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  1. #11
    Sounds good to me.
    I'll go watch the videos on the rail comparisons.

    re:welding, my only concern is steel is very difficult to weld and maintain high tolerances, for instance creating a right angle between two pieces of steel, after you have prepped and clamped into position, then welded and cooled down, you might end up with 88 degrees instead of 90, most things that doesnt matter, but if you then wanted a true 90 deg out of it you'd have to machine faces.

    I think that is why Ali extrusions are desirable as they are made to high tolerance and obviously adjustable to square up.

    Maybe there are welded CNC machines on here, I'll take a look out of interest. But unless there are huge advantages I'd be prefer to bolt together, and maybe weld the odd bracket if needed.

  2. #12
    Cad models aren't so bad, you can download dxf's from KJN aluminium if using aluminium profile, Hiwin cad models are available from their website make sure you get the right model (It's the carriages you have to watch mostly) I never cad the ballscrews out I just did the maths using the datasheets but you could cad them if needed the thread is irrelevant. I certainly never picked up a pair of verneirs during my build lol

    The information you need on the ballscrews are on the datasheets for BK12/BF12 and dsg16 if using 16mm ballscrews.

    Further to what clive said about 15mm being harder to mount you need spacers see below.

    Click image for larger version. 

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    also greasing 15mm rails is also a PITA.

    If you have trouble finding cad models grabcad is good but I always grab the models directly from manufacturer or reseller if I can as accuracy is important.

    Lots of people makes their frames from welded steel box section and then use epoxy resin to level the box section where you fit the linear slides. Steel is a lot cheaper than aluminium extrusion, it's also popular to mix steel everything with an aluminium extrusion gantry which is my plan for my next build.

    There's 600+ in aluminium and fittings in my router if I'd paid retail for it and I have 120cm * 70cm travel. You could certainly do something in steel a lot cheaper than that and of course it's stronger.


    Accuracy with a steel a frame is nowhere as important as you think depending on how you fit the hiwin's the most important thing is they are level and parallel to each other. I'm going to weld mine together myself but have the steel cut by someone else (Who will be super accurate and square) to make things easier then you need a level working space and so decent magnetic clamps should be fine.

    This is a quick mockup I did in fusion 360 for my next router, see how I'm planning to mix steel with extrusion. The cost of those 2 pieces of 9090 extrusion is 240 alone! My design is a nightmare because I want the Hiwin's sideways on so the frame does have to be very accurate and epoxy levelling for the Hiwin's will be difficult as I'll have to turn the router 90 to level each side. Mount the Hiwin's on top and you can don't need the frame to nearly as accurate.

    Click image for larger version. 

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    That's not a ballscrew it's a cylinder I extruded with BK fitting's I downloaded the important bit is the DSG ballnut housing as this is your mounting point.

    Prices add up quickly I've spent over 80 just on T nuts to fit the Hiwin's to the extrusion and M4, M5, M6, M8 & M12 bolts. If you use corners it becomes even more expensive.
    Last edited by Desertboy; 02-01-2018 at 04:33 AM.
    http://www.mycncuk.com/threads/10880...60cm-work-area My first CNC build WIP 120cm*80cm

    If you didn't buy it from China the company you bought it from did ;)

  3. #13
    Ah ha,,,,,welding now it makes sense.

    I see now, yes for sure if your including a frame there would be alot of welding, and I see that shimming out the rails with epoxy etc will give you the alignment accuracy where needed.

    Lot of interesting points in your post, I'll digest that some more later.

    Out of interest why are you choosing to mount the rails on the side rather than on top? is there an advantage or is it to do with working width?

    Also to reduce materials; at a cursory glance if you wanted side mount rails I wonder if you would gain strength and reduce flexing movements by putting those rails on the inside of the frame?
    (Though no doubt you'd probably lose some working width).

  4. #14
    Also to reduce materials; at a cursory glance if you wanted side mount rails I wonder if you would gain strength and reduce flexing movements by putting those rails on the inside of the frame?
    (Though no doubt you'd probably lose some working width).
    If you go the steel route mount the rails on the top as it is much easier, the way the epoxy works is that you make a moat on the two rails with a bridge between them this way the epoxy will flow around and give you the flat plane you require.

