4-Axis CNC or 3-Axis CNC and lathe?

Discussion in 'Tools' started by Dousi, Oct 28, 2012.

  1. Oct 28, 2012 #1

    Dousi

    Dousi

    Dousi

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    Hi guys,

    I'm planing to build some model engines and want to build a CNC mill for doing so. My question is now, if its ok to build a 4-axis CNC or if I must have a lathe?

    I plan to do crankshafts and eventually the camshafts with the 4-axis CNC.

    hoping for answers.
    Florian

    Florian

    PS: sorry for my english, as I'm from switzerland...
     
  2. Oct 28, 2012 #2

    kuhncw

    kuhncw

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    Hi Florian,

    First of all, your English is very good.

    This is my opinion, but I feel the three axis CNC and a lathe would be the better combination. I think you will find many jobs will be easier to do on the lathe. You can always add a 4th axis to your mill by putting a stepper on a small rotary table, such as a Sherline table or similar.

    My experience comes from a Taig 3 axis CNC mill and a Sherline 4 inch rotary table with a stepper motor on it. My control was built from the beginning with 4 stepper drivers. I have a manual lathe and also another manual mill in the shop.

    Good luck and please keep us informed as you build your CNC mill.

    Best regards,

    Chuck Kuhn
     
  3. Oct 28, 2012 #3

    bret4

    bret4

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    I agree, the 4 axis mill may not give the finish on the crank to fit the bearings. Not that it can't be done but a lot can be done with the lathe and a cnc mill.
     
  4. Oct 28, 2012 #4

    Tin Falcon

    Tin Falcon

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    Florian :
    1st of all welcome to the forum. Please post an introductions in the welcome area. if you please sir.
    2nd may I ask why a warp jump to cnc is that what you are used to ? college or tech school maybe. We recommend manual machining first.

    While it is completely possible to build an engine with just a mill a lathe is considered king of the shop. and the most essential machine tool.

    you are talking crankshafts and camshafts so sounds like you are planning on multiple cylinder Internal combustion engines. not an easy task but doable.
    IMHO you need a lathe for the task.

    To build a 3 axis cnc or 4 axis is just a matter of an extra stepper motor and a rotary table and maybe a center support. building a fourth axis is easy programming it to make cams and crank shafts could be a challenge but again doable.
    Comparing a 4 axis cnc mill to a lathe is like comparing an apple and an orange.
    Tin
     
  5. Oct 29, 2012 #5

    Dousi

    Dousi

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    Thanks to all for your answers!

    I know that its easy to step ud from 3 to 4-axis cnc, but I don't know if I should spend the money for the lathe or not. I will go CNC because its more fascinating to me, and I'm an Automotive Engineering Student, so I have acces to all the programs needed to draw and programm the machine. I also have the knowledge to build and operate the cnc, and I can operate an manual mill and lathe too, learned it in my apprenticeship.

    I wasn't thinking about a special engine when I wrote this, I just meant the camshafts and crankshafts for all those engines that I'm gonna build.

    I will, as I'm gonna build it from ground up, not based on a commercially available machine.

    is it only the quality of the surface wich bothers you, the 4-axis couldn't handle? I think this should be doable with the mill, when proper machined?

    greetings
     
  6. Oct 29, 2012 #6

    Tin Falcon

    Tin Falcon

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    commercial cams and crankshafts are usually ground. If you make a grinder for cams and cranks machining to 2 to 5 thousands oversize then finish grinding could give the best results. or mill to size then hand polish.
    sounds like you have a good foundation and a good grasp of what you are doing.
    I guess the next question is what size/scale engines are you planning and what size machines are you building.

    I put together a small cnc lathe for IIRC $350 US It uses the same computer and controller as the mill.

    I see nothing wrong with using commercial machines or parts as a foundation for your project will likely save time and possibly money. but this is your journey your choices.
    I put together a getting started in cnc thread in the cnc area you may find it helpful. I am US based so suppliers are US based.
    Tin
     
  7. Oct 30, 2012 #7

    kuhncw

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    Florian, what size mill are you planning to build?

    When you speak of a 4th axis, I think of a stepper driven rotary table or indexing device. Are you perhaps considering something like a motor driven lathe headstock and spindle mounted on the mill table? Something like that might take the place of a lathe.

    Regards,

    Chuck Kuhn
     
  8. Oct 30, 2012 #8

    dieselpilot

    dieselpilot

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    A lathe is a requirement in my mind. So many parts are cylindrical and would be much more difficult to produce on a mill. Many engines have been built on a lathe alone, but I've seen very few with just a mill. I just added a 4th axis to my small CNC mill, and hope to take my projects to the next level, but it can all be done without a CNC 4th axis.
     
