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How to think - planning my first CNC

Discussion in 'CNC Mills/Routers' started by Zeuligan, May 16, 2017.

  1. Zeuligan

    Zeuligan New
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    I'm a total beginner and found many great threads in this forum, but unfortunately I'm still left with questions Sorry for an other - my first build thread. I got a few questionmarks and pre reqs that might be hard to fullfil making me want to create this thread before I spend my vacation budget on a CNC :)

    I apologize for a lengthy post, but will try to explain as detailed as I can.


    I live in an apartment and is lucky to have a workshop in the building, but it's a shared room so I need to have a CNC that is movable. If that is even possible and that is also my first and biggest concern. Can you relocate a CNC in a practical manor or does it need to be stationary? Thinking of keeping it square, time to set it up etc. I have a storage space maybe 15m from the workshop room so can carry or roll (design it on wheels?) it into the shop when I plan on milling.

    My primary use will be cutting Acrylic in minimum depths of 15mm, but would prefer to be able to cut fairly complex shapes in 30mm Acrylic. My secondary use will be cutting aluminum, but might leave that for a future upgrade if not covered by the initial machine recommendations.

    Thats the background, now to my thoughts and needs. I'm thinking of a small and rigid machine, based on the above mobility needs as well as the cutting materials (Acrylic and Aluminum). 500x500x250 making the C-beam very attractive. Will that work for my needs?

    I'm also found some C-beam (I think) converted machines on YouTube with Servo-engines and I'm amazed how fast and quiet they are. Particularly the Neo7CNC person.

    As I'm a hobbyist and don't plan at first to have any income of my machine I want to build my first as cheap as humanly possible and rather upgrade it when my needs grows, but I have a requirement it will work with Acrylic, pref Aluminum. My girlfriend want to cut MDF and make furniture, but that will require a 1000m+ build so that is for a future upgrade, but would like to build the first one as similar (but smaller) the a future model.

    As far as I've manage to come on my own I feel I can divide my build into 3 typical sections
    1. The construction
    2. The electronics (inc. motors)
    3. The router

    So if I start with the construction I'm so glad I found Openbuilds. The beam constructions feels just right up my alley. Flexible, smart and with so much out of the box parts to add for building it. I feel that that tick the box. But the question mark for me, as I'm such an amateur in this field is the different types of movement I need to decide.
    • Should I go for a lead screw or belt driven build? Other options?
    • Should I go a C-beam kit with movable plate or build with movable gantry and X-Y axels and construct my own build?
    • What is the pro and cons of a movable table vs not?
    Electronics feels like it's own chapter. Many DIY builds online uses Arduino with very cheap controllers making the total Electronics in 100$ range excluding motors. When I browse this site I find USB board for 250$ a pop making my wonder how much better (understand you get what you pay for) they are and if I really need that for my first build.
    Next is my thought of going Servo rather then Stepper for both torque and sound. Something I think I will need for faster Aluminium milling (correct?).
    • What is the cheapest electronic setup I should/could get to do my first build and still make it fairly upgradeable and the possibility to accurate milling in Acrylic (and potentially Aluminum)?
    • Smarter to start with Steppers and the extra controllers that require or go for a Servo engine with built in controllers from start?
    The router I guess it's as simple as if you buy a "real" spindle it becomes expensive fast, but you get more power and less noisy usage? I'm thinking a simple Bosch or Makita router to start. Will that work?

    Last I'm thinking about features as automatic zeroing and also automatic tool swap features. Is that something that is hard to create and that will require a specific option of the above 3 categories? Or just totally unnecessary for a hobbies that will mill a few times per month?


    Very happy to be here and I hope this post isn't to light for all the pro's in here. I just don't feel comfortable enough to order parts yet...
     
  2. Joe Santarsiero

    Joe Santarsiero OB addict
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    You can put you machine table on wheels. You wouldn't be the first. Just make sure it'll fit through a door if it needs too.

    30mm is easily doable.

    500mm in y on a c-beam? I don't know. Others do though.

    Servos. Pretty pricy. I think a low-end servo setup will cost you more than a really nice stepper set-up.

    The gantry type machines usally have a larger work area and are more easily upgraded for size. The moving table stationary gantry can be more rigid.

    During the build phase there is mechanical, electrical, software. Your task is to tie them all together. After the build there will be a brief learning phase dialing everything in. Be sure to take notes.

    Belt drive will cost you less to upgrade, but may give you more problems depending on how you abuse them. Lead screw isn't too expensive to replace.

    Moving table machines tend to limit the size of work. However, they can be more rigid if designed properly.

    Skip worrying about upgradeability regarding the electronics and invest in a decent setup right from the start. I'd probably forget about servos though. You may run into trouble trying to find help diagnosing any problems because steppers are the common and cost effective solution. Steppers suffice for what you're trying to accomplish.

