Thread: My Cnc build

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  1. #21
    Hopefully the last lot for now...

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  2. #22
    Well i think that's it for now...i have tried it out and it works but the top rail slightly binds or stops and occasionally shakes...if i tune the motors to different speeds/feeds it does stop but i think the linear bearings are too close together and the Z axis is too high/big for the bearing position, so i will be putting another square section between the two already there.
    Hopefully this will make it have a larger surface area to run along if you know what i mean...
    There is a water table going in for plasma and i have just bought a 3.3hp perske spindle for routing etc. Pictures to follow.
    I also have a few videos of it working and will post them if it helps explain the problems mentioned here...
    So hopefully i will have some feedback on my design whether it be praise, upgrades, alterations or criticism.
    Cheers for now Tommy

  3. #23
    thanks for all the pics!. keep them coming. Shame you live such a mission away, you seem to be of the same cast!.

    well done looks like you have been quite busy

    surely that rack and pinion drive on the x shoulders will need reducing via some kind of pulley or gearbox as 1:1 resolution on those steppers wont make a very high resolution machine?

    im sure my big machine, is 12:1 drive

    matt
    Last edited by kingcreaky; 06-08-2015 at 08:56 AM.

  4. #24
    Hello All

    I have just cut the new square section to go into the y axis to expand the surface area for the z to travel along and hopefully be putting that in this week and get rid of a few gremlins there.
    I have tried it out and it works in virtual mode but doesn't seem to know where it is in real mode...have been doing a lot of research in this department on the net and think it is the relationship between homing and machine co-ordinates but will fiddle with that once the y axis is complete and i have eliminated them few problems there first.
    The perske spindle is a monster and it rips through wood like butter but obviously no good if i cant control it.

    Kingcreaky, thanks for the reply and you mentioned reducing the x axis....is this a solution only if my steppers and the controls havent got a good enough resolution?

    It does go very slow to extremely fast depending on the settings.

    This is my first build and i am learning enormous amounts which believe it or not, i am enjoying.

    Pictures to follow as i will have to reduce the size.

    Cheers for now Tommy

  5. #25
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  6. #26
    Quote Originally Posted by Skiprat View Post
    Kingcreaky, thanks for the reply and you mentioned reducing the x axis....is this a solution only if my steppers and the controls havent got a good enough resolution?

    It does go very slow to extremely fast depending on the settings.
    Cheers for now Tommy
    Due to a lack of response of any more concise, studious, or literate members I shall do my best to try and explain. However Id urge you to check this explanation before taking it as gospel.

    assuming your gantry is being driven by 1 stepper either side, each stepper direct driving a cog running on the rack.. Il assume that one turn of the cog, will move the gantry about 1" or say 25mm. Im unsure of exactly why, and this is the basis of my argument, so Il hold my hand up if im wrong, but although the stepper drivers allow you to go to a crazy resolution (ie say 3200 steps per revolution) its not wise to be running in this setup. Ive always been advised to set them to something like 800 steps per rev. This maybe because all my machines have always ran direct off parallel port and I see you have a smooth stepper.

    so, assuming one revolution of your drive cog, moves 25mm along the rack. that means, when your setting up mach and you have to tell it your steps per mm your figure is going to be

    800 / 25mm = 32 steps per mm

    essentially, the greater you can make the steps per unit, the greater the resolution of the machine... but of course, lower top speed etc


    hence my comment, I would expect to see that pinion cog being driven by a belt. and the the belt changing the ratio of the drive from 1:1 to something like 12:1

    just bear this in mind, its not necessary a show stopper.

    Love the pictures though... keep them coming

    matt
    Last edited by kingcreaky; 10-08-2015 at 08:36 AM.

  7. #27
    Been looking in my draws and i have loads of bearings, cogs even belt driven spares. I could build some of my own reducing plates but very amateurish on the cad cam side of things yet. Unless someone has the dxf, swg files for me to use or pay for, it might be good for me to buy some premade.

    I have looked all over for rack and pinion drive plates but most seem to be in the USA, does anyone know where to buy any reducing motor cog plate "thingies", in the uk as i am not sure of the right wording for them?

    If i can buy some and get my machine working, then i think it gives you more incentive to build other things and probably more accurate as well.

    Cheers Tommy.

    This is what i am sort of looking for.

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  8. #28
    Thanks for that Matt

    I think i get your idea and will do some looking in my shed for the relevant bits and bobs and see what i have.

    Cheers Tommy

  9. #29
    D.C.'s Avatar
    Lives in Birmingham, United Kingdom. Last Activity: 05-01-2016 Has been a member for 4-5 years. Has a total post count of 326. Received thanks 30 times, giving thanks to others 24 times.
    For the gears & belt, http://www.beltingonline.com/ comes up a lot on this site as a good supplier.
    For the adjustable plate, figure out what you need and post an RFQ, I'm sure someone will be willing to make some for you.

  10. #30
    Quote Originally Posted by Skiprat View Post
    Thanks for that Matt

    I think i get your idea and will do some looking in my shed for the relevant bits and bobs and see what i have.

    Cheers Tommy
    feel like ive pi$$ed on your fire now chap, sorry.

    if your anything like me, you wont want to wait around getting plates cut for you...

    if it were me, id buy some toothed pulleys from the place suggested above, or bearingstation or something.

    get something like this say 10mm

    http://www.ebay.co.uk/itm/10-12-15-2...item4d32dc19cd

    get some round silver steel for a shaft...

    http://www.ebay.co.uk/itm/Silver-Ste...item3f2523697b

    put your pinion cog on one side of the shaft

    and a big ass belt pulley on the other.
    http://www.bearingstation.co.uk/Prod...y_5mm/725M25PB


    then drive the big pulley via another smaller pulley oo your stepper?
    http://www.bearingstation.co.uk/Prod...y_5mm/125M25PB

    get me?
    Last edited by kingcreaky; 10-08-2015 at 10:20 PM.

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