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  1. #11
    Thanks! Got it on the frame. Makes absolute sense! :) I was already designing some jigs in my head to keep weld distortion under control. Now I can probably ditch those.

    But with the Y. I basically just copied some designs I found here and there and I don't really have any more ideas. :(

  2. #12
    Quote Originally Posted by mart154 View Post
    I was already designing some jigs in my head to keep weld distortion under control. Now I can probably ditch those.
    Jigs to stop distortion are not practical really.? Heat cause's distortion and stress so to restrain these forces would need massively strong Jigs which for a one time machine just isn't worth the trouble. If you stitch weld in short runs and spread welding around so not to create heat build, Take your time and don't try to weld frame in one go let it rest and come back to it then you won't have much trouble.

    Tips to help with stress relieving are Stitch weld and balance the welds IE: If you weld for half inch on outside face of steel box then immediately weld half inch on inside face opposite to keep balanced stress's. Don't weld all of one side up then turn over and do other, Also Don't weld in one spot for long but Move around and try to weld with minimum heat.

    Quote Originally Posted by mart154 View Post
    But with the Y. I basically just copied some designs I found here and there and I don't really have any more ideas. :(
    I'd just move the rails on Gantry closer towards front and just have narrowest top and bottom brackets possible you won't need any thing more than that and they will be more than strong enough. Edit: When I say narrow I mean looking from side not narrow bearing spacing.!!

    I noticed your Z axis plates look on the thin side what thickness did you have in mind.? For the front and rear Z axis plates I wouldn't go less than 15mm and 20mm is best balance of strength and cost.
    Last edited by JAZZCNC; 17-09-2013 at 03:37 PM.

  3. #13
    I make my living with welding and have big strong (200ton tested) jigs I could use and know how to hold weld distortion to minimum :)
    But still I like your idea for the bed more. The massive amount of steel I designed there was in a hope that I could maybe use 15mm ali bed and stop excessive movements with the frame underneath.

    So with the Y you basically suggest a structure shaped like a PFC?

    Z axis plates? You mean the plate where the spindle and Z axis rails mount to? It is intended to be 20mm. At least in my head, have to check the drawing tho :)

  4. #14
    Quote Originally Posted by mart154 View Post
    I make my living with welding and have big strong (200ton tested) jigs I could use and know how to hold weld distortion to minimum :)
    Well your sorted then and you'll understand why I said what I did thinking your DIY welder with minimal resources.

    Quote Originally Posted by mart154 View Post
    But still I like your idea for the bed more. The massive amount of steel I designed there was in a hope that I could maybe use 15mm ali bed and stop excessive movements with the frame underneath.
    Yep it would have been but personally I'd only buy enough to cover the cutting area has Ali plates expensive and even with ali plate you'll want the edges supported. My steel Bed frame is larger than yours with less supports than you first drew and with 16mm ali bed and I don't have any probs with movement. Unless your throwing engine blocks on it then there's very little forces acting in a downward direction while cutting and you really want to limit plunge cutting to a minimum for spindle and machines sake has it knocks shit out of them.!!

    Quote Originally Posted by mart154 View Post
    So with the Y you basically suggest a structure shaped like a PFC?
    Yep just like a PFC ( Parallel Flange channel for those wondering.!!)
    Last edited by JAZZCNC; 17-09-2013 at 06:31 PM. Reason: Spell checker screwing me.!!

  5. #15
    Ok, I updated the drawing a bit.

    Did the "PFC mod", tho, now I have to fit the Y ballscrew somehow between the gantry and Z I suppose, so this is still going to change a bit.

    Redesigned the bed a bit also. Didn't save any steel tho :)
    Decided to have the extra steelwork under the bed just in case. Who knows, maybe I'll mill myself an engine block :)

    Now the bits that could introduce side distortion are in one piece and there's a box everywhere under the edge of cutting area.

    Left the green 30x30 bits in place. If I decide to have the bed only as big as the cutting area, these will help to mount "cutting fluid collection / mess containment solution"

    I plan to cover the sides (and the edges then) with plywood or mdf or 1mm mild steel or something similar.

