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  • How to do this better the next go around?



    Just finished cutting this and a lot went wrong. I'm hoping to make a few more of these again so I wanted to write out what happened while it was fresh in my mind in case people smarter than me have recommendations for how to make it go better next time.


    First, I wish there was some sort of vectric auto detect that would say, "hey, I see you want to do a profile cut. Some of it requires an 1/8" bit but most of it would be fine with a 1/4" bit for speed. Let me automatically do the 1/8" parts real quick and then you can cut out the rest with your 1/4" bit."


    I used an 1/8" bit for the whole profile cuts of the large pieces instead. Fine, but slow. Anybody have feeds and speeds they like for an 1/8" bit on 1/4" plywood?


    To secure the 2' x 4' plywood (1/4"), I did the blue tape trick with super glue directly onto the spoilboard. It wasn't enough and I had to use raptor nails. I think I should have just used the vacuum but I wasn't sure if it would have dealt with the cupping (and dealing with onion skin is annoying with so many small parts-- wish I had taken the time to make a pressure foot... or wish I had a thunder laser 130w for stuff like this).


    For the pieces that didn't require the radius of the 1/8" bit, I used a 1/4" compression bit. It was fine, but I didn't do tabs and some of them went flying. I had to turn off the dust collector so they wouldn't get sucked in. I guess they weren't affixed as well as I thought.


    I had to redo some parts and ended up breaking FOUR endmills. What happened was an 1/8" endmill broke going full depth (.2795") when it hit a raptor nail. I shouldn't have been doing it at full depth. I swapped it out for another endmill and the same thing kept happening even though I had slowed it way down and taking very light passes. What I failed to realize is that a part of the endmill was stuck on that raptor nail, so it kept breaking whatever the next bit was. Dumb and expensive mistake.


    Anyway, when I make more of these, any tips on what I can improve on?


    Many thanks and all the best.
    Attached Files
    stuart

    2021 Stinger II 4ft x 4ft
    3kw spindle
    servos
    blackbox cyclone
    Jtech 7w pro laser
    air assist
    laser crosshair
    ftc
    recoil ready
    vectric

    Central Texas
  • #2

    Profile cuts are a continuous vector and unlike with the pocket tool path and some others, there's no provision for alternative tools in the same toolpath. So if anywhere along that vector can only fit the .125" tooling, that's kinda what you're going to have to use unless you want to deal with multiple open vectors and the time it takes to change the tooling.

    If you are breaking tools, it's because you are taking too much of a bite on a pass for the diameter of the tool and the speed you are running it. While the smaller tools are more susceptible to that, you can whack a .25" tool pretty easy, too. Rampling can help reduce this, of course. .125" tools I rarely will cut deeper than about .2"/4mm per pass. .25" tooling, I don't go deeper than .375"/10mm and that's with ramping and in material that's not too difficult to cut. There is no "best" speed/feed, unfortunately, so I found from the start that being more conservative at first and then making adjustments upward to find what works for the work one is doing is just part of the learning process. It's not just about speed/feed, either, because chip load is also important to insure the tooling doesn't heat up. Chips take away the heat. I've noticed that many folks run their RPM a bit higher than might be ideal for chip load. Just because you "can" run at 18K RPM doesn't mean that's best for the work. It can also be varied as part of the getting to know your machine process and right from the WinCNC interface while you are cutting. Adjust speeds/feed and RPM "live" to figure out what's working.

    As to tabs...it's something you have to get used to checking on as you're preparing your toolpaths. Tabs are a two step process...turn on tabs and then tell the code where to stick them. If you change a vector, you may lose the tabs even if you have the box checked, so it's important to verify before you create that toolpath. So much of this CNC thing, especially in the beginning, is developing "anal habits" around certain things for everything you do. It's the only way not to miss something that can truly wreck a really nice piece of material. DAMHIKT!!
    ---
    Jim Becker

    SR-44 (2018), 1.7kw spindle, Performance Premium, USB, Keypad, T-Slot table (y-axis configuration), WinCNC, VCarve Pro upgraded to Aspire

    Non CNC stuff...

    SCM/Minimax
    Festool "a good collection"
    Stubby - lathe
    Oneida Cyclone
    more...

    Retired from full time work in the telecom industry 9/2017
    Occasional commission work for others, but mostly for me...furniture/tack trunks/signage/guitars
    Located Bucks County PA

    Comment

    • #3

      Many thanks, I really appreciate it. When I use GWizard to calculate feeds and speeds, it almost always sets my speed at 18000RPM. I guess I need to take a closer look at chipload and compare that with what the manufacturer recommends. I know I can change the feeds and speeds on the fly but I don't think I've ever fooled with the speeds in that way-- just the feeds.

      Wish there was some vectric gadget that would address tighter radii with smaller bits and the rest with larger bits for a profile. Best I found is this and looks like more time than it's worth unless you're doing tons of the same thing.

      https://forum.vectric.com/viewtopic.php?t=37474
      stuart

      2021 Stinger II 4ft x 4ft
      3kw spindle
      servos
      blackbox cyclone
      Jtech 7w pro laser
      air assist
      laser crosshair
      ftc
      recoil ready
      vectric

      Central Texas

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