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  1. #1
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    Default CNC vs manual milling machines

    I've been keeping my eyes peeled for a second hand manual vertical milling machine. Then I got thinking about a CNC milling machine... for equivalent money you would have to downsize capacity vs the manual mill but they have more versatility. It seems for basic one-off milling they don't have an advantage but they would be great for multi-step projects (eg milling surfaces then drilling a bunch of holes then tapping), or for curved cuts, or complex shapes like propellers. I love the idea of having a manual mill but then you see videos of CNC mills and what they can do with a 4th/5th axis is amazing! Check this out as an example:
    https://www.youtube.com/watch?v=BYmwikH3CJY
    They don't get much of a mention on this forum which I guess is due to price but there seems to be quite a few manufacturers targeting the home user/light industrial (eg Skyfire and Automatecnc) and these will filter down as second hand as people upgrade.
    My question is would there be any disadvantage of getting a CNC mill if you have no manual mill? The thing that worries me personally is a computer software glitch, but I wonder if there is any job that requires a manual mill in particular?

  2. #2
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    A tool maker I know once told me that anything that can be done on a CNC machine can be done on a manual machine, it just takes longer (in some cases much, much longer). I think I can agree with that as I've done some things on a manual mill that 10 or 15 years ago I would not have thought could be done or that I would have the skills and equipment to do.

    I have basically manual equipment in my shed because I work with computers most of the day and like to get away from that if I can. Others think CNC is the way to go because it can do repetitive bits pretty darn fast and as you say some of the fancier things with multiple axis with greater ease. Off hand I can't think of any great disadvantage to going CNC if that is what you want to do; it's not the be all and end all, and if you were only doing one off items I suspect that you may get frustrated by it as as well as doing the set ups as you would for a manual machine, you then have to program rather than just wind a handle or two.

    You also need to remember that those wiz-bang machines you see on Youtube, machining complex fan blade profiles are far different from the sort of machine available to a hobbyist. Industrial machines have a variety of tools to choose from, powerful controllers to drive them and are designed for rigidity & material removal. Even something like a Tormach machine has to have some compromises to be built for the price it is, so the controllers may not be able to move in as many axis at the same time, the machine certainly won't have the horsepower, accuracy may be less and you will still have to keep track of tools.

    If you haven't done any manual machining, you may find things difficult as you still need to learn/ discover the mechanics of machining. CNC does not take that away from you. If anything, it may cause bigger messes as you are one step removed from the process. On a manual machine you are aware of how close you are to a clamp say and will stop before you hit it. On CNC, if you have not allowed for that you are likely to break cutters and damage things before you realise it. There is a reason that machinists are started on manual machines before moving on to CNC...

    Michael

  3. #3
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    Default

    Maybe I'm looking in the wrong place but I don't see too many smaller / hobby CNC machines for sale in Aus. It seems to jump from the Chinese CNC 6040 & variants into commercial machines.

    I have a small Taig CNC Mill that I imported from the states years ago, pretty much came as a kit that you needed to complete, even the wiring had to be fixed up.
    https://www.deepgroove1.com/cnc-mill
    It was my only mill for a long time and you quickly learnt it's limits in both work envelope and power. It lives inside the house in a clear poly-carbonate box so I can run it while working on the computer ect.

    Since then have expanded the workshop and added a Bridgeport clone and have another bigger mill waiting to be commissioned. I would say that 99% of my milling is done on the Bridgeport clone at the moment and only rarely do I fire up the Taig.

    I think the question you need to ask is not so much would there be any disadvantage of getting a CNC mill if you have no manual mill. Instead your question would really be is there a disadvantage in getting a smaller CNC mill over a bigger manual mill. The answer to that one is work envelope and material removal rate.

    A Bridgeport clone can normally be picked up for a couple of grand and are not too hard to come by. A piece that is straight forward machining I can have finished on the bridgeport clone before I have even programmed it for the Taig and that taig will take 50 times longer to machine it. Yes I can be doing something else while it's machining but generally you want to watch the first part being run incase anything goes wrong, if your doing one off parts it means you end up sitting there watching it anyway and don't do anything else.

