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The Frog CNC Router

Discussion in 'CNC Mills/Routers' started by Neil Rosenberg, Jan 3, 2014.

  1. Neil Rosenberg

    Neil Rosenberg Journeyman
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    I'm sure there's a little, but it's not visible.

    They're far stronger than the wheels, so in that respect they're not the weakest link.
     
  2. Neil Rosenberg

    Neil Rosenberg Journeyman
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    I learned something about Mach 3 this morning that made a *HUGE* difference in cut accuracy. In a nutshell:

    There's a feature in Mach 3 called "Constant Velocity" which when enabled can cause severe and (it seemed) random undershoot at various points in the process. This has been the cause of uneven outlines when doing area cuts or reliefs in almost all of my parts so far. What happens is the initial plunge cuts are at the right location, but any subsequent cuts that approach an edge and turn around would undershoot by as much as 1/16 inch. Big errors, really ugly!

    If Constant Velocity is turned off, all of the errors disappear (yay!) but the motion becomes a bit jerky. Thankfully by setting a few parameters such as "Stop CV on angles > (say 30) Degrees", "CV Dist Tolerance" to a low number (i.e. 2), and carefully adjusting the acceleration ramps of the motors, I was able to turn CV back on. Now the machine operates really smoothly and does not exhibit those errors.

    Thankfully the problem was NOT due to mechanical flexing of the frame/system, and the output is now extremely clean.

    If you're seeing this problem with Mach 3, give CV a try!
     
  3. Hytech2k

    Hytech2k Veteran
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    Not having the CV set right usually causes rounded outside corners instead of being sharp. CV Dist Tolerance tells Mach how far away from the corner it should start slowing down. Can't really say what my settings are right now due to both machines running code but I think my stop CV is set for great than 90 degrees. Tuning the acceleration on the motor especially the X and Y to something along the lines of 15-20 will give smoother results and less shaking of the machine, I think my z is set to around 35 otherwise it slows down 3D cutting.

    Try reducing your bit stepover to 8-10 percent and you'll get very smooth results with little to no lines.

    Looking great though, have you tried cutting any rfl files yet?? I believe I have a few 3D files I can send you if you'd like trying them out...

    Gerald
     
    #213 Hytech2k, Feb 14, 2015
    Last edited: Feb 14, 2015
  4. Neil Rosenberg

    Neil Rosenberg Journeyman
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    Thanks Gerald, all good. Yes I've used a few of the rlf files that came with ArtCAM Express. The photo above is text hovering over one of those reliefs.

    In fact it's relief machining that really showed up the problem I described, with its constant back and forth carriage motion. Every time the tool turned around to go the other way (pre-fix), it would miss the mark. For the longest time I thought it was caused by mechanical issues, but I was blaming the wrong culprit.

    BTW I would never turn down 3d reliefs, here's my email: [email protected]

    regards
    N
     
  5. Hytech2k

    Hytech2k Veteran
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    Great to know it's not a mechanical issue, just a software problem, those are usually easier to fix. Looks great, what bit did you use?

    :) I'll send over a few... I've never used ArtCam, does it support grayscale reliefs also? I have a ton of those as well...

    Gerald
     
  6. Neil Rosenberg

    Neil Rosenberg Journeyman
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    Super!

    BTW I hadn't tried using a grayscale to do a relief cut in ArtCAM Express, but since you asked the question I just tried it. Seems to work really well.

    Let me know how I can return the favor.

    Neil
     
  7. Mark Carew

    Mark Carew OpenBuilds Team
    Staff Member Moderator Project Maker Builder Resident Builder

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    @Neil Rosenberg you have done an outstanding job on this build! Thank you for all the helpful and exciting updates you continue to share.:thumbsup:
    Mark
     
  8. Neil Rosenberg

    Neil Rosenberg Journeyman
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    Thanks Mark, havin' more fun than should be legal :p

    Here's a snap of the latest cut, finally smoothing out the bumps...

    [​IMG]

    This is the cover for my grand-daughter's "treasure box", measures about 8x5 inches.

    Neil
     
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  9. Hytech2k

    Hytech2k Veteran
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    I might just have to take another look at ArtCAM !! Very nice work !! Looks like your using a raster toolpath, if you change it to offset toolpath where it starts in the middle working its way out you'll eliminate the choppy marks around the border..
     
  10. Neil Rosenberg

    Neil Rosenberg Journeyman
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    Thanks Gerald and Justin.

    This is a relief cut, there's a 3d flower behind the text. The only way the stock ArtCAM Express product can do this kind of cut is raster. Delcam (makers of ArtCAM) does have a "Feature Machining" module that you can add to Express that is the best of both worlds (relief in both raster and offset modes) but I'm too cheap to spend the $250 for it, particularly now that I have this workaround.

    I totally agree with your comment -- if I wasn't doing a relief cut, area clear would be way better and quicker, and yes I'd probably use offset as you suggest, and that is included in Express. FYI, in Express even if you do an area clear in raster mode, it always finishes up with a full peripheral cut, so it's still quite clean.

