramps, and a slow progression of step downs, but I can't seem to figure out whether I can just cut the perimeter in one diameter-width or whether I need to widen? And if I need to widen, whether I should worry about fanciness like trochoidal toolpaths?

    Any help here will be greatly appreciated Best,
    Zach

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    Default Re: Recommended toolpath for profile/through cuts?

    Are you seriously writing programs by typing out lines of code? It is unbelievably laborious but does give a good grounding in the process and the understanding of Gcode. I fear that your spiral upcut tool will cause problems with surface splintering.There isn't normally any need to cut a groove wider than the diameter of the cutting flutes,but you need to avoid the shank rubbing as it will get very hot very rapidly.Which means either long enough cutting edges of a waisted portion below the shank.If you really enjoy 3D coordinate geometry problems you may add ramp entry to your toolpaths or it may be simpler to add arc entry from a point just off the job.Alternatively,you could just find a basic CAM program and let the computer do the work.

    Trochoidal toolpaths are normally used for cutting pockets and do a fine job.Again,you would save much mental toil if you use a CAM program as they can increase the size of a file by several thousand lines-depending on parameters selected.



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    Default Re: Recommended toolpath for profile/through cuts?

    Thanks, routalot. I should have been clearer: I'm not actually writing g-code by hand exactly. I'm using TPL (see https://tplang.org if curious) which is a high level language that allows me to program something like "canned cycles". I program a high level parametric toolpath once, and then I can call it with a single line of code (like squarePocket({width:10.2, height:2.4, depth:1.2}) The software for TPL also includes a simulator that models the cuts and resulting part. I know this is an unusual approach, but it allows me to leverage programming experience I started with.

    If I understand you right, though: you've answered my question in a way that's good news. If I need to make a 10 inch cut that's one inch deep, I can ramp down and cut this 10 inch slot in a dozen passes, and as long as the fluted section of my endmill is more than an inch long. And I don't need need to widen the slot more than a diameter. You said "Which means either long enough cutting edges of a waisted portion below the shank" -- does waisted here refer to the fluted part? And you say "either" -- is there any other option I'm missing?

    Thanks for helping me through this. Best,
    Zach



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    Default Re: Recommended toolpath for profile/through cuts?

    I hadn't encountered TPL previously but I note that it is related to Camotics and that is something I do know a little about.I would still recommend investigating some freely downloadable or demonstration versions of CAM software as it gets easier still.

    My comments about the geometry of the mill should be taken as recommending that either the flutes should be longer than the depth of the material or if not,the shank of the mill should be waisted above the flutes.In either of these situations you won't have the plain shank rubbing.



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    Default Re: Recommended toolpath for profile/through cuts?

    Thank you -- I understand the two options now. And I appreciate your advice to keep exploring CAM options. I am a Mac users, which seems like it means I have fewer good options. I downloaded a trial of MeshCAM, which I will probably eventually license if I can't find anything better. Fusion360 looks nice, but as a hobby user, I don't like the thought they Autodesk could one day change the terms of their cloud subscription such that it became too expensive to continue maintaining my designs.



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    Default Re: Recommended toolpath for profile/through cuts?

    There is a Mac version of Freecad and it has a module called Path which will create toolpaths,including ramp entry and trochoidal clearing.It isn't the easiest or most intuitive thing to use but it does a fine job once you learn it's quirks.There are some helpful tutorials on youtube.There is a clue in the name,it costs nothing and isn't likely to disappear.I don't know how well the Mac version works as I use the Linux appimage.



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Recommended toolpath for profile/through cuts?

Recommended toolpath for profile/through cuts?

Recommended toolpath for profile/through cuts?