Thread: It's begun....

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  1. Just for giggles I set up my machine to where it stalled and then backed it off. Now this is a rough set up and I have NOT gone back and tuned the drives so that would change things as well. Given that I was able to get x(x/c) axis up to 17m/min V with 450mm/sec^2 A; Y axis was gotten to 11m/min V with 350mm/sec^2 A and Z to 7.5m/min V with 250mm/sec^2 A. Let's just say that is a bit scary in speed.
    -Michael
    CAD software Shark Pro v10, Also Aspire v9.0
    CAM Software Aspire v9.0, CamBam v1 beta12
    CNC Machine: http://www.mycncuk.com/threads/3661-...Second-machine
    3D printers: 2 x Prusa MK2S soon to be 2.5's and 1 x mini Delta (180 x 180)
    Work with Solid Surfaces, Acrylics, Woods, Foamboard, PLA, ASA, PMMA
    Work Computer: Lenovo D20, K4000, Tesla C2070, 64GB RAM

    www.marino-customs.com

  2. #92
    Wow - effective limit switches are a must at those speeds I expect ;)

    Even 4m/min was hairy compared to what I've been used to previously when I tested it last night.

    Oh and a quick question or two: I'm running the same test job "cutting air" to see what progress I'm making as I make mods etc. to the machine and I notice that whatever max speed I set the motors to is what the test run seems to use as its rapids - I'm assuming that's normal behaviour?

    The other thing is when I first power up and load MACH3 the motors always seem to need one axis setting up in MACH before they "remember" the settings from the last session?

  3. #93
    Hi All,

    Quick update (no pics or vids yet).

    Last night I completed the mechanical option for running two ballscrews (I still have parts for plan b if needed), by adding some extrusion bracing and additional bearing to the long "bendy" extension on the back of the 2nd ballscrew. Alignment was surprisingly easy, as it was a case of using the already aligned ballscrew and using a transfer punch to mark, drill and tap the new bearing mounting holes. Things are much more sturdy there now.

    I have also added a 3rd pulley mounted on more extrusion and an axle, which I can adjust up and down to increase or decrease tension on the belt (better than what my car engine uses methinks :) ).

    So ran some tests - 4,000mm/min was no problem at all, so upped it to 6,000 mm/min and its still fine, but getting quite scary at that speed (I'm wondering if I should back off of 500mm/s/s acceleration?).

    I'm going to start some cutting jobs, once I have solved my VFD issue (see other thread in Electronics section) and then its back to the feeds and speeds learning curve :)

    Cheers


    Chris

  4. #94
    Quote Originally Posted by Washout View Post
    (I'm wondering if I should back off of 500mm/s/s acceleration?).
    No, you want to increase the acceleration if anything. I run my machine at around 1m/s^2, so twice what you've set. Part of the reason m.marino got such high feeddrates in post #91 is that the acceleration was set very low, and it's a compromise between high acceleration and speed.

    For example, in this video I set the acceleration lower and put a bigger pulley on the motor, and got 60m/min:
    https://www.youtube.com/watch?v=k3MG7ww49A8
    ... but it's not terribly useful.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  5. #95
    Love those Ball nuts

  6. #96
    Quote Originally Posted by Jonathan View Post
    No, you want to increase the acceleration if anything. I run my machine at around 1m/s^2, so twice what you've set.
    Be very careful here because while Jon's right acceleration is useful it's also the biggest cause of missed steps.!! . . . .6mtr/min and 500m/s/s on 5mm pitch screws is not unreasonable speed for first use and unless your doing lots of 3D work or lots of short moves then it will be fine for most work.

    Like Jon's says it a compromise of velocity or Accel so if your happy 6mtr/min then wind the acceleration up until motors stall and then back off 10-20% and you should be fine.

  7. #97
    Yes, clearly if you set the acceleration higher you want to test the system thoroughly to make sure the motors wont stall. After doing what Jazz suggests, I suggest running some code from here:

    http://www.mycncuk.com/forums/gcode/...or-tuning.html

    Then you can change from 'should be fine' to almost certainly fine.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  8. #98
    Quote Originally Posted by Jonathan View Post
    Yes, clearly if you set the acceleration higher you want to test the system thoroughly to make sure the motors wont stall. After doing what Jazz suggests, I suggest running some code from here:

    http://www.mycncuk.com/forums/gcode/...or-tuning.html

    Then you can change from 'should be fine' to almost certainly fine.
    That's handy Jon not seen that before and with G61 exact stop mode at G0 speeds with high acceleration it will double to test of how anchored the machine is.!! . . . . . Again careful has with high settings the Bloody thing will try to walk off. . Lol

  9. #99
    Some progress tonight, whilst I had some "workshop time".

    I decided to do a complete re-wire of the VFD a. to give me some more space with the machine and b. to ensure that the old stuff was not at fault. I also replaced the RCD in the workshop and now rely on the RCD at the consumer unit which feeds the barn/workshop where its split off from the main house supply.

    The VFD fired up first time and still had my old settings in it, which was nice. So I then ran a quick 2D job on some 6082 aluminium, which was very light work i.e. one central 3mm drill mark at 0.1mm deep and then 4 surrounding 6mm "dowel hole" marks at 2mm deep using ramping. Used a 3mm 2flute carbide bit at 16800rpm and 800mm/min. The job itself ran a treat apart from 3 spurious e-stops (tried a debounce setting in MACH3 of 1000 and 3000, but still had a phantom e-stop). I'll have to check earthing continuity on all the CY going back to the control box, as I know my spindle is earthed back to the VFD and the CY carrying the spindle cables is also earthed at the VFD end only i.e. no loop.

    Interestingly I checked continuity/resistance from the spindle to various parts of my machine and I'm getting negligible readings from the spindle, through the gantry and all the way to the main frame.

    Still some progress and light possibly at the end of the tunnel - at least the job I did complete showed very little grumbling from the tool and ripped through what it did have to do, with nice chips, which gives me some hope that I can start doing something other than work on the machine and make the machine do some work for a change ;-)

    More as I get time....


    Chris

  10. #100
    Another quick update:


    I still have spurious e-stops, which I thought I might get rid of by running the VFD off of a circuit in the workshop which does not go through the dado trunking next to the control box supply, but to no avail. Also checked all my earthing for the control cables and that is OK i.e. CY shielding going back to the control box star point, with good continuity. Also tried Mach3 de-bounce settings up to 3000. Only thing I have left I think is I replaced a big chunky, but very long (3mtr) parallel cable with a shorter one, so will switch that back to see if there's an improvement.


    On the bright side, to do the testing for the spurious e-stops I ran a job in beech block just to try and the following pic resulted, which despite the e-stops probably losing steps when incurred, is at least something and came out nice and clean apart from where the wood won't hold the very thin details. The 3mm end mill went through the wood like it was not even there (ran at 18600 rpm at 800mm/min on a 3flute), so aluminium next :-)
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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