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  1. #31
    Quote Originally Posted by JAZZCNC View Post
    Ok obviously miss understanding but either way flimsy or strong it's fact the rails would help support.!
    Of course, but if it's helping significantly you're probably doing something wrong.

    Quote Originally Posted by JAZZCNC View Post
    First let me say dont be fooled by the lack of post's, I've been building diy cnc machines both for my self and others for meny years so I know very well all the newbie mistakes and pitfalls I just havent posted on here.
    I've read plenty of your posts on CNCzone. Well, I'm pretty sure it's you. It is obvious from the few posts that you have made here that you know what you're talking about! I have not posted on CNCzone since 5 years ago as I figured I would never have time to do any machining if I did it too much.

    Quote Originally Posted by JAZZCNC View Post
    Regards the down side and your thinking you have to move the steppers with the front plate. It makes no differnce rails on rear or front both you can still have the motor static with the right design. Your right thou the difference is negliable.
    Fair enough, me not thinking...

    Quote Originally Posted by JAZZCNC View Post
    When using Profiled linear rails it's important you have a datum referance edge but not for helping stopping them move when crashed, the main importantance is for the alignment when installing.
    Agreed, the more important factor is to attain good alignment of the rails. It also explains why the sides of the bearing blocks are ground. The reason I said about stopping movement after a collision is that I remembered reading it here, page 13 where it mentions that 'it is possible that the rails and the blocks will be displaced when the machine is subjected to vibrations and impacts':

    http://www.hiwin.nl/DownloadCenter/f...9TE14-1006.pdf

    Quote Originally Posted by JAZZCNC View Post
    Then you tighten the opposing or what I call floating rail or bearing losely then slowly move the gantry or table along the rail nipping the bearing or rail as you go along feeling for any tight spots and losening adjusting the floating rail or bearing to eliminate tight spots
    That's what I did and subsequently checked it with a dial indicator.

    I won't pretend to be any sort of expert on profile rails - I've only just researched them and bought mine. I still may get some for my X-axis (2000mm rails). I gather you know of a good source?
    Last edited by Jonathan; 30-08-2011 at 09:40 PM.

  2. Jonathan and CNCJAZZ,

    Thanks you have given me a huge amount of insight into improvements for the gantry section on the rebuild and also on the new build (once the funds are in for that). I am having to replace the end bearings on the one I have and am looking at either getting replacements for now (to have the mill running and to get work done) or get the bearings that I am looking at getting for the rebuild. Think will go with a getting what will let me produce product and then buy the others as I build. Need to be able to make money to build better (more precise) machine.

    Michael.

  3. #33
    Quote Originally Posted by Jonathan View Post

    Agreed, the more important factor is to attain good alignment of the rails. It also explains why the sides of the bearing blocks are ground.
    Also Jonathan If you look carefully the rails are ground or have ref edge not just the blocks. . . Very easy to miss.!

  4. #34
    Here ya go Lads. . . I knew I had some pics of a Z axis I'd made (really should take more pics of stuff made!!) that used linear rails on front plate with stationery motor, Also with pockets for bearings to give datum ref and slightly recovers some lost stick-off.!

    It also inverts the stepper and drops it down the backside out the way connecting to screw with belts and pulleys. The number 1 looking bit in the pics is for a drop down bracket that attach's to the y axis screw.

    Also a pic showing the Yaxis stepper again inverted in on it's self, reason being this machine was designed for small spaces or sheds so wanted to minimise foot print and eliminate any sticking out bits, The X axis does the same with everything under the bed out the way. . . Nothing protudes past the frame foot print.



    In the pic showing rails n bearings they are just lent against the backplate for the pic, the bearings actually go to the bottom of the back plate. They also need cutting to length. . . . . ( Jonathan those are 20mm SBC bearings n rail.)
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  5. Okay,

    Now you really got me thinking of ways to not only improve what I have but make the new one even better. Also with the two carriage stacked like that on the Z I would assume that you need to increase the length of plate to allow the travel I want to attain. Which might not be a problem. Though would only one set of carriages on each side for the current rebuild be enough with only 150 -175mm of travel.

