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Thread: Lerarning cnc

  1. #1
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    Default Lerarning cnc

    I am computer challenged and also cant do any cam drawings. Is it possible to learn to program and drive a cnc lathe without being able to cad draw? I am thinking of learning to use cnc but would not like to take a chance and spend lots of money to find I have to rely on an outside programmer.Is there a simple language that all cnc lathes understand .The stuff I want to make is not complex but more repetitive. Ideally I would like to make or buy a simple cheap cnc lathe which would not cost the earth and if it does not work out for me I am not left with a big financial burden. I thought I saw somewhere a college or varsity where the students built a cnc lathe for a project and the plans were freely available.
    Second question to show how computer dumb I am. Why do my you tube downloads always take so long and freeze so bad that I loose interest.
    3rd question. My daughter asked if her computer would get heavier if she downloaded info for school projects and I couldn't answer her

  2. #2
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    Apr 2010
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    Learning CNC. CNC ....Computer Numeric Control. CNC is not a language used by machines as a language of communication.

    What you probably want to learn is "G" code, which is a pretty much universal machine language. An alternative, if controller capable, is often referred to as conversational programming.

    Basically, conversational consists of the controller asking questions, the operator answers the questions. the controller software then writes the "G" code based on the info/answers entered. The controller then tells the machine what to do based on the code/commands entered.
    Last edited by Amigo; 11-12-2011 at 04:19 AM.

  3. #3
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    Plunger you have no idea what can of worms you just opened regarding whether or not the computer gets heavier or not after downloading.

    THe smart guys on here are going to write 10 pages of answers about electrons and such. There was are recent thread that was quite entertaining along those lines.
    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

  4. #4
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    BlackForest, Your "can of worms" comment is spot on. The uninitiated have no idea.

  5. #5
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    May 2011
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    CNC ???? What's that ???

    Tell your daughter that her computer is a box that does not need to be moved so that any added weight is unimportant, but the box has only so much space in it. The more things she puts into it the less room she will have to put new things into it. Also, with each new item she puts into the box the box will take a slightly longer time to resort itself to find and give her back what she wants to take out of it.

  6. #6
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    Mousiour Le Plunger.

    It's possible to dip your toes in the water by just hanging two stepper motors onto the cross slide and leadscrew of a normal lathe.

    Now before the purists all get revved up about accuracy and ballscrews etc we are talking learning here, it might be that it doesn't work out and instead of a bought in dedicated CNC lathe becoming a boat anchor you can play for not much money and still keep the manual lathe.

    Then a simple controller program like Mach3 can be used on an old computer and this has what they call wizards but is conversational programming where you fill in boxes like lengths and diameters, speed and depth of cut and the 'wizard' writes the program for you.

    Contrary to popular opinion it's possible to work a CNC without knowing G Code, that comes to you later by osmosis.
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.




  7. #7
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    Oct 2003
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    mesa, az
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    The school I went to had a cnc program, we learned g-code and they had a small EMCO cnc5 lathe for us to program and make parts with. We did all of the programming by hand and layed out the parts on graph paper. No CAD needed, you do need a little bit of math skills, nothing hard, but if you havent done it in awhile may take some refreshing.
    FuQ

  8. #8
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    Apr 2007
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    Gauteng South Africa
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    Hi Eugene,

    CNC your Chinese lathe that you don't use.
    All you need are two stepper motors, power supply, breakout
    board, driver boards, computer with Mach program and a couple
    of pullies and belts. Go to www.hobbycnc.co.za and you will
    find what you need with prices.

    As Sir John says you don't need ball screws to get learning,
    then later you can build a "proper machine" like mine.

    Werner

  9. #9
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    Hi Plunger,

    You most certainly do not need to be able to draw anything to make parts on a CNC machine. You just need to be able to describe it in x y z coordinates (or just x and z for a lathe). The G and M codes, while they look like gobbledegook, are there to control specific machine motions and make a lot of sense when you break them into groups.

