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  1. #1
    So I have been interested in making a CNC machine for at least six months now hence my membership of these forums. I have been thinking of this design for the past month and have had it rolling around in my head playing with different ideas. So far this is what I have come up with.



    It's 800mm long and 600mm wide - I'm aiming for a cutting area of about 650 x 450. It's small compared to some but I want to keep it very strong so I've used 50 x 50 x 3mm box steel and have welded it together instead of aluminium and bolting. I want to use two 1600oz Nema 34 motors on the X and one on the Y for speed and accuracy. I will also use a very high power spindle to ensure my fast feed rate.

    This build log is going to go on for a long time purely because I'm a student and don't have any money so I will be doing this in dribs and drabs however I hope to have it finished just after Christmas where I can get everyone to buy me parts for it!

    The build so far...





    As you can see the welds aren't that great on the one at the back as I haven't done any welding in years and so it took a few goes to get some neat welds like the one below.



    I am hoping to finish the frame off today.

    I also need some opinions on how to do the gantry. I want to just have a peice of 100mm square box steel resting on the carriages spanning the rails but I can't really decide where I will mount the rails on the gantry like one on the side and top or both on opposite sides etc.

    Thanks
    Boscoe
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. #2
    I managed to finish the welding today I haven't got the grinder out because I don't have any ear protection currently.

    Last edited by Boscoe; 11-08-2013 at 09:42 PM.

  3. #3
    That what I like to see a man getting on with it and not talking about it. .

    Couple of suggestions.! Put some triangle plates on those upright legs to support them.!! . . . I know your thinking is he on drugs this things built like brick shit house but When machines cutting you'll be surprised just how much those legs resonate and this will transfer thru the gantry and down to the finished cut quality.

    I'd also do something on the inside to help keep the frame square, either with similar triangulation braces or plate with holes in each corner then threaded rod between to pull square.

    Because you have welded the top rail box section it means your linear rail mountings are going to have to be cock on parallel because you have no adjustment. It also means your top rail surface or plane is fixed so again if you have any discrepancy between each side it will be difficult to get out.
    If you bolted it to plates then you have a lot more freedom to shim and adjust into parallel and same plane. There are ways around this like Epoxying the top rails so they level to each other but this is more involved. Depends what you plan to do with the machine but building in adjustment helps greatly with setting up.

  4. #4
    Motors are far too powerful.
    1600 ox in on a 34 will have a hell of a load of detent torque to over come which in turn will slow the machine down.

    Very common mistake in that bigger is better.

    For the travels you are talking a 3 or 4 Nm type 23 will move far faster than the 1600 motors.
    If you want to go fast get the highest voltage drivers you can, usually 80 volts and run them at 50v AC rectified and smoothed with a big cap to get about 72 volts DC out.
    John S -

  5. #5
    Quote Originally Posted by John S View Post
    Motors are far too powerful.
    1600 ox in on a 34 will have a hell of a load of detent torque to over come which in turn will slow the machine down.
    Wow only looked at last picture and didn't read first post.!!. . . . . Bloody hell massive OTT like John says. At this size 3Nm on 10mm pitch screws with 70Volts and it will fly.
    When you say you want to cut fast, what exactly do you want to cut.? The material and tool used is often the limiting factor regards speed and most machines will travel far faster than the material or tooling will allow.
    Just having a high powered spindle isn't always enough and what exactly do you call high powered.?

    From the fact you where going to use 1600Oz shows me a few things.?
    1: You've been on the American sites too much. . .Lol and . . . 2: You haven't done enough research in this area.

    I suggest you post your intentions and desires then we can help save you from buying the wrong components.
    Like John says It's common mistake regards motors but it will have a big affect on performance, same goes with ball-screws, bigger is not always better. So post what your thinking to use and we can help steer you in right direction and suggest you don't buy a thing without asking unless your absolutely sure it's correct for your needs.

  6. #6
    Clive S's Avatar
    Lives in Marple Stockport, United Kingdom. Last Activity: 35 Minutes Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 9-10 years. Has a total post count of 3,333. Received thanks 618 times, giving thanks to others 78 times. Made a monetary donation to the upkeep of the community. Is a beta tester for Machinists Network features.
    Quote Originally Posted by JAZZCNC View Post
    There are ways around this like Epoxying the top rails so they level to each other but this is more involved..
    I sort of made a similar frame and used epoxy like others have done on here like this:-

    Click image for larger version. 

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    The bridges from one rail to the other is to allow the epoxy to self level.
    The Epoxy is Wests System 205/109 very slow setting hardener ..Clive

  7. The Following 2 Users Say Thank You to Clive S For This Useful Post:


  8. #7
    Quote Originally Posted by Clive S View Post
    I sort of made a similar frame and used epoxy like others have done on here like this:-

    The bridges from one rail to the other is to allow the epoxy to self level.
    The Epoxy is Wests System 205/109 very slow setting hardener ..Clive
    Now I wonder who gave you that idea Clive.? . . . Lol . . . . Looking good.

  9. #8
    Agreed with the 1600oz-in motors - they'd be excessive and might even perform worse than Nema 24 motors.

    Quote Originally Posted by JAZZCNC View Post
    Now I wonder who gave you that idea Clive.? . . . Lol . . . . Looking good.
    Me
    Last edited by Jonathan; 12-08-2013 at 06:27 PM.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  10. #9
    Thanks for the replies guys. I'm thinking of getting frame professional fabricated because although this one is pretty good and accurate I want something getting on for perfect!

    Quote Originally Posted by Jonathan View Post
    Agreed with the 1600oz-in motors - they'd be excessive and might even perform worse than Nema 24 motors.



    Me
    The motor thing is interesting, I thought they would be better especially if I used some high power drivers and high voltage rail.

  11. #10
    Quote Originally Posted by Boscoe View Post
    The motor thing is interesting, I thought they would be better especially if I used some high power drivers and high voltage rail.
    It depends, see here:

    http://www.mycncuk.com/forums/faqs-p...do-i-need.html
    Last edited by Jonathan; 12-08-2013 at 07:27 PM. Reason: formatting
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

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