    Click image for larger version. 

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    Now, couple other questions have risen as well.
    First, on this picture below theres a 15x60mm riser plate under the gantry. I was wondering if it might be worth extending it and put the X ball screw mount straight to it instead of the gantry endplate?
    Click image for larger version. 

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    Secondly. At the moment my Z rails are spaced 75mm apart, is this going to be enough or should I widen it?


    I must thank anyone yet again for feedback. And for this forum in general! Amazing source of information!

  6. #16
    Quote Originally Posted by mart154 View Post
    Now, couple other questions have risen as well.
    First, on this picture below theres a 15x60mm riser plate under the gantry. I was wondering if it might be worth extending it and put the X ball screw mount straight to it instead of the gantry endplate?
    Swings and roundabouts really, both will work. The extended version will possibly make fastening and alignment easier.
    Take some time to think about ballscrew alignment because little adjustments can make a big difference to performance and it doesn't take much to go from working fine to stalling motors, esp at higher speeds. So anything you do to make alignment easier you'll be thankful for when setting up.


    Quote Originally Posted by mart154 View Post
    Secondly. At the moment my Z rails are spaced 75mm apart, is this going to be enough or should I widen it?
    Not 100% sure what your meaning with the apart bit.? Do you mean 75mm between bearings in vertical direction or 75mm between bottom bearings and top bearings.?

    Anyway here's my take and way of doing it. The Z axis width or space between rails and bearings doesn't matter so long has you can fit everything like ballscrew between them. So you can make it just the minimum width if you like.!! . . . . What far more important is the bearing spacing on the Y axis and the more(within reason) you have the better it will be, obviously this comes at the cost of cutting width so it's a balancing act and personally I won't go any less than 200mm with 300mm being better. I tend to make my Z axis width 180mm or minimum 160mm.
    I only ever really use profiled rails/bearings if can help it and these are much stronger so can get away with 200mm but if using round type rail I'd be looking for more.

    I've also noticed you have the X axis bearing spacing very close together.? Same applys here has well but not quite the same with you running twin drive but I'd still try and get the widest foot print you can afford, even if it means extending the top rails past the ends slightly.!

  7. #17
    Ive tried to design most of the precision critical components with oval holes and left provisions for shims here and there.

    Here's a picture of the new "PFC" to explain the "apart bit."
    Click image for larger version. 

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    Tho I just realized that the number "75" should be actually 100. So many errors. Embarrassing....

    So I gather that would be fine?

    For bearing spacing on X and Y I do agree, tried to save some cash there but I'll increase it from 150 to 250.

    Or would it be any good if I leave the bottom bearings on the gantry with 150 (or 200) spacing and do the top one say 300? (just to get the cutting area that little bit bigger?

  8. #18
    Quote Originally Posted by JAZZCNC View Post
    profiled rails/bearings

    I just realized that profiled rails might actually be in my price range. Have to think and choose.


    I wander if 15mm might be too small?

    Have to do some more research :)
    Oh damn you! :)

  9. #19
    Quote Originally Posted by mart154 View Post
    Here's a picture of the new "PFC" to explain the "apart bit."

    Tho I just realized that the number "75" should be actually 100. So many errors. Embarrassing....

    So I gather that would be fine?
    Apart from it looks like there's not enough room for the ballnut.? . . . Have you accounted for it.?

    Quote Originally Posted by mart154 View Post
    Or would it be any good if I leave the bottom bearings on the gantry with 150 (or 200) spacing and do the top one say 300? (just to get the cutting area that little bit bigger?
    Yes I'd have the top wide because you can and it will help and have the bottom most you can spare.

    Quote Originally Posted by mart154 View Post
    I just realized that profiled rails might actually be in my price range. Have to think and choose.
    Well if they are within reach then stretch to them because they are in another league to round rail. 15mm will easily handle the loads but the bearings are not always ideal due to there smaller size but they will easily do the job.

  10. #20

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