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  1. #11
    Quote Originally Posted by Clive S View Post
    Wal according to his first post he intends to weld them to the supports so not using conventional rails. ..Clive
    That's right :) They will be supported at intervals. That's because they are integrated in the design. There is no efficient way to plasma cut full support profiles. Or you would need to cut the profile from lets say 20mm steel and stack all the supports next to each other, but that's just too much of a pain and would lead to alignment inaccuracy.

    Supporting them at intervals won't cause binding of the 20mm plain stainless steel shaft, considering that the interval length stays reasonable. Current interval is 220mm on Y axis and 240mm on Z axis.
    Last edited by eurikain; 20-08-2015 at 01:46 PM.

  2. #12
    Wal's Avatar
    Lives in Stockport, United Kingdom. Last Activity: 3 Days Ago Has been a member for 5-6 years. Has a total post count of 318. Received thanks 29 times, giving thanks to others 13 times.
    >That's right :) They will be supported at intervals.

    Ah, okay. You'll need to keep a close eye on those creeping bearing housings then, if one of those housing edges were to catch on a support it could spell trouble, although you'll probably hear them knocking/scraping before it does. Bear in mind that the machine could be working on a small part of a project, going back and forth many times over (with the bearing housing silently creeping out of place but not having to pass a support strut...) before moving on to a different part of a table... If it's crept enough to catch on a support strut... Disaster.

    You might want to 'arrest' the housings so that they don't rotate past a certain point, ie. with a blob of epoxy - I don't mean for you to glue 'em in... Just a blob or two on the outside of the housings that stops them rotating past a certain point... [I should probably do the same with mine...]

    Wal.
    Last edited by Wal; 20-08-2015 at 03:16 PM.

  3. #13
    Wal's Avatar
    Lives in Stockport, United Kingdom. Last Activity: 3 Days Ago Has been a member for 5-6 years. Has a total post count of 318. Received thanks 29 times, giving thanks to others 13 times.
    Wait - weld...? Weld the supports to the rails...? Surely you'll be asking those rails to bend...?!

  4. #14
    I've just jumped into this thread and I would think twice about welding the rails. They will almost certainly bend out of alignment with the heat and shrinkage, even I suspect with TIG which can be more delicate.

    It may also remove the hardening from the local area although that will probably be the least of your problems.

    Don't want to knock your ideas but I would seriously check whether this is a good strategy - so buy a very small length of rail, put a bearing on it with a cheap laser pointer aimed a a wall. Mark the spot, then weld the rail to a something to replicate the support post and see what happens to the spot. Then decide if this approach is going to work before spending money on all the laser cutting . . .

    To be honest, supported round rail would be a much better option and it is easy to bolt down via the flanges.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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  6. #15
    Wal's Avatar
    Lives in Stockport, United Kingdom. Last Activity: 3 Days Ago Has been a member for 5-6 years. Has a total post count of 318. Received thanks 29 times, giving thanks to others 13 times.
    >To be honest, supported round rail would be a much better option and it is easy to bolt down via the flanges.

    +1 - Even if you insisted on not using the supports that the rails comes with, you can unbolt them and use the pre-drilled/tapped holes in the rail to attach your own supports...

  7. #16
    Thanks for the replies ! It's nice to see the support !

    You are right, welding the rails will cause bending. What about brazing ?

    Pass the next paragraph if you're not interested in my totally subjective opinion and prefer getting to the more relevant part of my post :D

    Now, here is the problem I have with the fully supported rails: I have looked into that option for quite a while, but nobody at AliExpress will accept to ship 2000mm round supported rails to me... I asked already, they shipped the SFU2010 2000mm lengths without any problem, but won't take the risk of sending those rails over 1500mm. Now that's only one side of the problem... the other one is that shipping cost is just a waste of money... there is no real added value to those rails except the fact that they're round stainless steel rails mounted on stainless steel supports. Now this is just my opinion, and I know that using them would be the best option, but I just feel really bad spending $300 on shipping on a $100 rail, that's just not enough cost effective for me and not in the philosophy of this machine :(

    Even if you insisted on not using the supports that the rails comes with, you can unbolt them and use the pre-drilled/tapped holes in the rail to attach your own supports...
    Now that's a winner :) But, I can get those wholes drilled and tapped in a 20mm stainless steel shaft, here in Belgium, with $0 shipping cost. I could include that into my design as well ! Do you have a picture of a supported round rail where shaft and support are separated ?

  8. #17
    Something fresh and new!

    Your calculated weight numbers seems to be very low! 10mm and 15mm steel is heavy stuff...

    My experience with laser and plasma cutting tells me that positional accuracy is always good but edge is never 90 degrees. Plasma is worse than laser. It also gets worse with thicker materials. Most certainly you will have to use straightening tools since sheets are not flat. But good rubber hammer will get it fixed :D
    You have to somehow make the openings for M10 nut pressfitted otherwise the nuts will fall out. That especially when you assemble the gantry...or you have another solution for it?

    As for the rails...somehow I have a feeling that you will end up with HIWIN stuff.

  9. #18
    Please dont go with the round rails !

    it will ruin what is looking like a nice design

    thats all i have to say :S

  10. #19
    Wal's Avatar
    Lives in Stockport, United Kingdom. Last Activity: 3 Days Ago Has been a member for 5-6 years. Has a total post count of 318. Received thanks 29 times, giving thanks to others 13 times.
    Quote Originally Posted by eurikain View Post
    Do you have a picture of a supported round rail where shaft and support are separated ?
    I don't, I'm afraid, but here's a link to some data etc. for my TBRs:

    http://www.zappautomation.co.uk/mech...aund-rail.html

    IIRC even though the holes were spaced equally, there was no control over how far the first/last bolts fell from the ends of the rail - it didn't matter as I didn't need to separate the shaft from its support and I had full control over where I was putting my own mounting holes in the supporting base. I imagine it matters a bit more for you, but you could always buy over-length and then cut down so that the holes fall where you need 'em to...

    >As for the rails...somehow I have a feeling that you will end up with HIWIN stuff.

    Yes yes! (...and I like my round rails, but profile is the way to go..!)

    Wal.
    Last edited by Wal; 20-08-2015 at 10:13 PM.

  11. #20
    On the rail lengths problem I know you can butt individual profile rails together to make longer rails but not seen it done on supported rails. I wonder if you cut off a piece of the supporting extrusion you get with supported rails (say 200mm) and use it to bolt 2 shorter rails together ie a joining piece. Because the support is continuous and has a shallow radius on the top which the round rails sits in it should help align the rails to each other. You could then order 2x 1m rails . Not tried it but something to think about.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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