    You use the very slow curing epoxy made by Wests 205 - 109 fluid for about 8 hours.

    Search of the forum for epoxy levelling Click image for larger version. 

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    ..Clive
    The more you know, The better you know, How little you know

  5. The Following User Says Thank You to Clive S For This Useful Post:


  6. #15
    Thanks Clive

    I would have thought there are other benefits to mounting the rails on top too, like the slider bearing are being worn either side rather than all the weight and action being applied to topside...................Although it is probably negligible over time anyway.

    I like the Frame, neat job, is it 75mm box section your using or is that 100mm? ( I was trying to guess from the clamps and mdf).

    Epoxy, I haven't specifically looked yet but I did see some where making Epoxy square pads, but what you have done there is much better, less chance of the epoxy shattering with long strips like that too as opposed to isolated squares.

    I got a load of Epoxy here...and I guess besides a slow cure pre warming will make it like water to get the level, in fact you can get laminating epoxy which is quite thin and you buy the slow activator...(I repair boats occasionally). I buy from East Coast Fibreglass supplies, and CFS fibreglass suppliers.

    How are you sealing the MDF mould to stop the Epoxy running out underneath? have you stuck it down with a grab adhesive or some sealant?

    I make grp moulds occasionally and I use modelling clay (the GRP suppliers sell it) to make fillets around edge. you never see square edges with GRP parts, always rounded,,and it is done with modelling clay and a wooden spatula,,,or finger to make smooth radius. (Though in the case of what you have done there it wouldn't be applicable because the radius would create a lip in the epoxy down the edge). Anyhow just thought I'd pass that on as the clay is handy for various temporary shaping and sealing once you have used it for that kind of thing.

    Some polyurethane glue like gorilla glue, or even an expanding foam gun would make a good seal too,and be easy to peel off afterwards.

  7. #16
    My frame is made out of 60x60x5 box, what is not shown is the table bed as that is adjustable in that it can be moved to different positions but in reality I have never moved it.Click image for larger version. 

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    I sealed it with decorators caulk the epoxy is 5mm thick it came from East Coast Fibreglass. You have to be very careful with the sealing. It was left for about 8 days before removing the mdf
    ..Clive
    The more you know, The better you know, How little you know

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


  9. #17
    Looks Grand!

    I got CNC envyittus already.

    I did notice in the last photo, the bolt holes for adjusting the bed height.

    Those side plates look Beefy, I can just make out you have them rebated into the bottom plate, is there a fillet weld along sides too I think I can make one out in the photo, or is just bolted?

  10. #18
    Quote Originally Posted by Clive S View Post
    My frame is made out of 60x60x5 box, what is not shown is the table bed as that is adjustable in that it can be moved to different positions but in reality I have never moved it.Click image for larger version. 

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    I sealed it with decorators caulk the epoxy is 5mm thick it came from East Coast Fibreglass. You have to be very careful with the sealing. It was left for about 8 days before removing the mdf
    That's a damned nice machine there
    http://www.mycncuk.com/threads/10880...60cm-work-area My first CNC build WIP 120cm*80cm

    If you didn't buy it from China the company you bought it from did ;)

  11. #19
    Quote Originally Posted by Heliox View Post
    Looks Grand!

    I got CNC envyittus already.

    I did notice in the last photo, the bolt holes for adjusting the bed height.

    Those side plates look Beefy, I can just make out you have them rebated into the bottom plate, is there a fillet weld along sides too I think I can make one out in the photo, or is just bolted?
    The bed sits on angle that is bolt through the holes if you bolt the bed directly to the frame you would pull the sides in.
    But as I said its never been moved.
    ..Clive
    The more you know, The better you know, How little you know

  12. #20
    Quote Originally Posted by Clive S View Post
    The bed sits on angle that is bolt through the holes if you bolt the bed directly to the frame you would pull the sides in.
    But as I said its never been moved.
    Sorry Clive, my question was about the polished Aluminium side plates on the Gantry being rebated into their bottom plates, is it bolted and welded or just bolted?

    (I just carried on from talking about the adjustable bed and should have worded it better).

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