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  1. #1
    I am wanting to buy/build a cnc router, primarily for wood working (birch ply) but with the option to machine small non ferrous metallic components infrequently.

    A specific job I have for the cnc router will be to machine audio horns – see attached picture. Click image for larger version. 

Name:	iwatahorn.jpg 
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ID:	18230 I will profile layers and glue them together. The maximum size I will be making is around 700 mm x 500 mm. I don’t expect to 3D machine them but to 2 ½ D machine them with 1-2mm steps, which will be sanded post assembly.

    I have been looking at a number of posts on this website and others and estimate that a cnc machine is going to be £1500 plus just for the parts. I have no real desire to build the machine, so I had been looking at commercially marketed machines too.

    What is the general opinion about Chinese steel framed machines in the £3K sector, as I feel that this is the level I would want to compare too? Buying may be cheaper as a couple of hundred quid can be lost with a few errors. I am also time poor currently.

    I have little NC experience – last time I was involved it was on punch tape! I am a professional design/stress engineer with a varied past, from designing complicated handling delivery systems to designing large fabrications for the aero industry. No machine/fixture design experience unfortunately.

    If I am to build, ( deep down the engineer in me wants too) I feel comfortable with the mechanical side of designing the gantry and rails – after following a number of the build threads on this site, I am starting to understand the pro’s and cons of different arrangements.

    I think I have decided on a few things.

    Machine Size - obviously it would be nice to be able to nest and machine a full 8 x 4 sheet. I cannot fit it in my workshop, and for the once a year job – I could not justify it. To build the largest wooden horn I will ever get asked for a 900mm x 600mm bed will be adequate. In the z axis I was going to stick with around 150mm, anymore than this and the work piece will vibrate, never mind the machine.

    For the X Y & Z slideways, I was thinking profiled rails. 20mm Hiwin or similar.

    I just have a concern with accumulating dust/debris on the rails – are the wiper seals on the carriages – that good? (The answer to this will decide on whether I mount the rails on the top of the frame – or protected down on the side)
    I have been looking into how to purchase the Hiwin rails and carriages economically – I see you can get the carriages from BST in china for a good price – but its not really economic to ship the rails. Is there any reason why I could not have the carriages shipped and purchase the rails in the UK? (Different standards/specs etc)

    It also seems to be cheaper to buy single longer rails. I was also thinking I would get a couple of longer rails and cut them into my 3 lengths – I assume they can be cut with a disc?

    The frame I was going to use aluminium profile sectioning – having used it for a couple of “work” jobs it seems to allow a robust construction without the need for a full fab/machine shop. (Obviously if I had a 2 metre bed machining centre I would fabricate and have the rail pads machined – post fabrication). I am hoping if necessary I could fill the profile rails with sand (concrete maybe) to damp out vibrations – reduce cutter chatter.

    I was thinking of using 80mm x 160mm profile for the Y carriage. With similar for the x axis support structure ( twin x axis ball screws).

    I am waiting on some info back from a friend who is a HGV coach builder– to see what aluminium sections he can get me for free.

    What I don’t have a clue about is the electronics and what is current and is best for this application and what is OTT. From reading threads on this forum, it seems like this bit I sort out after I have finished the mechanical side, I would like an idea of the cost of a “good” 4 motor & controller system.

    Sorry for the epic first post……


  2. #2
    In short- take the calc and you will see that ball screws, machining, Hiwin rails, carriages, spindle and VFD bought altogether from BST will save you a lot, even if shipping is costly. have been there, done that
    project 1 , 2, ...

  3. #3
    Hi Steve
    Welcome to the forum
    Have a look @ this

  4. The Following User Says Thank You to mekanik For This Useful Post:

  5. #4
    Sorry about the multifont post - looked okay on the ipad - but wrong on the PC.

    Well thanks for the link to the bellows - that can definitely mitigate the risk of dust/chipping on the bearings.

    Regarding buying everthing from BST - i have been expoilting some of the free postage offers they have had for the ball screws so almost have all of those, seem reasonable quality ( can only come to some SKF ones i used a few years back). I haven't been that lucky so far with import duty - and think that i will be financially worse off importing the rails from china. So back to my original question is there any reason why i cannot buy the rails and carriages seperately, my worry would be getting the carriages onto the rails if they are a very tight fit - i assume that a chamfer could be machined onto an end -to ease fitting.

  6. #5
    I don't have a lot of luck with imports either but a lot of chinese sellers are using european distribution warehouses which then negates the problem for the buyer and still works out a lot cheaper than buying from UK suppliers.

  7. #6
    Keep us updated regarding the rails and price, i have been collecting bits and bobs and have 20mm HIWIN carriages but on AliExpress most of the sellers seem to sell rail with two carriages. missed a couple of 1Meter rails that were on sale from a forum member.

  8. #7
    I have been looking at a number of posts on this website and others and estimate that a cnc machine is going to be £1500 plus just for the parts. I have no real desire to build the machine, so I had been looking at commercially marketed machines too.
    Welcome to the forum Steve. I would be careful of buying any stuff until you have a design sorted out as that is one of the biggest mistakes people make as the plan will evolve and change over time. Also don't buy any electronic kits and they are never matched or correct.

    There are one or two people on the forum that do build bespoke machines and usually to much higher quality than you can get for the same money. Good luck with whichever way you decide to go.

  9. #8
    Clive, Thanks for the words of wisdom. I was only going to purchase the rails and the ball screws. Which will be the same for what design style I chose.

  10. #9
    Can somebody give me a link/picture to some examples of the build quality of these "bespoke" machines, to give me an idea of what my potential diy effort will be up against.

  11. #10
    I like this one
    Dean(JAZZCNC) had input on this one so can't go wrong if you follow his lead.
    Last edited by mekanik; 21-04-2016 at 07:45 PM.

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