know how to use a CNC machine?

Discussion in 'Gunsmithing Forum' started by dynastyofnext, Jun 17, 2009.

  1. dynastyofnext

    dynastyofnext New Member

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    I'm up to my last MOD for the gunsmith course I am taking which is handguns; the only reason I took the course. In the other MOD's they mentioned using a CNC machine and its functions, but they never went into detail on how it works. Does anyone have experience with a CNC? Operating it? What other uses are there for a CNC machine?
     
  2. c3shooter

    c3shooter Administrator Staff Member

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    Disclaimer- I DO NOT use CNC machines myself, but have been around enuff manufacturing facilities that do.

    Unlike a standard machinist's lathe or milling machine, where you set operations thru a mechanical dial, a CNC unit is controlled by a computer, which directs tool speed, movement in 3 dimensions, etc. Very handy for DUPLICATING multiple pieces parts.

    Instead of the machinist turning a set of dials that move the cutter, a computer software program directs it. Allows program to be copied and sent to user to install. Also allows for high degree of accuracy in complex machinings. But to set up program first time, requires knowledge of the machine code (seem to recall G code being common one used).

    Does every shop need one? IMHO- no. If you are going into the manufacturing business, might be worthwhile.
     

  3. dynastyofnext

    dynastyofnext New Member

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    Thanks for the help. Now all I gotta do is find out what this G code is and how to use it.
     
  4. hunter Joe

    hunter Joe New Member

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    I operated CNC machining centers for nearly 25 years and there is a lot more to it than learning G-Code programming. Speeds and feeds, M-Code functions, using gauges, tool maintenance, set-up, and the list goes on and on. Stay in school.
     
  5. Gojubrian

    Gojubrian New Member

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    I'm a machinist by trade and can run most types of cnc mills, lathes(vertical and horizontal),etc..

    You can write programs to do whatever the machine is capable of using auto-cad or whatever the machine is set up to accept.
    Learning the ins and outs of cnc machining is not small feat and would require someone who already knows what they are doing. Otherwise, you'll probably crash it and jack it all up. I went to school for this ,lol.

    I work in the aerospace industry for Pratt & Whitney machining jet engine parts for the military and commercial planes holding as tight of tolearnces as + or -1 thousandth or +/- .001 for large diameters. When I worked with high speed cnc machines we would hold as much as 4 microns or .0004. :)

    I also use to run the frames for wilson combat 1911's. Very tight tolerances there. :)

    Here's the G and M codes, but they can vary from machine to machine.

    Does it ha ve a FANUC control? What type of CNC is it? I might can help from here.

    MachineMate Inc - Full List of CNC Codes
     
  6. Gojubrian

    Gojubrian New Member

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    Pretty much,lol. I've been at it for 13yrs, man am I a lucky guy. :D
     
  7. dynastyofnext

    dynastyofnext New Member

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    I dont have a specific machine just wanted to learn how to use one. If it was as simple as autocad input and hit drill, it would of been cake. It looks more like its C+ style coding, how do you get a design out of these machines? I'm familiar with Autocad and circuit building is it anything close to the same?
     
  8. skullcrusher

    skullcrusher New Member

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    CNC machinist here as well. Getting a post from a cad system can be done a few ways. RS232 cable, disk or flash drive depending on the machine and control. Autocad and others need to be programmed to post the codes that that specific control accepts. It can work great, but the cad produces large number of codes and lines even for a simple turn operation.

    I program direct G & M codes for some different but popular controls. They are not the same codes for each control. Even within the same make of control, the codes can vary.

    Goju, I programmed some Fanuc Super Precision controls that I programmed to .00001 and held tols of +/- .0001 on a regular basis. That is some cool shat right there! :D
     
  9. dynastyofnext

    dynastyofnext New Member

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    .....kind of sounds like you guys hang out at Area 51; whats a Fanuc SPC?
     
  10. skullcrusher

    skullcrusher New Member

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    Maybe a super precision control? Usually the machines are specified SP and the control itself is programmable to 5 digits to the right of the decimal point. The machines are built to tighter tols and the servos handle the minute moves.

    For instance: Hardinge T42 SP w/ a Fanuc 18T control is a super precision lathe and the control is programmable to .00001 inches.
     
  11. robbo60

    robbo60 New Member

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    I've been a tool room machinist for Caterpillar 11 years. I use newer CNC Mazak machines with conversational programming but have used many different codes in the past as well as all the manual machines and setups. If I can help you with anything let me know. Rob.
     
  12. dynastyofnext

    dynastyofnext New Member

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    thanks for the offer, can you tell me how the code is setup? Like say you show up to work and you have a new project, how would you start?
     
  13. indy_kid

    indy_kid New Member

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    My 2 cents...


    Easy as flying the Space Shuttle!


    My way of saying that you'd need to know basic machining, have a couple hundred hours with all the various machines (lathe, mill, etc.), then move up to CNC. Even then, you have your basic CNC, your advanced CNC, and your OMFG CNC. Learning never really ends, nor should it.

