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  1. #1
    G'day Everyone!

    My name is Richard and I live in Melbourne Australia. I have very much enjoyed reading the various threads on building DIY machines and probably like many on this forum have found and very much enjoyed the learning curve in getting to understand the issues and parameters in building a CNC machine. Unlike many on this site, I have limited experience in building machines, but I am quite a handy person and accustomed to getting my hands dirty on DIY projects. I am waiting for delivery of my TIG / Stick Welder, so my practical learning curve will start with improving my welding skills. Meanwhile I've been on a steep learning curve getting familiar with Rhino as a CAD drawing package (also to be used in designing Kinetic Artwork).

    I have created this thread hoping that those more experienced will be able to guide me on my build. So here goes....

    1. My Machine Parameters

    I plan to build a CNC Router, with the flexibility to use it for Plasma or Laser cutting of steel. It is intended to be a general purpose machine with a high degree of accuracy (if I'm going to the trouble of building something bespoke, then it may as well be accurate).

    The main material I will be cutting is timber (plywood up to 25mm thick) and some aluminium (aluminum) to create Kinetic Artwork (wall art etc).

    It will initially be a three axis machine, but I intend to build in capability to expand to a 4th axis to turn table legs, carving etc. If I honest with myself, I suggest that the challenge (and resultant satisfaction and no doubt accompanying frustration) of the build outweigh practical applications.

    The general parameters of the machine are:

    1.1 Working Area

    X Axis - 1.5m
    Y Axis - 1.25m
    Z Axis - capable of 220mm travel, but anticipated generally working to 154mm
    4th Axis Capability - Removable working platform to accommodate greater Z depth of 350mm (total) for an additional axis

    As the machine will be residing in my garage, I need to make is as compact as possible (car parking will likely be a casualty!).

    1.2 Router /Laser/ Plasma Capability

    I intend to install a 2.2kW water cooled router as the main cutter.

    I have designed a holding water tank and support to be able to cut steel. I understand that compromises are made to do this, however as it is as general purpose machine, speed etc. are very much a secondary consideration. I'm not sure where my Kinetic artwork will take me, so flexibility needs to be built in.

    1.3 Frame / materials

    I intend to build the majority of the frame from 89 mm SHS, 3.5mm thick.

    The Gantry will be manufactured from Steel RHS (150 x 200 mm) reinforced with 10mm Steel plate to sit on the carriages for the X Axis.

    I attach a spreadsheet showing the calculated weights expected to be carried by the X, Y & Z axis, which:

    X = 112kg
    Y = 27kg
    Z = 19kg

    For obvious reasons I wish to ensure that the removable Steel/MDF platform is robust to ensure accuracy. I have read threads where some members suggest simply building a removable MDF platform to vary the Z depth. Given the depth of the Z axis and flexibility to do some Plasma/ laser cutting, I have swayed away from this, but equally, I am conscious of the additional Steel / weight / work my design requires. Thoughts on alternative variable Z axis designs welcome! My requirement is to ensure accuracy prevails (no movement).

    1.4 Motors/Drive

    Having read in detail a number of threads relating to similar designs, I have landed on a design which utilises:

    Ballscrews - still to calculate / determine whether I need 20mm diameter or can get away with 16mm when considering lengths of:

    Y Axis - 1,694mm
    Z Axis - 1,762mm

    Z Axis Actuator - I will probably look to purchase one for the Z axis, believing that something 2nd hand may be more accurate than anything I will build.

    Guides - Looking at LM guides for greater accuracy from the likes of THK or suitable alternatives.

    1.5 Drive Mechanism

    All Axis (perhaps with exception of Z Axis depending on Actuator used) to be powered by belt drives to reduce vibration and provide flexibility in changing gearing ratios if need be. Initially, I intend gearing to be a 1:1 ratio, but final calculations may dispel this notion.

    I intend utilising stepper motors for their greater torque range, and wish to explore the use of an encoder function to provide a closed loop system reducing errors if steps are somehow missed.

    Based on earlier research, I expect that I will be utilising something like NEMA 23 motors with outputs around 3 to 4 kN (424 to 566 oz/in) outputs.

    I have purposefully held off on this hoping for some feedback on my draft design of the frame (gantry) suggestions on shaft diameters, etc., before calculating final requirements.

    I am not sure what cutting speeds I should design to (and hence input for motor requirements). Speed is not essential as I will not be into major production runs, but neither do I wish to watch a job completed at a snails pace. Any input on appropriate / realistic tool speeds for cutting MDF (25mm) or aluminium (aluminum plate say typically 20mm) which I should aim would be much appreciated.

    Plasma or laser speeds could presumably be much faster??, but router work should drive the design.

    2. Drawings and Spreadsheet

    For reference I attach various views and closeups of my draft drawings and spreadsheet showing materials and weights.