    Would be nice if you could find a machine like this one tho
    https://www.youtube.com/watch?v=ISzkthutKnA

  4. #4
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    Default

    Quote Originally Posted by Michael G View Post
    If you haven't done any manual machining, you may find things difficult as you still need to learn/ discover the mechanics of machining. CNC does not take that away from you. If anything, it may cause bigger messes as you are one step removed from the process. On a manual machine you are aware of how close you are to a clamp say and will stop before you hit it. On CNC, if you have not allowed for that you are likely to break cutters and damage things before you realise it. There is a reason that machinists are started on manual machines before moving on to CNC...
    This

    And there's always that bit doubt in the back of your mind when you hit go on a new program that you might have spent days writing; you're pretty confident it'll come out the way you expect, but did you forget to change the toolpath correction on one line?

    I don't think CNC is a replacement for manual, I certainly wouldn't have a CNC without at least a full manual override function, if not a separate manual machine.

  5. #5
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    Default

    I would add one more thing. Not having a cnc machine doesn't preclude you from writing some gcode and reading some tutorials. It would at least let you know if it's what you like.

    Have yoù used cad/cam software before? These are all cheap lessons you can go through before you buy a big heavy lesson your wife doesn't like in the garage.

  6. #6
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    Default

    If your requirements are mainly for one-off and basically rectilinear parts then I can't see an overwhelming requirement for a CNC mill.

    As part complexity increases then CNC takes over. Having to transfer a partly machined workpiece to a rotary table gets old fast. Circular milling studs standing in a recess is damn near impossible. Yeah I can think of ways to do it but still.

    Then there's the intended material. Small & light machines for plastic, aluminium and light cuts on soft steel, fine. Get into stainless or hardened 4140 or similar, you really do need the HP and rigidity because playing with light cuts invites work-hardening and it all goes pear-shaped.

    Personally I hate making more than one of anything by hand. Sooner or later I'm going to get a CNC mill *BUT* there's no way at this stage it'd be my ONLY mill.

    Then there's the cost and features. I'd want one with an auto tool changer for example.

    PDW

  7. #7
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    Default

    I'd really like a CNC mill as I come from a 3d printing background.

    There are 2 classes of machine in this ball game if we're talking about mills - Tormach/Skyfire/Syil/Novakon/other and 'real' cnc machines. That is, hobby class vs industrial.
    For hobby, beware skyfire and other Chinese mills, just join the facebook group to see all the issues. Even for Tormach, there are bad stories, check out this one - https://www.youtube.com/watch?v=FtnaqJuJ9kw
    This guy went from Tormach to Haas and explains the hobby vs cnc classes well - https://www.youtube.com/watch?v=PxytA3G4JmE
    There's also the option of retrofitting your own mill, such as an Optimum BF20 or a RF-45 with servos, ballscrews and electronics. See cnczone for many examples of benchtop mill conversions. I slightly regret going down this path now as it puts you a long way away from making chips, it's quite a lengthy process. If I had to restart I might just go for a hobby machine, possibly a Syil myself, and accept its limitations but get to the making chips part sooner.

    For cnc routers like 6040s, 6090s etc. I believe there are your Chinese ones and others. I saw some 'workbees' on aliexpress which are apparently a good option. I haven't really looked into this but they're similar to mills but the routers tend to come with higher speed spindles, a larger work envelope and less rigidity. In hindsight a good option that I could have taken would be to get a bridgeport clone in good nick as a manual mill, then a semi decent router like a workbee (maybe?). That way you can rough out parts on the workbee, sometimes to a surprising accuracy / finish if it's aluminium, and if you need something very precise, e.g. a hole bored, set it up on the bridgeport and do it there (after roughing out a complex outer shape on the router).

    Workbee video - https://www.youtube.com/watch?v=igSYJCYiR9E
    Good video on considerations if you're thinking of going down the used industrial machine route - https://www.youtube.com/watch?v=F7kwRiTYV-g

  8. #8
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    Default

    Thanks everyone for your replies.