    The DQ542MA is a great driver. You can pair it with an Arduino to control and a 48v pws and control it with the freeware available. You can upgrade this set up in a number of ways later.
    Whatever you do, please don't buy 2amp drivers and 3amp steppers.

    I won't recommend on the router. There's plenty of that around. If sound is an issue then you may want to consider a water cooled unit with vfd.

    Install limit/home switches!! They really don't cost much anyway.

    Joe
     
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  3. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    500x500 will probably take members on the order of 750mm in length so when you add steppers to the end this may hamper mobility unless you have fairly wide doors. One option would be a pivoting platform to mount the system on to where the system can be rotated vertical for transport. With a little looking around you should be able to find several variations on this concept. The only key here is that the unit must be attached to a very stiff stressed skin panel (box panel) to be sure it is always square when it is rotated up.

    As far as systems, I would recommend a fixed bed system like the Sphinx or any of the other screw drive C-beam framed stationary bed systems. And as far as Z axis depth, don't even try to build a system with more than 50mm usable depth if you intend to cut aluminum.
     
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  4. Zeuligan

    Zeuligan New
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    I now see my first misstake as when writing my measurement I was referring to the beam dimensions. Wasn't thinking of 250mm Z axis depth :)

    What about the square issue?
    Is it enough that the frame of the machine is all square or it it a factor that the entire machine always needs to be exactly perpendicular to the ground. Hmm, hope you understand what I'm asking. It's in the relation to moving the machine back and forth... If I have a squared machine and move that back and forth and place that on a table, that might not be exactly square, the machine table should still be square in relation to the rest of the parts as the build is square by definition. Or is this a faulty reasoning?
     
  5. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Having the surface absolutely level with the ground is not a requirement in any way. Many of the builders have their systems on carts that sit on slightly sloping garage floors. What is a requirement however is that the frame be attached to a platform that is structurally rigid and won't warp or twist in any way. For tilt-away type support tables this is done using a wood framework with plenty of intermediate ribs covered top and bottom with plywood that glued and screwed to create a rigid box platform.
     
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  6. Zeuligan

    Zeuligan New
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    Awesome, thank you very much sir. Now I'm on the same plane ;)
     
  7. Zeuligan

    Zeuligan New
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    Thank you very much Joel for your detailed answer. Will try to break down my followup questions
    • So with a C-beam "kit" I could mill 30mm easily?
    • Skip Servos from start, to price and brings other problems for an mature like my self (my words, not yours hehehehe)
    • Should be fine without a stationary gantry due to small dimensions and rigidness requirements (on a smaller budget)
    • Go with lead for first build
    • Don't be cheap, rather build right from start then very cheap
    • Be sure to match driver with stepper for AMPs
    Still question marks about the difference of an Arduino Uno CNC kit with power suppliers, stepper controllers etc for 70$ in total vs CNC USB controller Mk3/4 (4 axis) that cost 230$ just for that item. Confused on what I need and what I want :) Your example you mention DQ542MA and that is 40$ times 3 - 120$. That is almost twice the entire kit I mention above. I understand that it's a difference as nothing that cheap can be as good as a premium product. But it's also a difference between a Volvo and a Ferrari.
     
  8. Giarc

    Giarc Master
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    The reason the DQ542MA drivers cost twice as much is because they can actually supply the needed amperage of the larger stepper motors. The arduino kits usually come with DRV8825 or other drivers made for smaller motors like those used on a 3d printer. The DQ542MA drivers can be controlled with an arduino and good free software. The arduino is only about $20 so for $140 you have a great system This is what I use for mine, plus a 36 V power supply, and I easily mill aluminum and hard woods. I even accidentally milled iron...if you count cutting through a screw used to hold my work piece down.
     
    #8 Giarc, May 16, 2017
    Last edited: May 16, 2017
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  9. Zeuligan

    Zeuligan New
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    Thank you very much for that explanation. Made sense :)
    Found boards with built in software all controllers etc and at first glance feels pricy, but when you start to add upp computers, licenses for software, board etc. I start to understand that there is no single easy choice, just different roads to success.

    I got one last question (yeah right hehehehe) and that is to go with ball screws rather then acme. For such a small CNC I'm initially thinking of it isn't that much extra cost including all. Just the plates and fastening equipment that becomes a question mark.

    Nema 23 Torque with Ball screws and I should have a strong foundation for acrylic, aluminium and thin iron plates?
     
  10. Giarc

    Giarc Master
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    Aluminum and acrylic for sure. I have never attempted iron plates, so I can't comment on that.
     
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  11. Joe Santarsiero

    Joe Santarsiero OB addict
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    Ballscrews are great. I wouldn't get my hopes up for steel though.
     
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  12. Zeuligan

    Zeuligan New
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    Acme enough for my acrylic and aluminum needs?
     
  13. Giarc

    Giarc Master
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    Yes
     
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