    Other uses? What other uses are there for a 1911? Sure, you can use it as a hammer, but that isn't what it was designed to do. Sorry to sound harsh, but it's a very specific tool for a very specific task. Yeah, I'm sure someone had a CNC lathe with dozens of bells and whistles (just like some folks will put every accessory on the AR), but are they really necessary for the job at hand? I think the job determines which tool to use, and, more importantly, which tool NOT to use. An A-bomb will kill folks just fine, but it's not a CQB weapon (well, maybe once).

    CNC is good for rapid prototyping, as you can program it to spit out a piece made of plastic to give you an idea of the finished product. When you get the design refined, then you use metal and dial in the high tolerances.

    BTW, I'm not a machinist, though I'd love to learn to use a metal lathe for some basic gunsmithing. Just don't find a local school that offers the courses.

    The last HS I taught at had 12 industrial metal lathes, but no teacher. They could no longer put them to use during or after school (adult classes) - the liability insurance was too high.
     
  14. skullcrusher

    skullcrusher New Member

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    (Simply)

    Projects are started the same way. A print is given to the programmer/machinist showing the part, tolerances and material. The machinist selects which tools will be needed and gathers them for set-up. Programmer goes to the control and writes the G&M codes. The tools are set-up in the machine and the material is placed into the spindle or chuck or vise, whatever the workholding is on the machine. The program is usually checked on the control (run thru without machine actually doing anything) to check for mistakes or typos. After the tool lenghts are set in the offset, the green button gets pushed and machine makes part. Machinist checks part to tolerances and makes the changes in the offset to make sure the sizing will be right and the part is in tolerance.

    What else you wanna know?
     
  15. caniswalensis

    caniswalensis New Member

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    Hi Dynastyofnext,

    I have had two manufacturing jobs that required me to be able to operate & program CNC machines.

    The first, I worked in the engineering department of a very high-end furniture company. We had two 3-axis Komo CNC routers. They ran production parts for almost every piece that we made. Lots of fun to program & very challenging at times due to the special nature of some of our parts.

    Second, a 2- axis CNC water jet machine that cut parts out of rubber & foam by the hundreds. The complete opposite of the first job. We used nesting software to do a lot of the programing based on AutoCAD drawings. Very simple process from start to finish.

    Both of these places really benefited in a big way from having the CNC technology available. Production parts were made faster & with much closer tolerances than if they had been made with traditional methods. The possible manufacturing applications are limited only by the imagination.

    In my experience, each machine & software setup is different and you need to be trained specifically for the machine & software that you would be using, as well as having a general understanding of CNC programing & technology.

    I would say that it is beyond the scope of a forum like this to really explain to you how use a CNC machine. However, if I had you at the second job, I could make you into a competent operator in a day; and a programmer in a week. But that is with the simplest of Machine/software setups I can imagine. At the first job, We would spend months getting people trained to operate/program our machines.

    Hope this helps, Canis
     
    Last edited: Jun 17, 2009
  16. dynastyofnext

    dynastyofnext New Member

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  17. skullcrusher

    skullcrusher New Member

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    Comminity Colleges and Vocational Schools are your best bet. My training came through a job and control specific schooling that machine mfrs do for customers (my employers). I have programming certs from Hardinge, Emco-maier, Haas and Okuma. Basic lathe and mill is pretty easy. I also have C-axis programming. (That is live tooling on a lathe for drilling, milling, tapping, etc.)
     
  18. dynastyofnext

    dynastyofnext New Member

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    thanks, So what would a simple program look like? How is it written?
     
  19. skullcrusher

    skullcrusher New Member

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    First, there are few simple programs. It is all relatvie to the part.

    Basic turn:

    N0001 G97 S1000 M4 T0101 (spindle on at 1000 rpm, tool #1)
    G00 G99 X1. Z.1 M08 (rapid move, inches per minute feed, coolant on)
    G01 Z-1. F.01 (linear interprolation, 1" length of cut at .01" per minute)
    X1.46 (move up on X)
    G03 X1.5 Z-1.02 R.02 F.005 (circular intrerprolation and .02 radius cut)
    G01 Z-1.5 (linear interprolation to 1.5" length)
    G00 X1.55 Z-1.48 M09 (rapid move off part and coolant off)
    G28 U0. W0. M05 (go home and stop spindle)
    M30 (end program)

    That is a part that will measure 1" dia for 1", 1.5" dia with radius at 1.5" from face of part.

    That basic program does not use tool nose radius compensaton (G41/G42) to help control part size. In theory, the length and radius would be off depending on the radius of the cutting insert.

    That is also a gerneral program for Fanuc control. Okuma uses G94 for ipm and no use for G28. Also, not all Fanucs use G28.....

    This can get lenghty and complicated. I did not even try to cover canned programs.

    Also, whole comments within () will not be read by the control, they would not be written into the actual program. I used them to tell you what was happening.

    Also, I did not use constant surface feet per minute that makes the spindle change speed at each dia.
     
    Last edited: Jun 17, 2009
  20. Gojubrian

    Gojubrian New Member

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    Skull,

    .oooo1???? How? If the air temp changes a couple of degrees the tolerances are out,lol. Don't blow on it!! :D

    I like how where I work we machine the parts in one temperature and they CMM them in another room with a different temp,lol. Makes it interesting figuring out how much it will grow or shrink sometimes.