    Quote Originally Posted by Michael G View Post
    You also need to remember that those wiz-bang machines you see on Youtube, machining complex fan blade profiles are far different from the sort of machine available to a hobbyist. Industrial machines have a variety of tools to choose from, powerful controllers to drive them and are designed for rigidity & material removal. Even something like a Tormach machine has to have some compromises to be built for the price it is, so the controllers may not be able to move in as many axis at the same time, the machine certainly won't have the horsepower, accuracy may be less and you will still have to keep track of tools.

    Michael
    It looks like the ability to do complex machining is filtering down into the hobby machines. Looking at the Skyfire website, you can order it with a 5HP 3 phase motor, auto tool changer, and 4th and 5th axis kits. Don't ask me the price because I can't seem to get a reply from them.

    Quote Originally Posted by MasterSpoon View Post
    Maybe I'm looking in the wrong place but I don't see too many smaller / hobby CNC machines for sale in Aus. It seems to jump from the Chinese CNC 6040 & variants into commercial machines.

    I think the question you need to ask is not so much would there be any disadvantage of getting a CNC mill if you have no manual mill. Instead your question would really be is there a disadvantage in getting a smaller CNC mill over a bigger manual mill. The answer to that one is work envelope and material removal rate.
    It seems that you have to order the machines yourself from overseas.

    The size difference does worry me as there is always the unknown possible future project that might be bigger.

    Quote Originally Posted by elanjacobs View Post
    I certainly wouldn't have a CNC without at least a full manual override function, if not a separate manual machine.
    I agree that you would need simple manual input for the basic operations!

  9. #9
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    Default

    Quote Originally Posted by caskwarrior View Post
    I would add one more thing. Not having a cnc machine doesn't preclude you from writing some gcode and reading some tutorials. It would at least let you know if it's what you like.

    Have yoù used cad/cam software before? These are all cheap lessons you can go through before you buy a big heavy lesson your wife doesn't like in the garage.
    Good advice, I've only used CAD a little bit.

    Quote Originally Posted by PDW View Post
    Get into stainless or hardened 4140 or similar, you really do need the HP and rigidity because playing with light cuts invites work-hardening and it all goes pear-shaped.

    I'd want one with an auto tool changer for example.

    PDW
    I'd worry about rigidity too as the machines are a fair bit smaller and lighter than a similarly priced manual mill.

    I agree, if you are going CNC then an auto tool changer would seem essential to reap the benefit.

    Quote Originally Posted by j3dprints View Post
    I'd really like a CNC mill as I come from a 3d printing background.

    There are 2 classes of machine in this ball game if we're talking about mills - Tormach/Skyfire/Syil/Novakon/other and 'real' cnc machines. That is, hobby class vs industrial.
    For hobby, beware skyfire and other Chinese mills, just join the facebook group to see all the issues. Even for Tormach, there are bad stories, check out this one - https://www.youtube.com/watch?v=FtnaqJuJ9kw
    This guy went from Tormach to Haas and explains the hobby vs cnc classes well - https://www.youtube.com/watch?v=PxytA3G4JmE
    There's also the option of retrofitting your own mill, such as an Optimum BF20 or a RF-45 with servos, ballscrews and electronics. See cnczone for many examples of benchtop mill conversions. I slightly regret going down this path now as it puts you a long way away from making chips, it's quite a lengthy process. If I had to restart I might just go for a hobby machine, possibly a Syil myself, and accept its limitations but get to the making chips part sooner.

    For cnc routers like 6040s, 6090s etc. I believe there are your Chinese ones and others. I saw some 'workbees' on aliexpress which are apparently a good option. I haven't really looked into this but they're similar to mills but the routers tend to come with higher speed spindles, a larger work envelope and less rigidity. In hindsight a good option that I could have taken would be to get a bridgeport clone in good nick as a manual mill, then a semi decent router like a workbee (maybe?). That way you can rough out parts on the workbee, sometimes to a surprising accuracy / finish if it's aluminium, and if you need something very precise, e.g. a hole bored, set it up on the bridgeport and do it there (after roughing out a complex outer shape on the router).

    Workbee video - https://www.youtube.com/watch?v=igSYJCYiR9E
    Good video on considerations if you're thinking of going down the used industrial machine route - https://www.youtube.com/watch?v=F7kwRiTYV-g
    Great info... thanks for the heads up re the Chinese CNC mills.