    I am not totally sure how some components for drives/ LM / ballscrew Nut anchors should be attached, apart from the general understanding that everything needs to be adjustable to tweak tolerances (I/m sure my soon new found welding skills will challenge the need for this!). Thoughts / photos on how items should be bolted together or how I should alter my design to provide for this would greatly assist.

    3. Your input

    I now lay myself prostrate, seeking input from members who have the skills and experience in building such machines on matters raised or any other items which my design raises.

    Please note that I have a thick Aussie hide and welcome your constructive feedback! My first objective is to order steel to build the frame, but also understand that I should have ordered and received guides, shafts etc, before starting cutting to ensure concept and practical application marry up!



    PS The site wont let me upload images. Will post once sorted.
    Last edited by Tinkerer; 29-09-2014 at 10:55 PM.

  2. #2
    Sounds like you've done a good research job, I think 20mm ball screws may be in order and if you use good digital drivers for the stepper motors then speed should be achievable.
    There's not much to say until the pictures are up.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  3. #3
    Thanks Eddy. I have very much enjoyed reading and learning from your contributions to this site. For some reason I cannot load dwg files, so have reverted to pdf format. Attached are images and Excel spreadsheet of materials:

    Materials and Mass 20140930.xls

    I look forward to your and other's feedback.
    Attached Thumbnails Attached Thumbnails Right View.pdf   Top View.pdf   Perspective View.pdf   Gantry Right View.pdf   Front View X Axis and Gantry close up.pdf  

  4. #4
    Some additional views with shelf removed and with shelf/Plasma tank:

    Attached Thumbnails Attached Thumbnails Perspective View Shelf removed.pdf   Perspective View with platform and Plasma.pdf  

  5. #5
    G'Day Richard,
    Looks to me like you've done a cracking job researching, planning, and drawing your ideas!
    I reckon this forum's experts are the best in giving advice for DIY-CNC so welcome aboard.
    Cheers, Andy
    PS. Whereabouts-ish are you in this urban spread called Melbourne? I'm down Berwick way.

  6. #6
    I have been asked to upload JPEG files. Here they are (slightly different perspectives but from same drawing). If someone can advise what the preferred file format for graphic uploads is, then I will stick with that going forward.

    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Front View.jpg 
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ID:	13501   Click image for larger version. 

Name:	Gantry Close Up.jpg 
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ID:	13502   Click image for larger version. 

Name:	Perspective View with Plasma.jpg 
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ID:	13503   Click image for larger version. 

Name:	Perspective View.jpg 
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ID:	13504   Click image for larger version. 

Name:	Rigth View.jpg 
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Name:	Top View.jpg 
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ID:	13506   Click image for larger version. 

Name:	X and Y Axis Close Up.jpg 
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ID:	13507  

  7. Jpg or gif or png all work and display in the web page. Pdf is good for downloadable documents but doesn't display in the page.

  8. The Following User Says Thank You to irving2008 For This Useful Post:

  9. #8

    IMO you should reconsider some main points:

    1. Z axis travel, bed depth ,4rth axis, gantry

    -Z 200mm is ok and going more will lead to another problems, which would need reinforcement, that would l lead to more weight and that to servo motors.
    I am doing a similar build so 200mm is ok for all, even for plasma, as i intend to do also.

    -that singular gantry beam contradicts with the 200mm Z travel. 2 beams, say 100x100x4mm welded together will be better. Vibration wise.

    -that removable bed you have drawn is mistake. Either make it proper removable bed like some designs here make it, not with angles but bolted directly side of the beams, or calculate the correct bed depth for 200mm axis and make it fixed. For a fixed bed, depending on design you need more or less 300mm from gantry beam when all mounted.

    -4rth axis is no problem with say 300mm deep bed/from gantry beam/. The most ridgid 4rth axis worth for that type of machine, could be made from mini lathe, as i intend to, and it enters in 300mm bed from gantry, or you could make the axis inside the bed if you intend to spin things bigger than 300mm OD

    2. Z
    you should concentrate on the Z, draw it strong in all directions and all will start from there. Rails on the moving plate, and so on. Then the gantry, then the gantry sides...

    3. Now that you have all this clear, you should decide how to move it. If you decide on servos, go back and make it as much strong as its reasonable.

    4. Check if in real life the ball screw on the long axis will allow to be mounted like this. Will it pass once all welded.

    5. As far as i read 4 inch deep plasma water bed is ok, so that will be removable, no need to be bolted onto anything.

    Once you have it clear which way you would go, especially the motors, everything will speed up.

  10. #9
    One consideration I fell fowl of was that I was also constrained on space, so as I order plywood for a project now I need it cut at supply. If I were doing it again and could have made the space I'd have gone for a design that could take a standard 8x4 sheet of wood straight from supply.

  11. #10
    Hi Tony, thanks for the feedback. I have grappled with the same issue, but I believe I can source plywood at the smaller lengths here (or get the saw out!). Even if this were not possible, the space availability is an issue, so I will err on the small side for now...perhaps for the next build!

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