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  1. #11
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    xyz
    idea

    Please comment on this idea i do like the design, but i not sure if this is going to had too much deflection so please advise?

    i have reduced the hight y gantry from 400mm to 175mm from the bottom of the z axis

    y gantry virtical and mount box section is welded steel, or welded ali

    all comments welcome
    Last edited by ciscoeuk; 01-02-2013 at 02:59 AM.
    richard armstrong

    building 8x4 cnc all rounder, 2nd build.... major headache....LOL

  2. #12
    THE FINAL DESIGN

    I THINK????? suggestions welcome please

    for x y and z

    the z axis is not final i need help hear please

    using hiwin rails and ball screw, spindle using 2.2kw water cooled, clearance to table 165-175mm

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    using nema 34 motors, but not sure i should use a high torque nema 23 on the z axis

    rack and pinion x and y

    the y axis can with take a reduction drive or should i go direct drive


    help please!


    ric
    richard armstrong

    building 8x4 cnc all rounder, 2nd build.... major headache....LOL

  3. #13
    final design

    please post your thoughts


    but i fo nee help on the z axis

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    has any one got drawings or photos of a z axis using hiwin type linear rails and blocks and ball scre set up

    or point me to the thread please

    ric

  4. #14
    D.C.'s Avatar
    Lives in Birmingham, United Kingdom. Last Activity: 05-01-2016 Has been a member for 4-5 years. Has a total post count of 326. Received thanks 30 times, giving thanks to others 24 times.
    Hello cisco, I'm not one of the resident experts but as everyone seems to have sodded off I'll give it a shot.

    Try this thread for photos and video of a z-axis

    http://www.mycncuk.com/forums/items-...ma-23-3nm.html

    You want the rails mounted to the plate that the spindle is attached to as it will add stiffness to the plate and if you are using hiwin type rails you really want to use ecocast aly for the plate as it is a lot dimensionally accurate than the cheaper stuff and hiwin rails need very accurate alignment to work properly.

    Watch the round vs square rail video here to see what I mean:

    http://www.thomsonlinear.com/website...and_guides.php

    That big hunk of material that is your gantry, is that steel box section? If you intend to mount the rails directly to it you might want to consider finding a local machine shop with a surface grinder that can grind it reasonably flat for you.

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  6. #15
    Quote Originally Posted by D.C. View Post
    H

    That big hunk of material that is your gantry, is that steel box section? If you intend to mount the rails directly to it you might want to consider finding a local machine shop with a surface grinder that can grind it reasonably flat for you.
    thanks dc

    base is steel and all the upper is 12mm ali plate and box section

    cross member is 6 x 3 ali box, is this really necessary to get the box y gantry ground, if it is then my budget has been killed

    but if you are taking about the box and plate that connects to rails, then i that's given! i will nee the plate cute to shape and the I bar making, the i bar is made from ali, but the was thinking of welding it in steal but this means get the cut on a water jet or laser?

    been working on different ideals as you can see from by thread, but seam like almost no one is willing to giving advice or the own views, i welcome anyone who can talk from experience, good or bad,

    i-beam is screwed together, but if i can find a ali wekder i will get his welded

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    Last edited by ciscoeuk; 02-02-2013 at 10:45 AM.
    richard armstrong

    building 8x4 cnc all rounder, 2nd build.... major headache....LOL

  7. #16
    Quote Originally Posted by ciscoeuk View Post
    been working on different ideals as you can see from by thread, but seam like almost no one is willing to giving advice or the own views, i welcome anyone who can talk from experience, good or bad,
    I'm happy to comment on the new design, but I haven't posted as most of the things I have to say are the same as what I said in post #7. The main problem is still that the gantry is far too tall - it's best to have no gantry sides and lower the bed, that way the gantry is supported by the main frame not some flimsy bits of plate.

    A 3Nm nema 24 motor is plenty for the Z-axis. Also, to get anything like good resolution on X and Y with rack and pinion, you'll need to have two belt reduction not one. Search on the forum for rack and pinion versus ballscrews and you'll find plenty of relevant information.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  8. #17
    Quote Originally Posted by Jonathan View Post
    I'm happy to comment on the new design, but I haven't posted as most of the things I have to say are the same as what I said in post #7. The main problem is still that the gantry is far too tall - it's best to have no gantry sides and lower the bed, that way the gantry is supported by the main frame not some flimsy bits of plate.