  10. #10
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    I forgot to mention that for me personally I think I'd have more fun with a manual machine for simple operations. However, I can imagine there would be enormous satisfaction if you'd done all the programming for a complex machining set up then press start on a CNC machine! I also wonder if you had a manual mill that one day a friend with a CNC mill will produce something that quite frankly you would have to cast or spend forever trying to produce.

    I suspect the CNC mills will eventually take over, just as the humble typewriter gave way to the computer.

  11. #11
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    Quote Originally Posted by Pumpkinate View Post
    ... I can imagine there would be enormous satisfaction if you'd done all the programming for a complex machining set up then press start on a CNC machine!
    The satisfaction is fleeting as you need to get through the program without it crashing. Of course, once you have done that, the part is made and it's on to the next bit.

    Quote Originally Posted by Pumpkinate View Post
    ... I also wonder if you had a manual mill that one day a friend with a CNC mill will produce something that quite frankly you would have to cast or spend forever trying to produce.
    People in the know recognise the effort that goes into making complex bits on manual machines, particularly if it's something more than just orthogonal planes. If it is done on CNC, it's dismissed as the computer has done most of the work. True in a way - Once you have programmed the machine, it is just following instructions. No one knows if you have spent 5 minutes or 5 days programming and you have probably verified your work on the screen. Manually, the risk is there in real time...

    Quote Originally Posted by Pumpkinate View Post
    I suspect the CNC mills will eventually take over, just as the humble typewriter gave way to the computer.
    Possibly not - there are always one off jobs that don't justify programming time.

    Michael

  12. #12
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    What you have to remember is that the machine will do exactly what you tell it...which isn't what you thought you told it.

    Robert

  13. #13
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    While I'd love to have a CNC machine at times, I also wonder whether it'd be far more hassle than it's worth for a lot of what I do. Often I'm throwing an existing part into the lathe or mill to modify or repair it - generally car parts, but could be any pre-existing part. For instance, I just pulled the drive wheel off my 7x12 bandsaw, and to fix the flogged out bore, I rebored it to a taper, and made up a taper-lock bush to match, then recut the rounded off running surface true to the new centre bore, stopping once the low spots were gone. Doing that on a CNC seems like a headache of programming to me, and I suspect it would be faster and easier the way I did it (Unless of course the CNC machine also has manual controls, but I don't know enough about them to know if that's a common thing.)

    For scratch built parts, CNC would usually win, but then again some of what I do is quick and dirty, and only starts with a concept in my head, that resolves as I cut. Although I can run Fusion 360 pretty quick these days, some of my stuff I still reckon would be quicker without.

    As an added thought, given the number of times I've had to change an insert or sharpen a tool partway through a piece of scrapbinium for one reason or another, I could forsee a number of parts coming out at the end of the cycle that are not what I wanted due to tool wear/failure. I think I'd waste a lot of steel that way, where on a manual machine you can replace inserts/sharpen tools and go by micrometer dimensions. And steel ain't cheap...

    Personally, I think it's highly dependent on what your projects usually entail...

  14. #14
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    [QUOTE=Jekyll and Hyde;1939552 For scratch built parts, CNC would usually win, but then again some of what I do is quick and dirty, and only starts with a concept in my head, that resolves as I cut. ..[/QUOTE]

    That's pretty much how I operate, so I don't think CNC would be much good for my make it up as you go methods.
    Also I think for a hobby machinist, with most jobs being a one off, a manual mill would be quicker and less hassle.
    If you were doing production runs, it might be a different story.
    Regards
    Bradford

  15. #15
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    Modern CNC isn't hard to program. With conversational control you pick the cycle you want eg. rectangular pocket. a screen comes up with a picture and a heap of fields to enter numbers into Eg. size, depth. then you hit go. Its not like the old days when you have to enter every movement in code.
    I do one off and repairs at work all day and only use CNC mills and never want to go back to manual mills.. For a home shop manual lathes are better, CNC is a pain for one off.
    The down side of CNC is cost. 2nd hand machines are non existant here and new starts at about $20000. Hard to justify for a home shop when a 2nd hand turret mill can be had for $2-3000.

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