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  1. #1
    Join Date
    Mar 2009
    Location
    Melbourne
    Age
    54
    Posts
    825

    Default Using a CNCEST 6040 CNC Bed Mill/Router - My first foray into CNC

    Over the last few days I have had my first real foray into CNC machining.
    I needed to make up some brass plates to common the terminals on a -48VDC power distribution panel together.
    I've made these before on a conventional mill but its a slow and tedious job as my mill doesn't really spin fast enough for a 3mm endmill.
    A year or so ago my wife bought a 60x40 CNC router with a 400W spindle from ebay with which she planed to make cake decorations, however she never got around to utilising it fully as she does most of the things she needs with a 3D printer.
    When the job came up to make these PDP plates I though of the little CNC router and decided to see if I could put it to use.

    6040CNC Router 01.JPG 6040CNC Router 02.JPG

    The easy part was drawing the simple 3D model using Fusion 360 which I use now and then to model things before making them using conventional machining.
    The hard part (or so I thought) was to go from a 3D virtual model to producing chips on the CNC router.
    Thankfully, Fusion 360 has plenty of great tutorials to assist a luddite like myself and within a hour I had produced some G-code using the Fusion 360 CAM function.
    Initially I used an adaptive clearing tool path which seemed to be the recommended method. This uses helical ramping to establish a pocket then takes a series of curved cuts to extend the pocket to the finished size.
    The CAM package also gives a machining time estimate and lets you do a simulation run of the tool path so you know roughly how it will run in the machine.

    6040CNC Router 03.jpg 6040CNC Router 04.jpg
    The Fusion 360 model and the generated toolpath.

    The router uses Mach3 control software with which I had a passing familiarity but have never used for full on programmed machining.
    First run was with no tool and the spindle a couple of inches off the bed, I pressed the go button and away it went with no erratic or unexpected movements.
    A little drill vice is the only one I have that is small enough to fit under the spindle so I mounted this to some 19mm ply which was then secured to the router bed using four M6 cap screws.
    I cut some 3mm MDF to the same size as the brass stock and did a chicken pass using a 2mm solid carbide four flute endmill which seemed to work fine so the next step was to try it for real.

    The 3" x 1.5" x 1/8" brass stock was clamped in the vice, the spindle set to the required origin then I pushed the go button.

    The tool proceeded along its merry way and was very smooth while doing the helical ramping to establish each pocket.
    When it began doing the circular passes to extend the pocket however the router vibrated a lot but seemed to cope with the load.
    I let it continue to run for a while but decided to stop it about twenty minutes after it became obvious the resulting cuts were very rough and not to the required finished size.
    I had gone with pretty much the default settings when producing the tool path, the exception being to select conventional rather than climb milling, another face palm moment I was later to learn.

    The default toolpath was a full depth cut, combine this with the cutting feeds I had selected, (8in/min at 12000RPM), which in theory should have been ok, turned out to be far to aggressive on the router which lacks the rigidity of a proper milling machine.
    I tried a few more iterations running progressively slower feed rates but while things improved the results were still not as good as I had hoped.

    Things got worse when I hit the return to origin button after stopping a run. While this does indeed return the spindle to its X,Y point of origin, it doesn't withdraw the tool so the cutter was pulled through the brass full depth at 15in/min.
    To it's credit the tool, which was probably only doing 2500RPM, did manage to cut, albeit not following the correct path as the feed steppers slipped under the load.
    Unfortunately the cutting edge of the tool broke as it left the stock.


    6040CNC Router 05.jpg
    My trial and error plate, complete with erratic exit path on the left..

    I only had one 2mm cutter so it was back to the drawing board, well the CAM package, to recalculate for a 3mm cutter, and I took a bit more care in understanding all the different settings.
    This time I opted for a conventional 2D pocket clearing toolpath with multiple 0.020" roughing passes and a finishing pass for each pocket (this is the toolpath shown above).

    Back to the machine with a new cutter, a new tool path and a new piece of stock. Hit the go button and finally success.
    The machine still vibrated a bit but nowhere near as badly as before and the cuts were much smoother and appeared to be on size so I let the program run the full distance and an hour and twenty minutes later I had my first finished plate.

    6040CNC Router 06.JPG
    The stock and the first finished plate.

    6040CNC Router 07.jpg
    Four of the finished plates installed on a PDP.

    All things considered I am pretty happy with the performance of the router and for basic things like this, it did a very good job.
    The cheap import carbide endmills are also extremely good value at around $3.00 a piece.
    Finally, Fusion 360, what more can I say, for completely free software I am again astounded at how powerful and user friendly it is.
    Cheers,
    Greg.

  2. #2
    Join Date
    Sep 2006
    Location
    Australind , WA
    Age
    58
    Posts
    1,277

    Default

    Nice work.
    You are on your way!

    It sure is a steep learning curve but when you get it right, its great.

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