    Hope to get some drawings done tonight and trying to figure out a space issue with the required space for the Z leadscrew and backlash nut/mounting bracket versus the height that the rails and carriage require to function. Looks like I will be needing to mill some stock down with not only datum slots but also with channel to allow space for the screw. I have access to 12mm Alli' for sure and might have access to thicker. Having said that would milling the 12mm down to a 6mm channel in the centre reduce strength below the desired levels? I am still learning metal and it tolerances and what it can and can not do. Which is different then what i do with metal for making reeds in many fashions as there you want the metal to bend.

    Michael

  6. #36
    Hi Micheal,

    First depends what you intend to do with the machine regards the plate thickness. I've made various differant Z axis but only one that was made with thin plate. This had a long 220mm travel and was mainly intended to cut soft materials like foam,plastics etc. It was made with with cast off's and scrounged parts that the owner and me between us gatherd (Hence thin plate was used).
    It's not ideal for cutting hard materials but the guy does cut every thing from foam to Ali with it. . . It's a belt driven machine as well, very quick and accurate.!! . . I love this little machine "The Cavemill" was so much fun to make and resonably cheap being made mainly from scrounged bits. Attached a few pics of the Z axis and some stuff it's cut.

    I love making "Junk yard dog's" I'm just finishing off another I'll post a pic of.

    Personaly I dont like to use anything below 19mm for a Z axis that is intended to cut hardwoods or Ali. If your using profiled rail and intend to cut datum points and slots for screw etc then you really do need the 19mm else your weakening the structure. Again depends on intended use but for hardwoods and Ali using Profiled rail then 19mm is minimum IMO.
    Also I wouldn't recommend using 1 carraige per side no matter what thickness material, it's false economy because it will flex badly and you'll end up making it over again.! . . Esp at the travels your wanting.
    Imo the Z axis is one if not "THE" most important parts on the machine, remember doesn't matter how strong you build the rest of the machine if the Z aixs flexs you'll have BAD results.!! . . . It's also one area everybody new under estimates.

    Regards travel most of my Z axis tend to be between 120-150mm the one in the previous pics had 150mm if I remember correctly.??

    Attached a few pics of Zaxis made all ways. All built depending on machine and material requirements. Hope these will help you design something to full fill your needs.

    Cheers.

    PS: The upstands on the junkyard pics are temps just for affect to give idea too intended owner and have since been made lot shorter.

    Edit: Added Cavemill pics of stuff cut.
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    Last edited by JAZZCNC; 05-09-2011 at 11:45 AM.

  7. Folks been buried in work.

    Still chugging along but clients come first. Really need to get the rebuild on the first machine done though and if possible the second built as already have product that will need the length in it and have clients that want to buy. Why, oh, why do i get myself into these positions. Wish me luck and have the new drawings and hopefully more useful information up soon . Also mc_cnc I will try to drop you a line to see how to catch up with you.

    have a good night folks need sleep.

    Michael

  8. #38
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 3 Hours Ago Has been a member for 9-10 years. Has a total post count of 1,833. Received thanks 192 times, giving thanks to others 5 times.
    I know all about those positions, but right now the brain is shutting down!
    All I know is I woke up at 7am on saturday on the west coast of Canada, and I'm now sat at home having had about 2 hours sleep on the plane.

  9. Okay,

    Here is tha much promised and hard to get around to drawing of v2. You will notice that it is not complete. I am still working away at it but would like some input. Will let you know any other problems might be having in the near future. Due to problems (flex of Y axis and Z axis dropping up to 1.5mm from a set position) this rebuild has to be done like yesterday and been working on it the last three days non-stop. This is what has made far enough to be label a version and put before you folks for opinion and evaluation.Click image for larger version. 

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    Any and all opinions would be greatly appreciated as will be burningthe candle in to the long hours. Need this done to get product back up to stocking levels for a convention at the end of October. Yes thing s do go wrong at just the wrong time. Yes I know I need to increase the rail for Z to get 150mm.

    Anyone wanting a DWG, STP, IGES file of this or the completed gantry router let me know.

    Michael

  10. #40
    id think about putting both Y axis rails top and bottom or you are going to lose valuable space...

    the way you have them now will have your spindle over hanging further than it needs to buy quite a long way

    try to keep your spindle as far back as possible... every little bit will help, it may not alter the flex by much but im pretty sure that each little fraction of stiffness you save will reduce sympathetic resonance or vibration by a sh*t load

    good luck

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