    The group G00, G01, G02, and G03 all move the tool on the lathe and the table on the mill in the same way. G00 is Rapid Traverse, moving the machine as fast as it can go (to get to the part quickly, no machining is done with this code). G01 is Linear Interpolation, used for cutting straight lines, either cylinders or tapers. G02 and G03 are Circular Interpolation Clockwise and Counter-Clockwise respectively. They are used for cutting radii. All of these (except for rapid traverse) would also be accompanied by F codes, which specify the feed rate. For instance, G01 X.5 Z-1.25 F.003 would move from the tool's current location to the X an Z coordinates stated in a straight line at .003" per revolution (lathe program).

    The next group, M03, M04, and M05 control the spindle rotation (forward, reverse, and stop respectively). These will be accompanied by an S code for speed, so M03 S3000 would turn the spindle on forward going 3000 RPM. There are also codes for turning the Coolant on and off (M08 and M09).

    There is also a set of codes to compensate for the radius of the cutter (either the tip of a carbide insert or the diameter of an endmill). G41 and G42 are used for this on the Fanuc control (I'm not sure if these are control specific or not). One is Tool Radius Compensation (TRC) Left and the other is TRC Right. On the lathe, these are only necessary when cutting radii and tapers and you'd use one for outside turning and one for boring. On the mill, they determine which way the cutter is offset for its radius, depending on whether you are milling the outside or inside of the geometry. G40 cancels TRC. Many of the G and M codes are "Modal" meaning they stay active until another code in the same group cancels or supersedes it.

    There are numerous other codes that may or may not be control specific. There are codes to specify Inches or Metric, Feed in IPR or IPM, Constant SFM or Constant RPM, etc. There are also things called canned cycles, which are used for roughing and finishing, threading, drilling holes, thread milling, etc. These are used to shorten the program. When using these, you would specify a number of variables. In the case of a roughing cycle, you would tell the control which lines of code to repeat over and over, how much to take off per pass, how much to leave for a finishing pass on the X and Z axes, and feedrate. Once the roughing cycle is done, the finishing cycle takes over to finish the geometry.

    Lastly, T codes specify tools and their offsets. On the lathe, you would call up a tool by putting something like T0202, meaning you want the second tool position in the turret and it uses offset 02. The control stores the offsets when you set the machine up. You would touch each tool off on the face and diameter and enter that into the system so the control knows where the tool is. This is also where you put the nose radius of the insert for use with G41 and G42. On the mill, the tool is called up just by its number and a height offset is specified on a separate line, but the offset screens look pretty similar. There is also an offset screen to account for the wear of each tool, so you can adjust as your parts start getting close to being out of tolerance.

    BTW, the Z axis is always the spindle of the machine. X on the lathe is the diameter of the part (cross feed). On the mill, X is side to side, Y is front to back.

    Remember, just like manual machining, the only two things you really need to know are:

    1. Where is my tool in relation to the part?
    2. How does the machine move?

    Once you know the answer to those two questions, you can make anything you can imagine.
    Last edited by hornluv; 11-12-2011 at 11:58 AM.
    Stuart de Haro

  10. #10
    Join Date
    Nov 2006
    Location
    durban s africa
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    Default

    It all seems so daunting.Thanks for taking the time to explain it I am going to ask some stupid questions here. I would like to get a feel of cnc but if one had to upgrade to a better lathe at some time does that lathe have its own programme to control the commands I would not like to be bullied into relying on a company for backup every time I get stuck.Similer to some of the computer programmes out there like accounting packages where it costs alot for help. Is mach expensive to buy and would it be able to run a fancier machine if I get into it.Living in s Africa poses problems when it comes to facilities for learning. Can one become self taught in mach via the internet.
    Werner I don't think there are to many people around who could build a lathe like yours but it might be a good idea to make my Chinese lathe into cnc.
    Hornluv that's one hell of an answer to a question. Would take me a day and a half to write all that. However it has made made me understand that its not all magic and much more logical. I appreciate you taking the time Thank you

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