Thread: Why CNC?

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  1. #1
    Hello People,

    I'm a retired software engineer and like many who have spent their working lives pondering the invisible workings of processor internals, I feel the need now to make things with my hands as well as my head. So I have bought a 7 x 14 mini-lathe and of course I already have a decent bench drill, and I'm currently in the happy process of fitting out the rest of my tiny workshop.

    Now it's clear from this site that CNC holds attractions for many hobby machinists, but can somebody explain to me why? Surely CNC makes sense only if you're going to make products in quantity on a production basis? No doubt I'm missing something here, but may I ask "What exactly are all these CNC wood and metal routers going to make in such quantity that it's worth all the trouble and expense of going from manual machining to CNC?"

    Looking forward to being enlightened.

    Ian in Banbury :confused:

  2. #2
    I think there is more than one answer to this question.
    First I think saying cnc is only good for production runs is wrong in concept, it can make single items quicker and easier than by manual means.
    The manual method will entail the production of jigs etc to get the required shape and jigs again are usually in the realm of production whereas the cnc jig is the drawing program.
    Why use a machine at all most things can be made by hand tools and lots of effort, but if you like tools make a cnc mill or router nad then you can make even more tools.
    Most people on the forum are doing it as a hobby or as an idea to make money etc. Its ones imagination that wins in the end and if you have to justify it then dont do it just go down the pub.
    It all depends on whether its the journey you enjoy or just the destination, I for one enjoy it all and am not at all sure it will do what I want in the end but I'm not going to stop because I cant see the end in sight!
    Besides I like tools using and buying, making them, I have the belief that some day I will use them in earnest(well thats what I tell thye misses)

    Last edited by ptjw7uk; 10-12-2009 at 01:07 PM.

  3. #3
    Thank you Peter. It's the same excuse I use to my wife when she complains that when she opens her broom cupboard now, lots of metal bar stock falls out!

    I understand the point you're making though; the journey is part of the fun, and if the destination turns out to be somewhere nice, that's a bonus.

    But thank you too for a point I hadn't considered, namely that it's quicker to make a single part by CNC than by manual methods. That hadn't occurred to me. So perhaps you can answer another question which follows on from that, namely "Which CAD?" AutoCAD is a good commercial product but hopelessly over-priced for hobby use. Whis is the most popular CAD/CAM amongst the users of this forum? Is there such a thing as a concensus?


  4. I've recently finished my MDF machine - I enjoy designing things on a computer...I have done so even before the cnc machine. I also enjoy making things - now I have the cnc machine it allows me to design more complicated things & then make them with an accuracy that I could never have done before with hand/machine the end of the day its another workshop tool - but a very versatile one that does also speed up the building process.

    Mine is purely for hooby use & my own enjoyment - if at some later stage I find that I make something that I want to sell, then I have the capability to make more of them easily.

  5. #5
    Thank you. I'm beginning to get the drift. I have used CAD for designing PCBs for about twenty years and I certainly wouldn't want to go back to the early days of PCBs when I had to draw tracks by hand on to the board using a paintbrush. So I can understand the improvements which come from using CAD for machined parts.

    I probably approached this subject from the wrong end. The right place to start thinking about it would seem to be the CAD, and THEN the CNC follows naturally from that.

    (Which probably means I should find and migrate over to a CAD/CAM thread.)


  6. #6
    For me, the attraction is four-fold.

    Firstly, I design on a computer, so being able to just tell the computer "Take this, and make it" is fantastic - I don't need to print anything out.

    Secondly, I can get a significant amount of accuracy that I wouldn't have been able to get manually. I'm designing a car body, and it's expected that a manual process would be, at best, 3mm from side to side. The computer's accuracy is significantly higher than this (I'm aiming for 1mm, but I know that it should be able to get much higher).

    Thirdly, it's repeatability - if I need to make 1 'doodah', then manually it would be doable. If I needed to make 10, then it would be a bit laborious - 100, and I'd get really tired of it.

    Finally, it's automatic - I don't need to watch it do its thing over many hours, so I can get on with other things while it's doing its thing.

  7. #7
    The software side of things is a big problem in that you will unless you start to sell items never make up the large cost of the software.
    So what are the options, cambam do a free version which I have used and is reasonable for whta I want to do at the moment. Then there is Flashcut CNC3 which loads and can create gcode for free see post 5 by JohnS
    This will get you most of the way down the learning curve.
    I have Autocad Lt but it will not run on my Vista machine so I have to transfer dxf files to the vista machine so much for progress. Looking at the new Windows7 professional which will run a version of XP but needs a clean install so I'll just wait as this is a hobby and not a bottom less money pit.
    Just had a dya of more learning the ins and outs of cnc in that the software used with my controller Easycnc2 has an engraving function taht I have been playing with. For small print it appears to be OK but as I wanted bigger the curves to letters was a bit lacking so, I tried the Cambam text and it was a lot rounder flowing output, So produced the gcode and input it into easycnc2 and run it in emulate wtf it was producing great swirles all over the place?
    Had a look on the web for an emulator, found one download and run it text was great. Loaded the code into the mill and produced great swirles as per the emulator. Quick email to CDE produced the fact that there was an option for G02 and G03 code in that for arcs there is an option to do them in absolute or incremental fashion. Put a tick in the box and the text is now OK.

    You just have to take it one step at a time!


  8. #8
    Thank you Tribbles. That's a very comprehensive and persuasive set of arguments! :)

  9. #9
    Tom's Avatar
    Location unknown. Last Activity: 02-01-2014 Has been a member for 4-5 years. Has a total post count of 172.
    can somebody explain to me why?
    For me it's the same, the pleasure and freedom of being able to design something that doesn't necessarily have many straight lines in it. It's a bonus that you can make 2 or 3 in a similar time as it takes to make one (make one, sell one, give one away). My machine has only been running a couple of weeks, and isn't truly finished, but I'm loving CNC so far - if you can imagine it, you can make it!

    So perhaps you can answer another question which follows on from that, namely "Which CAD?" AutoCAD is a good commercial product but hopelessly over-priced for hobby use. Whis is the most popular CAD/CAM amongst the users of this forum? Is there such a thing as a concensus?
    My workflow at the moment is ProgeCAD Smart -> Cambam plus (still in my 40 trial startups) -> EMC2. This is fine for 2D and 2.5D cutting. The programs import and export via DXF.
    ProgeCAD Smart is basically the same as autocad, and free for non-commercial use.

    Later I'm going to get more into 3D forms (I have a very specific project to make a wedding present for some good friends), and have started to learn Blender (a pretty steep curve). Again export via DXF, but I haven't tested Cambam like this yet...

    I don't know about a consensus though! :)

    In summary, if you need to find some critical views on CNC, you probably need to try a different forum!!

  10. #10
    Peter, thank you for the CamBam tip. I hadn't heard of it, and it looks interesting. You're certainly right about the cost of software, and I'm amazed that hobby users can afford stuff like AutoCAD at all (unless of course they hoist the Jolly Roger and sail off into the sunset with a dodgey copy).

    I'll take a look at CamBam tomorrow. I suppose if all else fails I could actually write some CAD/CAM code myself; but I'm not very good at visualising things in 3D, and the thought of debugging 3D trig makes my head spin.

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