    Justin -- This is cut with 1/8" end mill (roughing) then 1/8" ball with a .008" stepover. The whole thing took just shy of 1 hour.

    Neil
     
    #220 Neil Rosenberg, Feb 15, 2015
    Last edited: Feb 15, 2015
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  11. Hytech2k

    Hytech2k Veteran
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    Oh I see, Aspire handles it a bit differently where the text and relief image become one component, I would rough it out with a .25 ballnose and finish cut it with either a 1/16 or 1/8 tapered ballnose bit... Looks great anyway though !! 1 hour isn't bad at all. The Harley signs I do run .5 hour for roughing and 3 for finish, but no sanding required, just touch up some areas, stain and poly....

    Keep it up Neil, looks great !!

    Gerald
     
  12. Dave Pinchbeck

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    Hi Neil, a great series of hints on how your have gone with your Frog.

    I am just wondering if you have used it for working with soft metals such as Aluminium and Brass, and if so how did it handle it. I am curious because I note the discussions about flexing of the gantry, using the open build extrusions. I am actually resurrecting a stalled build from a couple of years ago where I acquired a lot of 80x80 and 40x80 extrusions which I am hoping to incorporate, rather than buying all new stuff

    Cheers
     
  13. Neil Rosenberg

    Neil Rosenberg Journeyman
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    I haven't tried it yet, mostly because I don't have a suitable bit (o-flute) for cutting soft metals. They're a bit pricey, but I'm zero-ing in on one by Onsrud (63-610 O-flute) that looks pretty promising. When I manage to try it, I'll let you know.

    If I were to do this over again (no offense to OpenBuilds) I would use a much beefier beam for the gantry specifically, and likely go with steel linear bearings all around rather than the wheel approach. If you check out any of the commercial products, this is how the good ones do it. It really doesn't cost that much more, and the stability improvement is huge.

    Best of luck with your build.
     
  14. Hytech2k

    Hytech2k Veteran
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    Try these bits out Neil, I was pretty skeptical but I keep the rpms about 13000, feed 20 and DOC .04 ramping into the cut they work ok. I cut a full set of plates from .375 6061 over the weekend with one bit... Here is the secret i've found to cutting 6061 (brass is easy) direct a compressed air nozzle down at the tip of the bit and when doing profile cuts spray every second pass with WD40... works like a charm but keeping the chips blown out is the biggest thing, otherwise they like to reweld in the cut.

    http://www.ebay.com/itm/111563788736?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

    At 15 bucks with free shipping can't lose and you get 5 !! ;)

    I use bits from ToolsToday as well, pricey but great quality.

    Gerald

    Here are a few photos of my air blast/mister setup on my big machine,

    IMG_0046.JPG IMG_0047.JPG
     
    #224 Hytech2k, Feb 18, 2015
    Last edited: Feb 18, 2015
  15. GrayUK

    GrayUK Openbuilds Team Elder
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    Gerald.
    I've always considered an air blast like yours, but blowing towards, and into, a 1" x 4", slotted vacuum mouth, dead opposite, to take the debris straight away from the cut.
    Two birds, with one stone, so to speak.

    Gray
     
  16. Hytech2k

    Hytech2k Veteran
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    Only problem with that Gray is as the bit moves in different directions chips get thrown out going different ways, it would have to be a hell of a vacuum. Plus I think having one air nozzle is bare minimum, you really need 2 facing in X and Y directions. Profiling parts is where I get the most chip weld, with one nozzle the chips don't get evacuated very well when going sideways to the nozzle direction. Also i'm not too comfortable spraying flammable liquids and having a Vac suck them up, shop vac would probably go boom. :) WD40 does wonders at reducing chip weld and improving the cut quality.
     
    #226 Hytech2k, Feb 18, 2015
    Last edited: Feb 18, 2015
  17. GrayUK

    GrayUK Openbuilds Team Elder
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    That will be back to the drawing-board then. :D
     
  18. Neil Rosenberg

    Neil Rosenberg Journeyman
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    I'd like to find a way to machine aluminum without any "wet" stuff. My table is made out of face cut mdf and will soak up WD40 like a sponge.

    I suppose I could add a removable metal top to the bed, but I'm still concerned about flinging lubricant into everything.

    Maybe I'll build a second machine (that's the ticket!) :ROFL:
     
    #228 Neil Rosenberg, Feb 19, 2015
    Last edited: Feb 19, 2015
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  19. Paruk

    Paruk Journeyman
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    Treat the MDF with a wax to prevent it from sucking up WD40 and the likes. I use liquid beeswax on all work surfaces. To prevent sliding use a bit of salt under the work piece (if you use the vacuum table).
     
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  20. Hytech2k

    Hytech2k Veteran
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    I have the same issue, my bed is 3/4 ply with 2 layers of MDF on top. I just add another piece of MDF larger than the piece i'm cutting, it soaks up the WD40 pretty good and leaves the bed underneath dry... I thought about building a box with 6" walls to to help contain the overspray.