    A 3Nm nema 24 motor is plenty for the Z-axis. Also, to get anything like good resolution on X and Y with rack and pinion, you'll need to have two belt reduction not one. Search on the forum for rack and pinion versus ballscrews and you'll find plenty of relevant information.
    thanks for the advice
    richard armstrong

    building 8x4 cnc all rounder, 2nd build.... major headache....LOL

  9. #18
    Hi Richard,

    This design is really only suitable for Wood/plastic cutting. While it will cut aluminium the finish won't be very good and the cutting conditions regards DOC and feeds speeds will be far less than ideal.
    After our conversation and knowing your intentions to cut Ali to high finish standard then machine is all wrong. Even at half length it's all wrong.
    Again knowing your needs better then a dedicated small fixed gantry machine using profiled rails matched and ballscrews along with either high flood coolant or blown air/mist system will be far better.

    Regards this machine then I'd use supported round rail on X & Y for convenience and Budget, they will be more than good enough for just cutting wood/plastic.
    Personally I don't like R&P and would use 2010 screws on a rotating ballnut if much over 1800mm. Below this then standard connection is fine.
    That said I have used R&P in the past on large machines and it works OK but find it needs more maintenance and critical to keep free from debris. Needs much larger motors with matching drives with high ratio gearing to achieve decent resolution which together make it more costly than ballscrews with far less accuracy and efficiency.

    For the Z axis even with R&P I'd still use profiled rails and ballscrew. The Z axis is the single most important part of the machine that takes all the cutting forces directly, it also directly affects cut quality finish and if it's weak or poorly designed or uses cheap components then it will show in finish or wear and perform badly.

    The gantry design looks a little on the flimsy side regards it's sides and Box section for the gantry will be very resonant which is less than ideal and could directly affect cut quality and even motor performance if bad. If your using Aluminium box then it will need to be thick walled stuff 3 or 4mm won't be enough.
    Don't be afraid of weight when it comes to the gantry, often folks believe and go out there way to make the gantry has light as possible thinking it improves the machine when in reality it compromises the machine where it matters which is when cutting.!
    Mass helps significantly with cutting and damping resonance, light gantry only really helps regards allowing higher rapid speeds which come much lower down the pecking order of desirable requirements.

    If you want an all round machine then really this design isn't the way to go. In my experience for a successful all round moving Gantry machine then the frame/gantry needs to be different with the gantry mounted directly on the X axis bearings with no gantry sides to speak of. The distance from bed to cutter or put another way Z extension needs to kept to a minimum for harder materials like Aluminium. This requirement is often restrictive to the requirement to cut softer often bulkier materials like wood.!
    So away to accommodate both needs to be found.? You could just raise the material to the cutter for hard materials and keep the high gantry side design but this is less than ideal has the very high sides are weak area and allow flex and resonance that will show in the finish of harder materials like Aluminium. . . . Fine for wood plastics etc that need to hold less tolerance or finish.

    To do this we get rid of the the gantry sides and mount direct to bearings by raising the frame sides.
    Now we still need to accommodate the high clearance for bulky materials while still keeping the rigidity by not having the Z axis extend all the way down to the bed when cutting thinner Aluminium but at the same time we don't want to be messing around with Blocks to raise material.
    To get round this we make the bed adjustable, doing this takes away all cutting restrictions meaning you can keep maximum rigidity for all materials with much higher clearance if required.
    In real world use you will seldom move the bed and find a position that suits most of your requirements but for the times when MAX strength or large materials need to be worked on then you can and the whole machine is very configurable for ALL ROUND uses.
    All you have to remember is that it will always be a Jack of all trades and master of none but will still do a bloody good job.!

    hope this helps.

    Look around the forum for Z axis examples I've posted several examples with pictures of them in pieces and complete.
    Last edited by JAZZCNC; 02-02-2013 at 05:41 PM.

  10. #19
    thanks jazz thanks has been helpful, thanks the chat after speaking to ken (friend)

    we had decide to take your advice and build 18" x 24" unit dedicatted to metal only and encase it is a screen enclosure as this is more of a priority now all we nee now is a design

    construction will be steel and ali 3 axis unit

    as of now this thread is on hold and i will start a new one
    richard armstrong

    building 8x4 cnc all rounder, 2nd build.... major headache....LOL

  11. #20
    jazz and al


    is this what you mean by adding structure to the y gantry shoe?

    and i have lowered it 180mm to bottom of y gantry from table giving a cut of up to 125mm give or take

    end plate for structure
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    richard armstrong

    building 8x4 cnc all rounder, 2nd build.... major headache....LOL

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