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size speed etc ox

Discussion in 'Concepts and Ideas' started by peter28, Oct 13, 2016.

  1. peter28

    peter28 Well-Known
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    I have some questions about the ox cnc :

    I am thinking of buying a ox cnc but i am not sure about a 1500x1500 mm or a 1000x1500 mm.
    How fast can the ox go ( work speed and traveling speed and is it also slower with the 1500x1500 or the same als the 1500x1000?.

    Somebody told me i should get a gecko 540 and mach 3 because ist a lot better then a arduino because the arduino use usb and the gecko a printer port he said the arduine could lose steps sometimes ?
    how accurate is the ox is it 0.01 mm or 0.5 mm ?
    and how accurate can i get the machine?
    can i do something that would make it even better or more accurate ?
     
  2. Tim G-C

    Tim G-C Well-Known
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    Accuracy will be very dependant on your chosen Linear slides and type of motion drive. Not forgetting the care taken building the machine. Don't confuse Accuracy with Repeatability which is very important. If you want your spindle to cut a path then return to the exact place it started from to within 0.01mm again and again, you are looking at ensuring there is minimal or zero backlash and highly accurate power transmission. Expect to build a very rigid high Mass expensive build!!

    Motion can be Ball screw (Very very expensive), Lead screw (Not Cheap) Timing belt, Rack and Pinion, Acme screw and 'All Thread' bar. Each has it's pro's and con's.

    Linear Bearings or slides can also be graded on a 'sliding scale' Bearings from THK, Hewin etc can again be Very very expensive. Cheap Linear shafting and bearings can be obtained from the Bay or direct from China but you get what you pay for!!
     
  3. Metalguru

    Metalguru Master
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    The Ox max travel speed is probably about 2000-2500 mm/min. You might be able to increase that by using the high torque motors. This would be travel speed, not cutting speed.

    I think the standard Ox with 1/8 micro stepping is about 25-30 steps/mm, or about 0.04mm/step, or .0016" per step. This is resolution, not accuracy or repeatability. The OX is a belt driven machine, with a lead screw driven machine you could get an order of magnitude better resolution.

    GRBL/arduino is a very stable platform. I would not expect it to lose steps normally. It's a matter of preference and budget whether you use GRBL or Mach3. Mach 3 is around $200 US just for the software, and you will have to spend more on the hardware to interface it. Mach 3 has quite a few more features over GRBL.

    Gecko drives are in the $500-$1000 range. It depends more on your budget. BTW, nobody uses parallel ports anymore. You can't buy a computer with parallel ports, you either use an old computer or buy a parallel port add on card. USB to parallel port converters will not work. PP are a legacy thing with Mach3, but there are many driver boards that use Ethernet or USB with Mach3.

    IMHO, building a 1500x1500 Ox is a Really Bad Idea. Personally I would not recommend going more than 750x1000mm, or possibly 750x1200mm. It is not that stiff of a machine in the smaller sizes, and having a 1500mm X axis would wobble around like a skip rope... Accuracy becomes moot when your gantry whips around like a snake... Even a C-Beam based design would not be stiff enough at 1500x1500mm to make it worth the effort. If you want something that big, buy a $6000USD kit from CNCRouterParts.com.

    Why do you need such a big machine? Most people tend to way overthink the size of machine they WANT over the size they actually NEED.
     
  4. peter28

    peter28 Well-Known
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    Well i am going to use this machine for cabinets and cabinetdoors.
    i would like to go to 1500 because then i can take the left and right side of a cabinet and lay them on the machine together so that the line drilling is the same.
    And i can also put a half sheet of MDf on the machine .
    but i can also go for the 1000x1500 and then just drill 1 side then the other one.

    if i was to go with a 1500x1500 what can u recommend me to make the machine stronger and mor accurate? or just go with a 1000x1500 machine?
     
  5. Metalguru

    Metalguru Master
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    peter28, See my latest build in Big Ox Heavy Duty.

    You are still thinking like a woodworker, instead of a CNC'er. Because of the accuracy of the machine, you don't need to use techniques like lining several parts up and doing them at the same time. The machine is way more accurate than you will ever be doing things by hand. As long as you have a repeatable jig set up to hold your work, you are golden.

    You might save a small amount of fixturing time by having two pieces in the machine at once, but you will gain no accuracy advantage.

    An 850x1200mm would be just the right size for kitchen cabinet sides. This will mill a 24x36 cabinet side for dadoes, shelf pin holes etc, and do carvings on doors.

    MG
     
    #5 Metalguru, Oct 19, 2016
    Last edited: Oct 19, 2016
  6. Metalguru

    Metalguru Master
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  7. Giarc

    Giarc Master
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    My build (Lead Screw Driven Ox Derivative (850x1500)) is 850 X 1500 and I get a cutting area of about 670 x 1275, which is basically 26.3 inches by 50 inches. I did this for building cabinets as well. The X axis is two 20mm x 80mm beams bolted together and is nice and stiff. As MetalGuru said, if you place your materials in the same spot every time, you will end up with the holes drilled in the same spots every time. I have done this procedure by plotting out my holes in a Sketchucam drawing. Whenever I need that pattern drilled, I just load that g-code file into GRBL Panel and hit the play button.
     

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