    I spray my bed with shellac after surfacing, but that doesn't last long when you get alot of cuts into it... :)

    LOL i'm thinking of a third machine, maybe a laser cutter.. ;)

    Gerald
     
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  21. Jason Farley

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    While I have yet to finish my CNC router I have cut lots of aluminum dry on mills. You can do it quite easily with the right tool and air blast.

    I typically used solid carbide 2 flute high helix TiN coated end mills. Air blast on the tool to clear the chips and climb milling. Keep the chips light and thin but large in size. I liked curls the size of my small finger nail with a little curl to them.

    Certainly flood coolant is historically preferred in most cases but more and more we were moving to tooling that was cutting dry. This included 3" face mills through pre hardened steel at nearly 300 inches per minute.
     
  22. Hytech2k

    Hytech2k Veteran
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    What are the feeds and speeds your using to cut say 6061 with the 2 flute? I have a few high helix 1/4" end mills designed for milling aluminum but still have issues with chip weld when I cut dry.

    Gerald
     
  23. Jason Farley

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    The old prototrak was not high speed so speeds and feeds were low. Probably much lower than what is typical with the routers used in these OX builds.

    It has been more than 6 years since I regularly ran any equipment so my memory is fuzzy. I did a fair bit of manual cutting in the 1700 to 2200 rpm range and 10 to 25 IPM. This was on mostly 1/2" and 3/4" tooling. probably in the .005" to .007" per tooth chip load range. The production stuff was much higher chip load but we were still running flood coolant on aluminum in the production horizontal mills and lathes.
     
  24. Hytech2k

    Hytech2k Veteran
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    I think that's actually part of the problem, the rpm these routers turn. With common routers it's difficult if not impossible to get your rpms slow enough where you don't have rubbing. Some of us have variable speed routers but even my 3 1/4hp Porter Cable goes only as low as 10,000 rpm, but at a cost, it loses alot of torque. From what I understand usually about 4-5000 or lower is a good range with 1/4 and 1/2" end mills. With smaller bits you can run higher rpms and keep a good chipload, but when using a larger end mill like 1/4 or 1/2 the rpms need to come down a lot or you'll start rubbing and melting the aluminum instead of cutting.. I have found with a 1/8 O flute end mill 13000 rpm with 20ipm and a .04 DOC climb milling works pretty good, no broken bits.

    I use mostly "O" flute end mills designed for higher RPM routers and they seem to work pretty well, just much more costly than a solid carbide 2 flute... I can run these dry on everything but slotting operations (profile cuts) or deep pockets, that's when I break out the WD.. I have seen a few people run 1/4 end mills with just a mister moving fast 24k rpm at 120IPM .06 DOC, but on rigid machines with 10hp spindles.

    Check out NYCNC on youtube, he has alot of good info on milling aluminum... Or Toolstoday...
     
    #234 Hytech2k, Feb 19, 2015
    Last edited: Feb 19, 2015
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  25. Neil Rosenberg

    Neil Rosenberg Journeyman
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    The particular spindle motor I use (DeWalt 611) has variable speed, ranging from around 16,000 to 27,000 rpm no-load.

    As Gerald says, that's a LOT faster than the typical milling machine, changes the dynamic quite a bit.

    Not quite ready to ditch my old manual miller...
     
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  26. Neil Rosenberg

    Neil Rosenberg Journeyman
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  27. Hytech2k

    Hytech2k Veteran
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    I personally haven't but a lot of guys over on Joe's CNC forums have, no one has anything bad to say about them. If I decided to stay with a router I would go that direction, 5000 rpm and the ability to control it from Mach 3 is appealing.
     
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  28. Neil Rosenberg

    Neil Rosenberg Journeyman
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    Just rebuilt my electronics from the ground up. Got rid of the TB6560 (Sainsmart) 4-axis driver board/24v power supply and replaced with a 48 volt power supply driving a Gecko G540. HUGE improvement in accuracy of cut, slew speed and etc. The only downside I can see is that my motors are getting a bit hotter in use. I'll post pictures of the new control box, it's much more professional now, and includes auto z zero and auto spindle relay.

    At this point I'm pretty operational, but still haven't tried cutting aluminum. That's next!
     
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  29. Tweakie

    Tweakie OpenBuilds Team
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    Good move changing to the Gecko G540 Neil :thumbsup:
    If you motors are getting hotter than 60 deg.C then consider changing the current resistors (as per the Gecko instructions).

    Tweakie.
     
  30. Neil Rosenberg

    Neil Rosenberg Journeyman
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    Good point. Next time I'm running a long job I'll put a probe on the motors, see what they're up to.

    60c is pretty warm (140f), don't think it's that high but I'll see... It's easy enough to change the resistors.

    Thanks
     
    #240 Neil Rosenberg, Apr 18, 2015
    Last edited: Apr 18, 2015

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