  9. Oct 30, 2012 #9

    MuellerNick

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    That depends on your 4th axis. If it is fast enough, you don't need a lathe. Fast means 2000 RPM. But that would mean a hybrid or dual drive for your axis.

    Something like this (minus wife's comments):
    [ame="http://www.youtube.com/watch?v=b2-Kdud7eiA"]this[/ame]


    Nick
     
    xpylonracer and larry1 like this.
  10. Oct 30, 2012 #10

    Dousi

    Dousi

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    thats a good idea, I think it's the way I will go. Handpolishing at beginning, eventually building a grinder later.

    Thanks, I'm planing to build engines about 1/4 scale V8:cool:


    sorry, but what's IIRC?

    I will base my CNC design on the momus design seen here. but I will make it bigger than the momus design, because I want do other works with it too. it wil be about X:1200mm, Y:650mm Z:300mm

    I was thinking of a stepper driven rotary table, but considered a combination both, so that I'm able to work as a Lathe, and a indexed axis, something like muellernick just posted.

    This would be the killer machine in my opinion, if it would be possible to work in lathe mode, but with the (running) milling cutter as a lathe tool. is this doable?

    Florian
     
  11. Oct 30, 2012 #11

    dieselpilot

    dieselpilot

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    Nick, I suppose that's a reasonable way to go. I would still have a manual lathe in my shop. I hope to have my CNC lathe going soon, so I'll see which jobs end up on which machine.

    Greg
     
  12. Oct 30, 2012 #12

    MuellerNick

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    So you want to build plastics models?

    +1
    I have a manual lathe and a CNC-lathe. I use both.
    I also have a manual mill and a CNC-mill. I only use the CNC-mill. Since the CNC-mill works, I *never* switched on the manual mill. I intend to sell it (since a year).


    Nick
     
  13. Oct 30, 2012 #13

    dieselpilot

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    There is one more thing to consider when talking 4th axis, software. I've not found a 4th axis continuous machining CAM for less than 2500USD. You can do a lot with 3 axis CAM and manually coded indexing, but after just a few parts I see the need for continuous toolpaths. It's been several months since I've looked so i don't know if there is anything new on the market.
     
  14. Oct 30, 2012 #14

    kuhncw

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    Hi Florian,

    Thanks for the detail on the size of the machine you are planning. That is not a small machine.

    With regard to the 4th axis, you may have already seen these ideas, but I'll mention them just in case.

    Tormach sells a lathe they call the Duality Lathe which is mounted on the table of their Tormach mill. I'm not suggesting putting a complete lathe on your mill table, but the concept is similar to your idea for using a 4th axis for turning. They mount the lathe tool holder on the quill of the vertical mill. The Duality Lathe manual, Section 2.3.3, page 17 shows how the cutting tool is mounted. http://www.tormach.com/1100_options_lathe_4th_axis.html

    Here is another example of a 4th axis for lathe turning. http://www.theinturn.com/

    Regards,
    Chuck
     
  15. Oct 31, 2012 #15

    Dousi

    Dousi

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    No! You think that because its wood right? It is pretty strong if built like this, and it can be waterproofed against the coolant.
     
  16. Oct 31, 2012 #16

    MuellerNick

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    You will have to report about your experiences later (I avoided the word "success" in that context).


    Nick
     
  17. Oct 31, 2012 #17

    kvom

    kvom

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    Any CNC mill can work as a "vertical" lathe by fixing the stock in the spindle and securing the tool(s) to the table or vise. The limitations of this are the lack of a tailstock and maximum diameter/length of the work.
     
  18. Nov 2, 2012 #18

    dieselpilot

    dieselpilot

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    Anyone using a decent 4th axis CAM software? I've evaluated a few and none of the less expensive ones make suitable toolpaths.

    Greg
     
  19. Nov 2, 2012 #19

    kvom

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    Most hobby machinists I've heard of using a 4th axis use a 2.5D CAM program along with CNCWrapper.
     
  20. Nov 2, 2012 #20

    MuellerNick

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    Depends on what you want to do. Some milling can be described with math. Like a helix on a cylinder. Or gears, or camshafts, ...
    In that case, either write a program in $YourFavoriteLanguage that generates the G-code or do it directly in LinuxCNC.

    [ame="http://www.youtube.com/watch?v=-WacJOVzxmY"]Hirth-coupling[/ame]
    [ame="http://www.youtube.com/watch?v=SJQtx80euGM"]Gear Cutting[/ame]
    [ame="http://www.youtube.com/watch?v=YnABuOOoi5w"]Camshaft milling[/ame]


    Nick
     

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